A review was presented of the various types of grain boundary found in YBa2Cu3O7-d superconducting ceramics. A variety of samples, covering a wide range of current density Jc values was examined: including classical bulk ceramics, melt-textured bulk ceramics, bulk and thin-film bicrystals with specific orientations, thin films and single crystals. It was found that Jc decreased with increasing grain boundary misorientation. From the magnetic behavior, the critical current density was expected to increase with the number of pinning centers. All of the studies reviewed led to the conclusion that grain boundaries in Cu3Ba2YO7 materials could not be understood without having specific information on their local composition, structure and electronic state.

Grain Boundaries in High-Temperature Superconducting Ceramics. J.Ayache: Philosophical Magazine, 2006, 86[15], 2193-239