Chemical synthesis and structural characterization of the substitution compound LaFe1-xCuxO3 (x=0-0.40)

LaFe1-xCuxO3 samples with x = 0, 0.05, 0.10, 0.20 and 0.40 were prepared by citrate auto-combustion synthesis; up to x = 0.20 lanthanum ferrites are free from impurity, while for x = 0.40 molar content of copper a small amount of La2CuO4 and traces of CuO are present. The crystal structures of LaFe1-xCuxO3, with x = 0.05, 0.10 and 0.20 have been established through the Rietveld method applied to powder X-ray diffraction data. All compounds exhibit the orthorhombic symmetry (space group Pnma) and crystallize in the perovskite-like cell of LaFeO3, with octahedral sites occupied by a mixture of Fe and Cu and lanthanum atoms 12-fold coordinated. For x = 0-0.20 the oxidation state of iron cations was determined by redox titration to be Fe3+. The charge compensation required by the substitution of Fe3+ by Cu2+ is achieved by the elimination of oxygen atoms. The consistency of the crystal data with the charge compensation mechanism is discussed. (C) 2009 Elsevier B.V. All rights reserved.