Quantitative determination of F:O ratios in rare earth oxide fluorides by energy dispersive X-ray analysis

The F:O ratio in homogeneous and inhomogeneous rare earth oxide fluoride systems of compositions RO_1+xF_1–2x with –0.1x0.1 can be determined by energy dispersive X-ray (EDX) analysis with an accuracy of ±0.5% if an appropriate background modelling procedure is applied and if the EDX signals of the light elements are free of overlap from the accompanying rare earth element. The latter condition holds true for R=Tb–Lu and it is shown that the calibration of the method with well-defined samples of YbO_1+xF_1–2x can be transferred with only a moderate loss of accuracy to the determination of oxygen and fluorine in DyOF and ErOF. Increasing signal overlap in case of GdOF, EuOF, SmOF and especially PrOF necessitates the choice of different channels for background modelling, and the accuracy of the method is hence decreasing to ±4% for these systems.     

Formation of stabilized zirconia with rare earth fluorides

New reactions to prepare stabilized zirconia using rare earth fluorides as the solid electrolyte have been examined by means of X-ray diffraction, DTA and EPMA methods. The eleven rare earth fluorides of yttrium and samarium through lutetium reacted with ZrO₂ to form new types of stabilized zirconias (LnFSZ) consisting of the ternary system of ZrO₂-Ln₂O₃-LnF₃. (2x+3y)ZrO₂ + (4y+2z)LnF₃ = 2(ZrO₂)_x(Ln₂O₃)_z + 3yZrF₄) where x, y and z represent the stabilizing composition at which the homogeneous solid solution with the fluorite structure is formed, and x + y + z + = 1. This reactions begins to take place at about 600 C and is completed by firing at temperatures ranging from 1000 to 1300 °C for a few hours in an argon atmosphere.     

Photoluminescence studies on rare earth titanates prepared by self-propagating high temperature synthesis method

The laser-induced luminescence studies of the rare earth titanates (R2Ti2O7) (R=La, Nd and Gd) using 355 nm radiation from an Nd:YAG laser are presented. These samples with submicron or nanometer size are prepared by the self-propagating high temperature synthesis (SHS) method and there is no known fluorescence shown by these rare earths in the visible region. Hence, the luminescence transitions shown by the La2Ti2O7 near 610 nm and Gd2Ti2O7 near 767 nm are quite interesting. Though La3+ ions with no 4f electrons have no electronic energy levels that can induce excitation and luminescence processes in the visible region, the presence of the Ti3+ ions leads to luminescence in this region.     

NMR parameters in alkali, alkaline earth and rare earth fluorides from first principle calculations

(19)F isotropic chemical shifts for alkali, alkaline earth and rare earth of column 3 basic fluorides are measured and the corresponding isotropic chemical shieldings are calculated using the GIPAW method. When using the PBE exchange-correlation functional for the treatment of the cationic localized empty orbitals of Ca(2+), Sc(3+) (3d) and La(3+) (4f), a correction is needed to accurately calculate (19)F chemical shieldings. We show that the correlation between experimental isotropic chemical shifts and calculated isotropic chemical shieldings established for the studied compounds allows us to predict (19)F NMR spectra of crystalline compounds with a relatively good accuracy. In addition, we experimentally determine the quadrupolar parameters of (25)Mg in MgF(2) and calculate the electric field gradients of (25)Mg in MgF(2) and (139)La in LaF(3) using both PAW and LAPW methods. The orientation of the EFG components in the crystallographic frame, provided by DFT calculations, is analysed in terms of electron densities. It is shown that consideration of the quadrupolar charge deformation is essential for the analysis of slightly distorted environments or highly irregular polyhedra.     

Deposition of rare earth elements from a wet-process phosphoric acid by fluorine compounds

Effect of type and consumption of fluorine reagents (HF, NH₄F·HF, NH₄F and NaF) on the deposition of rare earth elements from the wet-process phosphoric acid of the dihydrate process was examined.     

