Wet Chemical Synthesis of Sr- and Mg-Doped LaGaO3, a Perovskite-Type Oxide-Ion Conductor

ISSN： 0022-4596

Source： Journal of Solid State Chemistry, Vol.136, Iss.2, 1998-03, pp. : 274-283

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Abstract

Sr- and Mg-doped LaGaO3 ultrafine powders were prepared by a sol-gel process that involves an acetate solution of the cations followed by ammonia peptization. The formed gel precursor consists of a hydrous complex of hydroxo and acetate ligands with the cations. Dehydration occurs when the gel is heated, and the complex of hydroxo and acetate ligands with the cations precipitates. Thermal analysis (DTA/TGA) reveals endothermic peaks corresponding to the decomposition of the hydroxo ligand at 220°C and the acetate ligand at 280°C followed by a strong exothermic peak at 330°C; gases are liberated by the cleavage of the CH3COO- ligands. The coupling of the endothermic peak at 280°C and the exothermic peak at 330°C is found to be a characteristic phenomenon for the breakup of the CH3COO- bond. The IR spectroscopy of products at different stages of decomposition further confirms the existence of OH- and CH3COO- ligands and the assumptions about chemical reactions made in this study. TEM observations show an average 50-nm particle size after calcination at 500°C. The X-ray diffraction patterns indicate a single perovskite cubic phase after sintering at 1400°C, yielding a 94% dense sample. Hydrothermal treatment of the gel and the Pechini method were also used for comparison. Copyright 1998 Academic Press.