Electrical Properties of Polymers, Ceramics, Dielectrics, and …contents.kocw.net/KOCW/document/2013/Inha/JungDaeyong/11.pdf · 2016-09-09 · Electrical Properties of Polymers,

Electrical Properties of Polymers, Ceramics, Dielectrics, and

Amorphous Materials

Dae Yong JEONG

Inha University

9.5. Dielectric Properties

Insulator (Dielectric materials) Insulator (generally refer to the materials with R ~ infinite)

Dielectric materials can be usually used for AC and other functional applications. (capacitor, piezoelectric, pyroelectric etc)

Dielectrics

Piezoelectricity

Pyroelectricity

Ferroelectricity

Metal

Semiconductor

Electronic Materials

Most ceramic (Al2O3, ZrO2, SiO2…)

Polymer : PE, PP…

ZnO, Quartz, AlN…

Pb(ZrTi)O3, BaTiO3, PVDF polymer


CVQ

F/m .

L

AC

-

o

o

12108548

vacuumofty Permittivi :

1air for

typermittivi relative

constant dielectric :K)(or

vacC

C

why large dielectric constant with materials?

From Electronic properties of materials, Fourth Edition, Hummel (© Springer, 2010)

Capacitor in circuit

When apply the voltage on Capacitor.

DC: No current flow through capacitor

AC (voltage changes with time.)

Charging

t = 0

just start accumulation of electron on the surface of electrode in capacitor

just small voltage across the capacitor

t = t1

Full accumulation of electron on the surface of electrode max voltage of

capacitor No more electron flows in the outer circuit

For AC current, it seems that current flows through the

capacitor…

Dielectric Materials for Capacitor

)90sin(11

sin1

)(1

sin)(

o

mmm

m

tiC

tcowiC

tdtiC

dttiC

V

titi

dt

tdVC

dt

tdQti

)()()(

Phase of voltage is 90o ahead of current.

Control the electrical current with Capacitor

V= RI V = Zc I

Zc: capacitive impedance : (resistance in AC)

Zc Should have information on phase difference and

magnitude.

IZcI = 1/ωC

Remark ZR: resistive impedance

IZRI = R

Same phase of voltage and current

ZL: inductive impedance

IZLI = ωL

Phase of voltage is 90o behind of current.

Application of C

Energy storage Energy = ½ CV2

Frequency filter (with the combination of L, R)

DC source (i=C dV/dt)

Impedance {Zc = -j/(2πfC), f: frequency}

(PLS refer to the books on “Basic electronic circuit”.)

How much is Xc(impedance) and (Yc) admittance

for:

(a) 0.1 uF of C at 1400 Hz?

(b) 1uF of C at the same frequency?

+ - +

+ -

+ - + + - +

Electronic

Ionic

Orientation

Space Charge

No field Field applied


spontaneous polarization

pore pore + + +

- - -

9.5. Dielectric Materials Applying V on to dielectrics No current flow through the material (insulator) (-) charged electron cloud of an atom becomes displaced with respect to its (+)

charged core.

(a, b, c) Inside material, polarization changes to compensate the applied Electric field. (di-delete, electric) Polarization direction [(-) to (+) ] opposite to E-field [(+) to (-)]

vac

Electric field strength in a material

Dielectric Displacement, D [charge/unit surface area] = [C/m2] Total charge = charge due to E-field w/o material (ie vacuum) + Polarization from material

+ - x Electrical dipole moment xqp

litysusceptibi:

1

1

o

ooo

P

PA

qD

Dielectric Property Material Dielectric constant

Vacuum 1. (by definition)

Air 1.00054

Teflon™ 2.1

Polyethylene 2.25

Silicon dioxide (SiO2) 3.7

FR-4 (PCB substrate) 4.35-4.7

Diamond 5.5–10

Graphite 10–15

Silicon 11.68

H2O 88–80.1–55.3–34.5

(0–20–100–200 °C)

TiO2 86–173

SrTiO3 310

(BaSr)TiO3 500

BaTiO3 1250–10,000

(20–120 °C)

(La,Nb):(Zr,Ti)PbO3 500–6000

9.5. Dielectric Properties application

At a certain frequency, large loss

Microwave oven?

