Optimization of the Thermoelectric Performances of CoSbS Semiconductors Using the High-Pressure Fabrication Method

Abstract

CoSbS-based compounds are good thermoelectric materials with low thermal conductivity and good electrical properties, which can effectively be used to improve the efficiency of many thermoelectric conversion processes. In order to improve their properties even more, in this study a series of experiments have been conducted in the frame of the traditional solid-phase synthesis and high-pressure method. It is shown that if the mass fluctuation and stress fluctuation in the considered CoSbS system increase, the scattering probability of phonons is enhanced and the lattice thermal conductivity of the material is reduced. Adding a small amount of Se can simultaneously optimize three thermoelectric properties, i.e., the Seebeck coefficient is improved, the thermal conductivity becomes smaller and the quality factor grows. At the same time, the thermal and electrical properties of bulk materials can be optimized by using nano-scale Ni doped CoSbS samples. As shown by the experiments, Ni-doped Co sites can effectively improve the carrier concentration, the effective mass of the density of states of the material, and the power factor. Under the same temperature conditions, the thermoelectric figure of merit (ZT) of Co1−yNiySbS1−xSex synthesized under high pressure, at x = 0.15, y = 0.1 is much higher than the corresponding value for CoSbS prepared by traditional methods.