Ultrafine nanocrystal precursor induced Jc increase of YBa2Cu3O7−x films prepared using advanced low-fluorine solution

High-performance YBa2Cu3O7−x (YBCO) films were obtained on LaAlO3 (LAO) substrate using an advanced low-fluorine solution with Y-TFA and fluorine-free Ba and Cu salts as precursors. Macropore-free precursor films were obtained using a rapid pyrolysis with the heating rate of 5 °C/min from 200 °C to 310 °C. In the precursor film, CuO and Ba1−xYxF2+x (BYF) were formed as intermediate phases. Ultrafine nanocrystalline CuO particles were found embedded inside the crystalline BYF matrix, leading to the formation of high-quality YBCO film. The obtained single-coated YBCO films showed a better in-plane and out-of-plane texture, and a higher critical current density (over 8 MA/cm2 at 77 K, 0T), compared with the YBCO films produced from precursor consisting of larger CuO particles.