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


Doorn van, Rene H.E. and Fullarton, Ian C. and Souza de, Roger A. 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

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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