PHASE TRANSFORMATIONS DURING CRYSTALLIZATION OF Sr2FeMoO6–δ FROM SIMPLE OXIDES

Abstract

The sequence of phase transformations during Sr₂FeMoO_6–δ crystallization by the solid phase method was studied for powders synthesized from the stoichiometric mixture of SrCO₃ Fe₂O₃, MoO₃ oxides. It is found that the synthesis of a strontium ferromolybdate solid solution proceeds through a series of parallel chemical reactions. It is revealed that at the beginning stage of interaction, the initially formed Sr₂FeMoO_6–δ powder is enriched with iron. During the annealing process, the composition of strontium ferromolybdate changes and the molybdenum content increases upon further heating. It is shown that in the process of crystallization of double perovskite in the temperature range T = (300–1420) K, there is the following sequence of phase transformations Fe₂O₃, MoO₃, SrCO₃} (300 К) → {SrMoO₄, Fe₂O₃, SrCO₃} (770 К) → {SrMoO₄, SrFeO_3–х (traces), Sr₂FeMoO_6–δ (traces)} (970 K) → {SrMoO₄, Sr₂FeMoO_6–δ } (1170 К) → { Sr₂FeMoO_6–δ } (1420 К)..