- Bright white upconversion luminescence in β-NaGd 0.794Yb0.20Ho0.001Tm0.005F 4 nanoparticles
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β-NaGd0.794Yb0.20Ho0.001Tm 0.005F4 nanoparticles were synthesized through a simple hydrothermal method. The nanoparticles crystallized well and exhibited nearly hexagonal morphology and ellipsoidal spheres, as characterized by X-ray powder diffraction and transmission electron microscopy. The β-NaGd 0.794Yb0.20Ho0.001Tm0.005F 4 nanoparticles have an average size of about 23 nm. Room-temperature bright white upconversion luminescence in β-NaGd0.794Yb 0.20Ho0.001Tm0.005F4 nanoparticles was obtained under single-wavelength diode laser excitation of 980 nm.
- De, Gejihu,Yu, Menggenqilavuqi,Bao, Siqin
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- STRUCTURE OF CUBIC YbZrF7.
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The structure of primitive-cubic YbZrF//7 has been determined using X-ray and neutron diffraction techniques. A unit cell (a equals 4. 07 A, space group Pm3m) contains one formula unit of Yb//0//. //5Zr//0//. //5F//3//. //5, with no ordering of cations, in materials prepared by rapid quenching from 1000 degree C. Metal and fluorine displacements from ideal sites are in accord with results previously obtained on Zr//0//. //8Yb//0//. //2F//3//. //2O//0//. //3. The separation between F-F pairs bridging neighboring metal ions is similar to those observed in other complex zirconium fluorides. The metal displacements, metal-fluorine distances and fluorine-fluorine distances are discussed with respect to the formation and stability of disordered fluorine-excess ReO//3-type phases.
- Poulain,Tofield
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- Anionic conductivity of several ytterbium hydrides and fluorides YbH1,8, YbH2,5, YbF2,33, YbF3 and the solid solution YbH1,8-nYbF2,33 (1,75 ≤n≤1,95)
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Measurements of conductivity have been performed up to 250°C for several ytterbium compounds including the hydrides and fluorides YbH1,8 and YbH2,5, YbF2,33, YbF3 and the solid solution YbH1,8-nYbFsu
- Bastide,Bouamrane,Carre,Claudy,Mourski,Candy,Frit,Laval
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- Preparation and characterization of high-purity metal fluorides for photonic applications
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We combine chelate-assisted solvent extraction (CASE) and hot hydrogen fluoride gas treatment to enable a general method for the preparation of high-purity binary metal fluorides. The fluorozirconate glass ZBLANI:Yb 3+ (ZrF4-BaF2-LaF3-AlF 3-NaF-InF3-YbF3), a solid-state laser-cooling material, is used as a test case to quantitatively assess the effectiveness of the purification method. The reduction of transition-metal and oxygen-based impurities is quantified directly by inductively coupled plasma mass spectrometry (ICP-MS) and indirectly by laser-induced cooling, respectively. The concentrations of Cu, Fe, Co, Ni, V, Cr, Mn, and Zn impurities in the ZrCl 2O precursor solution were measured individually by ICP-MS at various stages of the purification process. CASE was found to reduce the total transition-metal concentration from 72500 to ~100 ppb. Laser cooling was most efficient in ZBLANI:Yb3+ glass fabricated from CASE-purified metal fluoride precursors, confirming the results of the ICP-MS analysis and demonstrating the effectiveness of the purification methods in a finished optical material. High-purity metal fluorides prepared by the methods presented herein will enable new high-performance optical materials for solid-state optical refrigerators, crystals for vacuum ultraviolet (VUV) spectroscopy of the Thorium-229 nucleus, VUV optics, fibers, and thin-film coatings.
- Patterson, Wendy M.,Stark, Peter C.,Yoshida, Thomas M.,Sheik-Bahae, Mansoor,Hehlen, Markus P.
