Effect of Ag Vacancies on the Mechanical Properties of Ag2S Thermoelectric Semiconductor

Ag vacancies have been shown to regulate the thermoelectric properties of Ag₂S. However, their effect on the mechanical properties of Ag₂S remains unclear. In this study, Ag₂S-based samples with various Ag vacancy concentration were prepared, and their mechanical properties were investigated experimentally and theoretically. Both the bending strength and fracture strain decrease with increasing Ag vacancy concentration. Moreover, the dimple size on the fracture surfaces of the samples gradually reduces with increasing Ag vacancy concentration, further confirming the reduction in material ductility. Density functional theory results reveal that Ag vacancies lead to the disruption of Ag–S bonds in Ag₂S at low ultimate strains, consequently causing a simultaneous reduction in both strength and deformability, which agrees reasonably well with the experimental observations. This work provides new insights into the effect of vacancies on the mechanical properties of Ag₂S materials, which could guide the design of fast ionic thermoelectric materials.