Insights into the Iron- and Phosphorus-Induced Structural Rearrangements in Sodium Aluminoborosilicate Glasses and Their Impact on Melt Rheology and Crystallization Behavior

Abstract

This paper presents an insight into the structural rearrangements induced by Fe2O3 and P2O5 in glasses designed in the Na2O–Al2O3–B2O3–SiO2 quaternary system. A suite of state-of-the-art characterization techniques, including magic angle spinning-nuclear magnetic resonance (MAS NMR) (on both iron-free and iron-containing glasses), Raman, and Mössbauer spectroscopies, have been employed to study the structural evolution of glasses as a function of the Fe2O3/Al2O3 ratio and P2O5 content over a broad composition space. It has been shown that while P2O5 tends to repolymerize the structure of Fe2O3-free glasses, it has a minimal impact on the network connectivity of iron-rich glasses. Further, there seems to exist a strong tetrahedral avoidance between AlO4 and FeO4 units in the glass structure. In P2O5-free glasses, iron tends to preferentially bond with borate and silicate units, while in the presence of P2O5, iron prefers to associate with phosphate (over borate and silicate) units in the glass structure. Finally, an attempt has been made to correlate the underlying structural descriptors with the rheological and crystallization behavior of glasses with an overarching goal to establish the composition–structure–property relationships in the investigated glass system.