The facet and dislocation structures of 5° and 7° [001]-tilt grain boundaries of YBa2Cu3O7-d and Y0.7Ca0.3Ba2Cu3O7-d thin film bicrystals were studied. A 24° [001]-tilt YBa2Cu3O7-d grain boundary was also examined in order to contrast it with low-angle grain boundary faceting behavior. All of the low-angle grain boundaries exhibited strong faceting along (100)/(010) and (110) and possessed both straight symmetrical segments containing equally spaced [100] unit dislocations, and step asymmetrical segments composed of (110) and (100)/(010) facets. Grain boundaries with a higher degree of meander acquired up to 40% (110) facets. The atomic structure of (110) facets was revealed by atomic resolution Z-contrast imaging. The (110) facets were dissociated in both YBa2Cu3O7-d and Y0.7Ca0.3Ba2Cu3O7-d grain boundaries. It was also found that the Ca-doped (110) facets were more extended along the grain boundary plane; consistent with the earlier finding of a dissociated dislocation core in Ca-doped (100) facets. The 5° and 7° misorientations which were studied were in the range where YBa2Cu3O7-d grain boundaries began to become obstacles to current flow.

(110) Facets and Dislocation Structure of Low-Angle Grain Boundaries in YBa2Cu3O7-d and Y0.7Ca0.3Ba2Cu3O7-d Thin Film Bicrystals. X.Song: Journal of Materials Research, 2007, 22[4], 950-7