Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
7902331 | Journal of Non-Crystalline Solids | 2014 | 10 Pages |
Abstract
Iron K-edge EXAFS and XANES have been used to study the local structural environment of dilute quantities (0.2 mol% Fe2O3) of Fe3 + in seven representative SiO2-R2O-R'O glasses where R = (Li, Na, K), R' = (Mg, Ca, Sr, Ba). Sample preparation was carried out by adding excess CeO2 as an oxidising agent and it was confirmed by optical absorption spectroscopy that iron was fully oxidised to Fe3 +. This methodology has made possible, for the first time, an unambiguous EXAFS study of the coordination and local structural environment of dilute levels of Fe3 + in alkali-alkaline earth-silica glasses without the complications presented by the presence of Fe in multiple oxidation states. Coordination of Fe3 + in these glasses is strongly affected by the nature of the alkali and alkaline earth cations, with Fe3 +-O CN increasing from 4.0 ± 0.4 to 6.2 ± 0.9 with decreasing alkali/alkaline earth ionic radius ratio (IRR). Respective FeO bond lengths of 1.87 ± 0.01 Ã
to 1.92 ± 0.01 Ã
were also obtained. Dilute Fe3Â + in the studied glasses displays selective behaviour, as demonstrated by the opposing effects of alkali and alkaline earth ions on measured Fe3Â + CN and Fe3Â +O bond length.
Related Topics
Physical Sciences and Engineering
Materials Science
Ceramics and Composites
Authors
P.A. Bingham, O.M. Hannant, N. Reeves-McLaren, M.C. Stennett, R.J. Hand,