EFFECT OF THE 2ND-PHASE ON CRITICAL-CURRENT DENSITY IN NB-ADDED YBCO FILMS

Thin films of YBCO with or without Nb added were prepared on (100) ZrO 2 single crystalline substrate by de magnetron sputtering method. A ph ase of YBa2NbO6 was found to form not only in the target materials of YBCO but also in the sputtered thin films. The second phase of YBa2NbO 6 in the superconducting films destroyed a match relation between the lattice of YBCO and the lattice of ZrO2 substrate. The measurements of critical current density J(c) under magnetic field (H parallel to c a xis, up to 5 T) showed that the J(c) in Nb-added YBCO films reduced mo re apparently than that in YBCO films. It is concluded that the existe nce of second phase of YBa2NbO6 in superconducting phase does not play a rule of flux pinning.