Caesium Pentafluoroterbate, CsTbF 5

International audienc

Enhancement of cationic conductivity in some heptafluorozirconates due to a paddle-wheel mechanism

International audienc

Étude cristallographique, infra-rouge et Raman de nouveaux fluorophosphates de terres rares de structure zircon

Une série de solutions solides de formule générale LixLnxY1-x (PO4)1-xF4x où Ln = Gd → Lu, Y et 0 ≤ x ≤ 0,45 et de structure zircon a été mise en évidence lors de l’étude des systèmes LiLnF4 - YPO4. Leurs caractéristiques cristallochimiques ont été déterminées par diffraction X sur des échantillons pulvérulents. Une étude infra-rouge et Raman a été effectuée sur quelques représentants correspondant à la composition x = 0,40

Recent progress in tetravalent terbium chemistry

International audienc

Spectroscopic studies of the Eu3+ and Er3+ ions in the fluorozirconate LaZr2F11 matrix

An investigation by optical spectroscopy of the Eu3 + and Er3 + active ions in the crystallized fluorozirconate matrix LaZr2F11 is presented. The D-5(1) --> F-7(0-5) emission lines of Eu3 + are used to extract the F-7(0-5) energy scheme and the observed extinctions permit the deduction of irreducible representations (IRREPS) associated with corresponding sub-levels in the D-2 symmetry. The crystal field analysis was carried out on a 387 x 387 basis set, comprising the F-7, D-5(1,2,3) F-5(1,2), (5)G(1,2,3) and P-3(1,2,3,4,5,6) terms of the Eu-3 (+) 4f(6) configuration. The deviation and rms are 6.8 and 7.9 cm (-1), respectively for 38 levels and ten parameters. The experimental crystal field parameters are in good agreement with the ab-initio ones. Moreover, the relative intensities of the D-5(0) --> F-7(2,3,4) emissions are well reproduced by an 'ab-initio' calculation, except for three lines. The Er3 + ions introduced in LaZr2F11, microcrystals also lie in an unique crystallographic site. A total of 31 energy levels were recorded and the crystal field analysis led to 6.6 and 7.8 cm (-1) for the deviation and rms, respectively, for nine variable parameters taken into account. The experimental CF parameters for Er3 + and Eu3 + are very similar, which seems to show that the host lattice contracts around the smaller Er3 + ion. The informations given by both Eu3 + and Eu3 + optical probes in LaZr2F11 are very consistent with the structure previously determined for the isotypic PrZr2F11 fluoride. (C) 2000 Elsevier B.V. B.V. All rights reserved

(Adipato-2O,O')diaqua[bis(pyridin-2-yl-N)amine]cobalt(II) trihydrate

In the monomeric title complex, [Co(C6H8O4)(C10H9N3)(H2O)2]·3H2O, the distorted octahedral CoN2O4 coordination environment comprises two N-atom donors from the bidentate dipyridyldiamine ligand, two O-atom donors from one of the carboxylate groups of the bidentate chelating adipate ligand and two water molecules. In addition, there are three solvent water molecules which are involved in both intra- and inter-unit O-HO hydrogen-bonding interactions, which together with an amine-water N-HO hydrogen bond produce a three-dimensional framework

Magnetic properties of a mixed-valence (III/IV) terbium fluoride KTb3F12

The mixed-valence terbium (III/IV) fluoride KTb3F12 crystallizes with the tetragonal symmetry, space group I4/m. Below T-N=3.6+/-0.1 K this compound exhibits an antiferromagnetic collinear structure with k=0 characterized by ferromagnetic chains of edge-sharing Tb4+ polyhedra and an antiferromagnetic order between the nearest chains. The magnetic moments of the Tb4+ ions deduced from neutron diffraction are equal to 6.95(4) mu(B) at 1.4 K and aligned along the c axis. The Tb3+ ions lie in a special position with zero magnetic moments due to a symmetry cancellation effect of the internal molecular field. In other words, Tb3+ ions present a zero time-averaged magnetic moments in the ordered state, whereas T-N corresponds to the long-range antiferromagnetic ordering of the moments of the Tb4+ ions. From the thermal variation of the reciprocal magnetic susceptibility a molar Curie constant of 27.97(1) emu K mol-1 has been obtained, in good agreement with the theoretical value of 27.64 expected for two Tb4+ and one Tb3+ free ions. The Tb4+ contribution to the magnetization is approximated by the Langevin function and then the Tb3+ contribution is obtained by subtracting the calculated Tb4+ contribution to the total magnetization. (C) 2002 American Institute of Physics