Synthesis And Characterization Of Several Oxide, Phosphate And Sulfide Phosphors

Phosphor materials have been widely used in luminescence, optical fibers and amplifiers, fluorescence labeling etc. Oxide, phosphate and sulfide phosphors all have unique advantages in improving luminescence properties. In the last decade, significant interest in investigation of oxide, phosphate and sulfide matrix phosphors had been emerged due to the possibilities for advanced applications, especially for the field emission display (FED), the plasma display panels (PDP), the cathode ray tubes (CRT) and various flat panel displays. So, more and more attention has been paid to improve currently used phosphors or explore novel efficient phosphors. It was also found that some rare earth ions and transition metal ions as activators, even in very small quantities, such as Sm3+, Eu3+. In this thesis, we have successfully synthesized Y2O3:Eu3+, Tb3+ white emission phosphors, LiSrxBa1-xPO4:RE3+(RE=Sm3+, Eu3+) f-f transition phosphors and SrY2S4:Cu+/Tb3+, Y2O2S:Cu phosphors, on the basis of studying of luminescent properties of these phosphors, we make a comprehensive study on luminescence mechanism. The main contents and the important results are listed as following:1. Y2O3:Eu3+, Tb3+ phosphors with white emission were prepared with different doping concentration of Eu3+ and Tb3+ ions and synthesizing temperatures from 750 to 950℃by the co-precipitation method. The above phosphors were characterized by X-ray diffraction (XRD) and photoluminescence (PL) spectroscopy. The results of XRD indicated that the crystallinity of the synthesized samples increased with enhancing the firing temperature. The photoluminescence spectra indicated the Eu3+ and Tb3+ co-doped Y2O3 phosphors showed five main emission peaks: three at 590,611 and 629 nm originated from Eu3+ and two at 481 and 541 nm originated from Tb3+, under excitation of 250-320 nm irradiation. The white light luminescence color could be changed by varying the excitation wavelength. Different concentrations of Eu3+and Tb3+ ions were induced into the Y2O3 lattice and the energy transfer from Tb3+→Eu3+ ions in these phosphors was found. The Commission International de 1'Eclairage (CIE) chromaticity showed that the Y2O3:Eu3+, Tb3+ phosphors could obtain an intense white emission.2. Rare-earth ions (Sm3+ or Eu3+) doped LiSrxBa1-xPO4 (x=0,0.2,0.4,0.6,0.8,1.0) f-f transition phosphor powders were prepared by a high temperature solid state reaction. The resulted phosphors were characterized by X-ray diffraction (XRD) and photoluminescence (PL) spectroscopy. The results of XRD indicated that the phase structure of the sample changed from LiBaPO4 to LiSrPO4 when x changed from 0 to 1.0. The excitation spectra indicated that only direct excitation of rare earth ions (Sm3+ or Eu3+) could be observed. The doped rare earth ions showed their characteristic emission in LiSrxBa1-xPO4, i.e., Eu3+5D0-7FJ (J=0,1,2,3,4), Sm3+ 4G5/2→6HJ(J=5/2,7/2,9/2,11/2), respectively. The dependence of the emission intensities of the LiSrxBa1-xPO4:Sm3+ and LiSrxBa1-xPO4:Eu3+ phosphors on the x value and Ln3+(Ln3+=Sm3+, Eu3+) concentration were also investigated.3. SrY2S4:Cu+/Tb3+ and Y2O2S:Cu phosphors have been synthesized via the conventional solid-state reaction, by H2(5%)-N2(95%) gas or a double-crucible method. The X-ray diffraction patterns of the phosphors demonstrated SrY2S4 and Y2O2S phase. The phosphor SrY2S4:Cu+ had a strong broad absorption band peak at 267 nm, range from 250 to 290 nm, and it had a green emission; SrY2S4:Tb3+ phosphor had a charge transfer band ranged from 250 to 330 nm, also a Tb3+characteristic emission; Y2O2S:Cu had 1.0-3.0 um diameter of spherical form. Excitation and emission spectra results showed that Y2O2S:Cu could be efficiently excited by ultraviolet light from 230 to 285 nm. More natural white emission had been observed at 265 nm excitation. The photoluminescence results indicated that these phosphors could emit appropriate sharp emissions in the visible region, the Gd3+ and Ca2+ ions doping may change the trap depth in the Y2O2S matrix and improve the luminescent properties. CIE coordinate of Cu-activated Y2O2S phosphors was X=0.311, Y=0.334 at the concentration of Cu+ is 0.3%.