Realizing High Thermoelectric Performance in N‐Type Mg₃(Sb, Bi)₂‐Based Materials via Synergetic Mo Addition and Sb–Bi Ratio Refining

Abstract Developing thermoelectric (TE) performance is impeded by the compromise of TE parameters, resulting in inadequate conversion efficiency of heat to electricity. Herein, this work reports that Mo is a particularly effective additive in Mg₃Sb₂‐based alloys with significantly improved electronic transport via grain‐boundary engineering and band‐structure regulation synergy. In addition, phonon transport is simultaneously suppressed by employing multiple effects, lattice imperfection scattering, reduced phonon group velocity, and enhanced atomic disorder, leading to a minimum κ_lat = 0.52 W m⁻¹ K⁻¹ at 723 K. As a result, an outstanding ZT peak of ≈1.84 at 723 K and ZT_av = 1.34 within 323–723 K are achieved in Mg₃Sb₂‐based alloys, and the corresponding fabricated single‐leg TE module shows an exceptionally high conversion efficiency of ≈12% under a hot‐side temperature of 450 °C. These results demonstrate the great potential for advancing mid‐temperature heat harvesting in Mg₃Sb₂‐based materials.