Crystallisation of zirconolite from an alkoxide precursor

Abstract

Crystallisation of zirconolite (CaZrTi2O7) from a stoichiometric alkoxide precursor was studied by X-ray diffraction, differential thermal analysis and high resolution electron microscopy. The X-ray amorphous oxide formed by drying mixed ethanolic solutions crystallised to a disordered fluorite structure on heating to ~ 700 °C. Zirconolite with a pseudo-trigonal structure formed at ~ 900 °C, and at higher temperatures gradually transformed to fully ordered monoclinic zirconolite. Activation energies for the amorphous to fluorite and fluorite to pseudo-trigonal zirconolite transformations were obtained from the DTA measurements by the Ozawa method, but were not consistent with the rates of transformation observed by X-ray diffraction in isothermal measurements. The pseudo-trigonal zirconolite was found by high-resolution electron microscopy to be highly disordered monoclinic zirconolite.