Sodium Coordination Environments in Silica Films |
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Authors: | Jacques Jupille Anne-Marie Flank Pierre Lagarde |
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Affiliation: | Laboratoire CNRS/Saint-Gobain "Surface du Verre et Interfaces," 93303 Aubervilliers, France;LURE, Bat. 209D, UniversitéParis-Sud, 91898 Orsay Cedex, France |
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Abstract: | The local structure centered on sodium after diffusion in silica (Na-SiO2 samples) has been determined by means of extended X-ray absorption fine structure (EXAFS) studies. The Na-SiO2 samples are of particular interest because (i) their sodium content can be varied over a wide range of concentration and (ii) their local structure is representative of that of soda–silica glass. EXAFS analyses reveal the existence of a well-defined local structure involving oxygen, sodium, and silicon neighbors. The Na-O, Na-Na, and Na-Si bonds lengths, which amount to 0.23, 0.30, and 0.38 nm, respectively, do not depend on sodium concentration. This environment closely resembles that found in soda–silica glass. Moreover, it is compatible with the "target site" and "the site memory effect" suggested by recent theories of the ionic conductivity in oxide glasses. |
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Keywords: | sodium/sodium compounds silica films |
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