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 Ce 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 °C. BaCe0.9Y0.1O2.95, BaCe0.7Zr0.2Y0.1O2.95 and BaCe0.5Zr0.4Y0.1O2.95 can be sintered to high density at 1650 °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.