Evaluation of Processing Parameters in the Solvothermal Synthesis of Cu-Rich Tetrahedrites for Potential Application as Thermoelectric Materials

The major issue associated with thermoelectric performance is the low efficiency of power conversion. The main challenge is achieving a combination of high Seebeck coefficient, high electrical conductivity, and low thermal conductivity for a significantly improved figure of merit (ZT). Developing strategies include the production of tetrahedrites with an intrinsically low thermal conductivity through the solvothermal method, using a low reaction time and processing temperature. Here, we report on the preparation of Cu-rich tetrahedrites through the solvothermal technique at low temperature, providing a promising strategy for the preparation of materials with potential applications in thermoelectricity. The influence of synthesis reaction time and temperature on the morphological, structural, and thermoelectrical properties of the samples was investigated through different characterization techniques. Tetrahedrite synthesized at 180 °C for 19 h yielded a favorable ZT value of >0.43 and a thermal conductivity of 0.2 Wm−1 K−1 (423 K), related to the Sb3+/Sb5+ and Cu+/Cu2+ ratio, as was observed by XPS. The cubic tetrahedrite phase attributed to the (222) plane was confirmed by XRD and TEM and the intense Raman mode observed at 351 cm−1. SEM images revealed that nanotetrahedral Cu-rich tetrahedrites efficiently assemble into spherical structures, resulting in an improvement in the Seebeck coefficient (437 µVK−1) and electrical conductivity.