Sb Phase Research Articles

Unraveling the Highly Complex Nature of Antimony on Pt(111)

AbstractUnderstanding the growth behavior of group‐V elements on metal surfaces provides valuable information that can shed light on the feasibility of tailoring atomically thin monoelemental 2D polymorphs composed of pnictogens on these metallic substrates. Here, by combining scanning tunneling microscopy (STM), low energy electron diffraction and Auger electron spectroscopy measurements under ultra‐high vacuum conditions, a wide variety of Sb reconstructions on single‐crystal Pt(111) are identified and characterized. At Sb coverage of ≈0.2 ML, STM data are compatible with a scenario in which Sb atoms are randomly embedded into the topmost layer of Pt, in a substitutional configuration and without establishing a periodic structure. This disorder is robust against thermal annealing and quenching. Increasing the surface coverage and whether or not the sample is annealed, different well‐ordered Sb phases are formed. The Sb structures synthesized at room temperature without any heating process are best interpreted as surface alloys that involve only the first atomic layer. In contrast, experimental evidence points towards the development of multilayer alloy phases for the annealed samples.

Thermodynamic calculation of S−Sb system and Cu−S−Sb system

Sb2S3 and CuSbS2 have been proposed as alternative earth-abundant absorber materials for thin-film solar cells. However, no thermodynamic study of the S−Sb binary system and the Cu−S−Sb ternary system were investigated. In this paper, The S−Sb system and the Cu−S−Sb system are calculated utilizing the so-called CALPHAD (CALculation of PHAse Diagrams) technique. Using TEM-EDS and XRD, Cu0.9Sb1S2 is experimentally confirmed at the Cu1Sb1S2 and Sb2S3 two-phases region in the isothermal section at 673 K of the Cu−S−Sb ternary system. Given the asymmetric shape and miscibility gap of the liquidus in the S−Sb phase diagram, the associate solution model for the liquid phase is adopted. The solution phases (liquid, bcc, fcc) are treated with the Redlich–Kister equation. The compounds S3Sb2, Cu3SbS3, Cu12Sb4S13, CuSbS2, and Cu3SbS4 are described as a stoichiometric compound. A set of self-consistent thermodynamic parameters of the S−Sb binary system and the Cu−S−Sb ternary system are obtained. The calculated results are in good agreement with the experimental data. This study provides a set of reliable thermodynamic parameters to the Cu−Sb−S thermodynamic database, and a cost-effective tool to design material synthesis experiments and manufacturing processes.

Performance Improvement of Sb Phase Change Thin Film by Y Doping

Yttrium-doped Sb phase change thin films were prepared by magnetron sputtering and the in-situ resistance temperature measurement system was used to study the process of phase change thin films. With the addition of yttrium atoms, the crystallization temperature of Sb thin film increases, indicating improvement of their thermal stability and data retention ability. Furthermore, yttrium-doped Sb thin films have higher crystalline and amorphous resistance, which is conducive to the phase transition by Joule heating under electric pulse current. The optical band gap energy increases after yttrium doping, which means lower conductivity and higher conduction activation energy. X-ray diffraction shows that the doping of yttrium atoms can inhibit the grain growth and refine the grain size. X-ray photoelectron spectroscopy was used to examine the chemical state of the element, indicating the formation of a new Y-Sb bond, which verifies the improvement of stability. According to atomic force microscopy images, the yttrium-doped Sb material exhibits a surface morphology with less roughness, implying better interfacial properties and reliability. In general, yttrium-doped Sb thin films have better development in the application of phase change memory.

Microstructure and electrical performance of Ce0.3Ni1.5Co2.5Sb12 skutterudite from bulk to film

The skutterudite CoSb3 has been widely concerned, as one of the most studied candidate materials for thermoelectric applications. Here, n-type bulk skutterudite Ce0.3Ni1.5Co2.5Sb12 was successfully prepared under TGZM effect and its thin film deposited by PLD on single crystal Si substrate, to further understand the effect of microstructure and the electrical transport mechanism on the thermoelectric properties from bulk to thin film. It is found that two phases of Sb and CoSb3 coexist in bulk sample, while abundant nano-granular structures with well-crystallized CoSb3 and little of CeSb generate in the film. As a result, the maximum value of S and PF reach −250 μV/K and 5275 μW/(mK2) for film sample at 673 K. The PF value of film is four times higher than that of the bulk sample. This provides a novel avenue to increase the thermoelectric properties of skutterudite.

