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1.
O. Annalakshmi U. Madhusoodanan J. Sridevi B. Venkatraman G. Amarendra 《辐射效应与固体损伤》2013,168(7):636-645
Magnesium tetra borate (MTB) doped with rare earths (REs) was prepared by the solid state sintering technique. Among the different RE dopants studied in this phosphor, gadolinium-doped phosphors resulted in a dosimetric peak at a relatively higher temperature. The thermoluminescence (TL) emission spectra of RE-doped MTB showed characteristic RE 3+ emissions. Electron paramagnetic resonance measurements were carried out in these phosphors to identify the defect centers formed during gamma irradiation and to establish a mechanism for the TL process. Signals corresponding to (BO 3)2?, O v? were seen upon irradiation which vanished on annealing at 250 °C, showing the role of these centers in the TL process. The thermal activation energies calculated based on the decay of these signals matched well with those calculated on the basis of the usual conventional method showing the validity of the mechanism of TL. 相似文献
2.
Thermoluminescence excitation spectroscopy: A versatile technique to study persistent luminescence phosphors 总被引:1,自引:0,他引:1
Adrie J.J. Bos Ronald M. van Duijvenvoorde Winicjusz Drozdowski 《Journal of luminescence》2011,131(7):1465-1471
A versatile new facility to study photoionization processes in impurity doped compounds is presented. In this new facility monochromatic light is coupled to a thermoluminescence reader, enabling a fully automated recording of glow curves as a function of photon excitation wavelength. It provides detailed information on the mechanism of trap filling preceding persistent luminescence. The technique is first demonstrated with a study on Lu2SiO5:Ce3+ and then applied to commercial modern day double lanthanide doped SrAl2O4:Eu2+,Dy3+, Sr4Al14O25:Eu2+,Dy3+, CaAl2O4:Eu2+,Nd3+; and to the classical ZnS:Cu+ persistent luminescence phosphors. The presented data provide new insight into the mechanism of persistent luminescence. 相似文献
3.
Photoluminescent phosphors CaGa2S4: Eu2+, RE3+ (RE3+ including all rare earth ions except for Sc3+, Pm3+, Eu3+ and Lu3+) were prepared by sintering at high temperature in a reductive atmosphere, and their luminescent properties were studied intensively. The influences of co-doping rare earth ions on their luminescent properties were also investigated. No remarkable differences were found from excitation spectra of co-doped phosphors CaGa2S4: Eu2+, RE3+ in contrast with that of phosphor CaGa2S4: Eu2+, but there were a few differences in emission spectra of Ce3+, Pr3+ or Ho3+ co-doped phosphors. Phosphors CaGa2S4: Eu2+, RE3+ (RE=Ce, Pr, Gd, Tb, Ho and Y) had persistent afterglow, and very short afterglow was shown for Nd3+ or Er3+ co-doped phosphors, but no long afterglow appeared when auxiliary activator was La3+, Sm3+, Dy3+, Tm3+ or Yb3+. Among the phosphors with long-lasting phosphorescence, in our experiments, CaGa2S4: Eu2+, Ho3+ had the longest and the highest brightness long yellow afterglow. Thermo-luminescence of all co-doped phosphors was measured to find the answer of different influences from different rare earth auxiliary activators. 相似文献
4.
Hemam Jenee Devi Wairokpam Rameshwor Singh Romeo Singh Loitongbam 《Journal of fluorescence》2016,26(3):875-889
Rare earth elements (RE = Eu3+& Dy3+)and Bi3+ doped Y2O3 nanoparticles were synthesized by urea hydrolysis method in ethylene glycol, which acts as reaction medium as well as a capping agent, at a low temperature of 140 °C,followed by calcination of the obtained product. Transmission electron microscope (TEM) images reveals that ovoid shaped Y2O3 nanoparticles of around 22–24 nm size range were obtained in this method. The respective RE and Bi3+ doped Y2O3 precursor nanoparticles when heated at 600 and 750 °C, retains the same shape as that of the as-synthesized Y2O3 precursor samples. From EDAX spectra, the incorporation of RE ions into the host has been studied. XRD pattern reveals the crystalline nature of the heated nanoparticles and indicate the absence of any impurity phase other than cubic Y2O3.However, the as-synthesized nanoparticles were highly amorphous without the presence of any sharp XRD peaks. Photoluminescence study suggests that the synthesized samples could be used as red (Eu3+), yellow (Dy3+), blue and green (Bi3+)emitting phosphors. 相似文献
5.
