Evidence of Enhanced Flux Pinning by Dislocations in Deformed Textured Y₁Ba₂Cu₃O_xSuperconductor

Abstract

As-melt and uniaxially deformed melt textured YBCO (123) superconductors 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 both as-melt and deformed superconductors are found to have decreased dramatically both in zero field as well as in an applied field of 1.5 T. Furthermore, the distinct characteristic of deformed superconductors, i.e., J c ( H|| c -axis)≈ J c ( H|| a - b ), has totally disappeared after annealing the samples at 900° C for 48 h in flowing oxygen. Transmission electron microscopy revealed that the high dislocation density normally observed in deformed 123 superconductors has been 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 effective flux pinning centers in these superconductors. Meanwhile, it is suggested that pinning by stacking faults is magnetically sensitive where the effect is maximum at low fields.