Progress towards all-chemical superconductingYBa2Cu3O7-coated conductors

Abstract

Chemical solution deposition (CSD) has recently emerged as a very competitive techniquefor obtaining epitaxial films of high quality with controlled nanostructure. Inparticular, the all-CSD approach is considered to be one of the most promisingapproaches for cost-effective production of second-generation superconducting wires.The trifluoroacetate (TFA) route is a very versatile route for achieving epitaxialYBa2Cu3O7 (YBCO) layers with high critical currents. In this work, recent advances towardsimprovement of the performance of several conductor architectures basedon the YBCO TFA process will be presented. We show that new improvedanhydrous 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 polymericadditives. On the other hand, further understanding of the YBCO nucleation and growthprocess has allowed us to obtain a controlled microstructure and high critical currents(Jc≈4–5 MA cm−2 and Ic≈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-organizednanostructures (CeO2, BaZrO3) deposited by CSD have been investigated to obtain high-quality interfacesin multilayered systems. Different single-crystal or metallic substrates(YSZ-IBAD (yttrium stabilized zirconia-ion beam assisted deposition) andNi-RABiT (rolling assisted biaxial texturing)) have been investigated and long(≈10 m) CSD biaxiallytextured buffers (CeO2, La2Zr2O7) have been grown on Ni-RABiT substrates using a reel-to-reel system. High-performanceTFA-YBCO-coated conductors have been obtained on vacuum-based buffer layers(Ic≈140 A cm−1 width) and on CSD buffer layers grown on IBAD YSZ-SS (stainless steel) substrates. Finally, wereport on recent analysis of the magnetic granularity and vortex pinning properties ofTFA-YBCO conductors.