Enhancement of thermoelectric power factor in Si-doped Mg3Sb2 compoundfor 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 Mg3Sb2-xSix to improve the electrical conductivity of doping samples while maintaining a high value of the Seebeck coefficient. The results exhibited that Mg3Sb2 and Mg3Sb2-xSixcompounds 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 Mg3Sb1.75Si0.25 sample. The power factor of all doping samples increased compared to undoped samples. The power factor values at 673K of Mg3Sb1.9Si0.1, Mg3Sb1.75Si0.25, and Mg3Sb1.7Si0.3 increased around 1.7 times compared to the Mg3Sb2