Phase evolution and thermoelectric performance of Cu2SnS3

Cu₂SnS₃ (CTS), as a potential thermoelectric (TE) material, the electrical and thermal transport properties are heavily determined by its original phase structure and the following phase evolution upon heating. Unlike previous studies that induced CTS phase transition by doping, this study used mechanical alloying powder as the precursor and successfully prepared phase-pure cubic (c-) and monoclinic (m-) CTS samples, as well as two-phase mixed samples with different percentage composition of c-CTS and m-CTS, by simply adjusting the hot pressing temperature. Firstly, phase structures of hot-pressed specimens were determined and confirmed by XRD refinement, SEM, TEM, and Raman spectroscopy. Secondly, thermodynamic property was analysis by DSC analysis, and phase evolution was detailed by analyzing specimens quenched at various temperatures. Then, the electrical and thermal transport properties were measured up to 500 °C, and were correlated with phase evolution analyzed above. Benefiting from cationic disorder, a maximum zT of 0.42 at 500 °C was achieved in c-CTS samples hot-pressed at 575 °C. The phase evolution of CTS was comprehensively investigated by using high-quality samples. The results indicate that phase transition is the potential mechanism for the doping effect in most studies, providing some guidance for improving the performance of environmentally friendly TE sulfides.