Uniform Phosphor Spheres of Diverse Emission Colours via Homogeneous Precipitation

2011 ◽  
Vol 403-408 ◽  
pp. 1424-1427
Author(s):  
Chang Fa Li ◽  
Ji Guang Li
Keyword(s):  
Homogeneous Precipitation ◽  
Uniform Size ◽  
White Leds ◽  
Field Emission Displays ◽  
Concentration Quenching Of Luminescence ◽  
Sequential Precipitation ◽  
Luminescent Films ◽  
Basic Carbonate ◽  
Plasma Display ◽  
Oxide Particles

Basic carbonate monospheres of various lanthanide combinations are successfully synthesized by the urea-based homogeneous precipitation technique, which are then converted into well dispersed phosphor particles that emit diverse colours. Sequential precipitation is commonly observed for these mixed cation systems, calling for adequate annealing of the basic carbonate precursors to attain cation homogenization in the final oxide particles and thus better luminescence, through eliminating localized concentration quenching of luminescence. It is shown that, owing to their excellent dispersion and uniform size, the phosphor spheres are readily assembled into close-packed luminescent films, allowing their wide applications in white LEDs, plasma display panels (PDPs), and field emission displays (FEDs).

Synthesis of LiCoO2 particles with tunable sizes by a urea-based-homogeneous-precipitation method

2020 ◽  
Vol 111 (4) ◽  
pp. 347-355
Author(s):  
Munekazu Motoyama ◽  
Hiroki Iwasaki ◽  
Miyuki Sakakura ◽  
Takayuki Yamamoto ◽  
Yasutoshi Iriyama
Keyword(s):  
Size Distribution ◽  
Average Diameter ◽  
Precipitation Method ◽  
Homogeneous Precipitation ◽  
Uniform Size ◽  
Homogeneous Precipitation Method ◽  
Wide Range ◽  
Size Uniformity ◽  
Average Size ◽  
Uniform Size Distribution

Abstract This paper reports the synthesis of monodisperse spherical LiCoO2 particles in a wide range of average diameter using a urea-based-uniform-precipitation method. The average diameter of LiCoO2 particles can be varied from 2 to 14 lm with a uniform size distribution. The effective approach to maintain the size uniformity while changing the average size of LiCoO2 particles is to keep the ratio of [CO(NH2)2] to [CoSO4] at 8 even when the CoSO4 and urea concentrations are changed.

Microstructure and Spectroscopy of Lu2O3:Eu Prepared Using Various Synthesis Techniques

2004 ◽  
Vol 99-100 ◽  
pp. 25-30 ◽  
Author(s):  
E. Zych ◽  
J. Trojan-Piegza ◽  
L. Kępiński ◽  
P. Dorenbos
Keyword(s):  
Uniform Distribution ◽  
Spherical Particles ◽  
Nanocrystalline Powders ◽  
Nanocrystalline Powder ◽  
Homogeneous Precipitation ◽  
Uniform Size ◽  
X Ray ◽  
Methods Of Synthesis ◽  
Excited Luminescence ◽  
Subsequent Decomposition

Nanocrystalline powders of Lu2O3:Eu with activator content varying between 0.2%-10% were prepared using four different methods of synthesis. The products differed in their microstructure and crystallites sizes. Combustion of Lu(NO3)3 with urea produced strongly agglomerated material, most probably with significantly non-uniform distribution of the Eu3+ dopant. Replacing urea with glycine for the combustion produced only slightly agglomerated, voluminous, fluffy powder. Applying the Pechini technique resulted in significantly agglomerated powder while the homogeneous precipitation of Lu(OH)3 with urea at 90 °C and its subsequent decomposition to Lu2O3 at 650 °C resulted in a powder of perfectly spherical particles with a uniform size of about 130 nm with very low agglomeration. The efficiency of X-ray excited luminescence of our nanocrystalline Lu2O3:5%Eu was compared to that of the commercial microcrystalline Gd2O2S:Eu. It was found that the commercial phosphor performed four times more efficiently than our nanocrystalline powder. We consider this to be rather encouraging as the fabrication of our powder is not optimized yet. It seems that Lu2O3:Eu, even in nanocrystalline form, can perform much more efficiently which would make it a promising X-ray phosphor.