The thermo-luminescence (TL) of rare earth ions RE3+ (RE=Ln, excluding Pm, Eu and Lu) co-doped phosphors CaGa2S4:Eu2+, RE3+ was studied between room temperature and 300 °C, and 3D thermo-luminescence of the phosphors were measured from room temperature to 400 °C. The basic material CaGa2S4:Eu2+, showed at least two bands in the TL glow curve. Changing the auxiliary activator RE3+ (rare earth ion), intensities and the positions of the TL glow curve peaks were affected significantly. For the phosphors with long afterglow, auxiliary activator such as Ce3+, Pr3+, Gd3+, Tb3+, Ho3+, or Y3+ created some new defects in these compounds at lower trap levels and enhanced their TL intensities. The Nd3+ or Er3+ auxiliary activator only enhanced TL intensities to a low extent, so these two phosphors have short persistent luminescence at room temperature. TL intensities of La3+, Sm3+, Tm3+ or Yb3+ co-doped phosphors were suppressed greatly and no afterglow was shown. The relationship between auxiliary activators and corresponding thermo-luminescence curves of phosphors CaGa2S4:Eu2+, RE3+ are discussed in detail. According to our results, suitable activation energy and enough high corresponding trap density are necessary for the phosphor with long afterglow. 相似文献
6.
This paper reports the preparation of long persistent Sr2Al2SiO7:Eu2+ and Sr2Al2SiO7:Eu2+, Dy3+ phosphors and the comparison of their photoluminescent properties. The silicate phosphors prepared by solid-state reaction routine showed a broad blue emission peaking at 484 nm when activated by UV illumination. Such a bluish-green emission can be attributed to the intrinsic 4f-5d transitions of Eu2+. After the UV source was switched off, long persistent phosphorescence could be observed by naked eyes for both samples in darkness. Afterglow measurements revealed that Eu/Dy codoped phosphor possesses better afterglow properties than the Eu single doped one, since the maximum lifetime (τmax=99 s) of the photons calculated from the decay profile is much larger than that of the Eu single doped phosphor (τmax=82 s). TSL results suggested that the difference in afterglow properties was caused by the difference in the electron traps within the crystal lattice. For Eu/Dy codoped phosphor, the doping of Dy ions produced electron traps with trap depth of 0.52 eV, which is suitable and therefore leads to good persistence. However, in the case of Eu single doped phosphor, the trap depth is 0.88 eV, which is really too deep an energy barrier to overcome, and therefore a poor persistence was observed in the experiment. 相似文献
7.
This paper reports the structural and optical properties of rare earth doped and codoped yttrium oxide nanophosphors. Dysprosium (Dy3+) and Terbium (Tb3+) doped and codoped yttrium oxide (Y2O3) phosphors were prepared by combustion synthesis method and subsequently annealed to high temperature to eliminate the hydroxyl group (?OH) and to get more crystallinity. The formation of compounds was confirmed by the X-ray diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR). The diffuse reflectance spectra (DRS) of doped and codoped Y2O3 powder phosphors were measured and it is observed that the absorption edge of the doped samples is shifted towards blue region with respect to undoped sample. The bandgap of the prepared samples were evaluated with the help of Kubelka-Munk function using Diffuse Reflectance Spectra (DRS) and an increase in bandgap was observed with the decrease in crystallite size. A strong characteristics emission from Tb3+ and Dy3+ ions was identified and the influence of doping concentration and annealing temperature on photoluminescence properties was systematically studied. Transfer of energy was observed in dysprosium–terbium codoped Y2O3 nanophosphor at room temperature from Dy3+ ions toTb3+ ions. 相似文献
8.
