- Phase analyses of lanthanide oxide fluorides
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Approximate composition limits and lattice parameters of the rhombohedral and tetragonal phases observed in the system LnO1-xF1+2x (Ln = Nd, Gd, Er) are reported. Variation of the c/a ratio of the tetragonal phase with atomic number is noted and discussed. The rhombohedral to cubic transition temperatures of LnO1-xF1+2x (Ln = La, Nd, Sm, Eu, Gd, Tb, Dy, Y, Ho, and Er) determined from differential thermal analysis are reported and the transition is discussed. Thermal expansion data are reported for NdOF and its mode of thermal decomposition is indicated.
- Shinn, Dennis B.,Eick, Harry A.
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- Synthesis and characterization of Ba1-xNdxF2+x (0.00 ≤ x ≤ 1.00)
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A series of mixed fluorides with general composition Ba1-xNdxF2+x (0.00 ≤ x ≤ 1.00) was prepared by vacuum heat treatment of the mixture of starting fluorides, and analyzed by powder XRD. From the XRD analysis, the low temperature phase equilibria in BaF2-NdF3 system is elucidated. The initial compositions in this series, that is, up to the nominal composition Ba0.65Nd0.35F2.35 (x ≤ 0.35) exist as cubic fluorite-type solid solution. Beyond the solid solution limit, that is, x ≥ 0.35, a rhombohedral fluorite related ordered phase is observed. Further, NdF3-rich compositions (x ≥ 0.50) exist as a mixture of rhombohedral ordered phase and NdF3 (tysonite)-type phase. About 10 mol% of BaF2 could be retained in the NdF3 lattice, forming a tysonite-type solid solution, under the short annealed and slow cooled conditions.
- Grover,Achary,Patwe,Tyagi
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- Laser development of rare-earth doped crystals
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Rare earth doped laser crystals present good optical properties providing most of the solid state lasers available today. In particular, some fluoride crystals are capable of forming solid solution with several rare earth fluorides, allowing one to take full advantage of the energy transfer mechanisms that might occur among them. LiREF4 (RE = rare earth) crystals, for example, are so flexible that in some cases the doping concentration can go up to 100%. The Nd:LiLuF4 (Nd:LuLF) system has a 1047-nm emission bandwidth 25% larger than Nd:YLF, which makes it very promising for laser mode-locked operation. Nevertheless, lutetium compounds are very difficult to obtain, therefore Nd-doped mixed crystals grown from LiF-Y1-xLuxF3 (0A new laser medium was obtained for the Nd:LiLu0.5Y0.5F4 crystal, which presents a Nd emission bandwidth close to the Nd:LuLF (1.82 nm). The mode-locked operation in a diode pumped laser system using the KLM technique was performed and pulses of 4.5 ps were readily obtained. It is also shown that the LiGdF4 (GLF) is a promising host for diode pumped high power Nd lasers which require crystals with higher dopant concentrations. Another example is the Ho:LiYF4 (Ho:YLF) laser operating at 2065 nm obtained as a result of concentration optimization of the sensitizers Er and Tm. The optimization was based on a model comprising the various energy transfer mechanisms that take place in these long lived metastable states, heavily dependent on the dopants concentration. As a quasi-four-level system, the Ho concentration must be kept very small (≤0.005 mol%). The laser operation was optimized by the dynamical coupling of pump and laser modes, and by the dopants optical cycle. These optimizations resulted in a CW Ho laser with 2 W output, in a diode pumped system operation.
