CRITICAL-CURRENT DEPENDENCE ON DEFORMATION KINETICS IN TEXTURED YBA2CU3OX SUPERCONDUCTOR

The dependence of critical current on the deformation kinetics has bee n examined in melt-textured YBa2Cu3Oz superconductors that were subjec ted to uniaxial high temperature deformation. The J(c) of the deformed superconductors is found to increase with deformation time at ail mag netic field orientations with respect to the a-b plane. The rate of in crease in J(c) is found to subside after 12 h of deformation. The defo rmation time dependence of J(c) has been analyzed within the framework of high temperature creep, and is found to be very similar to the def ormation time dependence of mechanical strain. The rate of J(c) increa se in the secondary creep stage is found to be significantly higher in the orientation of H//c resulting in a lower anisotropy with increasi ng deformation time. The J(c) characteristics suggest that an anisotro pic defect structure is created after longer periods of deformation, a nd that the defects responsible for flux pinning are introduced by the rmal activation.