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 surround ing the filaments and an outer AgMn sheath containing 0.06 - 0.4 wt.% Mn ha ve been fabricated by using the oxide-powder-in-tube technique. In some cas es the filaments were additionally surrounded by a second AgPdAu sheath. Th e 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 filamen t density in tapes of the final dimensions. After the parameters of the the rmomechanical 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(c) values above 20 kA/cm(2) (77 K, 0 T) were measured on tapes over the whole length of 300 m. The tolerable tensil e stresses and strains employable to conductors at room temperature without causing essential J, degradation at 77 K were determined to sigma approxim ate to 90 - 110 MPa and epsilon = 0.2 % for tapes with an outer Ag-0.15 wt. % Mn sheath.