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

The transverse electrical resistivity in multifilamentary Ag/Bi, Pb(2223) t apes 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 f ar obtained a shift of the AC loss maximum from 5 Hz to > 100 Hz, This corr esponds to a marked lowering of AC coupling losses. The highest critical cu rrent density of these tapes is actually 15'000 A/cm(2) at 77K, 0T, i,e. st ill below that of our tapes without barriers (35'000 A/cm(2)), The fabricat ion processes leading to Bi, Pb(2223) tapes with oxide barriers is describe d, with an emphasis on new deformation processes developed in our laborator y for the fabrication of long multifilamentary Bi, Pb(2223) tapes, comprisi ng four roll (or two-axes) rolling and more recently, periodic pressing. Th e presently developed tapes with oxide barriers are promising in view of th eir use in transformers and cables.