Large area YBCO films on polycrystalline substrates with very high critical current densities

We deposited large-area YBCO films by reactive thermal co-evaporation on bi axially textured, Y2O3 stabilized ZrO2 (YSZ) buffer layers fabricated by an IBAD technique (ion beam assisted deposition). Polycrystalline, partially stabilized ZrO2 (PSZ) with a size of 10 x 10 cm was used as a substrate. Ho mogeneous, biaxially aligned IBAD buffer layers were prepared by using larg e ion guns and substrate rotation during the IBAD process. YBCO films with thicknesses of up to 1400 nm were deposited. The biaxial alignment of the b uffer layer and of the YBCO film was characterized by S-ray diffraction. Th e FWHM of YSZ (111) cp-scans varied laterally within a range of 15 degrees to 20 degrees. The FWHM of the YBCO (103) was always several degrees better with value of only 7 degrees to 9 degrees. The YSZ thickness dependence of this improvement was analyzed. We achieved a mean critical current density of 1.9 MA/cm(2) and a maximum critical current density of 2.1 MA/cm(2) on a substrate area of 10 x 10 cm.