Robust Room Temperature Thermoelectric Performance of Mg₃(Sb, Bi)₂‐Based Alloys via Multivalent Mn Doping

Abstractn‐type Mg3(Sb, Bi)2 has excellent room temperature thermoelectric performance, which is, however, severely restricted by the negatively charged Mg vacancies that significantly deteriorate the carrier mobility. Herein, by manipulating the threshold solubility and defect formation energy of Mn, multivalent Mn is selectively introduced that synergistically promotes the carrier conduction according to different Mg chemical potentials; In Mg‐rich areas, interstitial Mn dominates which effectively reduces the migration and accumulation of Mg vacancies, while in Mg poor areas, interstitial Mn switches to substitutional sites that directly compensate for the negative charge. All the Mn centers possess Jahn–Teller inactive positions, leading to an ultra‐stable room temperature thermoelectric performance with a leading ZT up to 0.97. This work reveals the critical effect of multivalent and multifunctional transition metal incorporation in Mg3(Sb, Bi)2‐based alloys toward high room‐temperature thermoelectric performance.