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

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Abstract
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.