Performance of Ca-doped GdBa1-xCaxFe2O5+δ(x = 0, 0.1) as cathode materials for IT-SOFC application

Abstract

GdBaFe2O5+δ doping with Ca to subsitute Ba in A site were prepared by the citric-nitrate process. The effects of different contents of Ca on the physical and chemical properties and electrochemical properties of GdBa1-xCaxFe2O5+δ were investigated. It is shown that with the increasing of Ca content, GdBa1-xCaxFe2O5+δ remains pure phase within the amount of doping is less than 20%, otherwise BaFe2O4 miscellaneous phase appears. The XPS result shows that the valence of Fe increases continuously, that is, Fe3+ continuously changes to Fe4+, as the content of Ca increases. According to the principle of conservation of charge, the oxygen content of the material increases continuously. However, with the further increase of Ca content, the high-speed oxygen conduction on the ab axis is affected when the BaO bond is destroyed to a certain degree, and the conduction velocity is significantly reduced (dominant factor), resulting the highest conductivity 9.57 S cm−1 at Ca content of 10%. With the increase of Ca content, electron hole and oxygen content in the material are increasing, also led to the continuous decrease of the polarization resistance of the material, when the Ca content ascended to 20%, the minimum polarization impedance will be to 0.0415 Ω cm2, δ increases to 5.8199, and the polarization process increases.