Al and Sr environment in tectosilicate glasses and melts: Viscosity, Raman and NMR investigation

Structure and properties of SrO-Al2O3-SiO2 glasses and melts were investigated along the tectosilicate join (SrO/Al2O3=1), varying the amount of silica. The structure of the glasses was studied by means of various spectroscopic techniques: Raman, 27Al NMR and XAS at the Sr K-edge. Raman spectroscopy revealed that the fraction of high-membered tetrahedral rings diminishes upon substitution of SiO2 by SrAl2O4 favouring the formation of low-membered rings. Sr K-edge XANES shows that the strontium coordination number is around 9, based on the spectrum similarity with the one obtained for crystalline strontianite. 27Al NMR spectroscopy indicates the presence of four- and five-coordinated aluminium the latter being found in small quantities (