Solid-state MAS NMR studies of the structure of magnesium aluminosilicate oxynitride glasses

Abstract

Magic angle spinning (MAS) 29Si and 27Al NMR has been applied to study the structure of glasses in the system SiO2-Al2O3-MgO with and without addition of Si3N4. Aluminium appears to be tetrahedrally coordinated. In contrast to studies of binary and quasibinary glasses, as a consequence of the large number of structural units, no splittings of the 29Si NMR spectra into individual lines have been observed. Chemical shift and line width data have been discussed in terms of a structural model which rules out AI-O-AI, AI-Ο-Mg and Mg-Ο-Mg bonding as well as a binary distribution of Q^n units. The spectra indicate preferentially Si-N and to a lesser extent Al-Ν bonding if nitrogen is incorporated into the network.