Crystal Structure of W1−x B3 and Phase Equilibria in the Boron-Rich Part of the Systems Mo-Rh-B and W-{Ru,Os,Rh,Ir,Ni,Pd,Pt}-B

The crystal structure of W_1?x B₃ has been reinvestigated by x-ray single crystal diffraction and revealed isotypism with the Mo_1?x B₃ structure type (space group P6₃/mmc; a = 0.52012(1), c = 0.63315(3) nm; R _F = 0.040). As a characteristic feature of the structure, planar hexagonal metal layers (1/3 of atoms removed from ordered positions) sandwich planar boron honeycomb layers. One of the two W-sites shows a random defect of about 73%. Strong metal boron and boron-boron bonds are responsible for high mechanical stability. Although W_1?x B₃ at about 80 at.% B is the metal boride richest in boron, it contains no directly linked three-dimensional boron framework. The solubility of Rh, Ir, Ni, Pd and Pt in W_1?x B₃ as well as of Rh in Mo_1?x B₃ has been investigated in as cast state and after annealing. Furthermore, phase equilibria in the boron rich part of the corresponding isothermal sections W-TM-B (TM = Rh, Ir at 1100 °C, TM = Ni, Pd at 900 °C and TM = Pt at 800 °C) and Mo-Rh-B (at 1100 °C) have been established. A ternary compound only forms in the system W-Ir-B: τ₁-W_1?x Ir _x B₂ with ReB₂ structure type (space group P6₃/mmc; a = 0.2900, c = 0.7475 nm). The type of formation and crystal structure of diborides W_1?x TM _x B₂ (TM = Ru, Os, Ir) isotypic with ReB₂ were studied by x-ray powder diffraction and electron probe microanalysis in as cast state and after annealing at 1500 °C. Accordingly, W_0.5Os_0.5B₂ (a = 0.29127(1), c = 0.7562(1) nm) forms directly from the melt, whereas W_0.4Ru_0.6B₂ (a = 0.29027(1), c = 0.74673(2) nm) and W_0.6Ir_0.4B₂ (a = 0.29263(1), c = 0.75404(8) nm) are incongruently melting. Annealing at 1500 °C leads in case of the iridium compound to an almost single-phase product but the same procedure does not increase the amount of the ruthenium diboride.     

New equilibrium phase in the Fe–Ge system obtained by mechanical alloying

A new equilibrium phase has been found in the Fe–Ge system. It has the composition Fe₂Ge₃, and decomposes at about 580°C due to a peritectoid reaction, giving FeGe (cubic modification) and FeGe₂. The phase forms by a eutectoid reaction from FeGe₂ at about 530°C; however, this transformation is kinetically inhibited. The Fe₂Ge₃ compound is likely to have a tetragonal lattice, structure type of Ru₂Sn₃, a=5.59 Å, c=8.92 Å.     

Crystal structural properties of Ti3SnD

Ti₃Sn crystallises in hexagonal Ni₃Sn type structures. Upon deuteration a primary interstitial solid solution of deuterium in Ti₃Sn has been identified. At higher deuterium concentrations a cubic hydride phase is formed with the limiting composition Ti₃SnD. The structural properties of these phases have been refined from neutron powder diffraction intensities using the Rietveld method. The crystal structure of Ti₃SnD has been confirmed to crystallize in the CaTiO₃ type structure, space group Pm3m, with the unit cell parameter a=4.1769(4) Å. The deuterium atoms occupy Ti₆ octahedral voids in the cubic structure to 95.7(6)% and 72(6)% in the hexagonal.     

Nd2Ni2MgH8 hydride: Synthesis,structure and magnetic properties

Hydrogen interaction with intermetallic compound Nd₂Ni₂Mg crystallizing in the tetragonal Mo₂FeB₂ type of structure leads to the formation of hydride/deuteride containing 7.4–8 H(D)/f.u. Hydrogen absorption is accompanied by a monoclinic deformation of the unit cell with the crystal structure data refined from Synchrotron XRD (Sp. gr. P2₁/c; a = 11.60733(5) Å; b = 7.66057(3) Å; c = 11.78743(5) Å, β = 92.4126(4)°, V = 1047.194(8) ų) and high resolution powder XRD data. The formed interstitial hydride disproportionates during heating forming NdH₂. Nd₂Ni₂Mg is an antiferromagnet with the Néel temperature T_N ≈ 19 K. Presence of another magnetic phase transition at 14 K together with two metamagnetic transitions indicates a complicated magnetic phase diagram. The hydrogenation reduces T_N to 1.0 K.     

