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International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
1
Photoluminescence Properties of White Light Emitting Kbapo4:Dy3+ Phosphor
1Govind B. Nair and
1S. J. Dhoble*
1Department of Physics, R.T.M. Nagpur University, Nagpur, India- 440033, INDIA.
*Corresponding author email ID: [email protected]
ABSTRACT:
KBaPO4:xDy3+ (x= 0.005, 0.01, 0.02, 0.03) phosphors were effectively synthesized by sol-gel
method. The photoluminescence spectra exhibited an increasing behaviour in the emission intensity
with an increasing dopant concentration with optimum intensity at x = 0.03 moles and no
luminescence quenching was observed till this concentration. For the emission wavelength 576 nm,
the phosphor showed excitation peaks at 326 nm, 350 nm, 365 nm, 388 nm, and 426 nm. Highest
emission intensities were observed for an excitation wavelength of 350 nm. The emission
wavelengths showed two sharp peaks with their wavelengths centered at 484 nm (blue) and 576 nm
(yellow) corresponding to 4F9/2 → 6H15/2 transitions and 4F9/2→ 6H13/2 transitions respectively.
Keywords: Phosphor, phosphate, White light emission, Dy3+
INTRODUCTION
ABPO4 phosphors have made a huge impact in the field of luminescence with their versatile
properties [1–4]. Phosphate phosphors are known specially for their role as excellent host matrix
offering good luminescence efficiency, strong absorption in the VUV region, high chemical and
thermal stability, moderate phonon energy, exceptional optical damage threshold and low sintering
temperature [5]. As a result, phosphates are preferred over sulphides, sulphates, fluorides, nitrides,
etc. as host matrix to luminescence materials.
Rare earth doped phosphors are primarily sought for their ability to produce visible light
emission under UV or near-UV excitation. A number of rare earth doped phosphors are being
studied for their application in solid state lighting. It is possible to obtain white light from a single
component phosphor by using the principle of energy transfer from the sensitizer to the activator,
which has been introduced into a crystalline host matrix. White light can also be obtained by
adjusting the yellow to blue intensity ratio obtained by doping the host matrix with Dy3+ ion, as it
has two intense emission bands in the blue (470–500 nm) and yellow region (560–600 nm). In this
work, KBaPO4:Dy3+ phosphors have been synthesized by so-gel method and their
photoluminescence properties have been analyzed.
EXPERIMENTAL
KBa1-xPO4:xDy3+ (x = 0.0005, 0.01, 0.02 and 0.03) phosphors were synthesized by sol-
gel method. The starting materials were NaNO3, Ba(NO3)2, NH6PO4, Dy2O3, Polyethylene
Glycol (PEG, molecular weight = 1500) and Citric acid. Dy2O3 was dissolved in conc. HNO3
under heating and stirring, and a clear solution of Dy(NO3)3 was attained. All the four solutions
NaNO3, Ba(NO3)2 and NH6PO4 dissolved in deionized distilled water were added one by one in a
glass beaker and kept for stirring at a constant rate. 0.1 M solution of PEG and citric acid solution
were added to the above solution (molar ratio of Metal ions : Citric acid : PEG = 1:0.5:0.5). The
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
2
solution was kept stirring and heating at 80 oC until the gelation takes place. The gel was dried in an
oven at 100 oC and the gel burnt into dry dark brownish precursor. This was then transferred into
porcelain crucibles and then heated in a muffle furnace at 600 oC for 6 hours. The resultant white
phosphor powder samples were then characterized for their photoluminescence properties. The as-
prepared phosphors were characterized by Shimadzu RF-5301PC Spectrofluorophotometer with a
slit width of 1.5 nm.
RESULTS AND DISCUSSION
Fig. 1 shows the PL excitation spectra of KBaPO4:Dy3+ phosphors monitored at 576 nm.
The sharp excitation peaks from 300 nm to 450 nm can be attributed to the intra-4f forbidden
transitions from the ground state 6H15/2 to higher energy levels of Dy3+. The peaks located at 326
nm, 350 nm, 365 nm, 388 nm, and 426 nm can be attributed to the transition from 6H15/2 to
4M17/2, 6P7/2, 6P5/2, 4P7/2 and 4G11/2, respectively. Optimum intensity was observed at 350 nm
indicating their potential to be used in UV LEDs.
Fig. 2 shoes the emission spectra of KBaPO4:xDy3+ (x= 0.005, 0.01, 0.02, 0.03) phosphors
at 350 nm excitation wavelength. The emission spectra displays similar trend for all the emission
lines and two dominating peaks at 484 nm and 576 nm, corresponding to 4F9/2 → 6H15/2 and
4F9/2 → 6H13/2 transition, respectively. It can be seen from the spectra that the blue emission is
stronger than the yellow emission, indicating that Dy3+ are located in centrosymmetrical site in
KBaPO4 [6]. It is observed that the emission intensities increase with Dy3+ concentration and reach
the optimum value at x = 0.03. No concentration quenching phenomenon was observed upto 3
mol% doping of Dy3+ ions in KBaPO4 phosphors.
Fig. 1: PL Excitation spectrum of KBaPO4:Dy3+ phosphor.
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
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Fig. 2: PL emission spectra of KBaPO4:Dy3+ phosphor.
CONCLUSIONS
A series of novel bluish-white light emitting KBaPO4:Dy3+ phosphors were synthesized by
the sol-gel method. Under the excitation of 350 nm, the phosphor gave two intense emission bands
centered at 484 nm and 576 nm corresponding to 4F9/2 → 6H15/2 and 4F9/2 → 6H13/2
respectively. Optimum concentration of Dy3+ for KBaPO4:Dy3+ phosphor was observed at x=0.03.
KBaPO4:Dy3+ phosphor can be confirmed as potential candidate for white light emitting diodes.
ACKNOWLEDGMENTS
One of the authors [GBN] acknowledges the Department of Science and Technology
(DST), New Delhi, INDIA for financial assistance under INSPIRE Fellowship programme with
registration number IF150675.
REFERENCES
[1]C.C. Lin, Z.R. Xiao, G.Y. Guo, T.S. Chan, R.S. Liu, Versatile phosphate phosphors ABPO4 in
white light-emitting diodes: Collocated characteristic analysis and theoretical calculations, J. Am.
Chem. Soc. 132 (2010) 3020–3028.
[2]H. FANG, S. HUANG, X. WEI, C. DUAN, M. YIN, Y. CHEN, Synthesis and luminescence
properties of KCaPO4:Eu2+,Tb3+,Mn2+ for white-light-emitting diodes (WLED), J. Rare Earths.
33 (2015) 825–829.
[3]L. Guan, C. Liu, X. Li, G. Jia, Q. Guo, Z. Yang, et al., Synthesis and optical properties of
KCaPO4:Eu2+ phosphor, Mater. Res. Bull. 46 (2011) 1496–1499.
[4]G.B. Nair, P.D. Bhoyar, S.J. Dhoble, Exploration of electron – vibrational interaction in the 5d
states of Eu2+ ions in ABaPO4 ( a = Li , Na , K and Rb ) phosphors, Luminescence. in press (2016)
doi.10.1002/bio.3143.
[5]G.B. Nair, S.J. Dhoble, Highly enterprising calcium zirconium phosphate [CaZr4(PO4)6 :Dy3+ ,
Ce3+ ] phosphor for white light emission, RSC Adv. 5 (2015) 49235–49247.
[6]S.-A. Yan, Y.-S. Chang, W.-S. Hwang, Y.-H. Chang, Enhancement of luminescence properties
via the substitution of Ba2+ by Sr2+ and Ca2+ in the white phosphors
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
4
Single Crystal Growth and Dielectric Properties Of Gallium(Iii) Doped KDP By
Shankarnarayan- Ramasamy Method
N. S. Meshram, V.R. Raghorte@
,B. A. Shingade#,
*, N. M. Gahane , K. G. Rewatkar, V. M. Nanoti***
Department of Physics, Dr. Ambedkar College, Deekshabhoomi, Nagpur-10 India
@ Department of Physics, Model Arts and Science College, Karanja-33, India
# Department of Physics, Bhavbhuti Mahavidyalaya, Amgaon . 10India
***Department of applied Physics, Priyadarshani College of Engineering, Nagpur-10
Email :[email protected]
ABSTRACT
Potassium Dihydrogen Phosphate (KDP) is newly developed ideal nonlinear optical crystal used
for high-energy laser technology and optical electronic devices. Gallium ion doped KPD single
crystal grown by Shankarnarayan -Ramasamy method. Good and transparent qualities of crystals
have been harvested with dimension 11x10x13 cm .The crystal structure and perfection has been
determined using powder XRD and High resolution XRD. Presence of Gallium was confirmed by
EDAX in the crystals. Functional groups were present in the crystal by FTIR. Thermal properties of
the crystal have been studied by using Thermogravimetric (TGA) and Differtial thermal analysis
(DTA). Optical transparency has been studied by UV-VIS spectrum. Dielectric properties were
studied with varying frequency at different temperature.
Keyword: - single crystal growth, KDP, Powder XRD, FTIR, TGA-DTA, Dielectric ,EDA
INTRODUCTION
KH2PO4 (KDP) and KD2PO4 (DKDP) crystals are currently the only nonlinear materials
suitable for frequency converters and Pockels cells in high-power large-aperture laser systems.
These crystals often suffer from laser damage, which adversely affects the quality of the
downstream beam. The observed damage thresholds of KDP/DKDP crystals are much lower than
the intrinsic thresholds, due to the nano-scale impurities, which are difficult to identify due to their
sizes. Laser-induced bulk damage resistance of KDP/DKDP crystals strongly depends on the laser
wavelength. The laser damage threshold at 1064nm is much higher than that at 355 nm.[1]
Trivalent impurities like Fe 3+,
Cr 3+
, Al3+
have effect growth rate of the crystal. Due to there
comparable ionic size with potassium ion and probably substituted trivalent impurities. Ga 3+ ion is
optically active material and no study has been made to investigate the effect of Ga(III) ion on
growth and optical properties of KDP crystal. Present work is based on effect of trivalent on
growth and dielectric properties of crystal. SR method is most suitable method for unidirectional
growth with 100% solute conversion efficiency [2].
SHAKARNARAYAN RAMASAMY METHOD FOR SINGLE CRYSTAL GROWTH
S-R method is the unidirectional crystal growth method by slow evaporation of solution.
Seed crystals were prepared by convectional recrystallization slow evaporation method. KDP of
Merck AR grade was used to prepared seed crystal. Very good and transparent qualities of seed
crystals were selected having perfect external morphology. <100> crystal plane was selected for
unidirectional growth in S-R method. Seed crystal was cut carefully and polished portion along
<100> plane. The processed seed crystal has been placed at the bottom of ampule, which is special
designed for S-R method[3,4]. Solution was prepared at 30 oC according to solubility curve. 27.8
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
5
gm/ 100 of KDP solute Merck AR grade has been dissolved in (Millipore 18.2 M Ohm cm
resistance) triple filter deionized water. Solution was kept three hours on magnetic stirrer at 30 oC
temperature for homogeneity in the solution. Solution was kept slightly under saturated for S-R
method. Clean filtered solution was carefully filled in ampoule without disturbing the position of
seed crystal inside the ampoule. The ampule has been rested in S-R set up for two hour. Initially,
temperatures are kept 30 oC at upper and lower ring heater. The solution has been settled inside the
ampule and concentration gradient maintain along the ampule. Concentration gradient was
maintained minimum at top and maximum at the bottom of the ampoule. Upper ring heater
temperature slightly was increased 35 oC for rising evaporation rate at top of the ampoule. The top
ring heater controls the spurious nucleation near the surface region of the solution during crystal
growth process. Upper part of ampule has been covered with transparency sheet and the small hole
at the center is reduced nucleation at upper part of ampule.
A transparent KDP crystal growth has been observed at the bottom of ampule under
optimizing condition in week. The KDP growth rate is approximately 1 mm per day was observed.
A good transparent quality of crystal was harvested. KDP Crystal growth has been carried out for
different doping concentration in S-R method [5].
Fig1. SR set up for growth crystal Fig 2 Grown KDP crystals by SR method
CHARACTERIZATION
Good quality and transparent KDP crystals were ground in pestle mortar to determine
different characterization. Some KDP crystals were cut in dimension 10mm x 10mm square area
for optical transmission studies.
1. Powder XRD and single crystal XRD analysis
Fig 3 powder XRD of KDP crystal
The crystalline phase characterization of the samples is carried out by a computer interfaced
X-ray Diffractometer (Philips, Xpert - MPD) operating at 40 kV and 30 mA with CuKα radiation
where =1.54056 Å. It is observed that the powder XRD diffracted peaks are same in the pure and
doped KDP crystal. The prominent peak of pure and doped KDP (101), (200), (112), (202), (310),
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
6
(312) are observed. The sharp peak indicated that the crystalline natures of grown crystal are fine
quality. The XRD data matched with the JCPDF data file no 035-0807 and result shows that gallium
has entered into the KDP lattice. It shows that the crystal structure of KDP remains same by doping
gallium [6].
2. FTIR spectral analysis
An FTIR spectrum of pure and doped KDP crystal has been recorded on VARIAN resolution pro
FTIR spectrometer in the range 400- 6000 cm -1 by KBR pallet technique.
Fig 4 FTIR of KDP crystal
The assignments confirm the presence of various functional groups present in the material. The
wave number 3065,3334 cm -1is presence of O-H bond, 2919,2839,2461 cm-1 presence of P-O-H
bonding, 2358 cm -1 represent P-O=H bond, 1295,1100 cm -1 presence of P=O bond, 904 and 543
cm -1 is represent of P-O-H bond [7,8].
3. EDAX studies
Fig 5 EDAX of Gallium doped KDP crystal
Energy dispersive X-ray analysis (EDAX) used in conjunction with all types of electron
microscope has become an important tool for characterizing the elements present in the crystals[8].
In the present research module study, INCA 200 energy dispersive X-ray micro analyzer equipped
with LEO – Steroscan 440 Scanning electron Microscope, analyzed the crystal. The recorded
EDAX spectrum is shown in figure 6. Presence of Gallium is confirmed from the EDAX spectrum
[9,10].
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
7
4. TGA -DTA Studies
0 100 200 300 400 500 600 700 800 900
-18
-16
-14
-12
-10
-8
-6
-4
-2
0
2
4
82
84
86
88
90
92
94
96
98
100
340.36oc
318.18oc
275.52oc
Hea
t Flo
w E
ndo
Dow
n (m
W)
218.61oc
DTA
TGA
Wei
ght %
(%)
Temperature oc
Fig TGA- DTA Gallium doped KDP Crystal DTA and TGA of KDP were carried out with the help of an instrument (STA 409C) using
KDP crystals as sample and alumina as reference [11]. As shown in figure 7, KDP doped sample
were decomposed at 320.3 . The graphs show the peaks at 261.6 , 213.5 , 261.6 reveal
exothermic reaction due to escape of oxygen atoms from the KDP crystal. As shown in figure ,
TGA curve sharply decrease at temperature at 230 and 356 is most probable melting point
of KDP crystal TGA curve shows that crystals are thermally stable below 230 [12,13]
5. Dielectric studies
KDP has dielectric nature was measured by Wynne Kerr 6500B (UK) impedance analyzer.
At low frequency, it was observed that the dielectric constant increases with increase temperature.
Also, it is observed that the dielectric loss reduces with increase in doing concentration. At high
frequency the dielectric constant decreases to large extent. This peculiar behavior appears because
of dopant Ga+3 ions in the crystal lattice [14].
Fig 7 Dielectric constant vs. log frequency Fig 8 Dielectric constant vs. Temperature
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
8
RESULT AND DISCUSSION
Pure and Trivalent Ga3+ ion added KDP crystals were grown by Shankarnarayan -
Ramasamy method. The XRD spectrum shows the excellent crystalline nature of Gallium added
KDP crystal. All functional groups were present in crystals and are confirmed by FTIR spectrum.
Ga3+ ions are adsorbed on the crystal faces and create isolated centers. The presence of
Gallium was confirmed by EDAX analysis. DTA, TGA analysis reveals that KDP is stable up to
240.36 before it melts. Gallium ion enhances the conductivity in crystal and Dielectric constant.
Dielectric constant is decreases with increase in frequency as temperature increases.
ACKNOWLEDGEMENT
Author N. S. Meshram and Dr. K. G. Rewatkar Acknowledge UGC for their financial support under
major research project
REFERENCE
[1]S. B. Monaco, L. E. Devis, S. P.Velsko, F. T.Wang, D. Eimerl, and A. Zalkin, J. Cryst. Growth
85, 252–25 (1987).
[2]N. P. Rajesh, V. Kannan, P. SanthanaRaghavan, P. Ramasamy, and C. W. Lan, “Nucleation
studies and crystal growth of (NH4)H2PO4 doped with thiourea in supersaturated aqueous
solutions,” Materials Chemistry and Physics, vol. 76, no. 2, pp. 181–186, (2002).
[3].N.P. Rajesh, V. Kannan, M. Ashok, K. Sivaji, P. SanthanaRagavan, P. Ramasamy,
[4].N. Balamurugan, P. Ramasamy, Cryst. Growth Design 6 1642(2006).
[5].Christer B. Aakeroy, Peter B. Hitchcock, J. Mater. Chem. 3 (11) 1129) (1993.6
[6].G.T. Moldazhanova, Crystallogr. Rep. 39 135(1994).
[7].A.A. Chernov, in: A.V. Shubnikov, N.N. Sheftal (Eds.), Growth of Crystals, vol. 3, Consultants
Bureau, New York, p. 35(1962).
[8].C. N. Banwell and E. M. McCash, Fundamentals of Molecular Spectroscopy, McGraw-Hill,
New York, NY, USA, 4th edition, (1994).
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
9
Super-Paramagnetic Iron Oxide Nanoparticles for Hyperthermia Applications
N. N Sarkar* K.G Rewatkar1 V.M Nanoti
2 C.S.Prakash
3
*Department of Physics Dr. Ambedkar College Deeksha Bhoomi Nagpur 440010 1 Department of physics Dr. Ambedkar college Deeksha Bhoomi Nagpur-10
2Department of Applied Physics P I E T Hingna Nagpur 3Department of Applied Physics SJCI T Chickballapur Bengaluru
*Corresponding author, [email protected]
ABSTRACT
Today most of the Researchers are attracted on Super Paramagnetic Iron Oxide Nanoparticle
(SPION) material due to their novel application and unique magnetic properties and their uses in
nanotechnology. SPION with a spinel structure form a large group of materials with a broad range
of applications. When the ferrite materials exhibited superparamagnetic behavior then it can be
applicable for biological purposes like drug delivery, hyperthermia and MRI Therefore, the
superparamagnetism is a characteristic strongly desired for spinel ferrites. Since this phenomenon is
size-dependent, the methodologies to synthesize these materials have emerged as a crucial step in
order to obtain the desired properties. In this regarding, several synthetic processes have been
developed. For example, Auto combustion, co-precipitation is a fast and cheap method to synthesize
superparamagnetic spinel ferrites.
Keywords: spinel ferrite, SPION , hyperthermia, drug delivery, synthesis methods, etc.
INTRODUCTION
Metal oxide nanoparticles are the important class of materials as their optical, magnetic and
electrical properties find a wide range of high tech applications [1]. Fe3O4 nanoparticles are
common ferrite with an inverse cubic spinal structure. These class of compounds exhibit unique
electrical and magnetic properties due to the transfer of electrons between Fe2+ and Fe3+ on
octahedral sites [2]. Fe3O4 nanoparticles have been the subject of intense interest because of their
potential applications in several advance technological areas due to their promising physical and
chemical properties. Generally, these properties depend on the size and structure of particles [3,4].
Fe3O4 nanoparticles find wide applications in the field of biomedical, as anticancer agent [5,6],
corrosion protective Pigments in paints and coatings [7]. The magnetic atoms or ions in such solid
materials are arranged in a periodic lattice and their magnetic moments collectively interact through
molecular exchange fields, which give rise to a long-range magnetic ordering. Among all iron oxide
nanoparticles, Fe3O4 represent the most interesting properties due to of its unique structure i.e. the
presence of iron cations in two valence states, Fe2+, Fe3+ on tetrahedral and octahedral site with an
inverse cubic Spinel structure. The coercivity and remenance values for the super paramagnetic
nano Fe3O4. nanoparticles have been found to be zero by the earlier reported methods[8]. Presently,
cell labeling strategies find application of superparamagnetic ferrite either through conjugating the
magnetic nanoparticles to the cellular surface of the stem cell or by internalization of the particles
into the cell. Superparamagnetic ferrite can work in both of these ways, since the potential to
manipulate their surface chemistry is plentiful and their sizes along with other attributes promote
their successful uptake into cells. The superparamagnetic nano ferrites also interface well with MRI
technology. The use of superparamagnetic particles play a crucial role In the diagnostic imaging
modality technique finds application in the study of stem cell [9].
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
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SUPERPARAMAGNETISM
Soft ferrites are characterized by a small value of coercivity, so they cause low hysteresis
loss at high frequency. They are widely used in electromagnetic cores of transformers, switching
circuits in computers and radio-frequency (RF) inductors, e.g. lithium ferrite, nickel ferrite and
manganese–zinc ferrite. A typical hysteresis loop of a soft magnetic material a high magnetizing
force is encountered, a point is reached where further increase in, H, does not cause useful increase
in, B. This point is known as the saturation point of that material. The saturation flux density, Bs,
and the required magnetizing force, Hs, to saturate the core.( fig1)
Fig 1 A typical hysteresis loop of a magnetic material
Spinel Ferrite
Spinel ferrites are a huge group of materials with the same structure of the natural spinel
MgAl2O4. According to the literature [10], over 140 oxides and 80 sulphides were already
synthesized and their physicochemical properties studied. This large variety of spinels is due to their
capacity to incorporate cations with different charges into the structure. However, the total positive
charge should not be higher than 8 to balance to the charge of the anions. Another requirement is
about the cation radii. The values must be in the range of 0.4-0.9Å.Magnetic spinels usually have
the general formula of M2+Fe2O4 (or MO.Fe2O3), where the divalent cation can be Mn, Ni, Fe,
Co, Zn, Mg, etc. The most important and abundant is the natural Fe3O4 (or FeO.Fe2O3) [11]. The
crystalline structure of spinel ferrites was firstly determined by Bragg [12] In1915. In the spinel
structure, the metallic ions are coordinated to oxygen with two different ways, which generate two
coordination sites. The first one is called A site and the cation is coordinated in tetrahedral
symmetry. The second one, namely B sites, is coordinated in octahedral symmetry as shown in
figure 2
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
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Fig 2. Spinal structure
Hyperthermia
Hyperthermia is the cure harnessing the nature that a cancer tissue has less heat-resistant
than normal one. In the hyperthermia, it is important that the cancer tissue is selectively heated
without damaging the normal tissue. The interstitial hyperthermia using magnetic material is known
as Magnetic Induction Hyperthermia [13,14], Soft Heating [15] or Implant Heating System (IHS)
[16] is an excellent system to perform the purpose. In the system, the ferromagnetic material
(implant) is implanted in the cancer tissue at first,and it is heated by utilizing the eddy current or the
magnetic hysteresis loss under the high frequency alternating magnetic field (HFMF). Then, the
temperature of the cancer tissue is raised and regulated at a Curie temperature Tc of the implant
material. We previously reported on the mechanism of heat generation by the eddy current [17],
which depends on the magnetic field, the frequency of HFMF, the permeability, the resistivity and
the size of the implant. Moreover, in order to gain the maximum heat generation, it is necessary that
the direction of HFMF is parallel to the long axis of the implant. Fe–Pt alloy needles [18], which
were developed based on this concept, were used for treatments of brain tumors [19] and oral
malignant tumors [20]. On the other hand, the hysteresis loss is hardly dependent of the direction of
HFMF and of the size of the implant. Therefore, the materials heated by the magnetic hysteresis loss
can also be used for hyperthermia in a fine powdered form.
LITERATURE REVIEW
Won li Choiet al.(2012) [21] was studied the effect of mechanical properties of iron oxide
nanoparticle loaded functional nano-carrier on tumor targeting and imaging, and they conclude that
the mechanical properties of chitosan-functionalized, Pluronic based nano-carrier were
systematically varied by loading different amounts of IONPs, but still keeping the same size, shape,
surface charge, and release profile of the loaded IONP. Overall, very good tumor targeting and
accumulation of IONP were achieved by using the functional nano-carrier, thus, this could serve as
an enhanced MRI contrast agent. P.A. Desai et al.(2011) [22] were studied on Silver doped
lanthanum chromites by microwave combustion method and found that LaCrO3 and silver doped
lanthanum chromite nanoparticles have been synthesized by microwave combustion route. Pure
phase products are obtained at microwave power of 0.56 kW, irradiation time of 10 min and fuel to
oxidizer ratio of 1. Average size of LaCrO3 particles is 57 nm, while the silver doped samples have
a finer particle size of 7–8 and 20–26, respectively, for A site and B site doping. Increase in
coercivity and saturation magnetization values of doped samples is attributed to non magnetic
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
12
nature of silver. Hasan Mukhtar et al.(2013) [23] also studied on Nanoformulation of natural
products for prevention and therapy of prostate cancer and they conclude that the use of naturally
occurring products, such as dietary nontoxic phytochemicals, has emerged as one important
approach to fight this disease, which may be appropriated for high-risk patients, especially those
with isolated HG-PIN, elevated PSA, and negative biopsy. Silvio Dutz et al.(2009) [24] were
studied on Ferrofluids of magnetic multicore nanoparticles for biomedical applications and they
found that the peak position from XRD data was used to distinguish between the magnetic phases
maghemite and magnetite. The diffractogram show a relatively broad single peak between the
theoretical angles for maghemite and magnetite. This means that the resulting particles presumably
consist of solid solutions of both phases (one resulting peak).
