Low temperature powder synthesis of LaAlO₃ through in situ polymerization route utilizing citric acid and ethylene glycol

Materials and Structures Laboratory, Tokyo Institute of Technology, Nagatsuta 4259, Midori-ku, Yokohama 226, Japan Powders of LaAlO₃ with large surface areas were synthesized by the polymerized complex technique based upon in situ polyesterification between citric acid (CA) and ethylene glycol (EG). Heating of a mixed solution of CA, EG, and nitrates of lanthanum and aluminium at 130°C gave brown transparent gel without any precipitation. The gel was preheated at 350°C to give a black powdery mass, which was subsequently used as a precursor for LaAlO₃. The formation of pure perovskite LaAlO₃ occurred when the precursor was heat-treated in a furnace set at 700°C for 8 h or at 750°C for 2 h. No X-ray diffraction evidence for the presence of crystalline impurities was obtained. The LalO₃ powder prepared by the polymerized complex method had a considerably large surface area in the range of 13-16 m² g^-1 when compared with ∼0.3 m² g^-1 for the conventional solid-state reaction powder of the same compound.