Effects of Bi doping on the electrical and thermal transport properties of Cu2SnSe3

Abstract

In the study, we deal with the effects of Bi doping on the thermoelectric properties in a series of Cu2Sn1-xBixSe3 (x = 0, 0.02, 0.04, 0.06, 0.08, 0.10) compounds. The pristine and Bi-doped Cu2SnSe3 samples are synthesized by the solid-state sintering technique. Cubic structure with F4‾3m space group is maintained for all the samples. FESEM analysis indicated that the average grain size increases with an increase in Bi concentration. It is found that the characteristics of electrical resistivity changes from semiconducting in the case of the pristine sample to metallic behavior for the doped samples. The decrease in both electrical resistivity (ρ) and the Seebeck coefficient (S) with an increase in x is attributed to the increased hole concentration. The highest power factor (PF) of ~348 μW/mK2 has been achieved for the x = 0.08 sample at 350 K, which is four times larger than that of the pristine sample. The thermal conductivity (κ) of the doped samples is observed to be higher than that of the pristine Cu2SnSe3, attributed to the increased grain size and electronic thermal conductivity. As a combined effect on the values of PF (= S2/ρ) and thermal conductivity, a maximum figure-of-merit (ZT) of ~0.027 for the x = 0.08 sample is attained at 350 K, about twice that of the pristine sample.