Nanocrystalline tetragonal zirconia stabilized with yttrium and hydroxyls

Nanocrystalline tetragonal zirconia was prepared by soft chemistry. via the hydrolysis of an aqueous solution of zirconyl and yttrium chlorides, and by using the sol-gel technique with zirconium n-butoxide as precursor and HCl, CH3COOH, and NH4OH as hydrolysis catalysts. In the samples with yttrium, the tetragonal phase appeared yet at crystallization beginning Since the x-ray diffractograms of the amorphous samples were equal and independent of yttrium concentration, it is suggested that yttrium substituted for zirconium atoms already in the formation of the amorphous structure. In the sol-gel samples, hydroxyls stabilized the tetragonal phase. After sample dehydroxylation at 600 degrees C, the main phase was monoclinic zirconia, except in the samples prepared with acetic acid; here, the main phase was tetragonal zirconia, which was stabilized by carboxyls. (C) 1999 Acta Metallurgica Inc.