Thermodynamics of CoO-MgO solid solutions

Lan Wang, Alexandra Navrotsky, Rebecca Stevens, Brian F. Woodfield, Juliana Boerio-Goates

Research output: Contribution to journalArticlepeer-review

15 Scopus citations

Abstract

Enthalpies of mixing in CoxMg1-xO solid solutions at T=298 K have been determined using high temperature drop solution calorimetry in molten sodium molybdate (3Na2O·4MoO3) solvent at T=973 K. Slightly positive enthalpies of mixing were observed, which conform to a regular solution model with interaction parameter W=(5.1±0.3) kJ·mol-1, which is similar to the interaction parameter calculated from previously measured activity-composition relations. Standard molar entropies Sm0 at T=298 K calculated from subambient Cp data for CoO, MgO are (52.8±0.1) J·K -1·mol-1 and (28.1±0.1) J·K -1·mol-1, respectively. Integration of the C p,m/T of the Co0.50Mg0.50O mixture yields an entropy of (40.3±0.1) J·K-1·mol-1. This value does not include configurational entropy from the Co/Mg site disorder. The excess entropy of Co0.50Mg0.50O is zero within experimental error. Heat capacities were also measured between T=298 K and T=973 K. The enthalpies of mixing do not depend on temperature in this range.

Original languageEnglish (US)
Pages (from-to)1151-1159
Number of pages9
JournalJournal of Chemical Thermodynamics
Volume35
Issue number7
DOIs
StatePublished - Jul 2003
Externally publishedYes

Keywords

  • Calorimetry
  • CoMgO solid solution
  • Enthalpy
  • Interaction parameter
  • Standard entropy

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics
  • Materials Science(all)
  • Physical and Theoretical Chemistry

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