On the structure of borosilicate glasses: a triple-quantum magic-angle spinning 17O nuclear magnetic resonance study

17O multiple-quantum magic-angle spinning nuclear magnetic resonance (NMR) spectra of borosilicate glasses clearly resolve four oxygen peaks, corresponding to Si–O–Si, B–O–B, Si–O–B and [Si,B]–O–Na linkages respectively. The results suggest that earlier assignment of the B–O–B and Si–O–B resonances is incorrect. In contrast to widely accepted structural models, the high intensity of the Si–O–B resonance demonstrates a much better mixing between the three-coordinated borons and the silica network. The implication of the mixing on the glass structure of other related systems is discussed.