The oxidation kinetics of a Fe-bearing supercooled liquid of the system SiO2-CaO-MgO-Na2O-FeO has been determined near the glass transition range by X-ray absorption near edge structure (XANES) and Raman spectroscopies. Both techniques yield room-temperature iron redox ratios in accord with wet chemical, Mossbauer and electron microprobe analyses. Similar oxidation kinetics have also been observed with both methods. At constant temperature, the kinetics obey an exponential law with a characteristic time that follows an Arrhenian temperature dependence. As redox changes are too fast to be accounted for in terms of diffusion of either ionic or molecular oxygen, these results lend further support to the idea that the rate-limiting factor for oxidation near the glass transition is diffusion of network-modifying cations along with a flux of electron holes. (c) 2006 Elsevier B.V. All rights reserved.
CNRS, IPGP, F-75252 Paris 05, France; CEA VALRHO Marcoule, SCDV, LEBV, F-30207 Bagnols Sur Ceze, France; Univ Paris 06, CNRS, IMPMC, UMR 7590, F-75252 Paris 05, France; Univ Paris 07, CNRS, IMPMC, UMR 7590, F-75252 Paris 05, France; CNRS, Lab Cristallog, UPR 5031, F-38043 Grenoble, FranceArticleEnglish