Magnetic shielding properties of YBa2Cu3O7-x tubes

The magnetic shielding properties of polycrystalline YBa2Cu3O7-x, tubes have been investigated at 77 K in weak magnetic fields. Based on a detailed analysis of a grain-boundary weak-link picture of granular superconductors, their transport, magnetic field penetration, shielding and trapping behaviour are interpreted in terms of a critical state model. The correlation between properties and material structure is discussed.