Authors:M. Mansori, C. Favotto, K. Jardet, M. Roubin, A. Sebaoun, and P. Satre
The oxygen exchange between the condensed phase(s) and the gas phase was studied as a function of temperature for superconducting
phases of the system (Bi,Pb)-Sr-Ca-Cu-O.
An oxygen probe apparatus allowed confirmation that the variation in oxygen composition in the Pb2212 and Pb2223 superconducting
phases is a reversible phenomenon on heating and cooling. It was demonstrated that the mass loss of both phases, for the 905
and 980°C isotherms, was due to the oxygen composition variation and to PbO loss (this latter phenomenon begin irreversible).
DTA-DTG systematic study of highTc superconducting phase (Bi,Pb)2Sr2CaCu2O8+x, with and without lead, shows a quantitatively opposite variation of oxygen stoechiometry on heating and cooling. Multiplate
sample container, designed for the study, allowed to dissociated PbO loss from oxygen variations.
Phases transformations have been studied under severalPO2 by scanning DTA and DTG. Oxygen variations evolution has been evaluated by isothermal TG. The results proved that phase diagram
representation must take into consideration thePO2 coordinate.