Investigation on starting solution of TFA–MOD process for high-speed production of YBCO coated conductors

Abstract

We have developed a new starting solution consisting of non-fluorine (F-free) yttrium salt, barium trifluoroacetate and copper octylate with focusing on a high-speed production of YBa 2Cu 3O 7− y (YBCO) coated conductors by the trifluoroacetate–metal-organic deposition (TFA–MOD) method. High critical current density ( J c) was recognized in the YBCO films fabricated on CeO 2 buffered ion-beam assisted deposition (IBAD)-Gd 2Zr 2O 7/Hastelloy substrates from the new starting solution at a wide range of the heating rates in the calcination process (2 → 25 °C/min, 2.3 → 2.4 MA/cm 2). Additionally, any degradation of J c performance (higher than 2 MA/cm 2 at 77 K, self-fields) up to about 0.4 μm per single coating was not observed in the YBCO films fabricated from the new starting solution at the heating rate of 5 °C/min in the calcination process. The relationship between fluorine contents in the single coating film and J c performance of the YBCO films suggested that the fluorine content in the single coating film determines the quality (bulk density, uniformity, etc.) of the precursor film.