Density andT _g of glasses of the As-Al-Te system

Abstract

Results of measurement of the density and the glass transition temperature (T _g) on 25 glass compositions of the As-AI-Te system are reported and discussed. A linear increase of density and a decrease ofT _g are seen with increasing As content across the AsAlTe₄- As₂Te₃ tie-line compositions. In the density-composition and mean atomic volume-composition dependences for the As _x ,Al₅Te_95−x , As _x Al₈Te_92−x and As _x Al₁₂Te_88−x glasses, a change in slope is seen at the respective tie-line compositions, indicating chemical ordering in these glasses. When the dependence of density on the average coordination numberZ are considered, the effects of chemical ordering are obscured; instead, the effects of topological nature emerge, with changes in slope at the topological thresholds ofZ≃2.40 andZ≃2.67. The results further indicate that the dependence of mean atomic volumev onZ is controlled by the Te content in these glasses. Due to this, the generally observed features in the dependence ofv onZ for chalcogenide glasses, namely a minimum inv forZ≃2.40, a peak inv forZ≃2.67 and a decrease ofv forZ > 2.67, are suppressed.