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

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

Superionic Cu2−xSe has attracted extensive research interest as a promising thermoelectric material with low lattice thermal conductivity (~0.6Wm−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 highpurity Cu1.7Se. After spark plasma sintering (SPS), porous Cu1.7Se pellet can be sintered and has a relatively low lattice thermal conductivity of ~0.24Wm−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.