Realizing Cd and Ag codoping in p-type Mg3Sb2 toward high thermoelectric performance

Abstract

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.