Thermodynamic properties of manganese oxides

Sophie Fritsch, Alexandra Navrotsky

Research output: Contribution to journalArticlepeer-review

118 Scopus citations

Abstract

Transposed temperature drop calorimetry and high-temperature drop solution calorimetry in molten 2PbO· B2O3 at 977 K were used to study the energetics of some manganese oxides, namely pyrolusite (MnO2), bixbyite (Mn2O3), hausmannite (Mn3O4), and manganosite (MnO). The enthalpies of oxidation at 298 K in the manganese-oxygen system, which were determined by appropriate thermodynamic cycles, were (in kJ/mol of oxygen): -441.4 ± 5.8 for the reaction 6MnO + O2 → 2Mn3O4, -201.8 ± 8.7 for the reaction 4Mn3O4 + O2 → 6Mn2O3, and -162.1 + 7.2 for the reaction 2Mn2O3 + O2 → 4MnO2. These values agreed very well with previous data that were obtained using equilibrium measurements that were reported in the literature. Thus, direct calorimetric measurements were well suited to obtain reliable enthalpy of formation data for oxides that contain manganese in the 2+, 3+, and 4+ states. Using these new values of enthalpies and reliable standard entropies, the phase-stability diagram of the manganese-oxygen system was constructed.

Original languageEnglish (US)
Pages (from-to)1761-1768
Number of pages8
JournalJournal of the American Ceramic Society
Volume79
Issue number7
DOIs
StatePublished - Jul 1996
Externally publishedYes

ASJC Scopus subject areas

  • Ceramics and Composites
  • Materials Chemistry

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