Crystals classified by electric conductivity


Metals

Metals have lattices with metallic bonding either elementary or alloys.

Semimetals

Semimetals have covalent-metallic bonding, where electrons not used in covalent bonding delocalize and produce metallic bonding between covalently bound layers (therefore they have anisotropic conductivity). They are graphite and

A7Vα-As, Sb, Bi, and their alloys, rhombohedral graphite

Semiconductors

Elementary semiconductors have covalent bonding:

A4 IVC, Si, Ge, α-Snindirect bandgap
A8VISe, Te 

Other elementary semiconductors include B, black-P, α-S.

Binary semiconductors have donor-acceptor or covalent-ionic bonding:

B3
(zincblende)
IV+IVβ-SiC
III+VBP, AlP, GaP, InP, AlAs, GaAs,..., InSb
II+VIZnS, CdS, CdTe, ZnTe, ZnSe, HgS, HgTe
I+VIIβ-AgI, CuBr
B4
(wurtzite)
IV+IVα-SiC
III+VAlN, GaN, InN
II+VIZnS, CdS, ZnO
B1
(rock salt)
IV+VIPbS, PbTe, SnTe (narrow gap)
II+VICdO
I+VIIAgCl, AgBr, γ-CuI

Triple semiconductors:

E11 (chalcopyrite)II+IV+VCdSnAs2, CdGeAs2

Substitutional alloys are possible like GaxAl1-xAs, GaAsxP1-x, CdxHg1-xTe, PbxSn1-xTe.

Insulators

In contrast to wide-gap semiconductors insulators "absorb" free carriers by intrinsic defects. This process is efficient in ionic (NaCl) or wide-gap covalent-ionic (SiO2) crystals. Other kind of insulator is molecular crystal.

Superionic conductors

There are two kinds of superionic conductors. The first is ionic crystals with small enough cations to move through the lattice of anions (therefore cation sublattice is disordered). The motion has activation barrier so that typically there is structural transition to high-temperature superionic state: AgI, AgBr, AgCl, CuBr, CuCl, Ag2S, Cu2S. There are also moving cations: PbF2, CaF2, BaF2, ZrO2.

The second kind is porous covalent-ionic crystals with weakly bound ions (typically impure).