Single Ce Research Articles

Thermal and spectroscopic studies of solid oxamate of light trivalent lanthanides

Solid-state LnL3·1.25H2O compounds, where L is oxamate and Ln is light trivalent lanthanides, have been synthesized. Simultaneous thermogravimetry and differential scanning calorimetry (TG–DSC), experimental and theoretical infrared spectroscopy, TG–DSC coupled to FTIR, elemental analysis, complexometry, and X-ray powder diffractometry were used to characterize and to study the thermal behavior of these compounds. The results led to information about the composition, dehydration, thermal stability, thermal decomposition, and gaseous products evolved during the thermal decomposition of these compounds in dynamic air atmosphere. The dehydration occurs in a single step and through a slow process. The thermal decomposition of the anhydrous compounds occur in a single (Ce), two (Pr), and three (La, Nd to Gd) steps with the formation of the respective oxides, CeO2, Pr6O11, and Ln2O3 (Ln = La, Nd to Gd). The theoretical and experimental spectroscopic study suggests that the carboxylate group and amide carbonyl group of oxamate are coordinate to the metals in a bidentate chelating mode.

Single crystal Ce doped scintillator material with garnet structure sensitive to gamma ray and neutron radiation

A mixed garnet scintillator host material is obtained from the melt—Yttrium Gadolinium Gallium Aluminum Garnet (YGGAG). In addition to the high thermal and chemical stability and radiation hardness found in garnet crystals, it offers sensitivity to neutrons due to the presence of Gd atoms, has lower melting temperature than yttrium aluminum garnet, and similar crystallization behavior suitable for growth of large volume crystals. Crystals of YGGAG doped with Ce of 10×10×10mm3 have already demonstrated energy resolution of 10% at 662keV.

Synthesis and investigations on CO catalytic oxidation activity of nanostructured Ce0.5Zr0.5O2 prepared by combustion method using polyvinyl alcohol

Nanostructured Ce 0.5 Zr 0.5 O 2 samples were synthesized by the combustion of the gel obtained from a mixture of polyvinyl alcohol (PVA) and metal nitrates at a temperature as low as 600 °C. The prepared samples were investigated by x-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). Their specific surface areas were determined from N 2 adsorption measurement at 77 K by Brunauer–Emmet–Teller (BET) method and their CO catalytic oxidation activities were investigated using a Landcom II instrument. The XRD and FE-SEM results revealed that Ce 0.5 Zr 0.5 O 2 nanocrystallines began to grow isotropically at 600 °C with the nanostructure found in all prepared samples. Further thermal treatment at 600 °C for 2 h yields the single crystalline phase Ce 0.5 Zr 0.5 O 2 nanostructured samples with average crystalline size < 50 nm and specific surface area of about 73 m 2 g −1. Besides, the effects of a number of factors such as calcination temperature and Ce/Zr molar ratio on the formation of prepared samples as well as the oxidative conversion of carbon monoxide over nanostructured Ce 0.5 Zr 0.5 O 2 catalyst were also studied.

Surface, structural and morphological characterization of nanocrystalline ceria–zirconia mixed oxides upon thermal aging

The effect of thermal aging on the physico-chemical properties of Ce–Zr oxides, as a function of Ce/Zr molar ratio, has been studied from the point of view of their application as catalytic nanomaterial. Homogeneous in size dimension and morphology, nanosized, single phase Ce–Zr solid solutions with various compositions were synthesized by the sol–gel like method. Upon thermal aging, important modifications of the textural and structural properties, which apparently create a strong effect on their catalytic performance, were observed. Their specific activity was found to be dependent on Ce/Zr molar ratio with the maximum observed over Ce0.75Zr0.25O2. Higher surface area, smaller particles, lower amount of particles agglomerates as well as higher amount of crystal faces, edges, and corners generate better catalytic activity, especially as long as cubic symmetry of mixed oxides was maintained.