However, it is also possible that particles consist of a mix of maghemite and magnetite
particles (two separated peaks). In principle, a differentiation between these both cases is feasible,
but due to the peak broadening of the small particles, a superposition of both peaks is possible.
Pol-Edern Le Renard et al.(2011) [25] was studied on magnetic and in vitro heating properties of
SPIONs and they found that, The superparamagnetic properties of magnetic silica composite
microparticles embedding nanoscale maghemite iron oxides are preserved in the injectable
formulations for the whole range of concentrations that allow syringe ability. These properties also
remain preserved in the implants formed in situ. The magnetic properties as well as the heating
capacity, which improved with increase in particle fraction, can be extrapolated from the
concentration of magnetic microparticles. With these AMF parameters, a straightforward
determination of the dissipated heat is now possible. In association with the previous in vivo
studies, this further allows for the modeling of tissue heating in vitro and in vivo, and this
improves our understanding of the heated livery through formulations intended for magnetically
mediated hyperthermia in the treatment of solid tumors. Ahmad Gholami et al.(2015) [26] were
studied on Lipoamino Acid Coated Superparamagnetic Iron Oxide Nanoparticles Concentration
and Time Dependently Enhanced Growth of Human Hepatocarcinoma Cell Line. And they found
that the cytotoxic effects of naked and some surface coated SPION on hepatocarcinoma cells
revealed that SPION at lower concentrations can be beneficial for these cells because of their
nutrient effect.
However, at concentrations higher than 50 micro gram /mL the trend was reversed and the
cell viability was decreased. Generally, it was concluded that SPION have dual impact on Hep-
G2: cell growth promotion and toxicity. In the initial phase (at concentrations from 1 to 50 micro
gram /mL), the dominant mechanism is the former one; however, by increasing nanoparticles
concentration, cytotoxic effect progressively rises and eventually becomes the main mechanism, if
aggregation or sedimentation of particles did not happen. Surface modification of SPION
especially the ones coated with LAA’s can maintain growth-enhancing effect. The reason may be
the controlled release of ionic iron into the cells. Biocompatible LAA coated SPION can be used
as targeted delivery of materials for diagnostic and therapeutic purposes. Alexander L. Kovarski et
al. (2006) [27] studied on ESR of thermal demagnetization processes in ferromagnetic
nanoparticles and the results comes out that ESR data indicate that the process of thermal
demagnetization of the tested particles is very complex, and some magnetic ordering remains in
the particles even above the Curie temperature, measured by static magnetic measurements.
Processes of thermal demagnetization in the vicinity of the Curie temperature in the alloys and
manganites are significantly different. Further studies of the thermal demagnetization processes in
ferromagnetic nanoparticles and deeper understanding of their mechanisms are crucial for
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
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developing effective mediator particles for magnetic fluid hyperthermia with parametric feedback
for biological applications [28-29].
SYNTHESIS METHOD TO OBTAIN SPINEL FERRITE NPS
Spinel ferrites can display the SPM behavior at room temperature. This is a very special
condition demanded for applications in the biomedical field. However, it is necessary to have a very
smaller NPs size. In order to face this, the choice of the appropriate synthetic methodology is
fundamental. For example, classical solid state routes are not suitable because the higher
temperatures used normally lead for bigger NPs size. Therefore, some researchers have developed a
wide range of synthetic approaches towards spinel ferrites like Co-precipitation, Sol- Gel Auto
combustions, Hydrothermal, Solvothermal, Decomposition and Microwave synthesis etc.
CONCLUSIONS
1) The Iron Oxide based material should be design as multiphase composite such that it
shows the different magnetic properties from each phase. The Curie temperature is in between 40 -
500C so that it can be easily demagnetized. It should be single spin domain so that it is easily
oriented by external applied field
2) It is found from the literature the microwave combustion technique is the one of the
promising technique for preparation of sample with the possibility of utilizing cheap precursors,
short reaction time and nanocrystalline products.
3) Keep it in mind that the magnetic material should be biocompatible therefore researcher
also focuses on non toxicity and PH value of material
REFERENCES.
[1] L. Zhou, J. Xu, X. Li, F. Wang, Mater. Chem. Phys. 97 (2006) 137.
[2] R. Chen, G. Song, Y. Wei, J. Phys. Chem. C 114 (2010) 13409.
[3] G. Schmid, D. Fenske, Phil. Trans. R. Soc. A 368 (2010) 1207.
[4] M. L-r, W. Chen, Y. Tan, L. Zou, C. Chen, H. Zhou, Q. Peng, Y. Li, Nano Res. 4 (4) (2011)
370.
[5] J.K. Oh, J.M. Park, Prog. Polym. Sci. 36 (2011) 168.
[6] D. Pan, H. Zhang, T. Fan, J. Chen, X. Duan, Chem. Commun. 47 (2011) 908.
[7] J. Alam, U. Riaz, S.M. Ashraf, S. Ahmad, J. Coat. Technol. Res. 5 (2008) 123.
[8] N. Bao, L. Shen, Y. Wang, P. Padhan, A. Gupta, J. Am. Chem. Soc. 129 (2007)
[9] M. Mahmoudi, H. Hosseinkhani, M. Hosseinkhani, S. Boutry, A. Simchi, W.S
[10] R.J. Hill, J.R. Craig, G.V. Gibbs, Systematics of the spinel structure type, Physics and
Chemistry of Minerals 4 (1979)
[11] V.G. Harris, Modern Microwave Ferrites, IEEE Transactions on Magnetics 48 (2012)
[12] W.H. Bragg, The structure of magnetite and the spinels, Nature 95 (1915) 561.
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
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Super Paramagnetic Behavior Of Mn Substituted Zn Ferrites Nanopartical Prepared
By Sol-Gel Auto Combustion Route
M. J. Gothe, A. P. Bhat, K. G. Rewatkar
Department of Physics, Dr. Ambedkar College, Nagpur-10 India
Department of Electronics, RTM Nagpur University, Nagpur-10 India
ABSTRACT
Manganese substituted zinc ferrite nanoparticals ( MnX Zn1-X Fe2O4with x = 0,0.5,1 ) were
synthesized via sol-gel auto combustion route. X-ray diffraction (XRD), transmission electron
microscopy (TEM), scanning electron microscopy (SEM), and electron dispersive X-ray (EDX)
have been used to investigate the prepared Magnetic Zinc Nanocrystal (MZN). Magnetic properties
of the prepared samples have been detected by vibrating sample magnetometer (VSM), at room
temperature and the results of the prepared MZN exhibits a superparamagnetic (SPM) behaviour.
SPM nanocrystals are promising applications in medical science such as drug delivery,
bioseperation and magnetic resonance imaging (MRI).
Keyword: Magnetic measurements, Superparamagnetism
INTRODUCTION
Spinal ferrites are most widely used magnetic material due to the low cost. Mn-Zn ferrites
have many important applications, particularly in electronics and engineering industry [19].
However, (MnX Zn1-X Fe2O4with x = 0.5, 1) exhibits superparamagnetic (SPM) behavior by using
the study of VSM. Superparamagnetism is a form of magnetism, which appears in small
ferromagnetic or ferrimagnetic nanoparticles. In nanoparticles, magnetization can randomly flip
direction under the influence of temperature. Typical time between two flips is called “Neel
relaxation time”. In the absence of external magnetic field, the time used to measure the
magnetization of the nanoparticals is much longer than the “Neel relaxation time”. Their
magnetization appears to be in an average zero. They are said to be in the Superparamagnetic state.
An external magnetic field is able to magnetize the nanoparticles. In paramagnetism, their magnetic
susceptibility is large.
SPM is not just an abstract topic of study in advance physics. But it also has a practical
applications in the medical field such as MRI technology, DNA & RNA experimentation treatment
of hyperthermia and drug delivery [1-10]. It is also used in high-tech sensors (of the sort used in
aerospace technology) and other aspect of nanotechnology. For high performance applications in
biomedicine, the magnetic nanocrystals are required to posses’ small width in proportion to length
distribution and uniform spherical shape that gives superparamagnetic properties [11, 12]
EXPERIMENTAL
Preparation of sample:
Powder of MZN ferrites particles were prepared by sol-gel auto combustion method. by
Using analytical grade chemical reagents of Mn(NO3)24H2O, Zn(NO3)26H2O, and
Fe(NO3)39H2O and its stoichiometric proportions were first dissolved in deionized water. The
mixture of solution was heated at 800c till the complete mixture transformed in to gel. The gel of
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
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the solution which were ignited and burnt by microwave oven on 600 watt for 7 minute to obtain
ash powder. The powders were annealed slowly at 8000c in a furnace for 4 hours after intermediate
grinding.
Characterization Technique:
The phase identification and crystalline structural analysis of the thermally treated powder
was analyzed by X-ray diffraction (XRD, Bruker AXS D8 advance, Cu K radiation λ = 0.1540
nm). The size and morphology of such prepared samples were characterized by scanning electron
microscopy. (SEM, Camca SU, SEM probe) and transmission electron microscopy (TEM, Phillips,
CM-200) for magnetic hysteresis loops were measured using a vibrating sample magnetometer
(VSM. Lakeshore 7410).
RESULTS AND DISCUSSION:
Fig.1. a & b) shows XRD pattern and broading of high intensity peak
The crystalline structures of MZN were characterized by XRD as shown in above fig.1 (a)
& (b). All the Bragg’s reflections have been indexed which confirmed the formation of simple cubic
spinel structure in single phase without any impurity peak. The strongest reflection and broadening
of high intensity peak comes from the (311) planes as depicted by JCPDS card 74-2403. which
denote the spinel phase appearing at 35.070 & 35.110.The crystalline size were calculated for
(MnXZn1-XFe2O4with X = 0.5,1) using high intensity (311) peaks and using Scherer formula i.e.
dhkl = 0.9 /cos.The values are found to be15nm and 16 nm.The lattice parameter for
Mn0.5Zn0.5Fe2O4 and MnFe2O4 The values are found to be 8.4812 Å & 8.4699 Å. it was found
that the lattice parameter decreases with increasing cations substitution of Mn2+ due to difference
of ionic radius (ionic radius of Zn+2 is 1.35 Å & Mn+2 is1.40Å) and its atomic mass.
b
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
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Fig .2 A typical TEM image of MnxZnxFe2O4, x =0.5,1 nanoparticles.
A typical TEM image of the prepared MZN nanocrystals has been shown in above fig.2. the
circular diffraction rings are clearly visible, indicating the nano crystalline nature of MZN. Most of
the such prepared magnetic nanocrystals are nearly spherical structure as per shown in TEM. Dark
regions are representative nanoparticles which are in agreement with the SEM findings below. The
morphogical studies of the Mn-Zn ferrite powder was carried out using SEM. This type of electron
microscope is capable of producing high resolution images of a sample surface [13-14] due to the
manner in which the images are created. SEM images have a characteristic three dimensional
appearance and are useful for judging the surface structure of Mn-Zn ferrite. It is found that the
powders were made up of particles with the size in the nano range as shown in fig.3. In which the
powder form of the solid sample was mounted on the conducting resin with dispersion treatment,
indicating that the almost spherical and homogeneous nanoparticles with the average size of MZN
are about 28 nm. This result is in agreement with the result of XRD and TEM analysis [17].
The chemical composition of such prepared ferrites samples was further confirmed by
energy-dispersive X-ray analysis (EDX). The result shows that Me2+/Fe3+ ratio is about 0.5 which
is in agreement with the expected stoichimetry in each case as shown in fig.3 EDX system are
attachment to SEM or TEM instrument where the imaging capability of the microscope identifies
the specimen of interest. The data generated by EDX analysis consist of spectra showing peak of
Mn, Fe, and O, corresponding to the elements making up the true composition of the sample being
analysed.The EDX technique is non-destructive and specimen of interest can be examined in
situation with little or no sample preparation.
Fig 3.SEM and EDX spectrum of the sample Mn Fe2O4
100nm
100nm
MnFe2O4
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
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The magnetic properties of the prepared MZN were investigated with a VSM as shown in Fig.4.
Fig 4: Magnetization curve of nano crystalline MnXZn1-XFe2O4with X = 0.5,1. At room temp.
The magnetization curves measured at room temperature, from the curve the measured
magnetic saturation values are about 28 emu/g for Mn0.5Zn0.5Fe2O4 and 20 emu/g for MnFe2O4.
The corecivity of the as prepared magnetic nanocrystals at room temperature is negligible, because
in a nano size particals many single domains are uniformly magnetized with all the spins aligned in
the same direction. The magnetization will be in reversed spin rotation, since there are no domain
walls to move. I.e. this is the reason for the very high coercivity observed in thin research module
with reported values between 38 between 177 Gauss in small nano particles [18, 20]. The
superparamagnetic behaviour can be represented by hysteresis curve as shown in fig.4.
Superparamagnetism occurs in nanoferrites which are single domains i.e. composed of a single
magnetic domain. This is possible only when their diameter measures below 3-50 nm, depending on
the materials. Superparamagnetic materials do not retain any significant amount of magnetization in
the absence of externally applied magnetic field and thus do not form aggregates.
A curve between magnetization and applied field (20kG) at room temperature is shown in
fig.4. It shows typical superparamagnetic nature with no trace of hysteresis and coercivity 38G and
almost zero remanence. It also prominently showed non-attainment of saturation magnetization even
at 20KG.
The nonsaturation of M-H loop and the absence of hysteresis remanence and coercivity at
room temperature strongly suggests the presence of superparamagnetic behavior.The values of Ms
are higher in multidomain bulk ferrites (45 emu/g) [15], than the Mn-Zn compounds represented in
the present work (Ms=28 emu/g).
The lower values of saturation magnetization and nanocrystaline ferrites pertaining to the
fact that the surface effect play vital role in supporting noncollinearity of magnetic moments on
their surface. Nanocrystaline particles consist of ferromagnetically aligned core spins and spin-glass
like surface layers .The disordered behavior in spin from the surface of the nanoparticles pushes to
modify the magnetic properties of these materials specially when surface/volume ratio is very large
[16].
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
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CONCLUSIONS:
We have successfully synthesized single phase simple cubic spinal polycrystalline of MZN ferrite
and particles with an average crystalline size of 28 nm by sol-gel route. We observed from the
XRD, that the lattice parameter decreases with increasing cation substitution.
The prepared MZN ferrites exhibits’ superparamagnetic behavior at room temperature. The
Superparamagnetic properties of MZN ferrites are significant for biomedical applications. Such as
drug delivery, bioseperation and magnetic resonance imaging. From our research and findings, it
seems that the sol-gel autocombustion method may offer to synthesis other ferrite nanocrystals with
novel magnetic properties.
REFERENCES:
[1] Li, H. Wang, J. Magn, Magn. Mater. 309 (2007) 295.
[2] S. Y. Zhao, R. Qiao, X.L. Zhang, Y. S. Kang, I Phys. Chem. C111 (2007) 7875.
[3] S. Sun, H. Zeng, D. B. Robinson, S. Raoux, P. M. Rice, S.X. Wang, G. Li, J. Am. Chem. Soc.
126 (2004) 273.
[4] H. Deng. X, Li, Q. Peng, X. Wang, J. Chen, Y. Li, Angew. Chem. Int. Ed. 44 (2005) 2782.
[5] T. Hyeon, Y. Chung, J. Park, S. S. Lee, Y. W. Kim, B. H. Park, J. Phys. Chem. B 106 (2002)
6831.
[6] S. R. Ahmed, P. Kofinas, Macromolecules 35 (2002) 3338.
[7] L. Li, G. Li, R. L. Smith H. Inomata, Chem. Mater. 12 (2000) 3705.
[8] V. Berbenni, C.Milanese, G.Bruni, A.Marini, I.Pallecchi, Thermochim. Acta 447 (2006) 184.
[9] H.Yang, X.Zhang, C.Huang, W.Yang, G.Qiu, J.Phys. Chem. Solids 65 (2004) 1329.
[10] T.Meron, Y.Rosenberg, Y.Lereach, G.Markovich, J.Magn. Magn. Mater. 292 (2005) 11.
[11] J.Park, J.joo, S.G.Kwoon, Y.Jang, T.Hyeon, Angew. Chem. Int. Ed. 46 (2007) 4635.
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
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Linear Power Amplifiers: Basic Considerations of Switched-Mode Assisted Amplifiers
N. V. Shiwarkar#, A. P. Bhat
&, K. G. Rewatkar
$
#Department of Electronics, Dr. Ambedkar College, Deeksha Bhoomi, Nagpur-22, India
&Department of Electronics, RTM Nagpur University, Nagpur-33, India
$Department of physics, Dr. Ambedkar College, Deeksha Bhoomi, Nagpur-22, India
Corresponding author: [email protected]
ABSTRACT:
The paper presents a combined high efficient amplifier system consisting of a linear
amplifier unit with a switched-mode(class D) current and voltage stage arranged in parallel. With
this topology the fundamental drawback of conventional linear power amplifiers - the high loss is
avoided. Compared to a pure class D (switching) amplifier the presented system needs no output
filter to reduce the switching frequency harmonics. This filter (usually of cascaded type) generally
try to avoide the transient response of the system and impairs the feedback loop design.
Furthermore, the low-frequency distortions of switching amplifiers caused by the inter system
response delay of the power transistors is avoided with the presented switched-mode assisted linear
amplifier system. This consideration as a master-slave system with a guiding linear amplifier and a
supporting class D slave unit. The work describes the operating principle of the system, analyzes the
fundamental relationships for the circuit design and presents simulation results with the help of
virtual lab.
Keywords: class D, harmonics, transient error, etc
INTRODUCTION
Conventional linear power amplifiers are replaced by switching (class D) amplifiers in an
increased quantity to overcome the essential drawback of linear amplifier systems[l]. The output
voltages of a class D amplifier imply a switching frequency component (harmonics) which may be
reduced by a proper filtering technique and circuitry. However, this filter - which has to be in
general of higher order type - reduces the dynamic response and increases the output impedance of
the whole amplifier system. Also, the interlock delay time of the usually applied bridge topologies, a
ripple of the DC supply voltage +V and the on-state voltages of the power semiconductor devices,
transistor and freewheeling diode may result in low-frequency distortion [2] which hardly can be
reduced by the described switching frequency output filter but has to be lowered by using a special
control loop design [3, 4]. A further problem of switching amplifiers is the possible occurrence of
harmonic frequency components which may result for a small signal-to switching-frequency ratio or
if a pulse width modulation strategy with variable switching frequency is applied. This harmonic
noise basically cannot be lowered by the output low pass filter because the frequency components
lie within the power bandwidth of the amplifier. A concept is proposed consisting of a parallel
arrangement of a class D switching system and a conventional linear amplifier stage.
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
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Fig. 1 Simplified circuit diagram of a linear power amplifier
The output filter of the switching amplifier is reduced to a single coupling inductor
determining the switching frequency ripple. Although the linear amplifier can be considered as
active filter which compensates the switching frequency ripple and the modulation noise, the basic
idea of the proposed switched-mode assisted linear amplifier is that the linear amplifier acts as the
guiding master system whereas the task of the class D (slave) stage is to take over the current of the
linear stage (current dumping). In the ideal (stationary) case the linear power amplifier only has to
deliver the ripple of the class D stage which significantly reduces its power losses. Contrary to a
passive output filter of a conventional switching amplifier the linear amplifier of the proposed
concept also reduces low-frequency distortions and harmonic components. However, a very low
output impedance of the linear system part is importance to get a high noise rejection. This
performance is to be considered by an appropriate design of the linear amplifier circuitry and
feedback system. Furthermore, the switched mode assisted linear amplifier allows a significant
reduction as an idealized class D amplifier. Therefore, concerning the losses the proposed system
can be seen as intermediate solution between pure linear and pure class D power amplifiers.
SYSTEM CONTROL - CALCULATION OF POWER LOSSES
The guidance of the class D part is realized by a current controller whose reference value is
identical to the current through the load. Thus, only the control error and the ripple is delivered by
the linear stage. Instead of an explicit subtraction of reference value (load current i) and actual value
(class D stage output current is, ) the calculation of the controlling quantity can be done in an
implicit manner by direct measurement of the linear stage output current . As an alternative, a pulse
width modulator (PWM) with a superimposed linear current controller or other types of modulation
is to maintain the harmonics develop in the master and slave and reduced by the low pass filter
current controllers being well known from switched-mode power supplies (e.g., conductance
control) can be applied.
Fig.2 Circuit diagram of a switched-mode assisted linear power amplifier.
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
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The pulse width modulator allows a switching frequency being constant which is, however,
of not essential significance for this application as stated before. An advantage of the hysteresis
controller is it’s inherent over modulation ability which yields a more efficient utilization of the DC
supply voltage *V. On the other side, PWM current controllers with their well defined switching
instants allow an easier extension of the class D stage to a parallel arrangement being operated in an
optimum phase shifted manner in order to reduce the total ripple current, or increase the effective
switching frequency, respectively. However, it should be mentioned that there exist solutions for
two hysteresis controlled converter branches (arranged in parallel) where a suboptimal phase shift
can be achieved in a very simple way. In the following, the losses of the linear amplifier stage shall
be calculated for the case that a hysteresis current controller with a constant tolerance band is
applied. It is assumed that the load current I and the output voltage V can be treated as constant
within the switching interval T or, that there exists a sufficient signal-to-switching frequency ratio,
respectively ( Fig.3). 'Switching Frequency The output voltage U (averaged within a pulse interval
T) is determined by the duty cycle. According to V, = Ldi,,/dt the switching frequency f, = 1/T can
be calculated.
Power Losses
The power losses of the linear stage depend on its operating mode, where one has to
distinguish between class A (linear amplifier with quiescent current eliminating crossover
distortions) and class B (without quiescent current) mode. the linear stage where it is assumed that
for class A mode the quiescent current is as small as possible, the class A mode losses are twice the
losses of the class B mode.
Frequency effect on the Amplifier Bandwidth.
The demand for low power losses implies a small ripple amplitude . However, for a defined
maximum switching frequency f, this would result in the usage of a high value of the inductance L.
On the other side, a higher value of L reduces the power bandwidth of class B of the switched-mode
current dumping stage. If we normalize gain bandwidth with respect to the value V/R (maximum
load current, resistive load EL = R assumed), kA = AI/(V/R), we receive for a class-B linear stage
(kA ... normalized ripple amplitude). The power bandwidth of the current dumping stage can be
defined as fB = R/ (2nL) .
The switching frequency to- bandwidth ratio is linked to the losses of the linear system. For
a given maximum switching frequency and a required power bandwidth of the whole amplifier the
current ripple (and therefore the power losses) is fixed. However, there are some possibilities to
overcome this fundamental limitation:
Usage of a higher supply voltage for the switching
Fig.3 Voltage and current waveforms of a switched-mode assisted linear power amplifier;
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
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Fig. 4: switching technology module.
(a): switch stage output voltage; (b): output currents of the class D system and of the linear stage; (c)
transistor currents for class B mode of the linear amplifier part;
(2) splitting-up the current dumping stage in several parallel branches operated in a phase shifted
manner or application of a three-level topology
(3) Higher order type coupling impedance of the switching stage . It has to be noted that the
described effect only limits the power bandwidth of the current dumping stage and not of the whole
amplifier system whose dynamic response (especially the slew-rate) is determined by the linear
stage. MOSFET safe operating area a) and the power losses b) of conventional linear power
amplifiers and switched mode assisted linear (SMALA) amplifiers (both class B mode) for
sinusoidal output voltage and different load current displacement factors.
SIMULATION RESULTS
A prototype system of a switched-mode assisted amplifier system with the nominal values
V = 20V, R = 2.5R (resistive load ZL = R ; RMS value of the sinusoidal output voltage: 50V), fB =
l0 kHz, f = 200kHz shall be calculated briefly. The power losses of the proposed system are far
beneath the lsosses of conventional linear power amplifiers, especially for the case of non-resistive
loads (e.g., the losses of a conventional linear amplifier would be P = 1kW for M=l and Cosc=0.5).
However, it has to be admitted that the losses shown in Fig.4 for the switched mode assisted
amplifier do not include the losses of the switching stage. On the other side, the efficiency of
switched-mode bridge topologies usually lies above 95% so that the total losses of switched-mode
assisted amplifiers would not be increased significantly as compared to conventional linear
amplifiers. The current wave shapes of the simulated 1kW amplifier system are shown in Fig.5.
