Structure and Property of YBa2Cu3Ox Tapes Formed on Metallic Substrate by CVD Technique

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Abstract
YBCO superconducting tapes with good superconducting property were prepared by a continuous CVD technique on 300mm long Hastelloy with biaxially aligned YSZ buffer layer. High Jc of larger than 5×108A/m2 (77K, 0T) covering the full length of the tapes that included the maximum value of 5.9×109A/m2 (Ic=10.4A) were achieved. The structure of YBCO tapes with high Jc larger than 109 A/m2 have been studied using by scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and transmission electron microscopy (TEM). The precipitates with a size of 1–3 μm were observed in the SEM and TEM images of YBCO tapes, and these were characterized as the gathering of Cu-O and Y-Ba-Cu-O grains with a size of 0.1–0.5 μm by the EDS analysis. An area of these second phase was estimated at 10–20%, but these grew from a part of 0.3 μm in the thickness from the bottom of YBCO layer, so the effective volume of the current path within these region were not completely blocked. Good c-axis oriented growth of YBCO layer normal to the flat surface of YSZ buffer layer was shown in the cross-sectional TEM view, in addition the intermediate layer as barium zirconate (BZO) with 15–20nm in the thickness was formed on the top of YSZ layer.