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p. 2896 - 2901
(2011/12/22)
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- Synthesis and optical properties of non-stoichiometric lanthanide (Sm, Eu, Tm, Yb) fluorides
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Nonstoichiometric samarium, europium, ytterbium, and thulium fluorides were prepared by reduction of the corresponding trifluorides with the same lanthanide metal or silicon. Crystal lattice type and lattice parameters of the compounds were determined by
- Ivanenko,Kompanichenko,Omelchuk,Zinchenko,Timukhin
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p. 841 - 847
(2010/09/17)
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- Optically active uniform potassium and lithium rare earth fluoride nanocrystals derived from metal trifluroacetate precursors
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This paper reports the first systematical synthesis of near-monodisperse potassium and lithium rare earth (RE) fluoride (K(Li)REF4) nanocrystals with diverse shapes (cubic KLaF4 and KCeF4 wormlike nanowires, nanocubes and
- Du, Ya-Ping,Zhang, Ya-Wen,Sun, Ling-Dong,Yan, Chun-Hua
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p. 8574 - 8581
(2011/01/06)
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- Thermochemical studies on the lanthanoid complexes of trifluoroacetic acid
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The thermal decomposition of the lanthanoid complexes of trifluoroacetic acid (Ln(CF3COO)3·3H2O; Ln = La-Lu) was studied by TG and DTA methods. The Ln(CF3COO) 3·3H2O complexes decompose in several stages; first dehydrate to the anhydrous state, then followed by decomposition of the anhydrous salt to a stable product of LnF3. From the endothermic and exothermic data of Ln(CF3COO)3·3H2O complexes, pyrolysis behavior of the complexes is classified into three groups: (1) La-Pr salts; (2) Nd-Gd salts; (3) Tb-Lu salts. It has been shown that all the final decomposition products were found to result in the formation of LnF3.
- Yoshimura,Ohara
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p. 573 - 576
(2008/10/09)
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- Hydrothermal synthesis of rare-earth fluoride nanocrystals
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In this paper, a hydrothermal synthetic route has been developed to prepare a class of rare-earth fluoride nanocrystals, which have shown gradual changes in growth modes with decreasing ionic radii and may serve as a model system for studying the underlying principle in the controlled growth of rare-earth nanocrystals. Furthermore, we demonstrate the functionalization of these nanocrystals by means of doping, which have shown visible-to-the-naked-eye green up-conversion emissions and may find application in biological labeling fields.
- Wang, Xun,Zhuang, Jing,Peng, Qing,Li, Yadong
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p. 6661 - 6665
(2008/10/09)
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- A thermal study of several lanthanide triflates
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Five lanthanide triflates, Ln(TfO)3·nH2O, where TfO-=CF3SO3-, Ln=La3, Nd3, Sm3, Gd3 and Yb3, and n=9 and 13, have been prepared and the thermal decomposition processes of these triflates up to 600°C were characterized by means of TG, DTA, XRD. The thermal studies have shown almost all the lanthanide triflates prepared in this study to exist as a stable nonahydrate. During the stepwise dehydration processes, it was found that mono-, di-, tri-, penta-, and heptahydrates were formed. Decompositions were found to be exothermic, and calcinations of these triflates at 600°C resulted in the formation of the corresponding LnF3. Crystal systems of the trifluorides thus obtained were hexagonal for La, Nd and Sm trifluorides, whereas those of Gd and Yb were found to be orthorhombic. The volatile decomposition products at 600°C were identified by MS, and it was revealed that the over all reaction scheme for the thermal decomposition proceeds as follows: Ln(OTf)3→LnF3+3SO2+CO2+CF 3OCF3.
