Wet-chemical process using ammonia to precipitate aluminum ions dissolved in a zirconia sol solution is examined. Formation of crystalline bayerite is unfavorable for fine dispersion of zirconia nanoparticles in alumina matrix after heat treatment. To avoid the bayerite formation, it was preferred to make a precipitation with a diluted ammonia or with an ammonia gas flow at high temperature. By optimizing the precipitation process and the calcination temperature, we successfully prepared the uniform microstructure in which tetragonal zirconia particles of ∼30 nm is finely dispersed within the alumina grains.

Keywords: Zirconia-toughened alumina, Ammomia percipitation, Microstructure