Effect of Co/Fe Ratio and Microstructural Design on the Structural and Electrical Properties of Mixed Conducting BaSrCo_1-XFe_xO_3-X

Abstract

Sr-doped LaMnO3, is commonly used as the cathode for SOFC applications due to its superior electronic conducting properties. With enhancement of ionic conduction, mixed conducting perovskites, such as BaSrCo1-xFexO3-x, may also be used as the SOFC cathode and ion transport membranes for gas separation. However, the structural /electrical properties of BaSrCo1-xFexO3-x are not only highly dependent upon the Co/Fe ratio but also on the microstructural design. In this study, Ba0.5Sr0.5Co1-xFexO3-x, is first fabricated by using carbonates/oxides as raw materials. Secondly, a BaSrCo1-xFexO3-x thin film is deposited on a porous BaSrCo1-xFexO3-x substrate by electrophoretic deposition technique. As a result, with high Co/Fe ratio, Ba0.5Sr0.5Co1-xFexO3-x exhibits hexagonal distortion of perovskite structure. With low Co/Fe ratio, Ba0.5Sr0.5Co1-xFexO3-x exhibits cubic perovskite structure. The structure evolution is rationalized based on XRD and XPS analysis in addition to the consideration of cationic valence and radii. The mixed conduction behaviors of Ba0.5Sr0.5Co1-xFexO3-x is rationalized based on the defect types and charge compensation mechanism. The sintering and densification of Ba0.5Sr0.5Co1-xFexO3-x is examined as a function of Co/Fe ratio. The microstructure of catalytic layers were also investigated. Finally, the enhancement of oxygen permeation through thin-film membrane is demonstrated as well.