Preparation of hexagonal cerium oxide nanoflakes by a surfactant-free route and its optical property

2007 ◽  
Vol 22 (11) ◽  
pp. 3006-3013 ◽  
Author(s):  
X. Yu ◽  
P. Ye ◽  
L. Yang ◽  
S. Yang ◽  
P. Zhou ◽  
...  
Keyword(s):  
Cerium Oxide ◽  
Visible Region ◽  
Blue Shift ◽  
Emission Peak ◽  
X Ray Diffraction ◽  
X Ray ◽  
Strong Reflection ◽  
Mean Size ◽  
The Mean ◽  
Pl Emission

Hexagonal cerium oxide nanoflakes have been synthesized by using a surfactant-free route. Transmission electcron microscopy (TEM), x-ray diffraction (XRD), infrared spectroscopy (FTIR), thermogravimetric and differential thermal analysis (TG-DTA), Brunauer–Emmett–Teller adsorption isotherm (BET), photoluminescence (PL), and ultraviolet–visible (UV–VIS) were used to characterize the sample. The mean size of the nanoflakes is about 30 nm and the specific surface is about 70.08 m2·g−1 when annealed at 400 °C. The acidity and superfluous NH4NO3 play a key role on the formation of nanoflakes in which there exists Ce (IV) and very little Ce (III). The nanoflakes exhibit a wide PL emission peak among 350–400 nm, strong absorption ranged from 200–450 nm, and strong reflection in the visible region. As the sizes of as-prepared samples decrease, a clear blue shift in the absorbing edge is observed. The linear relationship between ΔEg and D is shown in a log–log plot. The as-prepared cerium oxide nanoflakes can be widely used as UV absorbent and polishing materials.

scholarly journals Cubic InGaN Grown by MOCVD

1999 ◽  
Vol 4 (S1) ◽  
pp. 239-243
Author(s):  
J.B. Li ◽  
Hui Yang ◽  
L.X. Zheng ◽  
D.P. Xu ◽  
Y.T. Wang
Keyword(s):  
Room Temperature ◽  
Emission Peak ◽  
Buffer Layers ◽  
Cubic Phase ◽  
Yellow Luminescence ◽  
X Ray Diffraction ◽  
High Quality ◽  
X Ray ◽  
Cubic Gan ◽  
Pl Emission

We report on the growth of high-quality cubic phase InGaN on GaAs by MOCVD. The cubic InGaN layers are grown on cubic GaN buffer layers on GaAs (001) substrates. The surface morphology of the films are mirror-like. The cubic nature of the InGaN films is obtained by X-ray diffraction (XRD) measurements. The InGaN layers show strong photoluminescence (PL) at room temperature. Neither emission peak from wurtzite GaN nor yellow luminescence is observed in our films. The highest In content as determined by XRD is about 17% with an PL emission wavelength of 450 nm. The FWHM of the cubic InGaN PL peak are 153 meV and 216 meV for 427 nm and 450 nm emissions, respectively. It is found that the In compositions determined from XRD are not in agreement with those estimated from PL measurements. The reasons for this disagreement are discussed.

scholarly journals Near UV-Blue Excitable Green-Emitting Nanocrystalline Oxide

2011 ◽  
Vol 2011 ◽  
pp. 1-7 ◽  
Author(s):  
C. E. Rodríguez-García ◽  
N. Perea-López ◽  
G. A. Hirata
Keyword(s):  
Broad Band ◽  
Emission Peak ◽  
Electronic Transitions ◽  
Excitation Band ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Pl Emission ◽  
Intense Broad Band ◽  
Nanocrystalline Oxide

Green-emitting Eu-activated powders were produced by a two-stage method consisting of pressure-assisted combustion synthesis and postannealing in ammonia. The as-synthesized powders exhibited a red photoluminescence (PL) peak located at  nm when excited with  nm UV. This emission peak corresponds to the5D0→7F2transition in Eu3+. After annealing in ammonia, the PL emission changed to an intense broad-band peak centered at  nm, most likely produced by 4f65d1→4f7electronic transitions in Eu2+. This green-emitting phosphor has excitation band in the near UV-blue region (–450 nm). X-ray diffraction analysis reveals mainly the orthorhombic EuAlO3and Al2O3phases. Transmission electron microscopy observations showed that the grains are formed by faceted nanocrystals (~4 nm) of polygonal shape. The excellent excitation and emission properties make these powders very promising to be used as phosphors in UV solid-state diodes coupled to activate white-emitting lamps.

scholarly journals Hydrothermal Synthesis of Sb2S3Nanorods Using Iodine via Redox Mechanism

2011 ◽  
Vol 2011 ◽  
pp. 1-5 ◽  
Author(s):  
Abdolali Alemi ◽  
Sang Woo Joo ◽  
Younes Hanifehpour ◽  
Aliakbar Khandar ◽  
Ali Morsali ◽  
...  
Keyword(s):  
Elemental Sulfur ◽  
Orthorhombic Phase ◽  
Blue Shift ◽  
Atomic Ratio ◽  
High Yield ◽  
X Ray Diffraction ◽  
X Ray ◽  
Spectrometry Analysis ◽  
Pl Emission ◽  
First Time

