• • Annealing transforms the as-prepared Ag2S0.4Te0.6 powder from a predominantly amorphous state (with only trace poorly crystalline monoclinic phase) into a mixed cubic crystalline/amorphous state at room temperature, eliminating observable phase transitions upon subsequent heating from 110 K to 700 K.
• • In situ synchrotron radiation powder X-ray diffraction (SPXRD) reveals that unannealed powder undergoes a crystallization sequence: amorphous → monoclinic → mixed bcc+fcc phases upon heating, whereas annealed powder remains stable in the mixed cubic/amorphous state across the entire temperature range.
• • High-resolution transmission electron microscopy (HRTEM) confirms the coexistence of cubic crystallites and amorphous matrix in annealed powder, providing direct microstructural evidence for the enhanced ductility.
• • Annealing does not degrade the thermoelectric performance of bulk Ag2S0.4Te0.6, as the Seebeck coefficient, electrical conductivity, and thermal conductivity remain largely unchanged, ensuring that the ductility improvement is achieved without compromising functional properties.