Oxynitride glasses and their properties - an overview

Oxynitride glasses were first discovered as intergranular phases in silicon nitride based ceramics in which the composition and volume fraction of such oxynitride glass phases determine the properties of the material, in particular, high temperature mechanical properties. A number of investigations on oxynitride glass formation and properties have shown that they possess higher softening temperatures, elastic modulus, viscosity and hardness compared to the corresponding oxide glasses. This paper provides an overview of oxynitride glasses and outlines the effect of composition, especially nitrogen content, on properties such as glass transition temperature, hardness, Young's modulus and viscosity. Some studies of crystallization to form B-phase glass-ceramics are reported and also fracture of B-phase parent glasses in the Y-Si-Al-O-N system containing different levels of nitrogen are reported.