Different Concentrations Of Ce Research Articles

Photoluminescence optical and thermal quenching in heavily doped Gd3(Ga,Al)5O12:Ce, Mg single crystals: Dependence on the Ga3+, Ce3+, and Mg2+ concentration

Heavily doped single crystals of Gd3GaxAl5-xO12:Ce, Mg (x = 2.46–2.95) with different concentrations of Ce (0.016–0.188 at.%) and Mg (0–0.083 at.%) are investigated by the X-ray diffraction, photoluminescence, and thermoluminescence methods. Dependences of the luminescence characteristics, as well as crystal lattice parameters and distances between the Ce3+ and Mg2+ ions, on the Ga, Ce, and Mg concentration are studied. Mechanisms of the processes, resulting in the photoluminescence optical and thermal quenching and acceleration of decay kinetics, and the influence of the crystal composition on these processes are discussed. The role of close {Ce3+ - Mg2+Ga} pairs in these processes is considered. At T > 400 K, the luminescence thermal quenching is caused by the crossover process, while in the 200–350 K temperature range, by the electron transfer from the 5d1 excited state of Ce3+ to nearby defect levels (electron traps) located between the 5d1 level and the conduction band. The latter process results also in the appearance of thermally stimulated luminescence, and its efficiency depends on the Ga3+ content and concentration of intrinsic defects. The optimum concentrations of Ga3+ and Mg2+ ions in the investigated crystals are determined.

Effect of Ce doping on electromagnetic characteristics and absorbing properties of M-type barium ferrite

In this study, Ce3+-doped M-type barium ferrite BaCexFe12-xO19 (x = 0 ∼ 1.2) was prepared by sol-gel method. The effects of Ce3+ doping on the crystal structure, microstructure, electromagnetic properties and absorption properties of M-type barium ferrites were investigated. The results indicate that the crystal structure remains unchanged with the increase of Ce3+ doping. The crystal size of Ce3+ doped barium ferrite is in the micro-meter range, and the grain size remains almost constant with increasing doping. The addition of Ce3+ to the BaFe12O19 samples resulted in significant improvements in their electromagnetic and microwave absorption properties. These improvements were mainly due to the synergistic effect of magnetic and dielectric losses. Among the samples doped with different concentrations of Ce3+, BaCe0.2Fe11.8O19 exhibited the best absorption performance, which has a minimum reflection loss of −58 dB and an effective absorption bandwidth of 9.44 GHz at a matched thickness of 2.3 mm. This study proposes an efficient electromagnetic wave absorber with a wider effective absorption bandwidth.

Luminescence Properties of Ce-Doped Di-Calcium Magnesium Disilicate Ca2MgSi2O7:4 mol%Ce

Dicalcium magnesium disilicate (Ca2MgSi2O7) doped with cerium rare earth ions has been examined for its optical and photonic characteristics and applicability for radiation dosimetry applications. Mono-calcium aluminate that has cerium added to it, has been shown to be an excellent dosimeter with a linear response up to roughly 4 kGy of radiation exposures. Maximum TL emission is achieved at 4 mol% cerium dopant concentration. The clearly visible two peaks that were detected at 381.13K and 566.87K can be used as a high-temperature dosimetry advance. In this study, we reported the preparation technique and luminescence properties such as TL, ML, and PL of Ce3+ doped dicalcium magnesium silicate phosphors. The phosphors were prepared by the solid-state reaction method. The TL glow curves were recorded for all different concentrations of Ce- doped phosphors.

Enhanced Photocatalytic Performance of TiO2@CeO2 Hollow Structure through Synergetic Surface and Interface Engineering

AbstractIn this study, a synergetic structural design is developed to improve the photocatalytic performance of the sub‐micro core–shell hollow sphere (TiO2@H‐CeO2). TiO2@H‐CeO2 with maximum surface/interface effect is chosen as the substrate and then reacts with different concentrations of Ce(NO3)3·6H2O solutions. Optical properties analysis shows that after the reaction, the band gap of the composite structure and the electron–hole recombination efficiency both decrease while the photodegradation ability is effectively improved. Spectroscopic and microscopic observations reveal two changes in the structure after the reaction. The first is the deposition of CeO2 nanoparticles that can be observed inside and on the surface of the shell; the second is the doping of Ce3+ in the TiO2 nanoparticles of this shell. The deposition of CeO2 particles increases the interfacial area between the CeO2 and TiO2 and facilitates the corresponding charge transfer. The Ce3+ doping in the TiO2 shell changes the optical properties of TiO2. Therefore, the improved performance of the composite structure can be attributed to the synergy of different surfaces and interfacial effects caused by the reactions.

