Determination of the intragrain critical current density of the Bi(2223) phase inside Ag-sheathed tapes

Abstract

Multifilamentary Ag-sheathed tapes, prepared by the powder-in-tube method, have been characterized by both transport and magnetic techniques at temperatures T between 4.5 K and 85 K in a magnetic field up to 15 T, with the aim of studying the residual presence of a granular behaviour over this wide H-T range. From a comparison between these measurements we have determined a domain of the H-T plane where the current density is still limited by the quality of the boundaries between adjacent grains and the polycrystalline superconductor behaves as a granular one and, on the contrary, the temperature region where it behaves like a strongly connected body. Finally, the temperature behaviour of the intrinsic Bi(2223) current density has been evaluated. At temperatures below 30 K in zero applied field, the intragrain current density is at least an order of magnitude higher than the transport current density.