ac Losses in Bi,Pb(2223) barrier tapes Original Research Article

For many applications of Bi,Pb(2223) tapes involving alternative currents and/or fields, their ac losses are still too high. Several methods have been tried for reducing these losses and at present the most successful one is the introduction of a resistive barrier between filaments combined with filament twisting. At the University of Geneva, we tested an extensive series of different materials for their suitability as barrier materials. In this paper, we start by treating the different criteria these materials should meet for their use as barrier: no reactivity with Bi,Pb(2223) precursor, good deformability and low cost. We show why we used first BaZrO3 and later SrZrO3 as barriers and explain the differences between these two materials. We next discuss which modifications of deformation process are needed in order to have tapes with smooth and continuous barrier layers and to avoid too high a degradation of the critical current density. Finally, we show the effect of barriers on the ac losses and the effective matrix resistivity.