Study of alkaline metal ions and glass-formers in glasses with advanced NMR methods and quantum mechanic calculations

Silicate, calcium-silicate, and phosphosilicate glasses of the composition 80 SiO2–(20 − x) Na2O − x Me2O (where x = 0, 10 and Me = Li or K), 48.7 SiO2–26.9 CaO–(24.4 − x) Na2O − x Me2O (where x = 0, 12.2 and Me = Li or K), and 46.1 SiO2–2.6 P2O5–26.9 CaO–(24.4 − x) Na2O − x Me2O (where x = 0, 12.2 and Me = Li or K) have been studied with high resolution solid state NMR methods. The quantification of the different Qn species was obtained for each sample by 29Si MAS–NMR analysis. The 23Na MQ-MAS–NMR was used to distinguish the different 23Na sites present in the glasses. The presence of phosphorus in the Na2O phosphosilicate revealed the presence of three Na ionic sites, while the mixed alkali effect resulted in the absence of the third and most ionic site. Quantum mechanical calculations were performed for the identification of the structures observed in our glasses detected by MAS–NMR and MQ-MAS–NMR.