PREPARATION AND CHARACTERIZATION OF ALKOXY-DERIVED METASTABLE CUBIC ZRO2 POWDERS

Ultrafine alkoxy-derived ZrO2 powders have been prepared from the hydrolysis of zirconium n-butoxides with NaOH aqueous solutions of different pH values (pH 11, 13 and 13.7). The powders crystallize to form cubic phase at around 500-degrees-C and transform to tetragonal and monoclinic phases at around 900-degrees-C. Experimental results show that Na+ ions might be electrostatically trapped into the polymerized network structures by the Zr(OBu)3O- species which were formed in basic solutions. The trapped Na+ ions may act as nucleation catalysts, and the presence of Na+ is indeed necessary for stabilizing the cubic ZrO2 powders. The formation of needle-like monoclinic crystallites is attributed to the migration of ultrafine particles resulting from the evolution of sodium.