Abstract
Lanthanum manganite, an air electrode material of SOFCs, is well known for its complicated nonstoichiometry, which depends upon oxygen partial pressure, P O2 . This nomstoichiometry has a relationship with electrode reactivity as it affects oxygen activation step and/or oxide ion sink, etc. In addition, the cell volume of lanthanum manganite has a dependence on the nostoichiometty This paper aims to elucidate the effect of the cell volume on cathode reactivity, and to determine the rate equation for the reaction at the air electrode of the type O 2 (g)/porous La 1-x A k MnO 3+δ (A = Sr, Ca)/YSZ. The steady-state polarization and the complex-impedance were measured for the porous La 1-x A x MnO 3+δ /YSZ electrode with P O2 in the range of 10-10 5 Pa and temperature between 873-1273 K. The results suggest that oxygen nonstoichiometry and cell volume affect cathode reactivity. The steady-state current was found to obey the rate equation, which had a peculiar rate constant depending on composition.
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