Preparation And Luminescence Properties Of RE～(3+)(RE=Eu, Tb) And Na₂WO₄ Co-doped SiO₂ Materials

In the preparation of the precursor tetraethlortho silicate (TEOS), sodium tungstate, ethyl alcohol and HCl were mixed with europium ion or terbium ion, respectively, leading to a luminescent compound. DTA-TG, IR and XRD were used to characterized the structure of the materials, the result indicate that the materials with Eu3+ or Tb3+ were stable when annealed at 800℃and were in SiO₂ network structure, the doped concentration of rare earth and Na₂WO₄ were too low to influence the SiO₂ network structure. The materials were both in amorphous phase. The three-dimension fluorescence spectra, excitation and emission spectra were used to characterized the RE³⁺ and Na₂WO₄ co-doped SiO₂ luminescent materials, and the effect of WO42- on luminescence intensity of the materials have been discussed. The results indicate that in Eu3+ doped materials, the three-dimension fluorescence spectra confirm the emission wavelength of 612nm and excitation wavelength of 393nm, elementary estimate that WO42- sensitize rare earth Eu3+ because of the good energy transfer. When excited at 393nm, 5D0-7FJ (J=0-4) transitions were obtained in the emission spectra, which indicate vibrancy relaxation process for all the electrons to concentrate on 5D0 energy level. The comparison of Eu3+ doped only and Eu3+ and Na₂WO₄ co-doped materials testify that Na₂WO₄ transfer energy to Eu3+ ion efficiently that activated the transition of Eu3+ ion, especially the hypersensitive transition 5D0-7F2 sensitized more than 6 times; In Tb3+ doped materials, the three-dimension fluorescence spectra confirm the emission wavelength of 544nm and excitation wavelength of 230nm, when excited at 230nm. 5D4-7FJ(J=4,5,6) and 5D3-7FJ(J=4,5,6) transition were obtained in emission spectra. Tb3+ ions transfer energy to Na2WO4 that the intensity of Tb3+ depressed remarkably. The experiments indicate that the effect of Na2WO4 to different energy level is quite different. Because Na₂WO₄ has good energy transfer with 5D4-7F6 transition, induce the similar luminescence intensity of 5D4-7F5 and 5D4-7F6 transitions. In this paper, doping Na2WO4 has less influence with the emission position of Eu³⁺ or Tb³⁺ doped SiO₂ materials, but has great effect with the emission intensity. According to the three-dimension fluorescence spectra, excitation and emission spectra, the energy level diagram of (Eu³⁺or Tb³⁺) and Na2WO4 co-doped SiO₂ materials were designed to explain the energy transfer between metal ion W6+ and rare earth (Eu³⁺orTb3+). In order to investigate the influence factors of luminescence intensity, the pH value, the annealing time, annealing temperature, Na+ ion and tungstate concentration in Eu³⁺ or Tb3+ doped silicate materials were discussed, respectively.