Browsing by Subject "PERSISTENT LUMINESCENCE"

Now showing 1 - 4 of 4
  • No Thumbnail Available
    Item
    Preparation and cathodoluminescence characteristics of rare earth activated BaAl2O4 phosphors
    (PERGAMON-ELSEVIER SCIENCE LTD) Benourdja, S; Kaynar, ÜH; Ayvacikli, M; Karabulut, Y; Guinea, JG; Canimoglu, A; Chahed, L; Can, N
    Undoped and Pr, Sm and Tb activated BaAl2O4 phosphors have been synthesized by solid state reaction method and combustion method. The structure and morphological observation of the phosphor samples were monitored by X-ray powder diffraction (XRD) and environmental scanning electron microscope (ESEM) coupled to an energy dispersive X-ray spectrometer (EDS). The all diffraction peaks are well assigned to standard data card (PDF#17-306). Emission properties of the samples were explored using light emission induced by an electron beam (i.e cathodoluminescence, CL) at room temperature (RT). Undoped BaAl2O4 sample exhibits a broad defect emission from 300 to 500 nm from the aluminate defect centres. CL spectra recorded at room temperature display that the as-prepared BaAl2O4:Ln (Ln = Pr, Sm and Tb) phosphors exhibit different luminescence colors coming from different rare earth activator ions. The transition (4)G(5/2) -> H-6(7/2) located at 606 and 610 nm for Sm3+ can occur as hypersensitive transition having the selection rule Delta J = +/- 1. For the Tb3+ doped samples, they exhibit D-5(4) green line emissions. The proposed luminescent mechanisms of all doped rare earth ions are also discussed.
  • No Thumbnail Available
    Item
    Structural and spectroscopic properties of LaAlBO3 doped with Eu3+ ions
    (PERGAMON-ELSEVIER SCIENCE LTD) Halefoglu, YZ; Oglakci, M; Yuksel, M; Canimoglu, A; Topaksu, M; Can, N
    In this study, we performed X-ray diffraction (XRD) and environmental scanning electron microscope (ESEM) techniques to examine the structure and morphological observation of the samples and thermoluminescence (TL) experiments to extract the trapping parameters and dosimetric properties of LaAlBO3 phosphors doped with Eu at various doping concentrations. Diffraction patterns of obtained sample were well consistent JCPDS card No 98-009-7945, indicating the formation of pure phase. The TL kinetic parameters were estimated by CGCD software. TL glow curves of LaAlBO3:Eu3+ consist of 12 trap levels and exhibited dominantly first order kinetics. Photoluminescence (PL) emission was observed in the range 400-800 nm for LaAlBO3 phosphor doped with Eu3+. The dominant emission of Eu3+ corresponding to the electric dipole transition D-5(0) -> F-7(2) is located at 616 nm. The sharp emission properties exhibited demonstrate that the LaAlBO3 is a suitable host for rare-earth ion doped phosphor material. It is observed that for the variable concentration of Eu3+ on PL studies, the PL intensity augments with increase in the dopant concentration and the concentration quenching was found after 1 mass% of Eu3+. The PL experimental results reveal that LaAlBO3:Eu3+ phosphor as an red emitting phosphor may be promising luminescence materials for the optoelectronic applications.
  • No Thumbnail Available
    Item
    Structural and optical properties of SrAl2O4: Eu2+/Dy3+ phosphors synthesized by flame spray pyrolysis technique
    (ELSEVIER) Gültekin, S; Yildirim, S; Yilmaz, O; Keskin, IÇ; Kati, MI; Çelik, E
    In this study Sr0.985Al2O4:0.005Eu(2+)/0.01Dy(3+) luminescent materials with long afterglow and high intensity were synthesized by flame spray pyrolysis (FSP) method for the first time. Precursor solution was divided into two separate part. One of the parts was used FSP process, the other one was dried to simulate sol- gel process. Thermal properties and organic content of FSP derived particles and dried gel were compared using DTA-TG and FTIR devices. FSP derived particles were sintered in argon medium at 1200 degrees C. Phase and elemental analysis of the final phosphors were carried out by X-Ray Diffraction (XRD) and X-Ray Photo electron Spectroscopy (XPS) measurements. Scanning electron microscopy (SEM) images were obtained to observe particle morphology. Optical properties of phosphor were determined by Photoluminescence (PL), thermoluminescence (TL) and radioluminescence (RL) measurements. The emission spectra of Sr0.985Al2O4: 0.005Eu(2+)/0.01Dy(3+) were composed by a green band at 525 nm at room temperature when it was excited by 350 nm light, assigned to anomalous luminescence originated by Eu2+ and Dy3+ in the host lattice. There were estimated peaks at around 90, 130, 170 and 200 degrees C under the main glow curve in the sample irradiated by X- ray and He- Ne laser (lambda(exc) = 632 nm). RL spectrum of Sr0.985Al2O4 : 0.005Eu(2+)/0.01Dy(3+) powders have four distinct emission peaks at around 527 nm, 576 nm, 667 nm, 753; nm and a comparatively weak emission band at about 846 nm.
  • No Thumbnail Available
    Item
    Thermoluminescence glow curve analysis and kinetic parameters of Dy-doped BaSi2O5 phosphor
    (ELSEVIER) Alajlani, Y; Can, N
    In this paper, Dy3+ incorporated BaSi2O5 phosphors were synthesized by gel combustion method and characterized by X-ray diffraction (XRD). The effects of various heating rates on thermoluminescence (TL) kinetics and glow peak temperatures of Dy3+ incorporated BaSi2O5 phosphors exposed to beta irradiation at room temperature were investigated. The glow curves of the phosphor exposed to beta-irradiation (0.1-100 Gy) consist of four main peaks located at 87,130, 271, and 327 degrees C and exhibit a good linearity between 0.1 and 100 Gy. Three experimental techniques including variable heating rate (VHR), repeated initial rise (RIR), peak shape (PS) and computerized glow curve deconvolution (CGCD) were employed to determine TL kinetic parameters. Our findings indicate that the TL glow peaks of the phosphor obey first-order kinetics. Analysis of the main dosimetric peaks through the techniques mentioned above indicates that activation energies (E) and pre-exponential factor (s) are in the range of 0.80-1.50 eV and 1.15 x 10(8)-3.28 x 10(13) s(-1). Additionally, it is found that the temperature of the glow peaks shifts toward the higher temperatures and the TL intensity smoothly decreases as the heating rate increases. The effect on the TL intensities and glow peak temperatures of the heating rate is discussed in terms of thermal quenching. (C) 2020 Chinese Society of Rare Earths. Published by Elsevier B.V. All rights reserved.