Magnetic field dependence of Y-123 coated conductor and Bi-2223 tape at 4.2 K

We evaluated the dependence of the critical current (I_c) and index number (n) of Y-123 and Bi-2223 tapes on the magnetic field up to 17 T at 4.2 K, in order to explore their possible application for high field magnet. We observed that the I_c and n values depended on the magnitude and direction of the magnetic field for the Y-123 tape, whereas in the case of Bi-2223 tape, the I_c depended on the magnetic field but the n did not significantly depend on the magnitude of the field. It is to be noted that, for the Y-123 tape, the I_c(B) characteristics showed highly anisotropic behavior: the I_c decreased nearly linearly in an increasing parallel field and approximately 45% of the I_c (1.071 A/cm-width in a self-field) was retained at 17 T, whereas it decreased exponentially and only 14% of the I_c was retained in a perpendicular field at 10 T. In addition, no hysteric behavior was observed in the Y-123 tape when the fields were applied in increasing and decreasing paths, which is in remarkable contrast with the hysteretic behavior observed in the Bi-2223 tape. In the case of the Y-123 tape, the n decreased with increasing magnetic field and varied in the range of 16.8-49.7 in a parallel field ranging from 0 to 17 T and 5.2 to 45.2 in a perpendicular field ranging from 0 to 9 T. For the Bi-2223 tape, on the other hand, the n did not significantly depend on the magnitude of the field and the mean value and standard deviation were 24.5 and 5.3, respectively, in the range of 0-17 T.