Significantly Enhanced Thermoelectric Performance of -Type MgSb via Zn Substitution on Mg(2) Site: Optimization of Hole Concentration Through Ag Doping.

-Type MgSb-based thermoelectric materials have recently garnered significant interest due to their superior thermoelectric efficiency. Yet, the advancement of -type MgSb for thermoelectric applications is impeded by its lower dimensionless figure of merit (). In this study, we demonstrate the improved thermoelectric performance of -type MgSb through the strategic optimization of Zn content and Ag doping on the Mg/Zn(2) site. Initially, samples of MgZnSb ( = 0, 0.5, 1.0, and 1.5) were synthesized via elemental reactions within a Pyrex tube, followed by densification through hot pressing. X-ray diffraction analysis confirmed that the MgZnSb phases retain the same 1 space group as the pristine MgSb phase. The strategic substitution of Zn improved the power factor via band convergence and reduced lattice thermal conductivity by introducing point defect phonon scattering. This led to a peak of 0.5 at 725 K, with an average of 0.25 across the 325-725 K range. Enhancement in carrier concentration was achieved by doping Ag onto the Zn site, culminating in a peak of 0.95 at 725 K and an average of 0.46 between 325 and 725 K for the MgZnAgSb sample. This performance surpasses that of most -type MgSb-based materials, markedly advancing the potential for MgSb-based materials in midtemperature heat recovery thermoelectric generators.