Conductivity, transport number measurements and hydration thermodynamics of BaCe0.2Zr0.7Y(0.1-ξ)NiξO(3-δ)

BaCe0.2Zr0.7Y(0.1 - xi)Ni xi O(3 - delta) compounds with xi = 0.01 and 0.02 have been synthesized by solid state reaction at 1400 degrees C and sintered at 1450 degrees C. TEM analyses were performed and showed a segregation of nickel at the grain boundaries for xi = 0.02. This apparent solubility limit of Ni in the B-site of the perovskite is in agreement with similar data obtained earlier for the two compositions. The first aim of this work was to evaluate the conductivity of BaCe0.2Zr0.7Y(0.1 - xi)Ni xi O(3 - delta) at temperature between 500 and 900 degrees C, using impedance spectroscopy at different oxygen partial pressures and water vapor pressures, as well as the emf technique. The compounds exhibit p-type conduction in oxidizing atmosphere, and ionic conduction elsewhere. The oxide ion contribution of the conductivity is negligible only for temperatures below 600 degrees C. The determination of hydration enthalpies, our second goal, was achieved by modelling of the conductivity data and by thermogravimetric measurements (TG-DSC). (c) 2010 Elsevier B.V. All rights reserved.