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The TFA-MOD process was applied to fabricate YBCO films on PLD-CeO2/IBAD-Gd2Zr2O7/Hastelloy substrates. In order to obtain higher Ic performance, thicker films maintaining high Jc values are required. Jc depends strongly on the YBCO crystal alignment. Dependences of Jc on Δφ of the CeO2 substrates has been investigated. It was found that the Jc value increased with improvement of the crystal alignment of the CeO2 buffer layers. Also, the Jc value depended strongly on the PH2O during the crystallization. The pore size in the film was smaller in the high Jc films fabricated under medium PH2O and becomes larger in the low-Jc films under low and high PH2O. Furthermore, crack formation was observed in thick films crystallized at high PH2O. The large pore causes local reduction of current paths and additionally introduces the concentration of electric fields. It was found that both the porosity and crack formations limit the Jc properties. Finally, a YBCO film with 2.05 μm in thickness was fabricated on a CeO2/Gd2Zr2O7 layer buffered Hastelloy substrate with Δφ∼4°. A Jc value of 2.02 MA/cm2 and transport Ic value of 413 A at 77 K, self-field were obtained.
Date of Publication: June 2005