Pyrochlore phases in the system ZnOBi2O3Sb2O5: II. Crystal structures of Zn2Bi3.08Sb2.92O14+δ and Zn2+xBi2.96−(x−y)Sb3.04−yO14.04+δ

Rietveld refinement of combined X-ray and neutron diffraction data has, within errors, confirmed the stoichiometries of two, cubic pyrochlore phases in the ZnOBi₂O₃Sb₂O₅ system. Neither phase has the ‘ideal’ stoichiometry, Zn₂Bi₃Sb₃O₁₄. One phase, P₁, is a Zn-rich, Bi-deficient solid solution Zn_2+xBi_{2.96−(x−y)}Sb_3.04−yO_14.04+δ. The other, P₂, is a Bi-rich line phase, stoichiometry Zn₂Bi_3.08Sb_2.92O_14+δ. Both structures have a mixture of Bi, Zn on the A-sites and Zn, Sb on the B-sites. However, Zn is displaced off-centre in the A-sites to achieve lower co-ordination number with realistic ZnO bond lengths. Additional structural complexities arise from: displacement of O(2) atoms; partial occupancies of O(1) and O(2) sites; partial occupancy of a third, interstitial oxygen site, O(3). Since the multiplicities of the off-centre sites are much higher than those of the ideal positions, there is considerable possibility for correlated short range order throughout the structures.     

Investigation into the surface selective oxidation of dual‐phase steels by XPS,SAM and SIMS

Surface selective oxides created during continuous annealing (MnO, SiO₂, etc.) can have a deleterious effect on coating adhesion after hot‐dip galvanizing. Earlier research works have made it clear that increasing the annealing atmosphere oxidizing potential can alleviate the problem by reducing external surface selective oxidation. In the present study, increasing the water vapour content of the nitrogen–hydrogen protective gas mixture was used to raise its oxidizing potential. The technique was applied to a classical dual‐phase steel (0.15% C, 1.5% Mn, 0.45% Si, 0.05% Al…) that was annealed for 60 s at 800–810°C in protective atmospheres of nitrogen and 5% hydrogen with water vapour contents ranging from 10 to 6000 ppm. Post‐annealing surfaces were characterized by x‐ray photoelectron spectroscopy (XPS), secondary ion mass spectroscopy (SIMS) and scanning Auger microscopy (SAM). In situ XPS analyses were carried out right after simulation annealing in the preparation chamber connected to the spectrometer, never returning the specimens to air. This made it possible to identify in a reliable way the elements that segregated to the surface during the treatment, and to determine their corresponding oxidation states. On the other hand, the high sensitivity of SIMS was taken advantage of to assess oxide in‐depth concentration profiles (SiO₂, Al₂O₃, FeO) as a function of the annealing conditions, and SAM was used to characterize the corresponding oxide particle morphology. External selective oxidation was thus shown to decrease with increasing water vapour contents in the atmosphere (from 80 to 6000 ppm), whereas internal oxidation increases drastically to ～4 μm below the free surface. At 10 ppm of H₂O the oxygen partial pressure is very low and the external selective oxidation results in a thin, but almost complete, coverage of the steel surface. Consequently, metallic iron cannot be observed at the surface, thus hampering hot‐dip galvanizability, unless the water vapour content is raised to 6000 ppm. Various surface morphologies were observed and discussed. In the authors' opinion, basic investigations of this type are an indispensable first step to improving the response of highly alloyed steels (dual‐phase, TRIP) to hot‐dip galvanizing. Copyright © 2003 John Wiley & Sons, Ltd.     

Ternary K2Zn5As4‐type pnictides Rb2Cd5As4 and Rb2Zn5Sb4, and the solid solution Rb2Cd5(As,Sb)4

Dirubidium pentacadmium tetraarsenide, Rb₂Cd₅As₄, dirubidium pentazinc tetraantimonide, Rb₂Zn₅Sb₄, and the solid‐solution phase dirubidium pentacadmium tetra(arsenide/antimonide), Rb₂Cd₅(As,Sb)₄ [or Rb₂Cd₅As_3.00(1)Sb_1.00(1)], have been prepared by direct reaction of the component elements at high temperature. These compounds are charge‐balanced Zintl phases and adopt the orthorhombic K₂Zn₅As₄‐type structure (Pearson symbol oC44), featuring a three‐dimensional [M₅Pn₄]²⁻ framework [M = Zn or Cd; Pn is a pnicogen or Group 15 (Group V) element] built of linked MPn₄ tetrahedra, and large channels extending along the b axis which host Rb⁺ cations. The As and Sb atoms in Rb₂Cd₅(As,Sb)₄ are randomly disordered over the two available pnicogen sites. Band‐structure calculations predict that Rb₂Cd₅As₄ is a small‐band‐gap semiconductor and Rb₂Zn₅Sb₄ is a semimetal.     

