[en] The occurrence of twinning can often be related to higher symmetrical structures. Fluorides are frequently twinned due to their close relation to high symmetry structures like fluoride, tysonite or pyrochlores. The series of compounds CsLn_2F_7 is no exception. We refined the structures of the twinned compounds with Ln=Nd, Gd, Tb, Er, Yb in space group P112_1/b. An analysis of the pseudosymmetry of the resulting structures shows a highly symmetrical cation partial structure with a cation distribution similar to the one in the hexagonal Laves phase MgZn_2. Several other compounds ALn_2F_7, which have been described in the literature, show a similar cation array. The diversity of different space groups which have been reported for ALn_2F_7 compounds can be better understood using group-subgroup relationships assuming the hypothetical structure of the cation array with space group P6_3/mmc as aristotype. Furthermore, the twinning is easily understood on the basis of the lost symmetry operations in the symmetry reduction from point group 6/mmm, e.g. to 2/m in the case of the CsLn_2F_7 compounds.

No abstract available

[en] The diffuse reflectance and photoluminescence (PL) spectra of NdI₂, SmI₂, EuI₂, DyI₂, TmI₂ and YbI₂ were measured between 225 and 12 500 nm in order to determine their 4fⁿ → 4f^n-15d¹ optical bandgaps. The results were compared with those obtained using an empirical model of the electronic structure of LnI₂. The results can be used to explain the lanthanide valency and crystalline structure changes of other lanthanide diiodides such as PrI₂. (paper)

[en] From reactions of equimolar quantities of the heavier lanthanoids (M = Gd - Lu) with the elements sulfur and iodine in fused silica ampoules (900 C, 10 d) phase-pure samples of the lanthanoid sulfide iodides MSI (M = Gd - Lu) could be prepared. Besides the already structurally determined sulfide iodides MSI with M = Gd and Dy, all samples could be characterized by means of X-ray powder diffraction and their magnetic behavior was examined. In addition a single-crystal structure refinement for HoSI was carried out (orthorhombic, Pmmn; a = 415.09(4) pm, b = 531.34(5) pm, c = 920.53(9) pm), which confirmed the isotypy of the later lanthanoid sulfide iodides with the structure of FeOCl. On the basis of the X-ray powder diffraction experiments all prepared compounds could be indexed in a primitive orthorhombic unit cell. An analysis of the determined lattice parameters and cell volumes resulted in the typical lanthanoid contraction for compounds within the row of the 4f elements. The magnetochemical studies led to the expected effective magnetic moments for trivalent lanthanoid cations without showing any magnetic ordering phenomenon. (Copyright copyright 2013 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

No abstract available

[en] An easy to use and rapid procedure of ionometric determination of Zn and Cd in some alloys is presented. The method is based on the different capacity of complex formation of metal cations. Ion-selective electrodes with tetradecylammonium chloride and iodide were used as indicator electrodes. To separate Zn and Cd and to increase the selectivity of determination a sorption column with strong acid cationite KU-2 is used. Zinc and cadmium determination in alloys was conducted with the help of the restricting solutions method. It was achieved by a successive measuring of the ion-selective electrode potential in a standard solution with a lower zinc (cadmium) concentration, then in eluate and in a standard solution with a higher zinc (cadmium) concentration. The procedure thus proposed provides 4 -6 determination per hour

No abstract available

[en] We report a method for preparing uranium trichloride, UCl₃, by reacting ZnCl₂ with U in a molten LiCl-KCl eutectic salt at 500 °C. Cyclic voltammetry indicated the formation of UCl₃ as the reaction proceeded. After 30 h, the reaction was terminated and the final product was confirmed to contain 13.2 wt% UCl₃-LiCl-KCl salt by the ICP-OES method. (author)

No abstract available

[en] A fundamental study on the electrolysis of actinide and lanthanide fluorides in the LiF-NaF-KF (46.5-11.5-42.0 mol%; FLINAK) eutectic salt medium at 773K was performed by means of cyclic voltammetry as well as potentiostatic electrodeposition of metals. The positions of peak potential with the change of scanning rate in the cyclic voltammogram were examined, which enables us to identify the reversibility of electrochemical reduction and oxidation of the concerned ion at the electrode. It was considered that the reduction peaks at -0.8 V and -1.3 V (vs. the Ni-Q.R.E.) corresponded to the electrodeposition of actinide ions in the FLINAK melt. The peak at -2.05 V seems to be attributable to the multiple reductions of actinide and lanthanide ions in the melt. The deposits formed by the potentiostatic electrolysis of the FLINAK mixture with metal fluorides showed that the neptunium ion was selectively reduced up to the potential -1.2 V, whereas the mixture of actinides was deposited at a lower potential than -1.4 V. The analysis results by ICP (Inductively Coupled Plasma) and standard gamma spectroscopy of the samples revealed that salt adhesion and the relative amount of lanthanides in the cathode deposits were higher than that estimated in the range of -0.8 - -2.0 V, indicating that lanthanides are always accompanied by the reduction of actinides in the FLINAK melt in spite of their higher values of Gibbs free energy of formation than those of actinide fluorides. (author)