Highly (100)-oriented Ce 1 − xFe xO 2 − δ solid solution films prepared by laser chemical vapor deposition

Ce 1 − x Fe x O 2 − δ solid solution films were prepared on amorphous silica substrates by laser chemical vapor deposition using metal dipivaloylmethanate precursors and a semiconductor InGaAlAs (808 nm in wavelength) laser. X-ray diffraction revealed the formation of single Ce 1 − x Fe x O 2 − δ phase at x ≤ 0.15, while CeO 2 and Fe 2O 3 phases were found for higher Fe content. Highly (100)-oriented Ce 1 − x Fe x O 2 − δ ( x = 0.02) films were obtained at laser power, P L = 50–200 W and deposition temperature, T dep = 800–1063 K. Lotgering factor (200) was calculated to be above 0.8 for films prepared at P L = 50–150 W. X-ray photoelectron spectroscopy revealed the presence of Fe 3+, Ce 4+ and Ce 3+ on solid solution films. Cross-sectional transmission electron microscope images disclosed a film columnar feather-like structure with a large number of nano-scale interspaces. Deposition rates were 2 or 3 orders of magnitude higher than those reported for conventional metal organic chemical vapor deposition of CeO 2.

Synthesis, growth mechanism and photoluminescence of monodispersed cubic shape Ce doped YAG nanophosphor

In the present work, a novel method for the synthesis of monodispersed cubic shape Ce-doped yttrium aluminum garnet (YAG:Ce) nanophosphors is reported. Single phase Ce doped YAG nanoparticles are prepared by solvothermal processing, followed by annealing treatment. Morphological investigation by scanning electron microscopy (SEM) showed the formation of monodispersed 500 nm cubic shape Ce-doped YAG phosphor. The crystalline Ce-doped YAG showed broad emission peaks in the range of 480–640 nm with maximum intensity at 524 nm. The emission intensity increased with increase in calcination temperatures while reduced with increase in Ce 3+ ions concentration. Detailed study was carried out to understand the formation of monodispersed cubic shape Ce doped YAG nanoparticles. It was found that the solvent, surfactant and impurity (counter ions of cerium and aluminum salt) has significant effect on the crystal growth.

Comparative study of transparent ceramic and single crystal Ce doped LuAG scintillators

Abstract Transparent ceramic Ce 0.5% doped Lu 3 Al 5 O 12 (LuAG) scintillator grown by the sintering method and single crystalline Ce doped LuAG grown by the Czochralski method are prepared. They are cut to the physical dimensions 4 × 4 × 2 mm 3 . Their transmittance and radio luminescence spectra are evaluated. They are both transmissive in wavelength longer than 500 nm and intense Ce 3+ 5d–4f emission appears around 520 nm. When 137 Cs γ-ray is irradiated, 662 keV photo-absorption peaks are clearly observed in each sample. The transparent ceramic one shows higher light yield than that of the single crystalline one. The absolute light yield of the ceramic sample is turned out to be 14800 ± 1500 ph/MeV. The decay time constants are evaluated under pulse X-ray excitation. The main component of the decay time of ceramic and single crystalline one are determined as 37 and 46 ns, respectively.

An investigation into the electrochemical recovery of rare earth ions in a CsCl-based molten salt

A CsCl-based melt, was used as a supporting electrolyte for a fuel cycle in pyrochemical separation, as it has a high solubility for lanthanide oxide. Cyclic voltammetry and square wave voltammetry were carried out to investigate the cathodic reduction of those rare earth ions. The results prove that the cathodic process of La(III) ions dissolved in a CsCl-based melt, with a one-step reduction La 3+ + 3e − = La, and is similar to those of other reports which have utilised LiCl–KCl or CaCl 2–KCl molten salt systems. However, for the Ce(III) ions that dissolved in a CsCl-based melt, there is a significant difference when compared with published literature as there are two reduction steps instead of the reported single step Ce 3+ + e − = Ce 2+ and Ce 2+ + 2e − = Ce. In order to explain the novel result, a detailed investigation was focused on the cathodic process of Ce(III) in a CsCl-based melt. The identification of the M–O (M = La, Ce) compounds that are stable in the electrolyte, as well as the determination of their solubility products, were carried out by potentiometric titration using an oxide ion sensor. Furthermore, the E-pO 2− (potential-oxide ion) diagram for the M–O stable compound was constructed by combining both theoretical and experimental data.