Phase relations and structural properties of the ternary narrow gap semiconductors Zn5Sb4In2−δ (δ=0.15) and Zn9Sb6In2

A systematic study of the Zn-rich corner of the ternary system Zn-Sb-In revealed the presence of two ternary compounds: stable Zn₅Sb₄In_2−δ (δ=0.15) and metastable Zn₉Sb₆In₂ with closely related crystal structures. Their common motif is a tetragonal basic structure of 3²434 nets formed by the Sb atoms. The nets are stacked in antiposition to yield layers of square antiprisms sharing edges plus intervening tetracapped tetrahedra (tetreadersterns). The majority of Zn atoms occupy peripheral tetrahedra of such tetraedersterns, which produces frameworks with a composition “ZnSb”. These frameworks represent orthorhombic superstructures: (2×1×1) for Zn₅Sb₄In_2−δ (Z=4) and (2×3×1) for Zn₉Sb₆In₂ (Z=8) with respect to the tetragonal arrangement of Sb atoms. The In and remaining Zn atoms are distributed in the channels formed by the square antiprisms. Phase relations in the Zn-Sb-In system are complex. Crystals of metastable Zn₉Sb₆In₂ are regularly intergrown with various amounts of Zn₅Sb₄In_2−δ. Additionally, a monoclinic variant to orthorhombic Zn₉Sb₆In₂ could be identified. Zn₉Sb₆In₂ decomposes exothermically into a mixture of Zn₅Sb₄In_2−δ, Zn₄Sb₃ and elemental Zn at around 480 K. Both Zn₅Sb₄In_2−δ and Zn₉Sb₆In₂ are poor metals with resistivity values that are characteristic of heavily doped or degenerate semiconductors (0.2−3 m Ω cm at room temperature).     

Influence of soaking duration on the selective oxidation and galvanizability of a high‐strength dual phase steel

High‐strength dual phase steels readily exhibit bad galvanizability and coating defects because of selective oxides formed on steel surface during the annealing process prior to galvanizing. To investigate selective oxidation of alloying elements and their effects on glavanizability, a high‐strength dual phase steel was annealed with soaking duration for 45, 90, and 120 s, respectively, and then galvanized using a hot‐dip simulator. Field‐emission scanning electron microscopy characterization revealed that when dual phase steel was soaked for 45 s, selective oxides mainly precipitated along grain boundaries, while only a few of the oxides formed on grains. With soaking duration increased, oxides were so dense that nearly all steel surface was covered, leaving little bare area of the steel surface. Further XPS analysis showed that selective oxides mainly consisted of MnO and Cr₂O₃. In addition, the chemical nature of oxides did not change at all although soaking duration prolonged. Scanning Auger microprobe depth profiles presented that Mn had a much higher tendency to segregate than Cr and Mo. Oxygen penetration depth to subsurface was promoted as soaking duration increased. The formation of interfacial inhibition layer was founded to be greatly influenced by the density and size of surface oxides. The widely spaced small oxides had virtually no adverse effect on wettability because of aluminothermic reduction of oxides by the bath dissolved Al. As the oxides became dense and considerably big, the grains of the inhibition layer in some certain zones became coarse and the galvanizability tended to deteriorate. Copyright © 2011 John Wiley & Sons, Ltd.     

