Oxyfluoro-zinc-tellurite glasses – Part I: Predicting the elastic properties and glass transition temperature under the substitution of AlF3 by ZnO

Abstract

An extensive study has been carried out to predict the elastic properties and glass transition temperature of oxyfluoro-zinc-tellurite (10-x)AlF3-xZnO-90TeO2 (1 ≤ x ≤ 9), (30-x)AlF3-xZnO-70TeO2 (5 ≤ x ≤ 25), (35-x)AlF3-xZnO-65TeO2 (10 ≤ x ≤ 30) and (40-x)AlF3-xZnO-60TeO2 (15 ≤ x ≤ 35) glass systems, for the first time. Changes in the elastic moduli, Poisson’s ratio and glass transition temperature due to the substitution of AlF3 by ZnO have been discussed in terms of molar volume, fractal bond connectivity, packing density and dissociation energy per unit volume of the glass. The correlation between theoretically calculated and experimentally measured elastic moduli and Poisson's ratio has also been studied on the basis of Makishima-Mackenzie’s theory and Rocherulle et al. model. The composition dependence of fractal bond connectivity suggested that the studied oxyfluoro-zinc-tellurite glasses have an intermediate dimensionality between three- and two-dimensional structures. Both AlF3 and ZnO are incorporated into the tellurite network as network modifiers. This results is the conversion of TeO4 trigonal bipyramids into TeO3+1 polyhedral and then to TeO3 trigonal pyramids through breaking of TeOTe linkages and creation of non-bridging oxygen atoms. In addition to this, both Makishima-Mackenzie's theory and Rocherulle et al. model appear to be applicable for all the investigated glass systems. The agreement between theoretical and experimental values of elastic moduli and Poisson's ratio is excellent for majority of the samples.