Enhancing thermoelectric performance of Sn0.5Ge0.5Te via doping with In/Zn, In/Sb and In/Bi

Tin germanium tellurides, (SnGe)Te, are developed as a potential substitute for the lead telluride (PbTe) for thermoelectric power generation. SnTe and PbTe share similar crystal and electronic structures, however, SnTe has a much higher lattice thermal conductivity and a much lower Seebeck coefficient. Alloying SnTe with Ge and doping with other elements significantly improves its performance. This work provides a comparative study of the thermoelectric properties for the Sn0.5Ge0.5Te phases doped with In, and subsequently with Zn, Sb and Bi. The In doping on the Sn/Ge site induces resonant levels around the Fermi level, and thus, enhances the thermopower. Further doping with Sb and Bi in (Sn0.5Ge0.5)0.98In0.2Te leads to the valence band convergence (thus increasing the thermopower) and also optimizes the thermal conductivity. Comparison of the results for (Sn0.5Ge0.5)0.89In0.02Bi0.06Te and pristine SnTe reveal significant improvements in the average and highest ZT values by 446% (0.71 vs. 0.13) and 125% (0.80 vs. 0.36), respectively, within 100–500 ​°C.