Controlled growth of bulk bicrystals and the investigation of microstructure-property relations of YBa₂Cu₃O_x grain boundaries

A new method to prepare bicrystals with well defined planar interfaces in YBa₂Cu₃O_x (Y123) has been developed. The bicrystal misorientation is controlled by dual seeding using Nd_1+xBa_2-xCu₃O_y single crystals. The grain boundary plane orientation is influenced by the positioning of the seeds and by control of the temperature gradient. The macro-, meso-, and microscopic planarity of the grain boundaries has been established by optical and electron microscopy. In addition, a difference in critical current density between the low (≤10°) and the high (≥20°) misorientation angle regime of nearly two orders of magnitude has been established in a series of [001]-tilt grain boundaries. Thus, this type of grain boundary may allow a less ambiguous interpretation of the relationship between microstructure and transport properties than is possible from bicrystal thin film boundaries by eliminating the potential variations in properties associated with a varying grain boundary plane.