Luminescent Materials Of Ceo <sub> 2 </ Sub>: Of Sm (3 +), The Yvo <sub> 4 </ Sub>: Dy (3 +), Ga <sub> 2 </ Sub> O <sub> 3 </ Sub>: Eu (3 +) Preparation And Characterization

The material composition, structure, microscopic appearanceand and microscopic criterion display the decisive influence to its final performance. During the past decade, a wide range studies has been performed on the shape-and size-controlled synthesis of nanostructured/monodisperse materials due to their strong size-and shape-dependent properties. Therefore, it is very important to fine tune the size, dimensionalities, crystal structure and compositions of complex oxides in nanoscale, which may serve as a powerful tool for the tailoring of physicallchemical properties of complex oxides in a controllable fashion.Micrometer-sized CeO₂ powders with bundle-and flake-like morphologies have been successfully synthesized by a precursor-pyrolysis approach, in which the precursors is first synthesized by a hydrothermal method and CeO₂ powders are finally obtained through a pyrolysis process. Results reveal that the stoichiometric concentration of cerium ions plays an important role in the formation of the final products with different morphologies. The possible growth process is proposed by arresting a series of intermediate morphologies during the shape evolution of bundle-like CeO₂ based on the SEM image observation. In addition, the room-temperature photoluminescence properties were investigated. The relative intensity of the emission bands in bundle-like CeO₂ is much stronger than that in flake-like CeO₂. Sm³⁺-doped CeO₂ nanorods were synthesized and the optical properties of products were investigated.Dy³⁺-doped YVO₄ nanorods were synthesized via a low temperature hydrothermal route. The structures and optical properties of products were investigated. From the emission spectra, the as-prepared nanorods possess improved chromaticity compared with the irregular particles, and by change the calcinations temperature, the chromaticity can be tuned.α-Ga₂O₃: Eu³⁺ andβ-Ga₂O₃: Eu³⁺ powders in ellipsoid-like and spindle-like shapes have been successfully prepared by surfactant-free hydrothermal process. Andα-Ga₂O₃: Eu³⁺ andβ-Ga₂O₃: Eu³⁺ were converted from as-prepared GaOOH: Eu³⁺ particles by dehydration at 500℃and 850℃, respectively. The structures and optical properties of products were investigated. Results show that solution pH values play a key role in the formation of the GaOOH: Eu³⁺ powders with different morphologies andα-andβ-Ga₂O₃: Eu³⁺ inherit the morphology of GaOOH: Eu³⁺ exactly. Experimental results reveal that the emission intensity of spindle-like(or ellipsoid-like)β-Ga₂O₃: Eu³⁺ is superior to that ofα-Ga₂O₃: Eu³⁺ with the same morphology.