CATION EFFECTS ON P-31 MAS NMR CHEMICAL-SHIFTS OF METAPHOSPHATE GLASSES

We have examined a series of metaphosphate glasses with P-31 magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy. Increasing the ionic potential (Z/a) of the modifying cation from sodium to magnesium causes a systematic change to more shielded isotropic chemical shifts with a concomitant increase in the peak FWHM. These spectral trends are consistent with counterion-induced modifications to the ionic character of the P-O bond. Such modifications do not produce significant changes in either the chemical shift anisotropy or the asymmetry parameter.