Analysis of I-V characteristics in Ag/Bi2223 tapes by weak link path model

When transport current increases in Ag/Bi2223 tapes, the electric field is moderately generated in the vicinity of its critical current (Ic), suggesting that the transition from superconducting (SC) state to non-superconducting (non-SC) state is not sharp. An origin of this behavior is suggested to be a complexity of microscopic current transport, while the transport is dominated by homophase grain boundary weak links. In order to investigate the influence of weak links on I-V characteristics of the tapes, we have proposed a two-dimensional model named Weak Link Path Model. This model consists of SC and non-SC elements linked by weak links with coordination number Z. In the present paper, the influence of Z upon I-V characteristics is clarified. From the numerical analysis based on the model, the following results are obtained; (1) The larger Z is, the higher the Ic is. (2) Large Z lattices have finite (non-zero) Ic even with smaller volume fraction (Vf) of SC phase. Consequently, it is suggested that it ...