M. Vallet-Regí, S. Nicolopoulos, J. Román, J. L. Martínez and J. M. González-Calbet
Fine zirconium oxide powders have been obtained by pyrolysis of an aerosol produced by ultrahigh frequency from a zirconium oxalate solution. The as-received material, obtained at 400 °C, is amorphous and constituted of hollow spherical particles. This material was annealed under different conditions producing nanometric particles of ZrO2 . A study of the equilibrium between the monoclinic and the cubic/tetragonal phase as a function of the thermal treatment has been performed. Crystallographic characterization of the fine zirconia particles obtained has been accomplished using electron diffraction and high-resolution electron microscopy, revealing that even individual nanometric ZrO2 particles could contain multiple twin variants.