Effect of V, Ir-doping on the J/sub c/ properties of Bi2223 tapes

We prepared Ag-sheathed mono-core tapes and multifilamentary tapes with 19 filaments by the powder-in-tube method, using V- and Ir-doped Bi2223 powder with a doping amount x less than 0.15. In the doped tapes two effects are overlapped: One is the decrease in J/sub c/ due to some weak links caused by precipitates such as Sr-V-O oxides, and the other is the increase in J/sub c/ with the doping content due to the enhancement of Bi2223 phase formation. This results in a minimum in J/sub c/ at x=0.05. The second effect becomes stronger in the V-doping, because of the great enhancement of Bi2223 phase formation. In the Ir-doped tapes the J/sub c/ values decrease monotonically with the doping content. For the multifilamentary tapes the V-doping is very effective to obtain high I/sub c/ values.