Nanosized cubic and tetragonal ZrO2 were formed as thin nanocrystalline film on NaCl (100) plane by radio frequency ion beam sputtering. The microstructure and the epitaxy relationship with the NaCl (100) plane were studied by a high-resolution transmission electron microscope. The epitaxy orientation was found to be [001](Z)parallel to[001](N), [100](Z)parallel to[110](N) (group A), [011](Z)parallel to[0 0 1](N), [100](Z)parallel to[100](N) (group B-1) and [0 1 1](Z)parallel to[001](N), [100](Z)parallel to[010](N) (group B-2) between zirconia (Z) and NaCl (N). Groups B-1 and B-2 are the dominant type. The possible causes for the epitaxy relationship are discussed. Crystallites within the same group can merge by rotation and coalesce into a single crystal, whereas crystallites in different groups can form high-angle grain boundaries. (c) 2006 Elsevier B.V. All rights reserved.