Microstructure and phases evolution in cobalt ferrite based

composites

Galassi Carmen

CNR - ISTEC, Faenza, Italy

www.istec.cnr.it

AGGIELAND Texas May 1-3, 2016

Electroceramics at ISTEC Multiferroic composites

• Cobalt Ferrite (CFO). Milling as a key step • Particulate ceramic composites • Laminate ceramic composites

• Phase diagram of the PZT Anomalies in the compliance, ageing, fatigue effects La doping and phases coexistence

• Polarization switching behavior and energy-storage in PLZT

Outline

AOFC 2015, March 12, Kolkata

process, study and development of piezoelectric dense or porous materials (PZT, BNT-BT, BST etc.) to cover applications being used like sensors, actuators and transducers

magneto-dielectric materials were studied for miniaturized antenna substrate

miniaturized multiferroic structures like bar-shaped piezo-ceramic rods or plates were recently produced

functional characterizations (dielectric, piezoelectric and ferroelectric characterization).

Multifunctional Electroceramics

Collaborations CNR-ISC, University Departments, contracts with Companies

a. b.

c. d.

1 mm 1 mm

a b

Prototype Hydrophone

Lighter Cheaper Powerful ultrasonic waves

Porosity graded materials

Functionally graded materials

Ultrasound diagnostics

Level sensors

PZT thick film by electrophoretic deposition

1 cm

High sensitivity High Stability

Ultrasound efficient, high-frequency transducers applications

Active vibration damping greater performance

Miniaturization/Processing technologies/Applications

Multiferroics (MF) • ferromagnetism and ferroelectricity simultaneously

• magnetoelectric multiferroics: multifunctional and smart materials • a coupling between the ferroelectric and ferromagnetic ordering allows the

direct MagnetoElectric (ME) effect (change of the polarisation P through a magnetic field H) or the converse ME effect (change of the magnetisation M through an electric field E).

(a) Venn diagram representing the overlap of physical properties in multiferroic materials

(b)Relationship between the order parameters and their mutual coupling coefficients

W. Eerenstein et Al., NATURE|Vol 442|17 August 2006 Nan C. V. et Al. Journal of Applied Physics 103, 031101 2008

Multifunctional Ceramic Materials:

Relationship between the order

parameters and their mutual

coupling coefficients

“All-in-one universal solid state element” Capable of mechanical actuation, multiple memory states, logic functions, sensing and photoactive properties with unprecedented versatility for high-tech applications. “... have the potential to fundamentally transform our society and to allow the current scientific and technological progress to continue”

Applications

• Data storage - Multiple-state logic memories - Non-volatile memories

• Wireless telecommunications - Tunable devices - Resonators - Filters - Phase shifters and delay lines - Miniaturized antennas - Terahertz emitters

• Sensors • Conversion of energies • Energy harvesting

•Miniaturization

•Greater perfomances

•Wearable applications

[] M. M. Vopson. Critical Reviews in Solid State and Materials Sciences, 40:223-250, 2015

Why

PRODUCTION OF MULTIFUCTIONAL CERAMIC composites: BULK MATERIALS AND THICK FILMS ?

“An elegant solution to single phase (multifunctional) dilemma (weak magneto-electric coupling) was the developed of (multifunctional) composite materials” [] M. M. Vopson. Critical Reviews in Solid State and Materials Sciences, 40:223-250, 2015

DESIGN AND PREPARATION IN VIEW OF MULTIFUNCTIONALITY

Newnham’s composite classification [] R.E. Newnham, et al. Cross, Mater. Res. Bull. 13, 525 (1978)

Grain Boundaries Adhesion

Pores and mechanical defects

PROCESSING RELATED ISSUES IN MICROSTRUCTURE EVOLUTION

1 to produce ME ceramic composites with 0-3 connectivity by mixing phases produced by SSM

