Cerium Containing Chalcogenides with Chromatic Properties

1998 ◽  
Vol 548 ◽  
Author(s):  
G. Gauthier ◽  
S. Jobic ◽  
P. Macaujdiere ◽  
R. Brec
Keyword(s):  
Electronic Transition ◽  
Room Temperature ◽  
Inductive Effect ◽  
Transition Energy ◽  
Ionic Character ◽  
Blue Fluorescence ◽  
Energy Increase ◽  
Near Ultraviolet ◽  
Visible Spectra ◽  
Chromatic Properties

ABSTRACTλ–Ce2S3, like many other cerium containing chalcogenides, presents a strong absorption in the visible spectra in relation with the CeIII-4fl → CeIII-5d1 electronic transition taking place at around 1.9 eV. This transition energy, that induces a red hue for the phase, can be increased by changing the nature of the Ce-S bonding, in particular through an enhancement of its ionicity. This can be made by inserting/substituting some alkali metal ions in the structure of λ-Ce2S3. The sodium-doped λ-Na3/8Ce15/2S3 phase for instance undergoes a CeIII-4f1 → Cemi-5d1 transition energy increase of 0.12 eV. This shift is sufficient to modify substantially the pigment properties of the material and it has been mainly related to the narrowing of the electronic bands. In CePS4, Ce2SiS5, Ce4Si3S12and Ce6Si4S17, strong covalent bondings enhance the ionic Ce-S bond through inductive effect, leading to a CeIII-4f1 → CeIII-5d1 electronic transition in the blue (Eg - 2.5 eV) hence the yellow hue of these materials. Within the Ce-Si-S family, small differences may be attributed to difference in the [CeSx] and [SiS4] polyhedra bonding. The Ce3(TS4 )2X family (X = Cl, Br, I, T = Si, Ge) does not show pigment properties because of the Ce-X bond inducing a more Ce-S ionic character (in particular when X = Br, I) and thus a higher gap that is found in the near ultraviolet. On the other hand, the phases present an important room temperature blue fluorescence.

Notizen:Phosphorescence Decay in Thallium-Doped Ammonium Chloride

1978 ◽  
Vol 33 (10) ◽  
pp. 1241-1242 ◽  
Author(s):  
S. Chaudhari ◽  
T. R. Joshi ◽  
R. V. Joshi
Keyword(s):  
Aqueous Solution ◽  
Ammonium Chloride ◽  
Mechanical Treatment ◽  
Room Temperature ◽  
Host Lattice ◽  
Luminescence Decay ◽  
Decay Rates ◽  
Negative Ion ◽  
Ultraviolet Emission ◽  
Near Ultraviolet

Abstract The phosphorescence decay rates of thallium-doped ammonium chloride (NH4Cl:Tl) phosphors, prepared by crystallization from aqueous solution, have been studied at room temperature for near-ultraviolet emission. The effects of impurity concentration as well as thermal and/or mechanical treatment on the decay rates have been examined. Phosphorescence centres consisting of a Tl+ion and a nearby negative ion vacancy are suggested to be responsible for the observed luminescence decay. The changes in the decay characteristics after pretreatments are explained on the basis of the location of the centres in normal and distorted regions of the host lattice.

Room-temperature near-ultraviolet electroluminescence from a linear silicon chain

1997 ◽  
Vol 71 (23) ◽  
pp. 3326-3328 ◽  
Author(s):  
Chien-Hua Yuan ◽  
Satoshi Hoshino ◽  
Seiji Toyoda ◽  
Hiroyuki Suzuki ◽  
Michiya Fujiki ◽  
...  
Keyword(s):  
Room Temperature ◽  
Near Ultraviolet

scholarly journals Preparation and Spectral Study of New Complexes of Some Metal Ions with 3,5-Dimethyl-1H-Pyrazol-1-yl Phenyl Methanone

2011 ◽  
Vol 8 (4) ◽  
pp. 1005-1011
Author(s):  
Baghdad Science Journal
Keyword(s):  
Magnetic Susceptibility ◽  
Elemental Analysis ◽  
Room Temperature ◽  
Molar Conductivity ◽  
The Other ◽  
Octahedral Structure ◽  
Tetrahedral Structure ◽  
Visible Spectra ◽  
Ft Ir ◽  
Uv Visible

Many complexes of 3,5-dimethyl-1H-pyrazol-1-yl phenyl methanone with Cr(III), Co(II), Ni(II), Cu(II) and Cd(II) were synthesized and characterized by FT-IR, UV/visible spectra, elemental analysis, room temperature magnetic susceptibility and molar conductivity. Cd(II) complex was expected to have tetrahedral structure while all the other complexes were expected to have an octahedral structure.

