Realizing Cd and Ag codoping in p-type Mg3Sb2 toward high thermoelectric performance
Shijuan Xiao, Kunling Peng, Zizhen Zhou, Huan Wang, Sikang Zheng, Xu Lu, Guang Han, Guoyu Wang, Xiaoyuan Zhou
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.