Basic Research on Oxynitride Glasses.

Abstract

Abstract : Nitrogen has been partially substituted for oxygen in a wide variety of silicate systems to produce oxynitride glasses with improved properties. Nitrogen contents as high as 12 at% have been achieved. The glass-forming regions in the Y-Si-Al-O-N, Mg-Si-Al-O-N, and Ca-Si-Al-O-N systems have been investigated in detail, and those in the Si-Al-O-N, La-Si-Al-O-N, Li-Si-Al-O-N, and Sc-Si-Al-O-N systems have been studied to a lesser extent. For all compositions there is a consistent variation in properties with nitrogen content. The glass transition temperature, hardness, fracture toughness, and density all increase, and the thermal expansion coefficient decreases with increased nitrogen content. Those data, together with infrared spectroscopic results, are consistent with a structural model in which trivalent nitrogen substitutes for bivalent oxygen to give a greater degree of cross-linking in the glass network. The improved properties afforded by nitrogen substitution may lead to commercial applications for oxynitride glasses as hardened windows, high modulus glass fibers, leach-resistant coatings, and as joining compositions for nitrogen ceramics.