Structure of MgO/CaO sodium aluminosilicate glasses: Raman spectroscopy study

Understanding the composition dependence of the atomic structure of multicomponent aluminosilicate glasses is a challenging problem. Aluminum has a crucial influence on the structure-property relations in these systems, but there are still questions regarding its local structural environment. Here, we present results detailing the network structure of twenty quaternary MgO/CaO-Na₂O-Al₂O₃-SiO₂ glasses upon Al₂O₃-for-SiO₂ and MgO-for-CaO substitutions using room temperature and in situ high-temperature Raman spectroscopy. The Raman spectra reveal that the Mg-containing glasses violate the Al-avoidance at lower Al₂O₃ concentration than the Ca-containing glasses. Furthermore, the alkaline earth ions acting as charge-compensators for tetrahedral aluminum are found to have a similar effect on the network structure (Qⁿ speciation and Al/Si mixing), while they affect the network differently when they are in a modifying role. Increasing cation field strength allows for stabilization of networks with a larger distribution of bond angles.