Progress in critical current density of long Bi(2223) tapes deformed by periodic pressing

Critical current densities of multifilamentary Ag-sheathed Bi(2223) up to about have been achieved at 77 K and self-field for lengths of several metres using a new route: periodic pressing. This corresponds to an increase by 30-40% compared with the values obtained for conventionally rolled tapes starting with the same powders. Several pressing steps have been introduced during the anneal instead of only the standard rolling step (based on previous studies performed on both mono- and multifilamentary tapes). In contrast to earlier attempts by pressing techniques, periodic pressing is a practical and scaleable process for the fabrication of long lengths of Bi(2223) conductor as the standard intermediate rolling step. Engineering critical current densities of have successfully been obtained for tapes with high filling factor (40%). Because of the possibility of applying three or four pressing steps during the whole annealing period, the choice of the first annealing time becomes less stringent, which may constitute an advantage.