Precursor Thermal Decomposition Synthesis Of Rare Earth Complex Oxides And Property Research

Rare earth complex oxides have wide applications in various fields such as catalysis, optics, and biology analysis, due to their unique chemical and physical properties. It should be of great significant to develop novel synthetic approaches for rare earth complex oxides, investigate the formation mechanisms of rare earth complex oxides and research the composition-structure-property relationships. This dissertation explored novel precursor thermal decomposition synthetic approaches for series of rare earth mixed oxides with novel nanostructures, such as LnAlO3perovskite-type oxides and Ln2O3-Al2O3mixed oxides. The products produced by precursor thermal decomposition method have well-distributed grain diameters and good dispersivity. In this work, we successfully synthesized LaA103hollowspheres, rare earth chromate nanoparticles, YAP:Eu3+and YAG:Eu3+nanophosphors and Ag/La2O3-Al2O3porous materials, and investigated their luminescence properties and catalytic properties in details.LaAlO3hollow spheres were synthesized by the precursor thermal decomposition method. The morphologies of the precursors and the products were characterized by TEM and SEM. The precursors annealed at different temperature were investigated by XRD, FTIR and TG. The formation process of the LaAlO3hollow spheres included two steps. First, capsule-like organic-inorganic hybrid precursors were synthesized by the glycol solvothermal method. Then the precursors were annealed and converted to LaAlO3hollow spheres. Three kinds of luminescenct hollowspheres (LaAl03:Ln3+, Ln=Tb, Sm, Eu)were synthesized and their luminescent properties were carefully investigated. This approach was extended to successfully synthesize other two kinds of rare earth aluminate hollow spheres, such as PrAlO3and NdAl03hollow spheres. These luminescent hollowspheres might find potential applications in the fields of drug deliver and biological labeling.Two different phosphor powder of YAP:Eu3+and YAG:Eu3+were synthesized by precursor thermal decomposition method.The powders of YAP:Eu3+and YAG:Eu3+were investigated by SEM, XRD and FT-IR spectra. The results revealed that symmetry of the lattice structures of the two powders have significant influence on the morphologies and relative intensity of5D0â†'7F1and5D0â†'7F2transitions. The crystalline field’s intensity of two powders has critical influence on their photoluminescent properties.A precursor thermal decomposition method was developed for the synthesis of series of rare earth chromate. The formation mechanism of rare earth chromate complex oxides was investigated by taking GdCrO3as an example. The morphologies and lattice structures change with the increase of atomic number of rare earth elements. When Al3+and Cr3+ions were simultaneously introduced into glycol system, LaCrxAl1-xO3was synthesized and the properties of LaCrxAl1-xO3were investigated. The catalytic activity for CO oxidation over rare earth chromate and LaCrxAl1-xO3were evaluated to investigate the structural and compositional influence on catalytic properties.La2O3-Al2O3porous materials were successfully synthesized based on the precursor thermal decomposition method by tuning the La/Al molar ratio in the synthetic system. Furthermore, series of Ag doped La203-Al203porous catalysts were synthesized by in-suit introducing Ag+ions into the synthetic system. The formation mechanism of Ag/La2O3-Al2O3was investigated. The catalytic activities of as-prepared Ag/La2O3-Al2O3catalysts were evaluated by CO oxidation. The influence of La/Al molar ratio on their morphologies, surface area, and catalytic activity were investigated. A comparative study between Ag/La2O3-Al2O3catalyst and the comparision prepared by impregnation method was carried out to illustrate that the Ag/La2O3-Al2O3catalyst prepared by precursor thermal decomposition method posseses better catalytic activity and higher thermal stability.