Dye‐Laser Spectroscopy of Commercial  Y 2 O 3 : Eu3 +  Phosphors

Pappalardo, R.; Hunt, R.B.

doi:10.1149/1.2113940

Cited by 68 publications

(51 citation statements)

References 1 publication

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“…The inset of Figure 5 shows the wavelength range between 570 and 605nm in more detail. The strongest effect can be observed for the 5 3+ . It is therefore, confidently assigned to dysprosium contamination in the Y 2 O 3 material used for the synthesis.…”

Section: Fesem Characterisation-mentioning

confidence: 90%

“…Cathodoluminescence spectra.- Figure 5 shows CL spectra of films of monosized spherical Y 2 O 3 :Eu 3+ nanoparticles excited by an electron beam of 15keV at a current density of 3 μA/cm 2 and temperature of 298 K. The spectra are normalized to 100 arbitrary units for the 5 D 0 → 7 F 2 (C 2 ) transition at 611nm to indicate what trends can be observed for the weaker spectral transitions. For reasons of clarity the spectra with 10%, 4%, 3%, 0.8 and 0.5 mole percent europium have not been inserted in Figure 5.…”

Section: Fesem Characterisation-mentioning

confidence: 99%

“…Before 1996 these studies were focused mainly on micrometer sized particles, [4][5][6][7][8][9][10][11][12] more recently the attention has been directed to nano-sized powder materials. [13][14][15][16][17][18][19] In the earlier studies [4][5][6][7][8][9][10][11][12] the focus was on the interpretation of the excitation and emission spectra in terms of energy transfer in the Y 2 O 3 :Eu 3+ crystals, whereas in the latter studies [13][14][15][16][17][18][19] the attention shifted toward the synthesis of nanomaterials. Most studies used photoluminescence (PL) techniques, [4][5][6][7] which enabled the excitation of energy levels having a particular symmetry and yielded insight on the energy flow in Y 2 were limited to the evaluation of the luminous efficiency.…”

mentioning

confidence: 99%

“…[13][14][15][16][17][18][19] In the earlier studies [4][5][6][7][8][9][10][11][12] the focus was on the interpretation of the excitation and emission spectra in terms of energy transfer in the Y 2 O 3 :Eu 3+ crystals, whereas in the latter studies [13][14][15][16][17][18][19] the attention shifted toward the synthesis of nanomaterials. Most studies used photoluminescence (PL) techniques, [4][5][6][7] which enabled the excitation of energy levels having a particular symmetry and yielded insight on the energy flow in Y 2 were limited to the evaluation of the luminous efficiency. [10][11][12] A detailed investigation of the energy flow in Y 2 O 3 :Eu 3+ after excitation by an electron beam was performed by Klaassen et al 8 These authors also studied saturation effects in Y 2 O 3 :Eu 3+ at high current densities in an electron microscope.…”

mentioning

confidence: 99%

“…This selection is not trivial, because many peaks in the spectrum of Y 2 O 3 :Eu 3+ suffer from overlap or are combinations of more than one spectral transition. 5,6 The first phase in the energy flow in Y 2 4,20 In Y 2 O 3 there are two different Y 3+ lattice sites, which possess the point symmetries C 2 and S 6 (Schoenflies notation): 24 lattice sites have C 2 symmetry, while the other 8 have S 6 symmetry. Both sites are six coordinate and are thus present in the ratio of 3:1.…”

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confidence: 99%

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Cathodoluminescence of Nanocrystalline Y₂O₃:Eu³⁺with Various Eu³⁺Concentrations

Engelsen

Harris

Ireland

et al. 2014

ECS J. Solid State Sci. Technol.

