N-Type Mg₃Sb₂ (Bi, Te) Alloy Preparation and its Thermoelectric Performance Enhancement

Mg₃Sb₂-based alloys are competitive alternatives to the state of-the-art n-type Bi₂(Te,Se)₃ thermoelectric materials and have been under discussion for the last several years due to their high zT values. However, the poor performance of pure p-type Mg₃Sb₂ due to its poor electrical conductivity is an obstacle for advanced applications. Here the thermoelectric figure of merit is improved by reducing the thermal conductivity of the material produced through high-energy ball milling, without deteriorating other properties. The thermoelectric performance of Mg₃Sb₂-based material is optimized by substituting Te on the Sb site through Bi and Te co-doping in Mg_3.2Sb_1.5-0.5xBi_0.5Te_x with various Te concentrations and the figure of merit is improved from 0.9 to ~ 1.5 at 700 K. The variation in Te concentration has a significant impact on the structural and morphological properties of the material. The density functional theory was employed for the confirmation of the extramental results. This study proposes an efficient route to enhance the thermoelectric performance of n-type Mg₃Sb₂ via Bi and Te co-doping, for future applications of Mg₃Sb₂ based thermoelectric materials.