Fabrication and properties of Bi2223 tapes with CuO barrier formed by the in situ oxidation method

Abstract

Although Ag sheathed Bi2223 tapes have the performances of I c values over 100 A and length of 1000 m which are enough for prototype applications, their AC loss is still too high for practical applications. To reduce the AC loss, the introduction of high resistive barrier between filaments and the filament twisting are effective. In this study, the Bi2223 tapes with CuO barriers between filaments were fabricated through the in situ oxidation method. Mono-core wires covered with metal Cu were stacked and deformed to form 19-filamentary tapes. These tapes were sintered, and the metal Cu layer was oxidized to form CuO barrier layer. Although the CuO grains in barrier layer easily agglomerated during sintering, the continuity of CuO barrier could be kept well by decreasing total sintering time and by the use of thick barrier layer. However the conversion ratio from Bi2212 to Bi2223 became low by increasing the barrier thickness. In addition, XRD analysis revealed that the impurity phase of (Sr, Ca) 14Cu 24O x phase easily formed in the thick barrier tape. The J c value of over 1 × 10 4 A/cm 2 at 77 K, 0 T was achieved in CuO barrier tape with the initial thickness of 20 μm. The proper control of initial thickness and sintering conditions is important to achieve high J c and good continuity of barrier.