A narrow-band blue emitting phosphor Ca8Mg7Si9N22:Eu2+ for pc-LEDs

2019 ◽  
Vol 7 (13) ◽  
pp. 3730-3734 ◽  
Author(s):  
Chao Li ◽  
Xiao-Ming Wang ◽  
Feng-Feng Chi ◽  
Zu-Pei Yang ◽  
Huan Jiao
Keyword(s):  
Emission Intensity ◽  
Room Temperature ◽  
Narrow Band ◽  
Blue Emission ◽  
Thermal Quenching ◽  
Unit Cell ◽  
Photoluminescence Emission ◽  
Space Group

Ca8Mg7Si9N22 crystallizes in a tetragonal space group P42/nmc (No. 137) with a unit cell of a = 7.3271(11) Å and c = 10.336(2) Å. Ca8Mg7Si9N22:Eu2+ shows a narrow-band blue emission peaking at 400 nm with an intriguing bandwidth ∼34 nm and shows remarkably high thermal quenching resistance, maintaining 92% photoluminescence emission intensity at 420 K and 75% at 700 K of that measured at room temperature.

NQR and Crystal Structure of 4,5-Dichloroimidazole, C3H2N2Cl2

1992 ◽  
Vol 47 (1-2) ◽  
pp. 177-181 ◽  
Author(s):  
Shi-Qi Dou ◽  
Alarich Weiss
Keyword(s):  
Crystal Structure ◽  
Phase Transition ◽  
Temperature Dependence ◽  
Room Temperature ◽  
Unit Cell ◽  
Space Group ◽  
Temperature Range ◽  
Temperature Coefficients ◽  
Group D

AbstractThe two line 35Cl NQR spectrum of 4,5-dichloroimidazole was measured in the temperature range 77≦ T/K ≦ 389. The temperature dependence of the NQR frequencies conforms with the Bayer model and no phase transition is indicated in the curves v ( 35Cl)= f(T). Also the temperature coefficients of the 35Cl NQR frequencies are "normal". At 77 K the 35Cl NQR frequencies are 37.409 MHz and 36.172 MHz and at 389 K 35.758 MHz and 34.565 MHz. The compound crystallizes at room temperature with the tetragonal space group D44-P41212, Z = 8 molecules per unit cell; at 295 K : a = 684.2(5) pm, c = 2414.0(20) pm. The relations between the crystal structure and the NQR spectrum are discussed.

Tetra-n-butylammonium iodide: a space-group revision

2007 ◽  
Vol 63 (3) ◽  
pp. o1464-o1466 ◽  
Author(s):  
Wiesław Prukała ◽  
Bogdan Marciniec ◽  
Maciej Kubicki
Keyword(s):  
Crystal Structure ◽  
Room Temperature ◽  
Unit Cell ◽  
Unit Cell Parameters ◽  
Space Group ◽  
Cell Parameters ◽  
Temperature Determination

The crystal structure of tetra-n-butylammonium iodide, C16H36N+·I−, has been redetermined at room temperature and at 100 (1) K. In the low-quality (R = 0.142) room-temperature determination by Wang, Habenschuss, Xenopoulos & Wunderlich [Mol. Cryst. Liq. Cryst. Sci. Technol. Sect. A (1995), 264, 115–129], this structure was described as crystallizing in the space group C2 with Z′ = 2. Our results prove that the correct space group is C2/c (with the same unit-cell parameters as in the original determination) at both temperatures. In the crystal structure, the iodide anions fill the voids in the grid-like cationic structure. Weak C—H...I interactions (eight per anion) strengthen this packing.

