Synthesis of nanometer crystalline lanthanum chromite powders by the citrate-nitrate autoignition reaction

Lanthanum chromite-based materials have a great potential for use in variou s high temperature applications and as SOFC (solid oxide fuel cell) separat ors. Submicron crystalline lanthanum chromite was prepared by the autoignit ion of a citrate- nitrate gel. The effect of the fuel- oxidant molar ratio and sample form prior to combustion was investigated in terms of phase form ation, particle size, morphology, and agglomerate formation. Various charac terization methods, including X-ray powder diffraction and thermal analysis , scanning electron microscopy and BET measurement, were used to evaluate p owder characteristics. It was shown that the reaction period depends on the fuel/oxidant ratio and reaction mixture packing. The lanthanum chromite po wders prepared via the combustion route exhibited surface areas of about 12 m(2)/g for the loose packed layer prepared samples and 8.8 to 13 m(2)/g fo r the samples prepared from a pellet.