High temperature NMR approach of mixtures of rare earth and alkali fluorides: An insight into the local structure

In situ high temperature nuclear magnetic resonance in molten fluoride mixtures gives some structural picture of the complexes existing in the melt, i.e. of their nature and relative proportion. Thanks to the development of a laser heating system associated with a close crucible in boron nitride, we can describe experimentally the evolution of these complexes from the anions and the cations point of view. By ¹⁹F NMR, we have shown the existence of three kinds of fluorine atoms depending on the composition: free fluorine like in pure LiF (non-bonded), bridging fluorine in melts rich in LnF₃ in addition with terminal fluorine singly bonded to one rare earth. Data obtained by NMR spectroscopy are also combined with EXAFS measurements, again thanks to a specific development of the sample holder adapted with molten fluorides and high temperature. This study is a part of our systematic investigation of the different Alk-LnF₃ systems by NMR and EXAFS spectroscopy.     

The determination of rare earth alloying additives in special steels by neutron activation analysis

A procedure for neutron-activation analysis of cerium, lanthanum, praseodymium and neodymium, tested on more than thirty samples of steels, is described. After irradiation for 20 hrs with a neutron flux of 1.2·10¹³ n·cm⁻²·sec⁻¹ the steel samples were dissolved in aqua regia and extraction separation of iron from 6N HCl by ether was employed. The REE were separated as a group by precipitation as fluorides and hydroxydes. The individual rare-earth elements were separated from each other using a KU-2 cation exchange resin and a solution of ammonium α-hydroxyisobutirate as eluant. The separated samples were counted on a NaI(T1) γ-spectrometer.     

Analogs of the Rose center in the alkaline earth fluorides: Production by hydrolysis and identification by Raman spectroscopy

A family of molecular centers of the type (RO₂M)²⁺ is shown to exist in the alkaline earth fluorides MF₂ (M = Ca, Sr, Ba) doped with R = Sc, Y, Lu, Ho when these crystals have been hydrolyzed and subsequently X-rayed. The centers were identified with the aid of Raman spectroscopy and, in the past, with electron paramagnetic resonance (EPR).     

Systematization of the effective ionic charges in the oxides,oxide fluorides,and fluorides of the rare earth metals

Conclusion We can compare the values obtained above and in [9] for the effective ionic charges e^* for all three types of REM compound examined: fluorides, oxides, and oxide fluorides.In spite of the difference in composition, all these substances can be divided into two groups by separating the cubic (or pseudo-isotropic) crystals and the anisotropic compounds. The average values of the effective charges for each of the structural groups are given in Table 7, which also gives in parentheses the values of the ionic character of the bond, calculated according to Pauling's scheme with allowance for only the nearest homogeneous coordination sphere (for example, for CN=5 instead of 11 for the hexagonal LnF₃, etc.).It can be seen from the Table that the effective charges increase on going from the oxides to the fluorides of the REM, as expected in view of the fact that the electronegativity of fluorine is greater than that of oxygen. In all cases, the increase in the values of e^*, noted above, is observed on going from the anisotropic to the cubic crystals of these compounds. This last feature can be attributed to a decrease in the immediate coordination sphere around the REM atoms with change in the structure of the crystal; in this case the coordination sphere is understood to consist of the nearest ligands. Calculation of the degree of ionic character by the EN method with allowance for only the atoms situated at the shortest distances shows much better agreement with experiment than the classical calculation using the formal CN [8].All-Union Scientific-Research Institute for Physicotechnical and Radiotechnical Measurements. Translated from Zhurnal Strukturnoi Khimii, Vol. 14, No. 3, pp. 541–547, May–June, 1973.     

ICP-MS同时测定植物性食品中稀土元素的方法研究

建立了植物性食品中16种稀土杂质(Sc、Y、La、Ce、Pr、Nd、Sm、Eu、Gd、Tb、Dy、Ho、Er、Tm、Yb和Lu)元素的电感耦合等离子体质谱(ICP-MS)的分析方法.考察了基体效应及质谱干扰,应用In内标,有效地补偿基体效应所引起的测量偏差,建立修正公式校正质谱干扰.对照分析了参考标准物质.对所测定元素,校正曲线的相关系数为＞0.9990,方法的检出限低于2.2 pg/g(Sc为95pg/g),回收率为92%～106%,RSD优于3.2%(n=7).     

Precise determination of rare earth elements in rocks by neutron activation analysis

A pre-irradiation group separation method has been developed for the neutron activation analysis of rare earth elements (REE) and Ba in silicate rocks. REE and Ba were quantitatively separated from other elements by cation exchange column method. The chemical yield of each separation was monitored with Pr added to the sample powder before decomposition. The accuracy and precision were tested by repeated analyses of JB-1 and one analysis of BCR-1. In addition, it was found that REE distribution in a granitic rock powder was inhomogeneous and therefore special care must be taken for the sampling of granitic rock powders.     

