Crystal structure, thermochemical stability, electrical and magnetic properties of the two-phase composites in the La_0.8Sr_0.2MnO_3±δ-CeO₂ system

Crystal structure, thermochemical stability, transport and magnetic properties of compositions in the (100-x) La(0.8)Sr(0.2)MnO(3 +/- delta)xCeO(2) (LSMC) system were studied. All compositions in the LSMC series containing more than 2 mol% CeO2 were two phase and consisted of the modified perovskite constituent with rhombohedral structure (R3c) and ceria as a secondary phase with cubic structure (Fm3m). The presence of both Ce4+ and Ce3+ cations in LSMC compositions was revealed by X-ray Photoelectron Spectroscopy (XPS). CeO2 and compositions in the LSMC series showed good thermochemical stability in air and argon. However. in H-2-Ar atmosphere all LSMC compositions underwent reduction followed by decomposition. Transport and magnetic properties change in a non-linear way with the increase in the CeO2 content. The LSMC2 composition showed enhanced electronic conductivity and magnetic characteristics. Metallic type conductivity was observed for LSMC compositions with x <= 36 mol% CeO2 in a narrow temperature range of 770-900 degrees C. A small degree of substitution of Ce into LSM was found to change structural, magnetic and electrical properties. (C) 2009 Elsevier B.V. All rights reserved.