Structural effects of Co and Cr substitution in LaMnO3+δ

• Published in: Journal of materials chemistry 2000-01, Vol.10 (2), p.437-443
• Main Authors: EL-FADLI, Z, METNI, M. R, SAPINA, F, MARTINEZ, E, FOLGADO, J. V, BELTRAN, D, BELTRAN, A
• Format: Article
• Language: English
• Subjects: Condensed matter: structure, mechanical and thermal properties; Exact sciences and technology; Inorganic compounds; Physics; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; Water, oxides, hydroxides, peroxides
• ISSN: 0959-9428; 1364-5501
• DOI: 10.1039/a907173c

Series of perovskite oxides with the composition LaMn1- xMxO3+delta (M = Cr, Co; x = 0-1 were synthesised by thermal treatment of precursors obtained by freeze-drying of acetic acid solutions. The oxides were characterised by XRD, and the Mn4+ content and, thus, the oxygen excess, delta, was determined by redox back-titration. LaMnO3.14 and LaCrO3 phases have the rhombohedral-LaAlO3 and the orthorhombic-GdFeO3 structures, respectively. The LaMn1-xCrxO3+delta phases have the rhomobohedral structure for x up to 0.3, and the orthorhombic structure for x = 0.5 and above. LaCoO3 has, as LaMnO3.14, the rhombohedral structure. However, the LaMn1-xCoxO3+delta phases have an orthorhombic structure of x between 0.05 and 0.55. The evolution of the crystal symmetry was interpreted by considering the effect of the size of the substituting ion on the capability of the perovskite network to accommodate the oxygen excess (delta). 19 refs.