Fast synthesis and improved electrical stability in n-type Ag2Te thermoelectric materials

Cu- and Ag-based superionic conductors are promising thermoelectric materials due to their good electrical properties and intrinsically low thermal conductivity. However, the poor electrical and thermal stability restrict their application. In this work, n-type pure phase Ag2Te compound is synthesized by simply grinding elemental powders at room temperature and compacted by spark plasma sintering. It is found that, because of the migration of Ag+ after the phase transition around 425 K, submicron pores are formed inside the samples during the electrical performance measurement, resulting in poor electrical stability and repeatability of Ag2Te samples. However, Pb-doped Ag2-xPbxTe (x = 0–0.05) specimens exhibit improved electrical stability by the precipitation of the secondary phase PbTe in the Ag2Te matrix, which is confirmed via cyclic electrical property measurement and microstructure characterization. A maximum zT = 0.72 is obtained at 570 K for x = 0.03 mainly due to the increased power factor.