Crystalline antimony sulfide (Sb2S3) with nanorods morphology was successfully prepared via hydrothermal method by the reaction of elemental sulfur, antimony, and iodine as starting materials with high yield at 180∘C for 24 h. Using oxidation reagent like iodine as an initiator of redox reaction to prepare Sb2S3is reported for first time. The powder X-ray diffraction pattern shows the Sb2S3crystals belong to the orthorhombic phase with calculated lattice parameters,a=1.120 nm,b=1.128 nm, andc=0.383 nm. The quantification of energy-dispersive X-ray spectrometry analysis peaks gives an atomic ratio of 2 : 3 for Sb : S. TEM and SEM studies reveal the appearance of the as-prepared Sb2S3is rodlike which is composed of nanorods with the typical width of 50–140 nm and length of up to 4 μm. The PL emission indicates that band gap of Sb2S3is around 2.50 ev, indicating a considerable blue shift relative to the bulk. A formation mechanism of Sb2S3nanostructure is proposed.

Synthesis and Characterization of Surface Protected Nanocrystalline Particles of Titania

1998 ◽  
Vol 519 ◽  
Author(s):  
E. Scolan ◽  
C. Sanchez
Keyword(s):  
X Ray Diffraction ◽  
Elastic Light Scattering ◽  
Titanium Butoxide ◽  
X Ray ◽  
Toluene Sulfonic Acid ◽  
Nanocrystalline Particles ◽  
Mean Size ◽  
The Mean ◽  
Cp Mas Nmr

AbstractMonodisperse non-aggregated nanoparticles of titania are obtained through hydrolysis at 60°C of titanium butoxide in the presence of acetylacetone and para-toluene sulfonic acid. After drying the resulting xerosols can be dispersed without aggregation in water-alcoholic or alcoholic solutions. The characterizations of the nanoparticles have been carried out by using quasi-elastic light scattering (QELS), 13C 1H in solution and X-ray diffraction, TEM, TG-DTA, 13C CP-MAS NMR in the solid state. The mean size of the anatase oxide core can be adjusted in the I to 5 nanometer range by a careful tuning of the synthetic conditions. The anatase particles are surrounded by acetylacetonato ligands, para-toluene sulfonate based species and water.

scholarly journals Annealing Effects on Photocatalytic Activity of Zn0.2Cd0.8S Films Prepared by Chemical Bath Deposition

2014 ◽  
Vol 2014 ◽  
pp. 1-6 ◽  
Author(s):  
Yi-Feng Chai ◽  
Ling-Ling Wang ◽  
Gui-Fang Huang ◽  
Wei-Qing Huang ◽  
Yan-Hua Zhu
Keyword(s):  
Photocatalytic Activity ◽  
Heating Rate ◽  
Chemical Bath Deposition ◽  
Visible Region ◽  
X Ray Diffraction ◽  
X Ray ◽  
Glass Substrates ◽  
Mean Grain Size ◽  
Annealing Effects ◽  
The Mean

Zn0.2Cd0.8S alloyed films were prepared on glass substrates at room temperature using chemical bath deposition method. The obtained films were annealed at temperatures ranging from 200°C to 500°C with heating rate of 5°C/min and annealed at 400°C with heating rate of 2°C/min and 10°C/min. The films were characterized by X-ray diffraction, scanning electron microscopy, energy-dispersive spectroscopy, and UV-VIS spectrophotometer. The increasing of annealing temperature increases the crystallinity and the mean grain size of Zn0.2Cd0.8S alloyed films and significantly enhances the absorption in the visible region. The efficient visible light photocatalytic activity for annealed Zn0.2Cd0.8S alloyed films is associated with the larger size grain and the higher crystallinity.

Characterization of Ultra Fine Palladium Particles with the Mean Size of 20 A by X-Ray Diffraction

1981 ◽  
Vol 50 (9) ◽  
pp. 3071-3074 ◽  
Author(s):  
Ken-ichi Ohshima ◽  
Shigeki Yatsuya ◽  
Jimpei Harada
Keyword(s):  
X Ray Diffraction ◽  
X Ray ◽  
Mean Size ◽  
The Mean ◽  
Palladium Particles

scholarly journals Outstanding Photoluminescence in Pr3+-Doped Perovskite Ceramics

Micromachines ◽  
2018 ◽  
Vol 9 (9) ◽  
pp. 419
Author(s):  
Jiameng Zhang ◽  
Yanan Hao ◽  
Meihua Bi ◽  
Guoyan Dong ◽  
Xiaoming Liu ◽  
...  
Keyword(s):  
Emission Spectra ◽  
Green Emission ◽  
Emission Peak ◽  
Ferroelectric Ceramics ◽  
X Ray Diffraction ◽  
Green Band ◽  
Conventional Solid State Reaction ◽  
X Ray ◽  
Application Range ◽  
Pl Emission

