The critical currents of a series of ${\mathrm{YBa}}_2{\mathrm{Cu}}_3{\mathrm{O}}_7{/\mathrm{Y}}_2{\mathrm{BaCuO}}_5$ (123-211) melt-textured ceramic composites have been measured inductively with the field applied parallel to the ab planes $\left(H\parallel ab\right)$ and compared to those previously analyzed when $H\parallel c$. In-plane vortex pinning mechanisms are analyzed from temperature and field dependence of $J_c^c\left(H\parallel ab\right)$ 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 ${\mathrm{Y}}_2{\mathrm{BaCuO}}_5$ 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 ${\mathrm{Y}}_2{\mathrm{BaCuO}}_5$ 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.

• Received 20 April 1998

DOI:https://doi.org/10.1103/PhysRevB.58.15198