The approach

2 to produce ME laminated ceramic structures with 2-2 connectivity by EPD

Shaping

Uniaxial pressing

Isostatic pressing

Green body

1 µm

200 nm

• Drying • Sieving

• Drying Oven

• Sieving P

OW

DE

RS

• Starting materials

• Batching

• Mixing Wet mixing Dry mixing

• Calcination

• Milling/mixing

Freeze-drying Rotary evaporator

Bulk material

Sintering

Typical preparation procedure of a bulk ceramic materials by the SSR method

← substrate

← electrode ← layer 1

← layer 2 Electrophoretic deposition (EPD) was applied to prepare magnetoelectric (ME) composite bilayer thick films based on perovskite phase and spinel cobalt ferrite

Advantages • Simple apparatus • Short formation time • Little restriction of the

shape substrate • High degree of

stoichiometry • Debonding is not required

as calcined powders

Solid state reaction Pb0.988(Zr0.52Ti0.48)0.976Nb0.024O3

Ferroelectric phase PZT Lead Zirconate Titanate

Sample ρ ε33T kp k31 d31 d33

% [10-12m/V] MO 97.7 1551 0.670 -0.380 -184 355 SD 97.9 1401 0.315 -0.166 -63 180 SG 96.4 1435 0.554 -0.299 -132 314

20 μm

SSR PZT 1200°C 2h High electromechanical coupling factor

G Montanari, AL Costa, S Albonetti, C Galassi. Nb-doped PZT material by sol-gel combustion. J. Sol-Gel Sci. Technol. 2005 36,2: 203-211

Processing of the single phases

Magnetic phase CFO Cobalt ferrite CoFe2O4

© Lou Perloff / Photo Atlas of Minerals

spinel structure

• Hard magnetic behaviour • High magnetostriction

Processing of the single phases

27 nm

21 nm

13 nm

CFO: sintering

Processing of the single phases

Processing related issues • difference in thermal expansion coefficient• lead losses

Possible solutions

• Reduction of the CFO particle size• Increasing on the dispersion and distribution of CFO aggregates• Reduction of the sintering time and temperature

PZTN CFO

Composites

Melting point

PZTN - CFO 25 - 75

PZTN - CFO 50 - 50

PZTN - CFO 75 - 25

PZTN - CFO 80 - 20

1250 °C

1200 °C

1100 °C

Melting point

64% 58%

79% 76% 82% 88%

92% 89% 90% 98%

Composites

Ferromagnetic properties were checked

Ferroelectric properties will be analysed

Magnetic-electric coupling will be analysed

Composites

These materials were used as substrate for Miniaturized Microstrip Antennas.

… The aim is to improvethe magnetodielectric properties for wearable and wireless applications in the ultrahigh frequency.

Printed antenna with diameter 31.5 mm

Bottom metallization (electrical ground)

Sintered ferrite body

AC signal

Radio wave, GHz

Metallization

•Radiation efficiency•Bandwidth

•Stored energy•Radiated power

P Galizia, C Baldisserri, C Galassi Microstructure development in novel titania-cobalt ferrite ceramic materials” Ceram. Inter. 2015

Magneto-dielectric composite materials based on TiO2/CoFe2O4system Composites

16 24

27

33

37 42 50

75 CFO (vol.%) Magnetic phase Dielectric phase

The samples were prepared by solid state reaction starting from commercial powders:

Fe2O3 Co3O4

800 °C x 4 h

Sintered in air at 1200 °C for 2 h

CoFe2O4 TiO2

P Galizia, C Baldisserri, C Galassi Microstructure development in novel titania-cobalt ferrite ceramic materials” Ceram. Inter. 2015

Composites

• XRD

vol.%

vol.%

vol.%

1

vol.% 2

vol.% 3

TO FCTO CFO CTO FO

vol.% 4

CoFe2O4

TiO2

• SEM-EDXS • Image analysis

P Galizia, C Baldisserri, C Galassi Microstructure development in novel titania-cobalt ferrite ceramic materials” Ceram. Inter. 2015

Composites

CFO TO wt.% CFO

Achievement of new electromagnetic properties tailoring magnetic and

dielectric phases Functional properties will be analysed

Sample Density (g/cm3) Relative Porosity (vol.%)

µr (1 GHz)

