Fe Sb Research Articles

Synthesis of Bi–Fe–Sb–O Pyrochlore Nanoparticles with Visible‐Light Photocatalytic Activity

AbstractA method has been developed for the preparation of Bi–Fe–Sb–O pyrochlore nanoparticles by microwave hydrothermal treatment. Experiments revealed that the preparation procedure for the precursors is an important factor that affects the phase composition of the product. The morphology of the pyrochlore particles was investigated by SEM, HRTEM, and selected‐area electron diffraction (SAED) methods. The samples consist of numerous spherical agglomerates from 100 to 200 nm formed from 20 nm mutually oriented nanocrystallites. A mechanism for the formation of the particles is proposed, and the magnetic and photocatalytic properties of the Bi–Fe–Sb–O pyrochlore nanocrystallites are reported.

Enthalpies of mixing in binary Fe–Sb, Ce–Fe and ternary Ce–Fe–Sb liquid alloys

Abstract The enthalpies of mixing in liquid alloys in the binary Fe–Sb, Ce–Fe and ternary Ce–Fe–Sb systems were determined over a wide range of composition by means of isoperibolic calorimetry in the temperature range 1600–1830 K. The minimum values of the integral enthalpy of mixing (ΔH min) were determined to be (−2.32 ± 0.22) kJ · mol−1 at x Sb = 0.5 in the Fe–Sb system, and (−0.97 ± 0.19) kJ · mol−1 at x Ce = 0.35 in the Ce–Fe system. The enthalpies of mixing in liquid ternary Ce–Fe–Sb alloys were found to increase smoothly from the binary boundary systems Ce–Fe and Fe–Sb towards the Ce–Sb system, reaching the minimum value of (−107.5 ± 3.6) kJ · mol−1 in the vicinity of the phase CeSb.

Effect of aqueous Fe(II) on Sb(V) sorption on soil and goethite

The effects of Fe(II) on the sorption and precipitation of Sb(V) on soils and goethite were investigated using batch experiments and X-ray photoelectron spectroscopy (XPS) in this study. The sorption capacity of Sb(V) were much higher in anoxic soil than oxic soil. Typically, dissolved Fe(II) concentration in anoxic soils decreased significantly with increasing Sb(V), which may be suggestive of Fe-Sb precipitation. The elevated concentrations of Fe(II) (1 mM) enhanced the sorption capacity of Sb(V) on goethite significantly. However, synchrotron radiation X-ray diffraction showed no new characteristic peak, indicating that this Fe-Sb precipitate might be poor crystallinity or amorphous. Moreover, Sb(III) was detected in anoxic soil, and the reduction of Sb(V) to Sb (III) improved the sorption capacity of Sb in anoxic soil because of the low solubility and migration of Sb(III). Nevertheless, Fe-Sb co-precipitation and Sb(V) reduction to Sb(III) might contribute simultaneously to the increased sorption capacity of Sb(V) on anoxic soils. This research could improve our current understanding of soil Sb chemistry in paddy and wetland soils.

Growth and characterization of insulating ferromagnetic semiconductor (Al,Fe)Sb

We investigate the crystal structure, transport, and magnetic properties of Fe-doped ferromagnetic semiconductor (Al1−x,Fex)Sb thin films up to x = 14% grown by molecular beam epitaxy. All the samples show p-type conduction at room temperature and insulating behavior at low temperature. The (Al1−x,Fex)Sb thin films with x ≤ 10% maintain the zinc blende crystal structure of the host material AlSb. The (Al1−x,Fex)Sb thin film with x = 10% shows intrinsic ferromagnetism with a Curie temperature (TC) of 40 K. In the (Al1−x,Fex)Sb thin film with x = 14%, a sudden drop of the hole mobility and TC was observed, which may be due to the microscopic phase separation. The observation of ferromagnetism in (Al,Fe)Sb paves the way to realize a spin-filtering tunnel barrier that is compatible with well-established III-V semiconductor devices.

On the segregation behavior of tin and antimony at grain boundaries of polycrystalline bcc iron

The study of the temperature dependence of tin and antimony segregation at grain boundaries of binary Fe–Sb and Fe–Sn polycrystalline alloys using Auger Electron Spectroscopy suggests that during the brittle intergranular fracture mainly the general grain boundaries are opened in the samples annealed at low temperatures which are more segregated than the special ones. On the contrary, the special grain boundaries are opened in the samples annealed at higher temperatures because – as a consequence of the enthalpy-entropy compensation effect – they are more enriched by the solute. The limiting temperature between these two states is the so-called compensation temperature. Therefore, the temperature dependence of the grain boundary segregation measured in polycrystals should be described by two sets of the thermodynamic parameters (i.e. segregation enthalpy and entropy): one of them correlating the segregation under the compensation temperature, the other one for the segregation at higher temperatures.

