Nano-ZrO2 was succesfully prepared by calcining a precursor of a zirconium gel-emulsion in oleic acid. The gel-emulsion process was started with the preparation of a gel zirconium hydroxide. The hydroxide gel was then mixed with oleic acid at various ratios and heated at 200 oC to give zirconia precursors. These precursors were succesfully calcined at 800 oC, 1000 oC, and 1200 oC, to give zirconia powder. The crystal structure and the particle morphology of the calcined powder were identified using XRD, SEM, and TEM. The XRD results show that monoclinic zirconia is formed dominantly with crystallite sizes ranging from 46.2 to 55.3 nm at 800 oC. Meanwhile, the SEM micrographs of the zirconia calcined at 800 oC show particles with a homogenous morphology having sizes below 100 nm. The TEM results indicate that that the individual grain diameters of ZrO2 were less than 60 nm. A lower oleic acid concentration leads to a more alkaline condition and more monoclinic zirconia formed; and a higher calcination temperature leads to a larger size of crystallites.

Keywords: Zirconia, Gel-emulsion precursor, Oleic acid, Phase transformation.