- 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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- Stabilization of a new superconducting phase by low temperature fluorination of La2CuO4
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When La2CuO4 is treated with pure F2 gas at 200°C, the X-ray diffraction pattern of the resulting product is characteristic of a new single phase derived from the K2NiF4-type structure. An enhancement of the orthorhombic distortion relative to the starting oxide is observed with: a=5.342 angstrom; b=5.436 angstrom and c=13.192 angstrom. Both weight uptake and increase of the c unit cell constant could be consistent with an incorporation of fluorine atoms in the lattice. This new compound is superconducting at Tc=40 K with Hc1' 700 Oe and exhibits a strong diamagnetic susceptibility (Xg= -6.13 × 10-3 emu/g) at 6 K under an applied field of 1 Oe.
- Chevalier, B.,Tressaud, A.,Lepine, B.,Amine, K.,Dance, J. M.,et al.
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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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- Isolation of niobium, tantalum, and titanium complex fluoride salts with alkali metal cations
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Fluoride and oxofluoride salts of niobium, tantalum, and titanium were isolated. They precipitated from aqueous solutions and upon washing of organic extracts with aqueous solutions of ammonium, potassium, and sodium salts. The compositions of the isolate
- Nikolaev,Kirichenko,Rys'kina
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- Solvent-assisted selective synthesis of NaLaF4 and LaF 3 fluorescent nanocrystals via a facile solvothermal approach
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A facile solvothermal approach was developed to selectively synthesize water-soluble NaLaF4 or LaF3 nanocrystals (NCs) by tuning the solvent components. In ethonal/H2O media, high-quality LaF 3 NCs were prepared by using NaF and LaCl3 as the precursors. More interestingly, thermodynamically non-preferred NaLaF 4 nanorods could be obtained when ethylenediamide (EN) was introduced to the ethonal/H2O solvent. All of the products were characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM), and the crucial effects of EN on morphology and structure of the NCs were studied. Furthermore, by doping different lanthanide ions, these LaF3 and NaLaF4 NCs could emit intense upconversion (UC) or downconversion (DC) fluorescence, which showed potential applications in color displays, light-emitting diodes, optical storage and optoelectronics.
- Wang, Zhe,Liu, Chenghui,Wang, Yucong,Li, Zhengping
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- Electrochemical fluorination of La2CuO4: A mild "chimie douce" route to superconducting oxyfluoride materials
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The fluorination of La2CuO4 was achieved for the first time under normal conditions of pressure and temperature (1 MPa and 298 K) via electrochemical insertion in organic fluorinated electrolytes and led to lanthanum oxyfluorides of general formula La2CuO4F x. Analyses showed that, underneath a very thin layer of LaF 3 (a few atomic layers), fluorine is effectively inserted in the material's structure. The fluorination strongly modifies the lanthanum environment, whereas very little modification is observed on copper, suggesting an insertion in the La2O2 blocks of the structure. In all cases, fluorine insertion breaks the translation symmetry and introduces a long-distance disorder, as shown by electron spin resonance. These results highlight the efficiency of electrochemistry as a new "chimie douce" type fluorination technique for solid-state materials. Performed at room temperature, it additionally does not require any specific experimental care. The choice of the electrolytic medium is crucial with regard to the fluorine insertion rate as well as the material deterioration. Successful application of this technique to the well-known La2CuO4 material provides a basis for further syntheses from other oxides.
- Delville,Barbut,Wattiaux,Bassat,Menetrier,Labrugere,Grenier,Etourneau
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- Synthesis of lanthanum fluoride nanocrystals and modification of their surface
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The LaF3 nanoparticles were synthesized in the presence of citric acid and glycine. The products were characterized by X-ray phase analysis, transmission electron microscopy, dynamic light scattering, and infrared spectroscopy. In the presence of organic acids the synthesis was shown to result in a decrease in size of the formed particles. The IR spectroscopic studies revealed that citric acid and glycine acted as modifiers of the surface of LaF3 particles forming a chemical bond with the surface ions La3+. A suggestion was advanced on the structure of the grafted surface layer. The features of the colloidal behavior of the systems were investigated.
- Safronikhin,Ehrlich,Lisichkin
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- PHENOMENOLOGICAL COMPARISON OF SOME HEAVY METAL FLUORIDE GLASSES IN WATER ENVIRONMENTS.
