Thermoelectric properties and thermal stability of Cd-doped Cu2Se thermoelectric materials

It work provides a simple and effective doping strategy to obtain high-temperature cycle service stability of Cu2Se-based thermoelectric materials while maintaining their intrinsic excellent thermoelectric properties. Cu2-xCdxSe (x = 0, 0.02, 0.04, and 0.06) block materials were synthesized by vacuum melting annealing and spark plasma sintering (SPS). The effects of Cd doping on the composition, microstructure, band structure, and thermoelectric properties of Cu2Se were investigated. The development of Cd doping on the thermoelectric stability of Cu2Se was studied by four high-temperature cycles. The results show that Cd doping can reduce Cu + migration and improve its thermoelectric stability. The dissolution of Cd in Cu2Se is limited, and a second phase of CdSe is found in samples with high Cd content (x = 0.04 and 0.06). The second phase CdSe and element segregation (copper-rich phase) in the x = 0.06 sample enhance phonon scattering and reduce lattice thermal conductivity (κl). Therefore, the maximum ZT value of the Cu1.94Cd0.06Se sample at 873K (about 1.37) is about 1.02 times higher than that of the undoped sample (about 1.34). The research will accelerate the practical application of liquid thermoelectric materials and provide the possibility of Cu2Se series thermoelectric materials in the use of waste heat power generation in the middle-temperature area, which has great application prospects.