REDUCING AC LOSSES OF BI(2223) MULTIFILAMENTARY TAPES BY OXIDE BARRIERS

A new type of sheath material, consisting of a thin layer BaZrO3 aroun d each filament, has been used to fabricate Bi(2223) multifilamentary tapes. The transverse resistivity is enhanced by a factor of 10, thus leading to a significant reduction of ac coupling losses in Bi(2223) m ultifilamentary tapes. The electric decoupling effect of these barrier s is clearly demonstrated by ''magnetic length scale'' and Hall sensor magnetisation experiments. Moreover, it is possible to twist these ta pes with a pitch length of 2 cm, thus yielding an even higher decoupli ng effect without deterioration of the transport properties. The unifo rmity of filament size and barrier layer thickness have been improved by a modified PIT method using four-roll deformation. The critical cur rent density of these Bi(2223) tapes with BaZrO3 oxide barriers so far reaches 15kA/cm(2) (77 K, 0 T). (C) 1998 Elsevier Science B.V.