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.