Solid solutions Bi2–xLaxFe4O9 at small x‐values (x=0.05, 0.1) were synthesized by the solid‐state reaction method. Here larger Bi3+ ions were partially substituted by smaller La3+ ions. It is shown that the above solid solutions had an orthorhombic mullite‐type crystal structures. Crystal lattice parameters of solid solutions were very close to the respective parameters for pure Bi2Fe4O9 ferrite. It was determined that the substitution of Bi3+ ions by La3+ ions in Bi2Fe4O9 leads to the increase of specific magnetizations of the samples. All studied samples were antiferromagnets with Neel temperatures TN of 258 K, 246 K, ∼243 K for x=0, 0.05, 0.1 respectively. Hence at the substitution of Bi3+ ions by La3+ ions, TN decreases. It is shown that solid solution Bi1.9La0.1Fe4O9 had good photocatalytic activity for the oxidation of Acid Telon Blue dye in the aqueous solution under visible light irradiation.

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