Diffusivity of anion vacancies in WO3 passive films |
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Authors: | Gerardo Vá zquez |
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Affiliation: | Universidad Autónoma Metropolitana-Iztapalapa, Depto. de Química, Área de Electroquímica, Apdo. 55-534, C.P. 09340, México D.F., Mexico |
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Abstract: | The WO3 films were grown in 0.1 M HClO4 aqueous solution, at different formation potentials (Ef) in the range of 2.0-7.0 V versus sce, on W electrode. The anion diffusion coefficient (DO![radical dot](http://cdn.els-cdn.com/sd/entities/rad) ) of WO3 films was calculated from EIS spectra, following the surface charge approach (at high-field limit approximation), the Point Defect Model and the Mott-Shottky analysis. Among the parameters necessary to evaluate DO![radical dot](http://cdn.els-cdn.com/sd/entities/rad) , the half-jump distance (a) is very relevant, given that a small variation in a has a great impact in the calculation of DO![radical dot](http://cdn.els-cdn.com/sd/entities/rad) . In this work, it is proposed the half-jump distance (a) should be evaluated from spectroscopic data (available in the literature). The value of a (∼1.9 Å) is taken from lattice constants of a-WO3 (amorphous-WO3), with different values of N (coordination number), and the lattice constants of m-WO3 (monoclinic-WO3). The calculated value of DO![radical dot](http://cdn.els-cdn.com/sd/entities/rad) was ∼3 × 10−17 cm2/s. |
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Keywords: | Diffusivity Passive films EIS W oxides Mott-Schottky |
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