Phase Equilibria in the Sb<Subscript>2</Subscript>Te<Subscript>3</Subscript>–InSb System

The phase diagram of the (Sb₂Te₃)_100?x –InSb _x system was determined based on x-ray diffraction (XRD) analysis, differential thermal analysis (DTA), and microhardness and density measurements. An intermediate compound with composition Sb₂Te₃·2InSb was formed as a result of syntectic reaction, melting incongruently at 553 °C. This compound has tetragonal lattice with unit cell parameters of a = 4.3937 Å, b = 4.2035 Å, c = 3.5433 Å, α = 93.354°, and β = γ = 90°. Sb₂Te₃·(2 + δ)InSb (?1 ≤ δ ≤ +1) and (Sb₂Te₃)_100?x (InSb) _x (90 ≤ x ≤ 100) solid solutions exist in the investigated system, based on the intermediate compound Sb₂Te₃·2InSb and on InSb, respectively. Also, two invariant equilibria exist in the system, with eutectic point coordinates at compositions of x = 60 and x ≈ 85 mol% InSb and eutectic temperatures of T _E = 541 and T _E ≈ 501 °C, respectively.     

Synthesis,structure of a new acceptor TBA2S6 and preparation,physical properties of ET3S6

A general procedure for the synthesis of the tetrabutylammoium hexasulphide, TBA₂S₆, is first described. The structure of TBA₂S₆ has been determined by X-ray crystallography. Lattice parameters and space group information are as follows: a=15.039(5) Å, b=16.086(5) Å, c=17.078(6) Å, α=β=γ=90.00°, V=4131.5(24) ų, orthorhombic, Pbnb (Z=4). Diffraction data (MoK_α radiation, 2θ_max=50) is collected by Rigaku-AFC6 diffract meter. The structure was solved and refined by direct method and full-matrix least-squares procedures to R-value of 0.0645. The complex ET₃S₆ has been prepared through electrocrystallization ways. The conductivity of this salt at room temperature is 2.3 S cm⁻¹. It shows weak metallic behavior above 240 K. Below this temperature, it becomes a semiconductor. The XPS spectra indicated the presence of three different kinds of S atoms in the salt. The ESR line width is found to be 44.478 G at room temperature.     

Preparation,crystal structures and electrical conducting properties of new charge-transfer salts: (ET)2·SO3CF3 and (ET)·ClO4

Two new charge-transfer (CT) salts: (ET)₂·SO₃CF₃ and (ET)·ClO₄ were prepared by chemical oxidation of ET with AgSO₃CF₃ and AgClO₄, respectively. Their crystal structures were determined: monoclinic system, Cc, a=35.239(7) Å, b=6.5440(13) Å, c=14.646(3) Å, β=110.26(3)°, V=3168.5(11) Å³ for (ET)₂·SO₃CF₃; monoclinic system, C2/c, a=15.981(3) Å, b=10.627(2) Å, c=11.495(2) Å, β=120.61(3)°, V=1680.2(6) Å³ for (ET)·ClO₄. Electrical conductivity measurements indicate that (ET)₂·SO₃CF₃ shows semi-conducting behaviour with room temperature conductivity of 0.29 S cm⁻¹, while (ET)·ClO₄ is an insulator.     

Isothermal Section of Er-Ag-Sn System at 873 K

The isothermal section of the Er-Ag-Sn system at 873 K was constructed with the use of scanning electron microscopy, energy-dispersive x-ray microanalysis and x-ray powder diffraction. Two ternary compounds were confirmed at this temperature: ErAgSn (LiGaGe structure type, P6₃mc, Z = 2, a = 4.6595(2) Å, c = 7.2872(3) Å) and non-stoichiometric phase ErAg_1?xSn_2+x (Cu₃Au structure type, Pm-3m, Z = 1). For the last one homogeneity range was established (0.08 < x < 0.24) and lattice parameters were determined (a = 4.5007(4), 4.5040(2), 4.5107(1), 4.5412(1) Å for the compositions Er_25.4Ag_23.4Sn_51.2, Er_25.7Ag_23.0Sn_51.3, Er_25.7Ag_21.7Sn_52.6, Er_25.2Ag_18.6Sn_56.2 (at.%) respectively). Melting point of the phase Er_25.7Ag_21.7Sn_52.6 (at.%) was determined to be 1199 K by differential thermal analysis.     

