Enhancement of Thermoelectric Performance in Mg₃(Sb, Bi)₂ via Dual Doping of Cations and Anions

N-type Mg₃(Bi, Sb)₂ alloys exhibit great potential for waste-heat harvesting applications due to their excellent thermoelectric performance, lightweight nature, and the abundance and low cost of their constituent elements. This work presents a cation-anion (Lu-Se) co-doping strategy in Mg₃(Bi, Sb)₂ materials, which effectively enhances their thermoelectric properties. The electrical conductivity is significantly increased by the dual doping effect, resulting in a high power factor of 27 µW cm⁻¹ K⁻². Meanwhile, the lattice thermal conductivity is significantly reduced due to the enhanced phonon scattering caused by mass fluctuations and stress-field fluctuations, resulting from the two types of atoms, as well as the reduced grain size. Ultimately, a high thermoelectric figure of merit (zT) of ≈1.06 is achieved in (Lu, Se)-co-doped Mg₃Sb_1.5Bi_0.5 at 498 K. Furthermore, a module composed of n-type (Lu, Se)-co-doped Mg₃Sb_1.5Bi_0.5 and p-type BiSbTe exhibits superior power generation performance, achieving a maximum efficiency of 8% and a maximum output power of 0.46 W at a temperature difference of 280 K, which is at the forefront level. This work provides an effective and low-cost route to harnessing the potential applications of n-type Mg₃(Bi, Sb)₂ thermoelectric materials.