There, the pulse response demonstrates the limited slew-rate of the switched-mode current dumping
system. In this case the output current of the linear amplifier i,,, not only has to compensate the
ripple of the switching state but also has to take over the dynamic current peaks This effect results in
increased power losses of the linear stage.
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
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LINEAR STAGE DESIGN
A very low magnitude Z of the high-frequency output impedance z of the linear stage is of
fundamental importance for a high input voltage signal-to-noise ratio (SNR) of the system because
the ripple current AI of the switching stage generates a noise voltage. Today, the output stages of
linear amplifiers usually are realized by using power MOSFET source followers [5]. The output
impedance of source followers is defined by the transconductance (g) of, e.g., the upper transistor
and is also influenced by the output impedance Ri of the driver stage in the upper frequency region.
Fig5 : three level NPC switching level
Fig. 6 : Output impedance of source followers.
In general, the transconductance of power MOSFETs is far too low to get an output
impedance in the desired level. This fact is not of primary significance because the effective output
impedance is reduced by the loop gain of the feedback system. For the described system we have to
adjust the loop gain to 50dB at 200kHz. A higher loop gain would allow to further increase the
SNR but would reduce the stability margin of the linear amplifier system. The frequency response
of the amplifier mainly is determined by that of the voltage booster stage because the output current
buffer usually shows a much higher bandwidth due to the application of MOSFETs and a high-
frequency driver stage using bipolar video transistors. Contrary to conventional linear power
amplifiers the frequency design of the voltage booster has to be performed not only regarding the
power bandwidth but also has to consider the switching frequency of the current dumping stage in
order to get the described reduction of the output impedance. Therefore, we use a symmetric wide-
band push pull differential amplifier arrangement with a relatively low gain of 10 which, on the
other side is high enough to use a conventional OP-AMP as feedback amplifier This OP-AMP is
used as a PI-controller to increase the loop gain in the region of lower frequencies and to enhance
the linearity of the system. A further improvement of the loop gain could be achieved by the well
known principle of splitting-up the voltage booster into a low frequency part with full output
voltage swing and a high-frequency small-signal path being arranged in parallel to increase the loop
gain in the switching frequency region [6].
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
24
ISOLATION OF SWITCH SIGNALS
The NPC topologies as shown would allow a SMALA to be built with equal power rating to
a full bridge design using an equal number of equal The hysteresis control strategy using a pair of
controllers retains the very simple sensing structure of the original. The drive of the outer
MOSFETS is also simple, requiring non-isolated drivers. The inner NPC MOSFETs do require
isolated gate drives. The low N channel device can be isolated using a level shifting boot strap
driver HVIC. Most logically, this would be a half bridge driver with independent channels, such as
the IR21xx family of devices [12], driving S3 and S4.
However, no equivalent device is available for the P channel devices, capable of level
shifting to a more negative voltage for device S2. Recent digital isolators using IC scale magnetic
coupling techniques from Analog Devices [13] and NVE corporation [14] have low propagation
delay, low power consumption, and excellent noise immunity.
CONCLUSIONS
It is observed that a simple extension of the hysteresis current control demonstrated in a previous
two level SMALA implementation is suitable for controlling a three level Neutral Point Clamped
(NPC) converter. The NPC topology allows the use of lower voltage switches and lower switching
frequencies to implement high power audio amplifiers. It has to be noted that concerning the output
impedance the realization of the output stage using bipolar power transistors would probably be a
better solution because of their higher trans-conductance as compared to MOSFETs.
ACKNOWLEDGEMENT
The author would thankful to the Department or Electronics RTMNU for providing Audio
Engineering details literature and alumni student working in practical world of audio Engineering
field.
REFERENCES
[1] Walker, G. R. “A Class B Switch-Mode Assisted Linear Amplifier”, Power Electronics, IEEE
Transactions on, Vol.18, No.6, pp.1278- 1285, Nov. 2003.
[2] G. B. Yundt, “Series or Parallel-Connected Composite Amplifiers,” IEEE Transactions on
Power Electronics, Vol PE-1, , pp 48-54. January 1986
[3] H. Ertl, J.W. Kolar and F.C. Zach, “Basic Considerations and Topologies of Switched- Mode
Assisted Linear Power Amplifiers,” IEEE Transactions on Industrial Electronics, Vol 44, No. pp.
116-123. 1997.
[4] N. S. Jung, N. I. Kim, and G. H. Cho, "A New High-Efficiency and Super-Fidelity Analog
Audio Amplifier with the aid of Digital Switching Amplifier: Class K Amplifier," presented at 29th
Annual IEEE Power Electronics Specialists Conference, 1998.
[5] R. A. R. van der Zee and A. J. M. van Tuijl, "A Power-Efficient Audio Amplifier Combining
Switching and Linear Techniques," IEEE Journal of Solid-State Circuits, vol. 34, no.7, pp. 985-991,
July 1999.
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
25
Synthesis Of ALMgFe12O19 Hexa Ferrite For Data Storage Application
P. M. Bodele#, A.P. Bhat
@, R.M. Singh
#, S. T. Chatterjee
# S. J. Dhoble
& K.G. Rewatkar
#
#Department of Physics, Dr. Ambedkar College, Nagpur-10 India @Department of Electronics, RTM Nagpur University, Nagpur-10 India
&Department of Physics, RTM Nagpur University, Nagpur-33 India
Corresponding author: [email protected]
ABSTRACT
Manganese substituted Aluminum ferrite nanoparticals (AlxMg2xFe12-2xO19 with x = 0,0.5,1 )
were synthesized via sol-gel auto combustion route. X-ray diffraction (XRD), transmission electron
microscopy (TEM), scanning electron microscopy (SEM), and electron dispersive X-ray (EDX)
have been used to investigate the prepared Magnetic aluminum Nanocrystal (MAN). Magnetic
properties of the prepared samples have been detected by vibrating sample magnetometer (VSM), at
room temperature and the results of the prepared MZN exhibits a superparamagnetic (SPM)
behaviour. Their magnetic moment, saturation magnetization (Ms ), remanent magnetization (Mr,)
coercivity (Hc,) SQR, etc. are measured and studied. The temperature dependence of magnetization
as well as susceptibility is studied and discussed.
The electric properties of samples are also studied. The dc conductivity of the samples is
measured to know about their conduction mechanism. Activation energy is also determined to study
understand utility of samples in the industrial electronics. Basically, the samples are semiconducting
materials. By measuring their Seebeck coefficient and its temperature dependence, the type of
charge carrier is also confirmed.
.
Keyword: Magnetic measurements, Superparamagnetism
INTRODUCTION:
The development of civilization has been intimately linked with the ability of human beings
to work with materials. Indeed, the journey of this development was initiated in the Stone Age and
successively it got promoted in the copper and bronze, then Iron Age. This era of Nanoscience and
Nanotechnology of materials are the all new facets of such immense development. Magnetic
materials have a major contribution in the development of Nanotechnology and Nanoscience. The
recent researches in nano magnetic materials have enriched the applicability of nanotechnology in
the makings of new modern gadgets. In fact, the nanotechnology has developed the interest of end
users to purchase appliances and gadgets allied to Nanoscience and Nanotechnology.
The magnetic properties of materials have found to be changed drastically when the
material is transformed into nano scale. The recent researches in this field have confirmed that
materials with such structural, magnetic and electrical properties can easily be used for the
development of digital memories, cores, transducers, aero space devices, analyzers, cell phone
memories, etc. [D]. Besides, it is further cited that with further improvisation in such materials, they
can be used in telecommunication, satellite communication, computer technology, laser technology,
etc. When the size of the magnetic particle is reduced to nano scale, the multi-domain structure
generally turns into a single domain structure. Hence, the possible domain wall resonance is avoided
and the material can work at higher frequencies [F]. Moreover, the nanostructured materials have
the prospective to have better energy efficiency and storage.
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
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This research work is intended to provide an updated study of nano scale magnetism for
data storage applications. Moreover, it emphasizes on the synthesis, characterization and
applications of nanoscaled magnetic materials especially Al-Mg substituted Hexaferrite
Nanoparticles. It not only deals with the physics and chemistry but also structural, morphological,
magnetic and electrical characteristics of such nano magnetic materials.
EXPERIMENTAL
Preparation of sample:
Powder of MAN ferrites particles were prepared by sol-gel auto combustion method. by Using
analytical grade chemical reagents of Mn(NO3)24H2O, Al(NO3)26H2O, and Fe(NO3)39H2O and
its stoichiometric proportions were first dissolved in deionized water. The mixture of solution was
heated at 800c till the complete mixture transformed in to gel. The gel of the solution which were
ignited and burnt by microwave oven on 600 watt for 7 minute to obtain ash powder. The powders
were annealed slowly at 8000c in a furnace for 4 hours after intermediate grinding.
Characterization Technique:
The phase identification and crystalline structural analysis of the thermally treated powder was
analyzed by X-ray diffraction (XRD, Bruker AXS D8 advance, Cu K radiation λ = 0.1540 nm).
The size and morphology of such prepared samples were characterized by scanning electron
microscopy. (SEM, Camca SU, SEM probe) and transmission electron microscopy (TEM, Phillips,
CM-200) for magnetic hysteresis loops were measured using a vibrating sample magnetometer
(VSM. Lakeshore 7410).
RESULTS AND DISCUSSION:
Fig.1. a & b) shows XRD pattern and broading of high intensity peak of AlxMg2xFe12-2xO19
b
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
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The crystalline structures of MAN were characterized by XRD as shown in above fig.1 (a)
& (b). All the Bragg’s reflections have been indexed which confirmed the formation of simple
hexagonal structure in single phase without any impurity peak. The strongest reflection and
broadening of high intensity peak comes from the (107) planes as depicted by JCPDS card 84-1531
and 80-1197. which denote the spinel phase appearing at 30.070 & 35.110.The crystalline size were
calculated for (AlxMg2xFe12-2xO19 with X = 0.5,1) using high intensity peaks and using Scherer
formula i.e. dhkl = 0.9 /cos.The values are found to be 5nm and 15 nm.The lattice parameter for
Mn0.5Al0.5Fe12O19 and MnFe2O19 The values are found to be 5.4812 Å & 10.4699 Å. it was
found that the lattice parameter decreases with increasing cations substitution of Mn2+ due to
difference of ionic radius (ionic radius of Zn+2 is 1.35 Å & Mn+2 is1.40Å) and its atomic mass.
Fig .2 A Fig: SEM result of Al0.7Mg1.7Fe11.3O19 x =0.5,1 nanoparticles.
A typical TEM image of the prepared MAN nanocrystals has been shown in above fig.2. the
circular diffraction rings are clearly visible, indicating the nano crystalline nature of MAN. Most of
the such prepared magnetic nanocrystals are nearly spherical structure as per shown in TEM. Dark
regions are representative nanoparticles which are in agreement with the SEM findings below.
The morphogical studies of the Mn-Al ferrite powder was carried out using SEM. This type
of electron microscope is capable of producing high resolution images of a sample surface [13-14]
due to the manner in which the images are created. SEM images have a characteristic three
dimensional appearance and are useful for judging the surface structure of Mn-Al ferrite. It is found
that the powders were made up of particles with the size in the nano range as shown in fig.3. In
which the powder form of the solid sample was mounted on the conducting resin with dispersion
treatment, indicating that the almost spherical and homogeneous nanoparticles with the average size
of MZN are about 15 nm. This result is in agreement with the result of XRD and TEM analysis [17].
The chemical composition of such prepared ferrites samples was further confirmed by
energy-dispersive X-ray analysis (EDX). The result shows that Me2+/Fe3+ ratio is about 0.5 which
is in agreement with the expected stoichimetry in each case as shown in fig.3 EDX system are
attachment to SEM or TEM instrument where the imaging capability of the microscope identifies
the specimen of interest. The data generated by EDX analysis consist of spectra showing peak of
Mn, Fe, and O, corresponding to the elements making up the true composition of the sample being
analysed.The EDX technique is non-destructive and specimen of interest can be examined in
situation with little or no sample preparation.
100nm
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
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Fig 3.SEM and EDX spectrum of the sample Mn Fe12O19
The magnetic properties of the prepared MZN were investigated with a VSM as shown in Fig.4.
Fig 4: Magnetization curve of nanocrystalline AlxMg2xFe12-2xO19 with X = 0.5,1. At room temp.
The magnetization curves measured at room temperature, from the curve the measured
magnetic saturation values are about 28 emu/g for Mn0.5Aln0.5Fe2O4 and 20 emu/g for
MnFe12O19. The corecivity of the as prepared magnetic nanocrystals at room temperature is
negligible, because in a nano size particals many single domains are uniformly magnetized with all
the spins aligned in the same direction. The magnetization will be in reversed spin rotation, since
there are no domain walls to move. I.e. this is the reason for the very high coercivity observed in
thin research module with reported values between 38 between 177 Gauss in small nano particles
[18, 20]. The superparamagnetic behaviour can be represented by hysteresis curve as shown in fig.4.
Superparamagnetism occurs in nanoferrites which are single domains i.e. composed of a single
magnetic domain. This is possible only when their diameter measures below 3-50 nm, depending on
the materials. Superparamagnetic materials do not retain any significant amount of magnetization in
the absence of externally applied magnetic field and thus do not form aggregates.
A curve between magnetization and applied field (20kG) at room temperature is shown in
fig.4. It shows typical superparamagnetic nature with no trace of hysteresis and coercivity 38G and
100nm
MnFe12O19 MnFe12O19
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almost zero remanence. It also prominently showed non-attainment of saturation magnetization even
at 20KG.
The nonsaturation of M-H loop and the absence of hysteresis remanence and coercivity at
room temperature strongly suggests the presence of superparamagnetic behavior.The values of Ms
are higher in multidomain bulk ferrites (45 emu/g) [15], than the Mn-Al compounds represented in
the present work (Ms=28 emu/g).
The lower values of saturation magnetization and nanocrystaline ferrites pertaining to the fact that
the surface effect play vital role in supporting noncollinearity of magnetic moments on their surface.
Nanocrystaline particles consist of ferromagnetically aligned core spins and spin-glass like surface
layers .The disordered behavior in spin from the surface of the nanoparticles pushes to modify the
magnetic properties of these materials specially when surface/volume ratio is very large [16].
CONCLUSIONS
Doping effect on resistivity
The compositional dependence of resistivity (ρ) (at 393 K) for AlxMg2xFe12-2xO19
(0≤x≤1) (x = 0.00-0.10; y = 0.00-1.00) is presented in table 3.5. It is clear that the value of
resistivity increases from a value of 1.80 ×10 10 O cm for the undoped sample to 3.25 ×1010 O cm
for the sample with dopant level of Al = 0.06 and Mg =0.60, but decreases with further increase in
the dopant level. The observed variation can be explained in terms of site occupancy and nature of
the substituted ions. The substitution of Al 3+ to the Mg 2+ ion induces perturbation in both the
electron-density and symmetry around the 2b lattice site [15]. Lachevallier et al. [15] has reported
that among five lattice sites of Fe3+, the nearest neighbors of Mg ion in the Al-layer are 12k, 4f 2
and 2b (octahedral sites located in R block). 2b site is at a minimum distance of 0.340 nm to the 2d
site of Mg 2+ ions compared to the distance of 0.366 nm and 0.365 nm for 4f 2 and 12k sites.
Thus the presence of La near the octahedral site would not only change the separation between the
Fe 3+ ions but may also reduce the Fe obstruct electron transfer between Fe It has already been
reported that the Al 2+ 2+ -O-Fe and Fe2+ 3+3+ bond angle [30] which causes to ion pairs and
increases the resistivity. ions have a strong tendency to occupy the octahedral lattice sites (4f 2 ,
12k) [37], therefore, substitution by La-Ni ions partially replaces some of the Fe 3+ at the
octahedral site to consequently increase the resistive of Al-Mg hexaferrite. Enhancement of
resistivity is of significant 2+ 2+ 3+
Effect of applied field frequency on dielectric constant
The variation of dielectric constant (έ) for AL-Mg doped strontium-barium hexaferrite
series with respect to frequency from 100 Hz to 1 MHz are reported in figure 3.26. It has been
observed that έ, in general, show a decreasing trend with increasing applied frequency. For the
undoped strontium-barium hexaferrite, έ decreases continuously from 15.8 ×102 to 13.60 as the
frequency is increased from100 Hz to 1 MHz. However, the dispersion in the values of έ is fast at
low frequencies while it slows down at higher frequencies, in the studied range of frequency.
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
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Figure 5: “Variation of dielectric constant (έ) with applied frequency
Effect of applied field frequency on dielectric loss tangent
The variation of dielectric loss tangent (tan d) with applied field frequency (from 100 Hz to
1 MHz) for the La-Ni doped strontium-barium hexaferrite series are presented in figure 3.30. It can
be noted that the value of tand decreases with increasing applied frequency. For the undoped
strontium-barium hexaferrite, tand decreases continuously from 4.5 to 0.10 as the frequency is
increased from 100 Hz to 1 MHz. However, the dispersion in the values of tan d is fast at low
frequencies while it slows down at higher frequencies, in the studied range of frequency. We have
successfully synthesized single phase simple cubic spinal polycrystalline of MAN ferrite and
particles with an average crystalline size of 5 nm and 16 nm by sol-gel route. We observed from the
XRD, that the lattice parameter decreases with increasing cation substitution.The prepared MAN
ferrites exhibits’ superparamagnetic behavior at room temperature. The Superparamagnetic
properties of MAN ferrites are significant for biomedical applications. Such as drug delivery,
bioseperation and magnetic resonance imaging. From our research and findings, it seems that the
sol-gel autocombustion method may offer to synthesis other ferrite nanocrystals with novel
magnetic properties.
The present research work is devoted to set an attempt for the development of Nano
sciences and technology in the field of magnetic materials. The magnetic materials have always
been remaining an issue of discussion in every decade of discovery of sciences. The effect of Al and
Mg substitution along with the doping of in AlxMg2xFe12-2xO19 has been investigated. The
hexagonal M-ferrite composition was successfully synthesized by sol-gel auto-combustion method.
The Al doping of ferrite helped in better densification. The Al-doped ferrite showed lowest
dielectric permittivity and dielectric loss. Also it showed highest permeability, lowest relative loss
factor and highest resistivity, respectively. The permeability was stable up to 1 MHz frequency.
According to all the data presented, it can be said that Al-doped would be a good material for multi-
layer ferrite chip data staorage
In the present investigation, a system of AlxMg2xFe12-2xO19 (0≤x≤1) is developed using
hybrid technique which is popularly known here as ‘Microwave Induced Sol-Gel Combustion
Route’. The synthesized M-type Calcium hexaferrite are found to exhibit a hexagonal symmetry,
P63/mmc or D46h (No. 194) with two formula units per unit cell.
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
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The substitution with non-magnetic ions such as, Al results in low magnetic transition (Tc)
temperature. These compounds may act as a suitable substrate for thin epitaxial deposition of
hexaferrite films..
It is worth interesting to quote here that the nano hexaferrite particles synthesized in the
present investigation are observed to be having very small particle size of the order of 5.52 nm
earlier it is found to be 11.52 by shard sabale
ACKNOWLEDGMENT
The author would thankful to the Department of nanoscience and nanotechnology for effective help
and support during the project and UGC-DAE canter Indore for financial support and help
REFERENCES:
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126 (2004) 273.
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International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
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Dielectric Properties of Microwave Absorbing Material Used In Computer RAM
A.P. Bhat1, S. J. Dhoble
2, K.G.Rewatkar
3
1Department of Electronics, RTM Nagpur University, Nagpur India-33 2Department of Physics, RTM Nagpur University, Nagpur India-33 3Department of Physics Dr. Ambedkar college , Nagpur India-22
[email protected], [email protected]
ABSTRACT:
This study was to produce sheets of microwave absorbing materials using conductive
polyaniline dispersed in a silicone rubber matrix and to characterize the electromagnetic properties
(absorption, transmission and reflection of electromagnetic energy; and electric permittivity and
magnetic permeability) of these sheets in the X-band (8 - 12 GHz). Two sheets were produced: one
2.80 mm thick and the other 4.39 mm thick. The thinner sheet absorbed incident microwave energy
more efficiently, attenuating up to 88% of the incident electromagnetic energy. Also, calculations
were performed in order to determine the electromagnetic parameters that optimize the absorbent
properties of these sheets. These calculations showed that these materials could be combined and
altered to produce absorbing materials with a wide range of absorbing characteristics.
Keywords: microwave absorbing material, conducting polyaniline, flexible sheets
INTRODUCTION
In general terms, it is possible to describe the interaction of an electromagnetic wave with
microwave absorbing materials (RAM's) as a phenomenon where the electromagnetic energy is
transformed into thermal energy. According to the principle of energy conservation, the
electromagnetic wave impinging on a material can be reflected, attenuated or transmitted through
the material. The response of the material to the wave depends on its intrinsic characteristics; the
absorption of energy by the material does not necessarily means that the material will heat up,
sometimes the opposite can occur, i. e., the material can cool down.
To produce a RAM, it is necessary to select a matrix material (insulating polymer, porous
substrate, etc.) that will act as a support for an energy-absorbing center. The absorbing center may
consist of, for example, a conducting polymer with good mechanical and chemical properties and
whose electrical conductivity can be modulated5. The behavior of conducting polymers illuminated
by electromagnetic radiation in the X-band (8 - 12 GHz) has been studied to understand how the
conductivity of these polymers affect the absorption of electromagnetic energy and how these
materials can be used in the production of RAM's.
The electric permittivity (ε) and magnetic permeability (μ) are parameters related to the
dielectric and magnetic properties of a material, and directly associated to their absorbing
characteristics. The relative permittivity and permeability are represented by Equations 1 and 2,
respectively; the values of these parameters are calculated from the experimental values of the
transmission and reflection coefficients of the material.
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In these equations, the primed and double-primed symbols denote real and imaginary
components. When the material is lossy, the permittivity and permeability of are complex and some
of the incident electromagnetic energy is dissipated1. In the case of a magnetic material, losses are
produced by changes in the alignment and rotation of the magnetization spin. When an
electromagnetic wave illuminates a dielectric material, there is the formation of electric dipoles
which align in the direction of the applied field, and the dipole alignment is directly related to the
absorption of electromagnetic energy .The real component of the permittivity is associated with the
ability of the material to store energy, while the complex component is responsible for energy
dissipation. The use of polyaniline as an energy absorbing center allows the production of dielectric
RAM's with negligible magnetic permeability. Using a simple physical model, one can say that
dielectric materials behave as an electric circuit consisting of capacitors in parallel with resistors.
The knowledge of how to process materials and combine components, additives, and
polymer matrices are decisive factors in the final properties of the RAM21. Therefore, the aim of
this work was to measure the dielectric parameters of sheets produced by mixing polyaniline with
silicone rubber. The properties of the sheets were analyzed in the X-band in order to determine the
transmission, absorption and reflection coefficients of the material and also its electric permittivity
and magnetic permeability. Analytical calculations were performed to determine the absorbing
characteristics of the sheets for different thicknesses and when used in combination.
MATERIALS AND METHODS
Chemical procedures
The energy absorbing center (conductive polyaniline) of the RAM was processed first. This
polymer was produced chemically and in laboratory scale. The conductive form of polyaniline
(green color - emeraldine salt- powder form) was prepared from aniline and by the action of the
oxidizing agent ammonium peroxydisulfate in an acidic reaction medium (dodecylbenzenesulfonic
acid - DBSA). Following, the doped polyaniline powder was added to a matrix composed of either
one of two types of silicone rubber, L9000 and RTV630 (GE Silicones). The mixture was
homogenized by mechanical agitation, and the processed materials were poured into 30 × 30 cm
molds and dried at 70 °C overnight. Two different sheets were obtained; the sheet produced with
L9000 silicone rubber had a thickness of 2.80 mm, and the one produced with RTV630 silicone
rubber was 4.39 mm thick.
Electromagnetic evaluation
The electromagnetic properties of the sheets were analyzed using the waveguide technique
(closed system) in the frequency range 8 to 12 GHz (X-band). A rectangular wave guide was
coupled to a VSWR analyzer connected . The setup used for the measurements is shown in
Figure 1. Small samples (about 2 cm2) were cut from the sheets and inserted into the waveguide.
The complex electromagnetic parameters, (permittivity and permeability) were obtained from the
measured values The attenuation of the incident radiation by the RAM's was obtained from the
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
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difference between the reflectivity of an aluminum plate (reference material, alloy 2024) and that of
the same aluminum plate covered with the RAM.
Analytical reflectivity of RAM's.
In the case of single-layer RAM's, a layer of absorbing material is placed in contact with a metal
plate (Figure 2). Changing the thickness of the absorbing materials and their electromagnetic
properties (permeability and permittivity) can vary the absorbing characteristics of the RAM.
