MEASUREMENT AND THERMODYNAMIC EVALUATION OF PHASE-EQUILIBRIA IN THE MG-TI-O SYSTEM

Equilibrium phase relations among the periclase (MgO), spinel (Mg2TiO4 -MgTi2O4 solution) geikielith (MgTiO3-Ti2O3 solution), karrooite (MgTi 2O5-Ti3O5 solution) and Magneli phases at 1500 degrees C in the MgO-Ti O2-Ti2O3 system are investigated by the quench method combined with mi croprobe analysis and X-ray diffraction. These data are combined with other thermodynamic data to obtain a set of optimized thermodynamic eq uations for the phases. Models for the spinel, geikielith and karrooit e solutions are developed. The good agreement between the calculated a nd measured tie-lines indicates the essential correctness of the therm odynamic models and the phase diagram. A similar modeling of literatur e data for the Mn-Ti-O system is carried out. The parameters are combi ned with those obtained in an earlier optimization of the Fe-Ti-O syst em in order to develop a thermodynamic database for oxide compounds an d solutions in the Fe-Mg-Mn-Ti-O system.