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 biaxially 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. Homogeneous, biaxially aligned IBAD buffer layers were prepared by using large 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 buffer layer and of the YBCO film was characterized by X-ray diffraction. The FWHM of YSZ (111) cp-scans varied laterally within a range of 15° to 20°. The FWHM of the YBCO (103) was always several degrees better with value of only 7° to 9°. The YSZ thickness dependence of this improvement was analyzed. We achieved a mean critical current density of 1.9 MA/cm2 and a maximum critical current density of 2.1 MA/cm2 on a substrate area of 10 x 10 cm.