Balancing the anionic framework polarity for enhanced thermoelectric performance in YbMg₂Sb₂ Zintl compounds

1-2-2-type Zintl phase compound has aroused great interest for potential thermoelectric applications. However, YbMg₂Sb₂ is seldom studied due to the very low electrical conductivity resulting from the large difference in the electronegativity between Mg and Sb. In this paper, we adjust the covalently bonded network of Mg[sbnd]Sb by replacing part of the Mg with Zn which has the electronegativity closer to that of Sb. The decreased polarity in the anionic framework offers more free distance for electrons for the enhanced Hall mobility and electrical conductivity. Together with the increased point defect and the decreased lattice thermal conductivity by introduction of Zn, the maximum ZT value of ∼0.8 at 773 K is achieved in YbMg_0.9Zn_1.1Sb₂ which is ∼100% enhancement compared with that of YbMg₂Sb₂.