Enhanced Thermoelectric Performance of Mg-Doped AgSbTe 2 by Inhibiting the Formation of Ag 2 Te.

The existence of Ag 2 Te has always been an obstacle for p-type thermoelectric material AgSbTe 2 to improve its thermoelectric performance. In this work, AgSb 1- x Mg x Te 2 samples are synthesized by melting-slow-cooling and then spark plasma sintering (SPS). Through increasing the solubility of Ag 2 Te in the AgSbTe 2 matrix by Mg doping, the formation of Ag 2 Te is inhibited. Density functional theory calculations confirm more valence bands are involved in electrical transport due to Mg doping. Therefore, the electrical conductivity of AgSb 1- x Mg x Te 2 samples has been greatly improved due to the reduction of Ag 2 Te with n-type electrical conductivity. Moreover, the downward trend of ZT, which is caused by the structural transition of Ag 2 Te at about 418 K, disappears. Meanwhile, lattice defects form in the AgSb 0.98 Mg 0.02 Te 2 sample, and Mg doping improves the configurational entropy change, resulting in a decrease in lattice thermal conductivity over the entire temperature range of measurement. Finally, a high ZT value of 1.31 at 523 K is achieved for the AgSb 0.98 Mg 0.02 Te 2 sample. This study demonstrates that Mg doping can effectively improve AgSbTe 2 thermoelectric performance by inhibiting the formation of the Ag 2 Te impurity phase.