T:Toxic;7789-24-4Relevant articles and documents
Electron microscopy and krypton adsorption characterization of high purity LiF powders
Dericbourg J.
, p. 1157 - 1160 (1992)
In the present work, a comparative study of LiF powders has been undertaken. Methods for the preparation of well-defined, high-purity LiF powders are reported. Sample characterization is carried out by combining transmission electron microscopy (TEM) with krypton gas adsorption isotherms. LiF crystallites obtained via precipitation in aqueous solutions are perfect regular cubes surrounded by {100} faces. However, fine particles produced by evaporation of LiF powders in an inert gas grow to more complicated polyhedra, surrounded by a predominant plane, which has been identified as a {111} plane.
Stability of Li2CO3 in cathode of lithium ion battery and its influence on electrochemical performance
Bi, Yujing,Wang, Tao,Liu, Meng,Du, Rui,Yang, Wenchao,Liu, Zixuan,Peng, Zhe,Liu, Yang,Wang, Deyu,Sun, Xueliang
, p. 19233 - 19237 (2016)
Lithium carbonate is an unavoidable impurity at the cathode side. It can react with LiPF6-based electrolyte and LiPF6 powder to produce LiF and CO2, although it presents excellent electrochemical inertness. Samples of Li2CO3-coated and LiF-coated LiNi0.8Co0.1Mn0.1O2 were prepared to compare their influence on a cathode's behavior. After 200 cycles at 1C, in contrast to 37.1% of capacity retention for the Li2CO3-coated material, the LiF-coated LiNi0.8Co0.1Mn0.1O2 retained 91.9% of its initial capacity, which is similar to the fresh sample. This demonstrates that decomposition of Li2CO3 can seriously deteriorate cyclic stability if this occurs during working.
Orange-Emitting Li4Sr4[Si4O4N6]O:Eu2+ - A Layered Lithium Oxonitridosilicate Oxide
Niklaus, Robin,Neudert, Lukas,Stahl, Juliane,Schmidt, Peter J.,Schnick, Wolfgang
, p. 14304 - 14313 (2018)
We report on the structure and properties of the lithium oxonitridosilicate oxide Li4Sr4[Si4O4N6]O:Eu2+ obtained from solid-state metathesis. The crystal structure was solved and refined from single-crystal X-ray data in the space group P42/nmc (No. 137) [Z = 2, a = 7.4833(6), c = 9.8365(9) ?, and R1(obs) = 0.0477]. The structure of Li4Sr4[Si4O4N6]O:Eu2+ is built up from a layered 2D network of SiN3O tetrahedra and exhibits stacking disorder. The results are supported by transmission electron microscopy and energy-dispersive X-ray spectroscopy as well as lattice energy, charge distribution, and density functional theory (DFT) calculations. Optical measurements suggest an indirect band gap of about 3.6 eV, while DFT calculations on a model free of stacking faults yield a theoretical electronic band gap of 4.4 eV. Samples doped with Eu2+ exhibit luminescence in the orange spectral range (λem 625 nm; full width at half-maximum 4164 cm-1 internal quantum efficiency at room temperature = 24%), extending the broad field of phosphor materials research toward the sparsely investigated materials class of lithium oxonitridosilicate oxides.
Crystal Structure and Nontypical Deep-Red Luminescence of Ca3Mg[Li2Si2N6]:Eu2+
Poesl, Christine,Schnick, Wolfgang
, p. 3778 - 3784 (2017)
Rare-earth-doped nitridosilicates exhibit outstanding luminescence properties and have been intensively studied for solid-state lighting. Here, we describe the new nitridolithosilicate Ca3Mg[Li2Si2N6]:Eu2+ with extraordinary luminescence characteristics. The compound was synthesized by the solid-state metathesis reaction in sealed Ta ampules. The crystal structure was solved and refined on the basis of single-crystal X-ray diffraction data. Ca3Mg[Li2Si2N6]:Eu2+ crystallizes in the monoclinic space group C2/m (no. 12) [Z = 4, a = 5.966(1), b = 9.806(2), c = 11.721(2) ?, β = 99.67(3)°, V = 675.9(2) ?3] and exhibits a layered anionic network made up of edge- and corner-sharing LiN4 tetrahedra and [Si2N6]10- bow-tie units. The network charge is compensated by Ca2+ and Mg2+ ions. Upon irradiation with UV to blue light, red emission at exceptionally long wavelengths (λem = 734 nm, fwhm ≈2293 cm-1) is observed. According to emission in the near-infrared, application in LEDs for horticultural lighting appears promising.
