Thermochemistry of iron manganese oxide spinels

Sophie Guillemet-Fritsch, Alexandra Navrotsky, Philippe Tailhades, Hervé Coradin, Miaojun Wang

Research output: Contribution to journalArticlepeer-review

23 Scopus citations

Abstract

Oxide melt solution calorimetry has been performed on iron manganese oxide spinels prepared at high temperature. The enthalpy of formation of (Mn xFe1-x)3O4 at 298 K from the oxides, tetragonal Mn3O4 (hausmannite) and cubic Fe 3O4 (magnetite), is negative from x = 0 to x = 0.67 and becomes slightly positive for 0.67<x<1.0. Relative to cubic Mn 3O4 (stable at high temperature) and cubic Fe 3O4 (magnetite), the enthalpy of formation is negative for all compositions. The enthalpy of formation is most negative near x = 0.2. There is no significant difference in the trend of enthalpy of formation versus composition for cubic (x<0.6) and tetragonal (x>0.6) spinels of intermediate compositions. The enthalpies of formation are discussed in terms of three factors: oxidation-reduction relative to the end-members, cation distribution, and tetragonality. A combination of measured enthalpies and Gibbs free energies of formation in the literature provides entropies of mixing. ΔSmix, consistent with a cation distribution in which all trivalent manganese is octahedral and all other ions are randomly distributed for x>0.5, but the entropy of mixing appears to be smaller than these predicted values for x<0.4.

Original languageEnglish (US)
Pages (from-to)106-113
Number of pages8
JournalJournal of Solid State Chemistry
Volume178
Issue number1
DOIs
StatePublished - Jan 2005
Externally publishedYes

Keywords

  • Calorimetry
  • Heat of formation
  • Oxide melt

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Ceramics and Composites
  • Condensed Matter Physics
  • Physical and Theoretical Chemistry
  • Inorganic Chemistry
  • Materials Chemistry

Fingerprint Dive into the research topics of 'Thermochemistry of iron manganese oxide spinels'. Together they form a unique fingerprint.

Cite this