Critical current properties in superconducting Y-123 tapes

The critical current density and the irreversibility field were measured for a coated Y-123 tape prepared by IBAD method. These results were compared with those of Y-123 thin film deposited on single crystal STO. It was found that J_c of the tape has a weaker magnetic field dependence, although its value at low fields is fairly lower than that of the thin film. This comes from the difference of the thickness. The lower J_c at low fields is due to the collective pinning property, and the better irreversibility at high fields can be attributed to a larger flux bundle volume. These results were compared with the calculated results using the flux creep-flow theory, and a good agreement was obtained. J_c was estimated with the aid of this theory assuming that a high-quality thick tape of 5 μm thick with strong pinning can be fabricated.