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

Abstract

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.