Incorporation of double artificial pinning centers in YBa ₂Cu₃O_7-d films

YBa₂Cu₃O_7-x+BaZrO₃+Y ₂O₃ (YBCO+BaZrO₃+Y₂O₃) mixed films were prepared on SrTiO₃/MgO substrates by pulsed-laser deposition, with an YBCO+BaZrO₃ target with a thin Y ₂O₃ sector stuck on the top. The pinning properties for the double-doped YBCO+BaZrO₃+Y₂O₃ thin film were enhanced in comparison with those of a pure YBCO sample prepared in the same experimental conditions. The maximum global pinning forces F_p for the double-doped sample are 12.8GN m^-3 near 3 T at 77 K, 46.3 GN m^-3 near 4 T at 65 K, and 122 GN m^-3 near 9 T at 40 K. In the double-doped sample the angular dependence of J_c showed a broad peak at , due to the flux pinning by c-axis correlated defects, combined with a plateau, due to the flux pinning by isotropic pinning centers. Both BaZrO ₃ nanorods parallel to the c-axis and Y₂O₃ nanoparticles randomly dispersed inside the YBCO matrix were consistently observed in the cross sectional transmission electron microscopy images.