Abstract.Our contribution has focused on the synthesis and characterization of lanthanum monoaluminate LaAlO3 by the method of co-precipitation. The powder was successfully synthesized using NaOH, La (NO 3 ) 3 .6H 2 O and Al (NO 3 ) 3 .9H 2 O as raw materials by this method and calcined at different temperatures. It was characterized by several techniques: Fourier transform infrared spectroscopy (FT-IR), thermogravimetric and differential thermal analysis (TGA/DTA), X-ray diffraction (XRD) and laser diffusion. All the results for physico-chemicals characterizations show that the crystallization temperature of the LaAlO 3 precursor gels precipitated is estimated as 790 °C by TG/DTA. The XRD pattern of the LaAlO 3 precursor gels calcined at 700 •C for 6 h has a perovskite structure of rhombohedral hexagonal phase formed and the presence of crystalline impurities is not found. The crystallite size of LaAlO 3 slightly increases from 31to 44.5 nm with calcination temperature increasing from 700to1000 °C for 6 h.

Perovskite LaCr 1-x Co x O 3 (0 B x B 0.5) oxides synthesized by co precipitation method were investigated. X-ray diffraction, thermo gravimetric and differential thermal analysis, Fourier transform infrared spectroscopy, scanning electron microscopy (SEM) and electrochemical measurements, were used to characterize the structure, morphology, electrochemical properties of the samples. The studied compounds have orthorhombic and rhombohedral systems in the ranges (0 B x B 0.2) and (0.3 B x B 0.5) respectively. Thermal analysis results indicate that the pure phase was obtained at temperature above 800°C. The structure and morphology of the samples characterized by SEM measurements indicate that particles have nearly spherical shapes and are agglomerated. The electrochemical measurements indicate that the catalytic activity is strongly influenced by cobalt doping. The highest electrode performance is achieved with large cobalt content.