Effect of Ag deficiency on the mechanical and thermoelectric properties of Ag2S0.7Te0.3

Ag2(S,Te) solid solutions are promising thermoelectric materials because they have metal-like ductility and decent thermoelectric performance. However, the mechanical and thermoelectric properties of Ag2(S,Te) solid solutions are highly sensitive to chemical composition. In this work, taking Ag2S0.7Te0.3 as an example, we systematically investigate the effect of Ag deficiency on its mechanical and thermoelectric properties. Introducing slight Ag deficiency in Ag2S0.7Te0.3 induces the formation of the Ag2S-based monoclinic phase and reduces the content of the amorphous phase. The Ag-deficient Ag1.995S0.7Te0.3 exhibits a higher zT because the changes in phase composition and electrical conductivity reduce the total thermal conductivity, but it has poorer ductility than Ag2S0.7Te0.3 due to the difficulty of coherent deformation between the amorphous phase and the monoclinic phase. This work sheds light on the further investigation of Ag2(S,Te) solid solutions.