Phase formation of high-T sub c superconducting oxides in the Bi-Pb-Sr-Ca-Cu-O glass

Abstract

Since the discovery of high-temperature superconductivity in the Bi-Sr-Ca-Cu-O (BSCCO) system, substantial research efforts have been expended in the areas of phase equilibria, processing, characterization, physical property measurement, and practical applications of these materials. This paper reports that one advantage of BSCCO materials, as compared to Ba-Y-Cu-O (BYCO) ceramics, is the presence of phases exhibiting superconducting properties at 80 and 110 K. The principal attribute of BSCCO, however, is the apparent absence of weak-link behavior in this material, a problem which can severely limit critical currents in bulk BYCO. The BSCCO system also offers the opportunity of glass formation so that glass-ceramic processing techniques can be used to form and crystallize materials into the desired products. An interesting problem exists with respect to forming the 110 K (Bi,Pb){sub 2}Sr{sub 2}Ca{sub 2}Cu{sub 3}O{sub x} (2223) phase in the BSCCO system. Efforts to obtain this 2223 phase directly from the lead-free Bi-Sr-Ca-Cu-O system have been largely unsuccessful, although reports have been made to the contrary. The addition of Pb to the starting materials has been found necessary to achieve significant quantities of 2223.