Theoretical issues for critical currents of bulk polycrystalline YBa2Cu3O7−δ superconductors

The influence of grain orientation and weak-link coupling between grains on the critical current of polycrystalline Y-Ba-Cu-O superconductors has been investigated by numerical methods. The theoretical results indicate that there is size effect on jC in bulk polycrystals, and that it is not necessary to consider the influence of grain orientation when jC is less than 105 A/cm2.