Thermoelectric properties of p-Bi2 ? xSbxTe3 solid solutions under pressure

This paper reports on a study of the Seebeck coefficient and power factor κ of p-Bi_{2 − x} Sb _x Te₃ solid solutions with different contents of antimony atoms in the bismuth sublattice for x = 0, 1.4, 1.5, and 1.6 under variation of pressure of up to 15 GPa. The magnitude of κ has been found to grow nonmonotonically within the pressure region of 2–4 GPa. The effective mass of the density of states m/m ₀ and the mobility μ₀ have been calculated with due account of degeneracy within the parabolic model of the energy spectrum assuming isotropic charge carrier scattering. It has been shown that application of pressure brings about a decrease of the effective mass m/m ₀ and an increase of carrier mobility. The power factor κ of the p-Bi_0.6Sb_1.4Te₃ composition exhibits at the pressure P ≈ 4 GPa the largest increase of the power factor κ as a result of a weak decrease of the effective mass m/m ₀ and an increase of carrier mobility as compared to the other solid solution compositions. The specific feature of the variation of the power factor κ with a change of the pressure in bismuth telluride near P ≈ 3 GPa, which is accompanied by formation of a knee in the m/m ₀ vs. P dependence, can be assigned to an electronic topological transition.