CRITICAL STATE IN DISK AND RING OF Y1BA2CU3O7-DELTA CERAMIC SUPERCONDUCTOR

We have studied the critical state in the zero-field-cooled disk-shaped superconducting ceramics of Y1Ba2Cu3O7-delta at 77 K over an applied magnetic field range 0-600 G. The measurements of the diamagnetic shielding field and the trapped field profiles have been performed across the superconducting ceramic disk and pressed-powder disk, in order to determine the intergrain component of shielding and trapped field. We have applied the critical state model of Daumling and Larbalestier to explain the dependence of the intergrain component of shielding in the ceramic disk of Y1Ba2Cu3O7-delta on an applied magnetic field. Good agreement between this model and the experimental data on the intergrain shielding of the ceramic disk of Y1Ba2Cu3O7-delta has been obtained for applied fields above 100 G at which the transport critical current density shows weak dependence on applied field. Similar results were obtained for ceramic rings of Y1Ba2Cu3O7-delta.