Synthesis And Luminescent Properties Of Several Rare Earth Base Optical Materials

In this thesis, firstly, the core-shell structure of a kind of up-conversion phosphor material NaYF4 had been synthesized by coating. Using the inorganic silica sphere as cores resolved the problem of preparing directly the spherical nanocomposites. A simple sol-gel process has been developed to coat NaYF4:Yb3+/Er3+(or Yb3+/Tm3+) phosphor layers on monodisperse spherical SiO2 particles. Compared with other preparation methods, sol-gel method has the advantages as follows:simple procedure, easy operation, nocomplic-ated instruments. Secondly, spherical Pr3+ doped CaTiO3 phosphor particles were fabricated through a two-step spray pyrolysis process, using citric acid and polyethylene glycol (PEG) as additives. Finally, Rare earth ions (Eu3+, Sm3+, Dy3+) doped CaWO4 nanoparticles and rare earth ions (Eu3+, Tb3+, Dy3+) doped SrMoO4 nanoparticles were synthesized via a facile solvothermal process.The structure, morphology, textural and optical properties were well characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), and photoluminescence spectra (PL), respectively.The results show that the core-shell structure phosphors NaYF4:Yb,Er/Tm@Si02 and NaYF4:Yb,Er/Tm@MCM-41 without annealing showed a cubic spinel structure of a-NaYF4. After being annealed above 400℃, the coexistence of a cubic and hexagonal structure of NaYF4 was obtained. The obtained core-shell structured phosphors maintain spherical morphology, submicrometer size and narrow size distribution, which have an average diameter of 300nm. Furthermore, uniform, smooth and crack-free phosphor films with thickness of 30nm were obtained. TEM results showed that the lattice fringes obvious and the distance between the adjacent lines are well consistent with the d value of (101) plane of NaYF4. The intense up-conversion emission was observed from the nanocrystals under excitation at 980nm.The as-prepared CaTiO3:Pr3+ phosphors are spherical with submicron particle size. The particles show a strong red emission corresponding to 1D2-3H4 (612 nm) of Pr3+ under the ultraviolet excitation (325 nm) and low voltage electron beams (1-5 kV). Furthermore, the morphology, PL and CL intensities of the CaTiO3:Pr3+ phosphors can be tuned by altering the concentration of PEG, annealing temperature, and acceleration voltage. These phosphors show potential applications in the field of field emission displays (FEDs).The XRD results reveal that all the doped samples are well assigned to the scheelite structure of the CaWO4 phase. The as-made phosphors consist of well-dispersed nanocrystals with relatively narrow size distribution. Upon excitation by ultraviolet radiation or low-voltage electron beams, the CaWO4:Eu3+ phosphors show the characteristic 5D0-7F1-3 emission lines of Eu3+, the CaWO4:Sm3+phosphors exhibit the characteristic 4G5/2-6H5/2-9/2 emission lines of Sm3+, and the CaWO4:Dy3+ phosphors demonstrate the characteristic 4F9/2-6H13/2-15/2 emission lines of Dy3+, respectively. These phosphors show potential applications in the fields of fluorescent lamps, field emission displays and biological labeling.Rare-earth ions(Eu3+,Tb3+ and Dy3+) doped SrMoO4 particles with uniform morphologies were successfully prepared through a facile solvothermal process. The XRD results reveal that all the doped samples are of high purity and crystallinity. It has been shown that the as-synthesized SrMoO4:Ln (Ln=Eu3+,Tb3+ and Dy3+)samples show respective uniform peanut-like and oval morphologies with narrow size distribution. Upon excitation by ultraviolet radiation, the SrMoO4:Eu3+ phosphors show the characteristic 5D0-7F1-3 emission lines of Eu3+, while the SrMoO4:Tb3+ phosphors exhibit the characteristic 5D4-7F3-6 emission lines of Tb3+, and SrMoO4:Dy3+ phosphors exhibit the characteristic 4F9/2-6H13/2-15/2 emission lines of Dy3+. These phosphors exhibit potential applications in the fields of fluorescent lamps and light emitting diodes (LEDs).