Sintering behaviour and properties of YAlSiO and YAlSiON glass-ceramics

Four different YAlSiO and YAlSiON compositions that produced either glass or glass-ceramic materials were designed. Densities, glass transition temperatures, coefficients of thermal expansion and hardness data were established for each material. The sintering behavior was determined from the hot stage microscopy (HSM) runs. For the YAlSiO glass compositions, the viscosity–temperature curves were estimated from five characteristic HSM points using Scholze's method. The YAlSiON glass-ceramics with higher Y content showed YAlO3 and SiAl6O2N6 crystals and the poorer Y composition had crystalline precipitates of Si3N4, Si4Al2O2N6 and Y2SiAlO5N. The effects of the Al/Si and Y/Si ratios, and the nitrogen content on the properties have been discussed. These glass-ceramics showed relatively high thermal expansion coefficient and hardness and, therefore, its application as protective coatings for metallic components against high temperatures and/or corrosive environments is envisaged.