Incorporating Controlled Porosity in a Cu₂SnSe₃ Material To Enhance Its Thermoelectric Properties

Cu-based ternary structures have attracted substantial interest owing to their cost-effectiveness, widespread availability, and nontoxic characteristics, rendering them highly attractive for thermoelectric applications. Among these structures, Cu2SnSe3 (I2IVVI3) exhibits p-type semiconductor behavior and is considered a prominent thermoelectric material. Despite good electronic transport properties, these materials present very normal thermoelectric performance due to high thermal conductivity which compromises the benefit of high electrical conductivity. One way to reduce thermal conductivity is to introduce controlled porosity in Cu2SnSe3 to overcome this challenge and enhance its thermoelectric performance. Here, we are reporting the fabrication of a porous Cu2SnSe3 structure, in an effort 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 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 pores inside the Cu2SnSe3 matrix act as phonon scattering sites, resulting in a substantial reduction of thermal conductivity from 1.09 to 0.22 W m(-1) K-1 at 548 K. Due to this reduction in thermal conductivity, the Cu2SnSe3 porous structure exhibited a reasonable figure of merit, reaching up to 0.85 at 548 K.