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 MgeSb 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 YbMg0.9Zn1.1Sb2 which is ~100% enhancement compared with that of YbMg2Sb2.