The p-type (Bi
0.25Sb
0.75)
2Te
3 doped with 3-12 wt% excess Te alone and n-type Bi
2(Te
0.94Se
0.06)
3 codoped with 0.017-0.026 wt% Te and 0.068-0.102 wt% I were prepared by the Bridgman method, to produce intentionally polycrystalline. Some of the as-grown specimens were annealed, in order to prepare specimens with much different
ρ. These polycrystalline specimens have almost the same degree of alignment of the
c plane parallel to the freezing direction. The electrical rersistivity
ρ and thermal conductivity
κ were measured at 298 K along the freezing direction and
κ was plotted as a function of
ρ. As a result, the lattice components
κph obtained by subtracting the electronic component
κel from the observed
κ were found to decrease almost linearly with a decrease of
ρ in both p- and n-type specimens, where
κel was calculated using Wiedemann-Franz law. This tendency is consistent with the conventional result that
κph becomes negligible small in metals. The significant decrease in
κph with decrease in
ρ is considered to be caused predominantly by the phonon scattering due to dopants. The relationship between
κph and
ρ was first clarified in the intermediate region between the metal and insulator.
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