Chengkang Chang Wen Li Xiaojun Huang Zhiyu Wang Xi Chen Xi Qian Rui Guo Yuelei Ding Dali Mao 《Journal of luminescence》2010,130(3):347-350
This paper reports the photoluminescence and afterglow behavior of Eu2+ and Eu3+ in Sr3Al2O6 matrix co-doped with Dy3+. The samples containing Eu2+ and Eu3+ were prepared via solid-state reaction. X-ray diffraction (XRD), photo luminescent spectroscope (PLS) and thermal luminescent spectroscope (TLS) were employed to characterize the phosphors. The comparison between the emission spectra revealed that Sr3Al2O6 phosphors doped with Eu2+, Dy3+ and Eu3+, Dy3+ showed different photoluminescence. The phosphor doped with Eu3+, Dy3+ showed an intrinsic f-f transition generated from Eu3+, with two significant emissions at 591 and 610 nm. However, the phosphor doped with Eu2+, Dy3+ revealed a broad d-f emission centering around 512 nm. After the UV source was turned off, Eu2+, Dy3+ activated Sr3Al2O6 phosphor showed excellent afterglow while Eu3+, Dy3+ activated phosphor almost showed no afterglow. Thermal simulated luminescence study indicated that the persistent afterglow of Sr3Al2O6: Eu2+, Dy3+ phosphor was generated by suitable electron traps formed by the co-doped rare-earth ions (Dy3+) within the host. 相似文献
9.
A series of silica doped with different mol percentages of Ce3+ concentration was synthesized using a sol-gel method to determine the dependence of photoluminescence wavelengths and intensity on the concentrations of the dopants. Sol-gel glasses are porous networks that have been densified through chemical processing and heat treatment. Rare-earths (REs) are insoluble in silica; due to this insolubility RE ions in silicate glasses enter as network modifiers and compete for non-bridging oxygen in order to complete their coordination. The morphological, structural, thermal and optical properties of the phosphors were characterized by X-ray diffraction, scanning electron microscopy, UV-vis absorption, photoluminescence, thermogravimetric analyses and differential scanning calorimeter. Silica (SiO2) gel containing Ce3+ ions was sputter coated with Au (gold) in order to monitor surface morphology of the samples. The highest emission intensity was found for the sample with a composition of 0.5 mol% Ce3+. Cerium doped silica glasses had broad blue emission corresponding to the 2D3/2-2FJ transition at 448 nm but exhibited apparent concentration quenching above concentrations of 0.5 mol% Ce3+. 相似文献
10.
Philippe F. Smet Koen Van den Eeckhout Adrie J.J. Bos Erik van der Kolk Pieter Dorenbos 《Journal of luminescence》2012,132(3):682-689
The evaluation of persistent phosphors is often focused on the processes right after the excitation, namely on the shape of the afterglow decay curve and the duration of the afterglow, in combination with thermoluminescence glow curve analysis. In this paper we study in detail the trap filling process in europium-doped alkaline earth silicon nitrides (Ca2Si5N8:Eu, Sr2Si5N8:Eu and Ba2Si5N8:Eu), i.e., how the persistent luminescence can be induced. Both the temperature at which the phosphors are excited and the spectral distribution of the excitation light on the ability to store energy in the phosphors' lattices are investigated. We show that for these phosphors this storage process is thermally activated upon excitation in the lower 5d excited states of Eu2+, with the lowest thermal barrier for europium doped Ca2Si5N8. Also, the influence of co-doping with thulium on the trap filling and afterglow behavior is studied. Finally there exists a clear relation between the luminescence quenching temperature and the trap filling efficiency. The latter relation can be utilized to select new efficient 5d–4f based afterglow phosphors. 相似文献
11.
Traditional aluminates phosphors with persistent luminescence are chemically unstable to water or moisture. Thus, how to improve the water-resistance of these phosphors is becoming a key issue in their practical applications. In this work, a series of alkaline earth aluminate phosphors including MAl2O4:Eu2+, Dy3+ (M = Sr, Ca, Ba) have been prepared by a co-precipitation synthesis and postannealing approach, using 8-hydroxyquinoline and sodium oxalate as precipitants. The samples before and after encapsulation were well characterized by means of XRPD, FESEM, FT-IR, TGA-DTG and PL techniques as well as water resistance measurements. The precipitants involved can react with Al3+ and Sr2+ (or Ca2+, Ba2+) to form complex compounds in aqueous solution, which further convert into porous phosphors by postannealing method under reducing atmosphere. Next, triethanolamine encapsulation at room temperature was conducted onto their surfaces to improve the water resistance. The results reveal that the encapsulation of aluminate phosphors with triethanolamine can effectively enhance the water resistance, and minimally affect on persistent phosphorescence. 相似文献
12.