RbSb2 – Eine mit KSb2 verwandte Zintl‐Phase

RbSb₂ – A Zintl Phase related to KSb₂ The electron‐precise Zintl compound RbSb₂, which was known to melt incongruently at 418 °C, has been prepared in pure phase from elemental rubidium and antimony in sealed tantalum crucibles. In accordance with the ribbon‐shaped antimonide anions, the compound crystallizes with extremely thin intergrown, mechanically and chemically very sensitive needles of dark‐metallic lustre. The crystal structure could be determined and refined using single crystal x‐ray data (monoclinic, space group C2/m, a = 1403(2), b = 414.0(4), c = 855.7(14) pm, β = 104.45(12)°, Z = 4, R1 = 0.0901) despite the poor quality of the crystals. It shows fused six‐membered rings of two‐ and three‐bonded Sb atoms forming ribbons running along the monoclinic b axis, which can be interpreted as sections of the elemental structure of antimony (d_Sb‐Sb = 281.9(5) and 286.0(9) pm respectively). The structure of RbSb₂ is thus closely related to that of KSb₂, which exhibits identical antimony anions. Compared to the potassium compound, the ribbons are reoriented against each so that the coordination number of the A counter ions is increased from 6 + 2 (for A = K) to 8 + 2 (for A = Rb). The results of a FP‐LAPW band structure calculation of RbSb₂ are used to explain the chemical bonding in this classical Zintl phase with a calculated indirect band gap of 0.38 eV.     

Effect of metal doping on the low-temperature structural behavior of thermoelectric β-Zn4Sb3

The low-temperature structural phase transitions of Bi, Pb, In and Sn-doped samples of thermoelectric Zn₄Sb₃ have been characterized on crystals grown from molten metal fluxes, using electrical resistance and single crystal X-ray diffraction measurements. Room temperature stable, disordered, β-Zn₄Sb₃ undergoes two phase transitions at 254 and 235 K to the consecutively higher ordered phases α and α′, respectively. The ideal crystallographic composition of α-Zn₄Sb₃ is Zn₁₃Sb₁₀. The α-α′ transformation is triggered by a slight and homogenous Zn deficiency with respect to this composition and introduces a compositional modulation in the α-Zn₄Sb₃ structure. When preparing β-Zn₄Sb₃ in the presence of metals with low melting points (Bi, Sn, In, Pb) the additional metal atoms are unavoidably incorporated in small concentrations (0.04-1.3 at%) and act as dopants. This incorporation alters the subtle balance between Zn disorder and Zn deficiency in Zn₄Sb₃ and has dramatic consequences for its low-temperature structural behavior. From molten metal flux synthesis it is possible to obtain (doped) Zn₄Sb₃ samples which (1) only display a β-α transition, (2) only display a β-α′ transition, or (3) do not display any low-temperature phase transition at all. Case (2) provided diffraction data with a sufficient quality to obtain a structural model for highly complex, compositionally modulated, α′-Zn₄Sb₃. The crystallographic composition of this phase is Zn₈₄Sb₆₅.     

Mise en évidence de l'entité Sb2F4O dans un composé d'addition moléculaire avec l'urée étude structurale de [(NH2)2CO]2,Sb2F4O

The X-ray structure determination of [NH₂)₂CO]₂ · Sb₂F₄O shows the existence of linked units urea-Sb₂F₄O which show the Sb₂F₄O entity, not yet known. Crystal structure was solved with a singlecrystal X-ray diffraction study (the final R value is 0.046). The Sb₂F₄O unit is composed of a symmetric and short SbOSb bridge, and of four fluorine atoms, two being bonded to each antimony atom and situated in trans position relative to the SbOSb bridge. The bridge bond strength is assigned to a pπdπ overlap.     

Molecular Precursors for the Phase‐Change Material Germanium‐Antimony‐Telluride,Ge2Sb2Te5 (GST)

This review provides an overview of the precursor chemistry that has been developed around the phase‐change material germanium‐antimony‐telluride, Ge₂Sb₂Te₅ (GST). Thin films of GST can be deposited by employing either chemical vapor deposition (CVD) or atomic layer deposition (ALD) techniques. In both cases, the success of the layer deposition crucially depends on the proper choice of suitable molecular precursors. Previously reported processes mainly relied on simple alkoxides, alkyls, amides and halides of germanium, antimony, and tellurium. More sophisticated precursor design provided a number of promising new aziridinides and guanidinates.     