Crystallization mechanism and switching behavior of In–S–Sb phase change thin films

The crystallization mechanism of In2S3-doped Sb thin films is studied in detail to verify the potential application in phase change memory. Here, we observe directly that two different crystallization behaviors can exist in In–S–Sb thin layers by using aberration-corrected scanning transmission electron microscopy. The difference between Sb53.3(In2S3)46.7 and Sb30.9(In2S3)69.1 materials is induced by phase separation. The crystallization mechanism of the Sb53.3(In2S3)46.7 material is related to the formation of the nanocomposite structure with continuous precipitation of Sb nanocrystals. The crystallization characteristic of the Sb30.9(In2S3)69.1 material originates from the diffusion-driven In–S/In–S–Sb interface formation that acts as a “n–p” heterojunction, thereby resulting in the “depletion layer effect” and decreasing the carrier density to 7.42 × 1020 cm−3 at 280 °C. Sb30.9(In2S3)69.1 shows good bipolar-type resistance switching characteristics as the conventional Ge2Sb2Te5. This work provides clear experimental evidence to deepen the understanding of the crystallization mechanism for indium chalcogenides alloyed with Sb films, contributing to the improved control of the phase change behavior to establish high-performance multi-level nonvolatile memory and neuromorphic synaptic systems.

Chapmanite [Fe<sub>2</sub>Sb(Si<sub>2</sub>O<sub>5</sub>)O<sub>3</sub>(OH)]: thermodynamic properties and formation in low-temperature environments

Abstract. In this work, we have determined or evaluated thermodynamic properties of synthetic Sb2O5, MgSb2O6 (analogue of the mineral byströmite), Mg[Sb(OH)6]2⋅6H2O (brandholzite), and natural chapmanite [(Fe1.88Al0.12)Sb(Si2O5)O3(OH)]. Enthalpies of reactions, including formation enthalpies, were evaluated using reference compounds Sb, Sb2O3, Sb2O5, and other phases, with high-temperature oxide melt solution calorimetry in lead borate and sodium molybdate solvents. Heat capacity and entropy were determined by relaxation and differential scanning calorimetry. The best set of ΔfHo (kJ mol−1) and So (J mol−1 K−1) is byströmite -1733.0±3.6, 139.3±1.0; brandholzite -5243.1±3.6, 571.0±4.0; and chapmanite -3164.9±4.7, 305.1±2.1. The data for chapmanite give ΔfGo of -2973.6±4.7 kJ mol−1 and log⁡K=-17.10 for the dissolution reaction (Fe1.88Al0.12)Sb(Si2O5)O3(OH) + 6H+→ 1.88Fe3+ + 0.12Al3+ + 2SiO20 + Sb(OH)30 + 2H2O. Analysis of the data showed that chapmanite is finely balanced in terms of its stability with schafarzikite (FeSb2O4) and tripuhyite (FeSbO4) under a specific, narrow range of conditions when both aqueous Fe(III) and Sb(III) are abundant. In such a model, chapmanite is metastable by a narrow margin but could be stabilized by high SiO20(aq) activities. Natural assemblages of chapmanite commonly contain abundant amorphous silica, suggesting that this mechanism may be indeed responsible for the formation of chapmanite. Chapmanite probably forms during low-temperature hydrothermal overprint of pre-existing Sb ores under moderately reducing conditions; the slightly elevated temperatures may help to overcome the kinetic barrier for its crystallization. During weathering, sheet silicates may adsorb Sb3+ in tridentate hexanuclear fashion, thus exposing their chapmanite-like surfaces to the surrounding aqueous environment. Formation of chapmanite, as many other sheet silicates, under ambient conditions, is unlikely.