Crystal structure and magnetic properties of the binary uranium–nickel alloy UNi4

The crystal structure of binary UNi₄ was studied from single crystal X-ray diffraction data. This compound crystallises with CaCu₅ structure type (space group p6/mmm), with the unit-cell dimension: a=4.8457(2) Å, c=4.0451(2) Å. This phase belongs to the limited solid solution U_1+xNi_5−x with 0.20<x<0.33, where U atoms substitute partially Ni on its two crystallographic sites. UNi₄ is paramagnetic down to 4.2 K.     

Crystal and electronic structures and physical properties of two semiconductors: Pb4Sb6Se13 and Pb6Sb6Se17

The title compounds were synthesized by directly reacting the elements in stoichiometric ratios at elevated temperatures. Their crystal structures were determined by single crystal X-ray diffraction. Pb₄Sb₆Se₁₃ crystallizes in the monoclinic space group I2/m with lattice dimensions of a=24.591(1) Å, b=4.0910(2) Å, c=25.212(1) Å, β=93.943(1)°, V=2530.3(2) Å³ (Z=4), while Pb₆Sb₆Se₁₇ crystallizes in the orthorhombic space group P2₁2₁2 with lattice dimensions of a=15.872(4) Å, b=24.061(7) Å, c=4.1382(9) Å, V=1580.4(7) Å³ (Z=2). Electronic structure calculations predicted semiconducting behavior. Temperature dependent electrical conductivity measurements verified this prediction for Pb₄Sb₆Se₁₃.     

New bisdithiolene metal complex of the 2-thioxo-1,3-dithiole-4,5-dithiolato(dmit) ligand. Preparation,structure and physical properties

The complex HMEDA[Ni(dmit)₂]₂I (HMEDA=Hexamethylethylenediammonium) has been prepared. A single X-ray crystal structure analysis reveals that there are short S⋯S contacts between Ni(dmit)₂ dimmers. The monoclinic system, space group p2/n, has cell dimensions: a=11.710(3) Å, b=22.559(5) Å, c=7.374(2) Å, β=93.000(3)⁰, V=1945.3(8) ų, z=4. Full-matrix least-squares refinement, based on 2989 reflections converged at R=0.0686. The conductivity of this salt at room temperature is 0.1 S cm⁻¹ and it shows semiconducting behavior from 20 to 300 K.     

Phase equilibria in the system Au–Cu–Si and structural characterization of the new compound Au5±xCu2±xSi

The ternary Au–Cu–Si system was investigated by means of powder X-ray diffraction (XRD) for phase identification, scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX) for microstructures and chemical compositions, light optical microscopy (LOM), and differential thermal analysis (DTA) for the determination of thermal effects. Three isothermal sections were constructed at 250 °C, 400 °C and 650 °C. A new ternary compound τ, Au_5±xCu_2±xSi, was identified and its crystal structure was determined by means of single crystal X-ray diffraction. It adopts a new crystal structure type in space group Pnma, Pearson symbol oP32 and shows a composition range between Au_5.6Cu_1.4Si and Au_4.4Cu_2.6Si at 250 °C. Lattice parameters were found to vary between a = 9.64–9.50 Å, b = 7.61–7.64 Å and c = 6.90–6.89 Å from the Au-rich to the Au-poor composition limit. Three vertical sections, at 10 and 30 at.% Si and at 10 at.% Cu, were constructed based on DTA data and four invariant ternary phase reactions were identified. A partial ternary reaction scheme (Scheil diagram) and a partial liquidus projection are given.     

Radical cation salts of bis (ethylenediseleno) tetrathiafulvalene with halide mercurate anions

Four bis(ethylenediseleno) tetrathiafulvalene (BEDSe-TTF)-based salts, (BEDSe-TTF)₂Hg₂X₂ (X=I. Br), (BEDSe-TTF)₄Hg₃Br₈ · C₂H₃Cl₃ and (BEDSe-TTF)₄Hg₃Br₄ · 1.5C₂H₃Cl₃, have been prepared by electrocrystallization. Two of them. (BEDSe-TTF)₂Hg₂X₆, have been characterized by X-ray crystallography. The triclinic (space group Pī) room-temperature lattice parameters when X=I are: a = 6.798(4),b = 10.728(7), c 15.905(9) Å, α=106.33(6)°, ß=99.78(4)°, γ-92.97(5), V = 1090(1) ų. When X =Br the parameters are: a=6.665(3), b= 10.314(5), c=15.720(7) Å, α-105.70(4)°, ß=99.65(4)°, γ=93.79(4)°, V = 1018(1) ų. At room temperature, (BEDSe-TTF)₄Hg₃Br₈ · C₂H₃Cl₃ is metallic and the others are semiconductors.     

