The Effects of Grain Boundaries on the Current Transport Properties in YBCO-Coated Conductors

We report a detailed study of the grain orientations and grain boundary (GB) networks in Y(2)O(3) films grown on Ni-5 at.%W substrates. Electron back scatter diffraction (EBSD) exhibited different GB misorientation angle distributions, strongly decided by Y(2)O(3) films with different textures. The subsequent yttria-stabilized zirconia (YSZ) barrier and CeO(2) cap layer were deposited on Y(2)O(3) layers by radio frequency sputtering, and YBa(2)Cu(3)O(7-δ) (YBCO) films were deposited by pulsed laser deposition. For explicating the effects of the grain boundaries on the current carry capacity of YBCO films, a percolation model was proposed to calculate the critical current density (J(c)) which depended on different GB misorientation angle distributions. The significantly higher J(c) for the sample with sharper texture is believed to be attributed to improved GB misorientation angle distributions.