# Values for dielectric constants

| Here are some values for dielectric constants:
|  | First, some of themore interesting materials with electronic polarization at work, at least to some noticeable extent.
Static er for some semiconductors.
Covalent bonding | Covalent and ionic bonding
Electronic polarization is the main mechanism | Mix of electronic and ionic polarization
C | 5.7 | ZnO | 4.6
Si | 12.0 | ZnS | 5.1
Ge | 16.0 | ZnSe | 5.8
SiC | 6.7 | CdS | 5.2
GaP | 8.4 | CdSe | 7.0
GaAs | 10.9 | BeO | 3.0
InP | 9.6 | MgO | 3.0
The numbers are from "Solid State Physics" of Ashcroft / Mermin (an advanced text book).
|  | Next, some numbers for ionic crystals. Besides the static er(w = 0), the value er(w = ¥) for very high frequencies is also given. This means that after ionic polarizaton "dies out", there is still some electronic polarization left.
Static and high-frequency er for some ionic crystals
Crystal | er(w = 0) | er(w = ¥)
LiF | 9.01 | 1.96
NaF | 5.05 | 1.74
KF | 5.46 | 1.85
LiCl | 11.95 | 2.78
NaCl | 5.90 | 2.34
KCl | 4.84 | 2.19
LiBr | 13.25 | 3.17
NaBr | 6.28 | 2.59
LiI | 16.85 | 3.80
NaI | 7.28 | 2.93
The numbers are from "Solid State Physics" of Ashcroft / Mermin (an advanced text book).

With frame

3.2.2 Electronic Polarization

3.2.3 Ionic Polarization

© H. Föll (Advanced Materials B, part 1 - script)