Highly Efficient and Thermally Stable Eu2+-Doped Ca9Nd(PO4)7 Phosphor for Near-Ultraviolet White-Emission LED Applications

2021 ◽  
Vol 21 (12) ◽  
pp. 5859-5866
Author(s):  
Jian Zhou ◽  
Si-Li Ren
Keyword(s):  
Room Temperature ◽  
Green Emission ◽  
Color Temperature ◽  
Multipole Interaction ◽  
Interaction Radius ◽  
Promising Alternative ◽  
Quenching Effect ◽  
Near Ultraviolet ◽  
Great Performance ◽  
Concentration Quenching Effect

Various Eu2+-based Ca9Nd(PO4)7 (CNP:xEu2+, with different x values) materials are prepared via facile solid-state reaction. Their crystal structures are investigated in detail by means of the Rietveld refinement. The structure of CNP:Eu2+ with a trigonal lattice is analogous to that of β-Ca3(PO4)2. Therefore, Eu2+ ions tend to incorporate calcium sites in the host. All the obtained samples can be excited using near ultraviolet (nUV) light to present blue-green emission. An optimal dopant concentration is verified at x = 0.8 with a large critical interaction radius (11.21 Å). The mechanism of the concentration quenching effect is assigned to the multipole-multipole interaction. CNP:xEu2+ possesses a short decay lifetime of ∼60 μs and can endure severe working conditions thanks to its great thermal stability. The relative photoluminescence (PL) intensity of CNP:0.8Eu2+ can retain 84.75% of the pristine intensity measured at room temperature, and the relative intensity remains as high as 69.97% at 423 K. The CNP:Eu2+ phosphors also show great performance in the WLED demonstration. The correlated color temperature (CCT) of the prototype device is 3404 K, with an extremely high Ra (97.6). Therefore, CNP:xEu2+ could be regarded as a promising alternative to blue green phosphors in nUV chip-based WLED applications.

More light on the low electronic transition energy bands of dithizone

1987 ◽  
Vol 43 (10) ◽  
pp. 1281-1285 ◽  
Author(s):  
M.R. Mahmoud ◽  
A.A.Abd El Gaber ◽  
A.M. El Roudi ◽  
E.M. Soliman
Keyword(s):  
Electronic Transition ◽  
Transition Energy ◽  
Energy Bands ◽  
Electronic Transition Energy

The Near-ultraviolet Absorption Spectrum of Diimide in Liquid Ammonia and its Decomposition between −65 and −38 °C

1974 ◽  
Vol 52 (13) ◽  
pp. 2513-2515 ◽  
Author(s):  
R. A. Back ◽  
C. Willis
Keyword(s):  
Absorption Spectrum ◽  
Gas Phase ◽  
Room Temperature ◽  
Liquid Ammonia ◽  
Vibrational Structure ◽  
Ultraviolet Absorption ◽  
Ultraviolet Absorption Spectrum ◽  
First Order ◽  
Rapid Decomposition ◽  
Near Ultraviolet

The near-ultraviolet absorption spectrum of diimide in liquid ammonia at −50 °C is shifted about 500 Å to the red compared with the gas-phase spectrum, with λmax = 4000 Å. The spectrum is also broadened and the vibrational structure largely obscured. It is suggested that hydrogen bonding is responsible for these changes.Diimide is much more stable in liquid ammonia between −65 and −38 °C than in the gas phase at room temperature. A first-order decay is observed with Arrhenius parameters of A = 1.9 × 103 s−1 and E = 6.6 kcal/mol; this is always preceded by a more rapid, higher-order initial decay which may be related to the rapid decomposition observed during vaporization.

Structural and Optical Properties of Commercial Microparticle Zinc Oxide

2020 ◽  
Vol 990 ◽  
pp. 302-305
Author(s):  
Razif Nordin ◽  
Nadia Latiff ◽  
Rizana Yusof ◽  
Wan Izhan Nawawi ◽  
M.Z. Salihin ◽  
...  
Keyword(s):  
Room Temperature ◽  
Band Gap Energy ◽  
X Ray Diffraction ◽  
Structural And Optical Properties ◽  
Xrd Pattern ◽  
X Ray ◽  
Commercial Grade ◽  
Irregular Shapes ◽  
Visible Spectra ◽  
Uv Visible

Commercial grade ZnO were sieved into particle size of 38 to 90 μm at room temperature. X-ray diffraction (XRD) pattern confirms the hexagonal wurzite structure of ZnO microparticles. Irregular shapes of ZnO microparticles were observed by scanning electron microscope (SEM). Fourier transform infrared spectra (FTIR) confirmed the presence of Zn-O band. In addition, Uv-visible spectra (UV-Vis) were empolyed to estimate the band gap energy of ZnO microparticles.

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