Mean atomic volume and Tg of Agx(As0.4Se0.3Te0.3)100-x glasses

Results of measurements of the mean atomic volume (V) and the glass transition temperature (T-g) of twelve Ag-x(As0.4Se0.3Te0.3)(100-x) glasses (with x from 0.3 to 30 atomic percent (at.%)) are reported and discussed. The V-x data has three regions. In regions (i) between x = 0 and 2 and (iii) between x = 3.5 and 30, linear decreases of V with x occur; these regions are separated by a region (ii) between x = 2 and 3.5, in which steeper decrease of V with x is observed. The T-g of these glasses are invariant up to addition of 2 at.% of Ag to the parent As0.4Se0.3Te0.3 glass; for x > 2 at.%, T-g increases with increasing x. Analysis of the data indicate that up to 2 at.%, clusters of Ag atoms occupy interlayer positions in the layered network of the parent glass; up to this stage, they do not affect the medium or short range ordering of the parent glass. For higher concentrations, Ag bonds with the other elements. The V-x and T-g-x data can be rationalized with a model according to which, with progressive increase in Ag, formation of Ag2Te and Ag3AsSe3 structural units takes place in lieu of some of the original As2Te3 and As2Se3 structural units of the parent glass. (C) 1999 Elsevier Science B.V. All rights reserved.