Simultaneous multielement determination of rare earth elements by substoichiometric activation analysis

This paper presents simultaneous substoichiometric separation of four rare earth elements; samarium, europium, terbium and ytterbium. The elements are separated simultaneously and substoichiometrically by forming their complexanates with substoichiometric DTPA and extracting their unreacted parts with HTTA. Application to the determination of these elements by substoichiometric neutron activation is also presented.     

辉光放电质谱法测定稀土矿中的15种稀土元素

利用高纯铜粉与稀土矿石粉末均匀混合压片制样.混合15种高纯稀土氧化物制样建立标准工作曲线,校正15种稀土元素相对灵敏度因子,再进行定量分析.结果 表明,稀土元素工作曲线的线性方程相关系数R2均大于0.996,相对标准偏差(RSD)小于5％,满足定量分析要求.测定结果与电感耦合等离子体质谱法(ICP-MS)和电感耦合等离...     

Metrological characteristics of lead determination in rare earth phosphates by electron probe microanalysis

An equation for the calculation of the detection limit c _lim is presented. Relations for the limit of detection c _lim, limit of determination c _min, and relative error V of analyte determination are derived. The performance characteristics of lead determination in rare earth phosphates on a JXA-8100 microanalyzer are found. Under the typical conditions of the determination of monazite age (15 kV, probe current of 250 nA, count time in the positions of the line and background 400 s each) c _min using the 2σ-criterion is 0.006 wt % for an ordinary spectrometer and 0.004 wt % for a high-aperture one. In the simultaneous registration of lead by the scheme ”two ordinary plus one high-aperture channel,” c _min is reduced to 0.003%. For c _min = 0.006%, the acceptable error of age estimates V of 1–3 relative percent is attained at c _lim = 0.3-0.08%, respectively. As was found, the lowest capacity of microanalyzers for geochronology needs is 0.02–0.03% of PbO. Equations of constraints for the performance characteristics of methods ensure the revelation of the necessary conditions of analysis and compliance with them.     

An XRF method for the determination of common rare earth impurities in high purity yttrium oxide

Summary An XRF method for the determination of Eu, Gd, Tb, Dy, Ho, Er and Yb in yttrium oxide has been developed. The samples are converted to yttrium oxalate and presented to the spectrometer in the form of pressed pellets. Philips PW-1220, semiautomatic X-ray spectrometer is used for analysis. Analysis lines have been chosen after careful study of line interferences. The lower estimation limit for Yb is 0.01% and for other elements it is 0.005%. The method has been tested for its accuracy by analysing synthetic samples with known composition.

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Bestimmung von häufig vorkommenden Verunreinigungen an Seltenen Erden in Yttriumoxid hoher Reinheit mit Hilfe der Röntgenfluorescenzanalyse

Zusammenfassung Ein Verfahren zur röntgenfluorescenzanalytischen Bestimmung von Eu, Gd, Tb, Dy, Ho, Er und Yb in Yttriumoxid wurde ausgearbeitet. Die Probe wird zu Yttriumoxalat umgesetzt und in Form von Preßtabletten der RFA unterworfen. Das halbautomatische Röntgenfluorescenz-Spektrometer Philips PW-1220 wurde verwendet. Eine sorgfältige Untersuchung der Interferenzen führte zur Wahl der Analysenlinien. Die untere Bestimmungsgrenze liegt für Yb bei 0,01%, für die anderen Elemente bei 0,005%. Die Zuverlässigkeit des Verfahrens wurde anhand von synthetischen Proben bekannter Zusammensetzung geprüft.

     

Simultaneous determination of rare earth elements by using substoichiometric separation of lanthanium

An analytical method for the simultaneous determination of rare earth elements by using substoichiometry with two chelating agents, a complexon and an extracting agent, is proposed. The principle of the method is that the element which has the lowest stability constant with the complexon is separated substoichiometrically, while other elements which have higher stability constants are separated quantitatively by a single extraction. This method was applied to neutron activation analysis of rare earth elements. Lanthanum, europium and terbium in orchard leaves were determined simultaneously by using substoichiometric separation with DTPA and TTA.