Determination of the oxygen permeation flux through La0.75Ca0.25CrO3-deltaby an electrochemical method

The oxygen permeation flux measured as the oxide ion current density (J(o2- )) through La0.75Ca0.25CrO3-delta was determined at steady state by using a n electrochemical method in the p(o2) range from 10(5) to 10(-11) Pa at T = 1273 K. The oxygen vacancy diffusion coefficient (D-v) is estimated to be 1.5 x 10(-9) m(2) s(-1) in the p(o2) region from 1 to 10(-5) Pa. When p(o2) is lower than 10(-5) Pa, J(o2-) seems to depend on a surface reaction as t he rate-determining step. The contribution of grain-boundary diffusion on p ermeation was considered in the oxidizing atmosphere. The oxygen permeation current density through a 1 mm thick plate is estimated as 0.03 A cm(-2) i n the solid oxide fuel cell operation. (C) 1999 The Electrochemical Society . S0013-4651(98)07-071-2. All rights reserved.