Abstract
CeO2 powder prepared by isothermally aging cerium (III) nitrate solution at 303K in the presence of hexamethylenetetramine was sintered at 1723K for 2h. This process yielded polycrystalline CeO2 having a relative density equal to approximately 97.6% of its theoretical density. Polycrystalline CeO2, finely polished and examined by atomic force microscopy (AFM), was used to develop thermal grain boundary grooves at different temperatures (1473-1663K) and times (t=30-480min) in air. Subsequently, AFM was used to observe the surface morphological change in the annealed polycrystalline CeO2 in order to measure the width, W, and the dihedral angle Ψ of the developed grain boundary grooves. AFM observation revealed logW-logt relationships that are approximately linear with slopes of approximately 1/4. An analysis according to Mullins' formulas showed that grain boundary grooving is controlled by surface diffusion. Finally, the surface diffusion coefficient of polycrystalline CeO2 was calculated at different temperatures (1473-1663K), and the obtained diffusion coefficient was considered to correspond to that of a (CeO2)n group transportation.