- Vieira Jr.,Ranieri,Tarelho,Wetter,Baldochi,Gomes,De Matos,De Rossi,Nogueira,Courrol,Barbosa,Maldonado,Morato
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- Heterometallic Ln/Hg compounds with fluorinated thiolate ligands
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The early lanthanide benzenefluorothiolates (Ln(SC6F 5)3; Ln = La, Ce, Pr, Nd, Sm, Gd) react with Hg(SC 6F5)2 in DME to form ionic heterometallic compounds with Ln cations and Hg anions. X-ray diffraction analyses of all compounds reveal an isostructural series with the general formula [(DME) 3Ln(SC6F5)2]2[Hg 2(SC6F5)6]. In the structures, a fluorothiolate ligand has been extracted from the Ln coordination sphere that is saturated with three neutral DME donor ligands and a dative interaction between one ortho fluorine and the Ln. Distances between Ln and F do not vary simply with Ln ionic radius. There are two Ln cations with charge balanced by a Hg 2(SC6F5)6 dianion composed of two distinctly nonideal Hg(II) tetrahedra, all connected through a series of π-π interactions that link cations with anions in a one-dimensional array and anions to anions in a more complex 2D network.
- Banerjee, Santanu,Emge, Thomas J.,Brennan, John G.
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- Solubility of YF3, CeF3, PrF3, NdF 3, and DyF3 in solutions containing sulfuric and phosphoric acids
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The solubility of YF3, CeF3, PrF3, NdF3, and DyF3 in solutions containing 0-4.496% mol/L (0-35 wt %) of H2SO4 and 0-27.6 g/L of H 3PO4 (0-20 g/L of P2
- Lokshin,Tareeva
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- Spectroscopic characterization of Ho3+ ion-doped fluoride glass
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Among the new optical materials available, fluoride glass, which has an extended transmission window, is emerging as an important material for use in optical fibers, lasers, sensors, etc. Here, we analyze the spectroscopic properties of Ho3+ ions in a fluoroindate glass based on absorption measurements. Ho3+-doped fluoroindate glass with the composition (40 - x)InF3-20SrF2-20ZnF2-16BaF2-2GdF3-2NaF-xHoF3, x = 1.0, 2.0, 2.5, 3.0, 4.0, 5.0, 6.0, 8.0 and 9.0 mol%, was prepared under an argon atmosphere. Absorption spectra in the range 300-2200 nm were then obtained. The experimental oscillator strength fExp. was calculated from the areas under absorption bands. Using Judd-Ofelt theory and least-squares fitting, the phenomenological intensity parameter Ωλ (λ = 2, 4, 6) and the theoretical oscillator strength fCal. were calculated. To evaluate potential applications and to analyze the properties of Ho3+ ions in these host glasses, the following spectroscopy parameters were calculated: the transition probability between multiplets AJJ′, the branching ratio βJJ′, the radiative lifetime τR, the peak cross-section for stimulated emission σp, and the emitting-level multiphonon rate WNR for each band. The results were compared with those reported in the literature for similar glasses of the same concentration.
- Florez,Oliveira,Flórez,Gómez,Nunes
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- Optical properties of Nd3+-doped fluorophosphate glasses
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Optical absorption spectra of Nd3+-doped fluorophosphate glasses of the type 75NaPO3-24AF2-1NdF3 (A = Li, Na K) and of the type 75NaPO3-24AF2-1NdF3 (A = Ca, Sr, Ba, Zn, Cd) have been recorded. The dipole strengths are parameterized in terms of three phenomenological Judd-Ofelt intensity parameters Ωλ (λ = 2, 4 and 6). With the knowledge of these intensity parameters, the probability for spontaneous emission, the branching ratios and the radiative lifetime are calculated. The relation between the spectral intensities and the glass composition is discussed. The optical properties of the fluorophosphate glasses are compared with those of phosphate and fluoride glasses. It is shown that the choice of the cation only has a minor influence on the spectral intensities. The spectral behaviour of the fluorophosphate glasses is intermediate between the spectral behaviour of pure phosphate and fluoride glasses.
