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

Abstract.

Alternating Differential Scanning Calorimetric (ADSC) studies show that Se rich As₂₀Se_80-xAg_x (0 ≤ x ≤ 15) glasses exhibit two endothermic glass transitions and two exothermic crystallization peaks; the observed thermal behavior has been understood on the basis that As₂₀Se_80-xAg_x glasses are microscopically phase separated, containing Ag₂Se phases embedded in an As-Se backbone. With increasing silver concentration, the Ag₂Se 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, ΔH_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.