Nonrandom percolation behavior of grain boundary networks in high-T_c superconductors

The topology of grain boundary networks in tetragonal and orthorhombic superconductors was examined and found to be considerably nonrandom, as reflected in the coordination of low- and high-angle boundaries at triple junctions, as well as the percolation threshold for current flow. These results arise due to the need for crystallographic consistency in the grain boundary network.