- Binnemans,Van Deun,Gorller-Walrand,Adam
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- Synthesis and characterization of LnF(HF)(BF4)2 (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, and Dy), and crystal structures of LnF(HF)(BF4)2 (Ln = Pr, Nd) and La(BF4) 3
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Rare earth trifluorides (Ln = La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, and Dy) react with boron trifluoride in anhydrous hydrogen fluoride (aHF) at room temperature. Products were found to be only sparingly soluble in aHF where the solubility decreases from lantha
- Mazej, Zoran,Goreshnik, Evgeny,Hironaka, Kohei,Katayama, Yasushi,Hagiwara, Rika
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- Hydrofluoride synthesis of fluorides of some rare-earth elements
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Thermal gravimetric, X-ray phase, IR spectroscopic, and chemical analyses were applied to study the reaction of yttrium and neodymium oxides with NH 4HF2.
- Kalinnikov,Makarov,Tikhomirova,Elizarova,Kuznetsov
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- High-quality sodium rare-earth fluoride nanocrystals: Controlled synthesis and optical properties
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We report a general synthesis of high-quality cubic (α-phase) and hexagonal (β-phase) NaREF4 (RE: Pr to Lu, Y) nanocrystals (nanopolyhedra, nanorods, nanoplates, and nanospheres) and NaYF 4:Yb,-Er/Tm nanocrystals (nanopolyhedra and nanoplates) via the co-thermolysis of Na(CF3COO) and RE(CF3-COO)3 in oleic acid/oleylamine/1-octadecene. By tuning the ratio of Na/RE, solvent composition, reaction temperature and time, we can manipulate phase, shape, and size of the nanocrystals. On the basis of its α → β phase transition behavior, along the rare-earth series, NaREF4 can be divided into three groups (I: Pr and Nd; II: Sm to Tb; III: Dy to Lu, Y). The whole controlled-synthesis mechanism can be explained from the point of view of free energy. Photoluminescent measurements indicate that the value of / 610//590 and the overall emission intensity of the NaEuF4 nanocrystals are highly correlative with the symmetries of the Eu3+ ions in both the lattice and the surface.
- Mai, Hao-Xin,Zhang, Ya-Wen,Si, Rui,Yan, Zheng-Guang,Sun, Ling-Dong,You, Li-Ping,Yan, Chun-Hua
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- Phase relation studies in Pb1-xM′xF 2+x systems (0.0≤x≤1.0; M′=Nd3+, Eu 3+ and Er3+)
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In this communication we report the synthesis and characterization of a series of compounds with the general composition Pb1-xM′ xF2+x, (0.0≤x≤1.0; M′=Nd3+, Eu 3+ and Er3+) to elucidate the detailed phase relations between PbF2 and M′F3. These three rare-earth fluorides were selected so as to delineate the effect of ionic size on the phase relations. In all the three systems, fluorite-type solid solutions are formed at the PbF2 rich end. The solid solubility limits of NdF 3, EuF3 and ErF3 in the PbF2 lattice, as observed from this study, are 30, 25 and 15mol%, respectively. In PbF2-NdF3 system, beyond the fluorite-type solid solutions, NdF3 phase is observed. However, in both PbF 2-EuF3 and PbF2-ErF3 systems, certain fluorite related ordered phases, namely, a rhombohedral phase with about 40mol% of EuF3 or ErF3 in PbF2, and a tetragonal phase with 45-50mol% of ErF3 in PbF2, are observed. In all the three systems, no solubility of the PbF2 in the hexagonal or orthorhombic rare-earth fluoride lattice is observed. This is the first report on phase relation in these three systems under short annealed and slow cooled condition.
