Bridging oxygen speciation and free oxygen (O2 −) in K-silicate glasses: Implications for spectroscopic studies and glass structure

A 2D 29Si MAF NMR spectrum of K-disilicate glass indicates that two Q4 contributions are present in the spectrum, as previously observed in highly siliceous K-silicate glasses. One explanation for two peaks is that one Q4 signal represents Q4 tetrahedra attached to Q3 tetrahedra and the second peak represents Q4 attached to other Q4 species. An alternative explanation is offered based on these findings. The two Q4 signals may result from different types of BO-K moieties bonded to Si centers of Q4 species. K+, located in the second coordination sphere of BO, modifies the electronic (valence band) properties of the BO and Si atoms of the tetrahedron, thereby producing two Q4 signals. The 2D 29Si MAF NMR, 17O NMR and O 1s XPS spectra indicate ~ 2 (± 1) mol% O2 − in the K-disilicate glass. These three types of spectra yield remarkably similar results when high resolution spectra are collected and complete fitting of the spectra are performed.