Abstract

In this work, two perovskites (SrCo0.95Ir0.05O3-delta and SrCo0.95Ta0.05O3-delta) have been prepared, characterized, and tested as cathode materials for intermediate-temperature solid-oxide fuel cells, producing maximum power densities of 600 and 300 mW cm(-2) at 850 degrees C, respectively. The introduction of only a 5% of 02 highly charged cations like Ir4+ and Ta5+ at the Co sites of the SrCoO3-delta system stabilizes a tetragonal polytype, at room temperature, and improves some essential properties such as the electrical conductivity or the polarization resistances with the electrolyte. These two materials have been characterized by X-ray diffraction and neutron powder diffraction (NPD) at 25 degrees C; an in situ NPD analysis was carried out from 200 to 800 degrees C for SrCo0.95Ta0.05O3-delta in order to study the thermal evolution of the crystal structure. In complement, the chemical or mechanical compatibility of these materials with La0.8Sr0.2Ga0.83Mg0.17 O3-delta electrolyte, and a thermogravimetric analysis from 25 to 900 degrees C are investigated. Finally, a XPS study confirms the surface oxidation states of Co, Ta, and Ir in the SrCo0.95Ir0.05O3-delta and SrCo(0.95)Ta(0.05)O(3-delta )perovskite specimens.