Oxynitride glasses - an overview

Abstract

The theory and practice of oxynitride glass synthesis and property evaluation came into effect since late 70's. Its importance lies in the fact of its formation at the grain-boundary of synthesized silicon-nitride ceramics with additives. Earlier, heating an oxide glass with NH3 and/or N2 was the route to obtain oxynitride glass. Later on greater amount of nitrogen retention was made possible using AlN or Si3N4 as batch material. Silicate, borate and phosphate systems were studied in isolation or in conjugation. Melting temperature of such glasses varied from 1500-1800°C. Different technological developments regarding furnace atmosphere, temperature, compositions etc have been discussed towards a successful synthesis with a thermodynamic approach. Nitrogen content in glass as high as 36.8 eq% has been reported by the application of an overpressure of 30 atm N2. Different physical and chemical properties have been discussed in relation to nitrogen content in glass. Structural aspects have been considered with respect to XPS and IR spectroscopic studies. Finally some points have been highlighted towards some potential applications.