Characterization of the structure of Y-Ba-Cu-O coated conductors
Transmission electron microscopy (TEM) has been applied to the microstructural investigation of YBa/sub 2/Cu/sub 3/O/sub 7-/spl delta// (YBCO) thick films deposited on polycrystalline Ni-based metal substrates by pulsed laser deposition. The films were found to be strongly textured with c-axis oriented grains aligned perpendicular to the substrates. Despite the large average in-plane misorientation (/spl theta//spl sim/14/spl deg/), as was estimated from selected area electron diffraction and X-ray diffraction, TEM inspection reveals colonies of submicron-sized grains with low angle (/spl theta//spl les/7/spl deg/) tilt grain boundaries. The linkage of the colony structures may provide a continuous percolation pathway for the supercurrent transport in YBCO, which may provide the mechanism for the higher than expected critical current density J/sub c/. Periodic arrays of grain boundary dislocations were observed, which may serve as effective flux pinners.