Computational prediction of a high ZT of n-type Mg3Sb2-based compounds with isotropic thermoelectric conduction performance

N-type Mg3Sb2-based Zintl compounds are proved to be high-performance thermoelectric materials with multiple degenerate valleys and low lattice thermal conductivity. Here, we investigate the electronic band structure and the thermoelectric properties of n-type Mg3Sb2 using first-principles density functional theory. A high ZT of 3.1 at 725 K is obtained when the minimum lattice thermal conductivity and the optimal carrier concentration are reached. The calculated thermoelectric performance demonstrates that Mg3Sb2 possesses an isotropic character in thermoelectric transport. Furthermore, the calculated lattice thermal conductivity κL reveals that the unusually low κL in Mg3Sb2 predominantly originates from the large Grüneisen parameter γ.