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[en] The synthesis and crystal structure of a series of rare earth metal hydride tellurides with the composition REHTe (RE = Y, La–Nd, Gd–Er) is reported. These compounds have been obtained by the reaction of rare earth metal dihydrides (REH) with elemental tellurium in sealed tantalum capsules at T = 700°C using cesium chloride (CsCl) as fluxing agent, which can be washed away with water due to the astonishing insensitivity of these hydride tellurides (REHTe) against hydrolysis. All of the compounds crystallize in the hexagonal space group Pm2 with a filled WC-type crystal structure, exhibiting a mutual trigonal-prismatic coordination of the heavy ions (RE and Te), while the hydride anions reside in the trigonal prismatic voids surrounded by three rare earth metal cations expanding their coordination pattern to a tricapped trigonal prism. This 1H-type crystal structure is compared with the 1H- and 2H-type structures of the respective hydride selenides (REHSe, RE = Y, La–Nd, Gd–Tm, Lu). Both hexagonal basic crystal structures can be derived from the AlB-type structure as demonstrated in a Bärnighausen tree by group-subgroup relationships.
[en] Five rare-earth copper tellurides have been synthesized by the reactions of the elements at 1073 K. The isostructural compounds LaCu0.40Te2 (a = 7.7063(13) angstrom, b = 8.5882(14) angstrom, c = 6.3115(10) angstrom, T = 153 K), NdCu0.37Te2 (a = 7.6349(7) angstrom, b = 8.3980(8) angstrom, c = 6.18388(6) angstrom, T = 153 K), SmCu0.34Te2 (a = 7.6003(10) angstrom, b = 8.3085(11) angstrom, c = 6.1412(8) angstrom, T = 153 K), GdCu0.33Te2(a = 7.5670(15) angstrom, b = 8.2110(16) angstrom, c = 6.0893(12) angstrom, T = 107 K, and DyCu0.32Te2 (a = 7.5278*13) angstrom, b = 8.1269(14) angstrom, c = 6.0546(11) angstrom, T = 107 K) crystallize with four formula units in space group D2h11-Pbcm of the orthorhombic system. In each, the rare-earth (Ln) atom is coordinated by a bicapped trigonal prism of Te atoms and the Cu atom is coordinated by a tetrahedron of Te atoms. Infinite linear Te(l+x)- chains run parallel to c, with Te-Te distances decreasing from 3.1558(5) angstrom in LaCu0.40Te2 to 3.0273(3) angstrom in DyCu0.32Te2. Both the thermopower and conductivity data in the c direction show LaCu0.40Te2 to be a semiconductor at all temperatures, and NdCu0.37Te2, SmCu0.34Te2, and GdCu0.33Te2 to be semiconductors above 150--200 K. The thermopower data for these three compounds exhibit very high peaks of approximately 900 μV/K in the vicinity of 150 K, followed by a rapid decrease at lower temperatures. This behavior deviates from the trend expected for semiconductors. Huckel calculations predict that the Te(l+x)- chains in LnCuxTe2 should show metallic properties. Possible reasons for this discrepancy between theory and experiment involve distortions of the Te chains or disorder of the Cu atoms. GdCu0.33Te2 is paramagnetic with μeff = 7.74(3) μΒ, typical for Gd3+
[en] Problem of structural heterogeneity in semiconductor melts in the vicinity of melting point is considered. Results of experimental studied of viscosity and density of semiconductor melts, melting by semiconductor-metal type are analyzed. The conclusion about structural heterogeneity of semiconductor melts, metallizing during melting is made. Studies on properties of gallium, indium and mercury telluride melts, as well as alloys of quasibinary HgTe-CdTe systems are analyzed. 79 refs.; 14 figs
[en] The new compounds CsUTe6, CsTiUTe5, Cs8Hf5UTe30.6, and CsCuUTe3 have been synthesized through the reaction of the metals with a Cs2Ten flux. CsUTe6 crytallizes in space group D2h16-Pnma of the orthorhombic system with eight formula units in a cell of dimensions a = 30.801(7), b = 8.143(2), and c = 9.174(2) Angstrom and V = 2301(1) Angstrom 3 (T=113K). CsTiUTe5 crystallizes in space group D2h5-Pmma of the orthorhombic system with two formula units in a cell of dimensions a = 6.130(1), b = 8.240(2), and c = 10.363(2) Angstrom and V = 523.4(2) Angstrom 3 (T = 113K). Cs8Hf5UTe30.6 crystallizes in space group C2h5-P2√c of the monoclinic system with four formula units in a cell of dimensions a = 12.043(3), b = 18.724(4), and c = 30.496(6) Angstrom, β = 97.64(3)degrees, and V = 6816(2) Angstrom 3 (T = 113 K). CsCuUTe3 crystallines in space group D2h17-Cmcm of the orthorhombic system with four formula units in a cell of dimensions a = 4.327(1), b = 16.661(4), and c = 11.337(3) Angstrom, and V = 817.3(3) Angstrom 3 (T = 113K)
[en] Phase diagram of Dy2Te3-PbTe system and properties of compounds in the system were investigated (X-ray diffraction patterus, microhardness, density). Semiconductor character of solid solutions of rare earth tellurides in lead monotelluride was supported. 4 figs
