High-Jc thick YBCO coated conductors by TFA-MOD process

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 J(c) values are required. J(c) depends strongly on the YBCO crystal alignment. Dependences of J(c) on Delta phi of the CeO2 substrates has been investigated. It was found that the J(c) value increased with improvement of the crystal allgmnent of the CeO2 buffer layers. Also, the J(c) value depended strongly on the P-H2O during the crystallization. The pore size in the film was smaller in the high J(c) films fabricated under medium P-H2O and becomes larger in the low-J(c) films under low and high P-H2O. Furthermore, crack formation was observed in thick films crystallized at high P-H2O. 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 J(c) properties. Finally, a YBCO film with 2.05 mu m in thickness was fabricated on a CeO2/Gd2Zr2O7 layer buffered Hastelloy substrate with Delta phi similar to 4 degrees. A J(c) value of 2.02 MA/cm(2) and transport 1, value of 413 A at 77 K, self-field were obtained.