Abstract
Chemical composition and vacancy ditribution are studied in cation-deficient Mn Fe spinel oxides of general formula Fe 3− x Mn x O 4+ y prepared by the thermal decomposition of mixed carbonates. An oxygen/metal ratio in the 1.5–1.6 range is found for samples obtained at 400°C in an air atmosphere. In addition, a significant content of Mn(IV) ions can be derived from chemical and XRD data. The Mössbauer data of these samples reveal the effects of small particle size as well as isolating effects of the Fe(III) ions in B sites by A-site cation vacancies. These effects increase with Mn content. For samples prepared at 600°C, the XRD data and Mössbauer data are interpreted in terms of a higher particle size and lower vacancy content than those found at 400°C. At both temperatures, the cation vacancies found in B-sites are ordered in a γ-Fe 2O 3-type superstructure when the Mn content is lower than 0.6.
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