Fabrication of Y-Ba-Cu-O films on surface-oxidation epitaxy (SOE) processed substrates

The surface-oxidation-epitaxy (SOE) method promotes simple and cost-effective process to form a biaxially textured NiO template for epitaxial growth of YBa/sub 2/Cu/sub 3/O/sub x/ (Y-Ba-Cu-O) film. SOE tapes of 100 m in length were prepared by the reel-to-reel oxidation system with the tape moving speed of 10 m/h. A highly biaxially textured NiO layer, which had (Delta)(phi) (full width at half maximum from X-ray (phi)-scan) of less than 23(degree) throughout the whole length, was successfully formed under appropriate conditions of temperature and atmosphere. In order to improve surface conditions for obtaining high critical current density (J/sub c/) for Y-Ba-Cu-O film on the SOE-tapes, we have investigated the effect of thin oxide cap layers such as MgO, SrTiO/sub 3/, CeO/sub 2/, and so on. When BaZrO/sub 3/ was used as a cap layer, J/sub c/ and critical current (I/sub c/) of Y-Ba-Cu-O films grown by the pulsed laser deposition (PLD) at 77 K were measured to be 1.3 MA/cm/sup 2/ and 137 A, respectively. These values were for a 10 mm-width short tape. A continuous deposition of YBCO on 10-cm long *10-mm wide SOE tape with SrTiO/sub 3/ or BaZrO/sub 3/ cap layer was also investigated. The end-to-end I/sub c/ was 1 A (J/sub c/ of 1.6 *10/sup 4/ A/cm/sup 2/) for SrTiO/sub 3/ cap layer and 4 A (J/sub c/ of 5.6 *10/sup 4/ A/cm/sup 2/) for BaZrO/sub 3/ one.