Effect of iron plaque on antimony uptake by rice (Oryza sativa L.)

Although iron (Fe) plaque has been shown to significantly affect the uptake of toxic antimony (Sb) by rice, knowledge about the influence of iron plaque on antimony (Sb) (amount, mechanisms, etc) is, however, limited. Here, the effect of Fe plaque on Sb(III) and Sb(V) (nominal oxidation states) uptake by rice (Oryza sativa L.) was investigated using hydroponic experiments and synchrotron-based techniques. The results showed that iron plaque immobilized Sb on the surface of rice roots. Although the binding capacity of iron plaque for Sb(III) was markedly greater than that for Sb(V), significantly more Sb(III) was taken up by roots and transported to shoots. In the presence of Fe plaque, Sb uptake into rice roots was significantly reduced, especially for Sb(III). However, this did not translate into decreasing Sb concentrations in rice shoots and even increased shoot Sb concentrations during high Fe–Sb(III) treatment.

Single spin channels in Fe-doped CoTiSb semiconductor

The Fe-based single atomic chains are designed in the semiconductive CoTiSb matrix by continuously substituting Fe for Ti, Ti–Sb or Co in [001] crystallographic direction. The electronic structures and magnetic properties of CoTiSb supercells with the Fe-based single atomic chains have been investigated using the first-principles calculations. We predict that the single atomic chains of Fe–Sb (achieved by substituting Fe for Ti) and Fe-vacancy (achieved by substituting Fe for Co) show a 100% spin polarization and form a very small single spin channel. The single atomic chains of Fe–Fe (achieved by substituting Fe for Ti and Sb) show a spin-gapless characteristic.

(Ga,Fe)Sb: A p-type ferromagnetic semiconductor

A p-type ferromagnetic semiconductor (Ga1−x,Fex)Sb (x = 3.9%–13.7%) has been grown by low-temperature molecular beam epitaxy (MBE) on GaAs(001) substrates. Reflection high energy electron diffraction patterns during the MBE growth and X-ray diffraction spectra indicate that (Ga,Fe)Sb layers have the zinc-blende crystal structure without any other crystallographic phase of precipitates. Magnetic circular dichroism (MCD) spectroscopy characterizations indicate that (Ga,Fe)Sb has the zinc-blende band structure with spin-splitting induced by s,p-d exchange interactions. The magnetic field dependence of the MCD intensity and anomalous Hall resistance of (Ga,Fe)Sb show clear hysteresis, demonstrating the presence of ferromagnetic order. The Curie temperature (TC) increases with increasing x and reaches 140 K at x = 13.7%. The crystal structure analyses, magneto-transport, and magneto-optical properties indicate that (Ga,Fe)Sb is an intrinsic ferromagnetic semiconductor.

Interaction of exogenous refractory nanophases with tin dissolved in liquid iron

The heterophase interaction of Al2O3 refractory nanoparticles with a surfactant impurity (antimony) in the Fe–Sb (0.095 wt %)–O (0.008 wt %) system is studied. It is shown that the introduction of 0.06–0.18 wt % Al2O3 nanoparticles (25–83 nm) into a melt during isothermal holding for up to 1200 s leads to a decrease in the antimony content: the maximum degree of antimony removal is 26 rel %. The sessile drop method is used to investigate the surface tension and the density of Fe, Fe–Sb, and Fe–Sb–Al2O3 melts. The polytherms of the surface tension of these melts have a linear character, the removal of antimony from the Fe–Sb–Al2O3 melts depends on the time of melting in a vacuum induction furnace, and the experimental results obtained reveal the kinetic laws of the structure formation in the surface layers of the melts. The determined melt densities demonstrate that the introduction of antimony into the Fe–O melt causes an increase in its compression by 47 rel %. The structure of the Fe–Sb–O melt after the introduction of Al2O3 nanoparticles depends on the time of melting in a vacuum induction furnace.

