Ternary rare-earth bismuthides RE 5SiBi 2 and RE 5GeBi 2 ( RE=La–Nd, Gd–Er): Stabilization of the β-Yb 5Sb 3-type structure through tetrel substitution (original) (raw)
Related papers
X-ray photoelectron spectra and electronic structure of Bi2X3 (X = O, S, Se, Te)
Chemical Physics, 1977
The valence band density of stafes and core ievels have heen measured for Biz&, BiaS3, l&Sea, and BizTea by X-ray photoelectron spectroscopy. The results for Biases and BiaTea are compared with theoretical band structure calculations. The low ionization energy bands are interpreted as arising from p-like bands of bismuth and the Group VI atom. The core levels of bismuth have been found to shift to higher ionization energy with increasing elecfronegativity of the Grouu VI element in the compound. Evidence for two inequivalent selenium atoms in the spectrom of the B&Se3 stru&re has been observed.
Journal of Solid State Chemistry, 2005
The ternary rare-earth metal silicide borides RE 5 Si 2 B 8 (RE ¼ Y, Sm, Gd, Tb, Dy Ho) were prepared by arc melting the elemental components and subsequent annealing up to T ¼ 1850 K. The crystal structure was determined for each term of the series from single-crystal X-ray data: tetragonal symmetry, space group P4/mbm, Z ¼ 2; unit cell parameters a ¼ 7:2616ð3Þ, c ¼ 8:2260ð3Þ ( A and a ¼ 7:1830ð2Þ, c ¼ 7:9900ð3Þ ( A for Sm 5 Si 2 B 8 and Ho 5 Si 2 B 8 , respectively. The structure is a new type and can be structurally described as an intergrowth of ThB 4 -like and U 3 Si 2 -like slabs of composition REB 4 and RE 3 Si 2 , respectively, alternating along the c direction. The boron and silicon substructures are wholly independent and well ordered. The magnetic properties are as follows: Y 5 Si 2 B 8 is a Pauli-type paramagnet above 1.8 K, Gd 5 Si 2 B 8 undergoes a weak (canted) ferromagnetic-like order at 70 K followed by a colinear antiferromagnetic spin alignment at 44 K. Tb 5 Si 2 B 8 and Dy 5 Si 2 B 8 order antiferromagnetically at a Ne´el temperature of T N ¼ 45 and 28 K, respectively. In the paramagnetic regime, the effective moments are in good accord with the theoretical RE 3+ free ion moments. The temperature dependence of the electrical resistivities for the Y, Gd, Tb, and Dy containing samples corroborates with the metallic state of the nonmagnetic (Y) and the magnetically ordered compounds. 11 B, 29 Si and 89 Y nuclear magnetic resonance (NMR) spectroscopy on nonmagnetic Y 5 Si 2 B 8 shows different signals, which correspond to the expected number of distinct crystallographic sites in the structure. 11 B NMR on Y 5 Si 2 B 8 indicates that the local magnetic susceptibilities are substantially different from the ones observed in the related compound YB 4 .
