Key Engineering Materials Vols. 336-338

Abstract: Y1.97-xTi0.03CdxO2S (0≤x≤0.06) phosphors with long afterglow were synthesized by solid-state reaction. The photoluminescence spectra, decay curves, thermoluminescnece spectra and Chromaticity coordinate curves were investigated. Results showed that the luminescence and afterglow intensity of Y1.97-xTi0.03CdxO2S (0≤x≤0.06) reduced gradually with increasing Cd2+ ion content while the shape and position of emission peak remain unchanged. The Chromaticity coordinate of present phosphor keeps at (0.5497,0.4415). Furthermore, based on the results of thermoluminescence curves of Ti, Cd single doped and co-doped Y2O2S phosphors, the doped Cd ion reduces the inherent trap depth of Ti single doped Y2O2S:Ti, and induces simultaneously a new trap level in Y2O2S:Ti,Cd phosphor. Thus, it was proposed that the introduced new structure defect by Cd2+ ions should be responsible for the reducing luminescence and afterglow property.

Abstract: Green-emitting Y3Al5O12: Tb phosphor materials have been widely studied because of their high luminescence efficiency and stability under the conditions of high irradiance with an electron beam. In this paper, Green-emitting phosphor of yttrium aluminum garnet (Y3Al5O12 or YAG) doped with Tb3+, Ce3+ and Gd3+ was synthesized by sol-gel method. By means of TG/DSC, XRD, and photoluminescence (PL) performance, the sintering condition and its influence on the powder’s emitting performance were studied. The experimental results showed that, Y2.8Tb0.12 Ce0.08-x GdxAl5O12 synthesized by sol-gel method was a kind of phosphor of good performance. When the value of x was set at 0.04, the best emitting performance was obtained. The Y3Al5O12: Tb, Ce, Gd particles had fine size, spherical shape, filled morphology, high crystallinity, and good brightness.

Abstract: To gain nanometer SrAl2O4:Eu,Dy phosphors, uniform fine precursors of Eu and Dy ion doping strontium aluminate were prepared by microemulsion technology. Using as-synthesized stuff, long afterglow phosphors SrAl2O4:Eu,Dy were obtained after sintered at 1200°C. TEM characterization showed the morphology of their grains is sphere-shaped with size less then 100nm. XRD analysis illuminated the crystal structure of SrAl2O4:Eu2+, Dy3+ phosphors is monoclinic. Fluorometry examination detected the peak in emitting spectrum is at 510nm, and at 310nm in exciting spectrum, which both have little blue shift contrasting to the same kind of phosphors synthesized by solid-state reaction method. Finally, the major parameters influencing the grain size of prepared phosphor powders were made a discussion.

Abstract: A new red afterglow phosphor Sr3Al2O6: Eu2+, Dy3+ was synthesized by solid-state reaction and sintered at 1150°C for 2h in reducing atmosphere. Red long lasting phosphorescence of the prepared materials is observed in the dark with naked eye after the removal of the excitation light. From the photoluminescence spectra, the broad emission band centered at 612 nm is confirmed. Excitation band chiefly lies in visible range and its maximum peak is at 473nm. Luminescence mechanism is studied.

Abstract: Spherical SiO2 particles have been successfully coated with SrSiO3:Eu3+ phosphor layers through a sol-gel process. The resulted core-shell phosphors were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), photoluminescence spectra as well as kinetic decays. The XRD results demonstrate that the SrSiO3:Eu3+ layers begin to crystallize on the SiO2 particles after annealing at 1000oC. The obtained core-shell phosphors have perfect spherical shape. The Eu3+ shows a strong photoluminescence (PL) (dominated by 5D0-7F2 red emission at 612 nm).

Abstract: A series of phosphors of M2MgSi2O7: Eu2+ (M=Ba,Sr,Ca) have been synthesized and studied. The excitation spectra measurement showed that the phosphors had absorption in long UV light, the excitation spectra of the phosphors consisted of two broad bands: one in the range from 280nm to 330 nm and the other from 360nm to 420 nm. The main excitation band centered at around 395nm was belong to 4f→5d transitions of Eu2+. Analysis of the spectra of Ce3+ and Tb3+ co-doped phosphor showed that energy transfer from Ce3+ to Tb3+ in Ba2MgSi2O7 under UV excitation was efficient.

Abstract: Sr2B5O9Cl:Eu phosphor with high efficient luminescent material was synthesized by solid-state reaction method in air. The result of X-ray diffraction showed that the pure Sr2B5O9Cl phase forms at 900°C. The emission spectrum of Sr2B5O9Cl:Eu under 254nm excitation contained two parts. One part was constituted by a strong peak located at 417nm due to the d→f transition of Eu2+ ion, and the other part contained five weak peaks between 580-660nm due to the 5D0→7FJ(J=1,2,3) of Eu3+ ion. The infrared spectrum revealed that both BO3 unites and BO4 unites coexisted in the resultant product. The Eu2+ was surrounded and protected from being oxidized by the BO4 unites. Both red and blue visible lights were observed under ultraviolet excitation as a result of the coexistence of Eu2+ ion and Eu3+ ion.

Abstract: Ce3+-doped SrGa2O4 was synthesized by citrate-gel with citric acid as chelate agent and sintered in a slightly reduced atmosphere of hydrogen and nitrogen mixture. It was found that the phosphor synthesized by citrate-gel can be sintered at relatively lower temperature. The luminescent properties of Ce3+-activated SrGa2O4 and the complex Sr(Ga-Al)2O4 were studied.

Abstract: The microstructure and surface micromorphology of ZnSe single crystals grown directly from zinc and selenium have been investigated using rotation orientation x-ray diffraction (RO-XRD), atomic force microscope (AFM) and field emission scanning electron microscope (FE-SEM). The ZnSe samples exhibit only the surface leaning to (111) singular face by the angle of 3.13°, which is the buildup of two-dimensional dendritic crystal layers. Numerous nuclei and cavities distribute unevenly across the crystal surface, governing the formation of growth layer, while the dendritic crystal layers develop rapidly by margining the smaller nuclei. The formation of these microstructure and micromorphology on the surface of ZnSe crystals depends on the surface supersaturation and the growth parameters.