Distribution of Fe3+ in a synthetic (Ca,Na)2(Mg,Fe3+)Si2O7-melilite: 57Fe Mössbauer and X-ray Rietveld studies

Crystal structure and the 57Fe Mössbauer spectrum of synthetic (Ca1.53Na0.47)(Mg0.52Fe3+0.49)Si1.99O7-melilite have been investigated to confirm the location of Fe3+ at the T1 site, and to evaluate the effect of an incommensurate structure on 57Fe Mössbauer hyperfine parameters. A conventional Rietv...

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Bibliographic Details
Published in:Journal of Mineralogical and Petrological Sciences 2005, Vol.100(6), pp.229-236
Main Authors: AKASAKA, Masahide, NAGASHIMA, Mariko, MAKINO, Kuniaki, OHASHI, Haruo
Format: Article
Language:English
Subjects:
Crystal structure
Ferric iron
Melilite
Mössbauer
Synthetic mineral
X-ray Rietveld
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Summary:Crystal structure and the 57Fe Mössbauer spectrum of synthetic (Ca1.53Na0.47)(Mg0.52Fe3+0.49)Si1.99O7-melilite have been investigated to confirm the location of Fe3+ at the T1 site, and to evaluate the effect of an incommensurate structure on 57Fe Mössbauer hyperfine parameters. A conventional Rietveld refinement with occupancies of Ca(W), Na(W), Mg(T1), Fe3+(T1) and Si(T2) fixed to 0.765, 0.235, 0.515, 0.485 and 2.00, respectively, converged well with an Rwp (R-weighted pattern) of 13.14% and a goodness-of-fit of 1.337, indicating exclusive Fe3+ distribution at the T1 site. However, the Mössbauer spectrum consists of two doublets with an isomer shift of 0.19 mm/s and quadrupole splitting of 0.75 and 1.04 mm/s, which can be attributed to Fe3+ at the T1 site. There are two sorts of T1 site with distinguishable distortion in the synthetic Na-Fe3+-melilite, which might be attributed to the existence of an incommensurate phase at room temperature.
ISSN:1345-6296
1349-3825
DOI:10.2465/jmps.100.229