Oxide-ion conductivity of (Ba1-xLax)(2)In2O5+x system based on brownmillerite structure

(Ba1-xLax)(2)In2O5+x, whose end member is Ba2In2O5, is an oxygen-deficient perovskite oxide showing high oxide-ion conductivity. In order to clarify t he reason why the high oxide ion conductivity appeared in this system, the electrical conductivity was measured as a function of temperature and La co ntent. With an increasing La content, the discontinuous jump of ion conduct ivity in the Arrhenius plot, which is related to the disordering of the oxy gen vacancies, disappeared for the sample with x=0.2. Above x = 0.12, the i on conductivity linearly increased with La content, while the activation en ergy remained constant with respect to the La content. Moreover, the conduc tivity for x = 0.6 was 0.042 (S/cm) at 1073 K, which exceeded that of 8 mol % yttria-stabilized zirconia. The higher oxide-ion conductivity of this sys tem could be dominated by the amount of mobile oxygen ions. (C) 2001 Elsevi er Science B.V. All rights reserved.