(Invited) Two-Dimensional Pnictogens: Van Der Waals Growth, Stability, and Phase Transformation

Pnictogens (P, As, Sb, Bi) emerged as a new class of elemental 2D materials displaying a wide range of electronic and topological properties. With their ns2 np3 valence electronic configuration and sp3 hybridization, group VA elements are the only elemental group which forms vdW and quasi-vdW structures throughout the entire group, thus providing a rich allotropic system. Light group VA elements crystallize in the semiconducting orthorhombic layered phase (A17) and heavier group VA elements prefer the semi-metallic rhombohedral layered phase (A7). At nanoscale thicknesses, group VA materials undergo various electronic phase transitions. For instance, A17 P – black phosphorus – is a high mobility 2D semiconductor with a thickness-dependent direct band gap gradually varying between 0.3-2 eV as its thickness decreases from bulk to single layer. Similarly, A7 Sb is predicted to exhibit topological semimetal, topological insulator, quantum spin Hall and indirect band gap semiconductor phases at thicknesses between 1 and 22 layers.Despite their highly attractive scientific and technological potential, 2D materials remain scarcely implemented in scalable devices and technologies due to several challenges including among others the lack of large-area and uniform synthesis methods. In fact, many 2D materials exist only in the realm of theoretical predictions and most 2D materials can only be produced by mechanical or chemical exfoliation from bulk crystals, yielding 2D flakes with limited dimensions and poor thickness control. Developing epitaxial growth methods is therefore a crucial step to enable the integration of 2D materials in emerging technologies. With this perspective, this presentation will address the development of the molecular beam epitaxy (MBE) growth of group VA 2D materials on semiconducting and vdW substrates. Furthermore, thermal, ambient and phase stability of these emerging 2D materials is studied using in situ low-energy electron microscopy, transmission electron microscopy, x-ray photoelectron emission microscopy, and ab initio calculations. MBE growth of 2D-Sb and 2D-AsSb is demonstrated on Ge(111) and graphene. Real-time LEEM measurements of the growth dynamics combined with in situ STM allow to determine the nucleation and growth mechanisms on semiconductor and vdW substrates. Subtle behavior during growth or thermal annealing was revealed based on these in situ studies including the metastability and layered-to-layered phase transformation mechanisms of A17 2D-Sb, which was previously considered as an unstable Sb phase. These results provide a deeper understanding of vdW growth of group VA 2D materials and layered-to-layered phase transformation mechanisms.

Resolving few-layer antimonene/graphene heterostructures

Two-dimensional (2D) antimony (Sb, “antimonene”) is of interest in electronics and batteries. Sb however exhibits a large allotropic structural diversity, which is also influenced by its support. Thus, Sb heterostructure formation is key in 2D Sb integration. Particularly, 2D Sb/graphene interfaces are important. We thus study here few-layered 2D Sb/graphene heterostructures with atomic resolution (scanning) transmission electron microscopy. We find two Sb morphologies to coexist: first, a 2D morphology of layered β-Sb with β-Sb(001)||graphene(001) texture. Second, one-dimensional Sb nanowires which can be matched to β-Sb[2-21]⊥graphene(001) and are closely related to cubic Sb(001)||graphene(001). Importantly, both Sb morphologies show rotational van-der-Waals epitaxy with graphene. Both are resilient against oxidation, although superficial Sb-oxide formation merits consideration, including epitaxial Sb2O3(111)/β-Sb(001) heterostructures. Exact Sb growth behavior depends on processing and substrate properties including, notably, the support underneath the graphene. Our work elucidates the rich phase and epitaxy landscape in 2D Sb and 2D Sb/graphene heterostructures.

Antimony allotropes fabricated on oxide layer of Cu(111)

Monolayer and few layer antimony allotropes fabricated on oxide layers are essential for practical applications in fields of solar cells, electronic and photonic devices. Here the antimony structural phases are systemically studied on corrugated copper oxide of Cu(111) by atomically-resolved scanning tunneling microscopy (STM). We find that initial deposition of Sb atoms causes the structural changes of the underlying oxide layer and sequentially gives rise to the formation of flat (√7 × √7)-Sb and buckled antimonene phases. Finally, a nanoring-like antimony configuration is observed with triangle-shaped atomic arrays closely packing and shows high stabilities for oxygen exposure. The (√7 × √7) phase exhibits the metallic property with energetically continuous electronic states existing near Fermi level. For the antimonene and nanoring phases, band gap signatures are observed, implying the semiconducting features. Our results provide a method for fabricating stable elemental allotropes on oxide surfaces.

