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Mg3Sb2 has attracted intensive attention as a typical Zintl-type thermoelectric material. Despite the exceptional thermoelectric performance in n-type Mg3Sb2, the dimensionless figure of merit (zT) of p-type Mg3Sb2 remains lower than 1, which is mainly attributed to its inferior electrical properties. Herein, we synergistically optimize the thermoelectric properties of p-type Mg3Sb2 materials via codoping of Cd and Ag, which were synthesized by high-energy ball milling combined with hot pressing. It is found that Cd doping not only increases the carrier mobility of p-type Mg3Sb2, but also diminishes its thermal conductivity (κtot), with Mg2.85Cd0.5Sb2 achieving a low κtot value of ∼0.67 W m−1 K−1 at room temperature. Further Ag doping elevates the carrier concentration, so that the power factor is optimized over the entire temperature range. Eventually, a peak zT of ∼0.75 at 773 K and an excellent average zT of ∼0.41 over 300 − 773 K are obtained in Mg2.82Ag0.03Cd0.5Sb2, which are ∼240% and ∼490% higher than those of pristine Mg3.4Sb2, respectively. This study provides an effective pathway to synergistically improve the thermoelectric performance of p-type Mg3Sb2 by codoping Cd and Ag, which is beneficial to the future applications of Mg3Sb2-based thermoelectric materials.

Magnesium-based materials have been regarded as promising candidates for large-scale, high-efficiency thermoelectric applications, owing to their excellent dimensionless figure of merit, high abundance, and low cost. In this review, we comprehensively summarize the recent advances of Mg-based thermoelectrics, including Mg2X (X = Si, Ge, Sn), Mg3(Sb,Bi)2, and α-MgAgSb, from both material and device level. Their electrical and thermal transport properties are first elucidated based on the crystallographic characteristics, band structures, and phonon dispersions. We then review the optimization strategies towards higher thermoelectric performance, as well as the device applications of Mg-based thermoelectric materials and the related engineering issues. By highlighting the challenges and possible solutions in the end, this review intends to offer perspectives on the future research work to further enhance the performance of Mg-based materials for practical applications.