Progress towards all-chemical superconducting YBa2Cu3O7-coated conductors

X. Obradors, T. Puig, A. Pomar, F. Sandiumenge, N. Mestres, M. Coll, A. Cavallaro, N. Roma, J. Gazquez, J. C. Gonzalez, O. Castano, J. Gutierrez, A. Palau, K. Zalamova, S. Morlens, A. Hassini, M. Gibert, S. Ricart, J. M. Moreto, S. Pinol, D. Isfort and J. Bock Supercond. Sci. Technol. 19, S13-S26 (2006) DOI:10.1088/0953-2048/19/3/003 Chemical solution deposition (CSD) has recently emerged as a very competitive technique for obtaining epitaxial films of high quality with controlled nanostructure. In particular, the all-CSD approach is considered to be one of the most promising approaches for cost-effective production of second-generation superconducting wires. The trifluoroacetate (TFA) route is a very versatile route for achieving epitaxial YBa₂Cu₃O₇ (YBCO) layers with high critical currents. In this work, recent advances towards improvement of the performance of several conductor architectures based on the YBCO TFA process will be presented. We show that new improved anhydrous TFA precursors allow a significant shortening of the pyrolysis time (~1.5 h), and we have increased the total film thickness in a single deposition using polymeric additives. On the other hand, further understanding of the YBCO nucleation and growth process has allowed us to obtain a controlled microstructure and high critical currents (J_c≈4–5 MA cm⁻² and I_c≈300 A cm⁻¹ width at 77 K). The growth conditions (CSD) and post-processing conditions (sputtering and CSD) for the underlying oxide cap and buffer layers (CeO₂, BaZrO₃, SrTiO₃, La₂Zr₂O₇, (La,Sr)MnO₃) and of self-organized nanostructures (CeO₂, BaZrO₃) deposited by CSD have been investigated to obtain high-quality interfaces in multilayered systems. Different single-crystal or metallic substrates (YSZ-IBAD (yttrium stabilized zirconia-ion beam assisted deposition) and Ni-RABiT (rolling assisted biaxial texturing)) have been investigated and long (≈10 m) CSD biaxially textured buffers (CeO₂, La₂Zr₂O₇) have been grown on Ni-RABiT substrates using a reel-to-reel system. High-performance TFA-YBCO-coated conductors have been obtained on vacuum-based buffer layers (I_c≈140 A cm⁻¹ width) and on CSD buffer layers grown on IBAD YSZ-SS (stainless steel) substrates. Finally, we report on recent analysis of the magnetic granularity and vortex pinning properties of TFA-YBCO conductors.