Characterization and Critical Current Density Determination of High-Tc Superconductor Ba-Y-Cu Oxide

X-ray diffraction is used to characterize a sintered specimen of Ba-Y-Cu oxide which has zero resistance below 91 K and a diamagnetic susceptibility, χ, as large as 43% of the perfect diamagnetism at 84 K. About 90% of the specimen volume is found to be Ba 2 YCu 3 O x . The critical current densities under zero applied magnetic field are measured to be 105 A/cm 2 at 77 K and 300 A/cm 2 at 4.2 K. The influence of machining of the specimen on χ is investigated. Pulverization of the sintered bulk reduces χ/(-1/4π) from 43% to 14% at 84 K. This reduction is recovered by a subsequent thermal annealing.