Preparation and characterization of LaAlO3

Lanthanum aluminate has been prepared by combustion synthesis process using nitrate salts of lanthanum and aluminium as cation precursors and urea as the fuel. The powder density and the compacted pellet density have been determined. Sintering process reduces the porosity of the pellets by the agglomeration process. The conductivity of LaAlO3 increases with sintering temperature and the value is found to be 1.75 S cm(-1) at 1000 degrees C. The dielectric constant and loss tangent values are found to decrease with the applied frequency. This may be due to the change in orientation and ionic effects resulted from the inertia of ions and molecular levels. The XRD studies reveal that the material is assigned to be a pseudocubic structure. The FTIR spectra show the higher frequency and lower frequency bands are assigned to AlO6 octahedra in LaAlO3. SEM micrographs divulge the presence of platelet aggregates into globular mass with larger surface area. The electrochemical polarization was performed for as synthesized and sintered LaAlO3 materials in 0.5-2.0 M KOH. In general the corrosion kinetic parameters elucidate the fact that the green samples are found to be prone to corrosion than the sintered materials. (c) 2007 Elsevier B.V. All rights reserved.