Abstract
The phase composition of La1 – x Ca x FeO3 – 0.5x perovskites synthesized from preactivated oxides was studied by powder X-ray diffraction analysis and differential dissolution. The system does not form a continuous series of homogeneous solid solutions. No intermediate samples from this series are monophasic. It was found that the synthesis under nonequilibrium conditions (mechanical activation + calcination at 900°С for 4 h) resulted in nonequilibrium microheterogeneous solid solutions with degrees of calcium substitution for lanthanum of no higher than 0.5. A longer calcination (for 16 h) or an increase in the calcination temperature of solutions up to 1100 °С decreased the calcium content of the samples down to x ∼ 0.2 because of the formation of a brownmillerite phase. The catalytic activity of the test samples in the oxidation of CO changed nonmonotonically with x, and it was maximum at x = 0.5–0.6, which correlates with the maximum density of interphase boundaries in these samples.
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Isupova, L.A., Tsybulya, S.V., Kryukova, G.N. et al. Physicochemical and Catalytic Properties of La1 – xCaxFeO3 – 0.5x Perovskites Prepared Using Mechanochemical Activation. Kinetics and Catalysis 43, 129–138 (2002). https://doi.org/10.1023/A:1014269700953
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DOI: https://doi.org/10.1023/A:1014269700953