Reaction between rare earth elements and HFNO2 solution

Rare earth elements react with HFNO₂ solution to produce nitrosylium fluorometallates (NO)_xLnF_x+3. The value of x is 1.0 or 1.5 for light rare earth elements and 0.5 or 1.0 for heavy rare earths. Nitrosylium fluorometallates of rare earth elements can be decomposed into the simple fluoride and nitrosyl fluoride at low temperatures (46–68°C).     

Synthesis of 10 nm β‐NaYF4:Yb,Er/NaYF4 Core/Shell Upconversion Nanocrystals with 5 nm Particle Cores

A new method is presented for preparing gram amounts of very small core/shell upconversion nanocrystals without additional codoping of the particles. First, ca. 5 nm β‐NaYF₄:Yb,Er core particles are formed by the reaction of sodium oleate, rare‐earth oleate, and ammonium fluoride, thereby making use of the fact that a high ratio of sodium to rare‐earth ions promotes the nucleation of a large number of β‐phase seeds. Thereafter, a 2 nm thick NaYF₄ shell is formed by using 3–4 nm particles of α‐NaYF₄ as a single‐source precursor for the β‐phase shell material. In contrast to the core particles, however, these α‐phase particles are prepared with a low ratio of sodium to rare‐earth ions, which efficiently suppresses an undesired nucleation of β‐NaYF₄ particles during shell growth.     

Ionic conductivity of multicomponent fluorite-structured fluorides

Influence of mixing of homovalent cations on the fast anionic conductivity, static permittivity, and thermal diffusivity is investigated in multicomponent fluorite-structured concentrated solid solutions of alkali earth and rare earth fluorides. Influence of mixing of alkali earth cations on electrical properties of fluoride superionics is studied in Ba_{0.7 − x} Sr _x La_0.3F_2.3 single crystals and Ca_{0.85 − x} Sr _x Nd_0.15F_2.15 transparent polycrystals. Influence of mixing of rare earth cations on electrical properties of fluoride superionics is studied in Ba_0.75La_{0.25 − x} Nd _x F_2.25 and Ba_0.35Sr_0.35(R ₁, ..., R _i )_0.3F_2.3 (i = 1–6; R _i stands for rare earth elements) single crystals. It is shown that the ionic conductivity decreases with increasing difference between mean ionic radii of rare earth and alkali earth cations. Up to 350°C, the fastest ionic conductivity is found in Ba_0.35Sr_0.35La_0.3F_2.3 single crystals.     

Neutron activation analysis of rare earth impurities in europium oxide

A neutron activation analysis method for determining Yb, Dy, Ho, Sm and La impurities in europium oxide with sensitivities of 10^?5 to 10^?7% is described. The method is based on a preliminary concentration of the rare earth elements by reducing europium(III) with zinc to europium(II), and separating the trivalent rare earth elements by extraction chromatography. After neutron irradiation, the individual radioisotopes of the rare earth elements are separated by using KU-2 cation exchange resin and ammonium α-hydroxyisobutyrate solution as the eluant.     

Neutron activation analysis of rare earth impurities in metallic uranium

A method with a sensitivity of 2·10⁻⁷ to 1·10⁻¹⁰% has been developed for determining Yb, Ho, Dy, Gd, Eu, Sm and La impurities in metallic uranium by means of neutron activation. The method is based on a preliminary chromatographic separation of the total amount of rare earth elements from uranium by passing the solution in sulphuric acid through KU-2 cation exchange resin and eluting the traces of uranium retained by the resin with a solution of ascorbic acid. The rare earth impurities are then eluted from the resin with 4–5N HCl, evaporated, and irradiated for 20 hours with a neutron flux of 1.2·10¹³ n·cm⁻²·sec⁻¹. Subsequently the traces of the rare earth elements are co-precipitated with Fe(OH)₃, dissolved in concentrated HCl and separated from the iron and other impurities by passing the solution through Dowex 1X8 anion exchange resin in the chloride form. The individual rare earth elements are then separated from each other using KU-2 cation exchange resin and a solution of ammonium α-hydroxyisobutyrate as the eluant.     

Determination of individual rare earth elements in Vietnamese monazite by radiochemical neutron activation analysis

Radiochemical neutron activation analysis (RNAA) has been applied for determination of rare earth elements (REE) in Vietnamese monazite. The chemical separation procedure used is based on the chromatographic elution of rare earth groups, after the separation of²³³Pa(Th) in irradiated monazite samples by coprecipitation with MnO₂, the rare earth elements were retained by Biorad AG1×8 resin column in 10% 15.4M HNO₃-90% methanol solution. The elution of heavy rare earth (HREE) and middle rare earth (MREE) groups was carried out with 10% 1M HNO₃-90% methanol and 10% 0.05M HNO₃-90% methanol solution, respectively; while the light rare earths (LREE) were eluted from the column by 0.1M HNO₃ solution. The accuracy of the method was checked by the analysis of granodiorite GSP-I and the rare earth values were in good agreement.     

