Thermoelectric Properties of Solid Solutions with Cation and Anion Substitution on the Basis of the Layered Tetradimite-like Compound GeSnSb4Te8.

The thermoelectric characteristics of GeSnSb₄Te₈ quaternary compound and GeSnSb_{4 –x}Bi_xTe_{8 –y}Se_y solid solutions are measured in a wide temperature range of 300–600 K. The substitution of Sb for Bi and Te for Se leads to an increase in the thermopower coefficient and a decrease in the lattice component of the thermal conductivity as compared with the corresponding values for GeSnSb₄Te₈. The lower values of the lattice thermal conductivity in alloys with x = 0.6 and y = 0.4 in comparison with those in GeSnSb₄Te₈ are associated with distortions due to a difference in the atomic masses and sizes of Sb and Bi, as well as Te and Se. It is shown that, with an increase in the number of atoms participating in substitutions in both sublattices during the formation of solid solutions, the peak of the temperature dependence of the thermopower and the lowest value of the temperature dependence of the thermal conductivity are shifted to higher temperatures, which is induced by an increase in the band gap. With an increase in the content of Bi and Se in solid solutions, the lattice thermal conductivity decreases and, correspondingly, the thermoelectric efficiency increases. The thermoelectric figure of merit of the GeSnSb_{4 –x}Bi_xTe_{8 –y}Se_y sample (x = 0.6, y = 0.4) has the highest value with Z = 3.34 × 10^–3 K^–1 at 300 K. [ABSTRACT FROM AUTHOR]