PURPOSE: To obtain the superconductor having high critical current density by specifying the resistance of a polycrystalline oxide superconductor consisting essentially of rare-earth element-Ba-Cu-O toward the intrusion of a magnetic flux resulting from an effective magnetic field.
CONSTITUTION: The polycrystalline oxide superconductor consists essentially of the material shown by formula I (RE is rare-earth elements). The intrusion of a magnetic flux resulting from an effective magnetic field into the superconductor at 77°K is caused in the magnetic field at ≥100 G. The superconductor has a high critical current density of ≥ about 3000A/cm2. Meanwhile, the degree of orientation of the superconductor shown by equation II (P (oriented sample) by equation III and P0 (unoriented sample) by equation IV) in the X-ray chart is preferably controlled to ≥0.4, and high magnetic field and critical current density are exhibited as the degree of orientation is increased. Furthermore, the magnetic shielding effect is further increased by using this oxide superconductor for a magnetic shield, and the reliability in measurement of various measuring instruments is enhanced.
UEHARA KOICHI
IMURA HIROMI
NAGANO SABURO
