Synthesis and characterization of non-stoichiometric LaFeO3 perovskite

La(1−ε)FeO(3−1.5ε) perovskite catalysts (ε=0, 0.1, 0.2, 0.3) are synthetized by low-temperature thermal decomposition of La and Fe nitrates and further heating to 873 K in air. They are characterized by DTA, XRD, BET, SEM, Mössbauer spectroscopy and tested for the catalytic combustion of methane. All oxides are monophasic; for ε=0 the structure is orthorhombic, whereas for 0<ε≤0.3 a pseudocubic symmetry is evident. The Mössbauer spectra are characterized by antiferromagnetic sextuplets; for ε=0.3 a doublet is also present. The catalytic activity toward CH4 oxidation appears to be strongly enhanced in the samples with ε>0; the most active composition corresponds to ε=0.1, while for ε=0.2 and 0.3 the catalytic activity is slightly decreased. The results are explained assuming that the excess of iron oxide in the ε>0 samples corresponds to the presence of surface of layers of FeO5 polyhedra, coordinatively unsaturated, according to proposed structural model.