Eu2SrCo1.5Fe0.5O7 a new promising Ruddlesden–Popper member as a cathode component for intermediate temperature solid oxide fuel cells

Abstract

A new oxide of the Ruddlesden–Popper series in the (Eu,Sr)_n+1(Co,Fe)_nO_3n+1 system has been isolated and structurally characterized. X-ray diffraction and electron microscopy show that polycrystalline Eu₂SrCo_1.5Fe_0.5O₇ constitutes the n = 2 member of a homologous series, the essential feature of which is the existence of two connected Co/Fe octahedral layers with a perovskite-like structure, linked by an EuO rock-salt like layer. Random distributions of 3d-metals in the perovskite blocks and interstitial and oxygen vacancies in the rock-salt layers (anti Frenkel defects) are observed by electron microscopy. Such facts are commonly associated with high electronic conduction and ionic conductivity. The electrochemical study shows that the area-specific resistance of this compound is 0.26 Ω cm² at 700 °C in air, a value which is comparable to those of the best state-of-the-art Ruddlesden–Popper materials used as cathodes in intermediate temperature solid oxide fuel cells.