- Preparation and examination of the properties of complex scandium fluorides
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Precipitation of scandium with sodium fluoride from an ammonium hydrogen difluoride solution was examined at the molar ratios of Na to Sc within 1-14 and different initial concentrations of scandium in solution. The composition of the resulting precipitate was determined by X-ray phase analysis method. The solubility of the scandium compounds synthesized was examined. Pleiades Publishing, Ltd., 2011.
- Sokolova, Yu. V.,Cherepanin
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- On the phase diagram of the binary system Sc2O3-ScF3 in the temperature range 1400-1840 K
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The phase diagram of the binary system Sc2O3-ScF3 was investigated in the temperature range 1400-1840 K by quantitative differential thermal analysis (DTA). X-ray powder diffraction analysis revealed that at room temperature only the well-known compounds Sc2O3, ScOF and ScF3 exist. At 1419 ± 3 K, the slightly non-stoichiometric compound of composition Sc(O,F)1.88±δ is probably formed by eutectoid reaction from Sc2O3 and ScOF. ScOF decomposes into Sc(O,F)1.88±δ(s) and ScF3(s) at 1460±3 K. Eutectic melting occurs at 1627 ± 3 K for a mixture of 67 mol% ScF3 and 33 mol% ScO1.5. Pure ScF3 melts at 1822±3 K and does not display any solid state phase transition. The compound Sc(O,F)1.88±δ could not be quenched to room temperature, and therefore structural details of this presumably fluorite-related phase could not be investigated.
- Petzel,Schneider,Hormann
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- Ammonium scandium tetrafluoride
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The title compound, NH4ScF4, is an addition to the AMF4 family of layered perovskite-like structures. The structure consists of a two-dimensional array of corner-sharing ScF6 octahedra, which produces anionic sheets of stoichiometry [ScF4]- stacked along the c axis. The layers are separated by charge-balancing ammonium cations, which hydrogen bond to the apical F atoms of adjacent layers. This structure may be viewed as a 'single-layer' fluoride analogue of the Dion-Jacobson family of oxides.
- Stephens, Nicholas F.,Lightfoot, Philip
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- Syntheses and structures of Li3ScF6 and high pressure LiScF4-, luminescence properties of LiScF4, a new phase in the system LiF-ScF3
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Colorless single crystals of Li3ScF6 have been prepared by reacting the binary components LiF and ScF3 at 820°C for 16 h in argon atmosphere. This complex fluoride is the only stable phase in the system LiF-ScF3 under ambient pressure. According to a structure refinement based on single crystal X-ray diffraction data it crystallizes in the centrosymmetric space group P3c1 with a=8.78.3(1)A and c=9.518(1)A. The new structure of Li3ScF6 is a filled variant of the Na2GeF6 type structure and can be described in terms of a hexagonal close packing of fluorine in which 2/3 of the octahedral holes are occupied by Sc and Li. High pressure/high temperature studies of the system LiF-ScF3 show that the new phase LiScF 4 is formed at around 5.5 GPa and 575°C. According to Rietveld refinements of powder X-ray diffraction data LiScF4 adopts the Scheelite type structure (space group I41/a) with a=4.980(1)A and c=10.074(1)A. A sample of LiScF4 doped with 1% Er exhibits an intense luminescence in the far IR region.
- Tyagi,Koehler,Balog,Weber
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- Action of Ammonium Fluoride on Scandium: Synthesis and Crystal Structures of (NH4)3[ScF6] and [Cu(NH3)4]3[ScF6]2
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The action of (NH4)F on scandium in copper ampoules yields either (NH4)3[ScF6] or ScF3 and a small quantity of [Cu(NH3)4]3[ScF6]2, respectively,depending upon the molar ratio of the educts (NH4)F:Sc (6:1 and 4:1, re spectively) and temperature. (NH4)3[ScF6] crystallizes with the cryolitetype of structure: monoclinic, P21/n, Z=2; a=650.0(2); b=651.4(2); c=94 9.0(2) pm; β=90.40(2)°, [Cu(NH3)4]3[ScF6]2 is triclinic, P-1, Z=1; a=821.1(2); b=821.2(2); c=822.7(2) pm; α=90.04(3); β=90.00(3); γ=90.16(3)°. In its chemical behaviour against (NH4)F, scandium parallels aluminium rather than gallium.
- Boehmer, Norbert,Meyer, Gerd
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- Solubility of Scandium Trifluoride and Ammonium Hexafluoroscandate in Water and Hydrofluoric Acid
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The solubilities of ScF3 and (NH4)3ScF6 in water and in hydrofluoric acid are investigated by chelatometric titration at HF concentrations up to 24 mol/dm**3 and in the 20-80°C temperature range. The solubility of ScF3 in water (g/dm**3) is described by the equation c=-0.24+0.157T. With an increase in the HF molarity, the solubilities of both ScF3 and (NH4)3ScF6 increase over 0-5 mol/dm**3 range and slowly decrease over the .apprx.15-24 mol/dm**3 range. In the concentrated hydrofluoric acid,the ammonium salt converts into ScF3.
- Potapenko, S. V.,Rakov, E. G.,Khaustov, S. V.
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p. 1073 - 1076
(2008/10/08)
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