Texture formation and grain boundary networks in rolling assisted biaxially textured substrates and in epitaxial YBCO films on such substrates

Electron backscatter Kikuchi diffraction was used to study texture development and grain boundary networks in rolling-assisted-biaxially-textured-substrates, and the transfer of such a biaxial texture and preferential grain boundary network to epitaxial YBCO films grown on such substrates. It was found that the rolling texture in the Ni substrate is highly complicated, with most of the grains having orientations at and between the 'B' and 'S' orientations. No cube nuclei could be discerned in the etched, as-rolled sample. On recrystallization, a sharp {001}<100>, cube texture was imparted to the Ni substrate. It was found that the substrate was percolatively connected within 3°. Examination of epitaxial oxide layers on Ni showed that excellent epitaxy was obtained. At times, undesirable orientations nucleated during growth of the oxide layer, however, these were engulfed by the growing film (with correct orientation). Orientation image micrographs of an epitaxial YBCO film on a RABiT substrate with a J(c) of 1.6 MA/cm² at 77 K showed that most of the film was percolatively connected within 2°. A comparison of the spatially correlated and uncorrelated grain boundary misorientation distributions showed that local grain-to-grain correlations were present between the grains. Comparison of the data obtained for the YBCO film with those obtained for the underlying Ni substrate showed that both the macroscopic texture and the grain boundary networks were very similar in the two cases, implying excellent epitaxy of the multilayers.