Ba (Zr0.2Ti0.8) O3-50% (Ba0.7Ca0.3) TiO3 (BZT-0.5BCT) ceramics with different doping contents of Pr3+ were prepared by the conventional solid-state reaction. The phase structure and crystallinity of the fabricated ceramics were investigated by X-ray diffraction, Raman spectroscopy, and scanning electron microscopy. Photoluminescence (PL) emission spectra were measured to analyze the PL characteristics. The strong intensities of a green band at 489 nm and a red band at 610 nm were observed. The maximum emission intensity of the PL spectrum was achieved in the BZT-0.5BCT ceramic with 0.2% mol of Pr3+ ions. Furthermore, the PL spectra of BZT-0.5BCT ceramics were found to be sensitive to polarization of the ferroelectric ceramics. Compared with the unpoled ceramics, the green emission increased about 42% and a new emission peak at 430 nm appeared for the poled ceramics. With excellent intrinsic ferroelectricity and an enhanced PL property, such material has potential to realize multifunctionality in a wide application range.

The Determination of Crystallite Size and Size Distribution from Broadened X-Ray Diffraction Lines

1961 ◽  
Vol 5 ◽  
pp. 94-103 ◽  
Author(s):  
H. F. Quinn ◽  
P. Cherin
Keyword(s):  
Harmonic Analysis ◽  
Size Distribution ◽  
Fourier Coefficients ◽  
Distribution Functions ◽  
Composite Sample ◽  
X Ray Diffraction ◽  
X Ray ◽  
Mean Size ◽  
The Mean

AbstractMagnesium oxide crystallites having mean dimensions in the range of 25–1000 A can be prepared by controlled thermal decomposition of the carbonate.Following some earlier investigations of Birks and Friedman, we have determined the mean size and size distribution of several such MgO samples from the broadened X-ray diffraction lines which they exhibit. Contrary to the procedure of the above investigators, the harmonic analysis due to Stokes has been used to correct for instrumental broadening and values of mean-size and size-distribution functions obtained from the Fourier coefficients by the methods of Warren and Averbach.The results obtained are compared with average sizes and distributions obtained by direct examination of the samples in an electron microscope.A composite sample has been prepared by mixing known quantities of the sample previously studied. The distribution function obtained by harmonic analysis of one diffraction line of the composite sample is compared with the function calculated from the distributions of its components.Conclusions are drawn concerning the significance of the results obtained by the Warren technique: in particular, the average sizes obtained by this method are compared with those given by the approximate method used by Birks and Friedman.

scholarly journals Модификация структурно-морфологических свойств германия в многослойной нанопериодической структуре Al-=SUB=-2-=/SUB=-O-=SUB=-3-=/SUB=-/Ge с промежуточными слоями Si при отжиге

2021 ◽  
Vol 55 (10) ◽  
pp. 882
Author(s):  
М.В. Байдакова ◽  
Н.А. Берт ◽  
В.Ю. Давыдов ◽  
А.В. Ершов ◽  
А.А. Левин ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Heat Treatment ◽  
Annealing Temperature ◽  
Electron Beam Evaporation ◽  
X Ray Diffraction ◽  
Bimodal Size Distribution ◽  
X Ray ◽  
Transmission Electron ◽  
Mean Size ◽  
The Mean

Multi-layered nanosized Al2O3/Ge/Si structures manufactured by electron-beam evaporation and annealed at a temperature within the range 700−900◦C are examined using transmission electron microscopy, Raman spectroscopy and X-ray diffraction techniques. The periodic structure with a good layer planarity is confirmed to retain after heat treatment up to 900◦C. At an annealing temperature above 700◦C, nanocrystallites with a bimodal size distribution start to form within initially amorphous Ge layers, the mean size of small crystallites being determined by Ge layer thickness and annealing temperature. An essential loss of Ge from multi-layered structure after 900oC anneal and development of Ge1−x Six solid solution with x up to 0.07 in the nanocrystallites is revealed.

Preparation of Nanometer ZnO Compound Particles and Ultraviolet Absorption Properties

2012 ◽  
Vol 571 ◽  
pp. 43-47
Author(s):  
Ying Jia ◽  
Xing Yun Wang ◽  
Tian Tian Liu ◽  
Guo Gen Xu
Keyword(s):  
Visible Region ◽  
Blue Shift ◽  
X Ray Diffraction ◽  
Absorption Properties ◽  
Visible Absorption ◽  
Weak Absorption ◽  
X Ray ◽  
Reflective Spectrum ◽  
Absorption Performance ◽  
Scanning Electron

ZnO/TiO2 and ZnO/SnO2 composite nanoparticles were prepared by hydrothermal combined-assisted ethanol method , The products were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray spectrometer (EDS), and the uv-vis absorption performance of which was also characterized by uv-vis diffuse reflective spectrum (UV-vis). The results of the research showed that, in ultraviolet-visible absorption spectra diffuse, the maximum absorption peaks of ZnO/TiO2 and ZnO/SnO2 nanocomposite particles were blue-shift comparing to the pure nanometer ZnO, and there were also weak absorption in the visible region.

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