X-ray powder diffraction data for compound DyNiSn

1997 ◽  
Vol 12 (3) ◽  
pp. 134-135
Author(s):  
Liangqin Nong ◽  
Lingmin Zeng ◽  
Jianmin Hao
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Figure Of Merit ◽  
Room Temperature ◽  
Unit Cell ◽  
Powder Diffraction Data ◽  
X Ray Diffraction ◽  
Space Group ◽  
X Ray ◽  
Diffraction Patterns

The compound DyNiSn has been studied by X-ray powder diffraction. The X-ray diffraction patterns for this compound at room temperature are reported. DyNiSn is orthorhombic with lattice parameters a=7.1018(1) Å, b=7.6599(2) Å, c=4.4461(2) Å, space group Pna21 and 4 formula units of DyNiSn in unit cell. The Smith and Snyder Figure-of-Merit F30 for this powder pattern is 26.7(0.0178,63).

X-ray powder diffraction data of anilinium trimolybdate tetrahydrate and anilinium trimolybdate dihydrate

1999 ◽  
Vol 14 (4) ◽  
pp. 280-283 ◽  
Author(s):  
A. Rafalska-Łasocha ◽  
W. Łasocha ◽  
M. Michalec
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Room Temperature ◽  
Unit Cell ◽  
Powder Diffraction Data ◽  
Unit Cell Parameters ◽  
Space Group ◽  
X Ray ◽  
Cell Parameters ◽  
Diffraction Patterns

The X-ray powder diffraction patterns of anilinium trimolybdate tetrahydrate, (C6H5NH3)2Mo3O10·4H2O, and anilinium trimolybdate dihyhydrate, (C6H5NH3)2Mo3O10·2H2O, have been measured in room temperature. The unit cell parameters were refined to a=11.0670(7) Å, b=7.6116(8) Å, c=25.554(3) Å, space group Pnma(62) and a=17.560(2) Å, b=7.5621(6) Å, c=16.284(2) Å, β=108.54(1)°, space group P21(4) or P21/m(11) for orthorhombic anilinium trimolybdate tetrahydrate and monoclinic anilinium trimolybdate dihydrate, respectively.

Refinement of the Crystal Structure of the Low-quartz Modification of Ferric Phosphate

1975 ◽  
Vol 53 (14) ◽  
pp. 2064-2067 ◽  
Author(s):  
Hok Nam Ng ◽  
Crispin Calvo
Keyword(s):  
Crystal Structure ◽  
Least Squares ◽  
Room Temperature ◽  
Unit Cell ◽  
Full Matrix ◽  
Space Group ◽  
Ferric Phosphate ◽  
R Value

The structure of ferric phosphate at room temperature was refined on a Dauphiné-twinned crystal using full-matrix least-squares methods. The final R value was 0.078 for 487 symmetry-independent reflections whose intensities were corrected for twinning. The structure was found to be isotypic with AlPO4 (berlinite) with the space group P3121 and four formula units in a unit cell defined by a = 5.036(2) and c = 11.255(4) Å. The structure is also closely related to that of α-quartz with a nearly doubled c-axis because of the ordering of Fe and P atoms. The PO4 tetrahedron is almost regular with a mean P—O distance of 1.526 Å. The Fe3+ ion is tetrahedrally coordinated with an average Fe—O distance of 1.853 Å.

Study on Luminescent Properties of YAG:Ce3+, Gd3+/La3+ Prepared by Co-Precipitation Method

2014 ◽  
Vol 1002 ◽  
pp. 29-34
Author(s):  
Rong Feng Guan ◽  
Ya Jun You ◽  
Juan Song ◽  
Gui Hua Hou
Keyword(s):  
Emission Intensity ◽  
Room Temperature ◽  
Thermal Quenching ◽  
Luminescent Properties ◽  
Ammonium Bicarbonate ◽  
Color Temperature ◽  
Precipitation Method ◽  
Structure Morphology ◽  
Relative Emission Intensity ◽  
Co Precipitation