Oxic effects of Pb-Ce compound pollution on Chinese cabbage and programmed cell death in root tip cells

Heavy metal pollution is increasing, and rare earth elements (REE) play an important role in the environmental impact of heavy metals. Mixed heavy metal pollution is a major issue with complex effects. Despite substantial research on single heavy metal pollution, relatively few studies have focused on pollution from rare earth heavy metal composites. We studied the effects of different concentrations of Ce–Pb on the antioxidant activity in root tip cells and biomass of Chinese cabbage. We also used the integrated biomarker response (IBR) to evaluate the toxic effects of rare earth-heavy metal pollution on Chinese cabbage. We used programmed cell death (PCD) for the first time to reflect the toxicological effects of heavy metals and rare earths and studied the interaction between Ce and Pb in root tip cells in depth. Our results showed that Ce–Pb compound pollution can induce PCD in the root cells of Chinese cabbage, and the toxicity of compound pollutants is greater than that of single pollutants. Our analyses also provide the first evidence that Ce and Pb exert interaction effects in the cell. Ce induces Pb transfer in plant cells. The Pb content in the cell wall decreases from 58% to 45%. Additionally, Pb induced Ce valence changes. Ce (III) decreased from 50% to 43%, while Ce (IV) increased from 50% to 57%, directly resulting in PCD in the roots of Chinese cabbage. These findings improve our understanding of the harmful effects of compound pollution with rare earth metals and heavy metals on plants.

Trace Ce addition for inhibiting Bi segregation induced embrittlement in ultrahigh-purity copper

Bismuth (Bi), as an impurity element in copper and copper-based alloys, usually leads to the catastrophic intergranular fracture even with a ppm concentration. However, the intrinsic mechanisms of the embrittlement remain largely unclear and the control of such a brittleness has been rarely reported. Here, we investigate the influence of trace amounts of Bi on the ductility of ultrahigh-purity copper (99.99999%) at temperatures between room temperature (RT) and 900 °C. On this basis, the ductility improvement of CuBi alloy by adding different concentration of Ce is also systematically studied. Compared to the ultrahigh-purity copper, the Bi-containing alloy exhibits a remarkable decrease in ductility, with the severe reduction occurs at 450–900 °C. This is caused by the grain boundary (GB) segregation of Bi layers, which reduces the GB cohesion because of the weak BiBi bonds. However, after trace Ce are added, the ductility of CuBi alloy in the temperature range of 450–900 °C is significantly increased. The obvious enhancement is due to the reaction behavior of Ce and Bi to form the precipitated phases, as well as the preferential segregation of Ce to GBs and phase boundaries, which change the existing form of Bi in copper. Our findings provide a comprehensive understanding on the microstructural origin of Bi-induced GB embrittlement and an effective way for inhibiting such an embrittlement.

DEVELOPMENT OF RADIATION RESISTANT SCINTILLATORS BASED ON RARE-EARTH ALUMINATES

LuYAG:Ce and YAG:Ce,Ca crystals were obtained by the Czochralski method using tungsten crucibles in reducing surroundings. Crystals (LuxY1-x)3Al5O12:1%Ce and crystals of YAG:Ce,Ca with different concentrations of Ce and Ca were grown. Studies and analyses of their characteristics were carried out. The analysis of their characteristics is based on experimental data that we obtained by measurements of light output, decay time, spectra of luminescence, excitation, and light transmittance.

Effects of Ce(NO3)3 concentration on microstructure and properties of plasma electrolytic oxidation layer on 6061 alloy

Plasma electrolytic oxidation treatment of 6061 Al alloy was carried out in a sodium silicate and sodium hydroxide alkaline electrolyte containing different concentrations of cerium nitrate (Ce (NO3)3) under constant current mode. The effects of Ce (NO3)3 concentration on the roughness, cross section and surface morphology, composition and phase composition, adhesion force and corrosion resistance of the prepared layer were studied by means of true color microscope, scanning electron microscope, x-ray energy spectrometer, x-ray diffractometer, micrometer scratcher and electrochemical workstation. The results show that with the increase of Ce(NO3)3 concentration in the electrolyte, the thickness of the plasma electrolytic oxidation layer increases gradually, and the micropores and cracks increase, and the roughness increases first and then decreases. The plasma electrolytic oxidation layers under different concentrations of Ce (NO3)3 are mainly composed of α-Al2O3, γ-Al2O3 and a small amount of Al2SiO5. The Ce element in the layer is mainly present in the form of a mixture of Ce(OH)4, CeO2 and Ce2O3.The increase of Ce (NO3)3 concentration reduces the binding strength between the plasma electrolytic oxidation layer and the matrix, increases the self-corrosion potential, decreases the self-corrosion current, and weakens the corrosion resistance. The layer with a concentration of 0.25 g l−1 Ce (NO3)3 has less micropores and cracks, and has the better compactness. The bonding strength between the layer and the substrate is 27 N, the corrosion current density is 3.42 × 10−9A cm−2 and corrosion potential is −0.72 V, the best bonding strength and corrosion resistance is presented.