The reflectivity of electromagnetic energy of a single-layer RAM as function of frequency can be
calculated using the following equation:
In the above equations, μ and ε are, respectively, the complex permeability and permittivity
of the absorbing material, k is the wave number, f is the frequency of the incident electromagnetic
wave, c is the speed of light in vacuum, and d is the thickness of the absorbing layer. Both the
permeability and permittivity may vary with frequency.
Two or more layers of absorbing material can be stacked (Figure 3) in order to improve the overall
performance of the RAM.
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The reflectivity of electromagnetic energy by a two-layer RAM can be calculated using the
following equation10:
RESULTS AND DISCUSSION
In Figure 4 are shown the results derived from measurements (reflected, transmitted and
absorbed electromagnetic energy) as a function of frequency for the two single-layer RAM's
produced in this study. Figures 4 a andb show that both materials behave in a similar way; the
absorbed, reflected and transmitted energies vary approximately linearly with frequency. Also, for
both materials, the value of absorbed energy increased by about 10% with frequency in the
frequency range of the measurements. The maximum energy absorption, which was measured at
8 GHz, was 18.5 and 16.2% for the materials with 2.80 and 4.39 mm respectively, showing that the
thinner material had better absorbing properties. When the reflectivity of these materials were
measured using an aluminum back plate (a situation similar to their use in the real world, i.e.,
RAM's are used to coat metallic objects) the 2.80 mm thick material absorbed 88% of the incident
energy at 8 GHz whereas the 4.39 mm thick material absorbed 71% of the incident energy this
frequency. Lower values of absorption were obtained for higher frequencies. The behavior of both
materials clearly indicates their potential for the production of RAM's, especially for civilian
applications. The electromagnetic properties of the absorbing of these materials are shown in
Figure 5.
These differences in behavior shown in Figure 5a and b are due to the different matrix
compounds (silicon rubbers) used, since the absorbing center (conducting polyaniline) was the same
for both materials. For the silicone rubber L9000 (Figure 5a), the real and imaginary values of the
relative permittivity vary from 6.5 to 5.5 and from 2.1 to 1.85; for the silicone rubber
RTV630 (Figure 5b) the real and imaginary relative permittivity vary little with frequency and their
average values are about 3.5 and 5.0, respectively. As expected, since the materials were produced
using dielectric components, the values of the real and imaginary magnetic relative permeability
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
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were approximately 1 and 0, respectively, and did not show any major variation with respect to
frequency.
By definition, the real permittivity values are equal or larger than one. In an ideal material
with zero dielectric loss, the real and imaginary permittivities are equal to 1 and 0, respectively; in
this situation the material does not store (ε' = 1) nor dissipate (ε" = 0) energy. The larger the value of
the imaginary component of permittivity the larger is the loss in the material. A material with low
dielectric loss can store energy, but will not dissipate the stored energy. On the other hand, a
material with high dielectric loss does not store energy efficiently and part of the energy of the
incident wave is converted into heat within the material23.
Based on this information and on the results of Figures 5a and b one is led to the conclusion
that the 2.80 mm thick material (silicone matrix L9000) is indeed has the best absorbing properties
of the two RAM's produced in this study, as is evidenced by the results depicted in Figures 4a and b.
Based on the experimental data (permittivity and permeability) and on Equation 3, it is
possible to optimize the thickness of the RAM's with respect to the absorption of energy and its
intended use. Figures 6a and b show how changes in the thickness affect the ability of the RAM's to
absorb energy. The curves in these figures were obtained assuming that the RAM's were used to
coat a flat metallic plate (Figure 2). Another interesting result shown in these figures is the
displacement of resonance peak (maximum absorption) as a function of the thickness; note,
however, that the absorption amplitude does not vary significantly. These calculations also show the
RAM produced with the silicone rubber L9000 absorb electromagnetic energy more efficiently.
The single-layer materials developed in this study can be combined into multi-layer
materials to produce RAM's with different absorbing properties. Using the experimental data
collected on the single-layer materials, it is possible to simulate the behavior of two-layer RAM's
using Equation 5. Figure 7 shows the results of simulations when these materials are combined in
different configurations to produce a material with a total thickness of 10 mm. In these curves,
Z1 and Z2 refer to absorbing materials with the same electromagnetic properties of the materials
prepared with silicone rubber type L9000 and RTC6300, respectively. The results in Figure 7a were
obtained using 2 and 8 mm thick layers; in Figure 7b, both layers were 5 mm thick. It is interesting
to observe that the order in which these materials are stacked plays an important role in determining
the final properties of the RAM, affecting the amplitude and the position of the resonance peak.
CONCLUSION
The attenuation pattern of electromagnetic energy by the absorbing materials suggests that
the electrical conductivity of these materials is related to the quantity of absorbing centers
(conducting polyaniline) and type of polymer matrix (silicone rubber), which modify the impedance
of absorbing materials. In absorbing materials, a large fraction of the incident energy must be
attenuated, which is a consequence of the equilibrium between electric conductivity and electric
losses.
The materials produced with conductive polyaniline dispersed in a silicone matrix
attenuated the incident radiation up to about 88%, demonstrating that these materials can be used as
absorbers of electromagnetic radiation. Also, the analytical calculations demonstrated the
importance of optimization tools to produce absorbing materials with the required properties, since
variations in the thickness or the combinations of materials with different properties can improve the
absorbing qualities of the final material.
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
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Another important characteristic of the materials produced using conducting polyaniline and
silicone rubbers is their low density compared with conventional absorbers based on ferrites
(absorption 10 dB), with densities ranging from 4 to 5 g.cm-3.
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[11]. Lee SM. International Encyclopedia of Composites. New York: VCH Publishers; 1991.
[12]. Clark DE, Diane CF, Stephen JO and Richards S. Microwaves: Theory and Application in
Materials Processing III. Westerville: The American Ceramic Society; 1995.
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
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Gsm Based Heart Monitoring System for Pre-Mature Babies
A.P.Bhat., S. P. Mesharam., K. K. Dhawad., A.A. Ballal
Department of Electronic and computer science RTM Nagpur University Nagpur-33
Department of Applied Elelctronics, LAD College of Women’s RTMNU Nagpur,
ABSTRACT
Application of engineering and technology has proved its significance in the field of
biomedical. It not only made doctors more efficient but also helped them in improving total process
of medication. The Patient monitoring system is also a new step in the automation of supervision for
doctors. The Patient monitoring system for doctors provides solution for this. It continuously
provides following information to doctors.
1. Heart pulse rate
2. Temperature
3. Body Position
As used in hospital the same system can be used for a person who is not under the continuous
observation of doctor. Also this project to aim towards as the monitoring tool for premature baby
place in Incubator. The normal body temperature of a healthy and resting human being is stated to
be at98.4°For 37°C. Though the body temperature measured on an individual can vary, a
healthy human body can maintain a fairly consistent body temperature that is around the mark of
37.0°C.An indication is sent to the doctor when the pulse rate starts fluctuating just above or below
ideal pulse rate which is 72 pulse/min., for a normal human body. Body positioning plays a
significant role in determining the pressure on heart. Since GSM endows its users with a voice and
data channel and the possibility of sending an indication to other terminals. Thus GSM find its use
and adaptability in our project.
Keywords:- GSM, Premautar baby, biomedical parameter, communication protocol, ISM Band
INTRODUCTION
Cases of heart attacks and deaths due to lack of help are increasing. For this purpose personal
monitoring are best solution. For heart patients this kit gives indication to their doctors and they
immediately get medical help. Whenever beat rate of person exceeds more than 72pulse/min.,
doctor get immediate indication and help will be sent as fast as can. Cardiovascular diseases are
often very critical and serious condition, the change is so rapid, the one attack can bring about great
suffering to patients, and even lead to syncope or sudden death. Especially coronary heart disease,
cardiomyopathy, and arrhythmia history, family history of sudden cardiac death, heart
transplantation and other medical conditions, history, the disease has a sudden, random, high rate
characteristics of sudden death, usually after the acute onset of symptoms within 1 hour may cause
death and malignant ventricular fibrillation within 12 minutes and even cause sudden death in
patients suffering from serious heart disease in patients with the above mentioned is attack patients.
Drawbacks of present electrical method and the wireless system:
The current heart rate monitoring system uses a heavy and bulky setup at both ends i.e. at the
patient’s as well as at the doctor’s. This in turn causes convenience problems for the patient and any
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
39
M
C
U GSM
BEEP
AMPLIFIRE &
FILTER
SENSOR
CKT
LCD
defect occurring at any stage may result in loss of information which may result in improper
diagnosis.
Need of system:
The present monitor puts forward a novel system that benefits from GSM module and telephony
standard widespread technology. This design adds to the traditional capabilities, the attractive
features of real time processing and possibility of monitoring the patient’s heart anywhere,
anytime. Apart from traditional typical capabilities, the new system presents additional features,
both in automatic analysis and in the communications interface (GSM transmission)
BLOCK DIAGRAM OF GSM BASED SYSTEM
Figure 1: Block diagram of HRM System
DESCRIPTION OF BLOCK DIAGRAM:
The above figure shows the block diagram of GSM based HRM(Heart rate monitoring )
system. Slight fluctuation in the normal heart rate , body temperature and change in body position
of patient will be sensed by the heart sensor , temperature sensor and posture detector respectively,
attached to the index finger. It will forward data to the microcontroller where it will be compared
with the normal value of body temperature and heart rate. Depending upon the parameters
considered by monitor, if it finds any parameter disturbed then the result is send to the doctor and he
may immediately take the necessary action. Thus without wasting the time patient can be treated
whereas sending the report can be done using GSM. The device will compare the three parameters
with the ideal parameters, if some fluctuations are noticed, the SMS is immediately sent to the
doctor. This message may be in the form of beeps to indicate the doctor. The system comprises an
implantable medical device that includes a sensor operable to produce an electrical signal
representative of heart sounds, a sensor interface circuit coupled to the sensor to produce a heart
sound signal, and a controller circuit coupled to the sensor interface circuit. The sounds are
associated with mechanical activity of patient’s heart and the controller circuit is operable to detect
a posture of the patient from a heart sound signal electrical signal representative of heart sounds, a
sensor interface circuit coupled to the sensor to produce a heart sound signal, and a controller circuit
coupled to the sensor interface circuit. The heart sounds are associated with mechanical activity of
patient’s heart and the controller circuit is operable to detect a posture of the patient from a heart
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
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sound signal GSM based heart rate monitoring and the display system is a portable and a best
replacement for the old model stethoscope, which is less efficient. It is a combination of a
instrumentation based heart rate monitor interface with a GSM module to transmit the heart rate of
patient to a remote location.
The functioning of this device is based on the truth that the blood circulates for every
heartbeat that can be sensed by instrumentation amplifier and sensing pad. Depending upon the rate
of circulation of blood the heart beat per minute is calculated. This calculated value is
communicated to the person through a GSM modem interfaced to it.
CIRCUIT DIAGRAM
Patient’s heart and the controller circuit is operable to detect a posture of the patient from a
heart sound signal electrical signal representative of heart sounds, a sensor interface circuit coupled
to the sensor to produce a heart sound signal, and a controller circuit coupled to the Sensor interface
circuit. The heart sounds are associated with mechanical activity of patient’s heart and the controller
circuit is operable to detect a posture of the patient from a heart sound signal
Figure 2: - sensor circuit Figure3: microcontroller circuitry.
WORKING
The above circuit shows the working of the heart rate monitoring system using GSM.
Here at pin no. 1, 9 and 10 are connected to 3 capacitors in parallel. A crystal oscillator is placed
between pin no. 9 and10.Pin no.7, 20 and 21 are connected to +5v. The capacitors are connected to
GND at one terminal, also pin no. 8 and 22 also to ground. The output of the microcontroller is
given at PORT C from PC0 to PC3 as LM35, Heart Beat Sensor, to ADXL X axis from Pin no. 23
to 26. The RXD and TXD of microcontroller is connected to TXD and RXD of mobile. A voltage
regulator is used to regulate the voltage which is supplied form a 9v battery and gives an output of
5v. This gives the entire working of heart rate monitoring system using GSM.
Components of block diagram:
HEART SENSOR
LM35
POSTURE DETECTOR
MICROCONTROLLER ATMEGA8
GSM MODEM
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
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Heart sensor:
The heart sounds are the noises a physician listens by using a stethoscope over the heart. They are
the noises of the heart valves shutting. These noises areHeart beat is sensed by using a high gain
amplifier using AD624Ad. The sensor is placed in such way that the differential instrumentation
amplifier transistor be used. The skin may be transmitted or low amplitude signal for detection. The
very small changes in in transmittance caused by the varying blood content of human tissue are
almost invisible. Various noise sources may produce disturbance signals with amplitudes equal or
even higher than the amplitude of the pulse signal. Valid pulse measurement therefore requires
extensive preprocessing of the raw signal.
The new signal processing approach presented here combines analog and digital signal processing
in a way that both parts can be kept simple but in combination are very effective in suppressing
disturbance signals. The setup described here uses of a siganal pickup sensor for transmitted for
sensing the signals and a instrumentation amplifier as detector. With only slight changes in the
preamplifier circuit the same hardware and software could be used with other detection concepts.
The nose problem of the circuit is solve using following circuit with the preamplifier and fixed band
filter
Figure 4:- sensing point and signal condition block.
The filter/amplifier circuit is a standard design and is documented in many sources (e.g. 0). The
signal from the IR sensor is very weak where the voltage is just around 50µV, containing a
significant noise level. The signal is affected by interference caused resulted from movement of
artefacts like rings and mains 50Hz. It is known that the standard ECG signals has the frequency
component in the range of 0.05-200H.if the filtered range is 0-50H, the signals dose not
suffering significant loss of quality or the information within the signal. The filtering possess is
necessary to block the higher frequency noise component present in the signal.
Features:
Heart beat indication by LED
Instant output digital signal
Easily available and less costly
Compact size
Working voltage +5v DC
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
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LM35:
The LM35 series are precision integrated- circuit temperature sensors, whose output voltage is
linearly proportional to the Celsius (Centigrade) temperature. The LM35 thus has anadvantage
over linear temperature sensors calibrated in ° Kelvin, as the user is not required to subtract a large
constant voltage from its output to obtain convenient Centigrade scaling. The LM35 does not
require any external calibration or trimming to provide typical accuracies of ±1⁄4°C at room
temperature and ±3⁄4°C over a full −55 to +150°C temperature range. Low cost is assured by
trimming and calibration at the wafer level. The LM35’s low output impedance, linear output,
and precise inherent calibration make interfacing to readout or control circuitry especially easy. It
can be used with single power supplies, or with plus and minus supplies. As it draws only 60 μA
from its supply, it has very low self- heating, less than 0.1°C in still air. The LM35 is rated to
operate over a −55° to +150°C temperature range, while the LM35C is rated for a −40° to +110°C
range (−10° with improved accuracy). The LM35 series is available packaged in hermetic TO-46
transistor packages, while the LM35C, LM35CA, and LM35D are also available in the plastic
TO-92transistor package. The LM35D is also available in an 8-lead surface mount small outline
package and a plastic TO- 220 pa
Features:
Calibrated directly in ° Celsius (Centigrade)
Linear + 10.0 mV/°C scale factor
0.5°C accuracy guarantee-able (at +25°C)
Rated for full −55° to +150°C range
Suitable for remote applications
Low cost due to wafer-level trimming
Operates from 4 to 30 volts
Less than 60 μA current drain
Low self-heating, 0.08°C in still air
Nonlinearity only ±1⁄4°C typical
Low impedance output, 0.1 W for 1 mA load
Posture detector using sensor:
The motivation to include posture detector in this project comes from the basic need to support the
independent living of elder people and smart personal alarm system to detect deviation in health
status. The earlier the fall is reported, the lower is the rate of morbidity-mortality. The use of
automatic fall detector decreases the fear of falling and improves the independence and the security.
It increases the quality of life of elder people. The measurement of movement of body is made with
the help of tilt sensor and accelerometer and the processing and analysis of movement is done with
the help of microcontroller. The graph shows the percentage of falling people which is likely to
increase every year. Patient’s posture is an important factor in the diagnosis of certain medical
disorders and may also be used to enhance therapy delivery. Posture detection involves determining
an orientation of the patient’s body, such as determining if the patient is in vertical position ,
determining if the patient in in a horizontal position (lying on the back, lying on the stomach, lying
on left or right side),or determining if the patient’s body is tilted to right, left, forward or backward.
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
43
Posture detection in accordance with embodiments describe herein may additionally include
determining an angle of tilt of patient’s body. Posture information may be tracked over time, stored,
and /or correlated. Information about patient posture may be evaluated with respect to the detection
of various disorders to determine if an association between patient’s postures and a particular
disorder is present. The posture of patient’s body, such as the inclination of the upper torso, may
be linked to various medical disorders, including disorders affecting the respiratory and/or
cardiovascular systems. Tracking patient’s posture over time can be used to assess the general well-
being of a patient.
The consequences of falling lead to sudden death or may lead to severe harm to the person which
can be listed to a few as follows:
30% of home-dwelling elderly (65+) fall each year
0-20% of elderly people fall recurrently(at least twice within 6 month)
Mean incidence of fall is about 650/1000 person years
860 older people (65+) died because of fall- related accidents
Microcontroller ATMEGA8
The ATmega8 features a 10-bit by executing powerful instructions in a single clock cycle;
the ATMEGA achieves throughputs up to 16 MIPS. The ATMEGA is a low-power CMOS 8-bit
microcontroller based on the AVR RISC architecture, approaching 1MIPS per MHz, allowing the
system designer to optimize power consumption verses processing speed. This microcontroller
works in 5 different modes which enhance its working.
The ATMEGA8 AVR is supported with a full suite of program and system development tools,
including C compilers, macro assemblers, program debugger/stimulator, in-circuit emulators, and
evolution kits.
GSM MODEM:
GSM (Global System for Mobile Communication; originally from Group Special
Mobile) is the most popular standard for mobile telephony systems in the world. The
implemented prototype utilizes a GSM modem. This modem can be operated by the micro-
controller by means of straight forward Hayes (ATA) commands, which follow the ETSI GSM 300
standard [9]. Using those commands, all functionality provided by a GSM terminal (voice, data,
SMS) can be exploited. It is easily available in the market and weighing less than 20gm, which is
smaller than a matchbox, thus allowing system reduction and integration. A separate module can be
demolished; especially suitable for the use of multiple machines at the same time. It is used to avoid
high communication costs to be incurred in a month; it sends in clusters which can be sent
automatically to a large number of goals the same information.
The purpose of this project is to measure the heartbeat and send the heart beat monitoring
and display system is the portable and best replacement for the old model stethoscope, which is less
efficient. It consist detector sensor based heart rate monitor interfaced with a GSM module to
transmit the heart rate of the patient to transmit the heart rate of the patient to a remote location.
Depending upon the rate of circulation of blood, the heart rate per minute is calculated. This
Calculated value is communicated to a doctor through a GSM modem interfaced to it. Based on
several scenarios we present the functionality of a prototype we are building. The application is
capable of monitoring the health of high risk cardiac patients. The smart phone application analyses
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
44
in real-time sensor and environmental data and can automatically alert the ambulance and pre-
assigned caregivers when a heart patient is in danger. It also transmits sensor data to a healthcare
center for remote monitoring by nurse or cardiologists. The system can be personalized and
rehabilitation programs can neither monitor the progress of a patient. GSM modem is
interfaced with the microcontroller with the help of ATA commands.
Feature of GSM:
Maximum transmission speed of 9.6Kbps
Coverage of 98% of the territory
SMS of around 150 characters
Cheap and are easily available
Support tri band mobile phones, a feature available with very few modules.
ADVANTAGES:
It is a small, low cost and a portable device which can be carried easily. Provides continuous
monitoring.
The mobility in the monitoring process is continuous. It is extremely useful to increase your
exercise level in a graded and careful manner in order to avoid injuries, overexertion, and excessive
stress on the cardiovascular system.
Using a heart rate monitor is an ideal method of assessing one’s cardiovascular condition, and
gauging the level of intensity of the exercise session.
The heart rate monitor is useful for individuals who have been advised not to exercise above a
certain heart rate because the heart rate can be monitored continuously.
It allows an athlete to be more in touch with your body and your heart rate.
An added bonus is that heart rate monitors not only supervises a person’s heart rate, it also
keeps track of the calories burned that you can monitor your improvement over time.
Heart rate monitor is an ideal is an ideal method in assessing your cardiovascular condition.
Disadvantages:
Using this for long durations could lead to soreness and chafing of the skin.
A sudden failure of network may hamper the working of the system.
APPLICATIONS:
We can also observe the ECG report of a patient on the cell phone with the help of this system.
By programming the GSM module with proper commands, the doctor as well as the family
members will be informed simultaneously about the fluctuations in patient’s condition. We can
also observe the ECG report of a patient on the cell phone with the help of this system. For keeping
track of cardiac system of an athlete to give him proper training. In defense areas, where the
remote location of a soldier can be determined. In hospitals, medical colleges, laboratories.
Future Aspects:
The system can be further improved in several aspects. Once the system requirement have been
clearly defined, the hardware can be optimized, especially regarding its size, weight and
consumption.
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
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Together with clinical analyses, the protocols to optimize the system performance should be
established. New technology such as Bluetooth, GPRS and UMTS could also enhance the
performance of the final product.
Furthermore works in progress to develop and integrate a real time multichannel mobile
telemedicine system capable of simultaneously transmitting medical data such as ECG, Non
Invasive Blood Pressure(NIBP) and SpO2 applying Bluetooth and GPRS technologies could be
done, to make the system more flexible.
RESULTS & CONCLUSION:
Gender
Age
HR on display
97
HR on scope
96
Error %
1.03 Male 22 83 81 2.41
Male 20 78 78 0
Male 22 90 87 3.33
Male 20 80 79 1.25
Female 22 77 77 0
Female 22 104 103 0.96
Female 19 75 75 0
Female 20 69 71 2.81
Female 22 83 85 2.35
Figure 5:- wave shape on CRO Chart 1:- Wave shape of ECG
CONCLUSION
Wireless intelligent heart beat rate monitoring system have made possible a new generation of
noninvasive, unobtrusive personal medical monitors applicable during abnormal activities. There
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
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are many ongoing researches on heart monitoring system using GSM and the main purpose behind
these researches is to make this system more compact, easily available at affordable price and to
include as many parameters as possible required for heart rate monitoring. New technologies could
also enhance the performance of the final project.
ACKNOWLEDGEMENT
The author would like to thank the staff of the Electronics’ and software simulation lab, LAD &
SRP College for their valuable assistance. Also the academic staff of Department of Applied
Electronics and software technology for continuous help and support.
REFERENCES
[1] Department of Computer Science and Engineering, Khulna University of Engineering &
Technology (KUET), Khulna 9203, Bangladesh, 2010.
[2] S.Allender, V.Peto, P.Scarborough, A.Boxer and M.Rayner ,Coronary heart disease
statistics, , British Health Promotion Research Group, Heart Foundation Department of public
health, University of Oxford, 2007.
[3] Mohamed Fezari, Mounir Bousbia-Salah, and Mouldi Bedda, “Microcontroller Based Heart
Rate Monitor”, The International Arab Journal of Information Technology, Vol. 5, No. 4,
2008.
[4] Dogan Ibrahim, Kadri Buruncuk,“Hear Rate Measurement from the Finger using a
low cost Microcontroller” ttp://www.emo.org.tr/ekler/a568a2a 8c19a31_ek.pdf
[5] Boashash, B., “Time-Frequency Signal Analysis and Processing: A Comprehensive
Reference”, Oxford: Elsevier Science, 2003.
[6] R. Fensli, "A Wireless ECG System for Continuous Event Recording and Communication to a
Clinical Alarm Station", Proc of the 26th Annual International Conference of the IEEE EMBS,
2004.
[7] http://www.brianmac.co.uk/maxhr.htm, Accessed on 02/09/2011
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
47
Microcontroller Based Heart Rate Monitor using Fingertip Sensors
A.P. Bhat1 , S. J.Dhoble
2 , K. G. Rewatkar
3
1Department of Electronics, RTM Nagpur University, Nagpur India-33 2Department of Physics, RTM Nagpur University, Nagpur India-33
3Department of Physics Dr. Ambedkar college, Nagpur India-10
ABSTRACT:
This paper presents the design and development of a microcontroller based heart rate
monitor using fingertip sensor. The device uses the optical technology to detect the flow of blood
through the finger and offers the advantage of portability over tape-based recording systems. The
important feature of this research is the use of Discrete Fourier Transforms to analyse the ECG
signal in order to measure the heart rate. Evaluation of the device on real signals shows accuracy in
heart rate estimation, even under intense physical activity. The performance of HRM device was
compared with ECG signal represented on an oscilloscope and manual pulse measurement of
heartbeat, giving excellent results. Our proposed Heart Rate Measuring (HRM) device is
economical and user friendly.
