Details
Original language | English |
---|---|
Pages (from-to) | 44-56 |
Number of pages | 13 |
Journal | American mineralogist |
Volume | 92 |
Issue number | 1 |
Publication status | Published - 1 Jan 2007 |
Abstract
In-situ X-ray absorption spectroscopy at the Fe K-edge was used to characterize the local structural environment of Fe2+ and Fe3+ in silicate melts at high temperature (up to 1050 °C) in comparison to their quenched glassy analog at room temperature. Measurements were performed on binary alkali-silicate compositions and on haplogranitic compositions, which were doped with about 5 wt% Fe2O3. Changes in the structural environment of Fe were evaluated by analyzing both the pre-edge feature and the first maximum of the EXAFS of the spectra. In most cases, the spectra collected at high temperature differed from those of the quenched samples. At reducing conditions, the melts showed slightly higher amounts of low-coordinated Fe2+ than their glassy counterparts. This finding is consistent with results of earlier studies (e.g., Jackson et al. 1993), but the observed change in speciation is smaller than reported by these authors. At oxidizing conditions, glasses and melts displayed a more heterogeneous behavior. The spectra of alkali-silicate compositions indicate higher amounts of low-coordinated Fe3+ in the melt, whereas no significant difference between melt and glass was observed for Fe3+ in haplogranitic compositions, even if the latter are peralkaline. The amount of non-bridging O atoms in the glass/ melt system appears to play an important role particularly for Fe3+. However, more complex relationships between Fe and other structural components, especially Al, are possible.
Keywords
- Fe in silicate melts, Fe K-edge, Glass properties, High-temperature studies, Melt properties, XAS (XAFS, XANES)
ASJC Scopus subject areas
- Earth and Planetary Sciences(all)
- Geophysics
- Earth and Planetary Sciences(all)
- Geochemistry and Petrology
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In: American mineralogist, Vol. 92, No. 1, 01.01.2007, p. 44-56.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Speciation of Fe in silicate glasses and melts by in-situ XANES spectroscopy
AU - Wilke, Max
AU - Farges, François
AU - Partzsch, Georg M.
AU - Schmidt, Christian
AU - Behrens, Harald
PY - 2007/1/1
Y1 - 2007/1/1
N2 - In-situ X-ray absorption spectroscopy at the Fe K-edge was used to characterize the local structural environment of Fe2+ and Fe3+ in silicate melts at high temperature (up to 1050 °C) in comparison to their quenched glassy analog at room temperature. Measurements were performed on binary alkali-silicate compositions and on haplogranitic compositions, which were doped with about 5 wt% Fe2O3. Changes in the structural environment of Fe were evaluated by analyzing both the pre-edge feature and the first maximum of the EXAFS of the spectra. In most cases, the spectra collected at high temperature differed from those of the quenched samples. At reducing conditions, the melts showed slightly higher amounts of low-coordinated Fe2+ than their glassy counterparts. This finding is consistent with results of earlier studies (e.g., Jackson et al. 1993), but the observed change in speciation is smaller than reported by these authors. At oxidizing conditions, glasses and melts displayed a more heterogeneous behavior. The spectra of alkali-silicate compositions indicate higher amounts of low-coordinated Fe3+ in the melt, whereas no significant difference between melt and glass was observed for Fe3+ in haplogranitic compositions, even if the latter are peralkaline. The amount of non-bridging O atoms in the glass/ melt system appears to play an important role particularly for Fe3+. However, more complex relationships between Fe and other structural components, especially Al, are possible.
AB - In-situ X-ray absorption spectroscopy at the Fe K-edge was used to characterize the local structural environment of Fe2+ and Fe3+ in silicate melts at high temperature (up to 1050 °C) in comparison to their quenched glassy analog at room temperature. Measurements were performed on binary alkali-silicate compositions and on haplogranitic compositions, which were doped with about 5 wt% Fe2O3. Changes in the structural environment of Fe were evaluated by analyzing both the pre-edge feature and the first maximum of the EXAFS of the spectra. In most cases, the spectra collected at high temperature differed from those of the quenched samples. At reducing conditions, the melts showed slightly higher amounts of low-coordinated Fe2+ than their glassy counterparts. This finding is consistent with results of earlier studies (e.g., Jackson et al. 1993), but the observed change in speciation is smaller than reported by these authors. At oxidizing conditions, glasses and melts displayed a more heterogeneous behavior. The spectra of alkali-silicate compositions indicate higher amounts of low-coordinated Fe3+ in the melt, whereas no significant difference between melt and glass was observed for Fe3+ in haplogranitic compositions, even if the latter are peralkaline. The amount of non-bridging O atoms in the glass/ melt system appears to play an important role particularly for Fe3+. However, more complex relationships between Fe and other structural components, especially Al, are possible.
KW - Fe in silicate melts
KW - Fe K-edge
KW - Glass properties
KW - High-temperature studies
KW - Melt properties
KW - XAS (XAFS, XANES)
UR - http://www.scopus.com/inward/record.url?scp=33846406077&partnerID=8YFLogxK
U2 - 10.2138/am.2007.1976
DO - 10.2138/am.2007.1976
M3 - Article
AN - SCOPUS:33846406077
VL - 92
SP - 44
EP - 56
JO - American mineralogist
JF - American mineralogist
SN - 0003-004X
IS - 1
ER -