Effect of aluminium content on the coating structure and dross formation in the hot‐dip galvanizing process

Hot dipping of steel in aluminium–zinc baths of varying composition (5–90% Al) has been undertaken with the aim of elucidating the mechanism of coating formation. On the basis of these experiments, it has been possible to define a range of aluminium content over which there is a change from a normal galvanizing process to a typical aluminizing process. Alternatively, the coating structure and properties were markedly affected by the aluminium content of the dipping bath. The kinetics of such coatings acquires the character of the activation energy E_a. The effect of various silicon levels as an inhibitor to iron dissolution during hot dipping at different aluminium percentages was studied. The structure of dross formation in 55 wt.% Al–Zn was identified. The adverse effect of heavy accumulation of dross in the dipping pot on the coating structure also was shown. Copyright © 2003 John Wiley & Sons, Ltd.     

Towards Antimonene and 2D Antimony Telluride through Electrochemical Exfoliation

Two-dimensional (2D) layered antimony (Sb) and antimony telluride (Sb₂Te₃) are two valuable materials for optoelectronic devices and thermoelectric applications. Preparing high-quality sheets of these materials is the initial phase to promote their expected issues. Herein, micrometer-sized few-to-multilayered sheets of Sb and Sb₂Te₃ have been obtained by electrochemical exfoliation. The layered rhombohedral Sb was exfoliated in Na₂SO₄ and Li₂SO₄ electrolytes by anodic–cationic intercalation, and Sb₂Te₃ was exfoliated in Na₂SO₄. These findings are important contributions for the solution-based room-temperature electrochemical exfoliation, which is stable under glove-box-free conditions, to further improve the production of high-quality exfoliated sheets.     

Synthesis,Characterization, and Singlet Oxygen Sensitization by Antimony (III/V) Corrole Complexes

The synthesis, structural, spectroscopic characterization, and DFT/TD-DFT calculations of antimony corroles are reported herein. The studied complexes can be described as [(Corr)Sb^III] and [(Corr)(oxo)Sb^V]₂, where Corr is the trianion of corrole. All these complexes are diamagnetic in nature as is evident from sharp peaks with normal chemical shifts in the ¹H NMR spectra. Single crystal XRD analysis reveals that the antimony(V) corrole complex is the bis-μ-oxo-bridged dinuclear antimony(V). Both the tetra and hexa-coordinated [(Corr)Sb^III] and [(Corr)(oxo)Sb^V]₂ antimony complexes adopt domed-structure with weak d-π electron coupling. The Sb−O bond distances in the co-facial dimer of [(Corr)(oxo)Sb^V]₂ are 1.9802(16) Å (DFT: 2.0141 Å ) (for Sb1−O1), and 1.9639(17) Å (DFT: 1.9957 Å ) (for Sb2−O2) respectively. We observed that even though iodosobenzene is frequently used to oxidize [(Corr)Sb^III] species, the oxidation of [(Corr)Sb^III] is indeed very facile in nature and it even occurred in the air-equilibrated CHCl₃ solution while storing for few days. Excitation of these antimony (III/V) corrole complexes in DCM/MeOH (1 : 1) at 77 K results in red emission with maxima at 640–720 nm. The singlet oxygen production of [(Corr)(oxo)Sb^V]₂ has a quantum yield of 69 % and is two times higher than the analogous [(Corr)Sb^III] derivatives.     

Synthese et structure du sulfate double MSbF2SO4 (M = Rb,Cs)

The crystal structure of RbSbF₂SO₄ has been determined on a single crystal (R = 0.078 for 710 reflections). The structure shows sulfate anions distorted by the SOSb bonds. The antimony atom is from an SbF₂ unit. This antimony dihalogen is from the family of the $\text{1}\text{1}$ compounds which are in MX₃SbX₃ (M = Al, Ga, In) (X = Cl, Br) systems.     

