Thermodynamics of phase inter-relations in subsolidus of MgO-Al2O3-SiO2 system

Results of thermodynamic calculations determining temperature dependences of reactions between stoichiometric compounds of Mgo-Al2O3-SiO2 system have been presented. Particularities in thermodynamic conjugation of solid phase reactions have been analyzed. Thermodynamic instability of sapphirine and cordierite with stoichiometric compositions has been found. General scheme of interactions between non-stoichiometric compounds has been ground; Opportunity for forming the sapphirine and cordierite solid solutions has been taken into account. It has been shown that structural variations in crystal lattices of sapphirine and cordierite should be considered from view-point of varying the solid solutions.