Journal of Solid State Chemistry, 2006
A series of binary rare-earth metal silicides RE 5 Si 3 and ternary boron-interstitial phases RE 5 Si 3 B x (RE ¼ Gd, Dy, Ho, Lu, and Y) adopting the Mn 5 Si 3 -type structure, have been prepared from the elemental components by arc melting. Boron ''stuffed'' phases were subsequently heated at 1750 K within a high-frequency furnace. Crystal structures were determined for both binary and ternary series of compounds from single-crystal X-ray data: hexagonal symmetry, space group P6 3 /mcm, Z ¼ 2. Boron insertion in the host binary silicides results in a very small decrease of the unit cell parameters with respect to those of the binaries. According to X-ray data, partial or nearly full boron occupancy of the interstitial octahedral sites in the range 0.6-1 is found. The magnetic properties of these compounds were characterized by the onset of magnetic ordering below 100 K. Boron insertion induces a modification of the transition temperature and y p values in most of the antiferromagnetic binary silicides, with the exception of the ternary phase Er 5 Si 3 B x which was found to undergo a ferromagnetic transition at 14 K. The electrical resistivities for all binary silicides and ternary boron-interstitial phases resemble the temperature dependence of metals, with characteristic changes of slope in the resistivity curves due to the reduced electron scattering in the magnetically ordered states. Zintl-Klemm concept would predict a limiting composition RE 5 Si 3 B 0.6 for a valence compound and should then preclude the stoichiometric formula RE 5 Si 3 B. Density functional theory calculations carried out on some RE 5 Si 3 Z x systems for different interstitial heteroatoms Z and different x contents from 0 to 1 give some support to this statement. r
Revised structure of Bi 3 TiNbO 9
Acta Crystallographica Section B Structural Science, 1991
The displacive ferroelectric Bi4Ti3Ol2 [Mr = 1171.6, a =5-450(1), b=5.4059(6), c= 32-832 (3) ~, r= 90"00 ° , Z=4, Dx=8"045gcm -3, MoKa, A = 0-7107 ,A,, /z = 747.3 cm-i, F(000) = 1976] is described at room temperature as a commensurate modulation of an Fmmm parent structure derived from an idealized 14/mmm structure. Displacive modes of inherent F2mm, Bmab and Bbab symmetry are all substantial and reduce the space-group symmetry to B2ab. A further substantial displacive mode of Bbam symmetry reduces the space-group symmetry to Blal and induces minor displacive modes of Fmm2, F12/ml and Bream symmetry. A grouptheoretical analysis of the problem details how the X-ray data can be classified so as to monitor the refinement. To a first-order approximation, the F2mm and Bbab symmetry components of atom displacements contribute only to the imaginary part of the structure factors. Because the structure factors have a predominant real component, it is easy to get the F2mm and Bbab displacive components of the O atoms wrong. False minima occur at values of 0.027 for R~ = Y.hllFobs(h)l-IFcalc(h)ll/ZhlFobs(h)l but a corrrect solution was obtained with RI = 0.0177 for 2839 unmerged data with l(h) > 2o-[I(h)]. Criteria for a correct solution are evaluated and subsequently met. The final refinement used a 0.63:0-37 twin model. 0 A-Bi(l) 0(3) Tiff) 0(1) © © © 0 0 0 0 Acta Cryst. Abstract The structure of the incommensurate composite crystal of the monoclinic layered sulfide (PbS)I.12VS2, Mr = 384.20, has been analyzed on the basis of a four-0108-7681/90/040487-06503.00
Electronic structures and chemical bonding of Bi2−xPbxSr3Co2O9 (x=0.0 and 0.5)
Materials Letters, 2002
ABSTRACT The chemical bonding and the electronic structures of C60Fx and C70Fx were investigated by near edge X-ray absorption fine structure (NEXAFS) spectroscopy and UV photoemission spectroscopy (UPS), which are useful methods for examining the unoccupied and the occupied states, respectively. With these results and XPS measurements, we derived the electronic energy diagram of C60Fx and discussed the change of the electronic structure from that of C60 by fluorination. The energies of the LUMO and the Fermi level of solid C60F48 were estimated to be −5.0 and −5.4 eV below the vacuum level, indicating that highly doped C60Fx is a strong electron acceptor. The electronic absorption spectra of C60Fx solutions deep into the vacuum-ultraviolet region were also measured, and the isomerism of C60Fx was discussed by comparing the observed results with theoretical simulations.
Properties of Bi2Se3 Single Crystals Doped with Pb Atoms
Physica Status Solidi (a), 1993
crystallizes in the series of anisotropic V2VI, semiconductors in a layer structure with distinct cleavage planes perpendicular to the trigonal c-axis (point group 3m-D,,) and the compound is a component of material applied in thermoelectric devices as solid state coolers or generators [l]. Therefore, studies of the effect of impurities on the physical properties of Bi,Se, are interesting both for basic and applied research.
