Transport properties of BaCe0.95Y0.05O3-alpha mixed conductors for hydrogen separation

We have characterized the transport properties of a mixed ionic-electronic conductor, BaCe0.95Y0.05O3-alpha (BCY), by using impedance spectroscopy and open-cell voltage measurements. Such mixed conductors have many applications, including hydrogen separation. Results indicate that in an oxygen/water vapor atmosphere, proton conduction is dominant at low temperatures (500 to 600 degrees C) while oxygen ion conduction dominates at higher temperatures (700 to 800 degrees C). In a hydrogen/water vapor atmosphere, however, proton conduction dominates over the entire temperature range studied (500 to 800 degrees C). The proton conductivity of BCY ranges from 1.9 x 10(-3) Omega(-1) cm(-1) at 800 degrees C in an oxygen/water vapor atmosphere to 1.27 x 10(-2) Omega(-1) cm(-1) in a hydrogen/water vapor atmosphere. Compared to protonic conductivity (approximate to 7.2 x 10(-3) Omega(-1) cm(-1)), electronic conductivity in a H-2/H2O atmosphere is relatively low (approximate to 2.1 x 10(-3) Omega(-1) cm(-1)) at 700 degrees C and must be enhanced in order to improve the rate of gas permeation when BCY is used as a membrane for gas separation.