Impact of CuFeS2 on the Thermoelectric Performance of SnTe

Thermoelectric materials possess tremendous potential in energy regeneration owing to their capacity to produce power directly from heat. SnTe, a lead-free compound, is a prospective thermoelectric material. However, because of its elevated thermal conductivity, the thermoelectric performance of undoped SnTe remains at a low level. In this work, we induce ternary compounds CuFeS₂ into the SnTe matrix by ball milling. We observe the decomposition of CuFeS₂, which decomposes into FeS, Cu₂S, and other binary compounds. These newly generated binary compounds form micropores and secondary phases in the matrix. Combined with the natural grain boundaries in the polycrystal, they form all-scale hierarchical structures within the material, resulting in reduced lattice thermal conductivity. Overall, the produced SnTe + 2 wt% CuFeS₂ composites show the peak dimensionless figure of merit (ZT) up to 0.33 at 673 K, an increase of ~ 100% compared to the undoped SnTe.