Effects of Se Doping on Thermoelectric Properties of Tetrahedrite Cu12Sb4S13−zSez

Abstract

Tetrahedrite Cu12Sb4S13 is composed of abundant non-toxic components and has attracted attention as a promising thermoelectric material with low thermal conductivity at intermediate temperatures. The carrier concentration can be optimized by doping (substituting), thereby maximizing its power factor and reducing its thermal conductivity. In this study, Cu12Sb4S13−zSez (z = 0.1–0.4) compounds were synthesized using mechanical alloying and hot pressing. Our objective was to maintain a high power factor through Se doping and to reduce the lattice thermal conductivity through additional phonon scattering. X-ray diffraction analysis revealed that the lattice constant increased with an increase in Se substitution for the S sites, and all the specimens appeared as a single tetrahedrite phase. As the Se doping level increased, the carrier (hole) concentration decreased while the mobility increased. The Hall and Seebeck coefficients were both positive, indicating that Se-doped tetrahedrites exhibit p-type conduction. As the Se substitution increased, the electrical conductivity decreased, but the Seebeck coefficient increased. In addition, Se doping lowered both, the electronic and lattice thermal conductivities, which resulted in decreased thermal conductivity. A maximum dimensionless figure of merit (ZT) of 0.87 was obtained at 723 K for Cu12Sb4S12.8Se0.2 with a high power factor of 0.96 mW m−1 K−2 and a low thermal conductivity of 0.77 W m−1 K−1.