Signature of a silver phase percolation threshold in microscopically phase separated ternary Ge0.15Se0.85−xAgx (⩽x⩽0.20) glasses

Abstract

Temperature modulated alternating differential scanning calorimetric studies show that Se rich Ge 0.15 Se 0.85−x Ag x ͑0 ഛ x ഛ 0.20͒ glasses are microscopically phase separated, containing Ag 2 Se phases embedded in a Ge 0.15 Se 0.85 backbone. With increasing silver concentration, Ag 2 Se 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 microhardness measurements, undertaken in the present study, also strongly support this view of percolation transition. The superionic conduction observed earlier in these glasses at higher silver proportions is likely to be connected with the silver phase percolation.

Structure of Glassy Ag–Ge–Se by Neutron Diffraction with Isotope Substitution

“…In comparison, phase separation into silver-rich and silver-poor glassy phases has been observed for the Ag y (Ge x Se 1−x ) 1−y tie-lines (x = 0.20, 0.25) from scanning electron microscopy (SEM) [11,13,14], electric force microscopy (EFM) [1517] and conductive atomic force microscopy (C-AFM) [16] experiments, but the EFM and C-AFM results indicate a composition for the Ag rich phase that is not constant along a given tie-line. We note that two T g values were also found in MDSC work on samples of composition Ge 0.15 Se 0.85−y Ag y with 0 ≤ y ≤ 0.20 [53]. Multiple glass transitions were not, however, seen in DSC work on Ag y (Ge 0.25 Se 0.75 ) 1−y glasses [8,11,54] or in DSC work on glassy Ag 0.33 (Ge 0.2537 Se 0.7463 ) 0.67 (i.e.…”

Thermal and electrical switching studies on Ge20Se80−xBix (1≤x≤13) ternary chalcogenide glassy system

“…This phenomenon is similar to the percolation in Ag 2 Se phase observed in Ge-Se-Ag glasses, revealed by various experiments such as ADSC [48], electrical switching [49], Raman Scattering measurements [5], etc. The sharp fall in V T and its saturation around x = 6, can be connected with the percolation of the Bi 2 Se 3 phase with Bi addition in the parent glass.…”