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 degrees 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 (phi) was less than 1.0. Two species of oxygen, namely lattice oxygen and adsorbed oxygen, appeared in the deconvolution of O Is 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 phi = 0.6-0.7 compositions where the ratio of adsorbed oxygen-to-lattice oxygen was a maximum.