Magneto-Optical Investigations of LZO Buffer Layer Thickness Effects on YBCO Microstructure in the Simple NiW/LZO/YBCO Structure

The Ni_RABiTS/La₂Zr₂O_7MOD/YBa₂Cu₃ O_7MOCVD structure is a promising architecture for (YBCO) coated conductors. We succeeded in growing highly textured superconducting YBCO films on LZO-buffered Ni-5 at%W (NiW) substrates by metalorganic chemical vapor deposition (MOCVD). A single LZO buffer layer grown by metalorganic decomposition (MOD) is sufficient to ensure structural compatibility between YBCO and Ni, and to protect the substrate from oxidation during YBCO deposition. Textured Ni substrates obtained by rolling technique have intrinsic defects such as grain boundaries and rolling scratches. It is not easy to highlight their effects on LZO and YBCO films by usual measurements like XRD or SEM. The combination of Electron Backscattered Diffraction (EBSD) and Magneto-Optics imaging (MO) is useful to image grain boundaries and flux distribution in coated conductors. It provides complementary information on superconducting film qualities. These two techniques allowed us to understand how the microstructure of the LZO buffer layer and thus of the YBCO film is linked to the current density in this simple heterostructure.