Water has spontaneous polarization.

Oxygen (-)

Due to lone pair electron

Hydrogen (+)

http://www.shinwonbook.co.kr 물분자의 춤솜씨 (고교생이 알아야 할 화학 스페셜, 2003.10.1, (주)신원문화사)

Fig 7.13 From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)

v = Vosint

P = Posin(t - )

E = Eosint

(a)

r''

r'

r

(0)

1

1/10/

100/0.01/

0.1/

r' and r''

(b)

(a) An ac field is applied to a dipolar medium. The polarization P (P = Np) is

out of phase with the ac field. The relative permittivity is a complex number

with real (r') and imaginary (r'') parts that exhibit frequency dependence.

9.5. Dielectric Properties Dielectric Relaxation


v = Vosint

P = Posin(t -)

C

Conductance = Gp

= 1/Rp

v = Vosint

The dielectric medium behaves like an ideal (lossless) capacitor of

capacitance C which is in parallel with a conductance Gp.


102 104 106 108 1010 1012 101 4 1016ƒ

Orientational,

Dipolar

Interfacial and

space charge

Ionic

Electronic

r'

r''

r' = 1

1102

Radio Infrared Ultraviolet light

The frequency dependence of the real and imaginary parts of thedielectric constant in the presence of interfacial, orientational, ionic

and electronic polarization mechanisms.

Dielectric dispersion Depending on frequency different reaction

For example,

Electron polarization at optical frequency refractive index (n= sqrt (dielectric constant in optical frequency)

Dielectric Loss A substantial amount of

Excitation energy Heat

9.5. Dielectric Properties Dielectric Relaxation

Fig 7.18

From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)

Rs

Cs

C

A

B B

A

Dipolar

dielectric

A capacitor with a dipolar dielectric and its equivalent circuit in terms of an ideal

Debye relaxation.

Dielectric (material) Properties electrical circuit

9.5. Dielectric Breakdown

From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)


Corona and Partial Discharges: (a) The field is greatest on thesurface of the cylindrical conductor facing the ground. If the voltageis sufficiently large this field gives rise to a corona discharge. (b) Thefield in a void within a solid can easily cause partial discharge. (c)The field in the crack at the solid-metal interface can also lead to apartial discharge.

High voltage conductor

Gas

Ground

(a)

Void in dielectric

(b)

Crack (or defect) at dielectric-

electrode interface

(c)

Capacitor in electrical circuit

9.5. Dielectric Materials for Capacitor

Electrical circuit

R, L, C

Diode, TR…

Why is not “L-inductor” on Si wafer?

With R and C possible to emulate the “L”

What is function of “C”?

From Electronic properties of materials, Fourth Edition, Hummel (© Springer, 2010)

9.5. Capacitor

n

i

iCC1

n

i iCC 1

11

multilayer ceramic

ceramic disc

tubular ceramic

polystyrene

metallized polyester film

aluminium electrolytic

through-hole electrolytic

through-hole tantalum

multilayer polyester film

MLCC: Multilayer Ceramic Capacitor

MLCC: 삼성전기, 삼화콘덴서, 일본(무라타 ect)

http://upload.wikimedia.org/wikipedia/commons/d/de/Condensators.JPG

http://upload.wikimedia.org/wikipedia/commons/8/86/Photo-SMDcapacitors.jpg


Metal termination

Metal electrode

CeramicEpoxy

Leads

(b) Multilayer ceramic capacitor

(stacked ceramic layers)(a) Single layer ceramic capacitor(e.g. disk capacitors)

Single and multilayer dielectric capacitors


(b)

Al metallization

Polymer film

(a)

Two polymer tapes in (a) each with a metallized film electrode on thesurface (offset from each other) can be rolled together (like a Swiss roll-cake) to obtain a polymer film capacitor as in (b). As the two separatemetal films are lined at oppose edges, electroding is done over the wholeside surface.


