Solvothermal synthesis of high-purity porous Cu1.7Se approaching low lattice thermal conductivity

Abstract

Superionic Cu2−xSe has attracted extensive research interest as a promising thermoelectric material with low lattice thermal conductivity (~0.6 W m−1 K−1 at 773 K) and high figure of merit, zT. Here, we demonstrated that β-Cu2−xSe can be synthesized via a facile solvothermal method. By modifying the Cu/Se ratio to control the reaction kinetic condition, impurities, such as Cu2O, Cu and Cu3Se2, can be suspended and in turn lead to high-purity Cu1.7Se. After spark plasma sintering (SPS), porous Cu1.7Se pellet can be sintered and has a relatively low lattice thermal conductivity of ~0.24 W m−1 K−1 at 773 K. From the single parabolic band prediction, a high zT of ~1.6 at 773 K could be realized if the carrier concentration, nH, can be optimized to ~1 × 1020 cm−3 at the same low lattice thermal conductivity. Our study indicates that porous Cu1.7Se is promising to achieve high zT with proper nH-optimization.