Critical current density significantly enhanced by hot pressing in Bi-2223/Ag multifilamentary tapes

Ag-sheathed Bi-2223 multifilamentary tapes were prepared with a hot-pressing technique to study its effect on grain connectivity. The critical current density (Jc(B = 0)) after hot-pressing was significantly enhanced with the maximum increase reached more than double that before. Hot pressing raised the Jc(B=0) from 22,000 A cm-2 to 56,800 A cm-2 for 81-filament tape. However, the critical current density in an applied magnetic field (Jc(B)) was not improved by hot-pressing. The Jc(B) in a magnetic field of 1 T decreased from 33% of Jc(B=0) for the original tape to 21% of Jc(B=0) for the hot-pressed tapes before and after hot pressing. The fraction of strong links (IC05/IC0) was improved from 64% to 73% for the 81-filament tape as a result of hot pressing. Microstructural analysis showed that hot pressing chiefly improved grain connectivity, increased core density, recovered microcracks and reduced secondary phase impurities. (author)