Enhancement of thermoelectric power factor in Si-doped Mg3 Sb2 compound for thermoelectric converting applications

Abstract

Mg₃Sb₂ is a narrow band gap semiconductor with electrical conductivity and thermoelectric properties dependent on structure and doping elements. In this study, to improve the thermoelectric properties of Mg₃Sb₂, the authors doped Si at different ratios (x=0.05, 0.1, 0.15, 0.25, and 0.3) into Sb sites as the formula Mg₃Sb_2-xSi_x to improve the electrical conductivity of doping samples while maintaining a high value of the Seebeck coefficient. The results exhibited that Mg₃Sb₂ and Mg₃Sb_2-xSi_x compounds prepared by solid phase reaction method (high energy grinding combined with hot pressing and sintering) showed hexagonal structure. The electrical conductivity of the Si-doped samples increased significantly compared to the undoped Mg₃Sb₂ sample, while the Seebeck coefficient slightly decreased in the low doping contents samples and highest increase in the Mg₃Sb_1.75Si_0.25 sample. The power factor of all doping samples increased compared to undoped samples. The power factor values at 673K of Mg₃Sb_1.9Si_0.1, Mg₃Sb_1.75Si_0.25, and Mg₃Sb_1.7Si_0.3 increased around 1.7 times compared to the Mg₃Sb₂.