Influence of Sr2+ Concentration and A-Site Deficiency on Surface Stability of (La1 - ySry)xCr0.5Mn0.45 Ni0.05O3 -δ

Abstract

(La1–ySry)xCr0.5Mn0.45Ni0.05O3–δ (LSCMN) is a perovskite (ABO3) type mixed ionic-electronic conductive (MIEC) oxide and has been proposed as an electrode material for high temperature fuel cell. The material is catalytically active for oxidation of hydrogen and hydrocarbons. A significant amount of attention has been paid to stability issues if the material is used as an anode in a solid oxide fuel cell. So far, there is a lack of information about the dependence between A-site stoichiometry and stability performance of LSCMN surface. The La/Sr ratio and deficiency of A-site, i.e. A-site stoichiometry of (La1–ySry)xCr0.5Mn0.45Ni0.05O3–δ were varied and chemical composition of LSCMN surface and lattice parameters was studied. The chemical and structural changes of the material surface (segregation of some LSCMN components onto the surface and decomposition of perovskite phase) have a key role in the electrochemical performance and initial degradation rate of the electrode. XRD results for studied electrode powders showed significant dependence of the lattice parameters on the A-site composition. Materials were treated in synthetic air and in H2 environment. TOF SIMS analysis demonstrated the dependence of the surface stoichiometry on the A-site composition of bulk electrode as well as on the different gas environments after heat treatment. To improve the durability of the solid oxide cell fuel electrodes, it is inevitable to understand the degradation mechanisms during the cell operation and during cell fabrication.