Keywords: Heart rate monitor; Fingertip sensor; Microcontrollers; Fourier transform
INTRODUTION
Heart rate is the number of heartbeats per unit of time, typically expressed as beats per
minute (bpm). Heart rate can vary, as the bodies need to absorb oxygen and excrete carbon dioxide
changes during exercise or sleep. Medical professionals to assist in the diagnosis and tracking of
medical conditions use the measurement of heart rate. Individuals, such as athletes, who are
interested in monitoring their heart rate to acquire maximum efficiency, also use it. The wave
interval is the inverse of the heart rate 0.
Changes in lifestyle and unhealthy eating habits have resulted in a dramatic increase in
incidents of heart and vascular diseases. Furthermore, heart problems are being increasingly
diagnosed on younger patients. Worldwide, Coronary heart disease is now the leading cause of
death 0. Thus, the medical community welcomes any improvements in the diagnosis and treatment
tools. In a clinical environment, heart rate is measured under controlled conditions like blood
measurement, heart beat measurement, and Electrocardiogram (ECG) 0. However, there is a great
need that patients are able to measure the heart rate in the home environment as well 0. A heart rate
monitor (HRM) is a simple device that takes a sample of the heartbeat signal and computes the bpm
so that the information can easily be used to track heart conditions. The HRM devices employ
electrical and optical methods as means of detecting and acquiring heart signals.
Heartbeat rate is one of the very important parameters of the cardiovascular system. The
heart rate of a healthy adult at rest is around 72 bpm. Athletes normally have lower heart rates than
less active people. Babies have a much higher heart rate at around 120 bpm, while older children
have heart rates at around 90 bpm. The heart rate rises gradually during exercises and returns
slowly to the rest value after exercise. The rate at which the pulse returns to normal is an indication
of the fitness of the person. Lower than normal heart rates is usually an indication of a condition
known as bradycardia, while higher than normal heart rates are known as tachycardia. Most HRM
devices use a design where the signal is acquired from the subject and a filtering function is applied
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
48
M C U Atmega 16
Bu
zze
r
GS
M
Signal Conditioning
Keyp
ad
LC
D
T
x
R
x
to remove the high order harmonics and noise from the signal. This is then followed by a hardware
or software that uses a zero crossing algorithms to count the number of beats during a given time
interval. The zero-crossing algorithm may lead to false readings caused by local noise that may
result in multiple locals zero crossings.
In this paper, we eliminated the zero-crossing problems by the use of Fourier Transform of
the digitized signal. This is a reliable technique that guarantees the automatic filtering of any
transient noise in the signal. The design and development of a low powered HRM device is
presented. The device provides an accurate reading of the heart rate using optical technology. We
incorporated the optical technology using standard infrared Light Emitting Diode (LED) and photo-
sensor to measure the heart rate using the index finger. A microcontroller is programmed to acquire
the signal using its embedded analogue to digital converter, ADC, and use the readings to compute
the heart rate; eventually, the reading is digitally displayed on a LCD. In case the HRM device is
used in a continuous monitoring mode 0, the device alert the medical professional or the person
accompanying of the patient, if the heart rate falls outside a given range. A local audible alarm is
also provided. The rest of the paper provides a discussion on the system overview; describes the full
description of the HRM device and lists the experimental results.
SYSTEM HARDWARE
The proposed HRM device is intended to have the following features:
− The system provides an optical mechanism to detect physical changes.
− The system supports a keypad to allow the user to enter information like name, age and
telephone number.
− The device is connected to an SMS modem to allow the transmission of an alert text message to
a medical profession
− The system provides a LCD screen to output the measured heartbeat rate.
− The device would provide an audible warning tone.
Figure 1. Diagram of the proposed device.
The system consists of an infra red (IR) LED as transmitter and an IR phototransistor as a receiver
that acts as a fingertip sensor
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
49
Fingertip Sensor
The sensor consists of an IR light emitting diode transmitter and an IR photo detector acting as the
receiver. The IR light passes through the tissues. Variations in the volume of blood within the finger
modulate the amount of light incident on the IR detector. Two practical configurations could be
implemented to achieve this function. In the first configuration, the finger can be placed between the
transmitter and the receiver as shown in Fig. 2. In the second design, both the IR transmitter and
receiver could be placed on the same plane and the finger would function as a reflector of the
incident light instead. The IR receiver monitors the reflected signal in this case. The IR filter of the
phototransistor reduces interference from the mains 50Hz noise.
Figure 2. Fingertip sensor Figure 3. Shows our pulse detection circuit.
The IR LED is forward biased through a resistor to create a current flow.
The values of resistors are chosen so that they produce the maximum amount of light output. The
photo-resistor is placed in series with the resistor to reduce the current drawn by the detection
system and to prevent short-circuiting the power supply when the photo resister detects no light.
Amplification and Filter Stage
The filter/amplifier circuit is a standard design and is documented in many sources (e.g. 0).
The signal from the IR sensor is very weak where the voltage is just around 50µV, containing a
significant noise level. The signal is affected by interference caused resulted from movement of
artefacts like rings and mains 50Hz. It is known that the standard ECG where the limits of
integration are determined from our knowledge of the signal and the time of observation. ECG
signal has frequency components in the range 0.05-200Hz. If filtered to the range 0-50Hz, the signal
does not suffer any significant loss of quality or information within the signal. The filtering process
is necessary to block the higher frequency noise components present in the signal. A capacitor of
1µF value at the input of each stage is required to block the dc component in the signal
Physical Properties
The device operates using a 9V-battery source, which should last for one year under normal
use. The package is small, lightweight and portable. The cost of the HRM device is kept to the
minimum in order to maintain a competitive edge with products currently available in the market.
The current estimate of the cost of the components is ~SDG150.
The microcontroller is the main component in our device. It acquires the ECG signal via the
ADC, computes the heart rate, and controls the LCD, keypad and GSM modem. The
microcontroller used in this study is the ATMEGA32. The driving software component includes the
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
50
calculation algorithm to measure the heart rate. The overall flow of the software application is
depicted in Fig. 4.
SYSTEM SOFTWARE
Discrete Fourier Transform
Determination of heartbeat bps depends on computing the Fourier Transform of the
heartbeat signal. Assuming a relatively high heart rate of 120 bpm, we can compute the minimum
sampling rate using the Nyquist-Shannon sampling.
Let us assume that a total N samples were collected during a time duration of T. If the time
between samples is ∆t, then the signal could be expressed as a piece wise step level, sample
and hold, as:
g (t) = g (ti ) where i∆t ≤ t < (i + 1)∆t---(1)
The Fourier Transform could be computed using the discrete data acquired by the ADC as follows:
G( f ) = ∑ g (t )e − j 2πfti -------------(2)
The real and imaginary components are thus given as
Re(G( f )) = ∑ g (ti ) cos(2πfti ) ----------- (3)
Im(G( f )) = −∑ g (ti ) sin(2πfti )-----------------(4)
Heart Rate Range
Our device computes the bps and compares the measurement against the maximum safe limit for the
subject in question. The maximum safe bpm value is computed depending on the gender of the
subject and his/her age. A number of methods for the maximum safe bpm are used in the medical
profession, including Martha, Londeree-Moeschberger, Miller and other techniques 0. For our
study, we adopted the formulae used by UK practitioners to compute the upper limits, HRMax as:
HRm=216 − 1.09 × Age of femael
HRm=202 − 1.09 × Age of Male
The algorithm below summarises the software:
Initialise input and output Ports
Enter user data
Forever Do
Acquire smples from ADC (5 Seconds) Compute Fourier components
Find Hearbeat rate
Display rate on LCD
If HR is outside the safe range
Send SMS msg to assigned person (if not already sent)
Switch Buzzer ON Else
Switch Buzzer OFF (if already ON)
Endif
Endforever
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RESULTS AND DISCUSSION
Fig. 4 shows the analogue signal acquired by the sensors and input to ADC port of the
microcontroller. The signal is consistent with the standard ECG signals used to measure the
heartbeat rate and is also used in other types of clinical diagnosis. In Fig. 5 we show the frequency
analysis of a typical heartbeat signal. The Fourier Transform of the 5sec interval shows a dominant
peak power spectral density obtained from the Fourier Transform at 72 bps. The second largest
peak, i.e. the second harmonic of the heartbeat rate, is located at 144bps. Note that the algorithm
implemented in this study searches only for the rate with the highest spectral density.
Figure 4. Analogue signal
The final device was used to measure the heartbeat rate of a number of male and female volunteers.
The results as well as the bps measured simultaneously using the heartbeat pattern of the same
volunteers as displayed on the oscilloscope are shown in Table. 1. These results show excellent
agreement
Figure 5. Fourier analysis and curve fitting
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Table 1. Heart beat rate measurement using the developed device and via an oscilloscope
Gender
Age
HR
on LCD
HR
on scope
Error %
Male 22 97 96 1.03
Male 22 83 81 2.41 Male 20 78 78 0 Male 22 90 87 3.33 Male 20 80 79 1.25
Female 22 77 77 0 Female 22 104 103 0.96 Female 19 75 75 0 Female 20 69 71 2.81 Female 22 83 85 2.35
Table 2. Measurements of heartbeat rate before and after exercise
Age Condition HR
(bps)
HR
Normal
(bps)
24years
Before
exercise 65 64
After
exercise 90 88
15
years
Before
exercise 91 88
After
exercise 110 100
CONCLUSIONS
The design and development of a low cost HRM device has been presented. The device is
ergonomic, portable, durable, and cost effective. Tests have shown excellent agreement with actual
heartbeat rates. This device could be used in clinical and nonclinical environments. Individual users,
e.g. athletes, can also easily use it during sporting activities. The device could also be used as a
monitoring instrument exploiting the SMS capabilities provided by this system.
This study used the standard Fourier Transform to compute the spectral density. The overall
efficiency of the device could be improved by the use of Fast Fourier Transforms.
The device could be further developed into a continuously Monitoring device that could be used to
detect the heart beat anomalies associated with certain heart conditions. This would be made
possible by analyzing the heartbeat signal in the frequency domain.
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REFRENCES
[1]Leslie Cromwell,” Biomedical instumentation and mesurment” 2nd edition Printice Hall of India
Pvt. Ltd. New Delhi 2004,p.150-160.
[2] R.S. Khandpur, “Handbook of Biomedical Instrumentation”, Tata McGraw Hill publishing
Company, New Delhi 1998, p12-125.
[3] W. J. Tompkins, “Biomedical digital signal processing”, Printice Hall of India Pvt. Ltd. New
Delhi 2004,p41
[4] M.Rayner, Coronary heart disease statistics,, British Health Promotion Research Group, Heart
Foundation Department of public health, University of Oxford, 2007.
[5] Mohamed Fezari, Mounir Bousbia-Salah, and Mouldi Bedda, “Microcontroller Based Heart Rate
Monitor”,The International Arab Journal of Information Technology, Vol. 5, No. 4, 2008.
[6]Dogan Ibrahim, Kadri Buruncuk,“Hear Rate Measurement from the Finger using a
low cost microcontro ller” http://www.emo.org.tr/ekler/a568a2a a8c19a31_ek.pdf
[5] Boashash, B., “Time-Frequency Signal Analysis and Processing: A Comprehensive Reference”,
Oxford: Elsevier Science, 2003.
[7] R. Fensli, "A Wireless ECG System for Continuous Event Recording and Communication to a
Clinical Alarm Station", Proc of the 26th Annual International Conference of the IEEE EMBS,
2004.
[8] http://www.brianmac.co.uk/maxhr.htm, Accessed on 02/09/2011
[9] Kohler, B.-U.; Hennig, C.; Orglmeister, R. The principles of software QRS detection.
Engineering in Medicine and Biology Magazine IEEE, vol. 21, , 2002 pp. 42 – 57.
[10] Piotrowskia Z.; Rózanowski K. Robust Algorithm for Heart Rate (HR) Detection and Heart
Rate Variability (HRV) Estimation. ACTA PHYSICA POLONICA, vol. 118, No. 2010, pp. 131 –
135,
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
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Simulation Of High Efficiency Techniques For N-Type Multi-Crystalline Solar Cells
A.P. Bhat1 , S. J.Dhoble
2 , K. G. Rewatkar
3
1Department of Electronics, RTM Nagpur University, Nagpur India-33 2Department of Physics, RTM Nagpur University, Nagpur India-33
3Department of Physics Dr. Ambedkar college, Nagpur India-10
ABSTRACT
Research and development activities on silicon solar cells mainly focus on cost reduction
and performance optimization. An alternative technology with a large potential regarding cost
reduction and improvement of environmental reuse is n-type multi-crystalline silicon solar cell
technology. N-type multi-crystalline silicon shows several advantages compared to p-type multi-
crystalline silicon. One of them is the lower sensitivity to some metallurgical impurities, which is an
important feature when solar cells are produced from less pure silicon. In general, high minority
charge carrier lifetime and competitive diffusion length have been reported for n-type mc-Si. This
paper repors a brief overview of the n-type multi-crystalline silicon material and properties explain
in the literature, together with the behavior of n-type multi-crystalline material. Fabrication
processes for high efficiency n-type multi-crystalline solar cells based on industrial techniques are
presented.
INTRODUCTION
Today, the majority of solar cell production is based on p-type multi-crystalline silicon
wafers (mc-Si) using a very suiatble technology. However, many alternative solar cell technologies,
based on wafers or thin films, are under investigation. The overall objective is to develop a lower
cost technology and possibl use of such a materials to improved environmental footprint. N-type
mc-Si solar cells, the paper represent an alternative technology which can potentially fulfill the
objective, with current wafer utilization and cell production processes.
There is a rising interest in n-type silicon for solar cell applications: besides being an
additional silicon feedstock source for the PV production it attracted attention by a higher tolerance
to common impurities as Fe or O. The resulting higher diffusion lengths compared to p-type
combined with the reduced degradation due to the lack of B-O complexes qualifies the n-type
materia[2].
One of the advantages of n-type solar cells is that they can use of alternative silicon sources.
Due to the exponential increase of the cell production, the supply rapidly evolved into a shortage,
which may continue in the years to come. Therefore, n-type silicon is of interest because
approximately 2000 tones/year of n-type wastes of Czochralski (Cz) grown Si mono-crystals are
available[5] . Eventually after mixing with lightly doped silicon, may be used in production of n-
type mc-Si ingots by means of directional solidification. Also upgraded metallurgical silicon may
be more conveniently used for production of n-type cells, in situations where n- type dopents are
present and hard to remove. Additionally, some metallurgical impurities have lower impact in n-
type ingots. The same is true for the boron-oxygen defect.
Research and developments on solar cells based on n-type Si substrates and low-cost
screen-Printed processing became active in the recent years, and several cell structures, such as
boron- diffused emitter type, and the aluminum alloy emitter have been reported. Several
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groups have reported very high pre and post processing minority carrier recombination lifetimes in
n-type mc-Si wafers, low recombination activity of transition impurities or very high carrier
diffusion lengths. Considering commercial-grade silicon wafers and high yeild industrial processes
inducing a wide variety of impurities and defects.
Material selection
Photovoltaic materials use inorganic semiconductors. The semiconductors of interest allow
the formation of charge-carrier separating junctions. The junction can be either a homojunction (like
in Si) or a heterojunction with other materials to collect the excess carriers when exposed to light. In
principle, a large number of semiconductor materials are eligible, but only a few of them are of
sufficient interest. Ideally, the absorber material of an efficient terrestrial solar cell should be a
semiconductor with a bandgap of 1–1.5 eV with a high solar optical absorption (104 − 105 cm−1) in
the wavelength region of 350–1000 nm, a high quantum yield for the excited carriers, a long
diffusion length low recombination velocity. If all these constraints are satisfied and thebasic
material is widely available, the material allows in principle the manufacturing of a thin-film solar
cell device.
lifetime and diffusion length
Crystalline silicon is a semiconductor material with a bandgap of 1.1 eV. Because of the
indirect bandgap character of silicon for photons with energy lower than 3.4 eV, it is clearly not an
ideal material for thin-film solar cells.
One basic reason for the selectring materrial is of high minority carrier lifetimes in n-type
silicon – compared to p-type is the lower mobility of the holes which corresponds to a lower
diffusion coefficient. That means, for the same diffusion length, the lifetime of the holes needs to
be three times higher than the lifetime of electrons in p-type Si.
Such higher lifetimes can be expected for n-type Si because of the absence of lifetime
reducing boron oxygen complexes (B-O), and lower recombination activity of transition metal
impurities. The thin film of crystalline Si can be grown either by low-temperature deposition
techniques which yield microcrystalline Si or by high-temperature techniques. the material
properties of the grown crystalline Si film are similar to the properties of bulk crystalline Si solar
material. Because of its relatively low absorption coefficient, crystalline Si layers have to be at least
30 μm thick to absorb sufficient light unless optical enhancement techniques are used to improve
the effective absorption.
III–V compound materials like GaAs, InP and their derived alloys and compounds, which
most often have a direct bandgap character, are ideal for photovoltaic applications, but are far too
expensive for large-scale commercial applications, because of the high cost of the necessary
precursors for the deposition and the deposition systems itself. The deposition systems for these
materials are either based on molecular beam epitaxy or metalorganic chemical vapour deposition.
LITRETURE REVIEW
The first functional, intentionally made PV device was by Fritts [5] in 1883. He melted Se
into a thin sheet on a metal substrate and pressed a Au-leaf film as the top contact. The modern era
of photovoltaics started in 1954 when researchers at Bell Labs in the USA accidentally discovered
that pn junction diodes generated a voltage when the room lights were on. Within a year, they had
produced a 6% efficient Si pn junction solar cell [6] By 1960, several key papers by Prince [9],
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Loferski [10], Rappaport and Wysoski [11], Shockley (a Nobel laureate) and Queisser [12],
developed the fundamentals of pn junction solar cell operation including the theoretical relation
between band gap, incident spectrum, temperature, thermodynamics, and efficiency. Thin films of
CdTe were also producing cells with 6% efficiency [13]. In 1994, Mobil Solar Energy (MA, USA),
which had developed a process for growing solar cells on Si ribbon (called the Edge defined film
growth or EFG process) instead of more costly wafers.
Cuevas et al [1] demonstrated exceptionally high minority carrier lifetime on n-type mc-Si
material from Euro-solar SpA of varying resistivity, even approaching levels of n-type mono-
crystalline silicon.The effective minority carrier lifetime measured on mc-Si n-type material after
phosphorus (P). Deposition exceeds the millisecond lifetime mark. The best result has been reached
for a 2.3 Ωcm wafer, whose average lifetime of 1.6 ms corresponds to a hole diffusion length of 1.4
mm. Ref [1] also shows the spectacular consequence of the phosphorus deposition on the
trapping effects which are frequently associated with the presence of metallic impurities. The
results obtained on a 0.5 Ωcm resistivity wafer show a lifetime increase by a factor of 10. The
lifetime also remains practically constant over a broad range of injection levels, which is a very
desirable feature for solar cell operation. A similar behaviour is found for the post- deposition
lifetime of the 0.9 Ωcm wafer, except at high carrier densities where the lifetime is affected by
Auger and emitter region recombination.
Martinuzzi et al [2] measured, on a raw n-type material voluntarily contaminated with Fe,
Co and Au (dose of 1013 cm-2), a bulk lifetime τp of around 100μs. after deposition, they reach, at
least, 300μs.
Corresponding to diffusion length values around 200 to 300 μm. Such high lifetime values have
never been observed in p-type mc-Si raw wafers, or they have been measured only after long
deposition treatments by phosphorus diffusion or [3]. In phosphorus gettered samples, the measured
values of diffusion length are higher than 500μm. The authors refer to a LBIC contrast scan map
indicating values of diffusion length and note that conversely to p-type material, they did not find
regions in which there is no improvement of the material and where the diffusion length remains
very poor (few tens of μm).
Deposition effect
Photovoltaic cells convert sunlight directly to electricity. Their principle of operation is the
same as that for photodiode light detectors. As mentioned before these devices are fabricated from
semiconductor materials, such as silicon (Si), gallium arsenide (GaAs), and copper sulfide (Cu2S)
and other materials. In a photovoltaic cell, incident sunlight photons remove electrons in the
semiconductor from their bonds so that they are free to move around inside the semiconductor
material.
Deposition of metal impurities is an essential step in the production of efficient photovoltaic
devices from relatively impure materials, such as multi-crystalline silicon. Such metals impurities
may be present in numerous forms, including substitution or precipitates of oxides, silicates or
silicides. Some of the more important metal contaminants are most dangerous when present
interstitially, such as Fe and Cr. Deposition techniques are usually very effective at removing
interstitial impurities, and since these are often the dominant lifetime-killers, large improvements in
lifetime can result.
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Macdonald et al. [4] investigated phosphorus deposition effect performing Neutron Activation
Analysis (NAA) on mc-Si. Thanks to this measurement technique, phosphorus deposition effect was
monitored for various contaminating elements: As, Sb, Sn, Zn (substitutional), Ag, Co, Cr, Cu, and
Fe (interstitial). It turns out that phosphorus deposition does not have any effect on substitution
elements. Their inability to be gettered arises because of their much lower diffusivity than
interstitial impurities, meaning that deposition deep into the wafer bulk in the relatively short time
used is not possible. The three dopent species (As, Sb and Sn) do not introduce deep levels in
silicon, and hence they have little impact on carrier lifetimes. The ineffectiveness of deposition
then is of little consequence for these elements. While the substitution diffusers did not respond to
deposition,they show that for Ag, Co, Cr, Cu and Fe there is a definite reduction, often quite large.
These elements all diffuse interstitially, and hence have much higher diffusivity.
Impurities sensitivity
N-type mc-Si demonstrates resilience to contamination introduced during processing or
wafer formation. This is because for many interstitial metallic impurities commonly found in silicon
solar cells, the impurity capture cross section for holes is much less than the capture cross section
for electrons.
Macdonald and Geerligs [6] modelled and measured the impact of the recombination caused by
intentional Fe contamination on the low injection lifetime of n-type and p-type wafers. The results
clearly show that the n-type wafers are much less strongly affected.
Coletti et al. [7] measured the effect of Fe contamination on the minority carrier lifetime of
p- type and n-type ingots after phosphorus deposition, boron co-diffusion and hydrogenation. The
as-grown minority carrier lifetime in the iron-doped ingots is about 1–4 and 6–30 μs for p and n
type, respectively. After deposition and hydrogenation the lifetimes in the n- and p-type Fe doped
ingots are approaching each other (lifetime is about two times higher in the n-type than in the p-type
ingot). As-grown lifetime values for the n-type reference are similar to the gettered values of the n-
type Fe ingot.
Schmidt et al. [8] theoretically determined the recombination parameters of isolated Cr and
CrB pairs in phosphorus doped n- and boron-doped p- type silicon wafers. Contrary to Fe, Cr has
larger capture cross section for holes and electrons (σn=2,3.10−13 cm2 σp= 1.10−13 cm2). In
consequence, relatively low concentration of interstitial Cr in bulk Si causes large lifetime
degradation in both p- and n-type mc-Si.
Ti has diffusivity several orders of magnitude lower than Cr or Fe. Because of its low
density, titanium, once introduced, remains at interstitial sites within the Si lattice after cooling to
room temperature. Interstitial Ti produces mid-gap donor and acceptor levels with large
capture cross sections and has a pronounced influence on the lifetime of minority carriers in p- and
n-type silicon. However, Geerligs et al. Compared effective diffusion length of p- and n- type mc-
Si ingots voluntarily contaminated with Ti (fig 1). The measurement results show that the carrier
diffusion length of the n-type wafers is not affected, whereas the carrier diffusion length of the p-
type samples is
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Figure 1 - Comparison, of n-type and p-type mc-Si ingots
Crystal impurity
The recombination rate of minority carriers in a mc-Si wafer is also related to the
interaction between impurities and crystal defects. The extended defects themselves are increase or
decrease in recombination, and in the large grains of mc-Si, dislocations are the most harmful
defects when they are decorated by impurities. Since the capture cross sections of the metallic
impurities are smaller in n- type silicon, it is expected that the consequences of the impurity-defect
interactions are reduced, and this reduction will be enhanced after deposition because of impurity
concentration decrease (ref [2]).
Martinuzzi et al. [2] made lifetime and LBIC contrast scan map of high densities
extended defects regions. Local values of minority carrier lifetime measured are at least ten times
higher than those found in a p-type sample containing similar defect densities. In a region where the
dislocation density is about 107 cm-2 , diffusion length of 120 μm and lifetime of 60μs were
measured which confirm the low recombination strength of extended defects.
Cotter et al [9] reported the excellent tolerance of n-type wafers to induced or introduced
defects. For feedstock considerations, the defects that exhibit high hole lifetime and low
electron lifetime suggest that n-type silicon wafers would be a better choice for high-efficiency
commercial silicon solar cells.Also Woditsch et al, in patent US6576831, describe that crystal
defects in n-type silicon are less active than in p-type silicon, and as a consequence, n-type mc-Si
with low proportions of active grain borders can be obtained.
Recombination activity of impurity point defects between p- and n-type mc-Si. Ref [10]
show that the as-grown extended crystal defects degrade less after phosphorus deposition in p-type
wafer than in n- type wafer. After hydrogenation, the lifetime improvement is similar for both p-
type and n-type which means no large difference in tolerance to extended defects between both
types. In conclusion, high minority carrier lifetimes and competitive diffusion length have been
reported in multi-crystalline n-type material. In addition, n-type mc-Si demonstrated resilience to
common contaminations during process or wafer formation.
