Ce Powder Research Articles

Effect of Ga/Al ratio on the luminescent properties of inorganic scintillating GGAG:(4 mol%)Ce ceramic powder

Gadolinium gallium aluminum garnet doped with cerium (GGAG:Ce), a promising ceramic scintillator material, is being excessively explored for its high quality optical properties by the bandgap engineering with different Ga/Al ratio. In this study, GGAG:Ce powders were synthesized using a solvothermal method and sintered at 1300 °C to investigate the impact of the gallium-to-aluminum (Ga/Al) ratio on optical characteristics. The results revealed that a decrease in the Ga/Al ratio led to a decrease in particle size. This observation can be attributed to the different reactivity and growth kinetics of gallium and aluminum precursors during the solvothermal process. Perturbations from the optimized Ga/Al ratio of 1.5–1.77 and 1.27 resulted in substantially enhanced photoluminescence (PL) and radioluminescence (RL) spectra intensities. PL lifetime measurements of various Ga/Al ratio exhibit average PL lifetime between 48 and 57 ns. Specifically, the deviations to 1.77 and 1.27 ratios yielded approximately 125 % and 106 %, respectively, in observed luminescent measurements compared to other ratios. This enhancement in PL and RL intensity suggests that the Ga/Al ratio plays a critical role in modulating the optical properties of GGAG:Ce ceramic powders. The results of this study also highlight the importance of the Ga/Al ratio in tailoring the optical or luminescence characteristics of GGAG:Ce powders.

Microstructures and properties of Pr,Ce:Gd2O2S ceramics fabricated from powders synthesized at different initial water bath temperatures

Crystallized precursor with stacked layered was synthesized in hot water bath using oxide powders and concentrated sulfuric acid as raw materials. Gd2O2S powders with high phase purity were obtained by reducing the precursor under flowing hydrogen atmosphere. The influence of initial bath temperature of Gd2O3 and H2SO4 on the microstructure of Gd2O2S powders was investigated. The Gd2O2S:Pr,Ce powders showed a stacked layered structure and as the initial water bath temperature increases, the particle size of the flaky powders also increases. Using the synthesized powders, Gd2O2S:Pr,Ce scintillation ceramics were fabricated through pre-sintering in vacuum followed by HIP post-treatment in argon atmosphere. The Gd2O2S:Pr,Ce ceramics fabricated from the powders synthesized at lower initial water bath temperature show a rapid densification rate during pre-sintering. The Gd2O2S:Pr,Ce ceramic sample fabricated from powders synthesized at 7°C showed the highest optical transmittance, XEL intensity, and light yield value of 25,800 ph/MeV @ 662 keV γ rays. The PL decay time of Pr3+3P0→3H4 transition was measured to be ∼2.87 μs for all ceramic samples. The effect of the initial water bath temperature on optical transmittance and light yield of Gd2O2S:Pr,Ce ceramics was also discussed.

Liquid-phase synthesis and luminescence properties of Gd2O2S:Pr,Ce nanophosphors from a novel sulfur source

Gd2O2S:Pr,Ce nanophosphors have been prepared by liquid-phase method using NH2SO3H as the sulfur source for the first time. The formula of the novel precursor was determined as Gd2(OH)x(NH2SO3)6-x∙nH2O by EDS, TG-DSC and FT-IR spectroscopy, and the precursor exhibited an amorphous structure and lamellar morphology as deduced from XRD and SEM. The optimum pH was 8 and the optimum calcination temperature was 1000 °C for the preparation of Gd2O2S:Pr,Ce from the precursor. The PL quantum yield and the fluorescence lifetime of Gd2O2S:Pr,Ce powder was 53.62 % and 2.48 μs respectively, which will allow the preparation of ceramic scintillators with high optical output and energy resolution. Compared to the traditional sulfur sources such as sublimed sulfur, and H2SO4, NH2SO3H is harmless and avoids pollution gases during the preparation of Gd2O2S:Pr,Ce nanophosphors. It also eliminates the need to add additional reagents, simplifying the preparation steps and reducing production costs.

