Abstract: With the purpose of giving theoretical insight for preparation of single phase of Fe₃O₄ particles from Fe₃O₄ or coarse Fe₃O₄ using mechanochemical method, the impact of stored energy on the thermodynamics of the mechanochemical reaction of iron oxides was discussed. Results showed that the mechanochemical decomposition temperature of iron oxides in air decreases linearly with the increase of stored energy, and subsequently the phases in the reaction system changes within the temperature ranges in thermodynamically stable. On these ground, the thermodynamically stable region for Fe₃O₄ in the mechanochemical reaction system with Fe₃O₄ (or Fe₃O₄) as the starting reactant were drawn in the stored energy-temperature coordinate system, and thereby the thermodynamic condition for preparation of single phase of Fe₃O₄ from either Fe₃O₄ or Fe₃O₄ were clarified.

Key words: Fe₃O₄, Fe₂O₃, Mechanochemical method, Stored energy, Thermodynamically stable region