Chemical diffusion and oxygen surface transfer of $La_1-xSr_xCoO_3-delta$ studied with electrical conductivity relaxation


Haar, L.M. van der and Otter, M.W. den and Morskate, M. and Bouwmeester, H.J.M. and Verweij, H. (2002) Chemical diffusion and oxygen surface transfer of $La_1-xSr_xCoO_3-delta$ studied with electrical conductivity relaxation. Journal of the Electrochemical Society, 149 (3). J41-J46. ISSN 0013-4651

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Abstract:The chemical diffusion coefficient and oxygen-transfer coefficients of selected compositions in the series $La_1-xSr_xCoO_3-delta$ were studied using the conductivity relaxation technique. Measurements were performed in the temperature range 600-850°C and oxygen partial pressure $10-4$ to 1 bar. Chemical diffusivity and oxygen surface transfer in the $La_1-xSr_xCoO_3-delta$ perovskites appear to be highly correlated. The general trend displayed is that both parameters decrease with decreasing pO2 below about $10-2$ bar at all temperatures. This is attributed to ordering of induced vacancies at low oxygen partial pressures. The observation that the correlation between both parameters extends even to the lowest $pO_2$ values in this study suggests a key role of the concentration of mobile oxygen vacancies, rather than of the extent of oxygen nonstoichiometry, in determining the rates of both processes. The characteristic thickness $L_c$, which equals the ratio of the chemical diffusion coefficient to the surface transfer coefficient, shows only a weak dependence on oxygen partial pressure and temperature. For different compositions $La_1-xSr_xCoO_3-delta$, $L_c$ is found to vary between 50 and 150 µm.
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Copyright:© 2002 The Electrochemical Society
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