Novel Na–Li–SiAlPON glasses prepared by melt synthesis using AlN

Amorphous alumino–silicophosphate materials containing up to 1.70 wt.% nitrogen have been successfully prepared by aluminium nitride solution in Na–Li–Si–Al–P–O melts at 850 °C thus preventing phosphorus volatilisation. Although the solubility limit for nitrogen in these glasses was limited to 8.31 wt.%, the presence of nitrogen in the materials greatly increases their glass transition temperatures, suppresses the devitrification and has a significant effect on their melting behaviour. Comparative analysis of Raman spectra for the oxide and oxynitride glasses shows the substitution of P–O–P linkages by PN–P linkages while tri-coordinated nitrogen bridges were not detected. The attendant increase in network connectivity arising from such a substitution is responsible for the increase in glass transition temperature when nitrogen substitutes for oxygen.