Optimization strategies for thermal transport properties of n-type Mg₃Sb₂-based thermoelectric alloys

The n-type Mg_3Sb_2-based alloys have attracted considerable attention as promising thermoelectric materials for intermediate-temperature applications, owing to their unique layered crystal structure, suitable bandgap, and intrinsically low thermal conductivity. However, the conversion efficiency of thermoelectric devices fabricated from Mg_3Sb_2-based materials remains relatively low, and further enhancement of the thermoelectric figure of merit zT is essential. Since lattice thermal conductivity is weakly coupled to electrical transport parameters, reducing lattice thermal conductivity has become a key strategy for improving the zT of Mg_3Sb_2-based materials. On the one hand, introducing defects and mass-strain field fluctuations via doping or alloying can significantly enhance phonon scattering and reduce lattice thermal conductivity. Simultaneously, this approach can improve electrical transport properties by tuning the carrier concentration. On the other hand, nano-modification and nanocomposite engineering enable control of grain size and microstructure, enhancing carrier and phonon scattering to reduce thermal conductivity without severely degrading electrical performance. This review summarizes recent progress in optimizing the thermal transport properties of n-type Mg_3Sb_2-based alloys through doping/alloying, nano-modification, nanocomposite formation, and synergistic regulation. These strategies enable a substantial reduction in thermal conductivity while maintaining stable electrical properties, leading to significantly enhanced thermoelectric performance, thus providing scientific and technological support for the application of Mg_3Sb_2-based thermoelectric devices.