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

Abstract

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 Ic 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 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 0.8μm. The size of CeO2 grains was about 1μm at the saturated thickness of Δϕ. YBCO films with the thickness of 1μm 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 Ic. The Ic values of 250–290A were obtained with the CeO2 layer thicker than 0.8μm. 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 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 was found to be at least 0.8μm.