Development of Solution Buffer Layers for RABiTS Based YBCO Coated Conductors

The main objective of this research is to find a suitable alternate solution based seed layer for the standard RABiTS three-layer architecture of physical vapor deposited CeO₂ cap/YSZ barrier/Y₂O₃ seed on Ni-5%W metal tape. In the present work, we have identified CeO₂ buffer layer as a potential replacement for Y₂O₃ seeds. Using a metal-organic deposition (MOD) process, we have grown smooth, crack-free, epitaxial thin films of CeO₂ (pure and Zr, Cu and Gd-doped) directly on biaxially textured Ni-5W substrates in short lengths. Detailed XRD studies indicate that a single epitaxial CeO₂ phase with slightly improved out-of-plane texture compared to the texture of the underlying Ni-W substrates can be achieved in pure, undoped CeO₂ samples. We have also demonstrated the growth of YSZ barrier layers on pure CeO₂ seeds using sputtering. Both sputtered CeO₂ cap layers and MOD-YBCO films were grown epitaxially on these YSZ-buffered MOD-CeO₂/Ni-5W substrates. High critical currents per unit width, I_c of 264 A/cm (critical current density, J_c of 3.3 MA/cm²) at 77 K and 0.01 T was achieved for 0.8 μm thick MOD-YBCO films grown on MOD-CeO₂ seeds. These results indicate that CeO₂ films can be grown directly on Ni-5W substrates and still support high performance YBCO coated conductors. This work holds promise for a route for producing low-cost buffer architecture for RABiTS based YBCO coated conductors.