Glass Formation, Properties and Structure of Soda--Yttria--Silica Glasses

The glass-formation region of the soda--yttria--silica system was determined. The glasses within this region were measured to have a density of 2.4-3.1 g/cm exp 3 , a refractive index of 1.50-1.60, Vickers hardness values of 3.7-5.8 GPa, softening temperatures between 500-780 deg C, and a coefficient of thermal expansion of 7 x 10-19 x 10 exp --6 / deg C. Aqueous chemical durability measurements were made on select glass compositions while infrared transmission spectra were used to investigate the glass structure and its effect on glass properties. A compositional region was identified which exhibited high thermal expansion, high softening temperatures, and good chemical durability. Given these properties, a portion of these glasses meet the requirements necessary to make suitable starting compositions for high-temperature coatings for super-alloys and for glass-to-metal seals.