(a)

Al case

Al foils

Al2O3

Anode Cathode

(b)

Electrolyte

Al Al


Epoxy

Silver paint

Ta

Lads

(a) (b)

Ta

Ta2O5

MnO2

Graphite

Silver paste

Solid electrolyte tantalum capacitor. (a) A cross section withoutfine detail. (b) An enlarged section through the Ta capacitor.

Comparison of dielectrics for capacitor applications

Capacitor name Polypropylene Polyester Mica Aluminum,

electrolytic

Tantalum,

electrolyt

ic, solid

High-K ceramic

Dielectric Polymer film Polymer film Mica Anodized Al2O3

film

Anodized

Ta2O5

film

X7R

BaTiO3 base

r 2.2 – 2.3 3.2 – 3.3 6.9 8.5 27 2000

tand 4 10-4 4 10-3 2 10-4 0.05 - 0.1 0.01 0.01

Ebr (kV mm-1) DC 100 - 350 100 - 300 50 - 300 400 - 1000 300 - 600 10

d (typical minimum) 3 - 4 µm 1 µm 2 - 3 µm 0.1 µm 0.1 mm 10 µm

Cvol (µF cm-3) 2 30 15 7,500a 24,000a 180

Rp = 1/Gp; C = 1 mF;

1000 Hz

400 kW 40 kW 800 kW 1.5 - 3 kW 16 kW 16 kW

Evol (mJ cm-3)b 10 15 8 1000 1200 100

Polarization Electronic Electronic and

Dipolar

Ionic Ionic Ionic Large ionic

displaceme

nt

NOTES: Typical values. h = 3 assumed. The table is for comparison purposes only. Breakdown fields are typical DC values,

and can vary substantially, by at least an order of magnitude; Ebr depends on the thickness, material quality and the duration

of the applied voltage. a Proper volumetric calculations must also consider the volumes of electrodes and the electrolyte

necessary for these dielectrics to work; hence the number would have to be decreased. b Evol depends very sensitively on

Ebr and the choice of h; hence it can vary substantially. Polyester is PET, or polyehthylene terephthalate. Mica is potassium

aluminosilicate, a muscovite crystal. X7R is the name of a particular BaTiO3-based ceramic solid solution.

Dielectric Properties



Capacitor (condenser) : electrical components with dielectrics

Dielectrics

Piezoelectricity

Pyroelectricity

Ferroelectricity

Metal

Semiconductor



Polymer : PE, PP…

ZnO, Quartz, AlN…


Electric Materials: Paraelectric

• Paraelectric:

• No spontaneous polarization

without E

• Induced polarization with E • But induced polarization is quite

small.

• Linear dependence

E (V/cm)

P (µC/cm2)

P

EKEEP

EP

ooo

o

D

air.for negligible benot could and small is icparaelectrfor

1D

9.6. Ferroelectricity

• Ferroelectric has spontaneous polarization

P & Polarization can be switchable by E field.

(Ferroelectric has a hysteresis loop.)

• Ps: saturation polarization

• Pr: remanent polarization

• Ec: cohesive field

PS

E

P

Ec

Pr

-Pr

Polycrystal

Grain/Grain boundary

Domain/Domain boundary Single crystal

Domain boundary

E = 0 Random domain

E < Ec Polarization

Magnitude change

E > Ec Polarization switching

One direction alignment

E = 0 Pr

Thermal fluctuation

E > Ec Polarization switching

One direction alignment

Opposite direction

Ferroelectric

• feroelectric:

• Spontaneous polarization (Ps) without E

• Induced polarization with E total P = Ps + ΔP • But induced polarization is quite large!!

• Nonlinear dependence

• At a certain E, derivate (instant slope)

P

EKEEP

EP

ooo

o

D

1)( large. quite is ricferroelectfor

1D

anti-ferro-electric

E (V/cm)

P (µC/cm2)

Ferro-behavior

Ferroelectrics

Poling process

E-field with Temp

Random aligned

T increases

Depoling/random P decreases.

