Contribution of grain boundary planes to superconducting coupling in YBCO

High-angle grain boundaries are considered to be the main obstacle for current flow in polycrystalline bulk superconductors. In bicrystal YBCO thin films, it has been shown that the current carrying behavior of grain boundaries is strongly dependent on misorientation angles. However, grain boundaries formed by the liquid phase removal method in bulk YBCO do not show such dependence, where high-angle grain boundaries are found to be capable of carrying high currents. To understand the mechanism by which current is carried by these high-angle grain boundaries, we performed TEM studies on two high-angle boundaries whose J/sub c/ varied considerably. The misorientation characteristics and grain boundary planes for these grain boundaries were determined.