SYNTHESIS OF Y2O3-DOPED ZRO2 GEL MONOLITHS BY POLYCONDENSATION OF METAL ALKOXIDE AND THEIR CHANGES ON HEATING .1. PREPARATION OF TRANSPARENT GEL MONOLITHS OF Y2O3-DOPED ZRO2

Polymeric gels of Y-doped zirconia were successfully prepared by the controlled hydrolysis and polycondensation of zirconium n-propoxide and yttrium nitrate. The following parameters affected on the reaction mechanism and the microstructure of the resulting gels: (1) the kind of catalyst, (2) the water to alkoxide ratio and (3) the amount of yttrium nitrate. Acetic acid was very effective to control the alkoxide reaction under the limited water to alkoxide ratio. The complex effect of the steric hindrance by alkoxide-acetic acid chelating and the enhanced hydrolysis by the increased proton could control the polycondensation moderately. The yttrium nitrate hydrate acted as a hydrolysis accelerator, which also affected the microstructure of the resulting gel. Transparent monolithic gels of Y-doped zirconia containing up to 10 mol% yttrium oxide were successfully prepared by optimizing these parameters.