Effect of extremely fine Y2BaCuO5 precipitates on the critical current density of melt-processed YBa2Cu3Ox

Based on previously developed melt processing methods, Y2BaCuO5 (211) precipitates with various size were obtained in YBa2Cu3Ox (123). In particular, a wide distribution of 211 size from 100 A to 10 μm has been found to exist in the matrix of 123, and strongly effected the critical current density, Jc. An enhancement of Jc was always found to be associated with the presence of extremely fine 211 precipitates. The flux pinning by these precipitates can be understood by considering the interaction of flux lines with cavities. It was found that although the flux lines are strongly pinned by cavities, the effectiveness decreases with the increasing number of flux lines trapped by them.