Effect of In, Ce and Bi dopings on sintering and dielectric properties of Ba(Zn 1/3Nb 2/3)O 3 ceramics

In, Ce and Bi doped Ba(Zn 1/3Nb 2/3)O 3 (BZN) ceramics were prepared by conventional mixed oxide technique. In doping between 0.2 and 4.0 mol% increased the density of BZN at 1300 °C, Ce doping caused a decrease in density at 1250 °C. Levels of Bi 2O 3 up to 1.0 mol% had negative effect on densification, while high level doping could significantly improve the densification of the specimens. XRD of the samples indicated that In, Ce and Bi doping resulted in single phase formation at all concentrations, except 0.5 mol% Bi. SEM of Bi doped BZN indicated only single phase structure and Ce doping even at 0.2 mol% gave some secondary phases. In and Ce doping increased the dielectric constant from 41 to around 66 at 1 MHz. Bi doping decreased the dielectric constant to about 37 at 0.2 mol%, and then higher doping led to dielectric constant to increase to about 63.

Development of modified micro-pulling-down method for bromide and chloride single crystals

We developed a modified micro-pulling-down (μ-PD) method for the crystal growth of halide materials with highly hygroscopic nature. A removable chamber system of the modified μ-PD method that can enter a globe box filled with Ar gas enabled to handle starting materials, set up a crucible and hot zone, grow a single crystal from the melt and take out a grown crystal without exposing to outside atmosphere. By the modified μ-PD method, CeCl3 and Ce 1% doped LaBr3 single crystals, which were famous as scintillator with high light yield and energy resolution were grown. Grown CeCl3 and Ce:LaBr3 single crystals indicated high transparency and they have no visible cracks and inclusions. In photoluminescence measurements, emission peak around 365nm was observed for CeCl3 single crystal and Ce:LaBr3 single crystal indicated two emission peaks around 360 and 380nm, which originated from 5d–4f transition of Ce3+ ion.

Single cerium zirconate buffer layer on biaxially textured metal substrates for high performance coated conductors

Textured cerium zirconate (Ce x Zr1−x O2) films were deposited on biaxially textured Ni-5at.%W substrate by direct-current (dc) reactive magnetron sputtering for low cost production of high performance YBa2Cu3O7−δ (YBCO) coated conductors. Film composition was controlled by modulating dc power applied to the Ce metal target. X-ray diffraction analysis shows that all the samples exhibit epitaxial growth, with c-axis perpendicular to the substrate surface. The YBCO film deposited directly on the Ce0.32Zr0.68O2 layer for optimized lattice matching shows a transition temperature T c and critical current density J c (75.5 K, self field) of 90.4 K and 1.3 MA/cm2. The in-field dependence of J c is similar to the standard CeO2/YSZ/CeO2 buffered samples. These results demonstrate that a single Ce x Zr1−x O2 buffer layer, instead of CeO2/YSZ/CeO2 multi-buffer layers for the fabrication of YBCO coated conductors, provides advantages such as simplified architecture and potentially reduced cost due to the reduced fabrication steps.

Low Temperature Magnetic Properties of Ce3Pd20Si6

Magnetization of a single crystalline Ce 3 Pd 20 Si 6 was measured at low temperatures down to 90 mK in fields up to 11 T for the three principal directions [100], [110], and [111]. For all directions, two transitions were observed in the temperature variation of the magnetization M ( T ) at 0.2 T; a broad peak at 0.28 K associated with a phase-III transition, and an upward bending at ∼0.5 K due to a phase-II ordering from the paramagnetic state (phase-I). The latter critical temperature T I–II is found to be strongly enhanced in magnetic fields B , depending on the field direction, and T I–II ( B ) becomes highly anisotropic. These results suggest that phase-II is an antiferroquadrupole state originated from a Γ 8 ground state. By contrast, no appreciable anisotropy is found in the phase-III state. At 90 mK, phase-III collapses by applying a field of ∼0.63 T for all directions. Above this field, the magnetization curve M ( B ) becomes strongly anisotropic. The magnetization value per Ce in the phase-I re...

Formation of Ce 3+ at the cerium dioxide (1 1 0) surface by doping

The formation of Ce 3+ ions in CeO 2 is key for its applications. We present density functional theory (DFT) studies of doping of the CeO 2 (1 1 0) surface with +5 cations, Ta and Nb, as a route to formation of Ce 3+. We use DFT corrected for on-site Coulomb interactions (DFT + U, U = 5 eV) and hybrid DFT (HSE06 functional). With both methods we find formation of Ce 3+ ions due to the extra electron from the dopant residing on a single Ce site, confirming the DFT + U description of these systems. Doping with Nb and Ta activates the surface to NO 2 reduction – there is no interaction with the undoped surface but the Ce 3+ ion in the doped surface interacts strongly with NO 2.

