Solution combustion synthesis and surface properties of LaFeO₃ powders

LaFeO₃ powders were prepared by solution combustion synthesis (SCS) using citric acid as a fuel and metal nitrate as an oxidizer. By a simple procedure the mixed solution was held at 400 °C for 10 minutes, and single-phase perovskite-type LaFeO₃ oxide powders with good crystallinity were obtained for lean fuel compositions where the fuel-oxidizer ratio (Φ) was less than 1.0. Two species of oxygen, namely lattice oxygen and adsorbed oxygen, appeared in the deconvolution of O 1s photoelectrons measured by X-ray photoelectron spectroscopy (XPS). It was found that the activation energy for the soot combustion of the synthesized LaFeO₃ powders was closely related to the ratio of the two oxygen states. The best catalytic activity for soot combustion was obtained for LaFeO₃ powders synthesized from the Φ = 0.6-0.7 compositions where the ratio of adsorbed oxygen-to-lattice oxygen was a maximum.