Tilt grain boundaries in NiO

High-resolution Electron Microscopy (HREM) show that crystallinity is maintained right up to the interface in a high-purity NiO 〈001〉 tilt grain boundary (GB). The strong Fresnel contrast effects that are found in high-angle NiO GBs by both conventional TEM and HREM are largely due to a locally reduced atomic density at the GB and are not caused by the presence of an amorphous phase. The HREM micrographs indicate several atomic-scale GB features.