The manipulation of substitutional defects for realizing high thermoelectric performance in Mg3Sb2-based Zintl compounds
The introduction of point defects by extrinsic doping is an effective way to optimize the carrier concentration. Here, we show theoretically and experimentally that Pr is a more effective dopant than Te in Mg3Sb2. Using first-principles defect calculations, the predicted highest carrier concentration with Pr doping at 725 K can be up to ∼9.3 × 1019 cm−3, consistent with our experimental measurements. In addition, the point defects introduced by Pr substitution on the Mg sites lead the lattice thermal conductivity to be reduced to as low as 0.429 W m−1 K−1. By optimizing the Pr doping concentration, Mg3.2Pr0.02Sb1.5Bi0.5 exhibits a peak zT value of 1.70 at 725 K.