Crystallization of silica-rich glasses prepared by sol-gel in the system alumina-silica-zirconia

The crystallization of ZrSiO4 and its evolution with temperature from chemically homogeneous alumina-silica-zirconia powders prepared by sot-gel method from alcoxide mixtures was studied in the silica-rich region. A glass with the same composition was obtained by quenching in water from the melt. The gel-glasses evolution and microstructure were studied by means of XRD, IR and SEM/EDX, in the range of temperatures up to 1650degreesC. The materials consisted mainly of amorphous phase up to 1200degreesC, at which partial crystallization of cristobalite was observed. IR spectroscopy analysis showed zircon bands after thermal treatment at 1200 C. The crystallization of zircon and zirconia particles at 1550degreesC was confirmed by SEM/EDX analysis. At 1650degreesC the only stable crystalline phase observed after 40 h of thermal treatment was zircon.