Effects of rapid solidification and Ce on the microstructure of Al–40Si

ABSTRACT This work explores the use of Ce and rapid solidification to attain primary Si modification in a hypereutectic Al-40wt-%Si alloy. Al–40Si and Al–40Si–1.5Ce powders were produced by Impulse Atomization. The resulting powders having increasing liquid cooling rate from ∼103 to ∼105 K/s were studied to determine the effect of Ce on the microstructure. The microstructures of both alloys contained an Al-rich halo (α-Al) which is not part of Gulliver-Scheil solidification paths. The presence of this structure suggests solidification of both alloys deviated from local equilibrium. In both alloys, increasing cooling rate was associated with the formation of less elongated primary Si presenting a more rounded surface. Additionally, alloying with Ce improved the distribution of primary Si in the microstructures of the smallest powders. Quantitatively, the microstructures of both alloys were found to increase in primary Si and halo (α-Al) content as cooling rate increases. The use of Ce also led to a measurable decrease in eutectic content in Al–40Si–1.5Ce with respect to the unmodified alloy. Similarly, primary Si and halo (α-Al) vol.-% also appear to increase as a result of Ce addition.

Beta particle excited thermoluminescence of new ZnO:Ce phosphors

This work reports on the beta particle excited thermoluminescence (TL) of ZnO:Ce phosphors, synthesized through a controlled chemical precipitation reaction followed by thermal annealing at 900 °C in an air atmosphere during 24 h. The successful obtention of crystalline hexagonal zincite structure was confirmed by X-Ray diffraction. By milling ZnO:Ce powder precipitated during the reaction before carrying out the thermal annealing, there are improved reproducibility and enhanced TL features of interest for dosimetry. Ce doping strongly increases the TL sensitivity and leads to a simpler glow curve shape. The TL – dose response exhibits a linear behavior at least up to 128 Gy. The sensitivity of the synthesized ZnO:Ce is ca. 103 times greater than that of undoped ZnO. The TL fades 22% two days after radiation exposure, and then it becomes negligible.

Low energy X-ray dosimeter based on LYSO:Ce fluorescent powder.

Cerium-doped lutetium yttrium orthosilicate (LYSO:Ce) powder has been synthesized by the co-precipitation method. The influence of the Ce3+ doping concentration on the lattice structure and luminescence characteristics of LYSO:Ce powder was investigated by X-ray diffraction (XRD) and photoluminescence (PL). The XRD measurement indicates that the lattice structure of LYSO:Ce powder was not changed by doping ions. PL results show that LYSO:Ce powder has better luminescence performance when the Ce doping concentration is 0.3mol%. In addition, the fluorescence lifetime of the samples was measured, and the results show that LYSO:Ce has a short decay time. The radiation dosimeter was prepared by LYSO:Ce powder with a Ce doping concentration of 0.3mol%. Radioluminescence properties of the radiation dosimeter also were studied under X-ray irradiation at doses from 0.03 to 0.76Gy, with dose rate from 0.09 to 2.284Gy/min. The results show that the dosimeter has a certain linear relationship response and stability. The radiation responses of the dosimeter at different energies were obtained under X-ray irradiation with X-ray tube voltages ranging from 20 to 80kV. The results show that the dosimeter has a certain linear relationship response in the low energy range of radiotherapy. These results indicate the potential application of LYSO:Ce powder dosimeters in remote radiotherapy and online radiation monitoring.

Cerium-activated non-basal slip improves ductility of magnesium alloy

Biodegradable magnesium (Mg) possesses satiable elastic modulus and favorable biocompatibility, but poor plasticity limited its clinical application in bone repair field. In this work, rare-earth cerium (Ce) was introduced in Mg powder via mechanical alloying (MA). Under sustainable impact of huge compelling force, the Mg and Ce powders welded together and generated much crystal defects, which reduced the energy barrier of solute atom diffusion, thus obtaining Mg-Ce supersaturated solid solution powder. Afterwards, the MA-processed powder was shaped into parts by powder metallurgy. The supersaturated Ce weakened the texture and triggered<c+a> dislocation on pyramidal planes, which accelerated the cross-slip of dislocation and gave birth to sufficient slip system during deformation. As a result, the Mg-Ce/MA part showed a high ductility with elongation of ∼18.1%. In addition, the in vitro cell testing showed that Ce addition exerted no obvious negative effect on the biocompatibility. This work showed the feasibility of MA and powder metallurgy in fabricating high performance RE-Mg alloy towards to future biomedical application.

Synthesis of Y3Al5O12:Ce Powders for X-ray Luminescent Diamond Composites

A concentration series of Y3Al5O12:Ce solid solutions were prepared, and the composition demonstrating the highest X-ray luminescence intensity of cerium was identified. Based on the best composition, a series of luminescent diamond–Y3Al5O12:Ce composite films were synthesized using microwave plasma-assisted chemical vapor deposition (CVD) in methane–hydrogen gas mixtures. Variations in the amounts of the embedded Y3Al5O12:Ce powders allowed for the fine-tuning of the luminescence intensity of the composite films.

