Band structure and thermoelectric properties of Al-doped Mg_(3-x)Al_xSb_2 compounds

摘要

Mg3Sb2-based compounds demonstrate promise as thermoelectric materials due to their cost-effectiveness, abundance and high-performance. However, the poor electrical conductivity limits the thermoelectric performance for both p-type and n-type compounds. In this study, Al-doped Mg3-xAlxSb2 samples were successfully fabricated by the high-temperature high-pressure and hot pressing sintering technique. Doping with Al decreased the hole carrier concentration of p-type Mg3Sb2 and transformed the persistent p-type material into an n-type semiconductor with the increase in the Al content to x = 0.2. The Fermi level moved toward the conduction band and the band gap tended to be narrower with the increase in the Al content. The Mg2 site was the most possible location that Al atoms replace. Meanwhile, the lattice thermal conductivity decreased significantly by doped with Al. This study of doping with Al provided an alternative strategy for the enhancement of the thermoelectric properties in n-type Mg3Sb2-based materials.