ELECTROCHEMICAL BEHAVIOR OF ORDERED OXYGEN-DEFICIENT PEROVSKITES LnBaCo2O5+ (Ln = Pr, Nd, Sm and Gd) USED AS CATHODE OF IT-SOFC

摘要

LnBaCo2O5+δ (Ln=Pr, Nd, Sm and Gd) double perovskite oxides have been synthesized by a combined EDTA and citrate complexing method and characterized as cathode for intermediate temperature SOFC (IT-SOFC) by powder X-ray diffraction (XRD), electrical conductivity and thermal expansion coefficient(TEC) measurements, as well as the electrochemical impedance spectra measurement. According to the XRD results, a single phase structure has been formed for LnBaCo2O5+δ after calcinations at 1100℃ for 10h, and the lattice volume decreases from Ln=Pr to Gd. LnBaCo2O5+δ oxides show high electrical conductivity, large thermal expansion coefficient (TEC) and outstanding electrochemical performance. But the properties of LnBaCo2O5+δ oxides are greatly influenced by A-site Ln3+ ions. The electrical conductivity, TEC and electrocatalytic activity decrease on going from Ln=Pr to Gd. Compared with other oxides, PrBaCo2O5+δ exhibits better electrochemical performance (lower polarization resistance), which should be largely contributed to its higher oxygen ion conductivity, superior oxygen diffusion rates and faster surface exchange kinetics.