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

O-17 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. (C) 1998 Elsevier Science B.V. All rights reserved.