A Mössbauer study of thermal decomposition of biotites
| Autor: | C. S. Hogg, R. E. Meads |
|---|---|
| Rok vydání: | 1975 |
| Předmět: |
Thermogravimetric analysis
010504 meteorology & atmospheric sciences Chemistry Thermal decomposition Atmospheric temperature range 010502 geochemistry & geophysics 01 natural sciences Ion Octahedron Geochemistry and Petrology Lattice (order) Mössbauer spectroscopy Physical chemistry Mossbauer spectra 0105 earth and related environmental sciences |
| Zdroj: | Mineralogical Magazine. 40:79-88 |
| ISSN: | 1471-8022 0026-461X |
| Popis: | SummaryThe effect of heat treatment in air at temperatures from 200°C to 1000°C of two Cornish biotites has been studied using the M6ssbauer effect in 57Fe. One of the micas was also studied after heating in vacuo.Progressive changes in the Mössbauer spectra of the materials after heat treatment can be correlated with the following processes: Oxidation of Fe2+ ions in isolated octahedral sites to give Fe3+ in the co-ordination Fe3+(OsOH); oxidation of Fe2+ ions in adjacent a-octahedral (cis OH−) sites to give Fe3+(O6); and oxidation of Fe z+ in adjacent a and b (trans OH−) sites to give either Fe3+(O5OH) or Fe3+(O6) depending on whether a shared hydroxyl group remains intact or otherwise (these processes occur at temperatures below 500°C Also, at higher temperatures, dehydroxylation of Fe3+(O5OH) to give more Fe3+ in the Fe3+(O6) configuration. Finally, in the temperature range 900 to 1000°C structural breakdown yielding α-Fe2O3 as the iron-containing phase.The results and interpretation are in good agreement with thermogravimetric data and with a previous infra-red study. The mechanism of charge diffusion in the lattice during oxidation is discussed in the light of the results. |
| Databáze: | OpenAIRE |
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