Thermoelectric performance improvement of p-type Mg3Sb2-based materials by Zn and Ag co-doping

Mg3Sb2-based Zintl compounds have attracted extensive attention as potential thermoelectric materials due to their earth-abundant elements. However, pure and intrinsic p-type Mg3Sb2 manifests a poor thermoelectric performance because of its high electrical resistivity. It is reported that Ag doping in Mg sites can increase the mobility and carrier concentration of p-type Mg3Sb2; however, high thermal conductivity still limits the improvement of the ZT value. In the present work, Zn and Ag co-doping in Mg sites was carried out to optimize the thermoelectric performance of p-type Mg3Sb2. Experimental results revealed that the carrier concentration and mobility of Mg3Ag0.01Sb2 significantly increased after Zn doping, leading to an improvement of the power factor. Simultaneously, lattice thermal conductivity was significantly reduced due to the large mass difference between Zn and Mg. The Mg2.39Zn0.6Ag0.01Sb2 sample with an optimal doping concentration of 3.95 × 1019 cm−3 achieved a maximum ZT value of 0.84 at 773 K. Hence, Zn and Ag co-doping is an effective method to improve the thermoelectric performance of p-type Mg3Sb2. [Display omitted] •Zn and Ag co-doping was carried out to optimize the thermoelectric performance of p-type Mg3Sb2.•The optimal carrier concentration of Mg3Ag0.01Sb2 is about 3.95 × 1019 cm−3.•The power factor of Mg3Sb2 was significantly enhanced after Zn and Ag co-doping.•The lattice thermal conductivity was reduced after Zn and Ag co-doping in Mg3Sb2.•Mg2.39Zn0.6Ag0.01Sb2 achieved a maximum ZT value of 0.84 at 773 K.