Stability and conductivity study of the BaCe0.9-xZrxY0.1O2.95 systems

Solid oxide components such as protonic separation membranes for the hydrogen purification and electrolyte for solid oxide fuel cell require thermo-chemical stability and high conductance. The perovskite BaCe0.9Y0.1O2.95 exhibits good proton conduction at high temperatures, but shows poor thermo-chemical stability. Substituting Zr for Cc in BaCe0.9Y0.1O2.95 improves the thermo-chemical stability but reduces proton conduction. The objective of this work was to study the optimization of protonic conductance and thermo-chemical stability by changing the ratio of Ce to Zr in BaCe0.9-xZrxY0.1O2.95. To elucidate the dopant effect, a coprecipitation and freeze drying method has been developed to produce single phase perovskites of BaCe0.9-xZrxY0.1O2.95 (0 <= x <= 0.9). The method has been optimized to yield high purity and homogeneous powders with a particle size of 50-100 nm in diameter. The sintering characteristics were studied in the temperature range of 1400-1650 degrees C. BaCe0.9Y0.1O2.95, BaCe0.7Zr0.2Y0.1O2.95 and BaCe0.5Zr0.4Y0.1O2.95 can be sintered to high density at 1650 degrees C. Sintered BaCe0.5Zr0.4Y0.1O2.95 and BaCe0.3Zr0.6Y0.1O2.95 show good chemical stability against water and carbon dioxide. Electric conductivities of sintered samples, which have been measured by impedance spectroscopy, decrease with their Zr content. (c) 2006 Elsevier B.V. All rights reserved.