- Tyagi,Patwe,Achary,Mallia
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- Lanthanide pentafluorophenolates. Synthesis, structure and luminescent properties
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The pentafluorophenolates of lanthanides Ln(OC6F 5)3 (Ln = Nd (1), Tb (2), Er (3)) were prepared by the reactions of pentafluorophenol with appropriate silylamides Ln[N(SiMe 3)2]3 in benzene or toluene solution. The same reactions in ether or methanol medium afforded the solvated complexes Ln(OC 6F5)3(Et2O)3 (Ln = Nd (4), Eu (5), Tb (6), Er (7), Gd (8)) or Nd(OC6F5) 3(MeOH)3 (9), respectively. The phenanthroline complexes Ln(C6F5O)3(phen) (Ln = Pr (10), Nd (11), Er (12)), Ln(OC6F5)3(phen)2 (Ln = Sm (13), Tb (14), Ho (15), Ln(OC6F5)3(phen) 2(Et2O) (Ln = Eu (16), Yb (17)), and Ln(OC 6F5)3(phen)(Et2O)3 (Ln = Eu (18), Nd (19), Ce (20), Dy (21)), Ln(OC6F5) 3(phen)2(H2O) (Ln = Sm (22), Ho (23)), and Gd(OC6F5)3(phen)2(MeOH) (24) were obtained when the reactions were carried out in the presence of 1,10-phenanthroline. The complexes with pyridine Tb(OC6F 5)3(py)5 (25) and 2,2′-bipyridyl Ln(OC6F5)3(bpy)2 (Ln = Tb (26), Yb (27)) were synthesized similarly. Compounds 7, 22, 23, and 24 were characterized by X-ray analysis. The complexes Ln(OC6F5)3 decompose above 150 C in vacuum to give lanthanide fluorides and octofluorodibenzo-p-dioxine. Phenanthroline derivatives are stable up to 310 C. Luminescence spectra of all the obtained complexes in visible region contain a broad band of ligand-centered emission peaked at 405-415 nm. Spectra of samarium 13, europium 5, 16, 18 and terbium 14, 25, 26 derivatives display also the characteristic narrow bands of Sm3+, Eu3+ and Tb 3+ ions.
- Maleev, Alexander A.,Fagin, Anatoly A.,Ilichev, Vasily A.,Lopatin, Mikhail A.,Konev, Alexey N.,Samsonov, Maksim A.,Fukin, Georgy K.,Bochkarev, Mikhail N.
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p. 126 - 132
(2013/11/19)
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- X-ray magnetic circular dichroism (XMCD) study of a methoxide-bridged DyIII-CrIII cluster obtained by fluoride abstraction from cis-[CrIIIF2(phen)2]+
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An isostructural series of dinuclear chromium(III)-lanthanide(III) clusters is formed by fluoride abstraction of cis-[CrF2(phen) 2]+ by Ln3+ resulting in LnF3 and methoxide-bridged Cr-Ln clusters (Ln = Nd (1), Tb (2), Dy (3)) of formula [CrIII(phen)2(μ-MeO)2Ln(NO3) 4]?xMeOH (x = 2-2.73). In contrast to fluoride, methoxide bridges in a nonlinear fashion, which facilitates chelation. For 3, X-ray magnetic circular dichroism (XMCD) provides element-specific magnetization curves that are compared to cluster magnetization and susceptibility data acquired by SQUID magnetometry. The combination of XMCD and SQUID is able to resolve very small magnetic coupling values and reveals a weak Cr III-DyIII coupling of j = -0.04(3) cm-1. The DyIII ion has a ground-state Kramers doublet of mJ = ±13/2, and the first excited doublet is found to be mJ = ±11/2 at an energy of δ = 57(21) cm-1. The Cr III ion exhibits a uniaxial anisotropy of DCr = -1.7(1.0) cm-1. Further, we observe that a weak anisotropic coupling of dipolar origin is sufficient to model the data, suggesting that methoxide bridges do not play a significant role in the magnetic coupling for the present systems.
