Characterization of critical current density in silver-sheathed Bi-2223 tape

The critical current property of a superconducting Bi-2223 tape produced by the over pressure processing at the final heat treatment was investigated. The critical current density increased by a factor of 1.6-1.8 at 77.3 K in comparison with the tape produced by the usual process. Thus, the critical current increased in spite of a reduction in the filament thickness. It was also found that the irreversibility field increased by a factor of 1.34 at 77.3 K by the new process. As a result, the enhancement of the critical current density at higher fields is remarkable. These results suggest that the over pressure process not only enriches the mass concentration of the superconducting phase but also contributes to the c-axis alignment. This is supported directly by the reduction of FWHM of rocking curve and indirectly by an enhancement the n value. The critical current property at lower temperatures is also investigated and the possibility of the further improvement of the property is discussed.