Binuclear Nickel Carbonyl Thiocarbonyls: Metal−Metal Multiple Bonds versus Four-Electron Donor Thiocarbonyl Groups

The structures of the mononuclear derivatives Ni(CS)(CO)(n) (n = 3, 2, 1, 0) and the binuclear derivatives Ni(2)(CS)(2)(CO)(n) (n = 5, 4, 3, 2) have been optimized by density functional theory for comparison with the corresponding structures of Ni(CO)(n+1) and Ni(2)(CO)(n+2), respectively. In the lowest energy structures for Ni(CS)(CO)(n) (n = 3, 2, 1), the nickel atom has approximate tetrahedral (n = 3), trigonal planar (n = 2), or bent coordination (n = 1) corresponding to 18-, 16-, and 14-electron metal configurations, respectively. The six lowest energy Ni(2)(CS)(2)(CO)(5) structures all have a single CE (E = S, O) bridge and a formal Ni-Ni single bond of length approximately 2.6 to approximately 2.7 A analogous to the lowest energy Ni(2)(CO)(7) structure. The Ni(2)(CS)(2)(CO)(5) structures with a bridging CS group are of lower energies than similar structures with a bridging CO group. Higher energy Ni(2)(CS)(2)(CO)(5) structures with a linear bridging CE group (E = O, S) and no Ni...Ni bond are also found with tetrahedral coordination for both nickel atoms. The lowest energy Ni(2)(CS)(2)(CO)(4) structures are doubly bridged structures with only two-electron donor CO and CS groups and Ni=Ni distances of approximately 2.5 A suggesting the formal double bond needed to give both nickel atoms the favored 18-electron configuration. For Ni(2)(CS)(2)(CO)(3) the structures with one four-electron donor bridging eta(2)-mu-CS group and a formal Ni=Ni double bond of approximately 2.4 to approximately 2.5 A are energetically preferred over triply bridged structures with a shorter Ni[triple bond]Ni distance of approximately 2.2 A, corresponding to a formal triple bond and similar to the lowest energy Ni(2)(CO)(5) structure. The lowest energy Ni(2)(CS)(2)(CO)(2) structures are generally derived from Ni(2)(CS)(2)(CO)(3) structures by removal of a carbonyl group. No formal quadruple bonds are found in any of the Ni(2)(CS)(2)(CO)(2) structures, as indicated by the absence of ultrashort Ni(-4)Ni distances.

Template-free hydrothermal synthesis and characterisation of single crystalline Ce(OH)CO3 and CeO2 with spindle-like structures

Single crystalline Ce(OH)CO3 and CeO2 with spindle-like structures were synthesised by a facile hydrothermal synthesis method. Then the effect of reaction time and concentration of cerium precursor on the formation and morphologies of Ce(OH)CO3 and CeO2 were further investigated. The products were characterised by X-ray powder diffraction, transmission electron microscopy and scanning electron microscopy. The results show that the single crystalline Ce(OH)CO3 with spindle-like structures could be obtained at 120°C for 8 h. The present method shows an easy process without high reaction temperature, long reaction time, surfactant and template to attain final Ce(OH)CO3 products. Furthermore, single crystalline CeO2 with spindle-like structures had been fabricated by a oxidation process at 600°C for 2 h using Ce(OH)CO3, with spindle-like structures as the precursor. Meanwhile, the single crystalline spindle-like CeO2 shows a high catalytic activity on CO conversion.

Analysis of N‐acetylaminosugars by CE: A comparative derivatization study

N-linked or O-linked glycans derived from glycoprotein processing carry, an N-acetylglucosamine or an N-acetylgalactosamine respectively, at their reducing termini. The presence of the N-acetylamino group on C-2 of reducing sugar residues has been reported to hamper the derivatization reaction with a chromophore at the anomeric centre. In this paper N-acetyllactosamine, N-acetylglucosamine, N-acetylgalactosamine and several other neutral monosaccharides are coupled to three different dyes (4-aminobenzonitrile, 2-aminopyridine, 2-aminobenzoic acid (2-AA)) by reductive amination and analysed by CE with UV detection. The 2-AA derivatives showed the lowest concentration detection limits, varying approximately in the 2-3 muM range for the saccharides tested including the N-acetamido ones. The possibility to separate and detect with the same sensitivity ten 2-AA-labelled monosaccharides mainly found in mammalian or plant glycoproteins in a single CE run is highlighted. The analysis has been carried out in less than 25 min using the borate-complexation method in CZE mode. The influence of the strength of the acid used as catalyst in the chemical modification of the sugars with 2-AA is also shortly addressed.

