Progress in R&D for YBCO coated conductors by TFA-MOD processing

Recent progress in the research and development of the TFA-MOD processing for the coated conductors is reviewed. For the higher I_c performance, process conditions such as heating rate and water vapor inlet temperature in the calcination step and heating rate and water vapor pressure in the crystallization step have been optimized to obtain YBCO films with good crystallinity. Consequently, a high I_c value of 431A/cm-w was achieved by the combination of the above optimized conditions with the use of highly textured CeO₂ cap layered substrates. Forwards the effort for long tape fabrication with high production rate, the multi-turn system for coating and calcination step was developed. Additionally, the reel-to-reel system for the crystallization step was developed for the longer tape, and a 25m long YBCO tape with a reasonable end-to-end I_c value of 100A, which corresponds to 2500Am as a product of I_cxL, was obtained by the above continuous system. For the higher production rate in the crystallization step, it was confirmed that optimization of the processing parameters such as high water partial pressure, high diffusion constants due to low total pressure, and a high gas flow rate affects the YBCO growth rate.