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| Naji, M. |
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| Motta, Antonella |
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| Aletan, Dirar |
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| Mohamed, Tarek |
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| Ertürk, Emre |
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| Taccardi, Nicola |
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| Kononenko, Denys |
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| Petrov, R. H. | Madrid |
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| Alshaaer, Mazen | Brussels |
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| Bih, L. |
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| Casati, R. |
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| Muller, Hermance |
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| Kočí, Jan | Prague |
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| Šuljagić, Marija |
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| Kalteremidou, Kalliopi-Artemi | Brussels |
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| Azam, Siraj |
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| Ospanova, Alyiya |
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| Blanpain, Bart |
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| Ali, M. A. |
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| Popa, V. |
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| Rančić, M. |
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| Ollier, Nadège |
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| Azevedo, Nuno Monteiro |
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| Landes, Michael |
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| Rignanese, Gian-Marco |
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Oneill, Hugh St C.
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Topics
Publications (5/5 displayed)
- 2021Coordination change of Ge4+ and Ga3+ in silicate melt with pressurecitations
- 2021The coordination of Cr2+ in silicate glasses and implications for mineral-melt fractionation of Cr isotopescitations
- 2006The effects of small amounts of H2O, CO2 and Na2O on the partial melting of spinel Lherzolite in the system CaO-MgO-Al2O3-SiO2 ± H2O ± CO2 ± Na2O at 1·1GPacitations
- 2004A XANES determination of the oxidation state of chromium in silicate glassescitations
- 2003XANES calibrations for the oxidation state of iron in a silicate glasscitations
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article
A XANES determination of the oxidation state of chromium in silicate glasses
Abstract
<p>Cr K-edge X-ray absorption near-edge structure (XANES) spectra were recorded for silicate glasses of various compositions in the system CaO + MgO + Al<sub>2</sub>O<sub>3</sub> + SiO<sub>2</sub> ± TiO<sub>2</sub>, quenched from melts equilibrated as a function of oxygen fugacity (f<sub>o2</sub>) at 1400 °C. The spectra vary systematically with f<sub>o2</sub> (logf<sub>o2</sub> ∼0 to -16) indicating changes in the Cr oxidation state. The intensity of a shoulder on the absorption edge (attributed to the 1s → 4s transition) was quantified using the corresponding peak in the XANES derivative spectrum and used to determine Cr<sup>2+</sup>/ΣCr. The resulting Cr<sup>2+</sup>/ΣCr values are in agreement with the theoretical dependence on logf<sub>o2</sub> suggesting that the 1s → 4s feature is diagnostic of Cr<sup>2+</sup> in a silicate glass and σ(Cr<sup>2+</sup>/ΣCr) = ± 0.015. The Cr<sup>2+</sup>/ΣCr ratio for a given logf<sub>o2</sub> changes with the glass composition which may reflect the ability of the melt to accommodate the Jahn-Teller distorted coordination geometry which stabilizes Cr<sup>2+</sup>·Cr<sup>2+</sup>/ΣCr varies between ∼ 0.3 and 0.8 over the logf<sub>o2</sub> range bounded by the Ni/NiO and Fe/FeO f<sub>o2</sub> buffers, suggesting that Cr<sup>2+</sup> may be important in natural melts even though this oxidation state has never been identified in a terrestrial material. The development of a methodology for determining Cr<sup>2+</sup>/ΣCr from XANES spectra of quenched glasses is an essential precursor to in situ experiments on Fe-bearing silicate melts at high temperature.</p>