Structure and transport properties of [001] tilt grain boundaries in YBa{sub 2}Cu{sub 3}O{sub x}

We have studied the microstructure and transport properties of nominal [001] tilt grain boundaries in order to correlate microstructural features with transport properties. single grain boundaries were prepared by epitaxial growth of YBa{sub 2}Cu{sub 3}O{sub x} onto bi-crystal SrTiO{sub 3} substrates. Transport measurements were used to characterize the electrical behavior across the boundary while TEM was used to characterize the structure of the boundary. The transport measurements are consistent with grain boundary behavior, but detailed comparisons show anomalies which may be resolved by microstructural characterization. Microstructural characterization showed that these artificially induced grain boundaries are periodically decorated by impurity phases. In addition, the boundaries are not always straight, but instead frequently meander away from the path of the underlying boundary in the substrate, and the various facets produced by the meandering show varying degrees of tilt and twist character. These structural variations suggest one potential explanation for the reduced effective coupling area, although the correlation is not unambiguous