Composition-structure-property relationships in boroaluminosilicate glasses

The complicated structural speciation in boroaluminosilicate glasses leads to a mixed network former effect yielding nonlinear variation in many macroscopic properties as a function of chemical composition. Here we study the composition-structure-property relationships in a series of sodium boroaluminosilicate glasses from peralkaline to peraluminous compositions by substituting Al ₂O ₃ for SiO ₂. Our results reveal a pronounced change in all the measured physical properties (density, elastic moduli, hardness, glass transition temperature, and liquid fragility) around [Al ₂O ₃]-[Na ₂O] = 0. The structural origin of this change is elucidated through nuclear magnetic resonance analyses and topological considerations. Furthermore, we find that addition of 1 mol% Fe ₂O ₃ exerts a complicated impact on the measured properties.