Temperature dependence of the intragrain critical current density in polycrystalline Ag-sheathed Bi(2223) tapes

The temperature dependence of the intrinsic (Bi,Pb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub 10/ current density has been evaluated inside Ag sheathed tapes. By comparing transport and magnetic measurements performed on multifilamentary (Bi,Pb)/sub 2/Sr/sub 2/Ca/sub 2/Cu/sub 3/O/sub 10/ tapes, we individuate a domain of the H-T plane where the current density is limited by the quality of the boundaries between neighboring grains and the tape behaves as a granular superconductor and, on the contrary, the domain where it behaves like a single crystal. At temperatures below 30 K in absence of applied fields, we find that the intragrain current density is about an order of magnitude larger than the transport current density.