P = 0

Paraelectric state

Curie Temp.

Phase transition

Cooling

Ferroelectric Oxide

Formula Tc (oC) Ps (uC/cm2) at T (oC)

LiNbO3

NaNbO3

KNbO3

Pb(0.55Sc0.5Nb)O3

Pb(0.33Mg0.67Nb)O3

Pb(0.33Zn0.67Nb)O3

LiTaO3

PbTa2O6

Pb(0.5Fe0.5Ta)O3

SrBi2Ta2O3

Sm(MoO4)3

Eu2(MoO4)3

Pb5GeO11

SrTeO3

1210

-200

435

90

-8

140

665

260

-40

335

197

180

178

485

71

12.0

30.3

3.6

24.0

24.0

50.0

10.0

28.0

5.8

0.24

0.14

4.6

3.7

23

-200

250

18

-170

125

25

25

-170

25

50

25

25

312

Perovskite

Perovskite

Typical structure for ferroelectric properties

m3m :Simple cubic]

Example, BaTiO3, Tc = 120 °C

O

O Ba Ba

Ba Ba

Ba Ba

Ba Ba

O

O

O

O

Ti O

O Ba Ba

Ba Ba

Ba Ba

Ba Ba

O

O

O

O

Ti

T>Tc, Cubic T<Tc, Tetragonal

Tc = 120 oC

Dielectric Properties



Capacitor (condenser) : electrical components with dielectrics

Dielectrics

Piezoelectricity

Pyroelectricity

Ferroelectricity

Metal

Semiconductor



Polymer : PE, PP…

ZnO, Quartz, AlN…


Piezoelectric Property

Most Dielectric Materials E field Displacement change (D)

No length change

Any material (Mechanical Property)

Stress (Force/area) shrink or expand (Strain)

No electric charge change

But, Piezoelectric (Special)

Cross effect of electric and mechanical properties

Stress charge change or E-field Strain generation

d

VE

d

AKC

EKDA

Vd

AK

A

QVCQ

o

oo

, as

1

StresscomplianceStrain

sTSl

l

o

Piezoelectrics Direct piezoelectric effect

constant icPiezoelect :ijk

jkijki

d

TdP

Inverse piezoelectric effect

kijkij EdS

Dielectrics

Piezoelectricity

Pyroelectricity

Ferroelectricity

Quartz

Pb(ZrTi)O3 (PZT), BaTiO3, PVDF polymer...

Nonferroelectric

Quartz d = 2 x 10-12 C/N

ZnS d = 10 x 10-12 C/N

Ferroelectric

BaTiO3 d33 = 149 x 10-12 C/N

Pb(ZrTi)O3

Hard

d33 = 200~300 x 10-12 C/N

Soft

d33 = 400~600 x 10-12 C/N

ZnO, ZnS, AlN…

Electrostriction and Pyroelectrics

Electrostriction

Pyroelectric

T

Pp s

p = pyroelectric coefficient [C/(cm2 K)]

t

Tp

t

T

T

P

t

PJ ss

Materials:

Devices: J= current density [C/(cm2 sec)]

dT/dt = heating rate [oC/sec]

Applications

: IR sensor, sensor for flushing of toilet, sensor for entrance of door…

tcoefficien ictiveElectrostr :

2

Q

QESl

l

o

H.W.

2, 3, 4, 6

Capacitor composed of the parallel Metal plates

with 650 mm2 of Area and 4.0 mm of distance

holds 2.0 x 10-10 C of charge.

(a) When inserting the materials with dielectric constant

(or relative dielectric constant) of 3.5, which voltage is

required for this capacitor?

(b) Without inserting materials, if keep the air between

two metal plate, which voltage is required?

(c) For (a), calculate the dielectric Displacement (C/m2).

(d) For (a), calculate the polarization (C/m2).

Documents

Electrical Properties of Polymers, Ceramics, Dielectrics, and …contents.kocw.net/KOCW/document/2013/Inha/JungDaeyong/11.pdf · 2016-09-09 · Electrical Properties of Polymers,