YBCO films prepared by PLD using nanocrystalline targets doped with BaZrO3 or Y211

YBCO thin films were prepared by pulsed laser deposition from a pure nanocrystalline YBCO target and similar targets doped with BaZrO₃ or Y₂BaCuO₅ (Y211 phase) in order to investigate the effect of these impurities on magnetic flux pinning. The doped targets were pressed from nanopowders prepared by a sol-gel method from starting solutions whose nominal molar ratios corresponded to compositions YBCO+2.2 and 6.5 wt% BaZrO₃ and YBCO+3.0 wt% Y211 phase. The biggest changes in the superconducting properties relative to the films prepared from the pure target were observed in the films ablated from the BaZrO₃-doped targets. Although the doping reduces the critical temperature, the critical current density calculated from the hysteresis loops is significantly increased in external magnetic fields above 0.15 T. Addition of Y211 to the target is found not to be as effective for improving the flux pinning of the films in high magnetic fields as addition of the BaZrO₃. J_c´s in zero field and 77 K were 1.2 MA/cm² in the pure YBCO film, 1.1 MA/cm² in the 2.2 wt% BaZrO₃ doped film and 3.2 MA/cm² in the 3.0 wt% Y211 doped film.