Pb-Distribution in a Five-Phase (Bi, Pd)-Sr-Ca-Cu-O Assemblage
Lawrence P. Cook, Winnie K. Wong-Ng
The partitioning of lead between phases in the nominal five-phase assemblage: (Pb,Bi)3Sr2Ca2CuOx + (Ca,Sr)2PbO4 + (Bi,Pb)2Sr2CaCu2Ox + (Ca,Sr)O + Liquid has been investigated in an atmosphere of 7.5% O2925% Ar. Samples were studied using a combination of high temperature quenching, simultaneous differential thermal analysis and thermogravimetric analysis, scanning electron microscopy, and energy dispersive x-ray analysis. Results indicate a strong partitioning of lead relative to bismuth into the (Pb,Bi)3Sr2Ca2CuOx and (Ca,Sr)2PbO4 phases, for which the average Pb/(Pb + Bi) ratios were determined to be 0.73 and 0.85, respectively. In the (Bi,Pb)2Sr2CaCu2Ox and Liquid phases, the average Pb/(Pb + Bi) ratios were much lower, 0.14 and 0.24, respectively. This indicates an apparent saturation of Pb in the (Bi,Pb)2Sr2CaCu2Ox superconductor at a relatively low level. Data on Sr/(Sr+Ca) ratios for coexisting phases are also presented, along with a thermodynamically-derived projection of the 5-component data for the coexisting phases.
Proceedings Of ACerS
May 1, 1997
BSCCO, five phase assemblage, high Tc superconductors, lead distribution, phase equilibria