The Systems Tantalum (Niobium)-Cobalt-Boron

Constitution of the ternary systems Nb-Co-B and Ta-Co-B was studied, employing optical and electron microscopy, x-ray powder, single crystal diffraction, electron probe microanalysis, DTA and Pirani melting point measurements. Ternary phase equilibria were determined within an isothermal section at 1100 °C. For the Co-rich part (≥50 at.% Co) of the system, a liquidus surface projection and a corresponding Schulz-Scheil reaction scheme were constructed in combination with data for primary crystallization from as-cast samples determined by SEM and EPMA measurements. The crystal structures of novel ternary compounds have been elucidated by x-ray powder and single crystal diffraction and were supported by TEM. {Nb,Ta}CoB with NbCoB-type exhibits a high temperature modification (ZrAlNi-type, a = 0.5953 nm, c = 0.3248 nm; a = 0.5926 nm, c = 0.3247 nm for Nb and Ta respectively), which was only present in as-cast alloys, but found to be stabilized by the addition of Fe to annealing temperatures of 1400 °C. Ta₃Co₄B₇ (a = 0.3189 nm, b = 1.8333 nm, c = 0.8881 nm) was proven to be isotypic with Nb₃Co₄B₇. The novel orthorhombic compounds {Nb,Ta}Co₂B₃ (TaCo₂B₃-type with space group Pnma; a = 0.53628 nm, b = 0.32408 nm, c = 1.24121 nm for TaCo₂B₃; a = 0.53713 nm, b = 0.32442 nm, c = 1.2415 nm for NbCo₂B₃) adopt unique structure types with branched boron zig-zag chains. {Nb,Ta}Co₂B were found to crystallize in a unique monoclinic structure type (space group P2 ₁/c; a = 0.9190 nm, b = 0.64263 nm, c = 0.63144 nm; β = 109.954°, for Nb) very close to an orthorhombic setting (Cmce, a = 0.63162 nm, b = 1.72810 nm, c = 0.64270 nm, for Nb). Substitution of Co by Ni stabilizes a smaller orthorhombic lattice with Re₃B-type structure (Cmcm) although no homologue compound in the Ni-system exists. The crystallographic relations among the structure types of Re₃B and pseudo-orthorhombic as well as monoclinic {Nb,Ta}Co₂B were defined in terms of a Bärnighausen scheme. DFT calculations revealed very close stabilities for the three competing structure types for {Nb,Ta}Co₂B. Detailed transmission electron microscopy (TEM) for Nb(Co,Fe)B, {Nb,Ta}Co₂B,  {Nb,Ta}(Co,Ni)₂B, and Ta₃Co₄B₇ confirmed lattice geometries and crystal symmetry. Vickers hardness was measured for {Nb,Ta}Co₂B, {Nb,Ta}(Co,Ni)₂B, {Nb,Ta}_2?x Co_21+x B₆ and {Nb,Ta}Co₂B₃ exhibiting the highest value of hardness of HV = 22.4 ± 1.1 GPa for TaCo₂B₃. Magnetic, specific heat and electrical resistivity measurements on the compounds TaCo₂B and Ta₂Co₂₁B₆ reveal paramagnetic and ferromagnetic metallic ground states, respectively.     

Magnetic structure of Tb2CuIn3

The intermetallic compound Tb₂CuIn₃ has been studied by means of neutron diffraction at various temperatures ranging from 293 to 3.8 K. Data analysis of the high temperature region confirms the hexagonal crystal structure (space group P6/mmm) with Tb at 1a, Cu and In statistically distributed at 2d positions. The unit cell constants are a=4.702(1) Å and c=3.682(2) Å. Below 33 K, Tb₂CuIn₃ undergoes a magnetic phase transition into a collinear antiferromagnetic structure described in an orthorhombic unit cell with A=a, B=a√3, C=c. Terbium magnetic moments of 6.8 μ_B at 3.8 K are oriented along the c axis. Complementary susceptibility measurements confirm the transition temperature. The magnetic isotherm at 5 K in fields with μ_oH up to 7 T is far from saturation.     

