- Experimental study of the enthalpy of holmium trifluoride in solid and liquid states
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The high temperature enthalpy of high purity HoF3 from 432 to 1588 K was measured by a drop calorimeter method. The temperature dependences of enthalpy and heat capacity were calculated. The values of heat capacity and enthalpy changes on melting were obtained. Original experimental values are presented.
- Lyapunov,Baginskii,Stankus
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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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- 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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- 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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p. 231 - 239
(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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- 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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- 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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- 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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