Enhanced flux pinning properties of MOD-processed YBa₂Cu ₃O_{7 - δ} thin films with BaZrO₃ nanoparticles using a Ba-deficient coating solution

We report the flux pinning properties of YBa₂Cu₃ O_{7 - δ} (YBCO) thin films with BaZrO₃ (BZO) nanoparticles, fabricated by a fluorine-reduced trifluoroacetate-metal-organic deposition process. For this study, the Ba-deficient coating solutions (Y: Ba: Cu=1: 1.5: 3) with various BZO contents ranging from 0 to 15 mol % were prepared by mixing Ba-trifluoroacetate with fluorine-free Y, Cu, and Zr sources. Precursor films were deposited on SrTiO₃ (001) substrates by dip-coating, pyrolized in a humid oxygen atmosphere, and finally fired at a high temperature in a reduced oxygen atmosphere. Highly enhanced critical current densities (J_c) in magnetic fields were achievable from all BZO-doped samples. The optimally processed YBCO film with 7.5 mol% BZO nanoparticles exhibited the J_c values of 0.39 and 0.5 MA/cm² at 77 K in 1 T and at 65 K in 3 T for H//c, respectively. The BZO nanoparticles of 10-50 nm size trapped in the YBCO matrix are considered to be responsible for enhanced flux pinning in BZO-doped YBCO films.