Sr<SUB>6</SUB>V<SUB>2</SUB>O<SUB>11</SUB>バリアをもつAgシースBi2223多芯テープ線材の作製と超伝導特性

Abstract

Ag-sheathed Bi2223 multifulamentary tapes (7 and 19 filaments) with and without Sr6V2O11(SVO) barriers have been prepared by the powder-in-tube method. The SVO barrier layers are arranged in three different configurations as inside (7 & 19SV10), outside (7 & 19SV01), and inside-outside (7 & 19SV11) of each filament. All of the barrier tapes have much higher critical-current density Jc than the non-barrier tapes (7 & 19SV00). In these cases, the compound SrCO3 contaminated in the process of SVO preparation must be eliminated in the inside-barrier tapes, and a thick-walled Ag tube must be used in the inside-outside barrier tapes with thicker barrier layers. This result will overcome the serious problem of the decrease in Jc in barrier tapes obtained so far. Furthermore, the inside barrier configuration will be possible using only SVO. The increase in Jc will be due to the enhancements of the Bi2223 phase formation and its crystal alignment by the reaction of the inside-coated SVO with a Bi-oxide core for the inside- and inside-outside barrier tapes (SV10 and SV11) and due to the reduction in oxygen partial pressure at the Bi-oxide core site during the heat treatment for the outside-barrier tapes (SV01). Furthermore, for all the barrier tapes, the transport a. c. losses at 77 K in self field are lower than those of the non-barrier-tapes. These results suggest that SVO will be one of the most important candidates for a resistive barrier with the view of a. c. applications. The inside-barrier tapes, especially, will permit the tape to be fabricated with ease and provide good potential for improving the overall Jc.