Oxide barriers and their effect on AC losses of Bi,Pb(2223) multifilamentary tapes

The transverse electrical resistivity in multifilamentary Ag/Bi, Pb(2223) tapes is considerably enhanced after introducing inert oxide barriers, a new concept in which each single filament is surrounded by a highly resistive BaZrO3 layer of < 2 mu m thickness. With these oxide barriers, we have so far obtained a shift of the AC loss maximum from 5 Hz to > 100 Hz, This corresponds to a marked lowering of AC coupling losses. The highest critical current density of these tapes is actually 15'000 A/cm(2) at 77K, 0T, i,e. still below that of our tapes without barriers (35'000 A/cm(2)), The fabrication processes leading to Bi, Pb(2223) tapes with oxide barriers is described, with an emphasis on new deformation processes developed in our laboratory for the fabrication of long multifilamentary Bi, Pb(2223) tapes, comprising four roll (or two-axes) rolling and more recently, periodic pressing. The presently developed tapes with oxide barriers are promising in view of their use in transformers and cables.