Enhanced Thermoelectric Performance of P-Type Mg3Sb1.4Bi0.6 Solid Solutions Through Ag Doping

Owing to the unique crystal structure and eco-friendliness of the Zintl-phase Mg 3 Sb 2 compound, it has become a research hotspot in the field of thermoelectric materials. Particularly, the key lies in the optimization of its p-type thermoelectric properties. In this work, Ag doping was implemented in the ternary Mg 3 Sb 1.4 Bi 0.6 matrix, which realized the simultaneous improvement of both the electrical and thermal properties in such materials. At 723 K, the maximum power factor of the Mg 2.99 Ag 0.01 Sb 1.4 Bi 0.6 sample reached 6.8 µW cm −1 K −2 , which was approximately three times that of the undoped sample (~2.3 µW cm −1 K −2 at 723 K). In addition, Ag doping introduced extra lattice disorders and point defects, which enhanced the phonon scattering effect and thus led to a significant suppression of lattice thermal conductivity. Specifically, the Mg 2.96 Ag 0.04 Sb 1.4 Bi 0.6 sample achieved a low lattice thermal conductivity of ~0.47 W m −1 K −1 at 723 K. Ultimately, the peak zT value of the Mg 2.99 Ag 0.01 Sb 1.4 Bi 0.6 sample goes up to 0.68 at 723 K, which was three times higher than that of the undoped sample. This study provides an important reference for subsequent research on optimizing the thermoelectric performance of p-type Mg 3 Sb 2 -based materials.