The influence of processing parameters and tensile stresses on the properties of Bi-2223 tapes with Ag and AgMn sheaths

Multifilamentary Bi-2223 tapes with an inner Ag sheath immediately surrounding the filaments and an outer AgMn sheath containing 0.06-0.4 wt.% Mn have been fabricated by using the oxide-powder-in-tube technique. In some cases the filaments were additionally surrounded by a second AgPdAu sheath. The forming parameters employed to the rolling of the tapes and consequently the density evolution of the filaments during rolling were optimized aiming to avoid filament sausaging and at the same time to provide a high filament density in tapes of the final dimensions. After the parameters of the thermomechanical treatment were optimized too, similar values of the critical current densities could be achieved for tapes with a Ag/Ag-alloy sheath as for those with a pure Ag sheath. J/sub c/ values above 20 kA/cm/sup 2/ (77 K, 0 T) were measured on tapes over the whole length of 300 m. The tolerable tensile stresses and strains employable to conductors at room temperature without causing essential J/sub c/ degradation at 77 K were determined to /spl sigma//spl ap/90-110 MPa and /spl epsiv/=0.2% for tapes with an outer Ag-0.15 wt.% Mn sheath.