  Temperature modulated Alternating Differential Scanning Calorimetric (ADSC)
studies show that Se rich Ge0.15Se0.85-xAgx (0 <= x <= 0.20) glasses are
microscopically phase separated, containing Ag2Se phases embedded in a
Ge0.15Se0.85 backbone. With increasing silver concentration, Ag2Se phase
percolates in the Ge-Se matrix, with a well-defined percolation threshold at x
= 0.10. A signature of this percolation transition is shown up in the thermal
behavior, as the appearance of two exothermic crystallization peaks. Density,
molar volume and micro-hardness measurements, undertaken in the present study,
also strongly support this view of percolation transition. The super-ionic
conduction observed earlier in these glasses at higher silver proportions, is
likely to be connected with the silver phase percolation.
