The Relation between the Electronic Structure and Thermoelectric Properties for Zintl Compounds Mg3Sb2

The electronic structure and the thermoelectric properties of Mg3Sb2 are studied by the first principles and the semiclassical BoltzTraP theory. Mg3Sb2 is semiconductor with an indirect band gap with the TB-mBJ, which is is closer to the experimental results. The higher absolute S values for n-type doping than that for p-type doping are mainly due to the larger band degeneracy at the bottom of the conduction band. The s of n-type Mg3Sb2 are larger than that of the p-type ones, due to the large conduction band dispersion near the Fermi level. Obviously, the larger ZT of n-type Mg3Sb2 mainly comes from its larger Seebeck coefficient and its larger s. For n-type Mg3Sb2, the ZT along the x-direction is larger than those along the z-direction. The anisotropy of ZT results show that it proved again the thermoelectric thin films with excellent performance can be obtained along the (100) and (010) surface.