Preparation And Luminescence Properties Of Rare-earth Ions Doped Luminescence Materials By A Sol-gel Process

The thesis describes the related theories of luminescent materials, systemically introduces luminescent theories of rare-earth ions doped fluorescence materials, gives an overview of species, characteristic and the recent advances on this materials, summarize the advantages and disadvantages of various approaches and the recent achievements on preparations. The red-emitting BaMg2Si2O7:Eu2+, Mn2+ phosphors, novel blue-green-emitting CaYAl3O7:Ce3+, Tb3+ phosphors and up-conversion luminescence phosphors Y2O3:Er3+, Yb3+ had been synthesized via a simple sol-gel method. Thermogravimetry-differential thermal analysis (TG-DTA), X-ray diffraction (XRD), scanning electronic microscope (SEM) and photoluminescence spectroscopy (PL) were used to investigate the crystal structure and luminescence property of the products.BaMg2Si2O7:Eu2+, Mn2+ phosphors have been prepared by a sol-gel procedure. XRD results showed that rare-earth ions doping facilitate preparing pure phase BaMg2Si2O7 without any impurities. Under excitation at 350 nm in the ultraviolet(UV) region, the red emission at 670 nm corresponding to 4T1(4G)→6A1(6S) transition of Mn2+ ions were observed due to an efficient energy transfer from the Eu2+ ions to Mn2+ ions, and with the increase of the sintered temperature, the red emission increased first then decresed.Blue-green-emitting CaYAl3O7:Ce3+, Tb3+ phosphors have been synthesized by a citric acid assisted with sol-gel method. Under single-wavelength excitation at 360nm in the UV region, PL spectra showed the phosphors consisted of a brighter and broader violet-blue emission (415nm) from the Ce3+ and some sharp green emission (495nm,544nm,591nm) from the Tb3+ ions. The reaction temperature and atmosphere had an essential influence on samples' luminescence intensity. The strongest emission can be observed in the Ca0.78YAl3O7:0.03Ce3+,0.19Tb3+ phosphors prepared for 6hr at 900℃in reducing atmosphere.The upconversion luminescence materials Y2O3:Er3+ and Y2O3:Er3+, Yb3+ had been prepared via citric acid assisted with sol-gel method. The possible reaction mechanism had been discussed. The dependence of the intensity of upconversion emissions upon the excitation power of the 980 nm LD suggested that three-photon absorption processes in Y2O3:Er3+ and two-photon absorption processes in Y2O3:Er3+, Yb3+ are involved in the green and red up-conversion luminescence.