An X-ray powder diffraction study of lanthanum- strontium ferromanganites

Various lanthanum-strontium ferromanganites (La1-xSrx)(Mn1-yFey)O3 +/- delta (LSMF) with x = 0.2, 0.5 and 0.7 and y = 0.2, 0.5 and 0.8 were prepared by a glycine-nitrate combustion route and conditioned into two different oxygenation states which are likely to be encountered in cathode materials for solid oxide fuel cells (SOFC). Crystal symmetries for both the low and the fully oxygenated states were determined by X-ray diffractometry. Most perovskite compositions crystallized in either cubic or rhombohedral symmetry with the exception of La0.5Sr0.5Mn0.2Fe0.8O3 +/- delta, where a transition from rhombohedral to cubic occurred in going from the full to the low oxygenation state. In addition, two strontium-poor compositions, La0.8Sr0.2Mn0.5Fe0.5O3 +/- delta and La0.8Sr0.2Mn0.2Fe0.8O3 +/- delta, remained diphasic and consisted of a combination of both the rhombohedral and the orthorhombic phases. Changes in unit cell volume were analyzed as a function of chemical composition and oxygenated state. (C) 2001 Elsevier Science B.V. All rights reserved.