- Dreiser, Jan,Pedersen, Kasper S.,Birk, Torben,Schau-Magnussen, Magnus,Piamonteze, Cinthia,Rusponi, Stefano,Weyhermueller, Thomas,Brune, Harald,Nolting, Frithjof,Bendix, Jesper
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p. 7842 - 7847
(2012/09/22)
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- Infrared spectra and quantum chemical calculations of the bridge-bonded HC(F)LnF2 (Ln = La-Lu) complexes
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Lanthanide metal atoms, produced by laser ablation, were condensed with CHF3 (CDF3) in excess argon or neon at 4 K, and new infrared absorptions are assigned to the oxidative addition product fluoromethylene lanthanide difluoride complex on the basis of deuterium substitution and density functional theory frequency calculations. Two dominant bands in the 500 cm-1 region are identified as metal-fluorine stretching modes. A band in the mid-600 cm-1 region is diagnostic for the unusual fluorine bridge bond C-(F)-Ln. Our calculations show that most of the bridged HC(F)LnF2 structures are 3-6 kcal/mol lower in energy than the open CHF-LnF2 structures, which is in contrast to the open structures observed for the corresponding CH2-LnF2 methylene lanthanide difluorides. Argon-to-neon matrix shifts are 15-16 cm -1 to the blue for stretching of the almost purely ionic Ln-F bonds, as expected, but 10 cm-1 to the red for the bridge C-(F)-Ln stretching mode, which arises because Ar binds more strongly to the electropositive Ln center, decreasing the bridge bonding, and thus allowing a higher C-F stretching frequency.
- Gong, Yu,Wang, Xuefeng,Andrews, Lester,Chen, Mingyang,Dixon, David A.
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p. 4443 - 4452
(2011/10/10)
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- The versatility of solid-state metathesis reactions: From rare earth fluorides to carboiimides
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The new carbodiimide compounds LaF(CN2) and LiPr 2F3(CN2)2 were obtained as crystalline powders by solid-state metathesis reactions from 1:1 molar ratios of REF3 (RE = rare earth) and Lisu
- Unverfehrt, Leonid,Glaser, Jochen,Stroebele, Markus,Tragl, Sonja,Gibson, Katharina,Meyer, H.-Juergen
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p. 479 - 483
(2009/06/17)
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- Synthesis of REF3 (RE = Nd, Tb) nanoparticles via a solvent extraction route
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NdF3 and TbF3 nanoparticles were successfully synthesized via a solvent extraction route using Cynex923 (R3P{double bond, long}O). X-ray diffraction (XRD) study showed that pure hexagonal phase NdF3 and pure ort
- Guo, Fuqiang,Li, Hongfei,Zhang, Zhifeng,Meng, Shulan,Li, Deqian
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p. 1565 - 1568
(2009/07/10)
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- Controlled hydrothermal growth and up-conversion emission of NaLnF 4 (Ln = Y, Dy-Yb)
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The controlled hydrothermal preparation of NaYF4 as both cubic and hexagonal phase types with specific associated morphologies, nanospheres and microtubes, respectively, has been achieved in the absence of organic solvents. The hexagonal NaYF4 compound can be prepared in novel microtubular form and directly co-doped with Yb3+/Er3+ ions. When excited by infrared light of 980 nm, these hexagonal NaYF4 microtubes display strong green up-conversion emission, which was much more intense than that of cubic NaYF4 or hexagonal NaYF4 nanoparticles. Other related hexagonal-prismatic microtubes of NaLnF4 (Ln = Dy-Yb) were also synthesized. A growth mechanism for the microtubes is proposed. In general, the diameter of the hexagonal NaLnF4 microtubes is strongly dependent on the Ln3+ size and increases as the rare-earth ionic radius decreases.
- Zhuang, Jianle,Liang, Lifang,Sung, Herman H. Y.,Yang, Xianfeng,Wu, Mingmei,Williams, Ian D.,Feng, Shouhua,Su, Qiang
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p. 5404 - 5410
(2008/10/09)
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- Synthesis and characterization of ternary NH4Ln 2F7 (Ln = Y, Ho, Er, Tm, Yb, Lu) nanocages
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In this paper, a new class of NH4Ln2F7 (Ln = Y, Ho, Er, Tm, Yb, Lu) inorganic nanocages that has been discovered will be presented. A facile template-free synthetic route was developed for one step, high yield, and large scale synthesis of ternary NH4Ln 2F7 (Ln = Y, Ho, Er, Tm, Yb, Lu) nanocages. On the basis of our studies, these nanocages are thermodynamically stable forms of this group of NH4Ln2F7 compounds. The tendency of NH 4Ln2F7 (Ln = Y, Ho, Er, Tm, Yb, Lu) to form these new-type nanostructures is believed to have a close relationship with their inherent layered structures, similar to that of inorganic fullerene-like nanoparticles. This new type of nanocage can be easily doped with other lanthanide ions, which may endow these nanocages with novel properties. Wiley-VCH Verlag GmbH & Co. KGaA, 2006.
