| Lumineseent materials based on lanthanide ions not only have good spectrographic properties of rare earth ions, but also have the huge application value as phosphors in solid-state laser, components in optical communication, lamps and display device and solar cells. Therefore, it is the main theme to study various luminous properties of rare earth doped lumineseent materials and improve the luminous efficiency. Tetragonal-phased LiYF4:Yb3+/Er3+and LiYbF4:Yb3+/Er3+crystal particles with octagonal morphology are prepared by hydrothermal method and characterized with XRD and SEM. The up-conversion fluorescence has been studied with spectroscopic method. The results showed that crystallization and particle size was adjusted by introducing EDTA (Ethylene Diamine Tetraacetic Acid), which finally introduced the change of fluorescence intensity. Green fluorescence emissions from4S3/2â†'4I15/2and2H11/2â†'4I15/2transitions, violet emission from2H9/2â†'4I15/2transition, and red emission from4F9/2â†'4I15/2were observed when the samples were excited with980nm IR laser. Meanwhile, the mechanism and the influence of the host matrix on the upconversion fluorescence emission of LiYF4:/Er3+and LiYF4:Yb3+/Er3+crystal particles have been discussed too.Part one:the compound of tetragonal LiY(Yb)F4:Yb3+/Er3+Crystal Particles and the research of upconversion of Emission spectraAnalysing the XRD (X-Ray Diffraction), SEM (Scanning Electron Microscopy) diagram and upconversion fluorescence spectra, showed that the introduction of EDTA leds to a change in the average size, surface morphology, crystallinity and luminous intensity, etc. Observing the SEM images, we can clearly see the added EDTA crystal particle which surface is smoother, more regular morphology, and more uniform size, but without EDTA, uneven surface and the irregular morphology of crystal particles. And after the experiment proceeds we see the luminescence intensity of the sample which has without EDTA than the added EDTA stronger. Analysis of the regulatory role of the matrix changes in fluorescence emission, the results show that LiYF4:Yb3+/Er3+crystal particles lead to green fluorescence emissions and LiYbF4:Yb3+/Er3+crystal particles lead to yellow fluorescence emissions.Part two:the upconversion fluorescence emission of LiYF4:/Er3+and LiYF4:Yb3+/Er3+crystal particles and the concentration of Yb3+for the influence of the fluorescence intensityIn this paper, the method of Hydrothermal Synthesis was used to prepare single blending of LiYF4:/Er3+and LiYF4:Yb3+/Er3+crystal particles. The Fluorescence spectrum measurements of LiYF4:/Er3+and LiYF4:Yb3+/Er3+crystal particles showed that the introduction of Yb3+have a significantly for enhancing the fluorescence emission of Er3+. Analysing produces more spectrum line by the energy level split. Meanwhile, we analyzed an discussed mechanism of upconversion emissions of LiYF4:/Er3+and LiYF4:Yb3+/Er3+crystal particles excited with980.0nm laser. And while the concentration of Yb3+increased from0mol%to20mol%, the fluorescence intensity of the sample continued to enhance. When the concentration of Yb3+increased to20mol%, the fluorescence intensity reached the largest, otherwise the concentration of Yb3+continued to increase, the fluorescence appeared reduced. The possible cause that more Y3+where sites of Yb3+ions are replaced in the sample, so that the distance between the Yb3+and Er3+of crystal was shortened, and enhanced the interaction between the ions. which make the lifetime of Yb3+ion to shorten in the excited state level, therefore, resulting in weakening of fluorescence intensity. There are a number of other the undetached out impurities in the sample, so that the energy transfers to impurity ions and the formation of quenching centers, or to exist Interaction between activate ions and the host material and the energy transfers to the lattice imperfections, what would give rise to the weakening of the fluorescence. |
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