Charge Transfer Between Ce and Fe During Cooling of an Aluminosilicate Melt: An In Situ XANES Investigation
Résumé
Multivalent elements are often incorporated to silicate glasses to enhance specific properties to the final product. However, these properties strongly depend on the redox state of the multivalent elements. While the redox behavior of glasses containing a single multivalent element is well studied, research on the in situ interaction between multiple multivalent elements is scarce. In this study, in situ XANES spectroscopy was used to investigate the high temperature redox state of both Ce and Fe in an aluminosilicate melt. The results were compared to room temperature measurements. Our findings demonstrate that, at high temperature equilibrium, Ce and Fe act independently. However, upon cooling below 900°C, a charge transfer process occurs between the two elements as described by the reaction Ce4+ + Fe2+ → Ce3+ + Fe4+. The existence of such a charge transfer, observed even in melts doped with very low Ce and Fe amounts, could suggests that both elements are not randomly distributed in the melt. The intensity of the charge transfer process depends on the CeO2/FeO ratio, with the element present in excess showing minimal change in redox state upon cooling. This explains the difference of room temperature redox state between samples.
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