- Liang, Xin,Wang, Xun,Wang, Leyu,Yan, Ruoxue,Peng, Qing,Li, Yadong
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p. 2186 - 2191
(2007/10/03)
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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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- Synthesis, structure and VUV luminescent properties of rubidium rare-earth fluorides
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RbF-LnF3 (Ln=rare earth) systems were synthesized by hydrothermal technique. Under the hydrothermal condition, the light rare-earth elements form LnF3 (Ln=La-Nd), while the heavy ones form RbLn 2F7 (Ln=Y, Er, Yb and Lu) with the RbEr2F 7 structure type. RbLn3F10 compounds were found for the in-between rare-earth cations (Ln=Eu-Tm and Y), which crystallize exclusively in the cubic γ-KYb3F10-type structure. The luminescent properties under vacuum ultraviolet light were studied for the Eu3+-doped RbLn3F10 (Ln=Y, Gd) and a high quantum efficiency of about 150% was observed for RbGd3F 10:Eu3+.
- You, Fangtian,Huang, Shihua,Liu, Shuman,Tao, Ye
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p. 2777 - 2782
(2008/10/09)
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- Fullerene-like rare-earth nanoparticles
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A low-temperature hydrothermal synthesis has been employed to prepare the title materials in the form of their fluorides and hydroxides. Electron microscopy reveals their hollow and closed-cage structures (see HRTEM image). Such nanostructures can be expected to bring forth new opportunities in important research and application fields, such as biological labeling, luminescence, and catalysis.
- Wang, Xun,Li, Yadong
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p. 3497 - 3500
(2007/10/03)
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- Hydrothermal syntheses and crystal structure of NH4Ln3F10 (Ln = Dy, Ho, Y, Er, Tm)
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Ammonium rare earth fluorides NH4Ln3F10 (Ln = Dy, Ho, Y, Er, Tm) were synthesized by a hydrothermal method. Two polymorphs, of the hexagonal β-KYb3F10 and the cubic γ-KYb3F10 structure types, were formed under hydrothermal conditions for most of the rare earth fluorides except NH4Dy3F10, for which only the cubic γ-phase was obtained. The crystal structures of MLn3F10 (M = alkaline metal, NH4+ and Ln = rare earth) show a strong correlation to the ratio of ionic radii (RM/RLn), which has been expressed in a structure phase diagram of the ionic radii of univalent and rare earth cations.
- Kang,Wang,You,Lin
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p. 358 - 362
(2008/10/08)
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- Judd-Ofelt intensity parameters of trivalent lanthanide ions in a NaPO3-BaF2 based fluorophosphate glass
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The spectroscopic properties of the trivalent lanthanide ions Pr3+, Nd3+, Sm3+, Eu3+, Tb3+, Dy3+, Ho3+, Er3+ and Tm3+ in the fluorophosphate glass 75NaPO3-24BaF2-1LnF3 (where Ln = lanthanide ion) are described. The dipole strengths of the transitions in the absorption spectrum are parameterized in terms of three Ωλ (λ = 2, 4 and 6) Judd-Ofelt intensity parameters.
- Van Deun,Binnemans,Gorller-Walrand,Adam
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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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- Study of phase transition in REOF system by dilatometry (RE = La, Nd, Sm, Gd, Eu and Y)
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Bulk thermal expansion behaviour of a number of rare earth oxyfluorides (REOF) has been studied using dilatometry in the temperature range 289-923 K in air. The studies revealed an anomalous expansion for each compound associated with the phase transition. The phase transition temperatures and the coefficients of average linear thermal expansion of the compounds determined by this method are reported.
