METHODS OF INTRODUCING LEAD INTO BISMUTH-2223 AND THEIR EFFECTS ON PHASE DEVELOPMENT AND SUPERCONDUCTING PROPERTIES

The specific method of introducing lead significantly influences the p hase development and superconducting properties of Pb-doped Bi2Sr2Ca2C u3O(x) (BSCCO-2223) Ag-sheated powder-in-tube tapes. This is demonstra ted in a study of tapes made from a series of powder mixtures containi ng the phases Bi1.8Pb(z)Sr2.0Ca1.0Cu2.0O8 (2212), Ca2PbO4, Ca2CuO3, an d CuO, where the lead content of 2212, z, was varied from 0.0 to 0.4. The overall composition of each mixture was the same, (Bi1.8Pb0.4Sr2.0 Ca2.0Cu3.0O10), and the amounts of each phase were varied to compensat e for changes in z. In an additional mixture made from lead-free 2212, Ca2CuO3, and CuO, all lead was added as PbO. A significantly more com plete 2223 formation, sharper transition temperatures, and higher crit ical current densities were seen when all lead was incorporated in the 2212 phase, rather than being added as either PbO or Ca2PbO4.