EVIDENCE OF ENHANCED FLUX-PINNING BY DISLOCATIONS IN DEFORMED TEXTURED Y1BA2CU3OX SUPERCONDUCTOR

As-melt and uniaxially deformed melt textured YBCO (123) superconducto rs have been used to examine the role of dislocations in flux pinning. These superconductors were subjected to a high temperature annealing process. After annealing, the critical current densities (J(c)) of bot h as-melt and deformed superconductors are found to have decreased dra matically both in zero held as well as in an applied field of 1.5 T. F urthermore, the distinct characteristic of deformed superconductors, i .e., J,IH parallel to c-axis) approximate to J(c) (Hlia-b), has totall y disappeared after annealing the samples at 9000C for 48 h in flowing oxygen. Transmission electron microscopy revealed that the high dislo cation density normally observed in deformed 123 superconductors has b een significantly reduced. In addition, several other microstructural changes were also investigated. These results indicate that the large amount of dislocations generated during the deformation process are el f ective 8ux pinning centers in thes e superconductors. Meanwhile, it is suggested that pinning by stacking faults is magnetically sensitive where the effect is maximum at low fields.