| 摘要 |
A description is given of a black superconducting material having the overall composition Bi4 (Sr, Ca)yCuzO delta , where z = 2-3, y = 4-6 and Sr/Ca is 1:1 to 10:1. It contains at least 10% by weight of a superconducting phase of the general formula Bi4+x-(Sr, Ca)5-xCu3O4+ delta , where x is between 0 and 0.7, in particular 0.1 and 0.4, which has a crystallographic unit cell having the dimensions a=5.4.10<-8>cm, b=5.39.10<-8>cm, and c=27.4.10<-8>cm, the Sr/Ca atomic ratio being 1:1 to 10:1. The critical temperature of the superconductor is not less than 80K. To produce the material, oxides of Bi, Sr, Ca, and Cu are melted in molar ratios corresponding to the overall composition, the melt is allowed to solidify, the solidified melt is heat-treated in an atmosphere containing 5 to 15% by volume of O2 at a temperature of not less than 750 DEG C but below the melting point of approximately 880 DEG C, and then it is cooled to room temperature. <IMAGE> |