High time and energy resolution semi-transparent scintillation detectors for application in [formula omitted] optics and Mössbauer spectroscopy

Recently, phenomena as a quantum entanglement, Raabi oscillations, a stimulated emission etc. have been expanded into short wavelengths, namely X-rays and the γ radiation. However, this brings new requirements for detection systems, especially for their time resolution and energy selectivity. In this article, two partially transparent scintillation detectors for the characterization of a gamma-photon beam are presented. The first detector is a partially transparent scintillation detector with the time resolution less than 10ns. The second detector is a partially transparent scintillation detector utilizing Mössbauer effect with the energy selectivity up to 20.2neV. The unique design of these detectors is possible due to the use of the YAP:Ce powder, which allows the preparation of the custom-shaped scintillators with tunable absorption properties. Using these detectors together in synergy makes them a comprehensive tool for the characterization of gamma photons both in the energy and time domain.

Luminescence and photoconversion properties of micro-powder phosphors based on the Ce3+ and Mn2+ doped Ca2YMgScSi3O12 silicate garnets

This work is dedicated to study the synthesis processes and luminescence properties of micro-crystalline powder phosphors of Ce3+ and Mn2+ doped Ca2YMgScSi3O12 garnets (CYMSSG:Ce and CYMSSG:Ce,Mn) The photoluminescence emission spectra and decay kinetics confirm the formation of Ce3+ multicenters in the CYMSSG:Ce powder phosphor due to local inhomogeneity of the different dodecahedral positions and presence of the energy transfer between high-energy and low energy Ce3+ emission centers in this garnet. The effective Ce3+ to Mn2+ energy transfer process is observed in CYMSSG:Ce, Mn phosphors resulting in the redshift of the emission spectra in comparison with CYMSSG:Ce counterpart. We have shown that CYMSSG:Ce and CYMSSG:Ce, Mn powder phosphors can be used as an efficient photoconverter (PC) for creation of the high-power white LEDs (WLEDs). The prototypes of PC-WLEDs, based on 450 nm emitting blue LED and planar layers of CYMSSG:Ce and CYMSSG:Ce, Mn microcrystalline powder phosphors, embedded in the epoxy resin, were prepared and their photoconversion properties were investigated as well.

Influence of Ceria Addition on Crystallization Behavior and Properties of Mesoporous Bioactive Glasses in the SiO2-CaO-P2O5-CeO2 System.

Knowledge of the crystallization stability of bioactive glasses (BGs) is a key factor in developing porous scaffolds for hard tissue engineering. Thus, the crystallization behavior of three mesoporous bioactive glasses (MBGs) in the 70SiO2-(26-x)CaO-4P2O5-xCeO2 system (x stands for 0, 1 and 5 mol. %, namely MBG(0/1/5)Ce), prepared using the sol–gel method coupled with the evaporation-induced self-assembly method (EISA), was studied. A thermal analysis of the multiple-component crystallization exotherms from the DSC scans was performed using the Kissinger method. The main crystalline phases of Ca5(PO4)2.823(CO3)0.22O, CaSiO3 and CeO2 were confirmed to be generated by the devitrification of the MBG with 5% CeO2, MBG5Ce. Increasing the ceria content triggered a reduction in the first crystallization temperature while ceria segregation took place. The amount of segregated ceria of the annealed MBG5Ce decreased as the annealing temperature increased. The optimum processing temperature range to avoid the crystallization of the MBG(0/1/5)Ce powders was established.

Optical and structural properties of composites films based on Ce3+ -doped yttrium aluminium garnet nanoparticles embedded in polystyrene.

In the present work, attempts have been made to prepare scintillating nanoparticle composite films of Ce3+ -doped Y3 Al5 O12 (YAG:Ce) embedded in a polystyrene (PS) polymer. A YAG:Ce phosphor has been previously synthesized using the sol-gel method. YAG:Ce-PS composite films of 250 ± 30 μm thickness were prepared using a solvent casting procedure with different PS/solvent concentration and a different mass ratio between nanoparticles of YAG:Ce and PS. X-ray diffraction analysis confirmed that the YAG:Ce powders were successfully prepared. Using thermogravimetric analyses and differential scanning calorimetry, we found that the glass transition temperature (Tg) and thermal degradation were shifted to higher temperatures for composite films relative to pure PS. Photoluminescence showed the yellow emission of the Ce3+ -doped YAG phosphors, which was attributed to the 5d→4f transition of Ce3+ ion and the intensity of the emissions changed with the mass ratio of the YAG:Ce nanoparticles incorporated in the polymer and with the concentration of the polymer solution.

