Effective thickness of CeO₂ buffer layer for YBCO coated conductor by advanced TFA-MOD process

YBCO films were fabricated on PLD-CeO₂/IBAD-Gd₂Zr₂O₇/Hastelloy substrates using the advanced TFA-MOD process. The effective thickness of the CeO₂ buffer layer for obtaining high I_c was investigated in short samples of YBCO films. The CeO₂ buffer layer was epitaxially grown on an IBAD-Gd₂Zr₂O₇ template tape with 18° of Δφ{symbol} by a reel-to-reel PLD system. The in-plane grain alignment of PLD-CeO₂ buffer layers rapidly improved with the thickness and saturated at a critical thickness of 0.8 μm. The size of CeO₂ grains was about 1 μm at the saturated thickness of Δφ{symbol}. YBCO films with the thickness of 1 μm were deposited by the TFA-MOD on the CeO₂ buffer layer with different thickness films. Improvement of the CeO₂ in-plane grain alignment resulted in increase of I_c. The I_c values of 250-290 A were obtained with the CeO₂ layer thicker than 0.8 μm. The CeO₂ thickness, at which the intensity ratio of the BaCeO₃ was saturated, corresponded to the critical thickness. From the view points of achieving higher production rates and to obtain the CeO₂ Δφ{symbol} value of 5° as well as considering the reaction between YBCO and CeO₂, the optimum thickness of the CeO₂ buffer layer on the IBAD-Gd₂Zr₂O₇ with 18° of Δφ{symbol} was found to be at least 0.8 μm.