Study On Synthesis And Fluorescence Properties Of Short Wave Emissing Rare Earth Ions Doped Fluorides

Inorganic solid-state fluorides have attracted great interest because of their uniquely structural properties and advantage in physics and chemistry as well as they being used as functional materials. The electronic properties, magnetic properties and optical properties of fluorides have been widely utilized. Most of fluorides and fluorides doped rare earth ions are synthesized by solid-state reactions at high temperature. As the reactions temperature is high, so it needs a complicated facility. Because it is corrosive set-up and pollution environment of fluorides, the oxygenic content in structure of fluorides synthesized by solid-state reactions at high temperature is high especially, so fluorides have been limited the application in the materials chemistry. Therefore, how to control the oxygenic content in fluorides and how to search the synthesis methods of fluorides with lower oxygenic content, is an important topic in region of fluorides chemistry.Complex fluorides of KMgF3, KZnF3 and fluorides phosphor of KMgF3:Eu, KMgF3: Ce, KMgF3:Eu, Ce, KZnF3:Ce and KZnF3:Tb through solvothermal process have been synthesized firstly. All products are characterized by X-ray powder diffraction (XRD), environment scanning electron microscopy (ESEM) and XPS analysis. The optical measurements are performed at room temperature using fluorescence spectrometer. The XRD patterns show that all the products are single phase, the ESEM shows the products have regular morphology and XPS analysis shows that there are not O—F bonds and F—M—O (M= K. Mg. and Zn) bonds in the structure of products synthesized by solvothermal process. These indicate that the oxygenic content is lower in the products. This is the ultimate difference between the complex fluorides synthesized by solvothermal routes and solid-state reaction at high temperature.Spectral properties have been made a detailed study. There is a broadband excitation in Ce or Eu-doped KMgF3. which the maximum peak all appears at about 250 nm. But in Ce-doped KZnF3, there are two emission peaks in the excitation spectrum, located at 246 and 263 nm, respectively. In the emission spectrum of the KMgF3,:Eu phosphor, there is only a sharp peak emission located at 360 nm, which arisen from f→f (6P7/2→8S7/2) transition of Eu2+. the broad emission bands should appear at 420 nm, which arisen from Eu2+←O2- could not be observed. The emission spectrum of Ce-doped KMgF3 or KZnF3 appears as a broad range with the maximum center located at 306 nm and 330 nm. respectively. In co-doped with Ce3+ and Eu2+ system of KMgF3, the strong emission band of the Ce3+ could be observed due to absorbing the exciting energy competitively between the Eu2+ and Ce3+, while the emission peak of the Eu2+ can only be observed due to energy transfer from Ce3+ to Eu2+ appearing in the KMgF3:Eu2+, Ce3+ polycrystalline powder prepared by solid state reaction at a high temperature. In addition, the mechanism of energy transfer is discussed in co-doped fluoride of KMgF3:Eu2+, Ce3+ synthesized by solvothermal way. In this thesis, KMgF3, KMgF3:Ce. KMgF3:Eu. KMgF3:Ce. Eu. KZnF3, KZnF3:Ce, KZnF3:Ce, Tb nanoparticles and BaLiF3:Ce nanocrystals are prepared in water/cetyltrimethylammonium (CTAB)/2-octanol microemulsions. All products are characterized by XRD. ESEM and XPS analysis. The optical measurements are performed at room temperature using fluorescence spectrometer. The XRD patterns show that all the products are single phase. ESEM shows that the even size distribution of the nanoparticles with cubic shapes. XPS analysis shows that there are not O—F bonds and F—M—O (M=Li. Ba) bonds in the structure of products synthesized by solvothermal process. These indicate that the oxygenic content is lower in the products.Photoluminescence characteristics of the rare earth ions doped complex fluoride nanoparticles through microemulsion are investigated and compared with that of the polycrystalline products prepared by solid state reaction at a high temperature. In the KMgF3 nanoparticles. similarly, there is only a sharp peak emission located at 360 nm, which arisen from f→f transition of Eu2+ in the emission spectrum of the KMgF3:Eu nanoparticles, the broad emission bands should appear at 420 nm, which arisen from Eu2+←O2- was not be observed. The excitation peaks in the excitation spectrum of the KMgF3:Eu nanoparticles are also blue shift very intensively. The emission band of the Ce3+ could only be observed due to absorbing the exciting energy competitively between the Eu2+ and Ce3+ in co-doped system of KMgF3 nanoparticles. while the emission peak of the Eu2+ can only be observed due to energy transfer from Ce3+ to Eu2+ appearing in the KMgF3:Eu2+, Ce3+ polycrystalline powder synthesized by high temperature reaction. The emission peak of the KZnF3:Ce3+ nanoparticles shows obvious red shift than that of polycrystalline powder. In the Ce3+ and Tb3+ co-doped system of KZnF3 nanoparticles. the emission band of Ce3+ even can hardly be observed and the luminescence intensity of Tb3+ is increased much than that Tb-doped KZnF3 singly. This shows that the emission of the Tb3+ is sensitized by Ce3+. The experimental results indicates there is an effective energy transfer from Ce3+ to Tb3+ in KZnF3 nanoparticles. The emission peak of the BaLiF3:Ce3+ nanoparticles synthesized by microemulsion shows obvious blue shift than that of BaLiF3: Ce3+ synthesized by high temperature reaction. And full width at half maximum (FWHM) of emission band was broaden. The reason why blue shift of the emission peaks can also contribute to the matrix nanoparticles structure and nanometer dimension effect.Eu3+-doped YF3 is prepared by solvothermal and hydrothermal process for the first time. X-ray diffraction (XRD) patterns identifie the formation of YF3 phase without detectable impurity. Environment scanning electron microscopy (ESEM) image shows the even size distribution of the samples with cubic morphology. The excitation and emission spectra of the rare earth ions doped YF3 through solvothermal and hydrothermal process are investigated by fluorescence spectrophotometer.In a word, the marked characteristics of the complex fluorides synthesized by solvothermal routes and fluorides nanoparticles prepared by microemulsion as microreactors are lower oxygenic content in the structure of products. These results can establish credible foundation for further studying the potential applications of fluorides doped rare earth ions in short wave laser materials.