Extraction of rare earth elements with 1-(diphenylphosphorylmethoxy)-2-diphenylphosphoryl-4-ethylbenzene with the use of 1,1,7-trihydrododecafluoroheptanol as a solvent

Extraction of rare earth elements from nitric acid solutions in a 1,1,7-trihydrododecafluoroheptanol-water system with the use of phosphoryl-containing podand 1-(diphenylphosphorylmethoxy)-2-diphenylphosphoryl-4-ethylbenzene (L) was studied. The content of metals in organic phase was shown to be negligible at nitric acid concentration lower 1 mol/L. Distribution ratio sharply increases with nitric acid concentration from 1 mol/L and reaches 5.5 for the yttrium subgroup elements at HNO₃ concentration of 6 mol/L. The rare earth elements of the yttrium subgroup were found to be extracted much better than the rare earth elements of the cerium subgroup under the same conditions, the distribution ratios in both subgroups smoothly rise with atomic number of element. It was shown using the shift of extraction equilibrium that the M: L ratio in extracted complexes is 1: 2 irrespective of the nature of rare earth element. The structure of complex {Yb[η²-(O,O′)-L]₂(η²-O₂NO)₂}(O₂NOHNO₃), whose single crystals were isolated from extraction solution, was established by X-ray diffraction study. The system can be used for the isolation and separation of rare earth elements.     

La、Ce、Yb掺杂对LiNi0.5Mn1.5O4高电压正极材料性能的影响

采用低温燃烧法制备出不同稀土元素掺杂的高电压镍锰酸锂(LiNi_(0.5)Mn_(1.5)O_4)正极材料,探究了不同掺杂比例(物质的量分数0.5%、1%、2%)和不同掺杂稀土元素(La、Ce、Yb)对样品性能的影响,并通过X射线衍射、拉曼光谱、电子顺磁共振和恒电流间歇滴定等技术探究了其影响机理。从X射线衍射图可以看出,稀土掺杂可以抑制Li_xNi_(1-x)O杂质相的产生;电感耦合等离子谱结果表明,掺杂进入的稀土元素与设计比例基本相符;从拉曼光谱图可以看出,稀土元素可以使样品的有序相增多,其中Ce掺杂样品的有序相最多;结合电子顺磁共振波谱氧空位测试,发现Ce掺杂诱导了样品中有序相比例增加,从而使样品的稳定性提高;经恒电流间歇滴定技术测试发现,Ce掺杂镍锰酸锂样品的扩散系数比未掺杂样品高了约15倍;在不同掺杂比例上,1%掺杂量时样品性能最佳。在3种最佳掺杂量的稀土元素样品中,Ce掺杂的样品性能最优,首次放电比容量可以达到133.3mAh·g~(-1),比未掺杂样品放电比容量高且首次效率提高了 18%,在1C下循环200次后,容量保持率为102%,比未掺杂样品提高了 8%。     

Determination of traces of rare earth elements in high-purity uranium by ion-exchange separation and neutron activation γ-spectrometry

Neutron activation γ-spectrometry is sufficiently sensitive for the determination of traces of rare earth elements but quantitative separation from uranium is essential. The rare earth elements in 0.2 M ammonium carbonate medium are quantitatively retained on Chelex-100, and are quantitatively separated from uranium by recycling the eluate. When 10-g samples are used, neutron activation provides detection limits of 1–20 μg kg^?1. Recoveries of rare earths, checked by spiking with radiotracers, are essentially complete.     

Preparation of samples for the α—Spectrometry of transplutonium elements

The electrolytic deposition of the hydroxides of rare earth and transplutonium elements on nickel holders from α-hydroxyisobutyrate solutions of 10⁻⁵ M to 5·10⁻¹ M concentrations has been investigated in the presence of ammonium chloride. It is shown that at total concentrations of ≥10⁻¹² M of rare earth and transplutonium elements, their electrodeposition proceeds with a 90% yield.     

