Critical current of high Tc superconducting Bi223/Ag tapes

The magnetic field dependence of the critical current of various high Tc superconducting Bi2223/Ag tapes indicates that the transport current is carried through two paths: one is through weakly-linked grain boundaries (Josephson junctions); another is through well-connected grains. The critical current flowing through the weakly-linked grain boundaries, ICw, can be characterized by the Fraunhofer-pattern, taking into account the distribution of junction dimension in the tapes. The critical current along the path of well-connected grains, ICs, is a complex exponential function of the applied field depending on the pinning strength in the grains.