Sintering of Zircon Utilizing SiO₂-TiO₂-Al₂O₃ Liquid Phase

Abstract

Effects of SiO₂-TiO₂-Al₂O₃ liquid phase on sintering of zircon were investigated with the compacts of zircon containing 0-30wt% additives at 1600°C. Compositions of additives used in this study were 85-100wt% SiO₂-TiO₂ eutectic mixture (89.5wt% SiO₂, 10.5wt% TiO₂) and 0-15wt% Al₂O₃. The liquid phase was formed from additives in the sintered bodies. The resultant liquid accelerated sintering of zircon and increased the density of the sintered zircon bodies by filling the intergranular spase of the compacts. But excess liquid prevented binding of each zircon grain, resulting in the high closed porosity. Therefore, the adequate amounts of additives for sintering of zircon were in the range of about 10 to 20wt%. The increase of Al₂O₃ contents in additives resulted in a faster melting of additives and in a decrease in the viscosity of liquid. Consequently, it caused a decrease in the open porosity and an increase in the closed porosity. Since the former was more significant than the latter in this study, the overall effect was favorable for densification. The use of pre-glassified additives, which contained none and 5wt% Al₂O₃, resulted in an acceleration of formation of liquid and of sintering of zircon with a significant decrease in the open porosity.