OXYGEN DIFFUSION PATHS AND MICROCRACK FORMATION IN THE TEXTURED 1-2-3 REGIONS OF PARTIAL-MELTED Y-BA-CU-O OXIDE

By annealing tetragonal Y-Ba-Cu-O in air, the oxygen diffusion process in the textured region of 1-2-3 plates was investigated by use of an optical polarizing microscope. The oxygen diffused region was identified by observing the orthorhombic phase near cracks containing twin structure and the tetragonal phase, the crack-free region. The thermal cracks formed by rapid thermal processing offer good diffusion paths for oxygen atoms in the textured region. The transformation stress from the tetragonal-to-orthorhombic phase results in the formation of microcracks along the cleavage plane of the Y-Ba-Cu-O oxide. In addition to the thermal cracks, the transformation cracks arc though to be effective oxygen diffusion paths in the textured 1-2-3 region. This result is comparable to that for polycrystalline Y-Ba-Cu-O oxide where oxygen diffusion paths are regions of open porosity and high-angle grain boundaries.