High‐quality p‐type chalcostibite CuSbS2 single crystal is successfully synthesized by zone melting method for investigating fundamental properties. The grown crystal is orthorhombic structure and nearly stoichiometric with slightly Cu‐rich composition. The electrical properties are the hole concentration of 8.0 × 1016 cm−3, conductivity of 0.8 S cm−1, and mobility of 65 cm2 V−1 s−1 by Hall effect measurement at room temperature. Intrinsic low thermal conductivity in CuSbS2 single crystal is 0.9 W mK−1 at room temperature, which is an advantage of thermoelectric material. These results indicate that CuSbS2 has potential as an environmentally friendly high performance thermoelectric material and provide references for the results of characterization on polycrystalline samples.

Chalcostibite CuSbS 2 has attracted attention as an environmentally friendly material in thermoelectric (TE) field. Our investigations into the TE properties of high-quality p-type CuSbS 2 single crystals revealed that they exhibit a uniquely low thermal conductivity caused by the active lone-pair electrons in Sb 3+ ions. The electrical conductivity was improved by the high density of shallow acceptor Cu vacancies and the absence of potential barriers to carrier transport. Consequently, the figure of merit for the Cu-poor CuSbS 2 single crystal reached 0.5 at 700 K, which is 25 times higher than that of the reported polycrystalline sample.