Bi(Pb)-Sr-Ca-Cu-O superconducting composite tapes prepared by the powder method using an Ag sheath

The Bi-based oxide superconducting tapes containing high-Tc (Tc=110 K) and low-Tc(Tc=85 K) phases were prepared by the powder metallurgy method using an Ag sheath, and Jc was measured at 77 and 4.2 K in magnetic fields up to 30 T. A grain-oriented microstructure with the c axes perpendicular to the tape surface was obtained for the tapes with a high-Tc phase by applying a combination of cold rolling and sintering. Jc of the high-Tc tape was significantly improved by this grain orientation. However, large anisotropy in Jc with respect to the magnetic field direction was observed for these textured tapes. For the low-Tc tapes, it was difficult to obtain a grain-oriented microstructure by the cold rolling and sintering process. However, Jc at 4.2 K of the nontextured low-Tc tape is as high as that of the grain-oriented high-Tc tape. Typical Jc values at 4.2 K were above 104A/cm2 at 12 T for both high- and low-Tc tapes. Jc at 4.2 K of the Bi-based tapes is much less sensitive to the magnetic field than the conventional metallic superconductors, which indicates that the Bi-based oxide is a good candidate for the high-field superconducting magnet.