YHO, an Air-Stable Ionic Hydride
Zapp, Nicolas,Auer, Henry,Kohlmann, Holger
, p. 14635 - 14641 (2019)
Metal hydride oxides are an emerging field in solid-state research. While some lanthanide hydride oxides (LnHO) were known, YHO has only been found in thin films so far. Yttrium hydride oxide, YHO, can be synthesized as bulk samples by a reaction of Y2O3 with hydrides (YH3, CaH2), by a reaction of YH3 with CaO, or by a metathesis of YOF with LiH or NaH. X-ray and neutron powder diffraction reveal an anti-LiMgN type structure for YHO (Pnma, a = 7.5367(3) ?, b = 3.7578(2) ?, and c = 5.3249(3) ?) and YDO (Pnma, a = 7.5309(3) ?, b = 3.75349(13) ?, and c = 5.3192(2) ?); in other words, a distorted fluorite type with ordered hydride and oxide anions was observed. Bond lengths (average 2.267 ? (Y-O), 2.352 ? (Y-H), 2.363 ? (Y-D), >2.4 ? (H-H and D-D), >2.6 ? (H-O and D-O), and >2.8 ? (O-O)) and quantum-mechanical calculations on density functional theory level (band gap 2.8 eV) suggest yttrium hydride oxide to be a semiconductor and to have considerable ionic bonding character. Nonetheless, YHO exhibits a surprising stability in air. An in situ X-ray diffraction experiment shows that decomposition of YHO to Y2O3 starts at only above 500 K and is still not complete after 14 h of heating to a final temperature of 1000 K. YHO hydrolyzes in water very slowly. The inertness of YHO in air is very beneficial for its potential use as a functional material.
Study of the reaction dynamics of Li + HF, HCl by the crossed molecular beams method
Becker, Christopher H.,Casavecchia, Piergiorgio,Tiedemann, Peter W.,Valentini, James J.,Lee, Yuan T.
, p. 2833 - 2850 (1980)
The reactions of (I) Li + HF --> LiF + H and (II) Li + HCl --> LiCl + H have been studied by the crossed molecular beams method.Anguylar distributions of product molecules have been measured at 4 collision energies (Ec) ranging from about 2 to 9 kcal/mole and time-of-flight (TOF) measurements of product velocity distributions were made at approximately Ec = 3 and 9 kcal/mole for both reactions (I) and (II).The combined N(Θ) and TOF results were used to generate contour maps of lithium-halide product flux in angle and recoil velocity in the center-of-mass (c.m.) frame.For reaction (I) at Ec = 3 kcal/mole the c.m. angular distribution shows evidence of complex formation with near forward-backward symmetry; slightly favored backward peaking is observed.The shape of this T(θ) indicates there is significant parallel or antiparallel spatial orientation of initial and final orbital angular momentum L and L', even though with H departing L' must be rather small and L ca.J', where J' is the final rotational angular momentum vector.It is deduced that coplanar reaction geometries are strongly favored.At Ec = 8.7 kcal/mole the T(θ) of reaction (I) becomes strongly forward peaked.The product translational energy distributions P(ET') at both these collision energies give an average ET' of ca. 55percent of the total available energy; this appears consistent with a theoretically calculated late exit barrier to reaction.The T(θ) at Ec = 2.9 and 9.2 kcal/mole for reaction (II) are forward-sideways peaked.Most of the available energy (ca. 70percent) goes into recoil velocity at both Ec for LiCl formation.This suggests a late energy release for this 11 kcal/mole exoergic reaction.Both reactions (I) and (II) show evidence of on more than a minor partitioning of energy into product vibrational excitation.Integral reactive cross sections (?R) are evaluated by integrating the product distributions in the c.m. frame and using small angle nonreactive scattering of Li as an absolute calibrant.Values of ?R are: for LiF formation ?R ca. 0.8 Angstroem2 and 0.94 Angstroem2 at Ec = 3 and 8.7 kcal/mole, while for LiCl formation ?R = 27 Angstroem2 and 42 Angstroem2 at Ec = 2.8 and 9.2 kcal/mole, with estimated absolute and relative uncertainties of a factor of 2, and 30percent, respectively.Average opacities for reaction have been estimated from the reaction cross sections and the extent of rotational excitation of products to be about 0.1 for reaction (I) and 1 for reaction (II), for L values allowed to react.These results are discussed in some detail with regard to the kinematic constraints, reaction dynamics, and potential energy surfaces for these two reactions, and related experimental and theoretical works are noted.In addition, angular distributions of nonreactive scattering of Li off HF and HCl are measured at 4 different Ec each. ...
