Incorporating Controlled Porosity in Cu2SnSe3 Chalcogenide for its Enhanced Thermoelectric Performance

Abstract

Cu-based ternary structures have garnered significant attention due to their costeffectiveness, abundant availability, and non-toxic nature, making them appealing for thermoelectric applications. Among these structures, Cu2SnSe3 has emerged as a subject of particular interest, owing to its unique "phonon-glass electron-crystal" (PGEC) configuration, characterized by an open-framework structure interspersed with filler atoms. Despite good electronic transport properties, these materials present very normal thermoelectric performance, due to high thermal conductivity which compromises the benefit of good electrical conductivity. Here we are reporting the fabrication of a porous Cu2SnSe3 structure, in a strive to achieve independent control over thermal conductivity and to decouple the electronic and thermal properties of the material. Cu2SnSe3 was prepared using a ball mill method, followed by the addition of porogen (Hexamine or Bismuth Iodide), and then carried out the densification and sintering. During the sintering process, the sublimation of porogen led to the formation of mixed-type (open and closed) porosity within the material. The porosity inside the Cu2SnSe3 matrix act as phonon scattering sites, resulting in a substantial reduction of thermal conductivity from 1.09 W m-1 K-1 to 0.22 W m-1 K-1 at 548 K. Due to this enhanced phonon scattering, which results in a reduction of thermal conductivity, the thermoelectric material exhibited a reasonable figure of merit (ZT), reaching up to 0.85 at 548 K. This study showcases a remarkably effective approach to enhance the thermoelectric performance of Cu2SnSe3 and similar structures. By successfully decoupling the thermal transport and electrical properties of the Cu2SnSe3 structure, we substantially improved ZT. These findings are important for investigating other related structures, thereby contributing to the advancement of cost-effective and efficient thermoelectric materials for green energy applications.