Rare-earth ions

Top PDF Rare-earth ions:

Photoluminescence studies in rare earth ions coordinated by a carbazolic derivative.

Photoluminescence studies in rare earth ions coordinated by a carbazolic derivative.

Para o complexo de Gd 3+ , as curvas de intensidade de emissão do ligante em função do tempo foram ajustadas a decaimentos biexponenciais, indicando que o Gd 3+ pode estar [r]

6 Ler mais

Quím. Nova  vol.21 número3

Quím. Nova vol.21 número3

quenching is caused by residual water, solvents, and silanol groups present in sol-gel glasses and leads to an enhancement of non-radiative decay pathways of rare earth ions. Dopant clustering is deleterious because it leads to concentration quenching of luminescence through cross-relaxation and energy transfer processes. In previous work, it was shown a method for detecting rare earth clustering in sol-gel glasses based on Eu 3+ fluorescence line narrowing spectroscopy 9 .

4 Ler mais

Optical characterization of europium-doped indium hydroxide nanocubes obtained by Microwave-Assisted Hydrothermal method

Optical characterization of europium-doped indium hydroxide nanocubes obtained by Microwave-Assisted Hydrothermal method

semiconductors to increase PL. Europium in its trivalent state is one of the most studied among rare earth ions by luminescence spectroscopy due to the simplicity of its spectra and wide application as red phosphor in color TV screens. This ion has also attracted significant research attention due to its potential application as biological sensors, phosphors, electroluminescent devices, optical amplifiers or lasers when used as doping in a variety of materials 10,11 . Dutta et al. 12 showed Eu 3+ and Dy 3+ doped

7 Ler mais

Quím. Nova  vol.26 número6

Quím. Nova vol.26 número6

A point that should be stressed here is that, in contrast with a common procedure found in the literature in the case of rare earth- doped glasses, the dynamic coupling mechanism cannot, in any circumstances, be neglected. When the Ω λ intensity parameters are phenomenologically determined from experimental intensities, the forced electric dipole and dynamic coupling mechanisms are absorbed simultaneously and cannot be distinguished. Therefore, when treating energy transfer processes between rare earth ions, one should bear in mind that in the dipole-dipole or dipole- quadrupole expressions for the transfer rates the Ω λ ’s which appear refer only to the forced electric dipole contribution, that is, Ω λ ed . This is one of the reasons that
Mostrar mais

7 Ler mais

EPR linewidth of local magnetic moments diluted in Ce intermediate-valence compounds

EPR linewidth of local magnetic moments diluted in Ce intermediate-valence compounds

lations must consider the energy transfer between the im- purity spin S, the spin of the host rare-earth ions (Ce), the spins of the conduction electrons as well as the lattice, in the p[r]

4 Ler mais

Matéria (Rio J.)  vol.19 número4

Matéria (Rio J.) vol.19 número4

The rare earth luminous fiber has been increasingly used as functional fibers for technical textiles such as decorations, protections and medical textiles etc. The rare earth ions such as Sm (III), Eu (III), Tb (III), Dy (III) possess good fluorescence properties due to their special structural characteristics [1-4]. Chelating the amidoxime fibers with rare earth ions can produce amidoxime/Europium (ІІІ)-chelated complex (AECC) fibers which have excellent light-emitting intensity, good mechanical properties, and can free from harmful radiation [5,6]. They can absorb ultraviolet or visible light for ten minutes, and then can emit light continually for more than ten hours after removal of excitation resource [7, 8]. Such functional fibers can be used for technical textiles such as decorations, protections and medical textiles etc [5, 9-11]. However, few studies have been found about using chelating reaction method to fabricate AECC fibers.
Mostrar mais

8 Ler mais

Mat. Res.  vol.19 número5

Mat. Res. vol.19 número5

at selected wavelengths could be obtained by altering the doping concentration in the triple-doped sample. Based on the CIE coordinates, it could be inferred that double-doped Gd 2 O 3 with the composition Tb = 0.05% and Dy = 1.95 mol%, when excited at 247 nm, emits white light, which is closest to the standard noon daylight. Hence, it can be inferred that by altering the doping content of the rare-earth ions in a suitable host lattice like Gd 2 O 3 , it is possible to achieve desired emission colors.