The YAG:Ce3+, Gd3+/La3+ yellow phosphors were prepared by co-precipitation method with 0.1mol/L ammonium bicarbonate and aqueous ammonia as precipitants, and the crystal structure, morphology, luminescent properties were investigated. The results indicated that the emission peaks of the YAG:Ce3+, Gd3+/La3+ were redshifted from 535nm to 545.5nm /547nm, and the relative emission intensity declined from 330nm to 145/132 with doping content of Gd3+ /La3+ increased from 0 to 0.9mol at room temperature. Compared with Gd-doping phosphors, the redshift of La3+-doping phosphor was larger and the relative emission intensity declined more quickly. Compared with YAG:Ce3+, the thermal quenching characteristics of YAG:Ce,Gd and YAG:Ce,La were noticeably worse when the temperature increased, but the extents of peak wavelength redshifts were almost the same, about is 7-8nm in the experimental temperature range (50-200°C), have little relation with the doping concentration change. Doping concentrations of Gd or La couldn't be too high, and the suitable concentration was less than 0.6mol at the regulating color temperature and color index.

Structures and phase transition of three isomers of 1-phenylindolin-2-one derivatives: 6-chloro-1-phenylindolin-2-one, 4-chloro-1-phenylindolin-2-one and 1-(3-chlorophenyl)indolin-2-one

2018 ◽  
Vol 74 (12) ◽  
pp. 1750-1758
Author(s):  
Bing Wang ◽  
Qi Fang
Keyword(s):  
Phase Transition ◽  
Low Temperature ◽  
Phenyl Ring ◽  
Density Functional ◽  
Room Temperature ◽  
Unit Cell ◽  
Monoclinic Space Group ◽  
Functional Theory ◽  
Triclinic Space Group ◽  
Space Group

Three 1-phenylindolin-2-one derivatives, namely 6-chloro-1-phenylindolin-2-one (A), 4-chloro-1-phenylindolin-2-one (B) and 1-(3-chlorophenyl)indolin-2-one (C), all C14H10ClNO, have been synthesized and the structures of these compounds at room temperature (A RT, B RT and C RT) and low temperature (A LT, B LT and C LT) have been determined. Crystal A at 295 K (A RT) crystallized in the monoclinic space group P21/c and the phenyl ring of the unique molecule exhibits disorder over two positions. At low temperature, the disorder disappeared and crystal A at 90 K (A LT) crystallized in the triclinic space group P\overline{1} with a doubled unit-cell volume and four molecules in the asymmetric unit. Density functional theory (DFT) calculations revealed a low oscillation barrier (0.24 kcal mol−1) of the phenyl ring of molecule A and the phase transition from the P21/c structure to the P\overline{1} structure can be interpreted in terms of the freezing out of the two conformations at low temperature. Crystal B retains space group P21/c in the temperature range from 100 to 297 K. A kind of obtuse-cell to acute-cell change can be recognized; if the unit cell of B LT at 100 K is set to be a standard obtuse cell [β = 90.341 (2)°] and the cell is kept untransformed in the course of temperature changing, the cell of B RT at 297 K was found to be acute [β = 89.288 (2)°]. The molecules in structure C are packed in layers, with C—H...O hydrogen bonds between neighbouring layers.

The crystal structures of Cu1•8Se, Cu3Se2, α- and γCuSe, CuSe2, and CuSe2II

1976 ◽  
Vol 54 (6) ◽  
pp. 841-848 ◽  
Author(s):  
Robert Donald Heyding ◽  
Ritchie MacLaren Murray
Keyword(s):  
Crystal Structures ◽  
Powder Diffraction ◽  
Room Temperature ◽  
Unit Cell ◽  
Intensity Data ◽  
Diffraction Intensity ◽  
Space Group ◽  
X Ray ◽  
Model Based ◽  
Tetrahedral Sites