Identification and Quality Control of Chinese Medicine Based on the Fingerprint Techniques

Traditional Chinese medicine (TCM) contains a large number of herbal medicine and Chinese patent medicine, each of which contains many compounds that may be relevant to the medicine's putative activity. The homonym and synonym are very popular in TCM for its source complex. How to identify species and control the quality of TCM has become urgent, and fingerprint techniques have now been widely used in TCM for these purposes. In the present paper, four popular fingerprinting techniques (CE, HPLC, GC, and XRD) and their current applications in TCM are reviewed. All these techniques are proved to be an advanced and effective way to get an accurate and integral fingerprint, and each is discussed in detail with examples. CE, HPLC and GC are widely considered as the ideal methods to work out fingerprint analysis. GC is outstanding in analyzing the volatile components and HPLC has advantages in the analysis of the majority of chemical components of TCM. However, because of the complexity of chemical components in TCM, it is very hard for single CE, HPLC or GC to characterize all these components. Hyphenated techniques are strongly recommended for the purpose of quality control of TCM. It is concluded that more rational approach to the authentication and quality assessment of TCM is essential and the fingerprint techniques might be a powerful tool for quality control of TCM in the near future for their unique advantages.

A simple MOD method to grow a single buffer layer of Ce 0.8Gd 0.2O 1.9 (CGO) for coated conductors

A single Ce 0.8Gd 0.2O 1.9 (CGO) buffer layer was successfully grown on the home-made textured Ni–5 at.%W (Ni–5W) substrates for YBCO coated conductors by a simple metal–organic deposition (MOD) technique. The precursor solution was prepared using a newly developed process and only contained common metal–organic salts of both Ce and Gd dissolved into a propionic acid solvent. The precursor solution at 0.4 M concentration was spin coated on short samples of Ni–5W substrates and heat-treated at 1100 °C in a mixture gas of 5% H 2 in Ar for an hour. X-ray studies indicated that the CGO films had good out-of-plane and in-plane textures with full-width-half-maximum values of 4.18° and 6.19°, respectively. Atomic force microscope (AFM) investigations of the CGO films revealed that most of the grain boundary grooves on the Ni–5W surface were found to be well covered by CGO layers, which had a fairly dense and smooth microstructure without cracks and porosity. These results indicate that our MOD technique is very promising for further development of single buffer layer architecture for YBCO coated conductors, due to its low cost and simple process.

Scintillation Characteristics of ${\rm Ce}:{\rm Gd}_{2}{\rm Si}_{2}{\rm O}_{7}$ (Ce 2.5–30 mol%) Single Crystals Prepared by the Floating Zone Method

Cerium-doped gadolinium pyrosilicate single crystals Ce:Gd <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> Si <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">7</sub> (Ce:GPS) with various Ce concentrations of 2.5-30 mol% with respect to the total rare-earth sites were prepared by the floating zone method. Their scintillation performances were investigated under irradiation of gamma rays of <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">137</sup> Cs. The Ce concentration dependence of scintillation characteristics and high-performance scintillation characteristics were obtained: 3-6 times greater light output than that of BGO single crystals, rapid decay, and good energy resolutions of 5.1-8.4%. Furthermore, X-ray diffraction patterns of Ce:GPS revealed Ce concentration dependence of the crystal structure of Ce:GPS.

Statistical model structure of A1−xZxB2 Laves phase C15 system—the superconducting alloy Ce1−xLaxRu2

The local structure of the Ce1−xLaxRu2 system measured by EXAFS is re-examined and correlated to the statistical ad hoc model recently applied to the sphalerite, wurtzite, and other intermetallic ternary alloys. Deconvolution of the EXAFS data shows that the Ce1−xLaxRu2 ternary system is essentially a mixture of CeRu2 and LaRu2 binary alloys with a small proportion of the Ce0.5La0.5Ru2 ternary configuration, which is maximum for the intermediate concentration. Moreover, the analysis reveals that while the LaRu2 configuration exhibits a Bernoulli random distribution, the presence of a Ce atom affects both the CeRu2 and Ce0.5La0.5Ru2 distributions, strongly favoring the configuration with the CeCe pair, while keeping rare that with a single Ce ion.