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.
- CoMgO solid solution
- Interaction parameter
- Standard entropy
ASJC Scopus subject areas
- Atomic and Molecular Physics, and Optics
- Materials Science(all)
- Physical and Theoretical Chemistry