Surface oxygen exchange of La0.3Sr0.7CoO3-d


Doorn, Rene H.E. van and Fullarton, Ian C. and Souza, Roger A. de and Kilner, John A. and Bouwmeester, Henny J.M. and Burggraaf, Anthonie J. (1997) Surface oxygen exchange of La0.3Sr0.7CoO3-d. Solid State Ionics, 96 (1-2). pp. 1-7. ISSN 0167-2738

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Abstract:The surface oxygen exchange of La0.3Sr0.7CoO3 − δ has been studied by 18O/16O exchange followed by dynamic SIMS analysis in the temperature region 700–;900 °C at a pO2 of 2.1 × 104 Pa. The activation energy for the surface exchange rate (k) is 28 ± 5 kJ mol−1 and for the oxygen tracer diffusion coefficient (D*) 56 ± 4 kJ mol−1. The absolute values for both k and D* are among the highest known in the literature. The characteristic thickness at a pO2 of 2.1 × 104 Pa is calculated to lie in the range 0.70 to 1.3 mm and is a function of temperature. The latter reflects the different activation energies for k and D*. The surface oxygen exchange coefficient is proportional to PO2n with N = 0.41 ± 0.02 at 800 °C, which has been explained by a rate determining step involving an adsorbed oxygen species and an oxygen vacancy. No oxygen pressure dependence for the tracer diffusion coefficient was observed at this temperature.
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Copyright:© 1997 Elsevier Science
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