Microwave synthesis of LaBO3 (B = Co, Fe) perovskites using graphite and citric acid additions

We studied the effects of graphite and citric acid additions on the formation of LaFeO3 and LaCoO3 perovskites upon microwave treatment of crystalline hydrates or nitrate solutions, respectively. The addition of graphite was shown to increase the yield of LaCoO3 perovskite and to result in the formation of crystalline LaFeO3 perovskite even at the microwave treatment stage. Subsequent thermal treatment at 800°C yields single-phase lanthanum ferrite with a high specific surface area (11 m2/g). Due to the addition of citric acid to nitrate solutions, a highly viscous gel forms, which allows preparation of single-phase perovskites with a high specific surface area (up to 34 m2/g) after microwave treatment and calcination. The samples obtained using the admixtures are characterized by a high catalytic activity in methane oxidation. No single-phase oxides form without introduction of these admixtures.