Abstract
Mössbauer spectra of 57Fe in 2 schorlomite garnets reveal 5 distinct quadrupole-split doublets: dodecahedral Fe2+, octahedral Fe2+ and Fe3+, and tetrahedral Fe2+ and Fe3+. The isomer shifts and nuclear quadrupole splittings of the 5 doublets were studied between 15 and 500 K. The site occupancies for iron were determined. Reference of the chemical analyses to a basis of 12 oxygens and the Mössbauer data show that in the 2 schorlomites titanium is exclusively quadruvalent within the experimental error.
The isomer shift of tetrahedral Fe2+ between 15 and 295 K seems to be rather small. The shift is interpreted in terms of localized chemical bonding. Above 295 K the shift cannot be evaluated because of overlapping peaks. If electronic transfer processes (e.g. “electron hopping”) between cations are present their relaxation times must be longer than ∼10−7 s.
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Amthauer, G., Annersten, H. & Hafner, S.S. The Mössbauer spectrum of 57Fe in titanium-bearing andradites. Phys Chem Minerals 1, 399–413 (1977). https://doi.org/10.1007/BF00308849
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DOI: https://doi.org/10.1007/BF00308849