Anchoring of red perovskite nanocrystals on YAG:Ce phosphor for high color rendering index WLEDs

Widespread application of YAG:Ce-based white light-emitting diodes (WLEDs) is being challenged for their poor color rendering index (CRI) and high correlated color temperature (CCT) due to the lack of red emission. Organic-inorganic hybrid perovskite nanocrystals (MAPbX3 PNCs, X = Cl, Br, I or mixture of them), presenting high photoluminescence quantum yield, tunable emission color and simple fabrication process have been recognized as promising red-emitting component for warm WLEDs. However, additional protection process for PNCs always needed due to their poor stability, which complicates the fabrication procedures of WLEDs. Besides, nano-sized PNCs and micron YAG:Ce powder display different sinking behavior in silicone, which also hard to ensure the uniform distribution of the two components and subsequently stable optical characteristics of the device. Herein, a one-pot anchoring strategy is implemented to realize the enhanced thermal and photo-stabilities of in-situ generated red-emitting MAPbBr0.5I2.5 PNCs and simultaneously strong interaction between the PNCs and YAG:Ce to form PNCs@A-YAG composite, which greatly simplifies the processes, and also avoids the uneven distribution of phosphor and PNCs in silicone. Furthermore, the WLED, fabricated by PNCs@A-YAG and a commercial blue chip, exhibits high CRI of 92, low CCT of 4755 K, and super high saturated red color R9 of 95, which are of vital importance in achieving warm white light for indoor lighting applications. This work could promote the practical application of perovskite nanocrystals in the field of high color rendering index WLEDs.

Utilization of YAP:Ce powder scintillator for 57Fe Mössbauer spectroscopy

Using a powder scintillator for a detection of gamma and X-rays allows to create detectors of various shapes, moreover the handling and fabrication of such scintillators is much easier than in the case of large or thin monocrystals. We report on the application of YAlO3:Ce powder to Mössbauer spectroscopy. The detection efficiency and the energy resolution of the scintillators made of powders of two different granularities (grain size ≤30μm and 50–70μm) were investigated. The powder scintillators exhibited a comparable energy resolution and detection efficiency as YAlO3:Ce monocrystal with thickness of 400μm. Burying the YAlO3:Ce grains into the epoxy resin increased the energy resolution of powder scintillators. The studied scintillators were found to be suitable for experiments in Mössbauer spectroscopy. The performance of YAP is also compared to the NaI:Tl scintillator.

Characteristics of Porous YAG:Ce Nano-Powders Phosphor Fabricated by a Solution Combustion Synthesis.

A cerium-doped YAG (Y₃Al5O12) phosphor is used as a rare-earth element phosphor for blue light absorption and yellow light emission for a white light source. A solution combustion synthesis, which is a method for producing nano-powder, is a reaction that is spontaneous ignition by reaction heat released through oxidation/reduction reaction between metal nitrate and fuel. Since the reaction speed is fast and it does not go through a separate firing process, it is a method of easily synthesizing nano-powder by simple process. In this study, YAG:Ce nano-powders were prepared by using various fuels in the combustion synthesis method. Depending on the kind of the additive fuel, the reaction of the combustion synthesis process was different, and the shape of the powder particles according to the fuels was also different. The agglomerated particles of nanoparticles were observed and the characteristics of YAG:Ce powders synthesized under various conditions were analyzed.

Magnetic properties and microwave absorption of Ni0.7Zn0.3A0.05Fe1.95O4 (A = La, Ce, and Nd) powders within the range of 2–18 GHz

Ni0.7Zn0.3A0.05Fe1.95O4 (A = La, Ce, and Nd) powders were obtained by the sol-gel combustion technique. The phase composition, microstructure, and electromagnetic properties of La3+, Ce3+, and Nd3+ substituted Ni0.7Zn0.3Fe2O4 were investigated. Compared with the Ni0.7Zn0.3Fe2O4 ferrite, the saturation magnetization of substituted Ni0.7Zn0.3Fe2O4 powders decreases due to the reduction of the super-exchange interaction by the substitution of La3+, Ce3+, and Nd3+at the Fe site. Furthermore, the enhanced dielectric constant of the substituted Ni0.7Zn0.3Fe2O4 ferrites prompts to the formation of good impedance matching and thereby improving the microwave absorption performance. The best reflection loss of Ni0.7Zn0.3Ce0.05Fe1.95O4 ferrite is −17.5 dB at 13.8 GHz, and the corresponding absorption bandwidth (RL ≤ 5 dB) can be achieved 10.9 GHz. These results suggested that the Ni0.7Zn0.3Ce0.05Fe1.95O4 ferrite is a potential composite for electromagnetic applications, particularly for broadband microwave absorption.

