E– J characteristics of Bi-2212/Ag and Bi-2223/Ag tape conductors

Abstract

We evaluated the E– J characteristics of dip-coat-processed and powder-in-tube (PIT)-processed Bi-2212/Ag and Bi-2223/Ag tapes by both the resistive and the magnetization methods. The slopes of the magnetically investigated log E–log J curves ( n-values) were almost equal to the slopes of resistively measured n-values for dip-coat-processed Bi-2212 and Bi-2223 tapes. For the PIT-processed tapes, however, the n-values obtained by the resistive method were smaller than those obtained by the magnetization method. This smaller resistively measured n-values of the PIT-processed tapes should be attributed to their inferior microstructure. No substantial difference in magnetically investigated n-values was observed between dip-coat-processed and PIT-processed tapes, which suggests that the pinning characteristics are the same for tapes prepared by these two methods. N-values of ∼20 were obtained in 10 T for dip-coat-processed Bi-2212 tapes, while larger n-values of ∼34 were obtained for dip-coat-processed Bi-2223 tapes although the J c values of the Bi-2223 tapes were much lower than those of the Bi-2212. This suggests that Bi-2223 tape is also a good candidate for the conductors of a high-field magnet operated under a persistent current mode.