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The details of corrosive attack by water on several heavy metal fluoride glasses are given. The glasses studied contained either ZrF//4 or HfF//4 as primary constituents, or, were composed of the fluorides of zinc, thorium, barium and either yttrium or ytterbium. Polished specimens were subjected either to room temperature (RT) liquid water or to 100% relative humidity at room temperature. The degree of surface corrosion was correlated with the preparatory and compositional effects. Thermogravimetric analysis (TGA) was utilized to determine the extent of corrosion as a function of temperature and as a function of time at constant temperature in an atmosphere of RT helium saturated with water.
- Robinson,Drexhage
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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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- Phase transition and compressibility of LaF3 under pressures up to 40 GPa
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The compressibility of LaF3 (tysonite) has been studied up to 40 GPa using X-ray diffraction in a diamond anvil cell. A phase transition from tysonite to an orthorhombic phase (Cmma, No. 67) was observed at a pressure of 19 GPa at room temperature. The volume discontinuity was ΔV/V0 = -0.077 at the transition point. The cell parameters of the high-pressure phase are a=8.221(6) A?, b=8.589(9) A?, c=5.231(6) A?, Z=8 at p=16 GPa, which is accepted conventionally as equilibrium. The bulk moduli and pressure derivatives calculated by fitting V(p) data to the Birch-Murnagan equation of state are presented for both phases.
- Dyuzheva,Lityagina,Demishev,Bendeliani
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- Synthesis and characterization of single-crystalline lanthanum fluoride with a ring-like nanostructure
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LaF3 ring-like nanostructures with a diameter of less than 2 |im have been fabricated by a facile, effective, and environmentally friendly molten salt synthesis route in which NaNO3 and KNO3 (2:1 molar ratio) act as reacti
- Tian, Yang,Wen, Jing,Liu, Bin,Sui, Ning,Jin, Qionghua,Jiao, Xiuling
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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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- Two-step self-assembly of nanodisks into plate-built cylinders through oriented aggregation
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Oriented aggregation-based self-assembly of hexagonal LaF3 nanodisks with cavities into plate-built cylinders proceeding in acidic solution in the absence of any organic additive was disclosed. The self-assembly consists of two steps. First, the nanodisks sequentially aggregated together by coalescence mainly through {100} planes to form larger monocrystalline plates, followed by Ostwald ripening to smooth their surfaces. The holes on the primary nanodisks should be responsible for this intriguing growth. Second, the surface-smoothed plates were stacked face-to-face with each other along the [001] direction to construct the cylinders. The acidic condition was found to be a prerequisite for the oriented aggregations in this system. ? 2005 American Chemical Society.
- Cheng, Yao,Wang, Yuansheng,Zheng, Yuanhui,Qin, Yong
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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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- High-pressure phase transitions of LaF3 and CeF3
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The effect of high pressure on the structure of LaF3 (tysonite), CeF3, and nonstoichiometric LaF3-based solid solutions (rhombohedral system, P3c1, Z = 6) is discussed. In the systems MF 2-LaF3 with M = Pb and Sr, fluorite-like M 1-xLaxF2+x solid solutions (Fm3m, Z = 4) are obtained in the composition range 0.5 ≤ x ≤ 0.75 by quenching from 1500-1700 K at p = 10 GPa. By extrapolating the composition dependences of the lattice parameter for these cubic solid solutions, the lattice parameter of cubic LaF3 is estimated at a = 5.86 ± 0.02 A. High-pressure x-ray diffraction studies indicate that CeF3 undergoes a first-order phase transition similar to that revealed recently in LaF 3. At p = 20.6 GPa, the lattice parameters of orthorhombic CeF 3 (Cmma, Z = 8) are a = 8.062 ± 0.006 A, b = 8.457 ± 0.009 A, and c = 5.091 ± 0.006 A. The transition is accompanied by a 7.3% decrease in volume. The high-pressures structure of LaF3 and CeF3 can be thought of as a distorted modification of the structure of a hypothetical fluorite-like trifluoride. The lattice parameters of the orthorhombic and cubic cells are related by a ortho ~ bortho ~ √2 acubic and cortho ~ acubic.
