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

Abstract

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 κ_L reveals that the unusually low κ_L in Mg₃Sb₂ predominantly originates from the large Grüneisen parameter γ.