Largely Optimized Thermoelectric Performance in (Ag, S) Coalloyed CuTe Thermoelectric Materials.

CuTe-based compounds are expected to exhibit superior thermoelectric performance compared to CuS and CuSe due to the larger atomic mass and more covalent bonding of Te atoms, such as chalcogenide selenide and chalcogenide lead. However, the currently reported figure of merit () for CuTe is still lower than that of CuS and CuSe. In this work, the thermoelectric transport properties are studied and optimized by two-step coalloying of CuTe-based materials. An improved average power factor of 7.21 μW cm K is obtained between room temperature and 773 K because of the largely optimized carrier concentration and Seebeck coefficient. Additionally, the total thermal conductivity decreases to 0.55 W m K for AgCuTeS W m K at room temperature, and the lowest thermal conductivity of 0.49 W m K is obtained in AgCuTeS at 523 K because of the tuned carrier concentration and increased entropy. Combined with the simultaneous optimization of electrical transport properties and thermal transport properties, (Ag, S) coalloyed CuTe shows a maximum of 1.4 at 773 K, which is 460% higher than that of CuTe at the corresponding temperature.