Atomic force microscopy study of surface diffusion in polycrystalline CeO2via grain boundary grooving

CeO2 powder prepared by isothermally aging cerium (III) nitrate solution at 303 K in the presence of hexamethylenetetramine was sintered at 1723 K for 2 h. This process yielded polycrystalline CeO2 having a relative density e qual to approximately 97.6% of its theoretical density. Polycrystalline CeO 2, finely polished and examined by atomic force microscopy (AFM), was used to develop thermal grain boundary grooves at different temperatures (1473-1 663 K) and times (t = 30-480 min) in air. Subsequently, AFM was used to obs erve the surface morphological change in the annealed polycrystalline CeO2 in order to measure the width, W, and the dihedral angle Psi of the develop ed grain boundary grooves. AFM observation revealed log W-log t relationshi ps that are approximately linear with slopes of approximately 1/4. An analy sis according to Mullins' formulas showed that grain boundary grooving is c ontrolled by surface diffusion. Finally, the surface diffusion coefficient of polycrystalline CeO2 was calculated at different temperatures (1473-1663 K), and the obtained diffusion coefficient was considered to correspond to that of a (CeO2), group transportation.