Direct observation of multiple oxygen sites in oxide glasses: recent advances from triple-quantum magic-angle spinning nuclear magnetic resonance

Triple-quantum, magic-angle spinning nuclear magnetic resonance (3QMAS NMR) on 17O has demonstrated remarkable improvements in resolution among signals from different oxide species in glasses. As many as four separate types of oxygen anion environments can be observed simultaneously in some compositions; Si–O–Si, Al–O–Al, B–O–B, Si–O–Al, Si–O–B, and Al–O–B bridging oxygens can be distinguished and at least roughly quantified; non-bridging oxygens bonded to Si vs. B can in some cases be separated, and there are hints of oxygen tricluster species. These types of data are already providing important new constraints and tests of models of glass structure and properties.