Glass structure and electrical conductivity in (As$_2$S$_3$ $_{1-x}$ (Ag$_{2}$S)$_{x}$*

We have synthesized titled glasses in the 0 $<$ x $<$ 0.16 range, and have examined them in modulated DSC experiments. The starting materials, As$_{2}$S$_{3}$ and Ag$_{2}$S lumps, were reacted in evacuated fused quartz tubings, and glasses synthesized by water-quench of homogenized melts. Thermal measurements used a TA instruments model 2920 operated at 3\r{ }C/min scan rate and 1\r{ }C/100s modulation rate. Preliminary results reveal a single glass transition in the 0 $<$ x $<$ 0.05 range, which steadily decrease from a value of 210\r{ }C at x = 0 to 182\r{ } C near x = 0.05. In contrast, bimodal glass transitions are observed at x $>$ 0.09, with one T$_{g}$(1) near 167\r{ }C and the second, T$_{g}$(2) near 186\r{ }C, and with the endotherm associated with T$_{g}$(1) steadily increasing with x. Non-reversing enthalpies associated with T$_{g}$s are found to steadily decrease in the 0 $<$ x $<$ 0.09 range, to nearly vanish in the 0.10 $<$ x $<$ 0.12 range and to increase thereafter ( x $>$ 0.12).These findings suggest that glasses at low x ( $<$ 0.09) are Stressed- rigid, those at x $>$ 0.12 Floppy while those in between in the Intermediate phase$^{1}$. The present results correlate well with earlier$^{2}$ electrical conductivity results in suggesting the possibility of an elastic origin to the conductivity thresholds in solid electrolyte glasses. 1. P. Boolchand, D.Georgiev and B. Goodman, J.Opto {\&} Adm. Mater. 3, 703 (2001). 2. E.A. Kazakova and Z.U.Borisova, Fiz. Khim.Stekla \textbf{6}, 424(1980).