Thermodynamic assessment of the Co–Fe–Sb system

The Co–Fe–Sb ternary system is critically assessed by CALPHAD (CALculation of PHAse Diagram) technique in the present work. The NiAs-type structure phase β-(Co,Fe)Sb with a wide non-stoichiometric range is described by three sublattices, (Sb)1/3(Co,Fe,Va)1/3 (Co,Fe,Va)1/3, following the extension of the sublattices of the phases β(CoSb) and β(FeSb) in the related binaries. The intermetallic compounds ζ(Co,Fe)Sb2 and η(Co,Fe)Sb3 are treated as linear stoichiometric compounds. The liquid, γ(A1)-Fcc_A1, α(A2)-Bcc_A2 and ε(A3)-Hcp_A3 phases are assumed to be substitutional solutions. The Rhombo_A7 phase is considered as the pure Sb phase. The order/disorder transformation between α(A2)-Bcc_A2 and α′(B2)-Bcc_B2 phases is described by a two-sublattice model (Co,Fe,Sb)0.5(Co,Fe,Sb)0.5. A set of self-consistent thermodynamic parameters of the Co–Fe–Sb system is obtained to fit satisfactorily a large amount of experimental data from literature. In the mean while, the Fe–Sb binary system is re-optimized critically.

Significant ZT enhancement in p-type Ti(Co,Fe)Sb–InSb nanocomposites via a synergistic high-mobility electron injection, energy-filtering and boundary-scattering approach

It has been demonstrated that InSb nanoinclusions, which are formed in situ, can simultaneously improve all three individual thermoelectric properties of the n-type half-Heusler compound (Ti,Zr,Hf)(Co,Ni)Sb (Xie WJ, He J, Zhu S, Su XL, Wang SY, Holgate T, et al. Acta Mater 2010;58:4795). In the present work, the same approach is adopted to the p-type half-Heusler compound Ti(Co,Fe)Sb. The results of resistivity, Seebeck coefficient, thermal conductivity and Hall coefficient measurements indicate that the combined high-mobility electron injection, low energy electron filtering and boundary scattering, again, lead to a simultaneous improvement in all three individual thermoelectric properties: enhanced Seebeck coefficient and electrical conductivity as well as reduced lattice thermal conductivity. A figure of merit of ZT≈0.33 was attained at 900K for the sample containing 1.0at.% InSb nanoinclusions, a ∼450% improvement over the nanoinclusion-free sample. This represents a rare case that the same nanostructuring approach works successfully for both p-type and n-type thermoelectric materials of the same class, hence pointing to a promising materials design route for higher-performance half-Heusler materials in the future and hopefully will realize similar improvement in thermoelectric devices based on such half-Heusler alloys.

Electronic Griffiths Phase in the Te-Doped SemiconductorFeSb2

We report on the emergence of an electronic Griffiths phase in the doped semiconductor FeSb(2), predicted for disordered insulators with random localized moments in the vicinity of a metal-insulator transition. Magnetic, transport, and thermodynamic measurements of Fe(Sb(1-x)Te(x))(2) single crystals show signatures of disorder-induced non-Fermi liquid behavior and a Wilson ratio expected for strong electronic correlations. The electronic Griffiths phase states are found on the metallic boundary between the insulating state (x = 0) and a long-range albeit weak magnetic order (x ≥ 0.075).

Discovery of Spin Glass Behavior in Ln2Fe4Sb5 (Ln = La–Nd and Sm)

Single crystals of Ln(2)Fe(4)Sb(5) (Ln = La-Nd and Sm) were grown from an inert Bi flux. Measurements of the single crystal X-ray diffraction revealed that these compounds crystallize in the tetragonal space group I4/mmm with lattice parameters of a ≈ 4 Å, c ≈ 26 Å, V ≈ 500 Å(3), and Z = 2. This crystal structure consists of alternating LnSb(8) square antiprisms and Fe-sublattices composed of nearly equilateral triangles of bonded Fe atoms. These compounds are metallic and display spin glass behavior, which originates from the magnetic interactions within the Fe-sublattice. Specific heat measurements are void of any sharp features that can be interpreted as contributions from phase transitions as is typical for spin glass systems. A large, approximately linear in temperature, contribution to the specific heat of La(2)Fe(4)Sb(5) is observed at low temperatures that we interpret as having a magnetic origin. Herein, we report the synthesis, structure, and physical properties of Ln(2)Fe(4)Sb(5) (Ln = La-Nd and Sm).

