Studies on oxygen dissociation pressure of LnMnO3 (Ln = rare earth) with the e.m.f. technique

Phase Equilibrium in the System Ln–M–O

“…The DG1 value for reaction (2) is À62.2 kJ/mol, and this value shows fairly close agreement with À61.5 kJ/mol (26). The present value is larger than those of À85.3 for LaMnO 3 , and À71.3 for NdMnO 3 , as would be expected from the higher oxygen partial pressure in equilibrium.…”

Phase Equilibrium in the System Ln–Mn–O IV. Ln=Sm at 1100°C

“…Although only four data have been obtained so far, the figure indicates a linear relation between DG1 and the ionic radius. The same phenomenon at 1273 K was found by Atsumi et al (27).…”

Enthalpies of Formation of La1−xAxMnO3±δ (A=Ca and Sr) Measured by High-Temperature Solution Calorimetry

“…This is far less exothermic than !340.5 and !293.0 kJ/mol O previously found for CaMnO \B and SrMnO \B , respectively (20). However, this is indeed expected as reaction [10] also involves the formation of cation vacancies (LaMnO >B can alternatively be described as La >B Mn >B O to point out the presence of cation vacancies). In addition La O is also more acidic than CaO and SrO, and a lower stability of Mn(IV) in LaMnO >B relative to CaMnO /SrMnO is expected.…”

“…From the enthalpy of oxidation of lanthanum manganite, Eq. [10], the enthalpy of formation from the binary oxides of the stoichiometric phase (LaMnO ) is found to be !51.9$8.2 kJ/mol at 993 K. Thermodynamic data for the binary oxides were taken from Barin (27). The enthalpy is in good accord with the data obtained by decomposition measurements by Atsumi et al (10) (!51.7 kJ/mol at 1000 K).…”