High-temperature Mössbauer study of Fe-substituted mullite

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doi: 10.2138/am.2005.1689
Authors:Mack, Daniel E.; Becker, Klaus D.; Schneider, Hartmut
Author Affiliations:Primary:
Technische Universität Braunschweig, Institut für Physikalische und Theoretische Chemie, Braunschweig, Federal Republic of Germany
Deutsches Luft- und Raumfahrtzentrum, Federal Republic of Germany
Volume Title:American Mineralogist
Source:American Mineralogist, 90(7), p.1078-1083. Publisher: Mineralogical Society of America, Washington, DC, United States. ISSN: 0003-004X
Publication Date:2005
Note:In English. 22 refs.; illus., incl. 1 table
Summary:Mossbauer spectra of Fe-substituted 3/2-mullite (10.3 wt% Fe2O3) have been measured from room temperature up to 1200°C under nitrogen atmosphere. A Voigt-type fit to the spectral line shape is proposed that is based on the assumption of three non-equivalent Fe3+ environments A, B, and C in the mullite structure. The Fe3+ subspectra display quadrupole splittings of about 1.1 (A), 0.7 (B), and 1.3 mm/s (C) where the isomer shifts at room temperature are about 0.3 mm/s for subspectra A and B and about 0.1 mm/s for site C. Subspectra A and B are attributed to two different Fe3+ octahedral sites in mullite coordination, experiencing slightly different quadrupolar interactions; the third site is assigned to ions in tetrahedral coordination. Subspectrum A is assigned to the iron-oxygen octahedra having TO4 tetrahedra as next nearest neighbors, while subspectrum B may correspond to iron-oxygen octahedra having TO4 and T*O4 tetrahedra with associated oxygen vacancies in their vicinity. The quadrupolar splittings of the three subspectra are found to be almost independent of temperature. The temperature dependences of the isomer shifts conform closely to those expected for a harmonic solid at the high-temperature limit. The Mossbauer study gives no support for any temperature-induced redistribution of Fe in mullite.
Sections:Crystal structure; Experimental mineralogy
Mineral Groups:Ortho-and ring silicates
Subjects:Coordination; Crystal chemistry; Crystal structure; Experimental studies; Ferric iron; High temperature; Iron; Isomorphism; Laboratory studies; Metals; Mossbauer spectra; Mullite; Nesosilicates; Orthosilicates; Silicates; Spectra; Temperature
Abstract Numbers:05M/2786
Record ID:2005049950
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Abstract, copyright, Mineralogical Society of America, Reference includes data from GeoScienceWorld, Alexandria, VA, United States
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