- Dyuzheva,Lityagina,Demishev,Bendeliani
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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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- Surface complexation onto nanosized lanthanum fluoride
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The surface chemical modification of LaF3 nanocrystals with 4-(2-pyridylazo)resorcinol and Xylenol orange was investigated. The study of the complexes of these ligands with lanthanum ions in aqueous solution and on the LaF3 surface r
- Safronikhin,Ehrlich,Shcherba,Lisichkin
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- Luminescent properties of Nd3+-doped LaF3 core/shell nanoparticles with enhanced near infrared (NIR) emission
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A kind of Nd3+-doped LaF3 nanoparticles with core/shell structure were synthesized via a co-precipitation method. The possible formation mechanisms for the core/shell architectures were presented. The X-ray diffraction (XRD) patterns indicated that the obtained nanoparticles exhibit hexagonal structure. In comparison with LaF3:Nd core nanoparticles, the fluorescence intensity and lifetime were increased by 140% and 150% respectively in LaF3:Nd/LaF3 core/shell nanoparticles. The obvious features are mainly attributed to the formation of LaF3 shell which effectively protected the Nd3+ ions from surrounding influence. The results show that rare-earth-doped nanoparticles with core/shell structure have potential applications in biological labeling and light-emitting devices.
- Cui, Xiaoxia,She, Jiangbo,Gao, Chao,Cui, Kai,Hou, Chaoqi,Wei, Wei,Peng, Bo
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- Branched NaYF4 nanocrystals with luminescent properties
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In this article, branched NaYF4 nanocrystals have been successfully synthesized via a simple hydrothermal method. On the basis of the analysis of HRTEM and TEM images, the growth modes of the branched structure and further branching behavior have been proposed. The up- and down-conversion luminescence of branched NaYF4:Er3+/Yb3+ and NaYF4:Eu3+ have been characterized. Multiarmed NaYF 4 phosphors can be introduced into polystyrene to form composite luminescent polymers because of its special geometrical shape. In conclusion, the luminescent branched particles should be of wide potential application as building blocks in the future nanoscience and nanotechnology.
- Liang, Xin,Wang, Xun,Zhuang, Jing,Peng, Qing,Li, Yadong
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- Preparation of high purity lanthanum compounds for use in fluoride optical fibers
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The preparation of ultrapure lanthanum nitrate by co-precipitation is described. Preparation of high-purity lanthanum carbonate from the pure nitrate is also described. Hydrofluorination of pure lanthanum carbonate produces high-purity lanthanum fluoride
- Ewing,Buckner,Jaganathan
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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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- Improvement of structural and electrochemical properties of commercial LiCoO2 by coating with LaF3
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Commercial LiCoO2 has been modified with LaF3 as a new coating material. The surface modified materials were characterized by X-ray diffraction (XRD), transmission electronic microscopy (TEM), field emission scanning electron microscopy (FE-SEM), auger electron spectroscopy (AES) and galvanostatic charge-discharge cycling. The LaF3-coated LiCoO 2 had an initial discharge specific capacity of 177.4 mAh g -1 within the potential ranges 2.75-4.5 V (vs. Li/Li+), and showed a good capacity retention of 90.9% after 50 cycles. It was found that the overcharge tolerance of the coated cathode was significantly better than that of the pristine LiCoO2 under the same conditions - the capacity retention of the pristine LiCoO2 was 62.3% after 50 cycles. The improvement could be attributed to the LaF3 coating layer that hinders interaction between LiCoO2 and electrolyte and stabilizes the structure of LiCoO2. Moreover, DSC showed that the coated LiCoO 2 had a higher thermal stability than the pristine LiCoO2.
- Yang, Zhanxu,Qiao, Qingdong,Yang, Wensheng
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- Single-crystalline and monodisperse LaF3 triangular nanoplates from a single-source precursor
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Single-crystalline and monodisperse LaF3 triangular nanoplates (2.0 × 16.0 nm) in trigonal tysonite structure were synthesized by the thermolysis of a single-source precursor (SSP), La(CF3COO)3, in a hot oleic acid/octadecene solution. The combined use of SSP and coordinating and noncoordinating solvents was demonstrated to have played key roles in the formation of such high-quality nanoplates, which could spontaneously organize into two types of superlattices (edge-to-edge and face-to-face) on a large area. This SSP approach has advantages of one-step, mass production, and easy operation, and may represent a rather general route toward metal fluoride nanocrystals. Copyright
- Zhang, Ya-Wen,Sun, Xiao,Si, Rui,You, Li-Ping,Yan, Chun-Hua
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- Luminescence of Eu3+ ions in LaF3 laser host
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Rare earth doped fluorides have been used in laser applications. Not much is known about the effect of ionizing radiation on the lasing and other properties of fluorides. The colour centre formation by γ-ray irradiation in pure and Eu3+ doped L
- Dhoble
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- 19F MAS-NMR studies of strontium oxyfluoride aluminosilicate glass
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Local environment of fluorine atoms in the lanthanum oxyfluoride aluminosilicate glasses and glass-ceramics modified by SrO was studied by solid state 19F MAS-NMR spectroscopy and X-ray diffraction. The effect of strontium concentration on the formation of crystalline LaF3 phase was determined, as a function of heat treatment conditions. In all glasses studied, the F-Me(n) (where Me = Sr, La), but no Na-F species were observed. The presence of F-La,Sr(n) units, in which fluorine is coordinated by both lanthanum and strontium, was detected in the glass with higher content of SrO. Supplementary XRD analysis of this series confirmed that an increase of strontium contents leads to the formation of Sr0.69La 0.31F2.31 and LaSr2F7, instead of the pure LaF3 only.
