Mean atomic volume and Tg of Cu−Ge−As−Se glasses

Results of measurements of the mean atomic volume (V), the glass transition temperature (Tg) and the activation energy for glass transition (Et) are reported for 11 glass compositions of the Cu-Ge-As-Se system. The compositions studied can be represented as Cux(Ge0.125As0.25Se0.625)100-x glasses. In the V-x, Tg-x and the Et-x data of these glasses, changes in slope are observed at an x value of approximately 2. The results are consistent with a picture wherein, up to approximately 2 atomic percent (at.%), Cu atoms occupy interlayer positions between the uncorrelated layers of the parent glass matrix without affecting either the medium or the short range ordering of the parent glass. The results also suggest that up to approximately 2 at.%, Cu atoms act as `plasticizers' in the parent glass matrix, reducing its Tg.