The high field magnetic dependence of critical current density at 4.2 k for ag-sheathed Bi₂Sr₂CaCu₂O_y superconducting tape

Critical current density (J_c) at 4.2 K and its dependence on applied magnetic field was measured for Ag-sheathed Bi₂Sr₂CaCu₂O_y superconducting tape. The specimen showed a strong grain alignment which could be attained by adjusting the conditions of heat treatment. The degree of crystal orientation (F) was evaluated to be up to 95% by XRD for this specimen. In the case of magnetic field applied in a direction parallel to the tape, the J_c initially decreased with the magnetic field from 1.2×10⁵ A/cm² at 1 T to 5×10⁴ A/cm² at 10T and then remained almost constant up to 23 T. As the F value decreased from 95%, J_c also decreased. The pinning force (F_p) of the 95%-F-value tape was estimated to be about 1×10¹⁰ N/m³ at 23 T. This value is larger than those of conventional low-T_c superconductors.