THERMODYNAMICS OF MN3O4-CO3O4,FE3O4-MN3O4, AND FE3O4-CO3O4 SPINELS BY PHASE-DIAGRAM ANALYSIS

High temperature phase equilibrium data are compiled from the literature for the Mn-Co-O, Fe-Mn-O, and Fe-Co-O systems. These data are then analyzed with a view to examining the thermodynamics of the spinel phases. It is shown that the results are consistent with a simple ″ideal″ model of cation distribution in the spinel phases. The representation and subsequent analysis of the phase equilibria are greatly facilitated through the use of isothermal log rho omicron //2-composition phase diagrams and through the use of a computer program to calculate these diagrams.