Tanδ (1 GHz)

CFT57 4.305 6 1.20 0.04 CFT80 4.855 6 1.22 0.08

P Galizia, C Baldisserri, C Galassi Microstructure development in novel titania-cobalt ferrite ceramic materials” Ceram. Inter. 2015

Composites

Pt-c

over

ed A

l 2O3

1° EPD

2° EPD

Pt-c

over

ed A

l 2O3

CoFe

2O4

• Pt-covered Al2O3

• CoFe2O4

• Pb0.988(Zr0.52Ti0.48)0.976Nb0.024O3

• Pt

Magnetoelectric composite bilayer films by electrophoretic deposition

Composites

Magnetic and Electric Characterization

Magnetic-electric coupling will be analysed

Ferromagnetic properties were checked

Ferroelectric properties will be analysed

Composites

[] P Galizia, et al. J. Eur. Cer. Soc. 2016; 36, 2: 373–380.

1° layer: Co-deposition of titanium oxide and cobalt ferrite nanoparticles 2° layer: deposition of Nb-doped lead titanate zirconate

102 103 104 105 106

100

150

200

250

300 47/AlO/CFT82/PZTN

ε'

Frequency (Hz)

I II III

102 103 104 105 1060,0

0,2

0,4

0,6

0,8

1,0

1,2 47/AlO/CFT82/PZTN

I II III

tan

δ

Frequency (Hz)

M E

Multifunctional device

DESIGN AND PREPARATION IN VIEW OF MULTIFUNCTIONALITY

Composites

[] P Galizia, et al. “Bilayer thick structures based on CoFe2O4/TiO2 composite and niobium-doped PZT obtained by electrophoretic deposition” J. Eur. Cer. Soc. 2016; 36, 2: 373–380.

PZTN

Ag

Al2O3

CoFe2O4 TiO2

TiO2 (Rutile) CoFe2O4 TiO2 (Anatase)

Ag

Si PZTN

(1 1

1)

CFO/TO: 98% relative density; 25vol% TiO2; 75vol% CFO PZTN: 95% relative density

Composites

Summarizing activity on multiferroics

1. The “Influence of milling and calcination temperature on the microstructure of cobalt ferrite” was studied.

2. Bulk particulate Nb-doped PZT - cobalt ferrite ceramic composites have been developed. Functional characterization is still in progress.

3. Novel in-situ particulate composites were produced by combining cobalt ferrite and titanium dioxide. Microstructure development depends on starting composition

4. Electrophoretic deposition was used to produce multifunctional thick films:

• “Bilayer thick structures based on CoFe2O4/TiO2 composite and niobium-doped PZT obtained by electrophoretic deposition” were produced. • processing of PZTN-CFO thick films successful

Anelastic and dielectric spectra of PZT - 6-20% Ti

the elastic compliance is equally sensitive to polar and non-polar modes

excellent tool for studying AFD modes

the dielectric susceptibility is extremely sensitive to the polar instabilities, which mask the other ones

Revised PZT phase diagram

Cordero, Craciun, Trequattrini, Galassi (anelastic, dielectric) JPCM 23, 415901 (2011); PRB 87, 094108 (2013); Phase Transit. 87, 255 (2014)

a -a -c 0 ≡ in-phase tilts about (110)

orthorhombic AFE Pbam

Pb (1-10) with

( )11041=q

tilted R-FE R3c = R3m + a -a -a - anti-phase tilts about (111)

rhombohedral FE R3m Zr,Ti and Pb (111)

FE

AF

OT RT

PZT phase diagram near the AFE/FE MPB

Cordero, Craciun, Trequattrini, Galassi (anelastic, dielectric) JPCM 23, 415901 (2011); PRB 87, 094108 (2013); Phase Transit. 87, 255 (2014)

a -a -c 0 ≡ in-phase tilts about (110)

orthorhombic AFE Pbam

Pb (1-10) with

( )11041=q

tilted R-FE R3c = R3m + a -a -a - anti-phase tilts about (111)

rhombohedral FE R3m Zr,Ti and Pb (111)

