Synthesis and characterization of Ba0.6Sr0.4Ce0.8−xZrxY0.2O3−δ proton-conducting oxides for use as fuel cell electrolyte

Abstract

Ba0.6Sr0.4Ce0.8−xZrxY0.2O3−δ (x = 0–0.8) proton-conducting oxides are prepared using a sol–gel complexing process. The effects of the Ce/Zr ratio on various material properties are systematically investigated. The sintered samples show a perovskite crystal structure without impurity phases and have a rather compact interior, making them suitable for use as a fuel cell electrolyte. Increasing the Zr content in the oxides causes lattice constriction and suppresses grain growth during sintering at 1600 °C. The ionic conductivity of the oxides increases with increasing Ce/Zr ratio. At 800 °C, Ba0.6Sr0.4Ce0.8Y0.2O3−δ has a conductivity of as high as 0.14 S/cm. However, X-ray diffraction and Raman spectroscopy evaluations show that this oxide cannot withstand a CO2 atmosphere. A suitable substitution of Ce with Zr in the structure significantly improves the chemical stability of the oxide without significantly degrading conductivity.