Limiting current mechanisms of Bi2223 wires in magnetic fields

Abstract

Controlled overpressure (CT-OP) processing eliminates pores and heals cracks, whichdensifies the Bi2223 filaments and increases the critical current of Ag-sheathed Bi2223 wire.High current capacity wires with critical current values around 210 A at 77 K and self-fieldhave been achieved. The enhancement of the current capacity seems to be due to reducingthe weak links between Bi2223 grains and improving the flux pinning. In order tounderstand the mechanisms for transport critical current in Bi2223 wires, the dependenceof the critical current on magnetic field and temperature has been investigated. The criticalcurrent is measured as a function of the perpendicular and parallel magnetic fields, up to12 T, at temperatures ranging from 4.2 to 90 K. These results indicate that higher criticalcurrent is associated with highly textured and well connected Bi2223 grains. Tofurther improve a critical current of Bi2223 wires, it is necessary to decrease themisalignment angle and reduce the fraction of Bi2212 and secondary phases.