Enhanced Thermoelectric Performance of Mg-Doped AgSbTe by Inhibiting the Formation of AgTe.

The existence of AgTe has always been an obstacle for p-type thermoelectric material AgSbTe to improve its thermoelectric performance. In this work, AgSbMgTe samples are synthesized by melting-slow-cooling and then spark plasma sintering (SPS). Through increasing the solubility of AgTe in the AgSbTe matrix by Mg doping, the formation of AgTe is inhibited. Density functional theory calculations confirm more valence bands are involved in electrical transport due to Mg doping. Therefore, the electrical conductivity of AgSbMgTe samples has been greatly improved due to the reduction of AgTe with n-type electrical conductivity. Moreover, the downward trend of ZT, which is caused by the structural transition of AgTe at about 418 K, disappears. Meanwhile, lattice defects form in the AgSbMgTe 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 AgSbMgTe sample. This study demonstrates that Mg doping can effectively improve AgSbTe thermoelectric performance by inhibiting the formation of the AgTe impurity phase.