The influence of the first heat-treatment on the critical current density of (Bi,Pb)-2223/Ag superconducting tapes

摘要

Optimization heat-treatments have been performed on multi-filament Bi-2223/Ag superconducting tapes under 1 bar total gas pressure, the oxygen partial pressure being 8.5 percent. In a first heat-treatment (HT1), the tapes were sintered within 822-838 deg C for 1-50 h. After intermediate deformation, all the samples underwent the second heat-treatment (HT2) at 825 deg C and 830 deg C for 20 h followed by a thermal sliding procedure. The relative content of the phases present in HT1 samples was measured by XRD. It was found that the Bi-2212 phase content after HT1 strongly influences the values of J_c after HT2. There is a correlation between the amount of Bi-2212 phase after HT1 and the final J_c values after HT2. A maximum of Jo was found for a ratio of 0.15 between Bi-2212 and Bi-2223.