In-plane flux pinning in melt-textured YBa2Cu3O7-Y2BaCuO5 composites

The critical currents of a series of YBa2Cu3O7/Y2BaCuO5 (123-211) melt-textured ceramic composites have been measured inductively with the field applied parallel to the nb planes (H parallel to ab) and compared to those previously analyzed when H parallel to c. In-plane vortex pinning mechanisms are analyzed from temperature and field dependence of J(c)(c)(H parallel to ab) in samples with different concentration of 211 particles. A hierarchy of pinning centers has been identified and analyzed: 123/211 interfaces, dislocations, stacking faults, and twin boundaries. We show that the interface of the secondary phase Y2BaCuO5 with the superconducting matrix plays an important role in pinning the Josephson vortices though with a reduced efficiency as compared to Abrikosov vortices. In addition, we identify a second contribution to flux pinning which is independent of V/d, i.e., the amount of interface between the Y2BaCuO5 particles and the matrix, that we associate with in-plane linear defects, such as dislocations and partial dislocations surrounding the stacking faults. Finally, the contribution to the pinning of Josephson vortices from twin planes has also been evaluated. [S0163-1829(98)03446-8].