Spectroscopic and luminescent properties of Ce3+ -doped TeO2-WO3-GeO2 glasses

Different concentrations of Ce3+-doped TeO2-WO3-GeO2-Ce2O3 (TWGCe) glasses were prepared by melt-quenching method and characterized. Different spectroscopic and luminescence properties were evaluated using room temperature absorption and emission spectra. The absence of sharp X-ray diffraction peaks and the presence of broad band from 18° to 35° shows the amorphous phase of studied glasses. The Fourier transform infrared absorption spectra show the presence of various vibrational bonds. The optical properties of TWGCe glasses were studied by exciting the glass samples at 323 nm ultraviolet wavelength. The quenching in luminescence is noticed at × = 0.5 mol% along with a red-shift at higher Ce3+ concentrations. The decay time was found decrease with increase of concentration of Ce3+ ions. These glasses emit intense blue luminescence with CIE coordinates (0.161, 0.018) when excited at 323 nm radiation. These glasses are favourable as blue light sources in the design of phosphor-based white LEDs.

Enhancement of up-conversion luminescence through doping Ce3+ ions in YbxEr2−xTi2O7 thin films

Lanthanide-doped up-conversion nanomaterials have great potential applications in solar cells, color displays, biomedical imaging. In this work, high-quality Yb3+/Er3+/Ce3+ co-doped YbxEr2−xTi2O7 thin films were fabricated by pulsed laser deposition. The morphology and up-conversion luminescence of YbxEr2−xTi2O7 thin films with different concentrations of Ce3+ ions were systematically studied. More than 3-fold enhancement of up-conversion emission was obtained via 7.5% Ce3+ ions doping, which may be attributed to cross-relaxation processes and a destruction of local crystal field. The enhancement mechanism of up-conversion emission was investigated in detail.

Effect of Rare Earth on the Corrosion Resistance of Electroless Ni-Mo-P Composite Coatings

A kind of corrosion-resistant Ni-Mo-P composite coating was deposited on the surface of AZ91D magnesium alloy substrate by electroless plating method with different concentration of Ce(NO3)3 and Nd(NO3)3. The deposition mechanism of Ni-Mo-P composite coating was explored. Furthermore, the effects of Ce(NO3)3 and Nd(NO3)3 concentration on the microstructure and properties of Ni-Mo-P composite coatings were studied. Results indicated that the Ni-Mo-P composite coatings prepared by adding the optimal concentration of Ce(NO3)3 and Nd(NO3)3 had few defects. Meanwhile, the deposition rate of the composite coatings and the adhesion between the coating and the magnesium alloy substrate were improved. When the concentration of Ce(NO3)3 and Nd(NO3)3 were 0.10 and 1.00 g/L, the Ni-Mo-P composite coatings had the minimum corrosion rate of 0.826 and 0.681 g/m2·h, respectively. Herein, compared with the addition of Ce(NO3)3, the Nd(NO3)3 added Ni-Mo-P composite coating has the maximum arc radius of capacitive resistance and significant improvement corrosion resistance.

Impact of the Synthesis Method on the Conventional and Persistent Luminescence in Gd3-xCexGa3Al2O12.

The series of Gd3–xCexGa3Al2O12 nanopowders doped with different concentrations of Ce3+ ions were prepared by Pechini (sol–gel) and combustion methods. The structure and morphology of the powders were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. It was found that the synthesis method has a great impact on the morphology and, consequently, spectroscopic properties of the powders. Optical properties of the powders were examined using excitation, emission, and luminescence kinetic measurements. For all powders, persistent luminescence and emission decay processes were studied. The most intense luminescence was observed for the powder with 0.5 mol % of Ce3+ synthesized using the combustion method and 1 mol % in the case of the sol–gel sample. The longest and brightest persistent luminescence was observed for the powders doped with 0.1 mol % (combustion) and 0.2 mol % of Ce3+ ions (sol–gel). The thermoluminescence measurements were done for the powders prepared using different methods to understand the impact of the synthesis conditions on the number and depths of the traps involved in persistent luminescence. On the basis of spectroscopic measurements, the mechanism of persistent luminescence was constructed and discussed.