Phase formation and thermoelectric properties of Zn1+Sb binary system

The phase formation and thermoelectric (TE) properties in the central region of the Zn−Sb phase diagram were analyzed through synthesizing a series of Zn1+xSb (x=0, 0.05, 0.1, 0.15, 0.25, 0.3) materials by reacting Zn and Sb powders below the solidus line of the Zn−Sb binary phase diagram followed by furnace cooling. In this process, the nonstoichiometric powder blend crystallized in a combination of ZnSb and β-Zn4Sb3 phases. Then, the materials were ground and hot pressed to form dense ZnSb/β-Zn4Sb3 composites. No traces of Sb and Zn elements or other phases were revealed by X-ray diffraction, high resolution transmission electron microscopy and electron energy loss spectroscopy analyses. The thermoelectric properties of all materials could be rationalized as a combination of the thermoelectric behavior of ZnSb and β-Zn4Sb3 phases, which were dominated by the main phase in each sample. Zn1.3Sb composite exhibited the best thermoelectric performance. It was also found that Ge doping substantially increased the Seebeck coefficient of Zn1.3Sb and led to significantly higher power factor, up to 1.51 mW·m−1·K−2 at 540 K. Overall, an exceptional and stable TE figure of merit (ZT) of 1.17 at 650 K was obtained for Zn1.28Ge0.02Sb.

Alloy decomposition under pressure: Bi–Sb incommensurate phase as a case study

The high-pressure phase behavior of the Bi–Sb system was investigated experimentally and modeled thermodynamically to study the effect of the transition to the incommensurate Bi-III type structure, which is adopted by the high-pressure phases Bi-III and Sb-II of the pure elements. The thermodynamic model of the Bi–Sb phase diagram including the effect of pressure in the isomorphous regime was extended to include solid–solid phase transitions of the pure elements. Consequently, the alloy phase diagram was found to transform to the eutectic form with pressure and is predicted here in the pressure range of 3–6 GPa. The alloy was found to transform from the ambient, rhombohedral A7 structure to the incommensurate phase. The transformation occurred at intermediate pressures between those observed in elemental Bi and Sb. The region of thermodynamic stability was determined by calculating the spinodal curves. To verify these predictions, the structure of a Sb-rich alloy was determined as a function of pressure by X-ray diffraction measurements in a diamond anvil cell, demonstrating the transition from A7 to the incommensurate Sb-II-like structure. It was found that the decomposition of the alloy under pressure is determined by the thermodynamic instability located at the spinodal curve. In contrast, alloy compositions located in the metastable region between the binodal phase line and the spinodal curve did not decompose under pressure, thus indicating a new region of phase space to be explored in high-pressure studies of alloys.

Identification of Antimony Precipitates in Sb-Bearing C-Mn Steel

The structure and two successive heterogeneous precipitation behaviors of Sb precipitates in ultrahigh Sb bearing steel were investigated. MnS is an effective heterogeneous nucleation core of Sb-precipitated phase in Sb bearing steel. The inclusion of Ti-modified MnS can increase the ratio of the precipitation core of the steel. The specific structure type of Sb-precipitated phase in steel is FeSb phase.

Simulation of Fe-Ti-Sb Thernary Phase Diagram at Temperatures above 900 K

Heusler alloys have been considered as one of the most promising thermoelectric materials for electrical power generation in a temperature range of 500–800 °C. Establishment of phase diagrams allows one to predict formation, equilibria, and stability of phases in of these ternary alloys. In this work we report on the simulation and investigation of phase diagram and phase equilibria in ternary Ti-Fe-Sb system which is of considerable interest for thermoelectric applications. The simulation was carried out using the CALPHAD method in Pandat software. The existence of the thermoelectric Heusler TiFe1.5Sb phase was revealed in a temperature range from 970 to 1070 K. The equilibria between TiFe1.5Sb and other phases were determined. The entropy of formation was calculated for the phases existing at 970, 1020 and 1070 K using a fitting approach. A narrow equilibrium region containing pure body centered cubic Fe and TiFe1.5Sb was found.

