PINNING MECHANISMS IN AG-SHEATHED BI(PB)SRCACUO TAPES

The pinning properties of Ag-sheathed (Bi,Pb)2Sr2Ca2Cu3O10+y (2223) wires have been studied in comparison with the normal powder, and the powder scraped from the 2223 tape by the measurements of irreversibility lines (IL). The IL for both the tape and the powder scraped from the tape are nearly equally shifted to higher temperatures in comparison with that for the normal powder. This indicates that the enhanced IL is attributable to the defect pinning. TEM studies reveal that the grains within Ag-clad 2223 tape contain high concentrations of dislocations (10(10)/CM2 ) and stacking faults that may act as effective pinning sites. The results on the transport and magnetisation J(c) suggest that the critical current is controlled by flux pinning at high temperatures, while the weak links limit the critical current at low temperatures.