Quenched compounds (Bi
1-
xSb
x)
2 (Te
1-
ySe
y)
3 were given heat treatment for 10hr. at 400C., and Hall coefficient
R and electrical conductivity σ were measured over a temperature range of 80-300K. It was found that composition of compounds with vanishing Hall coefficient is approximately given by
x=(
y-0.25)
2+0.35 at 100K. Hall coefficient hardly changes with temperature but does change with composition. Composition dependence of electrical conductivity is approximately expressed by σ∝[
ax(1-
x)+
by(1-
y)+
c]
-1, where
a,
b and
c are constants Temperature dependence of electrical conductivity is more gradual than
T-1.5.
The following conclusions are obtained from a discussion of the experimental results; (1) Impurity and alloy scattering are as important factors of scattering mechanism as acoustical lattice scattering in many compounds. (2) Carriers of these compounds are almost invariably the lattice defects themselves. (3) Composition dependence of electrical conductivity is given by the factor (
m*
5/2ED2), where
m* is the effective mass of a charged carrier and
ED is the deformation potential. (4) Conduction and valence bands both consist of two bands.
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