Effect of silver doping on the structure and phase separation of sulfur-rich As–S glasses: Raman and SEM studies

We report on the structural details and microphase separation of the bulk glasses Ag_x·(As₃₃S₆₇)_100-x for 0x25. Glass–glass phase separation occurs over a wide range of Ag content, i.e. 4x20. An off-resonant polarized Raman spectroscopic study has been carried out to elucidate structural aspects at the short- and medium-range structural order of the glasses. Analysis of Raman spectra revealed quantitative changes of the sulfur-rich microenvironments that reduce upon adding Ag. Scanning electron microscopy combined with X-rays microanalysis have been utilized to examine the type and extent of phase separation, and to provide quantitative details on the atomic concentrations in the Ag-poor and Ag-rich phases. It has been shown that at 7 at.% Ag the Ag-rich phase percolates through the structure; this effect can be associated with an ionic-to-superionic behavior of these glasses in accordance with similar studies on the stoichiometric arsenic sulfide glass; although the phase separation observed in the present glasses is qualitatively different.