- Mathews,Tyagi,Moorthy
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p. 165 - 167
(2008/10/09)
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- Phase equilibria in rare-earth chloride-fluoride and rare-earth chloride-magnesium fluoride systems
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Equilibrium phase diagrams for the systems LaCl3-LaF3, CeCl3-CeF3, NdCl3-NdF3, LaCl3-MgF2, CeCl2-MgF2, and NdCl3-MgF2 were determined by differential thermal analysis. A eutectic was observed at 654° ± 4°C and 31 molpercent LaF3 in the LaCl3-LaF3 system, 620° ± 3°C and 31.5 molpercent CeF3 in the CeCl3-CeF3 system, 615° ± 5°C and 29 molpercent NdF3 in the NdCl3-NdF3 system, 723° ± 5°C and 30 molpercent MgF2 in the LaCl3-MgF2 system, 690° ± 3°C and 26 molpercent MgF2 in the CeCl3-MgF2 system, and 655° ± 3°C and 26.5 molpercent MgF2 in the NdCl3-MgF2 system. A compound, NdCl3·NdF3, decomposing at 595° ± 5°C, also was observed in the NdCl3-NdF3 system. On the basis of agreement between the activities calculated by the Temkin model and the Clausius-Clapeyron equation, the melts of the rare-earth (RE) chloride and fluoride consisted of RE3+, Cl-, and F-. The melts formed with a rare-earth chloride and magnesium fluoride consisted of RE3+, Mg2+, RECl63-, and MgF42-.
- Sharma, Ram A.
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p. 2582 - 2586
(2008/10/08)
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- Thermodynamics of the rhombohedral-cubic phase transition of ROF with R=Y, La, Pr, Nd, Sm-Er
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The temperatures and enthalpies of the rhombohedral-cubic phase transition of stoichiometric ROF with R=Y, La, Pr, Nd, Sm-Er, have been determined by differential scanning calorimetry. The temperatures of transition are found in the range 742-880 K in sat
- Petzel,Marx,Hormann
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- Synthesis and thermal study of tris(ammonium) hexafluoro metallates(III) of some rare earths
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Fluorination of oxides of rare earths using ammonium hydrogen fluoride at room temperature gave new compounds 3MF6*nH2O, where M = Y, La, Nd, and Pr.In the case of cerium, 4CeF8 is formed.The course of thermal decomposition of all these compounds is studied by thermogravimetry/differential thermal analysis (TG/DTA) and X-ray powder diffraction(XRD).Key words: hexafluoro metallates, rare earths, ammonium hydrogen fluoride, thermal decomposition, X-ray diffraction.
- Patwe, S. J.,Wani, B. N.,Rao, U. R. K.,Venkateswarlu, K. S.
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p. 1815 - 1818
(2007/10/02)
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- Thermochemistry of rare-earth trifluorides, I. Fluorine bomb calorimetric determination of the enthalpies of formation of LaF3, PrF3, NdF3, GdF3, DyF3, HoF3, and ErF3
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The energies of combustion of high-purity samples of lanthanum, praseodymium, neodymium, gadolinium, dysprosium, holmium, and erbium in fluorine to form the respective trifluorides were measured in a bomb calorimeter.The results obtained for the standard enthalpies of formation, ΔH0f(298.15 K)/kJ mol-1, are as follows: LaF3, -(1699.5 +/- 2.0); PrF3, -(1689.1 +/- 2.6); NdF3, -(1679.4 +/- 1.9); GdF3, -(1699.3 +/- 2.3); DyF3, -(1692.0 +/- 1.9); HoF3, -(1697.8 +/- 2.3); and ErF3, -(1693.6 +/- 1.9).
- Johnson, Gerald K.,Pennell, Rebecca G.,Kim, Kwang-Yil,Hubbard, Ward N.
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p. 125 - 136
(2007/10/02)
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