Li2B3O4F3, a new lithium-rich fluorooxoborate
Pilz, Thomas,Nuss, Hanne,Jansen, Martin
, p. 104 - 108 (2012)
The new lithium fluorooxoborate, Li2B3O 4F3, is obtained by a solid state reaction from LiBO 2 and LiBF4 at 553 K and crystallizes in the acentric orthorhombic space group P212121 (no. 19) with the cell parameters a=4.8915(9), b=8.734(2), and c=12.301(2) A. Chains of fluorinated boroxine rings along the b axis consists of BO3 triangles and BO2F2 as well as BO3F tetrahedra. Mobile lithium ions are compensating the negative charge of the anionic chain, in which the fourfold coordinated boron atoms bear a negative formal charge. Annealing Li2B3O4F3 at temperatures above 573 K leads to conversion into Li2B6O9F 2. The title compound is an ionic conductor with the highest ion conductivity among the hitherto know lithium fluorooxoborates, with conductivities of 1.6×10-9 and 1.8×10-8 S cm-1 at 473 and 523 K, respectively.
PREPARATION OF HIGHLY PURE LITHIUM AND SODIUM FLUORIDES USING SOLVENT EXTRACTION.
Kobayashi
, p. 2965 - 2966 (1988)
LiF and NaF can be purified by solvent extraction. The impurity concentrations in the purified NaF are 2. 5 ng g** minus **1 for chromium, 60 ng g** minus **1 for iron, 0. 03 ng g** minus **1 for cobalt, and 1. 5 ng g** minus **1 for copper. The concentra
Pyrolytic synthesis and Eu3+→Eu2+ reduction process of blue-emitting perovskite-type BaLiF3:Eu thin films
Fujihara, Shinobu,Kishiki, Yoko,Kimura, Toshio
, p. 1032 - 1036 (2004)
Perovskite-type barium lithium fluoride (BaLiF3) was synthesized by pyrolysis of metal trifluoroacetates. The reaction temperature necessary for producing a single-phase material was found to be 600°C, which was lower than that for a conventional solid-state reaction or a melting method. Eu-doped BaLiF3 was also prepared and characterized to examine the suitability of trifluoroacetates for precursors in synthesizing homogeneous complex metal fluoride materials. It was demonstrated that trivalent Eu3+, which was used as acetate for a starting material, was reduced to divalent Eu2+ in the pyrolysis process of BaLiF 3, as indicated by a broad blue emission due to an allowed 4f 65d→4f7 transition at 408nm with a ultraviolet excitation at 254nm. The concentration quenching of the blue emission occurred at 5at% of Eu in BaLiF3, indicating that Eu was homogeneously dispersed in the BaLiF3 host lattice. Mechanisms of the formation and reduction process of BaLiF3 were discussed based on pertinent chemical reactions.
Flux crystal growth, structure, magnetic and optical properties of a family of alkali uranium(IV) phosphates
Usman, Mohammad,Morrison, Gregory,Klepov, Vladislav V.,Smith, Mark D.,zur Loye, Hans-Conrad
, p. 19 - 26 (2019)
A family of alkali uranium(IV) phosphates, AU2(PO4)3 (A = Li – Cs), was synthesized as single crystals by the reaction of US2 and (NH4)2HPO4 in the respective ACl (A = Li – Cs) flux contained in a sealed fused-silica tube at 850 °C, and as phase pure powders from a similar reaction using UF4 as the uranium source. AU2(PO4)3 (A = Li – Rb) crystallize in the NaTh2(PO4)3 (NTP) structure type with monoclinic space group C2/c and consist of a 3D structure that features a framework composed of edge- and corner-sharing polyhedra. The cesium analogue, CsU2(PO4)3, crystallizes in a different structure with space group P21/n that is related to the NaZr2(PO4)3 (NZP) structure type and consists of a framework composed of corner-sharing polyhedra. Two new alkali uranium phosphates, Li2U(PO4)2 and Cs4U4(P2O7)5, were also grown as single crystals at 700 °C. Li2U(PO4)2 was isolated in approximately 30% yield based on uranium. Li2U(PO4)2 crystallizes in space group P21/c exhibiting a layered structure while Cs4U4(P2O7)5, crystallizes in space group P21/n in a new structure type featuring a 3D framework. The magnetic susceptibilities and the field dependent magnetizations were measured for AU2(PO4)3 (A = Li, Na, K and Cs); all compounds exhibited negative Weiss temperatures with no obvious antiferromagnetic transition. Optical properties were measured by UV–vis and IR spectroscopy.