arXiv: Materials Science, 2020
Na$_{0.5}$(Bi$_3$/4RE$_{1/4}$)$_{0.5}$TiO$_3$ (RENBT, RE = Nd, Gd, Dy, and Ho) compounds were investigated in the framework of first-principles calculations using the full potential linearized augmented plane wave (FP-LAPW) method based on the spin-polarized density functional theory implemented in the WIEN2k code. Combined charge density distribution and Ti K-edge x-ray absorption spectra revealed that the RENBT compositions with high polarization values were accompanied by a higher TiO$_6$ distortion, DyNBT, and NdNBT compounds. The effect of the rare-earth elements on the polarization were confirmed experimentally with the collection of the hysteresis loops. The investigation of the electronic properties of the compounds highlighted the emergence of a magnetization owing to the 4f orbital effect of the rare-earth elements. Besides, the investigation of the chemical ordering showed a short-range chemical ordering for the pure composition and an increased A-site disorder for dyspro...
Electronic structure of YbTX compounds
Journal of Alloys and Compounds, 2003
The electronic structure of ternary YbTX compounds (T5Au, Pd, Rh, Pt; X5Sn, Bi) was studied by X-ray photoemission spectroscopy (XPS). XPS valence bands were compared with calculations using the tight-binding linear muffin-tin orbital method. The results showed that the valence bands in these compounds were formed mainly by the 4f orbitals of ytterbium and the 4d (5d) orbitals of the transition elements. Analysis of the Yb 4f valence band and Yb 4d core level states clearly indicated the presence of divalent Yb ions in YbAuSn and YbAuBi, and trivalent ions in YbRhSn and YbPtSn. In turn, the Yb ions in YbPdBi exhibited a mixed valence character.
Journal of Alloys and Compounds, 2006
The solid state phase equilibria in the ternary RE-Si-B diagrams (RE = Dy, Ho, Er and Y) were determined at 1270 K using experimental techniques such as X-ray diffraction, scanning electron microscopy and electron probe microanalysis. In general, three ternary phases were obtained for each diagram: the line compound RE 5 Si 2 B 8 with tetragonal symmetry, the boron-inserted Nowotny phase RE 5 Si 3 B x of Mn 5 Si 3 -type and the solid solution REB 2−x Si x of AlB 2 -type. Prior to this work, the binary systems RE-Si and RE-B, which form the boundary of each diagram, were also re-investigated. In addition to the structures of RE -type) which were previously reported or will be presented in a forthcoming paper, the X-ray single crystal structures of RE 5 Si 4 (Sm 5 Ge 4 -type, RE = Dy and Ho), DySi (CrB-type) and HoSi in both polymorphic modifications, i.e. the FeB-(high temperature) and CrB-(low temperature) types, were determined and are described herein. Structural relationships between members of the same series on one side, and between both forms of HoSi on the other side, are also discussed in terms of coordination polyhedra and interatomic distances. Finally, magnetic measurements were performed on the alloys REB 2−x Si x , which in case of RE = Dy exhibit a marked increase of the magneto-crystalline anisotropy, whereas for RE = Ho a change from ferromagnetic to antiferromagnetic behaviour with increasing silicon content is encountered. (J.-F. Halet). the boron-inserted Nowotny phase Nd 5 Si 3 B x of Mn 5 Si 3 -type. With RE = Gd instead, the line compound Gd 5 Si 2 B 8 of a new structure type was discovered in addition to the Nowotny phase Gd 5 Si 3 B 0.64 . This result encouraged us to pursue the investigations on the RE-Si-B systems when RE is a heavy rareearth metal. Our research was focused on the solid phase equilibria in the RE-Si-B system (RE = Dy, Ho, Er and Y) at 1270 K. Prior to this work, the binary systems RE-Si and RE-B, which form the boundary of each diagram, were re-investigated. Generally, all the binary phases reported in literature were confirmed , as well as the more recently detected binary compounds RE 3 Si 4 of the Ho 3 Si 4 -type [7], formed via a sluggish peritectoidal reaction between RESi and RESi 2−x . Moreover, the holmium silicide HoSi was encountered in both polymorphic modifications, i.e. the FeB-and CrB-type structures. 0925-8388/$ -see front matter