Energetics of brannerite-type solid solutions: The system MnV2O6LiMoVO6Mo2O6

K. Mocala, A. Navrotsky

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

Brannerite-type solid solutions in the system MnV2O6LiMoVO6Mo2O6 (MnLif{cyrillic}) were studied by high-temperature drop-solution calorimetry and X-ray diffraction. Enthalpies of mixing, referred to brannerite standard states, are ΔHmix = y(1 - y)(24.8 - 51.7y) kJ/mole for (1 - y)MnV2O6 - yLiMnVO6 (MnLi) and ΔHmix = 23.4x(1 - x) for (1 - x)MnV2O6 - xMo2O6 (Mnf{cyrillic}). A fit to all the data simultaneously (the two joins above, three ternary points, and one point along Lif{cyrillic}) gives values similar to those above for ΔHmix(MnLi) and ΔHmix(Mnf{cyrillic}) while suggesting a negative heat of mixing along the Lif{cyrillic} binary and negligible ternary excess terms. Parameters for the transformation of Mo2O6 from the MoO3 structure to the hypothetical brannerite structure are estimated to be: ΔH = 10.0 kJ/mole Mo2O6, ΔV° = 7.65 cm3/mole. Both the MnV2O6LiMoVO6 system studied here and the MgV2O6LiMoVO6 system studied previously show positive heats of mixing at MnV2O6- or MgV2O6-rich compositions and negative heats of mixing at LiMoVO6-rich compositions. In each case, a linear correlation of the enthalpy interaction parameter, λH, and the volume interaction parameter, λV, is observed. Both systems show that positive heats of mixing correlate with negative volumes of mixing and negative heats of mixing correlate with positive volumes of mixing, but the MgLi correlation has a steeper slope than that for MnLi. This rather unusual but systematic behavior thus persists in several systems with brannerite structure.

Original languageEnglish (US)
Pages (from-to)45-55
Number of pages11
JournalJournal of Solid State Chemistry
Volume80
Issue number1
DOIs
StatePublished - May 1989
Externally publishedYes

ASJC Scopus subject areas

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

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