Material for resistive barriers in Bi-2223/Ag tapes

The reactivities of several oxide materials (OM) in direct contact with BSCCO powder has been tested at a temperature of approximately 845°C in air. The OM such as BaZrO₃, SrCO₃, MgO and ZrO₂ showing little or no reactivity with BSCCO were mixed (10 wt%) with a BSCCO precursor powder and used for monocore tapes made by a standard powder-in-tube technique. The microstructure of the BSCCO+OM cores was analysed by SEM and XRD and the transport current properties-critical current, pinning force and resistance up to 16 T-were measured as a function of the magnetic field for various orientations with respect to the ab plane. The OM used influenced the electrical properties of the Bi-2223 phase in different ways. This is because the oxides react with BSCCO during the heat treatment and simultaneously affect the 2212 → 2223 phase transformation as well as the Bi-2223 grain growth and grain connectivity. Submicrometre commercial SrCO₃ powder was evaluated as the best material from all those tested, for resistive barriers in Bi-2223/Ag tapes.