Computer-assisted analysis and calculation of phase diagrams of the FeCrO, FeNiO and CrNiO systems

Abstract

Available thermodynamic and phase equilibrium data for the FeCrO, FeNiO and CrNiO systems are assessed and equations for the free energies of the phases as functions of composition and temperature are derived. With these mathematical expressions and with a computer program written for the purpose, phase diagram sections at constant temperature, or at constant log p O 2 , or at constant P co P co 2 or p H 2 P H 2O ratios can be calculated at all compositions and over a wide range of temperature and oxygen potential. The representation and analysis of the phase equilibria are greatly facilitated through the use of isothermal log P O 2 -composition phase diagrams which are discussed in some detail. Structural models for the spinel phases are examined.