Extraction of rare earth elements by high molecular weight amines from nitric acid solutions

Extraction of trivalent rare earth elements by a high molecular weight primary amine /decylamine/ from 0.5–3M nitric acid solutions, containing potassium phosphotungstate /K₁₀P₂W₁₇O₆₁/, has been investigated. The effect of nitric acid and potassium phosphotungstate concentration of the organic solvent, and lanthanides ionic radii upon distribution coefficients has been studied. It has been established that decylamine solutions in chloroform can be used for the group isolation of rare earth elements and for their separation.     

Rare earth impurities in high purity lanthanum oxide determined by neutron activation analysis

Individual rare earth impurities in high purity La₂O₃ (99.9%) have been determined by NAA after pre-separation of the matrix (La). The separation is carried out on an anion exchanger (Dowex 1×8) using different mixtures of methanol/nitric acid as eluants. The rare earth elements from Dy to Lu are eluted quantitatively using a 10% 1M HNO₃-90% methanol mixture, while the light rare earths from Ce to Gd are eluted quantitatively using a 10% 0.05M HNO₃-90% methanol mixture. La, which is retained on the column, is eluted using 0.1M HNO₃. The recoveries of the various rare earth elements have been checked using radiotracers and also by spiking the sample with known amount of elements, and the recoveries are found to be quantitative. Results obtained on a typical high purity lanthanum oxide are reported here.     

Rare earth element complexation by fluoride ions in aqueous solution

Rare earth fluoride stability constants for Ce, Eu, Gd, Tb and Yb at 25°C have been determined by examining the influence of fluoride ions on the distribution of rare earths between tributyl phosphate (TBP) and 0.68M NaClO₄. Our results indicate that rare earth mono and difluoro complexation constants show a steady increase as a function of atomic number from La to Tb but remain relatively constant after Dy. This behavior is similar to that which has been observed for dicarboxylic acids. Stepwise stability constant ratios, K₂/K₁, obtained in our work (where K₁=[MF²⁺][M³⁺]^–1[F^–]^–1 and K₂=[MF ₂ ⁺ ]^–1[MF²⁺]^–1[F^–]^–1) indicated that, for all rare earths, K₂/K₁=0.09±0.03.     

Bulky Amido Ligands in Rare Earth Chemistry — Syntheses,Structures, and Catalysis

The amido metal chemistry of the rare earth elements is a rapid developing area in coordination chemistry. Especially bulky mono and bidentate amido and amidinates have been introduced as ligands in rare earth chemistry. Due to these sterically demanding ligands, the coordination numbers of the rare earth elements are significantly reduced. This article focuses on two of these bulky ligand systems: bis(trimethylsilyl)amide and aminotroponiminates. The homoleptic bis(trimethylsilyl)amides of rare earth elements, [Ln{N(SiMe₃)₂}₃], are well established compounds in synthetic chemistry. Therefore, this article reviews recent progress in the catalytic application of these compounds. In the second part of this research report, it is shown that N, N′‐disubstituted aminotroponiminates and mono bridged bisaminotroponiminates can be used as cyclopentadienyl alternatives. Achiral and chiral aminotroponiminates have been used. The structural properties, reactivities as well as the catalytic and synthetic applications of the aminotroponiminates complexes will be outlined in this article.     

Electro‐kinetic Separation of Rare Earth Elements Using a Redox‐Active Ligand

Purification of rare earth elements is challenging due to their chemical similarities. All of the deployed separation methods rely on thermodynamic properties, such as distribution equilibria in solvent extraction. Rare‐earth‐metal separations based on kinetic differences have not been examined. Herein, we demonstrate a new approach for rare‐earth‐element separations by exploiting differences in the oxidation rates within a series of rare earth compounds containing the redox‐active ligand [{2‐(t BuN(O))C₆H₄CH₂}₃N]³⁻. Using this method, a single‐step separation factor up to 261 was obtained for the separation of a 50:50 yttrium–lutetium mixture.     

Determination of dysprosium,europium, samarium and gadolinium in yttrium oxide of high purity by means of neutron activation analysis

Radioactivation analysis is the only method which allows the determination of individual rare earth element impurities in rare earth elements of high purity. The determination of dysprosium, europium, samarium and gadolinium in yttrium oxide is complicated by the short half-life of¹⁶⁵Dy (138 min.) and by the difficulty of separating traces of these elements from the matrix. A chromatographic method has been developed, for the separation of traces of Dy, Eu, Sm and Gd from ytrium, on a column packed with anion exchangerAV-17, by means of elution with 0.1N and 0.3M solutions of EDTA-sodium salt, followed by the separation of the mixture of the rare earth impurities on a microcolumn of cation exchangerKU-2, using a 0.17M solution of ammonium α-hydroxyisobutyrate as the eluent. The sensitivity of the determination of Dy, in the case of irradiating 10 mg of Y₂O₃ with a flux of 1.2·10¹³ n·cm⁻²·sec⁻¹ for 5 min. was 1·10⁻⁷%; the corresponding values for Sm, Eu and Gd, when irradiating a 100 mg sample of Y₂O₃ for 20 hours with the same flux, were 2·10⁻⁷%, 1·10⁻⁸% and 5·10⁻⁶%, respectively.     