Effect of Ce and Sb on Primary Graphite Growth in Cast Irons

It is well-known that if certain trace elements are present in cast iron melts the morphology of the graphite precipitates can be altered. In order to understand the effect of doping elements on primary growth of graphite, pure Fe–Sb alloys were prepared by induction melting. They were then placed in graphite crucibles and heated to a temperature above the Fe–C eutectic so that the charge became saturated in carbon and melted. To obtain Fe–Ce alloys, metallic Ce was added at the bottom of a graphite crucible and covered with iron, and then heated as for the Fe–Sb charge. In both cases, the melt was then cooled and held slightly above the eutectic temperature so that primary graphite crystals, which had nucleated on the crucible walls and then detached from it, could grow freely in the melt. The influence of the added elements on graphite growth was revealed by the change in the shape and distribution of the crystals compared to those obtained in similar experiments carried out with pure Fe. The experiments were made in air and vacuum so as to point out possible interactions between the elements present in the melt and oxygen.

ChemInform Abstract: Interaction of Vanadium with Iron and Antimony at 870 and 1070 K.

AbstractThe isothermal sections of the V—Fe—Sb ternary system at 870 and 1070 K are constructed.

Interaction of Vanadium with Iron and Antimony at 870 and 1070 K

AbstractThe isothermal sections of the phase diagram of the V–Fe–Sb ternary system have been constructed at 870 and 1070 K by means of X‐ray and electron‐probe microanalyzer (EPMA) analyses over the whole concentration range. The existence of the one ternary phase, VFeSb, with MgAgAs‐ and Ni2In‐type structures was observed at 870 and 1070 K, respectively. The solid solution formed based on the binary Fe2–xSb (Ni2In‐type) compound reaches up to 12 at.‐% of V at 870 K and 40 at.‐% at 1070 K, respectively. Differential scanning calorimetry (DSC) analysis, magnetic susceptibility measurements, and electronic structure calculations showed the absence of a VFeSb polymorph phase transition and indicate that the hexagonal phase is part of the VyFe2–xSb solid solution.

MINERALOGY OF WEATHERING PRODUCTS OF Fe-As-Sb MINE WASTES AND SOILS AT SEVERAL Sb DEPOSITS IN SLOVAKIA

We present the results of an investigation of tailing ponds and contaminated soils at five antimony deposits in Slovakia, Pezinok, Dubrava, Medzibrod, Cucma, and Poproc. With the exception of Poproc, all primary mineralization contained abundant carbonates; the sites studied are examples of neutral mine drainage. The Fe–As–Sb-rich products of weathering were studied in 250 samples of tailings and also in contaminated soils for comparison. They were examined by means of 2500 electron-microprobe (EMP) and 500 micro-X-ray diffraction (μ-XRD) analyses. The primary focus of this work is the incorporation of the metalloids Sb and As into (poorly) crystalline authigenic phases, not their association with mineral surfaces. The EMP analyses define a densely populated field in a triangular Fe–Sb–As diagram. Compositions along the entire Fe–Sb edge are common; many of them lie near the Fe apex, with an (As + Sb)/(Fe + As + Sb) value not exceeding 0.3. Oxidation-induced rims on arsenopyrite mostly consists of X-ray-amorphous hydrous ferric oxides (HFO) with average As and Sb contents equal to 13.9 and 5.69 wt%, respectively. The rims developed on pyrite mostly consist of goethite or a mixture of goethite and HFO, which acts as effective sorbents of As, Sb, Ca, Si and Cu. Among the grains without relics of primary sulfides, HFO with variable concentrations of As, Sb is common. The most common secondary mineral at all sites is goethite, with average As and Sb contents of 1.33 and 3.93 wt%, respectively. A very common Sb-bearing secondary phase at all studied localities is tripuhyite (FeSbO 4 ). Calcium antimonates with the pyrochlore structure are typical of environments rich in Ca. Simple secondary Sb oxides such as cervantite and senarmontite were observed each in only one soil sample. Beudantite was identified in a few samples with a higher Pb content. In one sample, a porous secondary oxide rich in Pb and As was identified as clinomimetite.

