Rare Earth Luminescent Material Yag And Nayf < Sub > 4 < / Sub > Preparation And Performance Of The Research

New light-emitting materials have attracted considerable interests in the last years.The rare earth doped light-emitting materials have the advantages of photochemicalstability, long life span of fluorescence, high yield of quantum, narrow opticalspectrum and large Stokes shift etc. due to its unique electronic structure. Amongthem, the tombarthite ions mixed with light-emitting materials have long been thefocus of the study. Eu³⁺, Er³⁺are the most commonly used as the activator in red andgreen phosphors. This paper aims at the study of luminous materials doped with Eu³⁺and Er³⁺. The main conclusions are summarized as follows.The Er³⁺-doped Y3Al5O12upconversional luminescence agents (YAG: Er³⁺) wereprepared via self-propagating-high-temperature route using yttrium oxide, aluminumnitrate, erbium oxide as the raw materials. The as-formed powders were fine particleswith high crystallinity and uniform size distribution, which were characterized byX-ray diffraction （XRD）, scanning electron microscopy （SEM）, transmission electronmicroscopy （TEM） and fluorescence spectrometer, etc. The particles were intensifiedas the single crystal with the size of about100-200nm. The fluorescence spectra ofYAG doped with different erbium concentration was investigated. The excitation peakand the emission peak wavelength was488nm and540nm, respectively. The dopingamount had an important effect on the fluorescence properties of YAG: Er³⁺sample.The intensities of excitation and emission peaks increased with the increasing ofdoping amount. Furthermore, the TiO₂（P25） photocatalyst was coupled with the YAG:Er³⁺up-conversion materials. Interestingly, it was revealed that the YAG:Er³⁺/TiO₂composite processed obvious visible-light response activity through the photocatalyticdegradation reaction of methyl orange. The degradation efficiency of YAG: Er³⁺/TiO₂was much higher than that of TiO₂. The results showed that the up-conversionmaterials can improve the catalytic ability of the TiO₂photocatalyst.Furthermore, the NaYF₄:Eu³⁺luminescent materials were prepared byhydrothermal method using EDTA as the complexing agent. The ratio of NaF and rare earth ions, pH, polymer modification and heating treatment on the surfacemorphology, structure and. Fluorescence properties of the sample were systematicallydiscussed. The results showed that the tetragonal spherical particles and hexagonalmicronprisms NaYF₄:Eu³⁺could be synthesized by controlling the ratio of NaF and Yions. And the hexagonal micronprisms NaYF₄:Eu³⁺exhibited stronger fluorescenceproperties than the tetragonal spherical particles. Under the excitation by the light at395nm, the NaYF₄:Eu³⁺exhibited orange （588nm） and red （614nm） emissions, whichare assigned to the⁵D₀â†'⁷F₂and⁵D₀â†'⁷F₁transition, respectively.Additionally, the NaYF₄: Eu³⁺hexagonal microprisms synthesized byhydrothermal method were further experienced by heating treatment process. Theresults showed that the annealing temperature had little effect on the crystal structureof the NaYF₄: Eu³⁺, but a significant effect on the grain shape and morphology. Afterannealing, it still remained the hexagonal phase structure. Also it can improve theEu³⁺doped state in the matrix and fluorescence properties. The sample calcined at300℃still remained stable hexagonal prism shape, and got the best fluorescenceperformance. Finally, during the hydrothermal synthesis processes, the morphologyand fluorescence properties can be adjusted by controlling the pH of the reaction, orpolymer PEG6000added in the reaction solution.