Reduction of recombination activity after deposition in n-type mc-Si has been shown to be
as good as in p-type material. Crystallographic defects commonly introduced during wafer
growth, such as grain boundaries or dislocations, may exhibit low recombination strength in n-type
mc-Si, . fabrication process would lead to high efficiency silicon solar cells based on n-type mc-Si
substrates.
The main reasons for p-type mc- Si wafers are used for solar cell production are when space
power applications dominated because irradiation studies showed significant degradation of the
minority carrier lifetime and junction characteristics for n-type wafers [11]. Other reasons for the p-
type domination on the solar cell market are related to fabrication process issues such as easier
emitter formation by phosphorus diffusion. Moreover, new processes achieve excellent boron
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emitter formation and passivation and n-type solar cells benefit from structure design advantages
such as open rear side metallization, suitable for thin wafers and enhancing internal reflection.
EXPRIMETATION
Deposition efficiency of p-type emitter versus n-type emitter
Deposition via standard phosphorus diffusions remove easily a selection of interstitial
impurities (e.g. Fe) but the possible effect of these impurities on the recombination rate in the
diffused regions is to be considered. Macdonald et al. [12] investigated whether concentrations of Fe
for both boron- and phosphorus-diffused regions can cause a measurable increase in recombination,
as characterized by the emitter saturation current density. The author established that the deposition
efficiency of the phosphorus is much greater than for boron diffusions, despite the fact that a greater
number of boron atoms are required to achieve the same sheet resistance, due to lower carrier
mobility. The extracted current density values show that even though more than 99% of the Fe is
present in the phosphorus diffused regions and glass, there is no measurable impact on the
currenty density values. However, there is a clear two- to three-fold increase in the saturation
current for boron diffused samples.
These observations can be explained by the large difference in capture cross sections for
electrons and holes for the likely forms of Fe in these samples. In the n-type multi-crystalline
bases, which are of increasing interest, iron gettered to boron-diffused emitters may still have a
significant impact on recombination
RESULTS
Fe contamination
G. Coletti et al. [7] investigated the impact of Fe on n- and p-type wafers sliced from
directionally solidified microcrystalline ingots and on performance of solar cells fabricated from
these wafers. Short circuit current (Jsc) times open circuit voltage (Voc) product for the p- and n-
type references and for the Fe contaminated ingots. The performance is remarkably close to the
reference at positions between about 65% and 72% of the ingot height for the p-type ingots. In the
n-type ingot, the addition of Fe reduces the solar cell performance in most of the ingot. Jsc×Voc is
reduced in the bottom and the middle. In the top, the performance of the n- type reference decreases,
approaching the value of n-type Fe contaminated ingot. The authors showed that the main reason for
the degradation is a reduction in the diffusion length. From spectral response and reflectivity
measurements, the internal quantum efficiency (IQE) and the effective average minority carrier
diffusion length (Leff) were calculated. The main differences between the references and Fe
doped ingots are in the long wavelength response. No increase in recombination in the emitter
region is visible in the IQE measurements differently than reported by Macdonald et al. [10].
However, Mihailetchi et al. [13] note, for the same Fe-contaminated cells, a more distinct drop
in Voc than for non-Fe- contaminated cells, and attribute this to recombination in the emitter, in
line with the findings of Macdonald. Further experimental work is needed in order to
discriminate between the possible causes.
The authors also described a difference in the crystal structure development for both the Fe
doped ingots compared to the reference ingots. At the bottom and at the top of the Fe doped ingots
the density of the crystal defects is enhanced, both in comparison to about 70% height within the
same ingots and in comparison to the reference ingots. This is reflected in the solar cell efficiencies,
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which are reduced in the bottom and top, but are comparable to the reference at around 70% height.
The increasing defect concentration in the top of the Fe doped ingots may be related to the
increasing iron concentration in the melt. In the bottom, the initial high concentration of Fe in the
silicon melt may have originated a transient nucleation and growth disturbance during the early
solidification phase. However, these effects may be particular for the very heavy contamination (50
ppmw) introduced in these experiments
Efficiency variation
Mihailetchi et al. [13] experimentally investigated the correlation between resistivity and
solar cell efficiency on n-type mc-Si wafers. Two multi-crystalline n-type ingots grown in the same
furnace have been selected for this investigation: a compensated ingot (called ingot 5) which is
partially p-type (boron dominates over antimony) and partially n-type (antimony dominates
over boron) doped. Solar cells have been fabricated on 156.25Cm2 wafers distributed to cover a
resistivity range of0.8 to 7.7 Ωcm from the first ingot and 0.3 to 2.2 Ωcm from the second ingot.he
measured JscxVoc product increases with resistivity for cells made from ingot 6 while it stays rather
constant for cells of ingot 5 for resistivity larger than 1.3 Ωcm. These results suggest that the
optimum base resistivity for n-type multi-crystalline Si feedstock lies between 1.5 to 4Ωcm.
However, recent results in our group for an ingot of higher resistivity (described in the next
paragraphs), indicate that this result is probably dependent on ingot growth conditions, and not
universally valid. From lifetime data resulting from fitting internal quantum efficiency data (IQE),
in ref. [13] it is observed that a resistivity higher than approximately 1.3 Ωcm is required in order
to ensure that bulk diffusion length is higher than the average wafer thickness for both ingots.
The lifetime as a function of resistivity also shows, for low resistivity, a linear dependence,
suggesting activity of some impurity which is relatively harmful in n-type base (e. g. Au, Zn,
perhaps Cr).
A similar study on n-type mc-Si wafers from the Dai-Ichi Kiden company has been also
carried out in our group. The results show an increase of efficiency with resistivity, even up
to a resistivity higher than 7 Ωcm. The JocxVoc trend is actually similar to the trend described by
Mihailetchi et al. [13] but shifted to higher resistivity. The reason for the difference in efficiency
variation as a function of the resistivity is still under investigation, and could be due to different
defects in the various ingots.
Process
The n-type mc-Si material characteristics described in the previous sections offer
perspective for fabrication of high efficiency commercial solar cells. The main challenge resides
in the designing of an adapted fabrication process. One of the major development areas of the n-
type mc-Si solar cell process remains the passivation of the front side boron emitter. Since the
conventional way to passivate phosphorus emitters for the p-type solar cell process, using a
PECVD-SiNx layer, results in a poor or no passivation for boron emitters, a new way of
passivating boron doped surfaces needs to be developed. Mihailetchi et al. [13] have developed a
new method to passivate boron emitters which brought new potential to the n-type
multicrysatlline silicon industrial solar cell process. This new method relies on the same
PECVD SiNx technology, as is widely used in industry to passivate phosphorus emitters,
and is industrially applicable with no substantial increase in cost or process time.
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This method employs an ultrathin silicon oxide between the emitter and the SiNx. An
almost 6-fold enhancement in the lifetime and 60 mV higher implied Voc is observed for
lifetime test devices after firing. These values outperform even the results obtained using
thermal SiO2/PECVD SiNx stacked layers as a passivation method. Since the method employs a
low-temperature oxidation process, possible deterioration of, e.g., the base material, is minimized.
Our simplified cell process protocol is illustrated in figure 2 and a structure of the fabricated
n-type cells is presented in figure 3. The rear-side metallization has an open structure that
can enhance the internal reflection, as well as increase the annual energy yield by employing
bifacial modules. The cell process led to efficiencies of 16.7% on multi-crystalline and 18.5%
on monocrystalline wafers of 125mm size (independently confirmed by ISE CalLab) [14]
Wafer texturing and cleaning
Emitter & BSF diffusion
Wet chemical process and
SiNx coating (both sides)
Screen printing metal paste
Firing through
Figure 2 - Major process steps for making industrial screen printed n-type solar cells.
Figure 3 - Schematic cross-section of the n-type solar cell.
In the context of the European FOXY project, modules were made of n-type mc-Si solar
cells - made from Deutsche Solar wafers by ECN using the process described above – and were
assembled and tested by Isofotón. After 3 months of outdoor exposure, no signs of degradation have
been observed. Also, on separate (mini-)modules, damp heat and thermal cycling tests were carried
out at ECN and have shown a fill factor degradation of less than 2%. Recently, Naber et al. [14]
demonstrated that an alternative wet chemical process for creating the SiO2 passivation layer
facilitates a further enhancement of the Voc by 4 to 5 mV. The Voc has (on Cz of 1 Ωcm) an
average value of 634 mV and a peak value of 639 mV.
New passivation methods for boron emitter are under development to utilise the full
potential of n- type solar cells. New technology involving negatively charged dielectric layers
such as Al2O3 are under investigation. Benick et al. [15] have proven the excellent surface
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passivation of Al2O3 deposited by Atomic layer deposition technique (ALD) on cell level
based on float zone Si substrates. They reported very high IQE values of ~100% in the 300–
600 nm range demonstrating the excellent front surface passivation on B-doped emitters provided
by Al2O3. Atomic layer deposited Al2O3 may therefore also offer excellent passivation for n-type
mc-Si wafers.
CONCLUSION
The results presented in this paper confirm that n-type multi-crystalline silicon offers a
significant opportunity for commercial high-efficiency silicon solar cells. From a feedstock point of
view, n-type mc-Si material exhibits an excellent tolerance to a large number of impurities and it
has been reported that the effect of interactions between impurities and extended defects can be
strongly reduced compared to p-type mc-Si material. In consequence, compared to p-type, n-type
mc-Si has high minority carrier lifetime and competitive minority carrier diffusion length suggesting
that this n-type mc-Si is better suited for high efficiency commercial silicon solar cells. Simple and
cost effective concepts for solar cell manufacturing based on n-type mc-Si wafers are in
development and already led to record efficiency of 16.7% on large area multi-crystalline wafers.
One of the key process steps to reach such high efficiencies is the boron emitter passivation
Photovoltaics constitute a new form of producing electric energy that is environmentally
clean and very modular. In stand-alone installations, it must use storage or another type of generator
to provide electricity when the sun is not shining which currently outperforms the best passivation
obtained for the conventional n-type emitter on p- type wafers (Joe=23 fA/cm2 for p-type emitters
vs. Joe200 fA/cm2 for n-type emitters).
REFERENCES
[1] Andres Cuevas, Mark J. Kerr et al. pl. Physics Letters, vol.81,n°26, 2002
[2] Martinuzzi et al. J. Appl. Phys. 32, 187-192, 2005
[3] A.A. Istratov, H. Hielsmair, E.W WeberAppl. Phys. A 69, 13 (1999)
[4] Macdonald et al. IEEE - New Orleans, 2002
[5] J. Libal, L.J Geerligs et al. Photovoltaic Specialists Conference, 2005
[6] Macdonald & GeerligsAppl. Physics Letters, vol. 85, n°18, 2004
[7] Coletti, Kvande et al.J. Appl. Phys., 104, 104913, 2008.
[8] Schmidt et al.J. Appl. Phys 102, 123701, 2007
[9] Cotter et al. IEEE, vol. 53, n°8, 2006
[10] Geerligs et al.J. Appl. Phys 102, 093702, 2007
[11] K.D. Schmidt et al. Bell Syst. Tech., 1963
[12] Macdonald et al.Appl. Physics Letters 88, 092105, 2006
[13] V.D. Mihailetchi et al. IEEE, 2008
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
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Unique Interfacing System For Multiple Sensor Data Acquisition And Control System Using
Virtual Instrumentation
A. P. Bhat1, N.V. Shiwarkar
2 S. J. Dhoble
3, K. G. Rewatkar
4
1Depatrment of Electronics, RTM Nagpur university Nagpur-440033 India. 2Department of Electronics, Dr. Ambedkar College, Nagpur-440010 India.
3Department of Physics RTM Nagpur University, Nagpur- 440033 India 2Department of Physics, Dr. Ambedkar college, Nagpur-440010 India.
[email protected], [email protected]
ABSTRACT
Data acquisition and control system consists of analog to digital converter (ADC), digital to
analog converter (DAC), timer, counter, pulse generator, digital input / output (DIO) depending
upon requirement. All the system components must communicate with personal computer (PC) for
data and control signal transmission via one of the communication protocol like Serial, Parallel,
USB, GPIB. Serial communication is advantageous over other protocol due to several reasons, like
long distance transmission, less number of physical connection, ease of implementation etc. The
system is developed Serial Multiple based Data Acquisition and Control System, which can control
different modules like temperatures pressure and vibration,, the interfacing card is designed using
single serial port and A Lab VIEW based program is developed for the individual communication
of each module.
Keywords: ADC, Digital system, communication methods, multiple data sensor, lab view, Virtual
instrumentation
INTRODUCTION
In the resent year numerous developments in VLSI give new era to the development of
microcontroller based system call as smart system. This development is being coupled with
numerous applications and continued with development changes compared with traditional
philosophy of data acquisition. Traditional scheme based on simple ADC interface have been
replaced in many situation where there is the need to collect information faster than a human, data
loggers can possibly collect the information and in cases where accuracy is essential. A data logger
is a device that can be used to store and retrieve the data [1]. Data logging also implies the control
of how sensor collects analyzes and store the data. It is commonly used in scientific experiments.
Data loggers automatically make a record of the readings of the instruments located at different
places. The user determines the type of information recorded. Their advantage is that they can
operate independently of a computer. The range includes simple economical single channel multi
sensor and function loggers to more powerful programmable devices capable of handling hundreds
of input [2].
The basic data acquisition and control system consists if different types of application module
like temperatures pressure and vibration etc. The module is selected depending upon the
requirement. The modules are individually controlled with personal computer (PC) for data and
control signal transmission using one of the communication protocol. If communication is done
using different protocol for different modules in system requires knowledge of different
communication protocols, communication hardware and large number of connection with the PC. In
order to overcome the above mentioned difficulties, we developed Serial Multiplexed based Data
Acquisition and Control System (SMDACS). In house developed system consists of different
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
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application modules and a controller module. The application modules are controlled by controller
module having serial connectivity. The control program for each application module is developed in
Lab-VIEW environment.
RELEVANT THEORY
The task of data acquisition and logging is unique in the predefined environment is behind less
complicated system but if we defined the task of remote data acquisition with the developing
technology then the task is become complicated. The problem is resolve using microcontroller
interfacing method with the wireless communicable environment such as RF environment. This
wireless communication helps to acquire the data from the remote place and received data is show
on display device or with some extra development interface with the personal computer (PC). The
primary goal of this work is to design an digital system using AVR Atmega-16 Microcontroller
Family with their communication feature (Rx, Tx) with the RF communication module (cc2205)
communication protocol. The prototype work is to use data logging for temperature, pressure
vibration and humidity measurements. In order to meet the above requirements, a low cost,
versatile, portable data logger is designed. The temperature, pressure and Vibration acquiring is
designed using microcontroller At mega 8 and At-Mega 16. A particular value of temperature
pressure and Vibration is acquired by At mega 8 designed unit which work as slave and it send to
main controller board designed using Atmega-16 work as master control, which connected with the
PC at the data collection centre
EXPERIMENTAL WORK
A block diagram shown in Fig. 1. Consists of different application modules which are
installed on back panel of card developed using ATMega- 16 microcontroller of the system. The
physical address for the application module is set on mother board from 000 to 111. When system is
switched ON, the application module read the physical address and saves in local register of
microcontroller. While transferring command for Read / Write, the logical address is sent first with
the interrupt status value. The microcontroller in application module compares logical address and
physical address. The module program command sequence is executed in the application module
whose logical address and physical address matches. All the commands are treated as either read or
write considering as receive or send by PC. Data and commands are sending or receive by the PC to
the application module via serial interface. The application module can be installed in one to eight
locations while controller is placed on ninth position. The application module has no physical
position limitation, i.e., any module can be installed in any position except the controller module.
Figure 1: Block diagram of developed system
Temp
Lab-
View
RS 232
Interface
Controller ATMega- 16
Humidit
y
Vibratio
n
Pressur
e
LCD
DISPLAY
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
65
Figure 2: shows the developed SMDACS assembly.
The assembly consists of 3U size, nine slot chassis. The chassis as controller module, application
module, back panel and in-built power supply. The right-most module is the controller module.
Each application module communicates with the controller module using back panel 9 pin D-type
for transmit, receive and power. Three pins of the 9-pin D-type connector are used for physical
address of the module. The application module is used physical address for data and control
information transmission. Each application module consists of logic gates, microcontroller
(ATMega 16) and other related electronics and communicable components.
Controller Module
Controller module is the heart of the system. It is the interface module which transmits data
and control signals between PC and application module. Front panel of the module has power
indicator and a data transmission receiver indicator. It has an internal trigger though the INT1 which
is used as bus trigger for the entire application power status check module simultaneously. A 9 pin
D-type connector is used for communication using serial bus .A 9 pin serial connector on the back
panel of this module is used to transmit and receive data or control signal.
Figure 2: Developed serial multiplexed based data acquisition and control system hardware.
The system uses two types of programs for its operation namely system program and module
program. PC System program Lab VIEW as Graphical User Interface (GUI) which is used by users
DAQ REMOTE
MODULE RF
MODULE
Controller kit RS232 MODULE
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
66
while the Module program is the program written in the embedded c programming structured
microcontroller of the application module. The Lab VIEW GUI program controls the operation of
system as shown in the Fig 3. While executing the Lab VIEW GUI program, the following sequence
is followed:
Configure serial port by VISA resource name.
Select Station ID (logical address) and other related parameters which are to be passed to the
different application modules.
Activate required Station ID for passing the parameters (All or specific station).
Select appropriate command (Write or Read) The program can stop forcefully by Stop command.
Application Module
The Module program is written inside the microcontroller [1] of the individual application
module. When power is switched ON, the microcontroller inside individual module will read
physical address from the back panel and write it in the local memory μC. Figure 4 shows the flow
diagram of module program. The Lab VIEW program sends the logical address to application
module through serial communication. The logical address send by the Lab VIEW program and
physical address written in microcontroller memory is compared. If the match in address is found,
next commands end by the Lab VIEW program will be executed on that particular module.
Depending upon the command send by the Lab VIEW program, data / control word will be read
/write in particular application module using the serial interrupt. All the other interrupts are disabled
whenever application module places data on the serial bus.
Figure 4: Flow diagram for module program.
START
Initialization
Convert data into string
Send data to Lab View
System initiation cycle –INT1
Configure serial port
Status check for power supply
Acquire a data from system
Is status
is ok?
STOP
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
67
Digital I/O Module
The DIO module consists of eight digital inputs and eight digital outputs. This module is
developed using inbuilt ADC of the microcontroller. The ATMega series microcontroller ic have
10 bit ADC, the module read the digital input and displays the status of each bit on the Lab-VIEW
GUI. The different digital pattern is generated by setting the bit pattern in the GUI. The GUI
transfers the digital pattern to the digital output port. Here we used the serial RS-232 port separately
for communication between microcontroller and Lab View GUI.
Digitizer Module
The diagram of the developed 10bit digitizer module using ADC. The module is initialized
by the number of sample to read and the mode of trigger. The ADC module continuously read the
required number of samples after getting start trigger and system status check. The start trigger of
the module is selected using software or external hardware trigger by GUI. The developed module
has maximum storage capacity of about 64 KB. After getting the trigger, the microcontroller read
the digital data from ADC and writes the required number of sample in the memory. When module
is selected for reading the data, it will transfer data from the module memory to PC via serial bus.
The data for the “number of data bytes to be read” is written by Lab VIEW program. The lab view
coding is orange in such way that the data format is separated with the specified formatted string
separator defined in microcontroller coding. It will write the data in defined file format. User can
define a file name or append to a file. The stored data can be retrieved and analyzed as per
requirement using Origin or MATLAB software.
Communication module
The communication between the lab view coding and the microcontroller is defied with the
predefined baud rate of 9600baud. The RS232 module is configured using max 232 as TTL to
Digital logic convertor. The microcontroller sends the string of fixed length defined while
programming and lab View (VISA) port is configure with the same data rate. Serial port activation
is carryout through the VISA Read operation tool available in lab View. The received string is
display in specific string constant format with the string separator.
RESULT
The data capture by the microcontroller ATMega 16 is converted into string format using the
standard library function and send through the serial port which is already defined in the code
wizard. Figure 6 shows the snap shot of the serial port data , the independent line shows the string
data printed on hyper terminal, the same data is received in the designed lab view panel. The lab
view and microcontroller is configured with the tool VISA available in library. The received string
is stored at location and same string is used with string splitter tool with the common separator
symbol. The separate logic of string to numeric converter the string data is converted into the
numeric floating point data.
The data acquired by the microcontroller is shown on the LCD display attached with the
microcontroller-developed board.
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
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Figure 5: hyper terminal data output by microcontroller
CONCLUSION
The developed SMDACS is stand alone and used in small experiment. The designed
system is compact, stand-alone, reliable, accurate and portable with on-board display of the
acquired the data from remote place or system under observation. The properly designed Data
Acquisition system saves time and money by eliminating the need of service personal to visit each
site for inspection, data collection logging or make adjustments.
The system can be used for acquiring slower sampling data for longer duration using
digitizer module. Other than this the module generates different timing pulses using TTL delay
generator to synchronize with other system. The system also generate digital pattern or to acquire
system status using digital input / output module. The analog signals generated using digital to
analog converter is used for analog pattern generation.
ACKNOWLEDGMENT
The author will thank to the National Instrument (India) Ltd. for providing the real time data
analysis tool and software support.
REFERENCES
[1] Muhammad Ali Mazidi and Janice Gillispie Mazid i, “The 8051 Micro controller and embedded
system using assembly and C”, second edition printice hall of India Pvt. Ltd .2005 PPP250, 267, 84
[2]Ayala K.J “The 8051 Microcontroller Architecture programming and Application penram
publication International ( India) Second Edition 1996.ppp.54,59,68
[3]Hall D.V, “Microprocessor and interfacing programming Hardware”, Tata Mc Grow-Hill
Edition,1991, seventh Reprint 1995.P344
[4]Johnson C.D, “The process control Instrumentation Technology ’’ Prentice-Hall (India) seventh
edition, August-2002.
[5] A. J. Thompson, J. L. Bahr and N. R Thomson, Low power data logger, proceedings of
conference department of physics, university of Otego, Dunedin2012
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
69
A Review Paper On Magnetic Nanoparticles Ferrites Used In Biological Applications
P. K. Tembhurne, K. G. Rewatkar, S. J. Dhoble
Dr. Ambedkar College, Department of physics, Nagpur-10 India
Department of physics, University campus, Nagpur -33, India
ABSTRACT:
Nanocrystalline ferrites are the subject of interest because of its wide application in industrial and
research area. But at present it had improved a lot curiosity in the case of nano bio-applications.
Nanoparticles have many magnetic, electrical properties which used to diagnosis the disease from
our body. This paper explains in details about biomedical application such as target drug delivery,
tumour, cancer diagnosis and magnetic resonance imaging contrasting agent etc. New developed
material are characterised with magnetic behaviour used in biomedicine application characterized
by XRD, SEM, TEM, VSM, which is useful for medical applications.
Keywords: Ferrites, biological application, XRD, SEM, TEM, VSM
INTRODUCTION
Ferrites are the ferromagnetic materials which possess the combined properties of magnetic
conductor and electrical insulator. They have been extensively investigated and being a subject of
great interest because of their importance in much technological application such as antenna rod,
transformer cores, magnetic data storage etc [1]. These electrical and magnetic properties are
affected by the type of substituent, microstructure, chemical composition and method of preparation
[2,3].
In the recent year, nanosized spinel ferrites particles received a considerable attention because
of their interesting magneting properties in biomedical application [4, 5]. It is found that when
particle diameter reduce to nanometre dimension spinel ferrite particles may exhibit super
paramagnetic behaviour, which is of great interest from the point of view of their application. The
earliest known biomedical use of naturally occurring magnetic materials involves magnetite (Fe3O4)
or lodestone which was used by the Indian surgeon Sucruta around 2,600 years ago. Current areas in
medicine to which magnetic biomaterials can be applied include molecular and cell biology,
cardiology, Neurosurgery, oncology and radiology.
We begin with a discussion of the application of magnetic biomaterials. Magnetic
nanoparticles can be applied to cell separation, magnetic resonance imaging (MRI), drug and gene
delivery, radionuclide therapy, and hyperthermia [6]. Physical properties of magnetic materials
attractive for biomedical applications because they can be control by an external magnetic field.
This is useful for separation and drug targeting. And hysteresis and other losses occur in alternating
magnetic fields are useful in hyperthermia application.
1] Drug Delivery
It is known that, chemotherapy is not always effective. In chemotherapy injected drug affect the
other than that body part where it is not required.
In the case of targeted drug delivery, the magnetic particle first acts as a carrier of the drug
which is coated. Once the drug coated particles have been introduced into the bloodstream of the
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
70
patient, a magnetic field gradient, created, e.g., by a external Strong permanent magnet is used to
“hold” the particles at the targeted region.