NiAlCe mixed oxides obtained from layered double hydroxides applied to anisole hydrodeoxygenation

Bio-oil derived from the pyrolysis of lignocellulosic biomass residues cannot be used directly as biofuel due to the high content of oxygenated compounds. As an alternative, bio-oil must undergo a deoxygenation process, such as catalytic hydrodeoxygenation (HDO). In this sense, this work studied the effect of different concentrations of Ce3+ and Ce4+ in layered double hydroxides (LDHs) in order to obtain mixed oxide catalysts containing NiAlCe (NiO-NiAl2O4-CeO2) with low cost and high performance for the hydrodeoxygenation of anisole as a model bio-oil compound. Mixed oxides were obtained from the thermal decomposition of layered double hydroxides (LDHs) by using terephthalic acid as compensation anion, with molar ratio: Ni2+/(Al3++ M) = 1.0, where M = Ce3+; Ce4+ or Ce3+-Ce4+; and Al/Ce ratios of 9 and 1. Characterization analyses confirmed the formation of LDHs for all materials, although at lower Al/Ce ratio it is observed a loss of crystallinity, due to a greater repulsion and distortion of the layer structure caused by the incorporation, in greater amount, of cations with a high ionic radius. The increase in the content of cerium in mixed oxides also led to an increase in the acidity of the catalysts, in addition to a reduction in the surface area, justified by the pore blockage by CeO2 on the catalyst surface. The greater structural and thermal stability was evidenced in the LDHs derived from Ce4+, as well as a greater dispersion of the NiO phase in the corresponding mixed oxides, and therefore presenting greater anisole conversion. The obtained data indicated that the presence of Ce4+ ions on the catalyst surface was decisive in the conversion of anisole to cyclohexane, the main deoxygenated product, obtained via the direct deoxygenation and hydrogenation mechanism.

Rapid synthesis of Ce3+:YAG via CO2 laser irradiation combustion method: Influence of Ce doping and thickness of phosphor ceramic on the performance of a white LED device

A new, rapid method was reported to produce Y3Al5O12 phosphors doped with different concentrations of Ce3+ (YAG:Ce3+) within 1.5 ​min via continuous-wave CO2 laser irradiation, in which a CO2 laser is utilised as the combustion source. X-ray powder diffraction confirmed the formation of pure cubic phase in the as-synthesised powder. Thus, laser irradiation plays an important role in optimising reaction kinetics to obtain high-quality crystal with high luminescence intensity. Furthermore, the incorporation of Ce3+ ions into the YAG matrix can be enhanced through sintering powders at 1050 ​°C for 5 ​h. Optical properties were examined comparatively using photoluminescence emission. Additionally, the performance of white light-emitting diode (LED) can be regulated easily by altering the Ce3+ doping concentration and YAG:Ce3+ layer thickness on blue InGaN LED chip. Excellent white light, which has a CIE coordinate of (0.31, 0.36) that approached the standard WLED values, a colour rendering index of about 69.4, a correlated colour temperature of about 6299 ​K and a luminous radiation efficiency exceeding 169 lm/W, was obtained for YAG doped with 2 ​mol% Ce concentration with a coating layer thickness of 1 ​mm.

High-performance Al2O3–Ce:YAG ceramics for white LED and LD by the optimization of Ce3+ concentration

Al 2 O 3 –Ce:YAG composite ceramics are widely used in high-power white light-emitting diodes (LED) and laser diode (LD), because of their good optical performance and high luminous efficiency, particularly, excellent thermal conductivity. In this study, we prepared Al 2 O 3 –Ce:YAG composite ceramics doped with different concentrations of Ce 3+ by vacuum sintering technique. The emission peak of Ce 3+ is redshifted from 533 nm to 553 nm with the increase of Ce 3+ concentration from 0.1 at% to 1.5 at%. When excited by a blue LED with 455 nm, the luminous efficiency of the ceramic doped with 1.2 at% Ce 3+ reached 106 lm/W and a low correlated color temperature of 3600 K was achieved. Moreover, when excited by the 450 nm blue LD with 5.8 W of electrical power, a higher luminous efficiency of 171 lm/W was obtained with 0.5 at% Ce 3+ doped. These results indicate that Al 2 O 3 –Ce:YAG composite ceramics doped with Ce 3+ concentrations of 1.2 at% exhibit excellent optical properties and are promising phosphor-convert materials for white LED and LD lighting applications. • Al 2 O 3 –Ce:YAG composite ceramic phosphors with different Ce 3+ concentration have been fabricated . • The emission peaks are redshifted from 533 nm to 553 nm with the increase of Ce 3+ concentration from 0.1 at% to 1.5 at%. • When the Ce 3+ concentration was 1.2 at%, the composite ceramic reached the highest luminous efficiency of 106.45 lm/W. • The optical properties of the composite ceramics were also tested when installed on LD.

