Enhanced thermoelectric power factor of p-type Mg3Sb2 via co-doping of Si and Fe

Abstract

Mg₃Sb₂-based Zintl compounds are well known as intrinsic p-type narrow bandgap semiconductors which can be considered as promising candidates because of their non-toxic and inexpensive elements. In this study, Mg₃Sb₂ compounds doped with Si and co-doped with Fe and Si have been successfully prepared by the solid phase reaction method (Combination of high-energy ball milling, hot pressing, and sintering). The thermoelectric properties of Si-doped and (Fe, Si) co-doped on the Sb sites of Mg₃Sb₂ compounds were investigated in the temperature range of 300-673K. The secondary phases of SiSb₃ and FeSb were found in the doping samples. The thermoelectric results showed that the electrical conductivity strongly increased in the Si-doped sample, while the additional Fe doping further enhanced the Seebeck coefficient compared to the undoped   Mg₃Sb₂ sample. The highest power factor value was observed in the co-doped Fe, Si sample. The maximum value of the power factor in Mg₃Sb_1.4Fe_0.5Si_0.1 was 1.8 Wcm^-1K^-2 at 673K, which is around ~ 2.2 times higher than that of the undoped sample.