Topological Constraint Model of Alkaline Earth Vanadate Glasses

TL;DR

This paper develops a topological constraint model for alkaline earth vanadate glasses, linking structural units to thermal and mechanical properties, and explaining network rigidity and anomalies through experimental validation.

Contribution

It introduces a novel topological constraint model specific to alkaline earth vanadate glasses, incorporating temperature dependence and structural anomalies.

Findings

Bridging oxygen constraints dominate network rigidity.

Vanadate networks remain highly connected despite modifiers.

Magnesium can form locally rigid structures.

Abstract

Topological constraint theory has enabled the successful prediction of glass properties over a wide range of compositions. In this study, a topological constraint model is constructed for alkaline earth vanadate glasses based on experimental data. The change in vanadate structural units from VO5 to VO4 was modeled as a function of alkaline earth content and related to thermal and mechanical properties. The model covers both high and low-temperature properties to probe the temperature dependence of constraint rigidity for each constituent of the glass network. The model is changed to describe anomalies in magnesium sites potentially implying that magnesium can form locally rigid structures. Furthermore, the traditional understanding of vanadate glass structure is compared to recent results concluding that the terminal oxygen must exist as a part of the VO4 units. Results for the model explain that bridging oxygen constraints are the main contributors to network rigidity in both low and high temperature regimes. Vanadate glass networks are highly connected even with the introduction of modifier species, which introduce their own bond constraints. Corroboration between experimental data and the topological constraint model illustrates the role of alkaline earth oxides in the glass network.