2] Hyperthermia
Hyperthermia is a type of cancer treatment in which body tissue is exposed to high
temperatures, using external and internal heating devices. Hyperthermia is almost always used with
other forms of cancer therapy such as radiation and chemotherapy
In the case of magnetic hyperthermia applications, a different principle is involved; we wish to
raise the temperature to about 43oC in a localized area in order to destroy cancer cells selectively.
This can be done by applying a magnetic field which varies with time; ferro- and ferri-magnetic
material will be repeatedly cycled through the B-H loop, resulting in hysteresis and other losses
which are then converted to thermal energy and result in an increase in temperature. Super
paramagnetic materials can also be heated using this technique.
3] Magnetic Resonance Imaging (MRI)
MRI (Magnetic Resonance Imaging) scanning is a medical investigation that uses an exceptionally
strong magnet and radio frequency waves to generate image of our body.
So far, we have only considered magnetic properties associated with the electrons in the
material. However, protons also have a magnetic moment, and this can be utilized in the powerful
imaging technique of magnetic resonance imaging (MRI). An MRI scan is one of the most
sophisticated diagnostic tools available to help a referring clinician understand the cause of our
particular health issue.
The phenomenon of magnetic biomaterials can also be applied to a no. Of biomedical application
like radionuclide delivery, cell separation, isolation of biologically active compound, modification
and for detection any diseases.
CHARACTERISTIC
Iron containing transition metal oxide phases have been the subject of extensive investigation.
These magnetic nanoparticles ferrites can be obtained in three different crystal systems like cubic
crystal structure (MFe2O4), hexagonal crystal structure (MFe12O19), and Garnet (R3Fe5O12). Magnetic
materials in the form of nanoparticles, mainly magnetite (Fe3O4), are present in various living
Organisms and can be used in a number of applications. Magnetic nanoparticles can, of course, be
prepared in the laboratory by means of the well-known methods; as sol-gel [7], hydrothermal,
reverse micelle synthesis [8], co-precipitation method [9], and ball milling technique [10].
1] XRD
The crystal structure of the materials was determined with X-ray diffraction (XRD) carried out on a
Bruker- AXS D8 Advanced diffracto meter with Cu Kα radiation in the 2θ range.
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
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Fig.1 shows the x-rd pattern of spinel ferrites.
The X-ray diffraction patterns of the synthesized ferrite nanocrystals have been shown in Fig. The
peaks in XRD patterns illustrate the characteristic peaks of single phase cubic spinel structure. Peak
intensity is indicative of high degree of crystallinity of prepared ferrites. The existence of the (220),
(311), (222), (400), (422), (511) and (440) major lattice planes in the XRD patterns confirms the
formation of spinel cubic structure with the Fd3m space group, which is consistent with the powder
diffraction file of JCPDS [11].
EDAX (energy dispersive analysis of x-ray) analysis is generally carried out to test the purity
of the sample by giving us the details of all the elements present in the given sample.
2] VSM (vibrating sample magnetometer)
Magnetic characterization of the samples was carried out by vibrating sample magnetometer at
room temperature with a maximum applied field.
The obtained M-H curves show coercivity (Hc), remanence (Mr) and saturation magnetization
(Ms) which indicates the property of the samples shown in fig.2]. The absence of saturation,
remanent magnetization, and coercivity in the M–H curves indicate the super paramagnetic nature
of the particles. The non-saturation of the magnetization even at the highest applied field also
implies the presence of the single domain nanoparticles in the super paramagnetic state. The
coercivity of sample dependence on mean particle dimensions in the range of 9-40nm.The expected
particle size for biomedical application should not be greater than above mentioned size.
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
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3] SEM and TEM
Morphology of the prepared samples was studied using scanning electron microscope (SEM) where
the secondary electron images were taken at different magnifications to study the morphology. The
scanning electron microscopic image of synthesized sample shown in fig. SEM micrographs show
that the grains have almost homogeneous distribution with spherical shape and agglomeration
between the particles.
Fig.3 shows the SEM image of ferrite
From the TEM image we can find the exact particle size with no agglomeration and also conform
the morphological structure.
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
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Fig.4 shows the TEM image of ferrite
DISCLOSURE:
Magnetic nanoparticle can be synthesized by many methods. It is used in medical application to
cure the dieses like drug delivery, MRI, hyperthermia etc. And synthesized sample characterized by
the XRD, VSM, SEM and TEM.
REFERENCE
[1] S.Muralidharan, V.Saraswathy, L.J.Berchmans, K.Thangavel, K.Y. Ann, 2010. Sensors
Actuators, B: Chemical, 145: 225-231.
[2] A.M.Samy, H.M.EI-Sayed, A.A.Sattar, J. Phys. Stat. Sol. (a) 200 (2) (2003) 401.
[3] S.Yan, Li Dong, Z.Chen, X.Wang, Z.Feng, J. Magn. Magn. Mater. 353 (2014) 47-50.
[4]. Colombo, M.; Carregal-Romero, S.; Casula, M.F.; Gutierez, L.; Morales, M.P.; Bohm, I.B.;
Heverhagen, J.T.; Prosperi, D.; Parak, W.J. Biological applications of magnetic nanoparticles.Chem.
Soc. Rev. 2012, 41, 4306–4334.
[5]. Singamaneni, S.; Bliznyuk, V.N.; Binek, C.; Tsymbal, E.Y. Magnetic nanoparticles: Recent
advances in synthesis, self-assembly and applications. J. Mater. Chem. 2011, 21, 16819–16845.
[6]. K. Raj, R. Moskowitz and R. Casciari, “Advances in Ferrofluid technology,” Journal of
Magnetism and Magnetic Materials, Vol. 149, No. 1-2, 1995, pp. 174-180.
[7] M. George, A. M. John, S. S. Nair, P. A. Joy and M. R.Anantharaman, “Finite Size Effects on
the Structural and Magnetic Properties of Sol-Gel Synthesized Powders,” Journal of Magnetism and
Magnetic Materials,
[8] Pileni, M.P., Lisiecki, I. (1993), Nanometre metallic copper particle synthesis in reverse
micelles.80, 63-68.
[9]H. Gul, W. Ahmed and A. Maqsood, “Electrical and Magnetic Characterization of
nanocrystalline Ni-Zn Fer-rite Synthesis by Co-Precipitation Route,” Journal of Magnetism and
Magnetic Materials, Vol. 320, No. 3-4, 2008, pp. 270-275. doi:10.1016/j.jmmm.2007.05.032
[10] Corrias Ennas, G., Musinu, A., Paschina, G., Zedda, D. (1997), Iron-Silica and Nickel-Silica
Nanocomposites Prepared by High Energy Ball Milling. J. Mater. Res, 2767, 12.
[11] H. P. Klug and L. E. Alexender, “X-Ray Diffraction Procedures for Polycrystalline and
Amorphous Materials, “Chapter 9, 2nd Edition, Wiley, 1974.
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
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Microstructure and Magnetic Studies Of Zinc Ferrite Nano- Particles With Cobalt
Doping For High Frequency Microwave Absorber
S. T. Chattrejeeb, A. P. Bhat
a, R.M.Shingh
b, P.M. Bodele
b, S. J. Dhoble
c, K. G. Rewatkar
b
aDepartment of Electronics, RTM Nagpur university, Nagpur -33, India bDepartment of Physics, Dr. Anbedkar college,Deekshbhoomi, Nagpur -10, India
cDepartment of Physics, RTM Nagpur university, Nagpur -33, India
Corresponding author: [email protected]
ABSTRACT
In zinc ferrite, the Co Zn2+ and Fe ions are distributed over the A and B sites and therefore the
formula is represented as (Zn1dFed)[ZndFe1+d]O4,where the part between the round brackets
represent the atoms at the A sites, the part between square brackets the atoms at the B sites. For bulk
zinc ferrite prepared by the conventional sol gel auto combustion method, the inversion parameter,
d = 0 which is the condition for normal spinel structure. But, d can increase up to 0.22 for as-
quenched samples [2]. In contrast to the bulk compound, the nanocrystalline ZnCoFe 2O4 system
always shows up as a mixed spinel, in which the value of d is largely dependent on the synthesis
procedure. ZnCoFe2O4 nanoparticles produced with the same particle size range exhibit variation in
the invers-ionparameter values. Zinc ferrite nano-particles are synthesized by advanced
combustion route. The nano-sized Zn ferrite characterized by X-ray diffraction (XRD), Scanning
electron micrographs (SEM) and Energy dispersive X-ray (EDX) techniques. The magnetic
properties were determined by using vibrating sample magnetometer (VSM). The preparation
method investigated brought about formation of moderate crystalline ZnFe2O4 as a single phase
with irregular shape. Both the saturation magnetization (60 emu/g) and the remnant magnetization
(20 emu/g) were found to be highly depending upon the size and crystallinity of the investigated
ferrite. Our results indicate that this method might provide a promising option for synthesizing high-
quality nano-sized ZnCoFe2O4. In this study, the microwave assisted sol-Gel combustion route
was used for preparation of zinc ferrite..
Keywords: XRD; SEM, EDX; Ms, ZnFe2O4, crystalanity,
INTRODUCTION
Ferrite material has been widely used in various technical applications including in magnetic
refrigeration, detoxification of biological fluids, magnetically controlled transport of anti-cancer
drugs, magnetic resonance imaging contrast enhancement, magnetic cell separation, magnetic
devices, switching devices, recording tapes, permanent magnets, hard disc recording media, flexible
recording media, read-write heads, active components of ferrofluids, color imaging, gas-sensitive
materials and catalytic materials [1-7]. Ferrite based nano-materials show novel properties that are
often significantly different from the bulk due to fundamental changes in structural and concomitant
electronic rearrangements (induced by the reduced dimensionality) and to significant dominance of
the surface atoms. [8–10]. Among the ferrite materials, zinc ferrite that has been many
applications in various fields of industry including magnetic materials, gas sensor and
absorbent material for hot-gas desulphurization [11-14]. Recently, it was found that Zn ferrite is a
promising semiconductor photo- catalyst for various processes due to its ability to absorb visible
light, high efficiency, low cost and excellent photochemical stability. In addition, zinc ferrite shows
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
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potentially wide applications in photo induced electron transfer, photo-electrochemical cells and
photo-chemical hydrogen production [15-22]. Zinc ferrite is fabricated by numerous methods, such
as ceramic method, sol–gel, co-precipitation, ball-milling technique, hydrothermal synthesis and
thermal decomposition [23-27].
In recent years, combustion synthesis of zinc ferrite has attracted the interest of many
researchers as an energy and time-saving process [31–34, 36, 37]. In addition, this method resulted
in ceramic products have high purity, chemical homogeneity on an atomic scale, small uniform
particle sizes and controlled particle shapes. In previous our investigations, the combustion route
with different fuels have been used to synthesize undoped and Li, Mg and Al,Co doped zinc ferrites
[31-34]. These studies showed that the molar ratio of fuel and doping affect the cation distribution
between the two interstitial sites of the spinel structure with subsequent modification in different
properties of the as prepared ferrites.
The present work aims to investigate the structural, morphologically and magnetic
properties of Zn ferrite sample which prepared by using the advanced combustion method. Detailed
analyses of the structural, morphologically and magnetic properties of as prepared ferrite are
discussed. The techniques employed were XRD, SEM, EDX and VSM.
EXPERIMENTAL
Materials
Zn/Fe mixed oxide sample was prepared by mixing calculated proportions of zinc and iron
nitrates with a mixture of Urea and ammonium nitrate. The mixed precursors were concentrated in a
porcelain crucible on a hot plate at 350 o
C for 10 minutes. The crystal water was gradually
vaporized during heating and when a crucible temperature was reached, a great deal of foams
produced and spark appeared at one corner which spread through the mass, yielding a brown
voluminous and fluffy product in the container. In our experiment, the ratio of the
H4NNO3: H2NCH2COOH: Zn(NO3)2.6H2O : Fe(NO3)3.9H2O were 1: 4 : 1 : 2, respectively.
The chemicals employed in the present work were of analytical grade supplied by Prolabo
Company.
Techniques
An X-ray measurement of various mixed solids was carried out using a BRUKER D8
advance diffractometer (Germany). The patterns were run with Cu K radiation at 40 kV and 40
mA with scanning speed in 2 of 2 ° min-1
. The crystallite size of Zn-ferrite present in the
investigated solids was based on X-ray diffraction line broadening and calculated by using
Scherrer equation [38].
B
d
2cos
where d is the average crystallite size of the phase under investigation, B is the Scherrer
constant (0.89), is the wave length of X-ray beam used, is the full-with half maximum
(FWHM) of diffraction and is the Bragg's angle. Scanning electron micrographs (SEM) were
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
76
recorded on SEM-JEOL JAX-840A electron microanalyzer (Japan). The samples were dispersed in
ethanol and then treated ultrasonically in order disperse individual particles over a gold grids.
Energy dispersive X-ray (EDX) analysis was carried out on Hitachi S-800 electron
microscope with an attached kevex Delta system. The parameters were as follows: accelerating
voltage 10, 15 and 20 kV, accumulation time 100s, window width 8 μm. The surface molar
composition was determined by the Asa method, Zaf-correction, Gaussian approximation.
The magnetic properties of the investigated solids were measured at room temperature
using a vibrating sample magnetometer (VSM; 9600-1 LDJ, USA) in a maximum applied field
of 15 kOe. From the obtained hysteresis loops, the saturation magnetization (Ms), remanence
magnetization (Mr) and coercivity (Hc) were determined.
RESULTS
XRD investigation
The XRD pattern of the as synthesized solid is shown in Fig.1. This figure showed that the
as prepared sample consisted entirely of nano-crystalline ZnFe2O4 particles. Indeed, the XRD
pattern contains ten sharp lines coincide with the standard data of the cubic spinel Zn ferrite
(Franklinite) phase with the Fd3m space group (JCPDS card No. 74-2397). The peaks of the as
prepared solid indexed to the crystal plane of spinel Zn ferrite (220), (311), (222), (400), (422),
(511), (440), (620), (533) and (622), respectively. The crystallite size of this ferrite was estimated to
be about 52 nm from the X-ray peak broadening of the (311) peak using Scherrer’s equation. The
X-ray pattern of the as prepared ferrite displays sharp and well-resolved diffraction peaks with the
good crystallinity of the as prepared specimen. No additional peak of the second phase was
observed in the XRD pattern, showing that the as prepared ferrite consisted of single spinel
ZnCoFe2O4 phase.
Figure 1. XRD pattern for cubic spinel ZnFe2O4 nano-particles.
An X-ray data enable us to calculate the different structural parameters such as the
lattice constant (a), unit cell volume (V), X-ray density (Dx), the distance between the magnetic
ions (LA and LB), ionic radii (rA, rB) and bond lengths (A–O and B–O) on tetrahedral (A) sites
and octahedral (B) sites of cubic spinel structure for the produced zinc ferrite crystallites. The
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
77
calculated values of a, LA, LB , rA, rB, A–O and B–O of Mn ferrite are 0.8444, 0.3656, 0.2985,
0.0552, 0.0719, 0.1902 and 0.2069 nm, respectively. Whereas, the value of V is 0.602 nm while the
value of Dx is 5.3207 g/cm3
.
SEM measurement
SEM micrographs of as-prepared powders with different magnifications are shown in Fig.
2a-d. This figure displays the formation of spongy and fragile zinc ferrite powders. The fracture
surfaces of the aggregated powders are formed by using a mixture of glycine with ammonium
nitrate. In addition, the as synthesized sample consisted of multigrain agglomerations with small
discrete crystallites. One can see voids and pores in the samples. This observation could be
attributed to the release of large amount gases during combustion process due decomposition of
both glycine and ammonium nitrate. By comparing with my previous work, it is found that the
zinc ferrite prepared by using a mixture of urea and ammonium nitrate displays week
agglomeration.
Figure 2. SEM images for ZnFe2O4 nano-particles with different magnifications.
Energy dispersive X-ray (EDX) analysis of the as prepared specimen was carried
out at different voltages and various areas on the surface of solid. This finding shows almost
homogeneous and uniform distribution of Zn and Fe particles in the powder sample.
Magnetic properties
The saturation magnetization (MS), remanent magnetization (Mr) and the coercivity of the
as- prepared powders were determined by measuring the magnetic hysteresis loop (not given) at
room temperature. The MS value was found to be 60 emu/g and the value Mr was 20 emu/g for the
ZnFe2O4 sample. The corresponding squareness ratio (Mr/Ms) was found to be 0.333. In addition,
the coercivity of the investigated sample was found to 50 Oe. . It was found that the as-prepared
Zn ferrite particles in this work exhibited a saturation magnetization greater than that of ZnFe2O4,
prepared by glycine as fuel [32].
DISCUSSION
Spinel zinc ferrite, ZnFe2O4, based materials can be prepared via sol-Gel reaction between
ZnO and Fe2O3 [28]. The enhancement of this reaction is controlled by thermal diffusion of Zn
and Fe cations through the zinc ferrite film which covers the surfaces of grains of reacting oxides
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
78
(ZnO and Fe2O3) and acts as energy barrier. The precursor compounds, preparation method
and preparation onditions have different effects on solid state reaction between ferric and zinc
oxides to produce Zn ferrite. [40, 41].
Formation of zinc ferrite nano-particles with moderate crystallization and low
agglomeration can be achieved via the combustion route by using a mixture of glycine and
ammonium nitrate depending upon the released heat and gases during the combustion process. So,
the use of ammonium nitrate is promising route for formation of moderate crystalline zinc ferrite
nano- particles due to distribution of the energy inside the whole reacting particles reducing
the aggregation process as shown in SEM micrographs. Also, XRD measurement showed that Zn
ferrite prepared by a mixture of glycine and ammonium nitrate has crystallinity less than that
prepared by glycine only [32]
The presence of any Fe3+
ions in ZnO by diffusion would contribute to the chemically
created vacancies depending upon the ionic radii of ferric and zinc speices are 0.064 and
0.074 nm, respectively [32]. Indeed, 3Zn2+
could be replaced by 2Fe3+
and a vacancy because of
electro-neutrality restrictions. However, ZnO–Fe2O3 system shows limited solid solution of
Fe2O3 in ZnO solid. Ferric cations which appear in tetrahedral sites with the introduction of
trivalent cations into ZnO can be considered as an embryonic element or nucleus for formation
of inverse spinel in order to satisfy energy stabilization in the structure [44] .On the other hand,
Fe3+
cations have a tendency to be located in tetrahedral sites with making a strong bond with
O2−
ions in terms of electro-negativity differences and reach the lowest state of energy.
In this work, the observed super-paramagnetic behavior of Zn ferrite nano-particles could
be attributed to spin canting and surface spin disorder that occurred in these nano-particles
[45, 46]. The large value of magnetization observed in the present study shows that the
cation distribution changed from normal to mixed spinel type. Hence, the percentage of Fe3+
ions occupies the tetrahedral sites which switches on the A–B super-exchange interaction and gives
rise in the magnetization. EXAFS studies conducted by Jeyadevan et al. support the presence of
Zn2+
ion on the B-sites [48]. Liganza found that 4% of the A-sites was occupied by Fe3+
ions
[49]. The neutron diffraction study of nanocrystalline ZnFe2O4 reports that the occupancy of
Fe3+
ions at the A sites is 0.018 and 0.142 for the fine particles of diameters 16, 17, 26 and 29
nm, respectively.
CONCLUSIONS
We have Prepared ZnCoFe2O4 sample by solgel method and performed structural and
morphological study and its particle size. The crystalline size of synthesis nanocrystal was
calculated by Debye sheerer Formula the particle size in the range of 26nm. The Xray diffraction
measurement the formula of indicates the formula of single phase cubic Spinel Ferrite with the
space group Fd3M and distribution. From the SEM image it is calculated that the Material is
moderately agglomerated at low magnification.
Using a mixture of Urea and nitrate as fuel resulted in formation of Zn ferrite with
moderate crystalline cubic spinel structure, homogeneously distributed nano- particles and nano-
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
79
scale size. Higher saturation magnetization (60 emu/g) and coercivity values (50 Oe) of Zn ferrite
are obtained by using a mixture of glycine and ammonium nitrate as fuel. These values are greater
than those for nano-magnetic Zn ferrite materials prepared by using glycine only.
ACKNOWLEDGEMENT
Author would thank to UGC-DAE Consortium center Indore, for material synthesis and Scientific
discussion.
REFERENCES
1. N. M. Deraz, S. Shaban, J. Analyt. Appl. Pyrolysis, 86 (2009) 173.
2. N. M. Deraz, M. K. El- Aiashy, Suzan. A. Ali, Adsorp. Sci. Technol. 27(2009)803.
3. N.M. Deraz, S.A. Shaban, A. Alarifi, J. Saudi Chemical Society 14(2010)357.
4. Y. KÖseoglu, A. Baykal, F. Gzüak, H. Kavas, Polyhedron 28 (2009) 2887.
5. Shao-Wen Cao, , Yue-Hong Huang, J. Hazard. Mater. 171 (2009) 431.
6. Z.H. Zhou, J.M. Xue, J. Wang, H.S.O. Chan, T. Yu, Z.X. Shen, J. Appl. Phys. 91(2002) 6015.
7. Y. KÖseoglu, G.S. Alvarez, M. Toprak, M. Muhammed, Phys. Status Solidi B 242 (2005) 1712.
8. M. Tsuji, Y. Wada, T. Yamamoto, T. Sano, Y. Tamaura, J. Mater. Sci. Lett. 15 (1996)156.
9. J.W. Choung, Z. Xu, J.A. Finch, Ind. Eng. Chem. Res. 38 (1999) 4689.
10. A.J. Rondinone, A.C.S. Samia, Z.J. Zhang, J. Phys. Chem. B (2000) 7919.
.
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
80
Thermal, UV & Magnetic Studies of Complexes of Ethyl Xanthates with Co(III),
Fe(III), Ni(II) and Zn(II)
S.S. Sakhare
M.M. College of Science, Nagpur
ABSTRACT
The ethyl xanthates complexes of Co(III), Fe(III), Ni(II) have been prepared and
characterized by elemental analysis and infrared studies. The thermal studies of these complexes
have been carried out. It was observed from the TG curves that Co(III), and Fe(III) complexes
decompose without any break to oxide and sulphate respectively, as the final product whereas Ni(II)
complex decomposes directly to Nickel sulphide where as Zinc (II) complex first decomposes as
zinc sulphide followed by decomposition to zine oxide as the stable end product. Some spectral,
magetic & thermodynamic parameters, e.g. U.V., activation energy, frequency factor, xH, xS, xG
were computed from Sharp Wentworth method by using Arrhenius equation.
INTRODUCTION
Xanthate usually refers to a salt with the formula ROCS2M+ (R = alkyl; M+ = Na+,
K+(1,2))
As early as 1815 , Zeise prepared the first xanthates and analyzed some of their potassium, sodium,
barium, lead and copper salts (1). He first coined the empirical name “Xanthate” for these
compounds because of the characteristics yellow color of the copper complexes. Thermal studies
on metal xanthates have been reported[2], but very little work has been done on the determination
of magnetic properties & kinetic parameters of these complexes [3,4]. The present paper deals
with the magnetic properties, U.V., I.R., Thermal Studies & determination of kinetic parameters of
ethyl xanthate complexes of Co(III), Fe(III), Ni(II) and Zn(II).
EXPERIMENTAL
Cobalt, Iron, Nickel and Zine complexes were prepared[5] by adding aqueous solution of
metal chlorides to the aqueous solution of the potassium salt of the ligand and refluxing for one
hour when soild mass crystallized out. The product was filtered, washed several times with water
and then dried in air and stored in desiccator over fused CaCl2. The ligand ratio was kept 1:2 for
Ni(II) and Zn(II) while that in case of Co(III) and Fe(III) was 1:3. Xanthate salts are produced by
the reactions of an alcohol with sodium or potassium hydroxide and carbon disuphide (6) (7)
ROH + CS2 + KOH → ROCS2K + H2O
Xanthates bind to transition metal cations as bidentate ligands. The charge-neutral complexes are
soluble in organic solvents.[8]
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
81
Structure of typical metal tris(ethylxanthate) complex.[9] The complexes were characterized
by elemental and IR analyses. Thermogravimetic analysis was carried out in air as carrier gas using
TGS-2, Thermogravimetric Analyser with TADS computer system (Perkim-Elmer). The powder
samples were collected between 300 to 400 cieves (5 to 10 mg) and heating rate was maintained at
100C/min. UV-Visible or electronic spectra of ligands and all complexes were recorded at room
temperature in chloroform in 190 to 700 nm range by using UV-240 Shimadzu automatic
recording beam spectrophotometer.
Infrared spectra of the samples were recorded on a SPECORD-75 spectrophotometer at the
Regional Sophisticated Instrumentation Centre, (RSIC), Nagpur. Spectra were recorded by using
KBr pellets technique in the frequency range 4000-400. Magnetic susceptibility of the co-
ordination complexes were determined by Gouy’s (10, 11, 12) method at room temperature at the
Department of chemistry, Nagpur University, Nagpur.
