Spectroscopic Properties Of Tb³⁺/Sm³⁺ Doped Glass Ceramics Containing LiYF₄ Nanocrystals

In recent years,research and preparation of transparent glass,ceramics and crystal materials have attracted the attention of researchers due to the large demand for large-volume,low-cost and easy-to-manufacture new fluorescent materials.In 1976,French scholar Auzel first prepared oxyfluoride glass-ceramic material doped with Yb³⁺,Tm³⁺,and measured the absolute efficiency of optimal up-conversion.Based on the theoretical prediction of the rate equation model,it was found that the optimized host material has a low phonon frequency of 370 cm^-1under the assumption of ion-lattice coupling and small oscillator intensity variation.This discovery of optical functional materials for blue-upconversion has attracted research interest in transparent oxyfluoride glass ceramics.The rare earth ion doped aluminosilicate luminescent glass ceramic is a photoluminescent material with excellent properties.Because the material is easy to prepare and has short processing time,it has good application prospect and research value.The introduction part of this paper introduces the background of the subject,the overview of glass-ceramics,the preparation of glass-ceramics,the mechanism of rare earth luminescence and the research status of doped rare earth materials for LED luminescence.The grain structure of LiYF₄ can be introduced by DSC,XRD and TEM characterization methods.The effects of preparation temperature conditions and rare earth concentration ratio on the luminescence properties of the materials were studied in detail by transmission spectra,emission spectra,lifetime decay curves and CIE chromaticity coordinates.The second chapter studies the preparation and spectral properties of Tb³⁺activated green fluorescent glass-ceramics.By heat-treating SiO₂-Al₂O₃-YF₃-LiF precursor glass,transparent oxyfluoride containing LiYF₄ nanocrystals is prepared.Glass-ceramic.Experiments have found that temperature control is especially important during crystallization,and different temperatures have a huge impact on crystallization behavior and spectral properties.In order to maximize the content of functional main crystal phase and reduce the impurity phase,the experiment has obtained the optimum heat treatment temperature of 540°C by XRD,TEM and emission spectroscopy.The material has a certain emission in green light emission?545nm emission?.The content of the third chapter is the preparation and spectral properties of Sm³⁺activated green fluorescent glass-ceramics.The controlled crystallization of precursor glass by melt-cooling method.The same can be used to dig out the interesting phenomenon of Sm³⁺luminescence.In the obtained material,76%high transparency can be maintained in the visible light region,and the 600 nm emission peak is multiplied.The sample emission is found in the red light region after CIE chromaticity coordinates.The fourth chapter is the preparation of Tb³⁺/Sm³⁺co-doped LiYF₄ glass ceramics.Through a large number of literatures,it is found that by adjusting the ion concentration ratio,the sample can be illuminated close to the standard white light.So we also tried and found many valuable results.Transmission electron micrographs?TEM?reflect the variation of grain size.The effects of different rare earths exist.We further study the energy transfer mechanism between Tb³⁺and Sm³⁺by measuring the fluorescence lifetime and Dexter's energy transfer theory.We obtain the dipole-dipole energy transfer mechanism between the two rare earth ions,and calculate the energy transfer efficiency of Tb³⁺?Sm³⁺according to the theory.The emission spectrum shows a combination of blue,green and orange-red emission,and the CIE chromaticity coordinates give the illuminating point in the white light region.The fifth chapter of the thesis is the summary and outlook,and expresses the main research content of the full text.Of course,I also reflected in detail the deficiencies in the experiment and set aside the future research.Keep up with the times.