Thermogravimetric Study of the Ln2O3–Co–Co2O3 System. VI: Ln=Pr at 1100 and 1150°C

Phase equilibria in the system Pr–Co–O at 1100 and 1150°C are established by changing the oxygen partial pressure from 0 to 12.00 in -log(PO2/atm), and a representative phase diagram at 1100°C is presented for the Pr2O3–Co–CO2O3 system. Under experimental conditions, the PrO1.63+(), Pr2O3, CoO, Co, Pr2CoO4, Pr4Co3O10, and PrCoO3 phases are present at both temperatures. The stoichiometric Pr2CoO4 is not stable. The nonstoichiometry of the compounds, Pr2CoO4, Pr4Co3O10, and PrCoO3 is represented with respect to the oxygen partial pressure, and activities of the components in the solid solutions are calculated using the composition–oxygen partial pressure relations obtained. The standard Gibbs energy changes of the reactions in the phase diagrams are calculated and their linearity with temperature is confirmed under the present experimental conditions.