450 °C Isothermal Section of the Ni-Sb-Zn Ternary System at the Zn-Rich Corner

The 450 °C isothermal section of the Ni-Sb-Zn ternary system with an emphasis on the Zn-rich corner was experimentally determined by means of optical microscopy, SEM-EDS analysis and x-ray diffraction. The existence of two true ternary phase, the NiSbZn (τ₁) and Ni₂SbZn₂ (τ₂) phase, was confirmed in the system at 450 °C. NiSbZn (τ₁) had an MgAgAs-type structure with a lattice parameter a = 0.58971 nm. Ni₂SbZn₂ (τ₂) is a ternary compound found in this system for the first time whose composition range spanned from 35.5-38.0 at.% Ni, 17.3-26.3 at.% Sb, 36.9-45.2 at.% Zn. It should be noted that the phase relationships at 450 °C are significantly different from the previous reported ones at 600 and 297 °C. The solubilities of Ni in SbZn, Sb₃Zn₄ and Sb₂Zn₃ were limited. The maximum solubilities of Sb in δ-NiZn₈, γ-NiZn₃ and β₁-NiZn were 0.1, 4.0 and 1.5 at.%, respectively and the maximum solubilities of Zn in NiSb and NiSb₂ were 5.6 and 1.6 at.%, respectively.     

Crystal structure of the new ternary indide CePt2In2 and the isostructural compounds RPt2In2 (R=La,Pr, Nd)

The title compounds have been synthesized by arc melting of the elemental components and subsequent annealing at 870 K. The crystal structure of CePt₂In₂ was determined from single-crystal X-ray data (R=0.0437 for 1439 |F| values and 62 variables). It represents a new structure type of intermetallic compounds: P2₁/m, mP20, a=10.189(6), b=4.477(4), c=10.226(6) Å, β=117.00(5)°, V=416.1(1) ų, Z=4. Isostructural compounds have been found also for La, Pr, and Nd.     

Isothermal section at 950 °C of the U–Fe–B ternary system

A systematic investigation of the isothermal section at 950 °C of the U–Fe–B ternary system was done by means of X-ray powder diffraction, scanning electron microscopy, complemented by energy dispersive X-ray spectroscopy, and electron-probe microanalysis. At this temperature the phase diagram is characterized by the formation of four ternary compounds with negligible homogeneity regions. The compounds are: UFeB₄ (orthorhombic YCrB₄-type structure, a = 5.887(1) Å, b = 11.412(2) Å and c = 3.4355(4) Å), UFe₃B₂ (hexagonal CeCo₃B₂-type structure, a = 5.049(1) Å and c = 2.9996(7) Å), ∼UFe₄B (structure closely related with the CeCo₄B-type, and a small hexagonal cell a = 4.932(1) Å and c = 7.037(2) Å), and U₂Fe₂₁B₆ (Cr₂₃C₆-type structure, a = 10.766(4) Å).     

700 °C Isothermal Section of the Al-Ti-Si Ternary Phase Diagram

The 700 °C isothermal section of the Al-Ti-Si ternary phase diagram has been determined experimentally by means of scanning electron microscopy coupled with energy dispersive x-ray spectroscopy and x-ray powder diffraction. Fourteen three-phase regions have been determined experimentally in the isothermal section at 700 °C. The ternary phases τ₁ (I4₁/amd, Zr₃Al₄Si₅-type) and τ₂ (Cmcm, ZrSi₂-type) are confirmed in the system at 700 °C. The compositions of τ₁ and τ₂ are found as Al_6.2-9.3Ti_32.4-34.0Si_57.5-60.9 and Al_10.0-11.6Ti_34.2-34.5Si_53.9-55.6, respectively. The τ₃ and Ti₃Al₅ phases are not found in the section. The Ti-rich corner at 700 °C shows the presence of three three-phase equilibriums, i.e., (TiAl + Ti₃Al + Ti₅Si₃), (α-Ti + Ti₃Si + Ti₅Si₃) and (α-Ti + Ti₃Al + Ti₅Si₃). The maximum solubility of Al in Ti₅Si₃, Ti₃Si and α-Ti is 6.0, 1.5 and 13.9 at.% at 700 °C, respectively. The maximum solubility of Si in L-Al, TiAl₃, TiAl₂, TiAl, Ti₃Al and α-Ti is 24.1, 13.6, 1.5, 0.8, 2.3 and 2.3 at.%, respectively.     

Crystal and electronic structures of the radical cation salt based on EDT-TTF and the photochromic nitroprusside anion, (EDT-TTF)3[Fe(CN)5NO]

A single crystal X-ray diffraction (XRD) study of the radical cation salt (EDT-TTF)₃[Fe(CN)₅NO] has been carried out (a=6.623(3), b=10.487(2), c=15.951(1) Å, α=109.19(1), β=96.30(2), γ=99.15(3)°, V=1017.3(5) Å³, space group P1, Z=1). The crystals have a layered structure with the distinctive feature of the presence of alternating EDT-TTF dimers and monomers in the radical cation stacks. Both the structural features and the calculated HOMO⋯HOMO interaction energies suggest that the strong intradimer interaction is responsible for the charge separation and the semiconducting properties of the salt.