SYNTHESIS AND MORPHOLOGICAL CONTROL OF MONODISPERSED MICROSIZED CERIA PARTICLES

2010 ◽  
Vol 17 (02) ◽  
pp. 147-152 ◽  
Author(s):  
S. YIN ◽  
Y. MINAMIDATE ◽  
T. SATO
Keyword(s):  
Particle Size ◽  
Cerium Oxide ◽  
Room Temperature ◽  
Aging Treatment ◽  
Precipitation Process ◽  
Homogeneous Precipitation ◽  
Morphological Control ◽  
Oxide Particles ◽  
Cerium Carbonate ◽  
Carbonate Precursor

The morphological control of crystalline cerium oxide particles was realized by homogeneous precipitation process followed by calcination in air at 400°C. The effects of room temperature pre-aging time on the morphologies of final products were investigated. Monodispersed rod-like cerium carbonate precursor was produced at 70°C for 2 h using the solution without pre-aging treatment. In contrast, monodispersed spherical precursor and plate-like precursor were obtained under the same conditions after pre-aging the solution at 25°C for 72 and 144 h, respectively. Ceria particles with similar morphologies and particle size to those of carbonate precursor could be obtained after calcination in air at 400°C. The monodispersed spherical, rod-like, and plate-like cerium oxide particles were successfully synthesized.

Synthesis of spherical metal oxide particles using homogeneous precipitation of aqueous solutions of metal sulfates with urea

2006 ◽  
Vol 169 (1) ◽  
pp. 33-40 ◽  
Author(s):  
Jan Šubrt ◽  
Václav Štengl ◽  
Snejana Bakardjieva ◽  
Lorant Szatmary
Keyword(s):  
Metal Oxide ◽  
Aqueous Solutions ◽  
Homogeneous Precipitation ◽  
Oxide Particles

Monodispersed Sc2O3 precursor particles via homogeneous precipitation: Synthesis, thermal decomposition, and the effects of supporting anions on powder properties

2003 ◽  
Vol 18 (5) ◽  
pp. 1149-1156 ◽  
Author(s):  
Ji-Guang Li ◽  
Takayasu Ikegami ◽  
Toshiyuki Mori ◽  
Yoshiyuki Yajima
Keyword(s):  
Thermal Decomposition ◽  
Amorphous State ◽  
Precipitation Method ◽  
Homogeneous Precipitation ◽  
X Ray ◽  
Monodispersed Particles ◽  
Homogeneous Precipitation Method ◽  
Basic Carbonate ◽  
Powder Properties ◽  
Precipitation Synthesis

Monodispersed Sc2O3 precursor particles were synthesized by the urea-based homogeneous precipitation method, with an investigation into the effects of supporting anions (NO3−, Cl−, and SO4 2−) on powder properties. Characterizations of the powders were achieved by elemental analysis, x-ray diffractometry, Fourier transform infrared, differential thermal analysis/thermogravimetry, high-resolution scanning electron microscopy, and the Brunauer-Emmett-Teller method. Unlike other rare earths, Sc3+ does not precipitate as basic carbonate but instead forms hydrated γ-ScOOH from either nitrate or chloride solution. Particles of the hydrated γ-ScOOH are pumpkin-shaped (approximately 1.0 μm) and are made up of thin-platelike crystallites emanating from a common axis. The presence of complexing SO42− changes the reaction chemistry toward Sc2O3 powders, leading to basic sulfate [Sc(OH)1.6(SO4)0.7 η H2O] precursor particles having hexagonal morphology (approximately 10 μm in diameter and 0.5 μm in thickness). The hydrated γ-ScOOH directly converts to Sc2O3 by calcination at 400 °C or above, while the basic sulfate transforms to oxide at temperatures ≥ 900 °C via an amorphous state and a Sc2(SO4)3 intermediate. The effect of SO42− on powder morphologies and reaction chemistry is discussed. Nanocrystalline Sc2O3 powders comprising monodispersed particles were obtained via thermal decomposition of the precursors.

Influence of Thermo-Mechanical Processing on the Microstructure of Beryllia Dispersed Nickel Alloys

1973 ◽  
Vol 31 ◽  
pp. 184-185
Author(s):  
M.S. Grewal ◽  
S.A. Sastri ◽  
N.J. Grant
Keyword(s):  
High Temperature ◽  
Nickel Alloys ◽  
Thermomechanical Processing ◽  
Cold Work ◽  
High Temperature Strength ◽  
Strengthening Effect ◽  
Mechanical Processing ◽  
Uniform Dispersion ◽  
Oxide Particles ◽  
Nickel Base

Currently there is a great interest in developing nickel base alloys with fine and uniform dispersion of stable oxide particles, for high temperature applications. It is well known that the high temperature strength and stability of an oxide dispersed alloy can be greatly improved by appropriate thermomechanical processing, but the mechanism of this strengthening effect is not well understood. This investigation was undertaken to study the dislocation substructures formed in beryllia dispersed nickel alloys as a function of cold work both with and without intermediate anneals. Two alloys, one Ni-lv/oBeo and other Ni-4.5Mo-30Co-2v/oBeo were investigated. The influence of the substructures produced by Thermo-Mechanical Processing (TMP) on the high temperature creep properties of these alloys was also evaluated.

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