|Budget Amount *help
¥3,300,000 (Direct Cost : ¥3,300,000)
Fiscal Year 1998 : ¥900,000 (Direct Cost : ¥900,000)
Fiscal Year 1997 : ¥2,400,000 (Direct Cost : ¥2,400,000)
Bi_2Sr_2CaCu_2O_<8+x> (Bi-22 12) superconductors have been synthesized by the diffusion reaction between a high melting point Sr-Ca-Cu oxide substrate and a low melting point Bi-Cu oxide coating layer with Ag2O addition. The Bi-22 12 diffusion layer, formed around both outside and inside of the cylindrical tube of 20/16mm in outerfmner diameter, shows dense and oriented structure with plate-like grains. The transport Jc of the diffusion layer, about 150mum in thickness, exceeds 20,000 A/cm_2 at 4.2K under self-field. The transport Ic of the whole tube is estimated to be about 4,000 A.Post annealing in Ar gas atmosphere improves Tc of the diffusion specimen by about 10K.Therefore, the transport Ic increases at temperatures higher than 40K in comparison with that of the as diffused specimen. The contact resistivity of the bulk ends is in order of 1-10 n(2cm2 between at 4.2K and 65K up to 3T.Consequently, the joule heating in the current terminals of the specimen is expected to be as small as 1mW for the transport current of 1,000 A.Present Bi-22 12 oxide cylinders with large transport Ic and Jc as well as low contact resistance may be promising as current leads and conductors.
Furthermore, Bi-2212 oxide superconducting layer has been synthesized around cylinder by the dip-coating and subsequent diffusion reaction between Sr_2CaCu_3 oxide substrate and Bi_2Cu_<0.136> eutectic oxide. The transport Jc of the diffusion layer, about 120mum in thickness, is as high as 25,000 A/cm_2 at 25K under self-field. The dip-coating process is more simple for the fabrication of Bi-22 12 oxide layer compared with the conventional slurry-coating process.