Preparation And Luminescence Properties Of Li⁺,Na⁺,Eu³⁺Codoping Gd₂O₃ And CaWO₄ Phosphors

It has very important applications for rare earth red phosphors in the field of the lighting, display and detection. Among them, Gd₂O₃:Eu³⁺with excellent electro luminescent properties, it is potential materials in high resolution display device has great potential. But how to improve the luminous efficiency and practice application for it, a large number of experiments need to be expanded. In addition, calcium tungstate, its resistance advantages, stable chemical properties, low price, low cost,easy preparation, radiation, coupled with the Eu³⁺ ions, especially CaWO₄:Eu³⁺, its emitting great strength in infrared, so it is another hot spot for it applicated in LED red fluorescent powder. Considering the less research about alkali metal ion doped Gd₂O₃:Eu³⁺ and CaWO₄:Eu³⁺ red fluorescence powder and luminescence properties in the domestic and foreign, solid the alkali metal Li⁺, Na⁺, Eu³⁺doped Gd₂O₃ and CaWO₄ two kinds of matrix are prepared. X-ray diffraction, scanning electron microscope（SEM）, transmission electron microscopy, excitation and emission spectra of the samples were characterized. The effect on alkali metal ions such as microstructure, synthesis and luminescence properties for Gd₂O₃:Eu³⁺ and CaWO₄:Eu³⁺ are given, as follows:In chapter 1, the luminescent materials and their luminescence methods are introduced. The characteristics and synthesis methods of rare earth luminescent materials are introduced for The research content for Gd₂O₃:Eu³⁺ and CaWO₄:Eu³⁺red fluorescent powder are introduced, and the significance and innovation for this work is given.In chapter 2, the anodized Gd₂O₃:Eu³⁺ phosphor doped with Na⁺, Li⁺ and co-doped with Li⁺, Na⁺is prepared by microwave solid-state reaction method. The effects of doping concentration and calcined temperature on the luminescence structure, morphology and luminescence intensity of the synthesized samples were discussed. After being acclaimed at 800℃ in the air for 2h, the samples particle size are in 50 80 nm. When the thickness of Eu³⁺ is 4.5 mol %. The light intensity of Eu³⁺ and Gd₂O₃ phosphor powder is in the strongest situation. The luminescence intensity increase with the Li⁺, Na⁺of doping concentration. The luminous intensity of Gd₂O₃:Eu³⁺ phosphors just doped with Li⁺, Na⁺ and co-doped with Li⁺, Na⁺ is4.6,5.8 and 7.2 times as strong as that without Li⁺, Na⁺ doped.In chapter 3, Gd₂O₃: Eu³⁺phosphor powder doped with Li⁺is prepared byco-precipitation reaction. The effect of different calcinations temperature, doping ions and precipitating agent on the luminescence intensity of Gd₂O₃:Eu³⁺ phosphor also are discussed. The results show that the solid particle size of sample which is prepared by co-precipitation method is 30⁵0nm. In the same conditions, without incorporation of Li⁺ samples, co-precipitation prepared samples of lumpiness’ s intensity is 5.8 times as strong as the samples prepared by solid phase method;incorporation of Li⁺ sample, co-precipitation prepared sample of luminous intensity is 1.5 times as strong as prepared by solid phase method. When C2H2O4 is used as precipitation agent, the emission of the sample with 4.5 mol% Li⁺and 4.5 mol% Eu³⁺co-doped Gd₂O₃ is 1.4 times than that only with 4.5 mol%Li⁺. Alkali metal doped on the fluorescent powder body field symmetry reduction and surface defects and surface radioactive relaxation center increase, in addition of alkali metal as charge compensation agent, sensitizing agent, cosolvents and lubricants can make the sample enhancement in the luminescence intensity.In chapter 4, the nanosized CaWO₄:Eu³⁺phosphors doped with Na⁺, Li⁺is prepared by microwave solid-state reaction. The effect of the best Eu³⁺ doping concentration, calcined temperature, doping ions with Na⁺, Li⁺ on the luminescence intensity are discussed. The result shows that the samples are similar to oval and the sizes are the same. The particles stack up together. The grain size of the sample becomes larger due to Li⁺ and Na⁺ as flux. CaWO₄: Eu³⁺ in the near ultraviolet light under the excitation of 393 nm, the main peak of 615 nm is⁵D₂â†'⁷F₀ corresponding to the transition of Eu³⁺. Alkali metal Li⁺ and Na⁺ as charge compensation agent make the luminescence intensity increase in different degree.In chapter 5, the summary and outlook are given.