- Synthesis of copper, silver, and samarium chalcogenides by mechanical alloying
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CuInX2 (X = S, Se, Te), Ag2S, Ag2Se, Ag3Te2, Ag1.9Te, AgCuSe, Sm3Se4, Sm2Se3, and SmTe were synthesized by a mechanical alloying method, using a high-energy planetary ball mill. The compounds were obtained by milling mixtures of the elements with desired ratios in agate or Cu-Be vials for 60-180 min. Copyright
- Ohtani,Maruyama,Ohshima
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- Physicochemical study of SmTe-In2Te3 and SmTe-InTe systems
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SmTe-In2Te3 and SmTe-InTe quasi-binary joins were studied using physicochemical methods. The SmTe-In2Te3 system forms two compounds, SmIn2Te4 and SmIn 4Te7, which melt
- Akhmedova,Agapashaeva,Aliev
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- Cs2Gd6N2Te7: The first quaternary nitride telluride of the lanthanides
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The first quaternary nitride telluride with trivalent gadolinium, Cs2Gd6N2Te7, was obtained by the reaction of metallic gadolinium with cesium azide, elemental tellurium, and gadolinium trichloride as well as cesium chloride as flux at 900 °C for 7 days in evacuated silica tubes. Single crystals occur as long black needles and crystallize in the monoclinic space group C2/m (a = 2403.1(2) pm, b = 424.03(3) pm, c = 1142.91(7) pm, β = 103.709(4)°, Z = 2). Three crystallographically different Gd3+ cations constitute the structure, two are coordinated by one N3- (d(Gd(1/2)-N) = 217 pm) and five Te2- anions (d(Gd(1/2)-Te) = 305-326 pm), and the third Gd3+ by two N3- (d(Gd(3)-N) = 244 pm) and four Te2- anions (d(Gd(3)-Te) = 316-317 pm), all forming distorted octahedra about Gd3+. The Cs+ cation shows a perfect bicapped trigonal prism (C.N. = 8, d(Cs-Te) = 383-431 pm) as coordination sphere. Two of these polyhedra are condensed via a common (non-capped) rectangular face building up double prisms [Cs2Te12]22-. Further linkage via triangular faces (along [0 1 0]) and two of the four caps (along [0 0 1]) results in corrugated layers [Cs2Te7]12- running parallel to (1 0 0). However, the main feature of the crystal structure comprises N3--centered (Gd3+)4 tetrahedra (d(N-Gd) = 217 pm (2×) and 244 pm (2×); {measured angle}(Gd-N-Gd) = 107° (2 + 2 + 1×) and 121° (1×)), which are connected via two vertices each to build up one-dimensional infinite chains ∞1{ [ N (Gd 1)1 / 1t (Gd 2)1 / 1t (Gd 3)2 / 2v ]6 + } (t = terminal, v = vertex-shared) along [0 1 0] like in the structure of the M3NCh3-type nitride chalcogenides with M = La-Nd, Sm, Gd-Dy, and Ch = S, Se.
- Lissner, Falk,Schleid, Thomas
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- Two new binary lanthanide polytellurides: Syntheses and crystal structures of CeTe1.90 and SmTe1.80
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Single crystals of the new binaries CeTe1.90 and SmTe1.80 have been obtained. CeTe1.90 was synthesized at 1023 K from the reaction of Ce, TeO2, and Te with the use of a CsCl flux. It crystallizes in the tetragonal space group P42/n with 20 formula units in a cell of dimensions at 153 K of a = 10.0261 (5), c = 18.1336 (12) A, V = 1822.84 (18) A3. It is isostructural with the LnSe1.9 polyselenides (Ln=La, Ce, Pr) and with SmS1.90. SmTe1.80 was synthesized at 1223 K from the reaction of Sm and Te in a KBr flux. SmTe1.80 crystallizes in a new structural type in the tetragonal space group P4/n with 20 formula units in a cell of dimensions at 153 K of a = 9.7026 (4), c = 18.0072 (14) A, V = 1695.21 (14) A3. Both of these layered structures, which may be derived from the ZrSiS structure type, consist of double layers of [LnTe] polyhedra separated by planar Te nets that contain vacancies. In these nets the shortest Te-Te distances are 2.9194(5), 3.1204(5), and 3.3324(6) A in CeTe1.90 and 2.878(1), 2.9932(3), and 3.2114(7) A in SmTe1.80. Neither a simple delineation of the Te-Te bonding nor an assignment of individual formal oxidation states is possible in either of these compounds if one takes strict account of the Te-Te distances.
- Ijjaali, Ismail,Ibers, James A.
