Speciation and polymerization in a barium silicate glass: Evidence from 29Si NMR and Raman spectroscopies

Raman and NMR spectroscopies have long been employed in pursuing quantitative relationships between polymerization of silicate glasses and melts. However, varying assumptions and ambiguities have often meant structural models vary significantly depending on the probe used. This study investigates a 40BaO center dot 60SiO(2) glass to determine its polymerization using static and MAS Si-29 NMR, and Raman spectroscopies to construct a coherent structural interpretation. The challenges and advantages of each technique are discussed as the structural model of 40BaO-60SiO(2) glass required partial evidence derived from each of these spectroscopies. The Raman scattering cross sections for Q(2) and Q(3) were found to be 0.85 and 1.22, respectively. The Q(n) distribution was shown to be 3, 35, 57, 6% (+/- 4%) for Q(1) to Q(4), respectively. This distribution yields a polymerization consistent with the stoichiometry, Ba0.66SiO2.66, having a O:Si ratio of 2.66. The agreement between all Q(n) distributions, the composition, the polymerization, and equilibrium constants strongly indicate that this structural interpretation is robust.

Automated summary

Raman and NMR spectroscopies have been used to study the polymerization of silicate glasses, with this study showing that the structural interpretation of 40BaO-60SiO(2) glass was robust by combining evidence from both techniques. The distribution of Q(n) and composition of the glass support the stoichiometry Ba0.66SiO2.66, indicating a consistent level of polymerization.