Tuning the thermoelectric properties by manipulating copper in Cu2SnSe3 system

Cu2+xSnSe3 (0 <= x <= 0.08) compounds were synthesized by conventional solid-state reaction followed by spark plasma sintering (SPS) technique. Transport properties of the samples were measured as a function of temperature in the temperature range 323-773 K. As compared to Cu2SnSe3 sample, the electrical resistivity (rho) is increased for the sample with x = 0.04, thereafter a decrease is seen with further increase in copper content. Analysis of electrical resistivity indicates that small poloron hoping model is operative in the entire temperature range for all samples. The positive Seebeck coefficient (S) for the samples in the entire temperature range indicates that the majority charge carriers are holes. The highest figure of merit, ZT (= 0.32) was achieved at 773 K for the sample Cu2.06SnSe3 which is about 3 times that of Cu2SnSe3 sample. Maximum thermoelectric compatibility factor (1.28 V-1) was observed at 673 K for the sample Cu2.08SnSe