The crystal structures of a number of copper selenides have been re-examined using X-ray powder diffraction intensity data. |F0| values for Cu1•8Se at room temperature (a = 5.765 Å) are satisfied by a model based on space group Fm3m with 4 Se atoms per unit cell on the fcc sites, 5.2 Cu atoms on the tetrahedral sites, and 2.0 Cu atoms on the trigonal sites in the Se sublattice. Cu3Se2 is tetragonal, [Formula: see text] a = 6.402, c = 4.279 Å, with Cu(1) in 2(a), Cu(2) in 4(e) with x = 0.147 ± 5, z = 0.781 ± 9, and Se in 4(e) with x = 0.272 ± 3, z = 0.264 ± 7. CuSe2 has the orthorhombic C18 marcasite structure, Pnnm, a = 5.005, b = 6.182, c = 3.740 Å, with Cu in 2(a), and Se in 4(g) with x = 0.184 ± 1, y = 0.385 ± 1. CuSe2II has the cubic C2 pyrite structure, Pa3, a = 6.116 Å, with Cu in 4(a), and Se in 8(c) with x = 0.3891 ± 5.Neither αCuSe nor γCuSe have the CuS covellite structure.These results are discussed in some detail.

scholarly journals Crystal Structure and 35Cl NQR of ( — ) β-(trichloromethyl)- β-propiolactone. Comparison with (±) β-(trichloromethyl)-β-propiolactone

1993 ◽  
Vol 48 (3) ◽  
pp. 491-496 ◽  
Author(s):  
Shi-qi Dou ◽  
Reha Basaran ◽  
Helmut Paulus ◽  
Alarich Weiss
Keyword(s):  
Crystal Structure ◽  
Room Temperature ◽  
Unit Cell ◽  
Intramolecular Interactions ◽  
Space Group ◽  
Solid States ◽  
35Cl Nqr ◽  
Independent Molecules ◽  
Group D ◽  
Limits Of Error

Abstract The crystal structure of(-)β-(trichloromethyl)-β-propiolactone at room temperature is reported, as is the 35Cl NQR spectrum in the range 77 ≦ T/K ≦ 323.5. The compound crystallizes with the space group D24-212121, Z = 8, a = 2416.0 (10) pm, b = 975.6 (4) pm, c = 595.0 (2) pm. The intramolecular distances and angles of the two crystallographically independent (-) molecules in the unit cell are equal within the limits of error. The spread of the 35Cl NQR spectrum is within 600 kHz, not changing in the temperature range covered. The crystal structure and 35Cl NQR spectrum are discussed.The results found for the (-) compound are compared with the corresponding ones reported for the (±) compound [1], and the influence of the different intramolecular interactions in the two solid states of the chemically identical compounds on the NQR spectrum is discussed.

A low-temperature polymorph ofm-quinquephenyl

2012 ◽  
Vol 68 (12) ◽  
pp. o492-o497 ◽  
Author(s):  
Ligia R. Gomes ◽  
R. Alan Howie ◽  
John Nicolson Low ◽  
Ana S. M. C. Rodrigues ◽  
Luís M. N. B. F. Santos
Keyword(s):  
Low Temperature ◽  
Cell Volume ◽  
Room Temperature ◽  
Unit Cell Volume ◽  
Unit Cell ◽  
Geometric Parameters ◽  
Asymmetric Unit ◽  
Cell Axis ◽  
Space Group ◽  
Π Interactions

A low-temperature polymorph of 1,1′:3′,1′′:3′′,1′′′:3′′′,1′′′′-quinquephenyl (m-quinquephenyl), C30H22, crystallizes in the space groupP21/cwith two molecules in the asymmetric unit. The crystal is a three-component nonmerohedral twin. A previously reported room-temperature polymorph [Rabideau, Sygula, Dhar & Fronczek (1993).Chem. Commun.pp. 1795–1797] also crystallizes with two molecules in the asymmetric unit in the space groupP\overline{1}. The unit-cell volume for the low-temperature polymorph is 4120.5 (4) Å3, almost twice that of the room-temperature polymorph which is 2102.3 (6) Å3. The molecules in both structures adopt a U-shaped conformation with similar geometric parameters. The structural packing is similar in both compounds, with the molecules lying in layers which stack perpendicular to the longest unit-cell axis. The molecules pack alternately in the layers and in the stacked columns. In both polymorphs, the only interactions between the molecules which can stabilize the packing are very weak C—H...π interactions.

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