THERMODYNAMIC MODELING OF THE PHASE DIAGRAM OF THE SYSTEM Cu2O–BaO–Fe2O3

The thermodynamic modeling of the phase diagrams of the double systems Cu2O–BaO, Cu2O–Fe2O3, BaO–Fe2O3, and also the ternary system Cu2O–BaO–Fe2O3 was carried out. Thermodynamic models and their parameters, necessary for the thermodynamic description of the activity of the oxide melt components in these systems, are determined. For the calculation, the approximations of the theories of ideal ionic solutions (for the system Cu2O–Fe2O3) and subregular ionic solutions (for the systems Cu2O–BaO, BaO–Fe2O3, Cu2O–BaO–Fe2O3) were used. Based on the results of the simulation, the coordinates of the points of nonvariant transformations in the systems under study are defined. The obtained results on the thermodynamic modeling of the coordinates of the liquidus lines of the phase diagrams of the binary systems Cu2O–BaO, Cu2O–Fe2O3, BaO–Fe2O3 were compared with disparate small literary data for the systems under study. In the course of the work, the areas of existence of barium ferrites in the ternary oxide system Cu2O–BaO–Fe2O3 were determined for the first time. Also isotherms are constructed on the full projection of the liquidus surface of the phase diagram of the Cu2O–BaO–Fe2O3 system. The modeling method allowed to estimate the enthalpy, temperature and entropy of melting of compounds BaO with copper (I) oxide (BaCu2O2); with iron (III) oxide (Ba3Fe2O6, Ba2Fe2O5, BaFe2O4, BaFe12O19). The data obtained during the work will be necessary for the development of technological conditions for the synthesis of the barium hexaferrite monocrystals, in the crystal lattice of which part of the iron cations is replaced by copper ions.