THERMOGRAVIMETRIC STUDY OF RARE-EARTH MANGANITES SMMNO3, DYMNO3, YMNO3, ERM O3, YBMNO3 AT 1200-DEGREES-C

The free energy changes of formation of SmMnO3, DyMnO3, YMnO3, ErMnO3 and YbMnO3 were determined to be -14.3, -11.1, -11.4, -11.2 and -10.5kcal/mol, respectively, at 1200°C on the basis of the equilibria. Simultaneously, the nonstoichiometry was also investigated in the oxygen partial pressure below logPO2[atm]=0. The free energy change and the width of nonstoichiometry in these ternary oxides were revealed to be dependent on the radius of rare earth ion. YbMnO3 showed no deviation from stoichiometry in contrast with LaMnO3. © 1979.