Improved epitaxial texture of thick YBa2Cu3O7-δ/GdBa2Cu3O7-δ films with periodic stress releasing

Thick high-Tc superconducting films consisting of a YBa2Cu3O7-(delta)/GdBa2Cu3O7-(delta) periodic architecture are developed on oxid-buffered Hastelloy tapes using a pulsed laser deposition process. It is revealed that multilayer intermittent structures for superconducting layers are effective to avoid the presence of a-axis grains and microcracks that occur with increasing thickness, which are frequently observed in monolayer films of REBa2Cu3O7-delta (RE = Y, Gd, or other rare earths), such grains and cracks being the significant challenge for obtaining high critical current in coated conductors. Presently, the thicknesses of multilayer films vary from 0.5 mu m to 3 mu m and, based on the SEM images and x-ray phi-scans, hardly show the influences on the microstructures and grain orientation of the c-axis. Also, the characteristic Raman spectrum patterns and their shifting with increasing the thickness of YBCO/GdBCO imply that the superior texture is obtained due to the evolution of stress dominated by the compressive stress rather than tensile stress.