Study On The Synthesis And Upconversion Luminescence Properties Of Rare Earth Codoped SrYbF₅Material

During the past decades, upconversion luminescence of rare earth (RE) ions doped material hasbeen received much interest due to their wide potential applications in color display, biomedicaldiagnostics, high density optical date recording and reading, and so on. Of the excited works,considerable research has been focused on searching for the white light-emitting materials since whitelight find potential uses and applications in many fields, such as three dimensional displays, lowenergy light sources and back light. Although some work on white upconversion emission fromTm3+/Er3+/Yb3+or Tm3+/Ho3+/Yb3+doped materials has been done, the host materials used forupconversion white light emissions are still very limited and need more exploration. It is essential toseek new materials capable of multicolor upconversion and study their upconversion mechanism. Inthis thesis, we take SrYbF5as the research object. A series of rare earth doped SrYbF5nanosheets andphosphors were prepared through hydrothermal method and coprecipitation method, respectively. Thestructural and optical properties of the prepared samples were studied using X-ray diffraction (XRD),scanning electron microscopy (SEM), High Resolution Transmission Electron Microscopy (HRTEM),energy dispersive X-ray spectroscopy (EDXS) and luminescence spectra. The main results andconclusions of this dissertation are outlined as follows:1. A brief introduction was given in chapter1to the classification and their applications indifferent fields of rare earth doped upconversion materials. The common synthesis methods, includinghigh temperature solid state method, sol-gel method, hydrothermal method, microwave radiationmethod and coprecipitation method are specifically introduced, in which hydrothermal method andcoprecipitation method are taken in our experiment to prepare SrYbF5samples.2. Er3+/Tm3+co-doped SrYbF5nanosheets were synthesized by hydrothermal method at200℃inthe presence of Poly-vinylpyrrolidone (PVP) as surfactant. The resulting samples were characterizedby XRD, SEM, HRTEM, EDXS and luminescence spectra. When only Er3+ions are doped, the redup-conversion luminescence was observed under a980nm excitation. When Er3+and Tm3+areco-doped into SrYbF5nanosheets, the spectra exhibit seven distinct bands centered at474nm,522nm,543nm,654nm,679nm,699nm and803nm. With the increase of Tm3+concentration, theupconversion emissions of Er3+ions are increased first and then decreased.3. Tm3+/Ho3+co-doped SrYbF5phosphors were synthesized by coprecipitation method. Thestructure and white upconversion emission were studied using XRD and luminescence spectra. Theinfluence of Ho3+concentration and pump power on white UC luminescence of the SrYbF5phosphors was analyzed. When the pump power was10.6mW, bright white light was produced throughsynthesis of red, green, blue upconversion luminescence in1%Tm3+/0.5%Ho3+codoped SrYbF5. Thecalculated CIE color coordinates (0.333,0.334) are very close to the standard white light (0.333,0.333) coordinates.