A critical evaluation of barium silicate glass network polymerization

The state of polymerization in barium silicate glasses (xBaO.(1-x)SiO2 , 0.28 <= x <= 0.45) has been studied by both experiment (Raman, static and MAS Si-29 NMR spectroscopy) and molecular dynamics simulations (VashishtaRahman and Du-Cormack potentials). No a priori assumptions were made about the number of Qn species, specific mean polymerization nor presence or absence of 'free' oxygen species. This allowed us to test the relationships between these structural aspects.& nbsp;The Q(n) site interconversion equilibrium constants K-Q2 and K-Q3 were found to be 0.07 and 0.05 +/- 0.02 from static 29Si NMR, and 0.14 & PLUSMN;0.07 and 0.07 & PLUSMN;0.01 from 29Si MAS NMR, respectively.The Qn species distribution was used to determine the Raman scattering cross-sections for Q(1) , Q(2) and Q(3) as 1.01 +/- 0.15, ~1.1, and 1.14 & PLUSMN;0.04, respectively, although some compositional dependence was found. The Q4 cross-section displays a unique behavior approaching 0 at 38% BaO. This more accurate structural framework paves the way for future studies to establish meaningful structure-property relationships for these glasses.

Automated summary

The state of polymerization in barium silicate glasses was investigated using experimental techniques and molecular dynamics simulations. The study provided a more accurate structural framework and laid the foundation for future research on structure-property relationships of these glasses.