《Current Applied Physics》2009,9(3):618-621
Eu3+ doped SrAl2B2O7 phosphors were fabricated by the wet method. The structures of the phosphors were characterized by XRD. The doping content of Eu3+ ions in SrAl2B2O7:Eu3+ phosphors are 1%, 4%, 6%, 8%, 10% (molar fraction), respectively. Luminescence properties were analyzed by measuring the excitation and photoluminescence spectra. The luminescent properties of SrAl2B2O7:Eu3+ phosphors are discussed. It is shown that from 4% to 6% of doping content of Eu3+ ions under 392 nm excitation in SrAl2B2O7:Eu3+ phosphors is optimum. 相似文献
13.
Xiaoming Teng 《Journal of luminescence》2010,130(5):851-854
The Sr2Si5N8:Eu2+ phosphors, both undoped and doped with Tm3+, were synthesized by high temperature solid-state method. The XRD pattern shows that only Sr2Si5N8 phase is formed whatever Tm3+ was doped or not. The peak positions of both phosphors are centered at 612 nm which is assigned to the 4f65d→4f7 transition of Eu2+. It implies that the crystal field, which affects the 5d electron states of Eu2+, is not changed dramatically after the phosphor is doped with Tm3+. The afterglow time is about 10 min after Tm3+ ion is introduced into the phosphor. The concentration of Tm3+ has little influence on the afterglow time of the phosphor. The depths of trap energy level of the two phosphors were calculated based on the TL spectra. The depths of Sr2Si5N8:Eu2+ and Sr2Si5N8:Eu2+, Tm3+ are 1.75 and 1.01 eV, respectively. 相似文献
14.
Yan Wang Zhenyu You Jianfu Li Zhaojie Zhu En Ma Chaoyang Tu 《Journal of luminescence》2012,132(3):693-696
In this paper we report on the optical properties of triply Cr3+, Er3+, and RE3+ (RE=Tm, Ho, Eu) doped Gd3Ga5O12 crystals that were grown by the Czochralski method. Optical absorption, near-infrared (NIR), and mid-infrared (mid-IR) fluorescence spectra were characterized for the fabricated crystals and corresponding luminescence decay measurements under 654 nm excitation were also carried out. Based on the analysis of energy transfer process between Er and RE (RE=Tm, Ho, Eu) ions, the energy transfer efficiency (ETE) values were evaluated, correspondingly. From the spectral data of all the studied crystals, it is observed that the co-doped Cr3+ ion highly increases the absorption pump power and the three kinds of co-doped RE3+ ions depopulate the Er:4I13/2 energy level effectively. The spectral analysis shows that titled rare earth doped crystals are promising materials for ~3.0 μm mid-IR laser applications and among them Cr,Er,Eu:GGG is relatively more suitable due to its excellent optical properties compared with others. 相似文献
15.
C. Hidaka E. Yamagishi T. Takizawa 《Journal of Physics and Chemistry of Solids》2005,66(11):2061-2064
Six kind CaGa2S4 single crystals doped with different rare earth (RE) elements are grown by the horizontal Bridgman method, and their photoluminescence (PL) spectra are measured in the temperature range from 10 to 300 K. The PL spectra of Ce or Eu doped crystals have broad line shapes due to the phonon assisted 4f-5d transitions. On the other hand, those of Pr3+, Tb3+, Er3+ or Tm3+ doped samples show narrow ones owing to the 4f-4f transitions. The assignments of the electronic levels are made in reference to the reported data of RE 4f multiplets observed in same materials. 相似文献
16.
The thermoluminescence (TL) of rare earth (RE) activated sulfates of Cd, Sr and Ba was studied above room temperature. Many of the phosphors prepared exhibit an extremely bright TL following X-irradiation (most notably with Sm, Eu, Tb, Dy and Tm dopants), having an efficiency comparable to that of the highest sensitivity phosphors available for TL dosimetry, and exhibiting activator-induced glow peaks between 405 and 480°K. In a given lattice, the RE3+ ions produce a characteristic glow peak at the same temperature (independent of the particular RE ion), whereas Eu2+ produces a single glow peak at a different temperature. A decrease in glow peak temperature with increasing interatomic spacing was observed in the homologous SrSO4-BaSO4 system - this shift being most pronounced in the Eu2+ -doped materials. TL emission spectra were obtained for trivalent Sm, Tb, Dy and Tm and for divalent Eu in these sulfates (and also in CaSO4). 相似文献
17.