CO2 laser post-treatment of sol-gel-derived Y3Al5O12:Ce phosphor ceramic powders

Cerium-doped yttrium aluminum garnet (Y3Al5O12:Ce, YAG:Ce) was prepared using a sol-gel method and then fired for CO2 laser post-treatments. Phase transformations and formation of impurities were not observed in YAG:Ce after CO2 laser sintering. The shift of the diffraction peak and the appearance of another Raman peak indicate a more homogeneous distribution of Ce activators and enhanced crystallinity in laser-sintered YAG hosts. Larger spheres (100–200 μm) with tiny crystallites (<10 μm) were observed on the smoother surface in the laser-sintered YAG:Ce, unlike the irregular, porous, and layered powders in the sol-gel-derived YAG:Ce (1–100 μm). Photoluminescence (PL) measurements revealed an emission increase of 180% and a red shift of the emission peak for the laser-sintered YAG:Ce powders compared with the sol-gel-derived powders. Both have comparable thermal PL quenching behavior; however, the YAG:Ce powders with CO2 laser treatment exhibited a PL efficiency improvement of approximately 4%.

The formation mechanism of cerium-bearing aerosols with the aid of chemical explosions in airtight scenarios

The formations of Ce-bearing aerosols from different materials, including CeO2, Ce powder and Ce tablet, via chemical explosive reactions.

Preparation of Ce-doped yttrium aluminum garnet phosphor particles using spray drying method

ABSTRACT The potential phosphor particles of Ce-doped yttrium aluminum garnet (YAG: Ce) particles were prepared using the spray drying method. This method yields a homogenous composition, regularly shaped particles, and has a short processing time. Meanwhile, acid catalysts affect the yield and particle shape of the spray dried particles. Therefore, in this study, three common acids i.e. formic acid, oxalic acid, and citric acid, were used to prepare the YAG: Ce powders. The X-ray diffraction measurements showed that all acid catalysts formed a single YAG phase. The SEM surface images and FIB cross-sectional images revealed two typical smooth hollow spherical and concaved solid spherical geometries. The statistical analysis showed that the particle size followed the order of citric acid-treated powder > oxalic acid-treated powder > formic acid-treated powder. Meanwhile, the citric acid-treated phosphor had a higher photoluminescence (PL) intensity than the formic acid- and oxalic acid-treated phosphors. The PL intensities of these three phosphors were correlated with their crystallite sizes, which is affected by the heat of combustion of the acid catalysts. Furthermore, the influence of the precursor properties on the corresponding formation mechanisms of the YAG: Ce powders was discussed.

Effect of reduced graphene oxides decorated by Ag and Ce on mechanical properties and electrical conductivity of copper matrix composites

This work investigated the influence of reduced graphene oxide (rGO) modified with silver (Ag) and cerium (Ce) on mechanical and electrical properties of copper matrix composites. Powders of Ce doped rGO and Ag doped rGO were synthesized using a hydrothermal reduction and an electroless plating (glucose chemical reduction) method, respectively. Then, composites with rGO content of 0.25 wt% were synthesized using ball milling and spark plasma sintering (SPS). The dispersion of the modified rGO and its bonding with the copper matrix have been signficantly improved. Hardness values of Ce-rGO/Cu and Ag-rGO/Cu composites were 26.3% and 16.4% higher than those of the sintered copper, and 19.4% and 10% higher than that of unmodified rGO/Cu composite. Meanwhile, the Ce-rGO/Cu and Ag-rGO/Cu composites maintained good conductivity and high ductility (with elongations of 26.3% and 25.2%, respectively). Compared with the sintered copper, the tensile strengths of these two types of copper matrix composites were 7.5% and 12% lower, respectively. The increase in hardness by using the modified rGOs is mainly due to the grain refinement of the matrix, and the lower value of the tensile strength is due to the defects of the modified rGOs and their poor bonding with the copper matrix.