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Herein a study on the preparation and cathodoluminescence of monosized spherical nanoparticles of Y2O3:Eu3+ having a Eu3+ concentration that varies between 0.01 and 10% is described. The luminous efficiency and decay time have been determined at low a current density, whereas cathodoluminescence-microscopy has been carried out at high current density, the latter led to substantial saturation of certain spectral transitions. A novel theory is presented to evaluate the critical distance for energy transfer from Eu3+ ions in S6 to Eu3+ ions in C2 sites. It was found that Y2O3:Eu3+ with 1-2% Eu3+ has the highest luminous efficiency of 16lm/w at 15keV electron energy. Decay times of the emission from 5D0 (C2) and 5D1 (C2) and 5D0 (S6) levels were determined. The difference in decay time from the 5D0 (C2) and 5D1 (C2) levels largely explained the observed phenomena in the cathodoluminescence-micrographs recorded with our field emission scanning electron microscope. . In this work CLtechniques were used as the characterization method of choice: in a vacuum system equipped with an electron gun and spectrometers, and in a field emission scanning electron microscope (FESEM). 3The application of Y 2 O 3 :Eu 3+ in cathode ray tubes has fostered extended luminescence studies of this material. Before 1996 these studies were focused mainly on micrometer sized particles, [4][5][6][7][8][9][10][11][12] more recently the attention has been directed to nano-sized powder materials. [13][14][15][16][17][18][19] In the earlier studies 4-12 the focus was on the interpretation of the excitation and emission spectra in terms of energy transfer in the Y 2 O 3 :Eu 3+ crystals, whereas in the latter studies [13][14][15][16][17][18][19] concentration, energy can be transferred from S 6 states to C 2 states. At low Eu 3+ concentration there is no interaction between a Eu 3+ ion at a S 6 site and a Eu 3+ ion at a C 2 site respectively and thus, there will be no energy transfer. Energy transfer also occurs in phosphors that are excited by an electron beam; therefore, it was also an objective of this work to investigate what information concerning energy transfer can be obtained from CL-spectra that are generated without activation of specified energy levels.In concentration of ca. 4.7 mole %, efficient energy transfer occurs between the S 6 and C 2 sites for Eu 3+ in the 5 D 0 level. As the 5 D 0 level in the S 6 site is 87 cm −1 higher than the same level in the C 2 site, the efficient energy transfer from S 6 to C 2 sites presumably occurs by simultaneous creation of a phonon.22 This efficient energy transfer is necessary for the high emission efficiency of the Y 2 O 3 :Eu 3+ phosphor, as the 5 D 0 → 7 F 2 transition which gives rise to the red 611 nm emission is electric dipole allowed for Eu 3+ in C 2 sites but forbidden for Eu 3+ in S 6 sites. In this work it was decided to focus on the 5 D 0 → 7 F 1 (S 6 ) transition at 582 nm and the 5 D 0 → 7 F 2 (C 2 ) transition at 611 nm, because these are reasonably well separated from other trans...

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Section: Fesem Characterisation-mentioning

confidence: 90%

Section: Fesem Characterisation-mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

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Cathodoluminescence of Nanocrystalline Y₂O₃:Eu³⁺with Various Eu³⁺Concentrations

Engelsen

Harris

Ireland

et al. 2014

ECS J. Solid State Sci. Technol.

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Phosphors

Srivastava¹,

Soules²

2000

Kirk-Othmer Encyclopedia of Chemical Technology

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PHOSPHORSLuminescence is the process of producing light in excess of thermal radiation following an excitation. A solid material exhibiting luminescence is called a phosphor. Phosphors are usually fine inorganic compound powders of a high degree of purity and a median particle size of 3-15 micrometers but may be large single crystals, used as scintillators, or glasses or thin films. Phosphors may be excited by high energy invisible uv radiation (photoluminescence), x-rays (radioluminescence), high energy electrons (cathodoluminescence), a strong electric field (electroluminescence), or in some cases infrared radiation (up-conversion), chemical reactions (chemiluminescence), or even stress (triboluminescence). Figure 1 shows the electromagnetic energy spectrum indicating some of the common energy forms that excite phosphors. Because phosphors convert the exciting energy to visible radiation, they have many everyday applications; phosphors are responsible for the light generated by fluorescent lamps, televisions, computer terminals, etc.Phosphors usually contain activator ions in addition to the host material. These ions are deliberately added in the proper proportion during the synthesis. The activators and their surrounding ions form the active optical centers. Table 1 lists some commonly used activator ions. Some solids, made up of complexes such as calcium tungstate [7790-75-2], CaWO 4 , are self-activated. Also in many photoluminescence phosphors, the primary activator does not efficiently absorb the exciting radiation and a second impurity ion is introduced known as the sensitizer. The sensitizer, which is an activator ion itself, absorbs the exciting radiation and transfers this energy to the primary activator.The optical properties of a phosphor are measured on relatively thick plaques of the phosphor powder. An important optical property for the application of the phosphor is its emission spectrum, the variation in the intensity of the emitted light versus wavelength. Fluorescent lamps must have phosphors which produce white light of high luminous efficiency and with good color rendering properties. Because individual activator centers generally emit in a relatively narrow region of the spectrum producing a colored light, more than one activator or phosphor must be used. Similarly colored televisions employ three phosphors in separate closely spaced dots; one dot contains a phosphor which emits in the blue, one in the green, and one in the red region of the spectrum. Saturated colors are needed in order for the screen to be able to reproduce nearly all colors using these emissions in different relative proportions. In other applications, such as x-ray screens, it is desirable to have an emission spectrum concentrated near the peak in the sensitivity of the receptor, such as the x-ray photographic film. The reflectance spectrum is a graph of the percentage of radiation reflected and absorbed by the powder plaque versus wavelength. The excitation spectrum gives the variation of the light output from the phos...

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