M. Mohapatra Y.P. Naik V. Natarajan T.K. Seshagiri Z. Singh S.V. Godbole 《Journal of luminescence》2010,130(12):2402-2406
Lithium titanate ceramics doped with three rare earth (RE) ions namely Eu3+, Dy3+ and Tb3+ were synthesized and their photoluminescence (PL) properties were investigated. PL spectra of Eu doped sample showed peaks corresponding to the 5D0→7Fj (j=0, 1, 2, 3 and 4) transitions under 230 nm excitation. Strong red emission coming from the hypersensitive 5D0→7F2 transition of Eu3+ ion suggested the presence of the dopant ion in a highly asymmetric environment. Dy doped samples showed the Dy3+ emission characteristic due to 4F9/2→6H15/2 and 4F9/2→6H13/2 transitions. Their relative intensity ratios also suggested the presence of asymmetric environment around the metal ion. In case of the Tb3+ doped sample blue-green emission corresponding to the 5D4→7Fj (j=6, 5 and 4) transitions was seen. The fluorescence lifetimes of Eu3+, Dy3+ and Tb3+ ions were found to be 645, 900 and 740 μs, respectively. PL intensity of the individual rare earth doped samples was compared with commercial red and green phosphors. It was found that the emission from Eu doped titanate sample was 46% of the commercial red phosphor and in case of the Tb samples it was 30% when excited at 230 nm. However, the synthesized Eu doped titanate sample showed better color purity as compared to the commercial phosphor. The titanate host was doped with all the three rare earths to get white light emission from the system. The individual rare earth ion content was optimized so as to get a near white light emission. The color coordinates of the triple doped systems were evaluated and plotted on the CIE x–y diagram. Our results suggest that lithium titanate has enough potential to be a phosphor material. 相似文献
18.
Luminescence characteristics of Eu2+ activated Ca2SiO4 Sr2SiO4 and Ba2SiO4 phosphorsfor white LEDs
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<正>This paper investigates the luminescence characteristics of Eu2+ activated Ca2SiO4,Sr2SiO4 and Ba2SiO4 phosphors. Two emission bands are assigned to the f-d transitions of Eu2+ ions doped into two different cation sites in host lattices,and show different emission colour variation caused by substituting M2+ cations for smaller cations.This behaviour is discussed in terms of two competing factors of the crystal field strength and covalence.These phosphors with maximum excitation of around 370 nm can be applied as a colour-tunable phosphor for light-emitting diodes(LEDs) based on ultraviolet chip/phosphor technology. 相似文献
19.
In this paper, we present the synthesis and luminescence properties of Tb3+ and Dy3+-doped lithium lutetium yttrium borate (Li6LuY(BO3)3) phosphors. We have adopted the well-known solid state reaction method for the synthesis of these phosphors. The emission intensities of the synthesized phosphors were found to reach their maximum, when doped by 1 mol% of Tb3+ and 3 mol% of Dy3+, beyond which emission intensities decrease due to concentration quenching. The homogeneous phase, crystalline structure and uniform morphology of the synthesized phosphors were confirmed by X-ray diffraction analysis (XRD) and Scanning electron microscopy (SEM). The X-ray and UV–VIS-induced luminescence, decay time and CIE chromaticity were investigated for the synthesized phosphors.The X-ray induced integrated light yield was measured to be 82% for Li6LuY(BO3)3:Tb3+ (LLYBO) and 59% for Li6LuY(BO3)3:Dy3+ of that of commercially available X-ray imaging material; Gd2O2S:Tb3+ (Gadox).LLYBO:Tb3+ phosphor displayed five major emission bands that correspond to 5Dj → 7Fj transitions. The 1931 Commission Internationale de l'Eclairage (CIE) chromaticity coordinates were also measured. 相似文献
20.
In this paper we report the combustion synthesis of rare earth (RE=Eu, Dy) doped Ba4Al2O7 phosphors. Prepared phosphors were characterized by X-ray powder diffraction (XRD), scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), CIE color co-ordinates and their photoluminescence (PL) properties were also investigated. In case of Ba4Al2O7: Eu2+, the emission spectra show unique band centered at 495 nm, which corresponds to the 4f65d1→4f7 transition of Eu2+, and PL emission spectra of Dy3+ ion under 348 nm excitation give two bands centered at 478 nm (blue) and 575 nm (yellow), which originate from the transitions of 4F9/2→6H15/2 and 4F9/2→6H13/2 of Dy3+, respectively. The results indicate that the Eu2+ and Dy3+ activated Ba4Al2O7 phosphor could find application in solid state lighting. 相似文献