Effect of Ag on the primary phase field of the high-T-c (Bi,Pb)-2223 superconductor

The subsolidus equilibria and the primary phase field (crystallization fiel d) of the 110 K high-T-c (Bi,Pb)-2223 ([Bi,Pb]:Sr:Ca:Cu) phase have been de termined in the presence of Ag under a 92.5% Ar/7.5% O-2 atmosphere (volume fraction). A total of 29 six-phase volumes that include both the (Bi,Pb)-2 223 and Ag phases was observed. These subsolidus volumes are similar to tho se observed without the presence of Ag. The compositional range of initial melts of these volumes (mole fraction basis) covers BiO1.5 from 5.6% to 25. 3%, PbO from 0.4% to 13.8%, SrO from 8.4% to 31.9%, CaO from 12.2% to 33.3% , CuO from 21.7% to 40.9%, and AgO0.5 from 1.2% to 6.3%. Based on these dat a, the primary crystallization field for the (Bi,Pb)-2223 phase in the pres ence of Ag was constructed using the convex hull technique. A section throu gh this "volume" was portrayed by holding the AgO0.5, SrO, and CaO componen ts at the median value of the 29 compositions while allowing projection on the other three axes (BiO1.5, PbO, and CuO). The net effect of Ag on the me lt composition is a reduction in the PbO concentration and an increase in t he SrO content. Applications of the liquidus data are also discussed.