INFLUENCES OF Y2BACUO5 PARTICLE-SIZE AND CONTENT ON THE TRANSPORT CRITICAL CURRENT-DENSITY OF YBA2CU3OX SUPERCONDUCTOR

Transport critical current density anisotropy measurements have been conducted on liquid-phase processed YBa2Cu3Ox superconductors 12(3) with differing Y2BaCuO5 (211) content and particle size. It is found that for specimens with micron-size 211 inclusions and low 211 content, the critical current density, J(c), increases with 211. In contrast, J(c) is determined to decrease with 211 content when the specimens contain large 211 particles and high volume fraction of 211. Moreover, the ability of 211 to act as pinning sites appears to diminish at moderate magnetic fields, whereas the crystal defects that are associated with the 123-211 interfaces appear to be effective pinning centers at high fields. It is proposed that the variation in J. with 211 content is not unique, but depends on the 211 content and the particle size, as well as the strength of the applied magnetic field.