An advanced low-fluorine solution route for fabrication of high-performance YBCO superconducting films

We have developed a new low-fluorine solution consisting of non-fluorine (F-free) barium and copper salts, and fluorine-containing yttrium trifluoroacetate. Using this new low-fluorine solution, the BaCO3 phase was avoided in the pyrolyzed precursor films. Instead, CuO, Y and Ba fluorides (YF3 and BaF2) were formed in the precursor films pyrolyzed at 450 °C, which was the same as when an All-TFA solution (prepared using Y, Ba, Cu trifluoroacetates as precursors) or other fluorine-reduced solutions were used. This new kind of low-fluorine solution has only 23% of the fluorine content in an All-TFA solution, and the fluorine content was lower than any other fluorine-reduced solution. Thus, rapid production of YBa2Cu3O7−x (YBCO) films can be easily realized. Using a heating rate of 10 °C min−1 in the pyrolysis process, a high critical current density (Jc) of 5 MA cm−2 (at 77 K, 0 T) was obtained in YBCO films fabricated on LaAlO3 (LAO) single crystal substrates from the new starting solution.