- Sroda,Olejniczak
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- Microwave-assisted one-pot synthesis of water-soluble rare-earth doped fluoride luminescent nanoparticles with tunable colors
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Polyethyleneimine (PEI) functionalized multicolor luminescent LaF 3 nanoparticles were synthesized via a novel microwave-assisted method, which can achieve fast and uniform heating under eco-friendly and energy efficient conditions. The as-prepared nanoparticles possess a pure hexagonal structure with an average size of about 12 nm. When doped with different ions (Tb3+ and Eu3+), the morphology and structure of the nanoparticles were not changed, whereas the optical properties varied with doped ions and their molar ratio, and as a result emission of four different colors (green, yellow, orange and red) were achieved by simply switching the types of doping ions (Eu3+ versus Tb3 +) and the molar ratio of the two doping ions.
- Mi, Cong-Cong,Tian, Zhen-Huang,Han, Bao-Fu,Mao, Chuan-Bin,Xu, Shu-Kun
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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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- 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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- Dielectric, modulus and impedance analysis of LaF3 nanoparticles
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Lanthanum fluoride nanoparticles have been synthesized by the simple method of direct precipitation from an aqueous solution. TG/DTA analysis confirms the sample formation at low temperature (300 °C). Structure of LaF3 nanoparticles has been an
- Arun Kumar,Selvasekarapandian,Nithya,Sakunthala,Hema
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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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- 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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- Solubilities of lanthanum oxide in fluoride melts: Part I. Solubility in M3AlF6 (M = Li, Na, K)
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Solubility of lanthanum oxide was measured by thermal analysis. The solubility in alkali cryolites is rather high, because of chemical reactions between lanthanum oxide and cryolites. In Li3AlF6-La 2O3, alumina
- Ambrová,Jurisová
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p. 105 - 108
(2008/10/09)
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- Sol-Gel Synthesis of Silica-Based Oxyfluoride Glass-Ceramic Thin Films: Incorporation of Eu3+ Activators into Crystallites
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Transparent oxyfluoride glass-ceramic thin films were prepared using a sol-gel method starting from rare-earth trifluoroacetate/silicon alkoxide solutions. SiO2-LaF3 and SiO2-LaOF glass-ceramics were formed by heating at temperatures of 300°-500°C and 600°-900°C, respectively. Eu3+ activators were successfully incorporated into oxyfluoride crystals, as evidenced by their luminescent properties, such as capability of a charge-transfer (O2--Eu3+) excitation, suppression of a multiphonon relaxation, and occurrence of a cross-relaxation at low Eu3+ concentrations. As a result, the films exhibited strong red emission by ultraviolet excitation. The incorporation supposedly originated from decomposition of the (La,Eu)-trifluoroacetates in the silica-gel matrix.
- Fujihara, Shinobu,Kato, Takayoshi,Kimura, Toshio
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p. 2716 - 2718
(2008/10/08)
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- Study of phase transition and volume thermal expansion in a rare-earth (RE) oxyfluoride system by high-temperature XRD (RE=La, Nd, Sm, Eu and Gd)
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Volume thermal expansion behaviour of a number of rare-earth oxyfluorides (REOF) have been studied using high-temperature X-Ray diffractometry (HT-XRD) in the 298-1075 K range in air. The studies revealed an anomalous expansion for each compound associated with phase transition. The phase transition temperature and the coefficient of volume thermal expansion of five compounds in REOF series determined by this method are reported and compared with our earlier results obtained by dilatometry.
- Achary,Ambekar,Mathews,Tyagi,Moorthy
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p. 239 - 243
(2008/10/09)
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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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