Dislocations and crystallite size distribution in nanocrystalline CeO 2 obtained from an ammonium cerium(IV)-nitrate solution

Abstract

Nanocrystalline CeO 2 powder has been obtained by thermal decomposition of hydrated ceria prepared from a solution of ammonium cerium(IV) nitrate. Thermal treatments up to 700°C were applied in order to reduce microstrains without substantial increase of grain growth. Crystallite size and size-distribution has been determined by X-ray diffraction profile analysis. The Williamson–Hall plots of the FWHM have revealed pronounced strain anisotropy which has been treated and rationalised in terms of the dislocation model of the mean square strain in the modified Williamson–Hall plots. The dislocation densities were obtained from the modified Warren–Averbach method. A strong decrease of the dislocation density and a slight increase of the crystallite size is observed with increasing annealing temperature.