Reduction properties of phases in the system La{sub 0.5}Sr{sub 0.5}MO{sub 3} (M=Fe, Co)
- Department of Chemistry, The Open University, Walton Hall, Milton Keynes MK7 6AA (United Kingdom)
- Instituto de Quimica-Fisica 'Rocasolano', Consejo Superior de Investigaciones Cientificas, c/ Serrano 119, ES-28006 Madrid (Spain)
Phases formed by the reduction of compounds of the type La{sub 0.5}Sr{sub 0.5}MO{sub 3} (M=Fe, Co) have been characterized by means of temperature programmed reduction, X-ray powder diffraction, {sup 57}Fe Moessbauer spectroscopy and Fe K-, Co K-, Sr K-, and La L{sub III}-edge X-ray absorption spectroscopy. The results show that treatment of the material of composition La{sub 0.5}Sr{sub 0.5}FeO{sub 3} (which contains 50% Fe{sup 4+} and 50% Fe{sup 3+}) at 650{sup o}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{sup o}C results in the formation of the Fe{sup 3+}-containing phase SrLaFeO{sub 4}, which has a K{sub 2}NiF{sub 4}-type structure, and metallic iron. The material of composition La{sub 0.5}Sr{sub 0.5}CoO{sub 3} is more susceptible to reduction than the compound La{sub 0.5}Sr{sub 0.5}FeO{sub 3} since, after heating at 520 deg. C in the hydrogen/nitrogen mixture, all the Co{sup 4+} and Co{sup 3+} are reduced to metallic cobalt with the concomitant formation of strontium- and lanthanum-oxides.
- OSTI ID:
- 20725860
- Journal Information:
- Journal of Solid State Chemistry, Journal Name: Journal of Solid State Chemistry Journal Issue: 4 Vol. 178; ISSN 0022-4596; ISSN JSSCBI
- Country of Publication:
- United States
- Language:
- English
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