Primary phase field of the Pb-doped 2223 High-T-c superconductor in the (Bi, Pb)-Sr-Ca-Cu-O system

Both liquidus and subsolidus phase equilibrium data are of central importan ce for applications of high temperature superconductors in the (Bi, Pb)-Sr- Ca-Cu-O system, including material synthesis, melt processing and single cr ystal growth. The subsolidus equilibria of the 110 K high-T-c Pb-doped 2223 ([Bi, Pb], Sr, Ca, Cu) phase and the location of the primary phase field ( crystallization field) have been determined in this study. For the quantita tive determination of liquidus data, a wicking technique was developed to c apture the melt for quantitative microchemical analysis. A total of 29 five -phase volumes that include the 2223 phase as a component was obtained. The initial melt compositions of these volumes range from a mole fraction of 7 .3 % to 28.0 % for Bi, 11.3 % to 27.8 % for Sr, 1.2 % to 19.4 % for Pb, 9.8 % to 30.8 % for Ca, and 17.1 % to 47.0 % for Cu. Based on these data, the crystallization field for the 2223 phase was constructed using the convex h ull technique. A section of this "volume" was obtained by holding two compo nents of the composition at the median value, allowing projection on the ot her three axes to show the extent of the field.