銀シースビスマス系酸化物超伝導テープの特性に及ぼす拡幅圧延の影響

Abstract

Spread rolling methods are applied to a fabrication process of silver-sheathed superconductor (Bi, Pb)2Sr2Ca2Cu3Ox tapes. Two spread rolling methods are adopted. One method is the satellite-mill rolling which has been developed by the authors. The method is applied to the forming process of tapes. And the other method is a cross rolling, in which the tapes are rolled in the transverse directions. The cross rolling is applied as an intermediate rolling during the final sintering process, that is, the thin tape is pre-sintered, rolled and re-sintered.The deformation characteristics of tapes, the microstructure and the texture of the oxides are investigated. And the critical current densities JC are measured at 77 K, 0 T. In order to make clear the effect of the spread rollings, these results are compared with those by the conventional longitudinal rolling method. Main results are as follows. (1) The high lateral spread rolling is realized by the satellite-mill rolling. In the tapes produced by the satellite-mill rolling, however, the silver sheath/oxide core interface is slightly inhomogeneous, and critical current density is little lower. (2) The critical current densities of the tapes deformed by the intermediate cross rolling is several times higher than those by the conventional rolling. (3) The sintered oxide grains are elongated in the direction of intermediate rolling. The texture is the c axis\varparallelN.D. fiber texture, and the c axes are dispersed in the direction of the intermediate rolling.