- Yanagihara, Naohisa,Nakamura, Shin,Nakayama, Masayoshi
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p. 3625 - 3631
(2008/10/09)
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- Crystal chemical study of the high-temperature phase R(O,F)1.93±δ with R = Tm, Yb and Lu. Professor Dr. Georg Brauer on the occasion of his 90th birthday
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The crystal chemistry of the non-stoichiometric compounds R(O,F)x with R = Tm, Yb, and Lu with x≈1.93±0.02, which are formed by peritectoid reaction of R2O3 with RF3 at ca. 900 K, ca. 950 K and 1076 K, respectively, has been studied by X-ray powder diffraction (Guinier method). Samples of the common composition R(O,F)1.93, which were obtained by quenching from 1375±15 K to room temperature, displayed diffraction patterns of a rather complex superstructure based on the fluorite-related parent structure. The corresponding body-centered basis structure with Z = 2 was found to be orthorhombic with the following lattice parameters: R a(angstroms) b(angstroms) c(angstroms), Tm 3.7508(2) 5.3772(3) 3.8210(2), Yb 3.7341 (2) 5.3609(4) 3.8129(3), Lu 3.7008(2) 5.3371 (4)3.8170(2). This type of compound could not be found in the system Er-O-F. It is therefore concluded that its existence is restricted to the systems with R = Tm, Yb, Lu and Sc, which are characterized by the occurrence of the monoclinic, baddeleyite-type modification of stoichiometric ROF. It could be shown that for the Tm-O-F system the parent structure formula volumes of the orthorhombic vernier phase Tm(O,F)2.11, cubic α-TmOF and orthorhombic Tm(O,F)1.93 depend approximately linearly on composition. The question, whether monoclinic baddeleyite-related TmOF, which has been described in the literature, exists as a thermodynamically stable compound, is tentatively discussed.
- Mueller,Petzel,Hormann,Greis
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p. 165 - 168
(2008/10/08)
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- Organolanthanide and organoactinide oxidative additions exhibiting enhanced reactivity. 5. Stoichiometry, kinetic, and mechanistic studies of (C5Me5)2YbII·OEt2 oxidative-addition reactions and of (C5Me5)2YbIIIR (R = R, X) YbIII ...
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Full title: Organolanthanide and organoactinide oxidative additions exhibiting enhanced reactivity. 5. Stoichiometry, kinetic, and mechanistic studies of (C5Me5)2YbII·OEt2 oxidative-addition reactions and of (C5Me5)2YbIIIR (R = R, X) YbIII-Grignard reactions with alkyl and aryl halides. Evidence for the dominance of inner-sphere mechanisms. (C5Me5)2YbII·OEt 2 undergoes atom-abstraction oxidative addition with alkyl and aryl halides according to the generalized stoichiometry 1.0(C5Me5)2YbII·OEt 2 + (1 + a)RX → (1 - a)(C5Me5)2YbIIIX + (a)(C5Me5)1YbIIIX2 + (a)C5Me5R + 1.0Et2O + 1.0[R-R, R-H(alkanes), R(-H)(olefins)]. A reactive Yb-alkyl intermediate, (C5Me5)2YbIIIR, is formed from R? trapping by diamagnetic (C5Me5)2YbII. This (C5Me5)2YbIIIR intermediate and the initial product (C5Me5)2YbIIIX react further with RX in subsequent YbIII-Grignard reactions that are retarded by added Et2O and, therefore, apparently operate via an inner-sphere pathway. The observed YbIII-Grignard stoichiometries are (C5Me5)2YbIIIR + 2RX → (C5Me5)2YbIIIX2 + C5Me5R + R-R and (C5Me5)2YbIIIX + RX → (C5Me5)1YbIIIX2 + C5Me5R. The absolute rates of reaction of RX with (C5Me5)2YbII·OEt2 are found to be first-order each in (C5Me5)2YbII·OEt-2 and RX, with an added inverse dependence upon Et2O. The Et2O dependence is consistent with a requirement for a site of coordinative unsaturation and an inner-sphere pathway. Comparison of the rates of reactions of (C5Me5)2UIII(Cl)(THF) and (C5Me5)2YbII·OEt2 with RX provides compelling evidence for participation of electron transfer in these net atom-abstraction reactions.
