TRANSPORT PROPERTIES ACROSS HIGH-ANGLE BICRYSTALS OF MELT-TEXTURED

We have investigated the transport properties of eight individual bicrystals in melt textured YBa2Cu3O6+x in low and high fields at 4K and 77K. Bicrystals were cut from samples produced by the melt texture process with 10% and 20% added Y2BaCuO5. Misorientations between the crystals were determined by pole figure analysis, backscatter channeling patterns and light microscopy. The bicrystals exhibited a wide range of misorientations in both the ab planes and c axis direction and all boundaries were high angle. Contrary to many reported expectations for melt textured materials, all of the grain boundaries were weakly coupled. However, the strength of the coupling varied with misorientation angle and a weaker field dependence of J(c) was observed in the samples with lower misorientation angle and lower grain boundary resistivity.