Reduction properties of phases in the system La0.5Sr0.5MO3 (M=Fe, Co) |
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Authors: | Frank J Berry Xiaolin Ren |
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Institution: | a Department of Chemistry, The Open University, Walton Hall, Milton Keynes MK7 6AA, UK b Instituto de Química-Física “Rocasolano”, Consejo Superior de Investigaciones Científicas, c/ Serrano 119, ES-28006 Madrid, Spain |
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Abstract: | Phases formed by the reduction of compounds of the type La0.5Sr0.5MO3 (M=Fe, Co) have been characterized by means of temperature programmed reduction, X-ray powder diffraction, 57Fe Mössbauer spectroscopy and Fe K-, Co K-, Sr K-, and La LIII-edge X-ray absorption spectroscopy. The results show that treatment of the material of composition La0.5Sr0.5FeO3 (which contains 50% Fe4+ and 50% Fe3+) at 650 °C in a flowing 90% hydrogen/10% nitrogen atmosphere results in the formation of an oxygen-deficient perovskite-related phase containing only trivalent iron. Further heating in the gaseous reducing environment at 1150 °C results in the formation of the Fe3+-containing phase SrLaFeO4, which has a K2NiF4-type structure, and metallic iron. The material of composition La0.5Sr0.5CoO3 is more susceptible to reduction than the compound La0.5Sr0.5FeO3 since, after heating at 520 °C in the hydrogen/nitrogen mixture, all the Co4+ and Co3+ are reduced to metallic cobalt with the concomitant formation of strontium- and lanthanum-oxides. |
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Keywords: | Perovskite-related oxides Reduction phases Mö ssbauer XAS |
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