Abstract
The flux density distributions in sintered Bi2Sr2CaCu2Ox high Tc superconducting specimens Were observed by means of a magneto-optical method using iron garnet films. The samples were formed to the disks with the thickness of 60∼600μm and the diameter of 1.5 mm. SEM image showed that the specimen consists of the grains with the diameters of about 300μm. Flux penetrated inhomogeneously for the specimens with smaller thickness than the diameter of the grain. However, it penetrated homogeneous as increasing the thickness. Preferential flux penetration at grain boundaries was not observed for all specimens. The values of the critical current density, that was estimated from the flux penetration distance by using Bean's model applied to disk-shaped specimens, was about 104 A/cm2 at 30 K, Which was nearly equal to the Value estimated from magnetization assuming that the shielding current flows uniformly through the entire specimen.
