Effects of cation doping on thermoelectric properties of Bi2S3 materials

Bi2S3 polycrystals doped with Al, Mn, Ag, and In were fabricated by vacuum melting and plasma activated sintering process, and the phase, microstructure, electrical, and thermal properties were investigated. The electrical conductivity is enhanced via Al and Ag doping. Compared with the Ag dopant, a higher electrical conductivity is achieved in the Al-doped sample, resulting in a peak power factor value of 1.96 μW/cmK2 at 423 K. Meanwhile, the thermal conductivity of Bi1.99Al0.01S3 sample is very low in the Bi2S3 system due to the high-density defects, and is only 0.39 Wm−1 K−1 at 740 K. By combining a power factor and a low thermal conductivity, a peak ZT value of 0.29 at 740 K is achieved in the Bi1.99Al0.01S3 sample, being about two times larger than that of pristine Bi2S3.