Characterizing armchaired and zigzagged phases: Antimony on oxide layer of Cu(110)

Antimony nanostructures fabricated on metal oxide layers are essential for practical applications in fields of solar cells, electronic and photonic devices. Here the antimony phases were systemically studied on the copper oxide of Cu(110). By high-resolution scanning tunneling microscopy (STM), we revealed that a wrinkled antimony phase was formed on the CuO surface regardless of the initial oxide structure. It exhibited an armchair-like configuration making up of protruded and dipped Sb atoms as confirmed by STM and density functional theory calculations. Further Sb deposition caused the armchair-like phase distorting and subsequently gave rise to formation of a c(2 × 2)-Sb phase. Finally, another kind of wrinkled phase was successfully fabricated. It consisted of two zigzagged antimony chains with protruded and dipped Sb atoms alternately distributing. By analysis of the atomically-resolved STM topographies, several kinds of dislocations have been observed and the corresponding geometric models are addressed. The armchair and zigzag phases both exhibited high stabilities for oxygen exposure. Conductance measurements imply that each phase interacts with the underlying layer. Our results might provide a way for fabricating stable ultrathin materials with a well-defined edge structure on oxide surfaces.

Interfacial heat transfer and microstructural analyses of a Bi- 5% Sb lead-free alloy solidified against Cu, Ni and low-C steel substrates

Bi-Sb system alloys demonstrate high corrosion resistance and good wettability, becoming promising for use as lead-free solder alloys. The simplicity of the phase diagram is also a characteristic of this system, which is isomorphous forming the (Bi,Sb) phase. While extensive research has been performed on heat flow in couples of microelectronics surfaces with eutectic and peritectic alloys, literature regarding the issues of interfacial heat transfer between isomorphous alloys and microelectronics substrates is nonexistent. In this regard, the present research work demonstrates not only the application of a numerical mathematical model for thermal interface conductance but also wetting and interfacial reaction layer results in the formation of phases for the Bi- 5 wt% Sb alloy in different substrate materials. After carrying out the mentioned analyzes in three different conditions, Bi-Sb/copper, Bi-Sb/nickel and Bi-Sb/low-C steel, the wetting angle is shown not to be the predominant factor in controlling the interfacial heat transfer. Instead, the phases forming the interfacial layer from each of the tested substrates have a role in the heat transfer coefficients (h). In the case of the steel substrate, there is no layer formation, which allows greater contact conductance, whereas Bi-Sb/copper and Bi-Sb/nickel couples generate smaller h, being reasonably similar to each other.

The Removal of Platinum Group Metals, Cs, Se, and Te from Nuclear Waste Glass Using Liquid Sb Extraction and Phase Separation Methods.

Recovery of platinum group metals (PGMs: Pd, Ru, Rh), Cs, Se, and Te from molten borosilicate glass containing simulated high level radwaste through the combination of liquid metal extraction and phase separation method under reductive heat-treatment was studied. In this process, the PGMs were extracted in recovered liquid metal phase, where Sb and Bi metals were used as the collecting metals. Meanwhile, Cs, Se, and Te were enriched in the phase separated potassium-rich materials on glass surface, which were extracted by water. The type of liquid metals had profound influence on the extraction behaviors of PGMs and other fission products from the glass melt. As a result, except the near extraction efficiency of Pd, Sb showed higher affinity for Ru and Rh than Bi metal. The higher phase separation efficiency of potassium-rich materials led to the higher extraction efficiencies of Cs, Se, and Te in liquid Sb extraction than Bi. Among the examined conditions, using liquid Sb extraction, the Pd, Ru, and Rh extraction efficiencies were 78.6%, 62.1% and 100% in liquid Sb metal phase, and 93.76% of Cs, 60.4% of Se, and 23.65% of Te in leachate were obtained.

