Stoichiometric manipulation to enhance the thermoelectric and mechanical performance of Ag₂Se_1+x

Thermoelectric silver selenide alloys have attracted significant attention owing to their high carrier mobility and promising thermoelectric performance. In this study, the phase diagram window is utilized to synthesize Ag2Se1+x samples within the range of -0.02 <= x <= 0.03. It is found that an excess of Se is helpful to fabricate pure-phase Ag2Se samples at room temperature. Combined with the optimized carrier concentration and reduced thermal conductivity, Ag2Se1.03 sample exhibits an average zT - 0.72 in the temperature range of 310-380 K, as well as a 25 % improvement of the Vickers hardness compared to that of the stoichiometric Ag2Se sample.