抄録
Microstructure was primarily determined by the composition ratio in Ag-sheathed Bi2Sr2Ca(1-x)Cu(2-x)Oy superconducting tape. The cation ratio of the raw powder was kept low in Ca and Cu compared to the stoichiometric Bi-2212 composition in order to suppress the second phase such as the coarse Sr-Ca-cuprate phase during the partial melting process. A highly aligned Bi-2212 phase with a small amount of Bi-2201 phase was obtained for the composition of x=0.36. No impurity phases were observed in the boundaries of the Bi-2212 phase by transmission electron microscopy. The best Jc of 1.67×105A/cm2 at 4.2K in zero magnetic field was obtained for the Ag-sheathed tape with the x=0.36 composition. The pancake coils were prepared by the wind-and-react technique. At liquid helium temperature, the sixteen-stacked pancake coils generated a magnetic field of 2.25 Tesla (T). The Ic of the magnet at temperatures from 4.2 to 30K coincided with the Ic of the short tape up to 6T. The evaluation of stability for the steadystate operational current was carried out using the quadruple pancake coil in various temperatures. The maximum stable operational current in a cryogenic atmosphere was a value between Ic defined as the criteria of 1μV/cm and 10-13Ω·m.
