Electron spin resonance in natural kaolinites containing Fe3+ and other transition metal ions
| Autor: | P. J. Malden, R. E. Meads |
|---|---|
| Rok vydání: | 1975 |
| Předmět: |
Chemistry
Stacking Resonance 020101 civil engineering 02 engineering and technology 010502 geochemistry & geophysics 01 natural sciences Spectral line 0201 civil engineering law.invention Ion Crystal Crystallography Nuclear magnetic resonance Octahedron Geochemistry and Petrology law Electron paramagnetic resonance Hyperfine structure 0105 earth and related environmental sciences |
| Zdroj: | Clay Minerals. 10:313-345 |
| ISSN: | 1471-8030 0009-8558 |
| Popis: | A number of natural kaolinites from a variety of world sources have been investigated using electron spin resonance at both X-band and Q-band. The results show systematic differences some of which are related to the crystallinity of the material, some to the presence of transition metal ions other than Fe3+ and hole-trapping defects.The results provide evidence for at least three sites for substitution of Fe3+ having large crystal fields : (i) a site with near maximum rhombic character having crystal field parameters D > 1·2, λ = ⅓ the occurrence of which is correlated with lack of crystalline perfection due to stacking defects or to the proximity of surfaces, (ii) a site with less rhombic character with λ = 0·234, D = 0·585 as likely parameters, and (iii) a site with parameters near the values λ = 0·207, D = 0·322.Mössbauer and ESR evidence suggests that the principal sites of Fe3+ substitution are octahedral. The presence of Fe3+ in adjacent cation sites leads to a very broad resonance centred near geff = 2. Other resonances in the spectra are attributed to the effect of trapped holes, some at least of which are situated at oxygen sites adjacent to Al3+ ions substituting in sites normally occupied by Si4+.Hyperfine effects due to the presence of the transition ions Mn2+ and (VO)2+ are also observed. |
| Databáze: | OpenAIRE |
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