Entropy of oxidation and redox energetics of CaMnO3-delta

The heat capacities of CaMnO3 and CaMnO2.562 from 10 to 600 K are determined by adiabatic calorimetry and used to derive an average entropy for the following oxidation reaction 4CaMnO2.50 + 02(g) = 4CaMnO3 The redox energetics of CaMnO3-5 is analysed using four independent sets of experimental data:...

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Bibliographic Details
Published in:Solid state ionics 2005-09, Vol.176 (29-30), p.2261-2267
Main Authors: Bakken, Egil, Boerio-Goates, Juliana, Grande, Tor, Hovde, Beate, Norby, Truls, Rormark, Lisbeth, Stevens, Rebecca, Stolen, Svein
Format: Article
Language:English
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Summary:The heat capacities of CaMnO3 and CaMnO2.562 from 10 to 600 K are determined by adiabatic calorimetry and used to derive an average entropy for the following oxidation reaction 4CaMnO2.50 + 02(g) = 4CaMnO3 The redox energetics of CaMnO3-5 is analysed using four independent sets of experimental data: the entropy of oxidation reported here, the enthalpy of oxidation previously determined by reaction calorimetry and by coloumetric titration as well as data for the oxygen stoichiometry of CaMnO3-delta as function of partial pressure of oxygen and temperature. We show very clearly the importance of experimental data for the non-configurational entropy. A solution model, in which a random distribution of oxygen atoms and oxygen vacancies on the 0sub-lattice is the main contribution to the structural disorder, largely reproduces the experimental data. The analysis furthermore suggests an energetic preference for square pyramidal coordination for manganese in CaMnO3-delta.
ISSN:0167-2738
DOI:10.1016/j.ssi.2005.06.009