Study On The Preparation And Photocatalytic Activity Of Perovskite Rare Earth Composite Oxides Nanocrystalline

Nanoparticles and nanocluster materials are a new class of advanced materials exhibiting unique chemical and physical properties compared to those of their bulk materials. Pollution abatement using semiconductor materials as photocatalysts under sunlight has been a subject of great interest. It is very important in theory and application. In our present work, the preparation and photocatalytic activity of perovskite-type rare earth composite oxides nanocrystalline were studied in order to find some effective ways to improve the photocatalytic activity.LaCoO₃ perovskite-type composite oxides are a series of important functional materials. Recent studies show that they have significant promise in the fields of electrics, magnetics, catalysis and luminescence. So, they were selected as the research subjects in our present work. LaCoO₃ and LaCoO₃ complex oxides partly doped in A-site or B-site or AB-site were synthesized by complexing sol-gel method, in which ethylen-diamine-tetraacetic acid (EDTA) or citric acid (CA) was used as the chelating agent, and polyethylene glycol (PEG) was used as polymerization agent. The heat decomposition mechanism of the gel, the formation process, crystal structure, micrograph and particle size of the nanocrystallines were investigated by TG-DTA, XRD, SEM respectively. The results show that the nanocrystalline of pure perovskite-type composite oxides can be obtained at relatively lower temperature. The particles of the nanocrystalline are fine in size, spherical in shape and dispersing well. Compared with traditional solid state reaction, this complexing sol-gel route has several remarkable advantages. Because of the greater ability of EDTA and CA anions to chelate metal cations, and forming very stable and soluble complexes, all of the starting materials are mixed at the molecular or atoms level in a solution, it is easy to control the composition and a high degree of homogeneity is achievable. In addition, the polymerization reaction of EDTA or CA induced by PEG can greatly inhibit cation segregation and /or fluctuation of chemical constitutents. Moreover, low calcining temperature is anticipated because of the high specific...