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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
9.5. Dielectric Properties
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
9.5. Dielectric Properties
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
Fig 7.14 From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)
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.
Fig 7.15 From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)
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)
Fig 7.25 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)
Fig 7.32 From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)
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
Fig 7.33 From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)
(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.
Fig 7.34 From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)
(a)
Al case
Al foils
Al2O3
Anode Cathode
(b)
Electrolyte
Al Al
Fig 7.35 From Principles of Electronic Materials and Devices, Third Edition, S.O. Kasap (© McGraw-Hill, 2005)
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
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)
Capacitor (condenser) : electrical components with dielectrics
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
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
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)
Capacitor (condenser) : electrical components with dielectrics
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
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).