The Synthesis and Investigation of Thermoelectric Properties of Cu₄SnS₄ at Elevated Temperatures

Cu₄SnS₄ is a promising thermoelectric (TE) material due to its low thermal conductivity ( \(\kappa\) $\kappa$ ) and relatively high electrical conductivity ( \(\sigma\) $\sigma$ ) and Seebeck coefficient (S). In this research, Cu₄SnS₄ was synthesized from Cu, Sn, and S powders using the mechanical alloying (MA) method. The 16-h milled powders were heat-treated and consolidated by spark plasma sintering at 873 K. TE properties of the 16-h milled sintered sample was investigated at elevated temperatures. It was observed that the formation of Cu₃SnS₄ began after 8 h and completed after 16 h of milling, whereby the resulting material exhibited fine particle sizes, ranging from 0.2 to 1.3 µm. Cu₄SnS₄ was formed after the heat treatment of the 16-h milled powder at 673 K, with a thermal stability up to 923 K. The band gap of the heat-treated powder was 1.62 eV. The values of power factor and the dimensionless figure of merit (ZT) increased dramatically with increasing temperature, until the maximum values of 174.4 µW/m K² and 0.05, respectively, were achieved at 723 K.