Geochemistry of arsenic and metals in stored tailings of a Co–Ni arsenide-ore, Khovu-Aksy area, Russia

Abstract Interest in the redistribution of As-bearing species during long-term storage of hydrometallurgical tailings is motivated partly by the need to prevent As from being released into the environment. The speciation of As in mine wastes from the Tuva Cobalt Plant (Khovu-Aksy mine site, Tuva Republic, Russia) has been studied using mineralogical techniques, and chemical analyses of solids (tailings, soils, vegetation) and solutions (recovered pore waters, leach solutions). Ore at the plant was processed by hot autoclave leaching with an ammoniacal carbonate solution followed by treatment with CO2(gas) and caustic magnesite, MgO. Pronounced differences in element concentrations were measured in the five separate tailings ponds and one trench that were filled sequentially during operation of the plant. The concentration of each element was relatively uniform within each pond but the correlations among solid-phase Co, Ni, Zn and Cu gradually decrease from the most recent to oldest ponds as does the correlation between solid-phase As, Ag, Cd and Pb. In the oldest ponds, significant correlations are present between solid-phase Fe–As, Fe–Sb and Fe–Zn. High carbonate content in the ores and leaching reagents control the pH of the pore waters (pH = 7.27–9.10) where the major cation is Ca2+, followed by NH 4 + and Mg2+. Concentrations of As in pore solutions reach up to 140 mg L−1, and average 15 mg L−1. The high pore-water As concentrations are a consequence of instability of the processing residues, which include Mg(NH4)AsO4⋅nH2O and Mg3(AsO4)2⋅nH2O. The concentrations of Zn, Cu and As in pore waters increase from the youngest pond to the oldest storage impoundment (trench), which is evidence of the increase in element mobility with time. In contrast to the metals, As is preferentially sorbed to Fe oxides formed in the tailings. Aerosol transport of dust from the dry ponds has produced anomalies of As and metals in the surrounding area with As in the most polluted soils reaching up to 540 ppm. Moreover, vegetation growing on the surface of the disposal ponds absorbs solutes from the soil.

Arsenic and antimony contamination of waters, stream sediments and soils in the vicinity of abandoned antimony mines in the Western Carpathians, Slovakia

Abstract Environmental contamination with As and Sb caused by past mining activities at Sb mines is a significant problem in Slovakia. This study is focused on the environmental effects of the 5 abandoned Sb mines on water, stream sediment and soil since the mines are situated in the close vicinity of residential areas. Samples of mine wastes, various types of waters, stream sediments, soils, and leachates of the mine wastes, stream sediments and selected soils were analyzed for As and Sb to evaluate their geochemical dispersion from the mines. Mine wastes collected at the mine sites contained up to 5166 mg/kg As and 9861 mg/kg Sb. Arsenic in mine wastes was associated mostly with Fe oxides, whereas Sb was present frequently in the form of individual Sb, Sb(Fe) and Fe(Sb) oxides. Waters of different types such as groundwater, surface waters and mine waters, all contained elevated concentrations of As and Sb, reaching up to 2150 μg/L As and 9300 μg/L Sb, and had circum-neutral pH values because of the buffering capacity of abundant Ca- and Mg-carbonates. The concentrations of Sb in several household wells are a cause for concern, exceeding the Sb drinking water limit of 5 μg/L by as much as 25 times. Some attenuation of the As and Sb concentrations in mine and impoundment waters was expected because of the deposition of metalloids onto hydrous ferric oxides built up below adit entrances and impoundment discharges. These HFOs contained >20 wt.% As and 1.5 wt.% Sb. Stream sediments and soils have also been contaminated by As and Sb with the peak concentrations generally found near open adits and mine wastes. In addition to the discharged waters from open adits, the significant source of As and Sb contamination are waste-rock dumps and tailings impoundments. Leachates from mine wastes contained as much as 8400 μg/L As and 4060 μg/L Sb, suggesting that the mine wastes would have a great potential to contaminate the downstream environment. Moreover, the results of water leaching tests showed that Sb was released from the solids more efficiently than As under oxidizing conditions. This might partly explain the predominance of Sb over As in most water samples.

The hunt for LaFeSbO: Synthesis of La2SbO2 and a case of mistaken identity

The phase La2SbO2 has been identified and characterized in the course of our efforts to realize LaFeSbO, a composition of great interest to the superconductor community. The compound La2SbO2 is a tetragonal layered oxypnictide containing La2O2 layers similar to LaMPnO compositions (where M=transition metal, Pn=pnictide) separated by pnictide anion layers. In order to better understand why LaFeSbO has remained elusive, density functional theory calculations have been used to determine the ground state heats of formation for LaFeSbO, La2SbO2, and other competing phases within the La–Fe–Sb–O system, as well as the phonon spectrum for LaFeSbO. These efforts suggest that LaFeSbO is a potentially metastable composition.