Microstructural Characterization of Nanosized Ceria Powders by X-Ray Diffraction Analysis

Spherically shaped nanocrystalline ceria powders were prepared by high energy ball milling (HEBM) of plate-shaped as-received ceria powders. Rietveld analysis was used to determine the surface weighted average crystallite size, lattice parameter, and lattice strain. The classical Williamson-Hall as well as modified Williamson-Hall method was used to determine the volume weighted average crystallite size. A comparison of the crystallite size obtained by the classical as well as modified Williamson-Hall method shows that the strain anisotropy consideration in the modified Williamson-Hall method yields a lower value of the crystallite size, and this difference becomes more pronounced with the increase in milling time. The modified Williamson-Hall method indicates that the dislocations present in the ceria powders are edge in character. The ceria powders also were characterized by field emission scanning electron microscopy (FESEM) and high resolution transmission electron microscopy (HRTEM) techniques.