Thermoelectric performance of Cu2Se bulk materials by high-temperature and high-pressure synthesis

Polycrystalline Cu2Se bulk materials were synthesized by high-pressure and high-temperature (HPHT) technique. The effects of synthetic temperature and pressure on the thermoelectric properties of Cu2Se materials were investigated. The results indicate that both synthetic temperature and pressure determine the microstructure and thermoelectric performance of Cu2Se compounds. The increase of synthetic temperature can effectively enhance the electrical conductivity and decrease the lattice thermal conductivity. A two-fold improvement in the power factor is obtained at synthetic temperature of 1000 °C compared to that obtained at room temperature. All β-Cu2Se samples exhibit low and temperature-independent lattice thermal conductivity ranging from 0.3 to 0.5 Wm−1K−1 due to the intrinsic superionic feature and the abundant lattice defects produced at high pressure. A maximum zT of 1.19 at 723 K was obtained for the sample synthesized at 3 GPa and 1000 °C. These findings indicate that HPHT technology is an efficient approach to synthesize Cu2Se-based bulk materials.