Hydrothermal syntheses and crystal structure of NH4Ln3F10 (Ln = Dy, Ho, Y, Er, Tm)

Kang,Wang,You,Lin

, p. 358 - 362 (2001)

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.

Jianming, Xu,Zhitong, Sui,Changzhen, Wang

, p. L9 - L12 (1992)

Isolation of niobium, tantalum, and titanium complex fluoride salts with alkali metal cations

Nikolaev,Kirichenko,Rys'kina

, p. 1070 - 1075 (2009)

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

Greis, O.,Bevan, D. J. M.

, p. 113 - 114 (1978)

Petzel, T.,Marx, V.,Potthast, J.,Ahnen, Th.

, p. 319 - 328 (1992)

PHENOMENOLOGICAL COMPARISON OF SOME HEAVY METAL FLUORIDE GLASSES IN WATER ENVIRONMENTS.

Robinson,Drexhage

, p. 1101 - 1112 (1983)

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.

Phase transition and compressibility of LaF3 under pressures up to 40 GPa

Dyuzheva,Lityagina,Demishev,Bendeliani

, p. 59 - 61 (2002)

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.

The versatility of solid-state metathesis reactions: From rare earth fluorides to carboiimides

Unverfehrt, Leonid,Glaser, Jochen,Stroebele, Markus,Tragl, Sonja,Gibson, Katharina,Meyer, H.-Juergen

, p. 479 - 483 (2009)

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

Study of phase transition in REOF system by dilatometry (RE = La, Nd, Sm, Gd, Eu and Y)

Mathews,Tyagi,Moorthy

, p. 165 - 167 (1997)

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.

Aziz, A.,Lyle, S. J.

, p. 1925 - 1932 (1970)

Surface complexation onto nanosized lanthanum fluoride

Safronikhin,Ehrlich,Shcherba,Lisichkin

, p. 1576 - 1580 (2011)

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

Branched NaYF4 nanocrystals with luminescent properties

Liang, Xin,Wang, Xun,Zhuang, Jing,Peng, Qing,Li, Yadong

, p. 6050 - 6055 (2007)

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.

Fullerene-like rare-earth nanoparticles

Wang, Xun,Li, Yadong

, p. 3497 - 3500 (2003)

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.

Improvement of structural and electrochemical properties of commercial LiCoO2 by coating with LaF3

Yang, Zhanxu,Qiao, Qingdong,Yang, Wensheng

, p. 4791 - 4796 (2011)

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.

Single-crystalline and monodisperse LaF3 triangular nanoplates from a single-source precursor

Zhang, Ya-Wen,Sun, Xiao,Si, Rui,You, Li-Ping,Yan, Chun-Hua

, p. 3260 - 3261 (2005)

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

19F MAS-NMR studies of strontium oxyfluoride aluminosilicate glass

Sroda,Olejniczak

, p. 78 - 82 (2011)

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.

Controlled hydrothermal growth and up-conversion emission of NaLnF 4 (Ln = Y, Dy-Yb)

Zhuang, Jianle,Liang, Lifang,Sung, Herman H. Y.,Yang, Xianfeng,Wu, Mingmei,Williams, Ian D.,Feng, Shouhua,Su, Qiang

, p. 5404 - 5410 (2007)

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.

Dielectric, modulus and impedance analysis of LaF3 nanoparticles

Arun Kumar,Selvasekarapandian,Nithya,Sakunthala,Hema

, p. 3803 - 3807 (2010)

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