[en] Five new quaternary chalcogenides of the 1113 family, namely BaAgTbS_3, BaCuGdTe_3, BaCuTbTe_3, BaAgTbTe_3, and CsAgUTe_3, were synthesized by the reactions of the elements at 1173-1273 K. For CsAgUTe_3 CsCl flux was used. Their crystal structures were determined by single-crystal X-ray diffraction studies. The sulfide BaAgTbS_3 crystallizes in the BaAgErS_3 structure type in the monoclinic space group C"3,_2_h-C2/m, whereas the tellurides BaCuGdTe_3, BaCuTbTe_3, BaAgTbTe_3, and CsAgUTe_3 crystallize in the KCuZrS_3 structure type in the orthorhombic space group D"1,_2"7,_h-Cmcm. The BaAgTbS_3 structure consists of edge-sharing [TbS_6"9"-] octahedra and [AgS_5"9"-] trigonal pyramids. The connectivity of these polyhedra creates channels that are occupied by Ba atoms. The telluride structure features "2_∞[MLnTe_3"2"-] layers for BaCuGdTe_3, BaCuTbTe_3, BaAgTbTe_3, and "2_∞[AgUTe_3"1"-] layers for CsAgUTe_3. These layers comprise [MTe_4] tetrahedra and [LnTe_6] or [UTe_6] octahedra. Ba or Cs atoms separate these layers. As there are no short Q..Q (Q = S or Te) interactions these compounds achieve charge balance as Ba"2"+M"+Ln"3"+(Q"2"-)_3 (Q = S and Te) and Cs"+Ag"+U"4"+(Te"2"-)_3. (Copyright copyright 2015 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)
[en] Much research effort has been put in to study layered compounds with transition metal dichalcogenides (TMDs) being one of the most studied compounds. Due to their extraordinary properties such as excellent electrochemical properties, tuneable band gaps, and low shear resistance due to weak van der Waals interactions between layers, TMDs have been found to have wide applications such as electrocatalysts for hydrogen evolution reactions, supercapacitors, biosensors, field-effect transistors (FETs), photovoltaics, and lubricant additives. In very recent years, Group 5 transition metal ditellurides have received an immense amount of research attention. However to date, little has been known of the potential toxicities posed by these materials. As such, we conducted the cytotoxicity study by incubating various concentrations of the Group 5 transition metal ditellurides (MTe2; M=V, Nb, Ta) with human lung carcinoma epithelial A549 cells for 24 hours and the remaining cell viabilities after treatment was measured. Our findings indicate that VTe2 is highly toxic whereas NbTe2 and TaTe2 are deemed to exhibit mild toxicities. This study constitutes an exemplary first step towards the understanding of the Group 5 transition metal ditellurides' toxicity effects in preparation for their possible future commercialisation. (copyright 2018 Wiley-VCH Verlag GmbH and Co. KGaA, Weinheim)
[en] It has recently been reported that the low-dimensional rare-earth tritellurides RTe3 (R=La-Nd,Sm,Gd-Tm) enter an unidirectional, incommensurate charge-density-wave (CDW) state when cooled below a temperature TCDW1∝ 450-250 K, which decreases with increasing rare earth atomic number, due to the effect of chemical pressure. For the heavier R (i. e.: Dy-Tm), a second CDW appears at TCDW2< TCDW1, orthogonal to the first one. We have recently found that the application of external pressure induces a superconducting (SC) state in GdTe3, TbTe3 and DyTe3 at low temperatures, coexisting or competing with the two CDWs and the local moment rare-earth magnetism. In this talk, we present the results of experiments we have performed on these materials at high pressure and low temperature, to help develop an understanding of the origin of the superconducting state.
[en] Understanding electronic structures is important in order to interpret and to design the chemical and physical properties of solid-state materials. Among those materials, tellurides have attracted an enormous interest, because several representatives of this family are at the cutting edge of basic research and technologies. Despite this relevance of tellurides with regard to the design of materials, the interpretations of their electronic structures have remained challenging to date. For instance, most recent research on tellurides, which primarily comprise post-transition elements, revealed a remarkable electronic state, while the distribution of the valence electrons in tellurides comprising group-I/II elements could be related to the structural features by applying the Zintl-Klemm-Busmann concept. In the cases of tellurides containing transition metals the applications of the aforementioned idea should be handled with care, as such tellurides typically show characteristics of polar intermetallics rather than Zintl phases. And yet, how may the electronic structure look like for a telluride that consists of a transition metal behaving like a p metal? To answer this question, we examined the electronic structure for the quaternary RbTbCdTe and provide a brief report on the crystal structures of the isostructural compounds RbErZnTe and RbTbCdTe, whose crystal structures have been determined by means of X-ray diffraction experiments for the very first time.