An evidence for a microscopic phase separation in AsSeAg glasses revealed by thermal and structural investigations

Alternating Differential Scanning Calorimetric (ADSC)studies show that Se rich $As_{20}Se_{80-x}Ag_x$(0 \leq x \leq 15) glasses exhibit two endothermic glass transitions and two exothermic crystallization peaks;the observed thermal behavior has been understood on the basis that $As_{20}Se_{80-x}Ag_x$ glasses are microscopically phase separated, containing $Ag_2Se$ phases embedded in an As-Se backbone. With increasing silver concentration, the $Ag_2Se$ phase percolates in the As-Se matrix, with a well-defined percolation threshold at x = 8. A signature of this percolation transition is shown up in the thermal behavior, as sudden jumps in the composition dependence of non-reversing enthalpy, \triangle$H_{nr}$ obtained at the second glass transition reaction. Scanning Electron Microscopic (SEM) studies also confirm the microscopic phase separation in these glasses. The super-ionic conduction observed earlier in these glasses at higher silver proportions, is likely to be associated with the silver phase percolation