RESULTS AND DISCUSSION
Data on physical characteristics, elemental analyses and thermogravimeric analysis of the
complexes are listed in Table 1. Table 1. Physical characteristics, elemental and TG analyses of
ethy 1 xanthate complexes of Co(III), Ni(II) and Zn(II)
Complexes
Co(OCHCS)2 5 2 3
Fe(OCHCS)2 5 2 3
Ni(OCHCS)2 5 2 3
Zn(OCHCS)2 5 2 3
Colour
Light green
Brownish yellow
Brown
White
% S
Theoretical Experimental
44.3
43.6
41.3
40.3
45.5
45.8
42.6
41.6
End product
Co O2 3
Nis
Fe(SO2 34
)
ZnO Ir Spectra Of Transition Metal Complexes With Ligand Potassium Ethyl Xanthate :
Infra-red spectra of all xanthate complexes (I.R. spectra of Fe (III) Ethyl Xanthate Fig.
3.2.25, I.R. Spectra of Zn (II) Ethyl Xanthate Fig. 3.2.29, IR Spectra of Ni (II) Ethyl Xanthate Fig.
3.2.27) Vibrational spectral Data of ethyl xanthate complex are given in table 2.
Table 2 : Vibration Spectral Data of Ethyl Xanthate Complexes of Fe (III), Co (III), Ni (II), Zn (II)
Sr. No.
Ethyl xanthate Complexes
C-O-Cin cm
-1
C-Sin cm
1-1
-C-H (streching) in cm
-1
-OH (Freestreching) in cm
-1
1.
2.
3.
4.
Fe (III)
Co (III)
Ni (II)
Zn (II)
1266
1246
1200
1273
990
1000
980
980
2987
3477
----
----
---
3450
3400
3400
C-Sin cm
2-1
1030
1040
1020
990
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
82
Infra-red spectra of all xanthate complexes shows a sharp band above 1200 cm-1 which
may be assigned to C-O-C linkage (ether) (13). A sharp band in Potassium Ethyl Xanthate
complexes of transition metal e.g., Fe (III), Co (III), Ni (II) and Zn (II) appears at 1266, 1246,
1200, 1273 cm-1 respectively which may be assigned to C-O-C linkage (ether). This also shows the
shifting of the C-O-C frequency in the xanthate complexes. Two sharp peaks near 1000 cm-1
appears in almost all xanthate complexes. Two sharp bands very close to each other in Fe (III), Co
(III), Ni (II) and Zn (II) xanthate complexes appears at (1000, 1040), (1000, 1040), (980, 1020),
(980, 990) respectively may be assigned to two different C-S frequencies.Free O-H frequencies
appears in Co (III), Ni (II), Zn (II), indicating the presence of hydrated water in the above
complexes as the bond appearing around 3400 cm-1 is broad and very weak.Shifting of the C-O-C
frequency in all xanthate complexes indicates the formation of complexes. Although there is no
direct evidence of the formation of bond between metal ions and sulfer atoms, the shifting of C-S
and C=S frequencies to lower frequencies and appeaeance of two C-S frequencies very close to each
other in all xanthate compexes as reported in the literature (14,15) supprots the formation of bond
between the sulphur atoms and metal ions.Magnetic & UV Properties of Xanthate complexes
Magnetic Data of Co (III), Fe(III), Ni(II) & Zn(II) Xanthate Complexes is given Table 3.
TABLE NO. 3 : Magnetic Data of Co (III), Fe(III), Ni(II) & Zn(II) Xanthate Complex.
Sr. No.
1
2
3
4
Complex Effective Magnetic Moment B.M.
Gram Susceptibility
Molar Susceptibility
Co(III) (Xanthate)
Fe(III) (Xanthate)
Ni(II) (Xanthate)
Zn(II) (Xanthate)
Zero
7.40
Zero
Zero
Zero
3100.00
Zero
Zero
Zero
2.83
Zero
Zero
Assignments of UV-VISIBLE absorption Bands of Co(III), Fe(III), Ni(II) & Zn(II) Xanthate
Complexes is show in table 4. UV-VISIBLE spectra of Co & Fe Complex shown in fig. 3.3.8 &
UV
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
83
Visible spectra of Ni Complex shown fig. 3.3.9 Fig. 3.3.9 U.V. spectra of Ni Xanthate complex
TABLE NO. 4 : Assignments of UV-VISIBLE absorption Bands of Co(III), Fe(III), Ni(II) & Zn(II)
Xanthate Complex
Sr. No.
1
2
3
Complex Probable StructureAbsorption Bands in nm
Assignments
Co(III) (Xanthate)
Fe(III) (Xanthate)
Ni(II) (Xanthate)
625
475
355
555
640
Octahedral
Octahedral
1A1g
1T2g
1A1g
1T2g
1A1g
1T2g
6A1g
4 4T E1g, g
1A1g
1Bg Square Panar
Fe(III) Xanthate Complex is found be magnetic in character. Cambi & co-worker (13) first
reported anomalous magnetic properties of Fe(III) complexes. Magnetic moments at room
temperature were due to equilibrium between high spin & low spin state. UV spectra of Fe(III)
Xanthate at 555 indicates Octahedral structure of complex. Magnetic study of Co(III) Xanthate
indicates Co(xanthate) is diamagnetic in nature. UV spectra at 625nm, 475nm & 355nm indicates
Octahedral structure of complex. Magnetic Study of Ni(II) Xanthate complex indicates that it is
diamagnetic in nature. UV spectra of Ni complex at 640nm indicates square planer structure of
complex. UV & Magnetic study of Zn(II) Xanthate shows that it is diamagnetic in nature. Thermal
Studies of Xanthate Complexes The TG curves of xanthate complexes of Co(III), Fe(III) and Ni(II)
between 50 to 5500C are similar in nature (Fig. 4) and expected end products are as shown in Table.
Fig. 4 Thermograms of xanthate complexes Co(III), Fe(III), Ni(III) and Zn(II)
It was observed from thermogram (Fig. 4) that the complexes of Co(III), Fe(III), Ni(II) and
Zn(II) do not contain water of hydration. Co(III) and Fe(III) complexes decompose without any
break to oxide and sulphate respectively as the final product whereas and Ni(II) complex directly
decompose to nickel sulphide. On the other hand, Zn(II) complex first decomposes directly to zine
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
84
sulphide followed by further decomposition forming zine oxide as the stable end product. Kinetic
parameters were calculated from Sharp Wentworth method by using Arrhenius equation and are
given in Table 5.
Table 5. Kinetic parameters of xanthates complexes of Co(III), Fe(III), Ni(II) and Zn(II).
Complexes
Co(Xanthate)
Fe(Xanthate)
Ni(Xanthate)
Zn(Xanthate)
Activation energy
kJ/mo1
199.7
42.1
53.2
68.9
Frequency factor
A
Sec--1
2.2 x 10
2.1 x 10
1.8 x 10
3.3 x 10
15
5
8
9
Decomposition
Temp.
453
438
473
433
Activation Energy
KJ/mole
119.683
42.1300
53.237
68.94
RT
KJ/mole
3.7662
3.6415
3.9325
3.5999
xH=E-RT
KJ/mole
-115.9213
-38.4885
-49.3045
+65.3401
xS
JK /mole-1
45.42
-146.10
-90.70
-65.80
x x
x
G= H-T
S
KJ/mole-136.4965
25.5033
-6.4034
93.8315
(Fig. 4.24 - Sharp-Wentworth Plot of Co (III) Xan, Fig. 4.25 Sharp-Wentworth Plot of Ni (II)
Xanthate Complex, Fig. 4.23 Sharp-Wentworth Plot of Fe (III) Xanthate Complex, Fig. 4.27 –
Sharp-Wentworth Plot of Zn (II) Xanthate Complex)
Frequency factor vary from 2.1 X 105 to 2.2 x 1015. Entropy changes S except
Co(Xanthate) shows negative values. This shows that during these decompostions reactions the
vibration of the activated complexes increases resulting into the loss of entropy. Positive values of
xH shows endothermic nature of decomposition process and negative values of xH shows
exothermic nature of decomposition process. Wandlant et. al (14) have reported low value of
frequency factor A as slow reactions and any other probable reason can not be given (15) Industrial
Applications The organosulpur (Xanthate) compounds are important in areas the production of
cellophane. Cellulose reacts with carbon disulfide (CS2) in presence of sodium hydroxide (NaOH)
to produces sodium cellulose xanthate, which upon neutralization with sulfuric acid (H2SO4) gives
viscose rayon or cellophane paper (Sellotape or Scotch Tape). Certain xanthate salts and
bisxanthates (e.g. Dixanthogen) are used as flotation agents in mineral processing. They are
intermediates in the Chugaev elimination process and are used to control radical polymerisation
under the RAFT process, also termed MADIX (macromolecular design via interchange of
xanthates).
ENVIRONMENTAL IMPACTS
Xanthates may be toxic to aquatic life at concentrations of less than 1 mg / L (16). Water downs
stream of mining operations is often contaminated (17)
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
85
ACKNOWLEDGEMENT
I am thankful to RSIC (Regional Sophisticated Instrumentation Center) for recording IR, thermal
data and my Guide Prof. M.N. Ray for giving valuable guidance needed for this paper
REFERENCES
[1] W.C.Zeise, Recueil de Memories del, Acad. Roy. Desscience de compenhagen, (1815)
[2] Eric Hoggarth, J. Chem. Soc., (1952) 4811.
[3] M.A. Bernard and M.M. Borell, Bull. Soc. Chim., France (1969) 3066.
[4] G.D. Ascenzo and W.W.Wendlendt, J. Thermal Analysis, 1 (1969) 423.
[5] E.E.Ried, “Organic chemistry of bivalent sulphur”, Chemical Publishing Co., New York
(1962).
[6] Roy, Kathrin-Maria (2005), "Xanthates", Ullmann's Encyclopedia of Industrial Chemistry,
Weinheim: Wiley- VCH, doi:10.1002/14356007.a28_423
[7] This report gives a detailed procedure for the potassium ethyl xanthate: Price, Charles C.; Stacy,
Gardner W. (1948). "p-Nitrophenyl sulfide". Org. Synth. 28: 82.; Coll. Vol. 3, p. 667
[8] Haiduc, I. (2004). "1,1-Dithiolato ligands". In McClevert, J. A.; Meyer, T. J. Comprehensive
Coordination Chemistry II 1. p. 349–376.
[9] Galsbøl, F.; Schäffer, C. E. (1967). "Tris (O-Ethyl Dithiocarbonato) Complexes of Tripositive
Chromium, Indium, and Cobalt". Inorg. Synth. 10: 42. doi:10.1002/9780470132418.ch6. ISBN
9780470132418.
[10]. L.H. Little G.W. Poling and J. Leja, Can J. Chem. , 39745 (1961)
[11]. M. Franzini, Z Krist, 118, 393 (1963)
[12]. T. Ikeda and H. Hogihara, Acta. Cryst., 21, 919 (1966).
[13]. L. Cambi and A. Cagasso, Att. Accad, : Naz Lincei, Ci. Sci. Fis. Mat. Nat. Rend, 13, 809
(1931); [14]. G.D. Ascenzo and W.W.Wendlendt, J. Thermal Analysis, 1 (1969) 423.
[15]. A. Mital, A.D. Kelkar and G.V. Gholap, J. Ind. Chem. Soc., 57 (1980) 517.
[16]. Besser, J.; Brumbaugh, W.; Allert, A.; Poulton, B.; Schmitt, C.; Ingersoll, C. (2009).
"Ecological impacts of lead mining on Ozark streams: toxicity of sediment and pore water".
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
86
Low Surface Leakage Current Of Bife2o3 Thin Films Deposited On Ito Substrates
By Using Pulsed Laser Deposition
A. P. Bhat, S. J. Dhoble, K. G. Rewatkar
Department of Electronics, RTM Nagpur University, Nagpur-440033 India
Department of Physics, RTM Nagpur University, Nagpur-440033 India
Department of Physics ,Dr. Ambedkar College, Deekshbhoomi Nagpur-440010India ABSTRACT Polycrystalline BiFeO3 thin films were prepared on indium-tin-oxide (ITO)-coated glass sub-
strates by using pulsed laser deposition (PLD). The X-ray diffraction (XRD) pattern showed a
polycrystalline perovskite phase and a (010) preferred orientation. A higher deposition tempera-
ture was required to crystallize for the BFO thin film on an ITO substrate compared to the BFO
thin film grown on a Pt substrate, the grain size was smaller than that of the BFO thin film on
Pt substrate, and the leakage current density was less. The optical transmittance was about 80%
around 780 nm, and the direct band gap (Eg ) was 2.72 ± 0.03 eV. The P − E hysteresis loop of
the BFO thin film on an ITO substrate was obtained at RT, and the polarization difference at
zero electric field (2Pro ), corresponding to the double remanent polarization was 140 µC/cm2 .
The M − H hysteresis loop was obtained at RT, and the antiferromagnetic behaviour was little
affected by using different substrates.
INTRODUCTION
Multiferroics are multifunctional materials that Si- multaneously exhibit some ferroic orders
such as ferro- electricity, (anti)ferromagnetism and ferroelasticity [1]. Moreover, they are
expected to be used for new type of devices such as magnetoelectric random access memo- ries
(MERAMs) by using interaction between dielectric and magnetic ordering. Although many
perovskite-type oxide materials such as BiMnO3 , TbMnO3 , and BiFeO3 (BFO) have been
studied as multiferroics, BiFeO3 has attracted more attention because of antiferromagnetic
ordering with a Neel temperature (T N ) of 643 K and ferroelectric ordering with a Curie
temperature (T C ) of 1103 K [2]. Moreover, a epitaxial BiFeO3 thin film on a SrTiO3 (001)
substrate prepared by using pulsed laser deposition (PLD) has been reported to have a high rema-
nent polarization of about 60 µC/cm2 , and a polycrys- talline BiFeO3 thin film on a Pt/TiO2
/SiO2 /Si substrate prepared by PLD shows a giant remanent polarization of over 150 µC/cm2 [3,4].
Recently, BiFeO3 with a large remanent ferroelectric polarization has been reported to show
photovoltaic effect and is expected to be applied to optoelectric devices [5,6]. Photovoltaic and
optoelectric applications of ferroelectric oxide ceramics have been explored in numerous
ferroelectric materials including BaTiO3 , and Pb(Zr,Ti)O3 [7,8], but are limited by a small
photo current density and a large band gap (∼3.5 eV) [5]. However, BiFeO3 is well known
to have a larger leak- age current due to oxygen vacancies and other defects and a lower band
gap than many other ferroelectric per- ovskite materials. Moreover, the Yang and the Choi et
al. demonstrated photovoltaic effects in epitaxial films and bulks of the BiFeO3 and obtained
low band gaps of about 2.74 eV or 2.67 eV; however, their ferroelectric hystereses were not given
due to the larger leakage current [5,6]. The optical properties of polycrystalline BiFeO3 thin
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films having a high remanent polarization deposited by using the pulsed laser deposition (PLD)
method on transparent indium tin oxide (ITO) as n-type electrode substrate can be investigated
and we expect those films to be more adequate for optoelectric applications. In this study, we
report on structural, optical, ferroelectric, and ferromagnetic properties of polycrystalline BiFeO3
thin films prepared on ITO-coated glass substrates by using PLD.
EXPERIMENTAL
BiFeO3 thin films were prepared on indium-tin-oxide (ITO, 200-nm thickness)-coated glass
substrates by using a PLD method. The fabrication of a ceramic target was started by mixing
appropriate amounts of oxide powers of Bi2 O3 (15%-excess considering highly volatile Bi) and
Fe2 O3 . The mixed powder was then calcined at 640 ◦C, followed by grinding. A disk pellet was
made by pressing the powder and sintering at 800 ◦C. The films were deposited at a
temperature around 520 ◦C and an oxygen pressure of 0.1 Torr with an ArF excimer laser (λ =
193 nm) with an energy of 130 mJ and a frequency of 5 Hz. A film thickness of 400 nm was
obtained after a 30-min deposition.
The crystalline structure of the deposited thin films was identified by using a X-ray diffraction
(XRD) analysis (Rigaku RINT 2000). The cross-sectional micrograph and surface morphology
were observed by using a scanning electron microscopy (SEM), (Hitachi, S-4800) and atomic
force microscopy (AFM), (Keyence, VN-8000). To investigate the optical properties, we
measured the transmittance by using an UV-VIS spectrometer (Varian, Cary 500). In order to
measure the electric prop- erties and the ferroelectric P − E hysteresis loop, we formed
circular Pt electrodes of 200 µm in diameter on the thin films by RF sputtering through a
shadow mask. The leakage current density versus electric field (J −E) characteristic and the
ferroelectric hysteresis loop (P − E) were measured using a semiconductor parame- ter analyzer
(Agilent, 4155C) and a ferroelectric test sys- tem (ToyoCorp, FCE-1). The magnetic hysteresis
loop was measured using a superconducting quantum interfer- ence device (SQUID)
magnetometer (Quantum Design, MPMS-5S). A magnetic field of −10 kOe to 10 kOe was applied
perpendicularly to the films plane.
RESULTS AND DISCUSSION
The crystallinity of the BiFeO3 thin films grown on ITO substrates at 470 ∼ 540 ◦C were
characterized, and the good crystallinity was obtained in the film de- posited at 520 ◦C, but the
optimum temperature for the BFO thin film deposited on a Pt/TiO2 /SiO2 /Si sub- strate is 500 ◦C.
Figures 1(a) and (b) show the XRD (θ- 2θ) diffraction patterns of BiFeO3 thin films deposited at
520 ◦C on an ITO substrate and at 500 ◦C on a Pt/TiO2 /SiO2 /Si substrate, respectively. The
XRD pat- terns of the thin films were indexed for a rhombohedral structure, and the BFO thin
film grown on a Pt sub- strate exhibited a single-phase perovskite structure with- out secondary
phases. However, the BFO thin film grown on the ITO substrate had secondary phases.
Addition- ally, if the crystallization and the electric properties of the BFO thin film on the ITO
substrate are to be improved, a little higher temperature of 520 ◦C, in com
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
88
Fig. 1. XRD (θ-2θ) diffraction patterns of BiFeO3 thin films on (a) ITO substrates and (b)
Pt/TiO2 /SiO2 /Si sub- strates. S indicates peaks attributed to the substrate.
Fig. 2. (Color online) (a) Microscopic SEM cross-sectional image of a BFO thin film on an
ITO substrate and AFM images of BFO thin films on (b) ITO and (c) Pt substrates.
parison with 500 ◦C on Pt substrate was needed. The BFO thin film grown on an ITO substrate
shows a higher 010)/(110) peak intensity ratio than the BFO thin film grown on the Pt substrate.
The reason for the (010) pre- ferred orientation of BFO thin film on the ITO substrate is not clear,
unlike the report on the BFO thin film de- posited on an ITO substrate by using a sol-gel method
[9]. Figure 2(a) shows the cross-sectional SEM image of the
Fig. 3. (Color online) Leakage current density versus elec- tric field (J − E) characteristics of
BFO thin films on Pt and ITO substrates measured at room temperature (RT).
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
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Fig. 4. (Color online) (a) Optical transmittance and (b) plot of (αE )2 versus E for BFO thin
films on ITO substrates.
BFO thin film grown on an ITO substrate, and Figs. 2(b) and 2(c) show AFM images of BFO
films on ITO and Pt substrates, respectively. The thickness of the BFO thin film grown on an
ITO substrate was about 400 nm. The grain size is smaller than that of the BFO thin film grown on
a Pt substrate, thus the (020) peak width of the BFO thin film grown on an ITO substrate
becomes broader than that of the BFO thin film grown on a Pt substrate. This result is in
agreement with the results for BFO thin films grown on Pt and ITO substrates by using the sol-
gel method [10,11].
Fig. 5. P − E hysteresis loops for BFO thin films on (a) Pt and (b) ITO substrates, measured
using a 20 kHz triangular waveform at RT.
Figure 3 shows the leakage current density versus elec- tric field (J − E) characteristics of BFO thin
films grown on Pt and ITO substrates at room temperature (RT). The J − E characteristic of the
BFO thin film on a Pt substrate is symmetric in the electric field, but that of the BFO thin film
on an ITO substrate is asymmetric as the top and the bottom electrodes are different. The
leakage current density for the BFO thin film grown on an ITO substrate is decreased compared
to that of the BFO thin film grown on a Pt substrate and the values for the Pt and the ITO
substrates at a maximum electric field of 125 kV/cm are 8 × 10−2 and 7 × 10−5 A/cm2 ,
respectively. This suggests that the film’s quality is im- proved and that interface property
between the BFO thin film and the ITO substrate are better than between BFO thin film and Pt
substrate, similar to result observed for a PZT thin film on an ITO substrate [12].
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
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Figure 4(a) shows the optical transmittance of the BFO thin film grown on an ITO substrate,
measured in the visible region by using an UV-VIS spectrometer. The transmittance of the BFO
thin film grown on an ITO substrate was about 80% around 780 nm. To deter- mine the band
gap, we plotted (αE )2 versus E for the BFO thin film, as shown in Fig. 4(b), where α and E are
the absorption coefficient and the photon energy, respec- tively. The direct band gap is 2.72 ± 0.03
eV from a lin- ear extrapolation of (αE )2 versus E plot. This value is in good agreement with those
reported by other researchers and is lower than that other ferroelectric materials such
Fig. 6. Magnetic hysteresis loops (M − H ) of BFO thin films on (a) Pt and (b) ITO substrates,
measured at 300 K. as BaTiO3 , and Pb(Zr,Ti)O3 [5,7,8,13].
Figures 5(a) and (b) show the P − E hysteresis loops for BFO thin films grown on Pt and ITO
substrates, mea- sured using a 20 kHz triangular waveform at RT. When the frequency of the
triangular waveform is smaller than 20 kHz, the P − E hysteresis is deformed due to the leak- age
current. The BFO thin film grown on a Pt substrate shows a good P − E hysteresis loop although
the leakage current is degraded a little, and the polarization differ- ence at zero electric field
(2Pro ), corresponding to the double remanent polarization is 206 µC/cm2 at a maxi- mum
electric field of 555 kV/cm. The P − E hysteresis loop is also obtained for a BFO thin film grown
on an ITO substrate, and 2Pro is 140 µC/cm2 at a maximum electric field of 1230 kV/cm. The
ferroelectric property of the BFO thin film grown on an ITO substrate in this study is much
better than that (Pr ∼ 2.0 µC/cm2 ) of the BFO thin film grown on an ITO substrate by using the
sol-gel method [9]. However, the ferroelectric prop- erty for the BFO thin film grown on an ITO
substrate is worse compared to that of the BFO thin film grown on a Pt substrate. The
degradation of the ferroelectric property is thought to be affected by the preferred ori- entation
and secondary phases while the BFO thin film grown on a Pt substrate shows random
orientation and no secondary phases. Figures 6(a) and (b) show the magnetic hysteresis loops
(M − H ) of BFO thin films grown on Pt and ITO substrates at 300 K, for a maximum magnetic
field of 10 kOe applied perpendicularly to the film’s plane. The BFO thin film grown on a Pt
substrate shows an anti- ferromagnetic behavior, similar to a previous study [14].
The BFO thin film grown on an ITO substrate shows an almost linear behavior, similar to result
observed for a BFO thin film grown on an ITO substrate by using sol- gel method [10], but the
magnetization is a little smaller than that of the film grown on Pt substrate. This in- dicates that
International Journal Of Advanced Engineering Science And Research Technology and Society for Technologically Advanced Materials of India –STAMI, India vol.1 (2016)
91
ferroelectric property of the BFO thin film grown on an ITO substrate is changed, but the
magnetic property is little affected by the substrate.
CONCLUSIONS
We prepared polycrystalline BiFeO3 thin films on ITO- coated glass substrates by using pulsed
laser deposition. The XRD pattern showed that the BFO thin film on a ITO substrate had a
polycrystalline perovskite phase with secondary phases, and a higher deposition temperature of
520 ◦C was required to crystallize the BFO thin film grown on ITO substrate, compared to the
500 ◦C for a BFO thin film grown on a Pt substrate. Moreover, the BFO thin film grown on an ITO
substrate showed a higher intensity ratio of (010)/(110), unlike the random orientation of the BFO
thin film on a Pt substrate. From SEM and AFM measurement, thickness of the BFO thin film
grown on an ITO substrate was about 400 nm, and grain size was smaller than that on a Pt
substrate. The leakage current density was lower, the optical transmittance was about 80% around
780 nm for BFO thin film on an ITO substrate, and the direct band gap was 2.72 ± 0.03 eV. The
P − E hysteresis loop of the BFO thin film on ITO substrate was obtained at RT, and the
polarization difference at zero electric field, 2Pro was 140 µC/cm2 The M − H hysteresis curve
showed a linear behavior at RT, and magnetic behavior depended little on the substrate.
ACKNOWLEDGMENTS
The one of the author would thank s to the IITB for development of material and deposition of
material and other characterization facility.
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