Reversed-phase thin-layer chromatography of the rare earth elements

Summary Partition chromatographic behaviour of the rare earth elements on C₁₈ bonded silica reversed-phase material has been investigated by thin-layer chromatography in methanol — lactate media. The rare earth lactato complexes are distributed and fractionated on bonded silica layers without ion-interaction reagents. The concentration and pH of lactate solution, methanol concentration and temperature have effects on the migration and resolution of the rare earth elements. The partition system is particularly suited to separate adjacent rare earths of middle atomic weight groups, allowing the separation of gadolinium, terbium, dysprosium, holmium, erbium and thulium to be achieved by development to 18 cm distance.     

An Efficient Catalyst System at Mild Reaction Conditions Containing Rare Earth Metal Complexes

An efficient rare earth metal complex‐catalyzed cycloaddition reaction of CO₂ with propylene oxide using Hdpza (di(2‐pyrazyl)amine) as a N‐donor ligand has been accomplished in good to excellent yields with high selectivity. The effects of different rare earth metal salts, ligands and reaction conditions were examined. Catalytic reaction tests demonstrated that the incorporation of ErCl₃ and Hdpza can significantly enhance the catalytic reactivity of the TBAB (nBu₄NBr, tetra‐n‐butyl ammonium bromide) towards cycloaddition reaction of CO₂ and propylene oxide that produce cyclic carbonates under mild conditions without any co‐solvent.     

Preparation of rare earth oxyfluorides and their properties as a material for fuel cell

The formation of rare earth oxyfluorides and their properties as an electrocatalyst and/or a solid electrolyte using for fuel cell were studied by means of x-ray and electrochemical methods.By a high temperature solid reaction between rare earth fluorides and rare earth or zirconium oxides not only the simple oxyfluoride such as NdOF, SmOF, CeOF and YOF but also the binary one written by Nd_1?xLn_xOF, (NdOF)_1?x(MO)_x and (ZrO₂)_1?x(LnF₃)_x were obtained, where Ln; Y, La, Nd, Sm and Yb, MO; alkaline earth oxide and Nb₂O₅. On the solid reaction process, it was found that the exchange reaction of anion, that is F? and O^2?, took place at first between the rare earth fluoride and the oxide. LnF₃ could form the solid solution with ZrO₂ at above 1200°C taking the fluorite structure in the composition range of below 30 mol%-LnF₃, so-called the stabilized zirconia.The crystal type of these oxyfluorides was any one of the rhombohedral, the cubic and the tetragonal. The cubic phase oxyfluorides contained Nd showed high electrocatalytic activity for both the hydrogen oxidation and the oxygen reduction. Then (NdOF.)_0.9(Nb₂O₅)_0.1 and (ZrO₂)_1?x(LnF₃)_x were found to act as the oxide ion conducting solid electrolyte.     

Preorganized, cone-conformational calix[4]arene possessing four propylenephosphonic acids with high extraction ability and separation efficiency for trivalent rare earth elements

p-t-Octylcalix[4]arene with tetraphosphonic acid at lower rim in cone conformation has been designed and synthesized as a new extraction reagent to investigate the extraction behavior of the nine trivalent rare earth elements: La, Pr, Nd, Sm, Eu, Gd, Ho, Y, and Er. The extraction of rare earth metals with the present extractant occurs by a simple ion-exchange mechanism. The stoichiometry of the extractant to rare earth metal ion was determined to be 2:1 based on the extraction equation, half pH values, pH_1/2, and the difference in the values of the extraction equilibrium constants of nine trivalent rare earth elements and separation factors between adjacent rare earth elements. This allowed for comparison of the estimated extraction efficiency and selectivity. The present extractant exhibited extremely high extractability and sufficiently high separation efficiency of rare earth metals, compared with calix[4]arene tetraphosphonic acid at upper rim, calix[4]arene tetraacetic acid at lower rim as previously reported and the commercial extraction reagent. This results was attributed to size and multidentate effects based on the preorganized cyclic structure of calix[4]arene and to the original selectivity of functional group for heavier rare earth elements.