Titel
Multicomponent diffusion in ionic crystals: theoretical model and application to combined tracer- and interdiffusion in alkali feldspar
Autor*in
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Abstract
We present a model for multicomponent diffusion in ionic crystals. The model accounts for vacancy-mediated diffusion on a sub-lattice and for diffusion due to binary exchange of different ionic species without involvement of vacancies on the same sub-lattice. The diffusive flux of a specific ionic species depends on the self-diffusion coefficients, on the diffusion coefficients related to the binary exchanges, and on the site fractions of all ionic species. The model delivers explicit expressions for these dependencies, which lead to a set of coupled non-linear diffusion equations. We applied the model to diffusion of 23Na, 39K, and 41K in alkali feldspar. To this end, gem-quality crystals of alkali feldspar were used together with 41K doped KCl salt as diffusion couples, which were annealed at temperatures between 800∘ and 950∘C. Concentration-distance data for 23Na, 39K, and 41K were obtained by Time of Flight Secondary Ion Mass Spectrometry. Over the entire investigated temperature range the Na self-diffusion coefficient is by a factor of ≥500 higher than the K self-diffusion coefficient. Diffusion mediated by binary 39K–41K exchange is required for obtaining satisfactory fits of the model curves to the experimental data, and the respective kinetic coefficient is well constrained.
Stichwort
Multicomponent diffusionIonic crystalsTheoretical modelApplication to alkali diffusion in alkali feldspar
Objekt-Typ
Sprache
Englisch [eng]
Persistent identifier
phaidra.univie.ac.at/o:1218478
Erschienen in
Titel
Physics and Chemistry of Minerals
Band
47
Ausgabe
8
ISSN
0342-1791
Erscheinungsdatum
2020
Publication
Springer Science and Business Media LLC
Fördergeber
Austrian Science Fund (FWF) — P28238-N29
Erscheinungsdatum
2020
Zugänglichkeit
Rechte
Rechteangabe
© The Author(s) 2020
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