7 Ler mais

Braz. J. Phys.  vol.37 número4

Braz. J. Phys. vol.37 número4

Borate glass is a particularly suitable optical material be- cause of its high transparency, low melting point, high ther- mal stability, different coordination numbers, and good sol- ubility of rare-earth ions [5–6]. Further, heavy metal oxide glasses have reduced phonon energy. Thus, the incorporation of heavy metal oxides such as PbO or Bi 2 O 3 into the borate

8 Ler mais

Surface-plasmon-enhanced frequency upconversion in Pr(3+) doped tellurium-oxide glasses containing silver nanoparticles

Surface-plasmon-enhanced frequency upconversion in Pr(3+) doped tellurium-oxide glasses containing silver nanoparticles

The study of glasses doped with rare earth ions are of significant interest due to their potential applications in many optical devices. 1–3 Specifically, heavy metal oxide 共HMO兲 glasses doped with trivalent rare earth ions are very impor- tant because they show strong luminescence due to their small cutoff phonon frequencies. 1 However, in order to make devices with enhanced optical characteristics, the concentra- tion of rare earth ions has to be low enough so that lumines- cence quenching is minimized. It is also possible to prevent the quenching effect by modifying the environment felt by the luminescent ions. 4–6 Therefore, glasses containing metal- lic nanoparticles doped with low concentration of rare earth ions are of particular interest because the large local field acting on the ions positioned near the nanoparticles may in- crease the luminescence efficiency when the optical fre- quency of the excitation beam and/or the luminescence fre- quency are near resonance with the surface plasmon frequency of the nanoparticles. 7
Mostrar mais

5 Ler mais

Rare Earth Elements and Geochemical Partitioning of Zn and Pb in Sediments of an Urban River

Rare Earth Elements and Geochemical Partitioning of Zn and Pb in Sediments of an Urban River

Abstract: Problem statement: Urban river sediment pollution due to Zn and Pb is a serious problem in all over the world. The source and level of Zn and Pb pollution in sediments of Nomi River of Ota Ward, one of the most industrialized areas in Tokyo, Japan is still lacking. Approach: The present study focused on Rare Earth Elements (REEs) and geochemical partitioning of Zn and Pb in sediments of 19 sampling sites of Nomi River in order to examine the mobility pattern. The amounts of Zn and Pb in the liquid extract of 5 (five) geochemical phases were measured by using Inductively Coupled Plasma Mass Spectrometry (ICP-MS) and the concentrations of REEs in sediments were determined by using X-ray Fluorescence Spectroscopy (XRF). Results: Speciation data indicate dominant labile fraction of Zn, which is related to the presence of several anthropogenic influence of the investigated area. Enrichment Factor (EFc) and Index of geoaccumulation (I geo ) value were compatible with the
Mostrar mais

10 Ler mais

Mat. Res.  vol.15 número4

Mat. Res. vol.15 número4

On-line ultrasonic velocity measurement as a function of temperature determines the T c in perovskites. T c that is observed with a decrease in the ionic radii of the rare earth elements decreases as observed by other studies such as conductivity. Thus, it is concluded that an on-line ultrasonic velocity/attenuation measurement is one of the best tools to explore the structural/phase transition in perovskites as a function of the ionic radii of rare earth elements.

5 Ler mais

Nitrenium ions.

Nitrenium ions.

A explicação mais provável para estes re- sultados é que no primeiro caso, o par de elétrons não comparti- lhado do nitrogênio está conjugado com a carbonila do grupo amida, possibilitan[r]

6 Ler mais

Carbonium ions.

Carbonium ions.

Os dois principais tipos de carbocátions são os íons carbênio, que possuem uma estru- tura planar com hibridização sp 2 no carbono catiônico e um sexteto eletrônico, e os íons carbônio,[r]

8 Ler mais

Mat. Res.  vol.12 número2

Mat. Res. vol.12 número2

Comparison of the effects produced by the different additives revealed that the highest densification and Vickers hardness results were obtained in samples containing Al 2 O 3 and La 2 O 3 . The use of two rare earth oxides simultaneously as sintering additives in combination with a lower alumina content increased the fracture toughness of the silicon nitride-based ceramics. The influence of the intergranular phase composition on fracture toughness of silicon nitride-based ceramics was also evaluated.

