Table 7.1 Typical examples of polarization mechanisms.
Example
Polarization
Static !r
Comment
Ar gas
Electronic
1.0005
Small N in gases: !r "1
Ar liquid (T < 87.3K)
Electronic
1.53
van der Waals bonding
Si crystal
Electronic polarization
due to valence electrons
11.9
Covalent solid;
Electronic bond polarization
NaCl crystal
Ionic
5.90
Ionic crystalline solid
CsCl crystal
Ionic
7.20
Ionic crystalline solid
Water
Orientational
80
Dipolar liquid
Nitromethane (27°C)
Orientational
34
Dipolar liquid
PVC
(Polyvinyl chloride)
Orientational
7
Dipole orientations partly
hindered in the solid
From Principles of Electronic Materials and Devices, Second Edition, S.O. Kasap (© McGraw-Hill, 2002)
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Table 7.2 Dielectric properties of three insulators.
ƒ = 60 Hz
Material
ƒ = 1 MHz
!r'
tan#$
%tan#$
! r'
tan#$
%tan#$
3.17
9&10-4
0.34
2.96
1&10-2
6.2&104
Silicone rubber 3.7
2.25&10-2
8.48
3.4
4&10-3
2.5&104
Epoxy with
mineral filler
4.7&10-2
17.7
3.4
3&10-2
18&104
Polycarbonate
5
From Principles of Electronic Materials and Devices, Second Edition, S.O. Kasap (© McGraw-Hill, 2002)
http://Materials.Usask.Ca
Table 7.3 Dielectric loss per unit volume for two insulators.
f = 1 MHz
Material
! r'
tan#
f = 1 MHz
Loss
(mW cm-3)
!r'
tan#
Loss
'
-3
(mW cm ) (W cm-1 K
XLPE
2.3
3&10
-4
0.230
2.3
4&10
-4
5.12
0.005
Alumina
8.5
1&10
-3
2.84
8.5
1&10
-3
47.3
0.33
From Principles of Electronic Materials and Devices, Second Edition, S.O. Kasap (© McGraw-Hill, 2002)
http://Materials.Usask.Ca
Table 7.4 Dielectric Strength; typical values at room temperature and 1 atm.
Dielectric Medium
Dielectric Strength
Comment
Atmosphere at 1 atm
pressure
37.1 kV cm at 60Hz
SF6 gas
79.3 kV cm at 60Hz
Polybutene
>138 kV cm at 60Hz
Transformer oil
128 kV cm at 60Hz
Amorphous silicon
dioxide (SiO2) in MOS
technology
10 MV cm dc
Borosilicate glass
10 MV cm duration of 10µs Intrinsic breakdown.
-1
6 MV cm duration of 30 s
Thermal breakdown.
Polypropylene
295-314 kV cm
-1
1 cm gap. Breakdown by electron
avalanche by impact ionization
-1
Used in high voltage circuit
breakers to avoid discharges
-1
Liquid dielectric used as oil filler
and HV pipe cables
-1
-1
Very thin oxide films without
defects. Intrinsic breakdown limit.
-1
-1
Likely to be thermal breakdown or
electrical treeing.
From Principles of Electronic Materials and Devices, Second Edition, S.O. Kasap (© McGraw-Hill, 2002)
http://Materials.Usask.Ca
Table 7.5 Dielectric insulation candidates for a coaxial cable.
Strength
!r
Dielectric (60Hz) (60Hz)
(kV cm-1)
C
(60Hz)
(pF m-1)
Breakdown
Voltage
Voltage for Partial
Discharge in a
Microvoid
XLPE
2.3
217
116
59.6 kV
11.9 kV
Silicone
rubber
3.7
158
187
43.4 kV
7.4 kV
From Principles of Electronic Materials and Devices, Second Edition, S.O. Kasap (© McGraw-Hill, 2002)
http://Materials.Usask.Ca
Table 7.6 Comparison of dielectric properties at 60 Hz for capacitor applications; typical
values. (Assume η = 2, PS = Polystyrene, PET = Polyehthyleneterephthalate. X7R is the name
of a particular ceramic solid solution.).
Polymer
film
PS
Polymer
film PET
Mica
Name
Polystyrene Polyester
Mica
!r'
2.5
6.9
tan#
3&10
-1
3.2
-4
5 &10
-3
5x10
-4
Ceramic
Al2O3
High-K
Ceramic
(BaTiO3
based)
Anodized Polycrystalline X7R
alumina titania
film
8.5
90
1,800
1x10
-3
Ceramic
TiO2
4 x10
-4
5x10
-2
Ebr (kV cm )
200-250
150-200
1000
1000
50-100
100
d (typical
minimum)
-3
Cvol ((F cm )
1-2 (m
1-2 (m
2.5 (m
0.1 (m
10 (m
10 (m
22.1
28
10
7,500
7.5
159.4
-3
1.1
0.80
76
94
2.5
200
Wvol (W cm )
-3
0.00025
0.0030
0.029
0.071
0.00075
7.5
Polarization
Electronic
Bond
Electronic
bond and
Dipolar
Ionic
Ionic
Ionic
Large ionic
displacement
Evol (mJ cm )
From Principles of Electronic Materials and Devices, Second Edition, S.O. Kasap (© McGraw-Hill, 2002)
http://Materials.Usask.Ca
Table 7.7 Piezoelectric materials and some typical values for d (piezoelectric
coefficient) and k (electromechanical conversion factor).
-1
k
Comment
-12
0.1
Crystal oscillators, ultrasonic transducers,
delay lines, filters
Crystal
d (m V )
Quartz (crystal SiO2)
2.3&10
Rochelle salt
(NaKC4H4O6.4H2O)
350&10
-12
0.78
Barium titanate (BaTiO3) 190&10-12
0.49
Accelerometers
PZT, Lead zirconate
titanate (PbTi1-xZrxO3)
480&10
0.72
Wide range of applications including
earphones, microphones, spark
generators(gas lighters, car ignition),
displacement transducers, accelerometers.
Polyvinylidene fluoride
(PVDF)
18.2&10
-12
-12
Must be poled; heated, put in an electric
field and then cooled. Large area and
inexpensive.
From Principles of Electronic Materials and Devices, Second Edition, S.O. Kasap (© McGraw-Hill, 2002)
http://Materials.Usask.Ca