Thermoelectric properties of the Cu2SnSe3–Cu2GeSe3 solid solution

We present results on the electrical resistivity, Seebeck coefficient, and thermal conductivity for Cu2Sn1−xGexSe3 alloys, with x ranging from 0 to 0.5. Samples quenched in water from high temperature were found to crystallize in a disordered zincblende-like structure while samples cooled slowly assumed a monoclinic structure. We observed little phonon scattering due to atomic mass fluctuations upon the addition of Ge at room temperature. The thermal conductivity is analyzed using the Debye model with the Grüneisen constant as the only adjustable parameter. An increase in electrical resistivity for the Ge-containing samples was offset by their enhanced Seebeck coefficients. The slow-cooled x = 0.2 sample showed the best thermoelectric properties with dimensionless figure of merit ZT = 0.0353 at 300 K, a relatively large value compared to other Cu-based multinary compounds.

Research highlights▶ Quenched samples of Cu2Sn1−xGexSe3 possess a zincblende-like crystal structure. ▶ Slow-cooled samples of Cu2Sn1−xGexSe3 possess a monoclinic crystal structure. ▶ Ge substitution has only a small influence on the thermal conductivity at room temperature. ▶ The best thermoelectric properties for these alloys are found for x = 0.2 in slow-cooled specimens.