Local environment of ferric iron in a silicate glass

Correlations between atoms in a silicate

Correlations between atoms in a silicate glass. The two Fe-O contributions (red and blue) are also observable in EPSR simulations, with typical distinct environments for Fe3+O4 tetrahedra.
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The presence of iron in glassy materials, either as a ubiquitous impurity or as an intentional additive, affects important properties such as melt rheology, and optical and thermodynamic properties.

Fe3+ is the most abundant valence state of iron in technological glasses, for example controlling UV-transmission in ‘solarcontrol’ soda-lime glasses for housing and automobiles.The determination of the local structure around Fe3+ in glasses is limited by disorder effects and by the permanent coexistence with Fe2+. Neutron diffraction with iron isotopic substitution was used to determine the detailed iron environment in a Na2O-Fe2O3-2SiO2 glass. High real-space resolution neutron diffraction data obtained on Sandals and Empirical Potential Structure Refinement (EPSR) simulations have been combined to quantify the extent of two different iron coordination environments. Tetrahedral Fe3+ constitutes 76% of the total Fe sites and a second contribution corresponds to 5-coordinated Fe3+ and Fe2+. These results are important for understanding the structural role and distribution of iron within the glass structure and provide a rationale for modelling redox properties in silicate melts.

C Weigel, L Cormier, L Galoisy, G Calas (Universites Paris 6 et 7,France), B Beuneu (Laboratoire Léon Brillouin, France), DT Bowron (ISIS)

Research date: December 2007

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