Y and In-doped BaCeO3-BaZrO3 solid solutions: Chemically stable and easily sinterable proton conducting oxides

BaCeO3 and BaZrO3 based perovskites display good protonic conductivity. However, the former suffers from low chemical stability while the latter exhibits good stability but lower conductivity and sinterability. Hence, a combination or solid solution of these two systems can be a good approach to maintain both conductivity and chemical stability. In this study, Ba(Ce, Zr)O-3 solid solution was doped with yttrium and indium and the effect of various levels of In-doping, BaCe0.4Zr0.3In0.3-xYxO3-delta (x = 0, 0.1, 0.2), on the sinterability, chemical stability and conductivity was studied. The pellets of In-containing samples could be sintered easily at a much lower temperature (1450 degrees C) yielding sintered density >= 94% of the theoretical density. The density was found to increase with increasing In content and a relative sintered density as high as 99% was achieved in the BaCe0.4Zr0.3In0.3-xYxO3-delta composition. The chemical stability against CO2 and water atmospheres also improved with In addition. The perovskite phase in the composition without In (BaCe0.4Zr0.3In0.3-xYxO3-delta) was stable till 500 degrees C in CO2 but reacted beyond that (>500 degrees C) forming the undesirable BaCO3 phase. The In-doped compositions, especially x = 0 and 0.1(In = 0.3 and 0.2), were fully stable even after a long term exposure of 12 h at 700 degrees C in CO2. A similar trend was observed in H2O atmosphere as well i.e. In-containing compositions showing fully stable behavior. The In-doped compositions showed lower conductivity compared to the In-free composition due to higher defect association in dry air and lower mobility of the protonic carrier in wet air atmosphere. However, the conductivity was still higher than many reported values for similar materials. (C) 2016 Elsevier B.V. All rights reserved.