Effect of the Ce3+ concentration on laser-sintered YAG ceramics for white LEDs applications

This paper describes the laser sintering and luminescence properties of Y3Al5O12 (YAG) phosphors doped with different concentrations of Ce3+ and synthesized using the polymeric precursor method. The ceramics were sintered by a new laser sintering technique in which a CO2 laser is employed as the heating source. The resultant ceramics exhibited a homogeneous microstructure with narrow grain size distribution and high relative density. The introduction of Ce3+ ions led to luminescence quenching at a concentration above 0.5 mol% and a redshift of the emission spectrum band with increasing cerium concentration. The excitation spectrum showed two characteristic bands centered at 340 nm and 460 nm and a relative change in their intensity by change the Ce3+ concentration. The presence of a single valence (Ce3+) of cerium was determined by X-ray absorption near edge structure measurements.

Luminescence and scintillation characteristics of Cs3ScCl6:Ce crystals

In this study, we fabricated Cs3ScCl6 crystals doped with different concentrations of Ce and investigated their luminescence properties. In both the photoluminescence (PL) and scintillation spectra, emission bands attributable to Ce3+ 5d–4f transition were observed. The PL temporal profiles revealed decay time constants of ~35 ns, which are typical values for Ce3+ 5d–4f transition. In the scintillation temporal profiles, two decay components were observed. The fast and slow components could be attributed to Ce3+ 5d–4f luminescence and self-trapped excitons (STEs) or a slow energy transfer from STEs to Ce3+, respectively. The maximum light yield was 9200 photons/MeV for a Ce concentration of 0.5 mol%.

Photoluminescence and scintillation properties of Al(PO3)3–CeCl3–CsCl–CsPO3 glass scintillators

The photoluminescence (PL) and scintillation properties of Al(PO3)3–CsPO3–0.5CsCl–xCeCl3 (x = 0.05, 0.1, 0.2, 0.3, 0.5) glass scintillators were analyzed. Glasses with different concentrations of Ce3+ were fabricated via the melt-quenching method under vacuum. The X-ray diffraction patterns of all the samples except those with x = 0.3 and 0.5 presented only halo features and no sharp diffraction peaks, indicating a crystalline structure and, in turn, the amorphous nature of the glasses. The PL emission and X-ray-induced radioluminescence spectra presented a fluorescence band at ~ 350 nm, which were attributed to allowed transition from the Ce3+ 5d excited state to the 4f ground levels (2F5/2 and 2F7/2). The PL and scintillation decay time were estimated to be ~ 35 ns. The glass scintillators with x = 0.3 exhibited the maximum light yield, which was approximately 2100 photons/MeV.

Tunable red-to-green emission ratio and temperature sensing properties of NaLuF4:Ho3+/Yb3+ microcrystals by doping with Ce3+ ions

In this work, β-NaLuF4:20Yb3+/2Ho3+ samples with different concentrations of Ce3+ ions are obtained by a hydrothermal method.

The effect of cerium cation on the microstructure and anti-corrosion performance of LDH conversion coatings on AZ31 magnesium alloy

The compact layered double hydroxide (LDH) coatings, containing Mg2+ and Ce3+ as a bi- and trivalent metal cation, were prepared on AZ31 substrate by a combined co-precipitation and hydrothermal processing method for the first time. To investigate the effect of Ce ions on the deposition of the suitable coating on AZ31, the LDHs with different concentration of Ce were synthesized. In addition, the synthesized coatings were investigated by XRD, FTIR, SEM and TEM. Potentiodynamic polarization and EIS measurements were conducted to compare the corrosion behaviors of the coatings. The finding of this study proves that a compact coating with two kinds of the structure is successfully produced. The coating is highly appropriate for the protection of AZ31 magnesium alloy.