FABRICATION OF HIGH-J(C) BI-2223 SINTERED BULK SUPERCONDUCTORS

Oxide superconducting calcined powder at first adsorbs atmospheric moi sture, then reacts with carbon dioxide, which deteriorate a supercondu cting property of oxide superconductor. We reconsidered a calcined pow der preparing process. It was found that moisture is easily absorbed b y the solvent removing method after the wet pulverizing method. By rem oving the solvent under reduced pressure, it was possible to reduce th e carbon content 0.03 mass% or less. The calcined powder was pressed t o a pellet 20 mm in diameter and approximately 1 mm in thickness and t hen sintered at 1093-1123 K in air with intermediate pressing by a CIP method. After the first CIP of the bulk, the orientation of the polyc rystalline greatly improved during the sintering resulted in the incre ase in density. As the number of CIP increased, the J(c) increased. Th e maximum value of J(c) was obtained when the number of CIP was three times. The J(c) of the bismuth-2223 sintered bulk of 0.2 mm(2) cross-s ection was increased to 8500 A/cm(2), with good reproducibility. After the second CIP, the orientation of the polycrystalline and the densit y of the bulk were not changed. Weak links were evaluated by a DC susc eptibility measurement of the sintered bulk. In the high J(c) sample, the peak sharpness of the differential curve of the susceptibility rev eals that the weak link among grains is improved.