6 Ler mais

Mat. Res.  vol.17 número1

Mat. Res. vol.17 número1

Lead titanate ceramics modiied with 10 and 15 mol% of a natural mixture of rare earth oxide of xenotime were prepared by conventional technique and the samples obtained were dense and free of cracks ceramic bodies. PXT compositions show low relative dielectric permittivity and high Curie temperatures, compared to others based PbTiO 3 ceramics compositions, features that are important to produce piezoelectric devices for operate at high frequencies and high temperatures.

6 Ler mais

Brazil. J. Polit. Econ.  vol.37 número3

Brazil. J. Polit. Econ. vol.37 número3

China’s decision to control rare earth exports marks a turning point in the international supply of these raw materials, as well as in the division of labor be- tween China and more advanced countries in renewable energy, defense, and other high-tech areas. The US was once the world’s largest producer of REEs, but Chine- se competition, as well as pollution caused by rare earth mining and processing, led to mine closures in the US and other countries. As a result, Chinese producers took over the world market. By 2005, their share of global production had reached 95%. China assumed this dominant position just as world REE demand was increa- sing with the proliferation of applications in consumer electronics, weapons systems and green technologies. Much of this demand increase took place within China itself. Between 2000 and 2007, China, once little more than an exporter of rare earth ores and concentrates, became a large manufacturer of high-tech magnets, wind turbines and other rare earth-dependent products. In 2000, China exported over 90% of its REE output, mainly to the US, the EU and Japan. By 2012, it was shipping abroad less than 20% of its output.
Mostrar mais

23 Ler mais

J. Braz. Chem. Soc.  vol.28 número10

J. Braz. Chem. Soc. vol.28 número10

The aim of this study was to determine the sixteen rare earth elements (REEs) in twelve types of popular flower herb teas and their infusions consumed in China. Microwave-assisted acid digestion was used for all of the samples, and the contents of these elements were determined by inductively coupled plasma mass spectrometry (ICP-MS). The concentrations of REEs varied from 94.6 to 7492 µg kg -1 among these flower samples. Ce was the most abundant elements in all

6 Ler mais

Rev. Esc. Minas  vol.68 número4

Rev. Esc. Minas vol.68 número4

The tests had as their main objec- tive to verify the best conditions for the separation of LREE from other rare earth elements in a synthetic liquor. The quantitative analysis was performed for the elements La, Pr, Nd and Sm. Sm was used as a reference for the separation between light and heavy elements. In the case of the pilot plant, Gd was also ana- lyzed. It was considered that the elements of atomic number higher than Gd were 100% removed.

8 Ler mais

J. Braz. Chem. Soc.  vol.16 número6A

J. Braz. Chem. Soc. vol.16 número6A

The purification procedure can be scaled up to semi- industrial level. This simplifies the achievement of pure RE elements fractions without the trouble of recovering EDTA from the processes that use the retaining ion (Cu- EDTA and Zn-EDTA complexes), as widely mentioned in the literature. The authors describe in this paper a method successful for the purification of Rare Earths by ion exchanger chromatography without the use of a retaining ion.

4 Ler mais

Braz. J. Phys.  vol.40 número3

Braz. J. Phys. vol.40 número3

age current. The properties of grown film and interface show a pronounced dependence upon the deposition process and the precise deposition parameters. Many techniques such as chemical vapor deposition, atomic layer deposition, sol- gel techniques, electron beam deposition etc. are used to deposit thin films on the aforementioned rare earth oxides. Each technique has their own set of advantages and disad- vantages. However, most of these techniques show some or other kind of interface damage [13]. Sputtering and e-beam assisted depositions create radiation induced surface damage during film growth. Thermal evaporation is a well known technique that does not produce any kind of surface damage [13,14]. Because this technique is a rather gentle process it creates very little or no damage to the interface [13].
Mostrar mais

4 Ler mais

Show all 2899 documents...