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- Structural Variations and Bonding Analysis of the Rare-Earth Metal Tellurides RETe1.875±Δ(RE = Ce, Pr, Sm, Gd; 0.004 ≤ δ≤ 0.025)
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Crystals of RETe1.875±Δ (RE = Ce, Pr, Sm, Gd; 0.004 ≤ δ≤ 0.025) were grown using alkali halide flux and chemical transport reactions. The crystal structures are described in space group Amm2 (no. 38), with lattice parameters of a = 13.3729(5) ?, b = 17.7918(5) ?, c = 18.1561(4) ? for CeTe1.87(1) (T = 100 K), a = 13.271(2) ?, b = 17.747(3) ?, c = 18.160(3) ? for PrTe1.85(1) (T = 100 K), a = 13.1251(6) ?, b = 17.4269(8) ?, c = 17.8808(8) ? for SmTe1.87(1) (T = 100 K), and a = 13.1762(4) ?, b = 17.4995(5) ?, c = 17.9591(5) ? for GdTe1.88(1) (T = 296 K). The structures contain alternating stacks of puckered [RETe] slabs and planar [Te] layers. The latter are composed of small anionic entities, such as Te2- and Te22-, along with a large anionic eight-membered Te ring, as supported by electron localizability indicator-based bond analysis for an ordered model of GdTe1.875. Slightly different patterns for individual compounds indicate a considerable structural flexibility. Temperature-dependent resistance measurements confirm semiconducting behavior for PrTe1.875±Δ and GdTe1.875±Δ (magnetic data evidence RE3+ and an antiferromagnetic transition at TN = 4 K for CeTe1.875±Δ and TN = 11 K for GdTe1.875±Δ), whereas PrTe1.875±Δ and SmTe1.875±Δ show no long-range order down to 2 K.
- Poddig, Hagen,Gebauer, Paul,Finzel, Kati,St?we, Klaus,Doert, Thomas
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- The Superstructure of Semiconducting SmTe2-x
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SmTe1.84was synthesized and the crystal structure was studied by the single-crystal technique. The substructure was isostructural with LaTe2-x, where corrugated rock salt LaTe slabs alternate with planar tellurium square lattices. The substructure of SmTe1.84is tetragonal anti-Cu2Sb type and the superstructure is √5×√5 of the tetragonal subcell. The superstructure is tetragonal, withP42/nsymmetry,a=9.709(1) A andc=18.007(7) A. There are both ordered and disordered defects in the Te sheet. The superstructure obtained consists of the three possible stable solutions suggested by Lee and Foran, and all three solutions were found in a single crystal. The resistivity dependence on temperature indicates that SmTe1.84is semiconducting, which seems due to structural modulation. The structural stability of the other phases of SmTen(n=1-2) is discussed in terms of temperature and ionic radius ratio.
- Park, Seon-Mi,Park, So-Jeong,Kim, Sung-Jin
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- BAND EDGE EXCITION SPECTRA IN Sm MONOCHALCOGENIDES.
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Reflection spectra have been measured on semiconducting SmS, SmSe and SmTe single crystals at 2 K in the photon energy region from 3 to 6 ev. From a comparison of the spectra in these Sm monochalcogenides with those in BaS and BaSe, the reflection peaks observed in this photon energy region are identified as the Wannier excitons associated with the band-edges at the X-point and the GAMMA -point. Temperature dependence of the reflection peaks and the electroreflectance spectra of SmSe support this identification. The energy band structure of semiconducting Sm monochalcogenides is discussed on the basis of the observed exciton spectra.
- Kurita,Kaneko,Koda
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- THERMODYNAMICS OF VAPORIZATION OF SAMARIUM(II) TELLURIDE AND YTTERBIUM(II) TELLURIDE: A DISCUSSION OF THE THERMOCHEMISTRY OF THE DIVALENT LANTHANOID AND ALKALINE EARTH TELLURIDES.
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The congruent vaporization of the solid monotellurides of ytterbium and samarium, both of practically stoichiometric composition, was studied over the temperature ranges 1606-1764 and 1732-1922 K, respectively, by the Knudsen effusion weight-loss technique. Using enthalpy and entropy data from the literature for gaseous LnTe, Ln, Te//2, and Te, and estimated data for solid LnTe(Ln equals Yb, Sm) it could be concluded from thermodynamic calculations that within the given temperature ranges-Ln and Te are the principal vapor species and that less than equivalent to 2. 8 and less than equivalent to 0. 9 mol percent of the vapor is present as YbTe and SmTe, respectively.
- Petzel,Ludwigs
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