Strain‐Engineered Modulation on the Electronic Properties of Phosphorous‐Doped ZnO

The modulation of strain on the electronic properties of ZnO:P is investigated by density functional theory calculations. The variation of formation energy (E^f) and band structure with strains ranging from ?0.1 to 0.1 are considered. Although both the conduction band minimum (CBM) and the valence band maximum of ZnO are antibonding states, the CBM is more sensitive to strain, reducing the band gap with an increase in strain. P‐substituted O (P_O) defects show poor p‐type conductivity due to a smaller E^f and lower lying acceptor levels as a consequence of lattice expansion. The E^f of P‐substituted Zn (P_Zn) defects decreases under tension, owing to the release of strong repulsive stress induced by excess electrons from P_Zn. The donor energy band of P_Zn broadens under tensile strain, which benefits n‐type conductivity. For Zn vacancies (V_Zn) and P_Zn–2V_Zn complexes, the distances between the O atoms around V_Zn are so large that repulsive and attractive interactions become weak, which results in an easy release of the strain. We herein present for the first time that the E^f values of V_Zn and P_Zn–2V_Zn complexes decrease under both tension and compression, or in the high‐pressure rock‐salt phase. Under a strain of 0.1 the P_Zn–2V_Zn complex shows the smallest E^f. Under ?0.07 strain the wurtzite/rock‐salt phase transition occurs and the direct band gap becomes an indirect one. The variation of band structures in the rock‐salt phase is similar to that in the wurtzite phase. Consequently, the p‐type conductivity of ZnO:P can be improved with an increase in solubility of P_Zn–2V_Zn or V_Zn defects.     

Chemical route for formation of intermetallic Zn4Sb3 phase

Synthesis of intermetallic zinc antimonide phases via low temperature solution route was investigated. Trial experiments were carried out under inert atmosphere at 70 °C using metallic Zn, SbCl₃ and NaBH₄ as reactants and tetrahydrofuran (THF), dimethylsulfoxide (DMSO) as organic media. Powder X-ray analysis confirmed the nucleation and growth of ZnSb phases in presence of excess Zn. SEM analysis revealed the existence of core-shell structure comprising of Zn core and Sb shell. Such particles get transformed into Zn₄Sb₃ crystalline phases upon thermal treatment at 300 °C/6 h in a silica tube closed under high secondary vacuum.     

Study on antimony oxide self-assembled inside HZSM-5

Sb/ZSM-5 was obtained by solid-state reaction with the mixture of Sb₂O₃ and zeolite HZSM-5 under a dry nitrogen flow at 773 K. Characterization of the treated zeolite was undertaken with XRD, ²⁷Al MAS NMR, BET, TGA and FT-IR. The results revealed that part of the antimony oxides migrated into the channels of zeolite, and decreased the Brönsted acid sites in Sb/ZSM-5 remarkably. The other part of antimony oxides together with the amorphous alumino-silicate in the products distributed on the external surface of zeolite ZSM-5 and modified it, while the framework of ZSM-5 in crystal phase was retained. The structure of occluded antimony oxide inside the channels of ZSM-5 was studied by XRD Rietveld method. The result showed that their structure can be described as a chain of non-perfect [Sb₅O₅(H₂O)₂]_n⁵ⁿ⁺, which is parallel to the straight channel of ZSM-5. There is about 0.6 [Sb₅O₅(H₂O)₂]⁵⁺ unit in every cell of the ZSM-5 on an average.     

Surface Reorganization on Electrochemically‐Induced Zn–Ni–Co Spinel Oxides for Enhanced Oxygen Electrocatalysis

Herein, we highlight redox‐inert Zn²⁺ in spinel‐type oxide (Zn_XNi_1?XCo₂O₄) to synergistically optimize physical pore structure and increase the formation of active species on the catalyst surface. The presence of Zn²⁺ segregation has been identified experimentally and theoretically under oxygen‐evolving condition, the newly formed V_Zn?O?Co allows more suitable binding interaction between the active center Co and the oxygenated species, resulting in superior ORR performance. Moreover, a liquid flow Zn–air battery is constituted employing the structurally optimized Zn_0.4Ni_0.6Co₂O₄ nanoparticles supported on N‐doped carbon nanotube (ZNCO/NCNTs) as an efficient air cathode, which presents remarkable power density (109.1 mW cm^?2), high open circuit potential (1.48 V vs. Zn), excellent durability, and high‐rate performance. This finding could elucidate the experimentally observed enhancement in the ORR activity of Zn_XNi_1?XCo₂O₄ oxides after the OER test.     