Ag–Sb/Cu interfacial reactions and Ag–Cu–Sb phase equilibria

Ag–Sb alloys are promising materials in joining applications and Cu is frequently encountered in electronic and thermoelectric devices. This study examines the Ag-41.0 at%Sb/Cu interfacial reactions and the phase equilibria isothermal sections of Ag–Cu–Sb at 300 °C and 500 °C. The Ag–Sb eutectic is reexamined and is at Ag-42.0 at%Sb and at 484.5 °C. No ternary compound is observed in the Ag–Cu–Sb system. It is found the ternary solubilities in the binary compounds in the Ag–Cu–Sb system are not significant. The highest is 4.7 at.% Cu in the Ag7Sb compound. Two reaction phases, Cu2Sb and Ag3Sb, are formed in the Ag–Sb/Cu couples reacted at 300 °C. Three reaction phases, Cu2Sb, Cu3Sb and Ag3Sb, are formed in the Ag–Sb/Cu couples reacted at 500 °C. The reaction rate in the couples reacted at 500 °C is very fast, and the reaction layer is 89 μm thick in the couple reacted for 4 min.

Unveiling the microscopic origin of asymmetric phase transformations in (de)sodiated Sb2Se3 with in situ transmission electron microscopy

Abstract Sodium-ion batteries (SIBs) have huge application potential in large-scale energy storage systems due to high abundance and low cost of sodium resource. Metal chalcogenides, which store Na ions by multiple reactions of intercalation, conversion, and alloying, are considered promising anode materials with high theoretical capacity but often suffer from fast capacity fading and underlying reason remains elusive due to the lack of a precise understanding of microscopic behaviors. Here, combined with in situ high-resolution transmission electron microscopy and consecutive electron diffraction, we tracked phase transformations during (de)sodiation of Sb2Se3 nanowires in real time and revealed multi-step reaction mechanisms. During sodiation, Sb2Se3 NWs firstly underwent the intercalation of Na ions and forming NaxSb2Se3 phase, following by the conversion reaction into Na2Se and Sb phases; afterwards, metallic Sb could further alloy with Na to form Na3Sb phase via sequential intermediate NaxSb phases. While during desodiation, despite the reversible dealloying of Na3Sb phase, the following deconversion of Na2Se and Sb phases back to Sb2Se3 phase was incomplete, which is deemed to be the key factor causing rapid capacity decay. Furthermore, we reveal that contact interfaces between NWs greatly affected the degree of deconversion reaction due to possibly changed electrode reaction kinetics. This work not only reports the first experimental visualization proof showing the effect of contact interfaces on phase transformations of electrode materials, but also affords new insights into capacity decay mechanisms and rational design of high-capacity SIBs.

YbCu0.52(2)Sb: Mixed-valent compound with a layered structure

A new ytterbium copper antimonide, YbCu0.52(2)Sb, was synthesized from the Pb-flux reactions, and its crystal structure was determined by the single-crystal X-ray diffraction method. The compound crystallizes in the trigonal space groupR3¯m (No. 166), a = 4.4494(4) Å, c = 33.767(7) Å, which adopts the same structure as Ca0.61(1)Ce0.39(1)Ag0.60(1)Sb. The crystal structure of this compound can be rationalized as a combination of the YbCuSb and YbSb structures. Also, the formula can be written as a sum of these two components, [(Yb2+)(Cu+)(Sb3−)]0.52[(Yb3+)(Sb3−)]0.48. The magnetic susceptibility measurements indicated coexistence of Yb2+ and Yb3+ in the structure, which was further supported by the X-ray photoelectron spectroscopy. The temperature dependent resistivity measurements indicated the metallic nature of the material. Since the Yb-Cu-Sb system contains very limited member compounds, the discovery of this ternary YbCu0.52(2)Sb phase is important, which represents a completely new fashion in stabilizing the crystal structure.

Effective phonon scattering and enhancement of thermoelectric performance in Ga-excess Bi0.4Sb1.6Te3 compounds

We investigate the thermoelectric properties on Ga-excess p-type GaxBi0.4Sb1.6Te3 compounds. Even though the random distribution of Ga-doping increases electrical resistivity giving rise to the decrease of power factor, the significant decrease of lattice thermal conductivity by the excess Ga-doping induces significant enhancement of ZT value (1.13 at 350 K) for the Ga x = 0.03 doped compound. From the X-ray diffraction and elemental mapping by energy dispersive X-ray spectroscopy, we observed Sb and Ga phase separation leading to the phonon scattering. The Sb precipitation implies atomic defect in the matrix which can induce short wavelength phonon scattering. The synergetic phonon scatterings from various scattering sources such as point defect, alloy scattering, and grain boundary phonon scattering have an important role in the enhancement of thermoelectric performance.