Sol-gel synthesis of a new oxide-ion conductor Sr- and Mg-doped LaGaO3 perovskite

Sr- and Mg-doped LaGaO3 powders were prepared from a salt acetate solution. The stable solution was peptized by reacting ammonium hydroxide with the precursor solution, Thermal analysis (DTA/TGA) was used to characterize first the dehydration and then the thermal decomposition of the organic ligands of the dried gel, The transformation from amorphous powders into a crystallized, homogeneous oxide phase corresponds to two endothermic peaks in the DTA curve; the first one at 150 degrees C is related to the removal of water and is followed by a shoulder at 250 degrees C. The second peak at 300 degrees C corresponds to a superposition of two decomposition reactions: acetate salt into its oxycarbonate and this oxycarbonate into its oxide. Two subsequent exothermic peaks correspond to oxidation of evolved gases such as methane, hydrogen, and carbon monoxide, TEM observations show an average 10 nm particle size of the LaGaO3 powder after annealing at 600 degrees C. X-ray diffraction patterns indicate a pure primitive-cubic phase is formed by 1300 degrees C without formation of any SrLaGaO3 impurity. The impedance spectroscopy on a 93%-dense sample exhibits no grain-boundary contribution and an ac conductivity sigma = 0.11 Ohm(-1) . cm(-1) at 800 degrees C.