Superconducting Properties of Ho-Ba-Cu-O and Er-Ba-Cu-O Bulk Superconductors

摘要

We investigated the superconducting properties of melt-textured Ho123 and Er123 bulk superconductors containing 5 to 40 mol% Ho211 and Er211, respectively. The samples were fabricated with the cold-seeding method in air using a Nd123 bulk seed crystal. The superconducting properties of the Ho-Ba-Cu-O samples were strongly affected by the Ho211 content and oxygen anneaing temperature. In the J_c-B curves of the Ho123 samples with low Ho211 contents, a secondary peak effect was clearly observed. The peak position shifted to lower fields as oxygen annealing temperature increased, presumably due to an incrase in oxygen vacancies. A secondary peak effect was also found in the Er123 sample with 5 mol% of Er211. We believe that the peak effect in these materials is ascribed to oxygen deficiency, since RE/Ba substitution is not present in either system.