Bulk and Wire Type Y–Ba–Cu Oxide Superconductor

We have fabricated the bulk Y–Ba–Cu oxide, various types of wire conductors and coils, and especially studied the critical current density Jc. Large Jc's were obtained at 77K and OT: 725A/cm2 for the non sheath wire, 560A/cm2 for the Ag sheathed wire. However, the Jc(77K) drastically decreased by a factor of hundred in a magnetic field lower than 1T while Jc(4.2K) little changed up to 12T. Based on the magnetic field dependence of Jc, for example, 2T of upper critical field Bc2(77K) and 47 to 80T of Bc2(4.2K) were obtained for the wire conductor.