FE

AF

OT RT

the AFE thermal hysteresis depends on the sample history and cooling rate

the AF and OT modes may occur nearly independently of each other with different kinetics

Identifying the anomalies in the compliance

TT

TT : tilt R3c ↔ R3m a -a -a - ↔ a *a *a * T

T

dielectric

elastic

softening on cooling

AF

AT

OT

AF

According to Landau’s theory of phase transition in its simplest form there are steps in the compliance at the tilt and FE transitions

Identifying the anomalies in the compliance

TT

TT : tilt R3c ↔ R3m a -a -a - ↔ a *a *a * T

T

dielectric

elastic

softening on cooling

TAF : AFE ↔ FE Pbam ↔ R3m

AF

AT

TOT : orthorhombic tilt Pbam ↔ R3m a -a -c 0 ↔ a *a *a *

OT

OT OT

OT

stiffening on cooling: disapearance of piezoelectric softening

AF

softening on cooling

AF

AF

Effect of ageing & high-temperature anneal on PZT 95.4/4.6

after 25 days

Elas

tic

com

plia

nce

norm

aliz

ed t

o it

s m

inim

um v

alue

TAF

TC

huge softening after 1 month ageing + few thermal cycles through AFE/FE

stiffness completely recovered above 800 K (recovery starts ~600 K)

F. Cordero, F. Craciun, F. Trequattrini, C. Galassi, Phys. Rev. B 89, 214102 (2014) + unpublished

Effect of ageing & high-temperature anneal on PZT 95.4/4.6

after 25 days

wait 1 month heat to 900 K

x4

F. Cordero, F. Craciun, F. Trequattrini, C. Galassi, Phys. Rev. B 89, 214102 (2014) + unpublished

Elas

tic

com

plia

nce

norm

aliz

ed t

o it

s m

inim

um v

alue

TAF TC important for applications

with FE/AFE transitions especially vs T (EC cooling)

Effect of La doping on aging & fatigue of AFE/FE PZT

From the dielectric La3+ reduces the temperature

Effect of La doping on aging & fatigue of AFE/FE PZT

undoped doped 2% La

softening up to 400% during 6 thermal cycles and 1 month ageing

reproducible within 0.3%, over 10 cycles and more than one year aging

the slow kinetics of the AFE transition and material instability are not due to the O-AFE phase, which is common to the two samples, but its coexistence with the FE phase

La doping → no FE phase → no stress/electric fields

La doping eliminated the FE phase → no electric and stress fields at the AFE/FE interfaces

Volume difference between O-AFE and intermediate phases: undoped (R-FE): ∆V/V = 6x10-3 doped (IC-AFE) ∆V/V = 4x10-4

no volume mismatch after doping

F. Cordero, F. Craciun, F. Trequattrini, P. Galizia, C. Galassi, unpublished

∆V/V = 6x10-3

Piezoelectric softening

piezoelectric softening

F. Cordero, F. Craciun, F. Trequattrini, C. Galassi, arXiv 1602-02799

W. P. Mason, Phys. Rev. 55, 775 (1939) B. A. Auld Acoustic fields and waves in solids (1973) B. Sen et al. J. Appl. Phys. 112, 024517 (2012)

The piezoelectric stiffening is well known: the depolarization field created by the polarization charges produces a piezoelectric strain that stiffens the sample or resonator (poled resonators with open electrodes, elastic waves in piezoelectric media)

The piezoelectric stiffening is simply the cancelation of a piezoelectric softening with respect to the background elastic moduli

PLZT 90/10 with La 0.02-0.04

I.V. Ciuchi, F. Craciun , L. Mitoseriu , C. Galassi, Preparation and properties of La doped PZT 90/10 ceramics across the ferroelectric–antiferroelectric phase boundary, Journal of Alloys and Compounds, 2015

