Shape dependent coalescence and preferred orientation of CeO2 nanocrystallites

Laser ablation (420–1200 W for 1–8 s in air) of CeO2-rich targets (CeO2, Z4C6 and A12Z40C48 where A, Z and C denote Al2O3, ZrO2 and CeO2, respectively and subscripts in mol.%) resulted in the CeO2 condensation. Transmission electron microscopic observations indicated the CeO2 crystallites thus produced were predominantly {111} octahedra and cubo-octahedra ({111}+{100}), having {111} as the preferred rest plane and contact plane for coalescence. X-ray diffraction of the CeO2 crystallites deposited on surface oxidized Si(100) and soda-lime glass showed preferred orientation {111} in accordance with the habit plane of the crystallites. Thus, the shape of crystalline condensates is an important factor of preferred orientation regardless of the type of the substrates. Post-deposition annealing (1200°C in air) of CeO2 film on surface oxidized Si(100) caused orientation change from {111} to {100}, which can be ascribed to shape change and accompanied rotation-coalescence of the CeO2 crystallites.