Enhancing the thermoelectric performance of Cu1.8S by Sb/Sn co-doping and incorporating multiscale defects to scatter heat-carrying phonons

Abstract

Cu-based chalcogenides have attracted increasing attention as a potential thermoelectric material due to their unique structural features, high element abundance, and low toxicity. In this paper, a series of Cu_1.8Sb_xSn_yS compositions (0.01 < x < 0.04, 0.015 < y < 0.045) were prepared by a simple method combining mechanical alloying (MA) and spark plasma sintering (SPS). The results demonstrate that Sb/Sn co-doping can optimize the hole concentration and substantially improve the dimensionless figure of merit (ZT) of copper–sulfide Cu_1.8S. The highest ZT, up to 1.2 at 773 K, was realized for the Cu_1.8Sb_0.02Sn_0.03S sample and maintained a high power factor of 975 μW m⁻¹ K⁻². The reduction in thermal conductivity was linked to the heterogeneous phase of Cu₁₂Sb₄S₁₃ and Cu₄SnS₄. Remarkably, after four testing cycles, the variation in ZT was less than 2%, indicating a good stability of the Sb/Sn co-doped Cu_1.8S materials.