Extending the temperature range of high thermoelectric properties of cuprous sulfide materials

Abstract

Cu-rich cuprous sulfide materials enter the superionic state after high-temperature phase transition and obtain high ZT. In order to improve the average ZT of cuprous sulfide materials, it is necessary to reduce the high-temperature phase transition temperature and extend the temperature range of high ZT. In this study, the sintered Se-alloyed cuprous sulfide blocks were heat treated to vaporize anions, so as to control the relative Cu content of the material. It is found that reducing the Cu content can make the cuprous sulfide material undergo superionic phase transition at lower temperature, so as to extend the high ZT temperature range of the material to the low temperature region and improve the average ZT. Paradoxically, the increase of Cu vacancies will inevitably increase the carrier concentration and carrier thermal conductivity, thereby increasing the total thermal conductivity of the material and reducing ZT. Therefore, only by reasonably controlling the Cu content can we achieve the coordination of low carrier concentration and low superionic phase transition temperature, and improve the average ZT of materials. Based on the experimental results, it is proposed that the effect of increasing the average ZT of cuprous sulfide only by controlling the Cu content is limited. The potential strategies of simultaneously reducing the superionic phase transition temperature and carrier concentration of Cu-rich cuprous sulfide materials to improve their average ZT are prospected.