Fluorine analysis and microstructural evolution in coated YBCO conductor deposited by metal trifluoroacetate process

A solution based processes using metal trifluoroacetate (TFA) precursors is being developed for commercialization of Yttrium Barium Copper Oxide (YBCO) coated conductors. This nonvacuum technique uses inexpensive precursors and has the advantage of easy scalability, ease of composition control, eliminates carbonate formation during decomposition, and helps maintain film uniformity during heat treatment. However, fluorine remains incorporated in the YBCO film, depending on process conditions, and may result in a reduction of Jc. An appropriate heat treatment schedule ensures reduction of fluorine in the YBCO films as well as an improvement in microstructural properties. The aim of this work was to investigate the fluorine depth profile, density, and microstructural evolution of metal organic deposited (MOD) YBCO films with heat treatment using focused ion beam (FIB) microscopy, nuclear reaction analysis (NRA), and Rutherford backscattering spectroscopy (RBS). Multilayer structures studied consisted of 0.7 μm to 2.0 μm-thick YBCO layers deposited on a NiW alloy substrate buffered with CeO₂/YSZ/Y₂O₃.