Challenges and solutions in Mg₃Sb₂-based thermoelectric materials toward applications: thermal stability and the performance-matched p-type

Mg₃Sb₂-based n-type thermoelectric materials have gained considerable interest for both power production and cooling applications because of their high zTs over a wide temperature range, mechanical robustness, and low cost. However, substituting commercial Bi₂Te₃ alloys with Mg₃Sb₂ in real applications remains challenging. On the one hand, the unsatisfactory thermal stability originating from significant Mg loss at high temperatures hinders their large-scale application; on the other hand, an ideal p-type compound with matched thermoelectric performance and thermodynamic properties has not been reported, making it difficult to construct a thermally reliable and low-cost thermoelectric module. In order to solve these issues, we first developed a simple cation-site doping strategy to enhance the thermal stability of n-type Mg₃Sb₂ through the suppression of Mg vacancy formation. Second, a high zT of 0.7 was achieved in p-type Mg₃Sb₂, allowing the construction of an all Mg₃Sb₂-based unicouple with a maximum conversion efficiency of 5.5% at the hot-side temperature of 573 K. Given the enhanced thermal stability and high performance of p- and n-type compounds, Mg₃Sb₂-based materials are promising candidates for next-generation thermoelectric devices.