- Finke,Keenan,Watson
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p. 263 - 277
(2008/10/08)
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- THERMODYNAMICS OF VAPORIZATION OF SAMARIUM(II) TELLURIDE AND YTTERBIUM(II) TELLURIDE: A DISCUSSION OF THE THERMOCHEMISTRY OF THE DIVALENT LANTHANOID AND ALKALINE EARTH TELLURIDES.
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The congruent vaporization of the solid monotellurides of ytterbium and samarium, both of practically stoichiometric composition, was studied over the temperature ranges 1606-1764 and 1732-1922 K, respectively, by the Knudsen effusion weight-loss technique. Using enthalpy and entropy data from the literature for gaseous LnTe, Ln, Te//2, and Te, and estimated data for solid LnTe(Ln equals Yb, Sm) it could be concluded from thermodynamic calculations that within the given temperature ranges-Ln and Te are the principal vapor species and that less than equivalent to 2. 8 and less than equivalent to 0. 9 mol percent of the vapor is present as YbTe and SmTe, respectively.
- Petzel,Ludwigs
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- PREPARATION, THERMAL CHARACTERIZATION AND X-RAY POWDER DIFFRACTION OF Ba2REF7 SUPERSTRUCTURE PHASES (RE EQUVLNT Dy-Lu, Y).
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Thermal analyses on samples of the composition (Ba, RE)F//2//,//3//3 revealed seven new compounds Ba//2REF//7 (RE EQUVLNT Dy-Lu, Y). They are stable only above about 940 degree C but can be quenched after annealing for several days at 950-1000 degree C. These phases, which are metastable at room temperature, were characterized by X-ray powder diffraction. A tetragonal distortion of the fluorite parent structure was detected, analogous to that in the Ln//3F//7, Ca//2REF//7, and Sr//2REF//7 phases. In contrast, however, the superstructure is not fully pronounced and only tripling along the c axis is observed.
- Kieser,Greis
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- The sodium fluoride-lanthanide trifluoride systems
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Phase diagrams are reported for the NaF-LnF3 binary systems. Hexagonal phases of the formula NaF·LnF3 are formed in all NaF-LnF3 systems. Above 700° the hexagonal phases NaF·PrF3 to NaF·LuF3 become converted to disordered fluorite-like cubic phases of variable composition. The composition limits of the cubic phase region are extended in proportion to the difference in ion size between Na+ and Ln3+ and vary in breadth ranging from 9 mole % (NaF-PrF3) to 25 mole % (NaF-LuF3). In each case, the LnF3-rich phase boundary was found empirically to be 5NaF·OLnF3 as the interstitial positions for allions become filled. Values of the fluorite unit-cell constants were calculated from ionic radii and found to be in good agreement with measured values. Unit-cube dimensions, a0, range from a maximum value of 5.720 A for the LnF3-rich phase in the system NaF-PrF3 to 5.425 A for the NaF-rich phase in the system NaF-LuF3. Lattice constants for the hexagonal phases NaF·LaF3 to NaF·LuF3 vary for a0 from 6.157 to 5.907 A and for C0 from 3.822 to 3.523 A. At high temperatures the 5NaF·9LnF3 phase displays disordering characteristic of the fluorite-like solid solutions; at lower temperatures cationic ordering takes place in the 5NaF·OLnF3 phases where Ln = Dy to Lu, transforming the cubic phase to an orthorhombic phase. Hexagonal NaF·LnF3 and orthorhombic 5NaF·OLnF3 compounds are partially miscible in the solid state. In the series Dy to Lu, the hexagonal phase is increasingly soluble in 5NaF·OLnF3, stabilizing the 5:9 phase to the extent that the lutetium compound is stable at temperatures below 300°, the lower temperature limit of this study. Optical properties and refractive indices of the intermediate crystalline phases in the NaF-LnF3 systems were determined as part of this investigation. Minimum liquidus temperatures in the NaF-LnF3 systems are associated with an NaF-NaF·LnF3 eutectic which varies in composition only from 25 to 29 mole % LnF3 and in temperature from 733 to 595°.
- Thoma,Insley,Hebert
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p. 1222 - 1229
(2008/10/08)
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