CRYSTALLIZATION IN SEEDED ZIRCONIA PRECIPITATES

Go-precipitation of mixed zirconium oxynitrate and yttrium nitrate in a diluted ammonia solution(pH 10-10.5) has been used to prepare 3 mol% Y2O3 stabilized zirconia powders. The addition of ultra-fine zirconia particles (crystalline size < 10 nm) in the co-precipitatrd amorphous zirconium hydroxides results in a decrease in the crystallization tem perature of zirconia, from 458 degrees C for the unseeded composition to 434 degrees C for the composition containing 30 wt% ultra-fine zirc onia particles. In contrast, the addition of zirconia particles of 60 to 70 nm in crystalline sizes in the co-precipitated zirconium hydroxi des has no effect on the crystallization temperature.