(Pb 1-x La x (Zr 0.9 Ti 0.1)1-x/4 � x/4 O3) - Pb2+

- Zr(Ti)4+

- O2- - La3+

selected compositions (x=0, 0.020, 0.030,0.031, 0.0320, 0.0330, 0.035, 0.038 and 0.040) across rhombohedral-orthorhombic phase boundary

solid state reaction

10 20 30 40 50 60 70 80

x=0,00

x=4,00

x=3,80

x=3,50

x=3,30

x=3,20

x=3,10

x=3,00

x=2,50

O(30

1)O(

310)O(

212)

O(22

1)O(

202)

O(22

0)

O(11

2)O(

211)

O(10

2)O(

201)

O(21

0)O(00

2)O(

200)

O(11

1)

O(10

1)O(

110)

O(00

1)

Inte

nsity

(a.u

.)

2θ

O(10

0)

x=2,00

Phase characterisation (XRD)

PLZT x/90/10

A pure perovskite phase structure

A coexistence of

FE rhombohedral phases (R3m) and

AFE orthorhombic phases (Pbam)

I.V. Ciuchi, F. Craciun , L. Mitoseriu , C. Galassi, Preparation and properties of La doped PZT 90/10 ceramics across the ferroelectric–tif l t i h s b d J l f All s d C ds 2015

Anelastic and dielectric spectroscopy PLZT x/90/10

F. Craciun, F. Cordero, I. V. Ciuchi, L. Mitoseriu, and C. Galassi JOURNAL OF APPLIED PHYSICS (2015)

• the AFE (FE)/PE transition is a first order transition, as evidenced by the thermal hysteresis of TC on heating and cooling

• the FE R phase can be induced at room temperature through an irreversible electric field-assisted phase transformation, by applying an electric field, which exceeds Et~2 kV/cm

• The induced FE R state reverts to the AFE O state only after heating above the depolarization temperature Td ~410 K

Ferroelectric Properties: AFE-FE field induced transition PLZT x/90/10

Irreversibile AFE-FE

transition

Reversibile AFE-FE

transition

Recoverable Energy Density and Efficiency

Maximum Wre = 1.85 J/cm3 for PLZT 3.5/90/10 AFE ceramic, η is 65 % at Emax 65 kV/cm

High Wre for compositions with the AFE and FE phase (2.5, 3.0, 3.1. 3.2.); η is about 60 %.

η=Wre/(Wre+Wloss)

I.V. Ciuchi, L. Mitoseriu , C. Galassi, Energy storage properties of PLZT ceramics with La compositions across FE/AFE phase boundary J. Am Ceram Soc. In press

Recoverable Energy Density and Loss

low border AFE phase

high border FE phase

Increase La Increase EF Increase Wre

PLZT x/90/10

2.0≤x≤3.5

• All PLZT compositions show high dielectric permittivity (ԑ’≥700) and low dielectric losses (tan δ below 3%) in a large range of frequency

• A low AFE to FE switching field was obtained and its value can be

adjusted by La substitution on Pb site. • At increasing La-content the Wre has been enhanced from 0.819

J/cm3 (for PLZT 2/90/10 and electric field of ~30 kV/cm ) to the highest value of 1.85 J/cm3 (for PLZT 3.5/90/10 and electric field ~65 kV/cm) followed by their subsequent reduction.

• While the PLZT system evolves from a FE state to an AFE state

both as a function of La content and electric field, the recoverable energy (Wre) and loss energy (Wloss) show two limits which lower and higher values are obtained for the compositions in AFE state and FE state, respectively.

• The high energy density (0.85≤Wre≤1.85) and high energy efficiency (41≤η≤65 %) at relatively low electric field (30≤Emax≤65 kV/cm), reveal that the investigated PLZT ceramics are quite promising for pulse power capacitors applications.

Summarizing PLZT results:

Acknowledgements

CNR-ISTEC Pietro Galizia Carlo Baldisserri Claudio Capiani Ioana Ciuchi Silvia Romano Andreana Piancastelli CNR-ISC Francesco Cordero Floriana Craciun CNR-IMEM Franca Albertini

IASI University Department of Physics Liliana Mitoseriu Cristina Ciomaga and Co-workers Vilnius University Department of Physics Robertas Gragalaitis

IASI University ROMANIA