Progress on TFA-MOD coated conductor development

The recent progress in coated conductor development by the TFA-MOD process was reviewed. Much progress was recognized in the R&D on TFA-MOD processing for satisfying several requirements, such as high superconducting performance, long tape production, high production rate, etc., considering the real application. For high superconducting performance, the high I_c value of 413 A was achieved in a short sample with an architecture of MOD-YBCO/IBAD-GZO/IBAD-GZO/Hastelloy. It was realized by improving the in-plane crystal grain alignment of the CeO₂ buffer layer and optimizing conditions of the heat treatments in the calcination and crystallization processes. In the calcination process, it was found that lower heating rate was effective to improve the morphology of the multi-layered precursor by preventing from pore generation and segregation of Cu elements. In the crystallization process, it was found that high humid gas partial pressure was effective to improve the J_c values by reducing the amounts and size of pores in the YBCO layers. Furthermore, in the case of thicker firm, it was found that the low heating rate in the crystallization process was effective to prevent from the crack formation. On the other hand, in order to obtain the long tape with uniform I_c values, in the crystallization process, the gas flow condition in a large scale equipment for the continuous long tape process was investigated using a computer simulation technique. Consequently, the 8.6 m YBCO on PLD-CeO₂/IBAD-Gd₂Zr₂O₇/Hastelloy tape which shows high I_c performance of 119 A as an end-to-end value at 77.3 K in self fields, was successfully obtained. As a result, I_c × L(length) value of 1024 A m was achieved.