DEFECT STRUCTURES IN YBA2CU3O7-DELTA WITH ENHANCED PINNING AT LOW FIELDS

The defects present in a sample of YBa2Cu3O7-delta, which has been prepared by the chemical decomposition of YBa2Cu4O8, are examined in detail in an attempt to ascertain with a high degree of probability which of them is primarily responsible for the enhanced flux pinning at low fields. The CuO precipitates are not significant in this regard as they are not numerous enough and produce little if any strain in the surrounding matrix. Imperfections in the twin boundaries are also found to have little if any contribution to pinning in this material. It appears that the partial dislocations bounding stacking faults in the material are the major contributor to the flux pinning as has been suggested previously in the literature.