Investigation on Proton Conductivity of La2Ce2O7 in Wet Atmosphere: Dependence on Water Vapor Partial Pressure

The AC conductivity of fluorite-structured La2Ce2O7 ceramic was measured under air and argon with different humidity between 250 and 550 degrees C. It was observed that the total conductivity in wet air and argon was higher than that under dry atmospheres. The effect of water vapor partial pressure (PH2O) on the conductivity of La2Ce2O7 in air was investigated in detail. The total conductivity increased remarkably with the water vapor partial pressure, and this phenomenon became more notable at lower temperatures. The enhancement of the conductivity was attributed to the proton conduction behavior of La2Ce2O7 in wet atmospheres, and the proton conductivity reached 6.68 x 105 S cm1 in wet air (3% H2O) at 550 degrees C. The relationship between the proton conductivity (rho H) and PH2O in wet air could be fitted to rho H proportional to P1/2H2O. The estimated proton transport number increased with increasing water vapor partial pressure and decreasing temperature, and varied between 0.05 and 0.89 in this study.