Ca and Pr substitution promoted the cell performance in LnSr3Fe3O10-δ cathode for solid oxide fuel cells
The substitution of Ca for Sr in the LnSr3-xCaxFe3O10-δ (x = 0–1.5, Ln = La, Pr, and Sm), Ruddlesden-Popper (RP) intergrowth structure was investigated to determine how the physical and electrochemical properties of this potential cathode material in solid oxide fuel cells (SOFCs) are impacted. A small amount of Ca incorporated into the structure reduced the thermal expansion coefficient, improved the electrical conductivity, and increased power density by up to 30% of a La0.8Sr0.2Ga0.8Mg0.2O3 electrolyte-supported single cell. The microstructure and oxygen permeability of the materials were independent of Ca substitution. A phase transformation of LaSr3-xCaxFe3O10-δ to perovskite was observed when the Ca composition of x > 1.0. Among the substitution of Pr and Sm for La in LaSr2.7Ca0.3Fe3O10-δ, only PrSr2.7Ca0.3Fe3O10-δ was pure with no phase transformation found. The co-substitution of Pr and Ca promoted the reduction of Fe, enhanced the oxygen permeation and active surface, and diminished the contact resistance at the cathode-electrolyte interlayer. The co-substitution of Ca and Pr delivered good electrochemical performance of approximately 354 mWcm−2 at 800 °C on a 0.3 mm thick La0.8Sr0.2Ga0.8Mg0.2O3 electrolyte-supported cell and the lowest area specific resistance (ASR).