Magnetic Shielding Effect of High-Tc Superconducting Plate

Magnetic shielding properties were measured at 77K in melt processed YBaCuO and Bi2228 superconducting plates. It is expected that high-Tc superconductors with high Jc can shield a relatively high magnetic field at 77K by the flux pinning effect. YBaCuO superconductors were prepared by a melt process, using a tunnel type unidirectional gradient furnace which consists of multi heating zones. It has a high critical current density at 77K and in high magnetic field. On the other hand, Bi2223 superconductors have been developed to have a high Jc value (~ 10,000 A/cm2) at 77K. Thus, the samples can shield a relatively high magnetic field. Two-dimensional distributions of flux densities over the sample surface were measured at 77K by using a Hall probe, when a magnetic field up to 30mT was applied perpendicular to the sample surface. Magnetic shielding effect of the samples was relatively uniform up to 15mT in both Y and Bi system.