DISTRIBUTION OF THE TRANSPORT CRITICAL-CURRENT DENSITY IN AG SHEATHED (BI,PB)2SR2CA2CU3OX TAPES PRODUCED BY ROLLING

By using a strip-cutting technique, we directly measured the lateral distribution of the transport critical current density of Ag sheathed (Bi, Pb)2Sr2Ca2Cu3O(x) tapes. For various long tapes prepared by the rolling technique with a critical current density of 23 000 A/cm2 at 77 K and 0 T, the local critical current density of longitudinal 0.2 mm wide strips was reproducibly found to vary from 18 000 A/cm2 at the center to 46 000 A/cm2 at the sides of the filament. In all cases, a symmetrical behavior of j(c) at both sides of the central axis was observed. The value of the transport j(c) of 46 000 A/cm2 at 77 K and 0 T in the external strips of Bi(2223) tapes produced by rolling processes comes quite close to the highest reproducible values reported so far on short pressed tapes. The field dependence of the critical current densities of the individual strips does not depend on their position inside the tape. Thus the observed difference in j(c) between central and external strips is not primarily due to a variation of the degree of texturing. A higher degree of compression and a lower amount of secondary phases were found for the external strips with the highest critical current density.