It was recalled that grain boundaries in high-temperature superconductors were very important with regard to the ability of these materials to carry super-currents. Transmission electron microscopic studies were made of grain boundaries, combined with simulations of their atomic and electron structures and estimations of their superconducting order parameter. By using a model which had been developed in order to correlate grain-boundary microstructures and superconducting properties, it was shown that the coupling behavior of grain boundaries did not depend only upon the misorientation characteristics. It was concluded that the grain boundary plane, as well as atomic ordering in the vicinity of the grain boundary, played an important role in the current-carrying capabilities of the grain boundaries.

Grain Boundaries in Bulk YBCO. K.Salama, M.Mironova, S.Stolbov, S.Sathyamurthy: Physica C, 2000, 341-348[3], 1401-5