Abstract
Subsolidus phase equilibria in Al2O3-Y2O3-SiO2 system and the phase separation and crystallization behavior of glass in this system were studied by X-ray diffraction, differential thermal analysis, scanning electron microscopy and X-ray microanalysis. Phase relations, liquidus and solidus temperatures in this system were obtained. Phase equilibrium was not confirmed in a lower temperature than solidus temperature near 1340°C. The glass transition temperature (Tg) the starting temperature of crystallization (Tc), the 1st and 2nd peak temperatures of crystallization (To and To' respectively) were studied as a function of composition. The activation energy of crystallization ΔE was determined by analyzing the heating rate dependence of To and found to be in a range of 472-890kJ/mol, depending on the composition. ΔE had a tendency to increase with decrease in liquidus temperature, suggesting that the glass becomes stable in compositions with lower liquidus temperatures. During heat treatment of glass at 1300°C, the phase separation was found to occur as an early stage of crystallization.
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