Die Kristallstrukturen von (DDI)2[Sb2F6O] und (DDI)2[Sb3F7O2] (DDI = 1, 3‐Diisopropyl‐4, 5‐dimethylimidazolium) — Ein Beitrag zur Hydrolyse von SbF3 [1]

The Crystal Structures of (DDI)₂[Sb₂F₆O] and (DDI)₂[Sb₃F₇O₂] (DDI = 1,3‐Diisopropyl‐4,5‐dimethylimidazolium) — a Contribution to the Hydrolysis of SbF₃ [1] The salts (DDI)₂[Sb₂F₆O] ( 2 ) and (DDI)₂[Sb₃F₇O₂] ( 3 ), (DDI = 1,3‐diisopropyl‐4,5‐dimethylimidazolium) are obtained by hydrolysis of C₁₁H₂₀N₂SbF₃ ( 1 ). The anion [Sb₂F₆O]^2? consists of two SbF₂ fragments linked by a symmetrical oxygen bridge and two unsymmetrical fluorine bridges to form a distored ψ‐octahedral coordination sphere at the antimony atoms. In [Sb₃F₇O₂]^2?, two SbF₂ units are linked by a symmetrical fluorine bridge, while the third antimony atom is connected with each SbF₂ fragment by a symmetrical oxygen and an unsymmetrical fluorine bridge. The antimony atoms adopt the centres of strongly distored ψ‐polyhedra.     

Sb10Se10]2+, a heteronuclear polycyclic polycation from a room-temperature ionic liquid

Reaction of antimony, selenium, and selenium(IV) chloride in the Lewis acidic ionic liquid [BMIM]Cl/AlCl₃ (BMIM: 1‐n‐butyl‐3‐methylimidazolium) at room temperature yielded air‐sensitive black block‐shaped crystals of [Sb₁₀Se₁₀][AlCl₄]₂. The triclinic unit cell (space group ${P\bar 1}Reaction of antimony, selenium, and selenium(IV) chloride in the Lewis acidic ionic liquid [BMIM]Cl/AlCl(3) (BMIM: 1-n-butyl-3-methylimidazolium) at room temperature yielded air-sensitive black block-shaped crystals of [Sb(10)Se(10)][AlCl(4)](2). The triclinic unit cell (space group P1, a=947.85(2), b=957.79(2), c=1166.31(3)?pm; α=103.622(1), β=110.318(1), γ=99.868(1)°; Z=1) contains the first mixed antimony/selenium polycation, [Sb(10)Se(10)](2+). The centrosymmetric polycyclic cation consists of two realgar-like [Sb(4)Se(4)] cages, which are connected through positively charged, three-bonded selenium atoms with a central [Sb(2)Se(2)] ring. Quantum chemical calculations predict semiconducting behavior of the compound and indicate primarily covalent bonding with varying ionic contribution within the [Sb(10)Se(10)](2+) polycation, while the interactions between the polycation and the [AlCl(4)](-) anions are predominantly ionic. The applicability of the Zintl concept to the chemical bonding in the heteronuclear polycation was evaluated by a thorough quantum chemical analysis.     

Structure and Properties of γ‐Brass‐Type Pt2Zn11—δ (0.2 < δ < 0.3)

The γ‐brass type phase Pt₂Zn_11—δ (0.2 < δ < 0.3) was prepared by reaction of the elements in evacuated silica ampoules. The structures of crystals grown in the presence of excess zinc or alternatively excess platinum were determined from single crystal X‐ray diffraction intensities and confirmed by Rietveld profile fits. Pt₂Zn_10.72(1) crystallizes in the space group I4¯3m, a = 908.55(4) pm, Z = 4. The structure refinement converged at R_F = 0.0302 for I_o > 2σ (I_o) for 293 symmetrically independent intensi ties and 19 variables. The structure consists of a 26 atom cluster which is comprised of four crystallographically distinct atoms. The atoms Zn(1), Pt(1), Zn(2) and Zn(3) form an inner tetrahedron IT, an outer tetrahedron OT, an octahedron OH, and a distorted cuboctahedron CO respectively. About 14 % of the Zn(1) sites are unoccupied. Pt₂Zn_10.73 melts at 1136(2) K. It is a moderate metallic conductor (ρ₂₉₈ = 0.2—0.9 mΩ cm) whose magnetic properties (χ_mol = —4.6 10^—10 to —5.4 10^—10 m³ mol^—1) are dominated by the core diamagnetism of its components.