High thermoelectric performance of Bi_1−x K _x CuSeO prepared by combustion synthesis

A series of K-doped Bi_1−x K _x CuSeO (0 ≤ x ≤ 0.10) compounds were prepared by combustion synthesis combined with spark plasma sintering method. Phase composition and microstructure analysis indicate almost single BiCuSeO phase in low doping level, while phase separation appears in heavy doping level. The thermoelectric properties of the Bi_1−x K _x CuSeO compounds have been measured in the temperature range of 323–823 K. The electrical conductivity is greatly enhanced by almost three times from 8.70 to 26.2 S/cm at 323 K by the substitution of Bi with K due to the large decrease of the activation energy. The overall thermal conductivity decreases significantly due to the strong point defect scattering by K doping and possibly enhanced interface scattering on the secondary phase. The maximum ZT reaches 0.6 at 823 K for the sample of x = 0.02, which is about 50% higher than that of the pristine sample. Our work offers a fast and more efficient approach for the fabrication of BiCuSeO-based materials.