Sb Phase Diagram Research Articles

Ba5Sb8: The Highest Homologue of the Family of Binary Semiconducting Barium Antimonides BanSb2n−2 (n ≥ 2)

A novel binary compound within the Ba–Sb phase diagram, Ba5Sb8, was synthesized by combining elements with an excess of Sb in an alumina crucible. Structural elucidation was performed using single-crystal X-ray diffraction. This compound crystallizes in the orthorhombic space group Fdd2 with unit cell parameters of a = 15.6568(13) Å, b = 35.240(3) Å, c = 6.8189(6) Å, adopting its own structure type. The most distinctive features of the structure are the eight-membered [Sb8]10− polyanionic fragments which have no known precedents among antimonides. They are separated by five Ba2+ cations, which afford the charge balance and enable adherence to the Zintl–Klemm formalism. Ba5Sb8 is the highest known member of the homologous series within the family of barium antimonides BanSb2n−2 (n ≥ 2), all of which boast anionic substructures with oligomeric moieties of pnictogen atoms with varied lengths and topologies. Electronic structure calculations indicate an indirect narrow bandgap of ca. 0.45 eV, which corroborates the valence-precise chemical bonding in Ba5Sb8.

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.

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.

Mixing Enthalpies of Sr–Sb Melts

The mixing enthalpies of Sr–Sb melts were measured by isoperibolic calorimetry at 1230 K over the entire composition range referred to the liquid components. Large exothermic mixing effects were found (∆Hmin = –70.1 ± 4.8 kJ/mole). They were indicative of very strong interaction between the components and agreed with the Sr–Sb phase diagram. A series of intermetallic compounds, SrSb, SrSb3, Sr3Sb2, and Sr2Sb, was found in the system. Minimum ∆H for the liquid alloys corresponds to the composition range where SrSb and Sr3Sb2 phases exist. The mixing enthalpies were found to be less exothermic than those for the intermetallic phases. This finding agrees with data for the alloys in systems with strong interaction between the components and is indicative of short-range ordering in liquid state. The mixing enthalpies for Mg (Ca, Sr)–Sb melts decrease in the Mg–Sb → Ca–Sb → Sr–Sb series, which agrees with increasing differences in the electronegativity of the components.

Experimental study and thermodynamic re-assessment of the Co–Sb system

The Co–Sb system is of a special attention due to existence of CoSb3 skutterudite structure which is the key structure for doped skutterudite based thermoelectric materials. A critical review of this system, performed recently, shows the published thermodynamic assessment may not be fully correct compared to existing studies. Especially, there is a contradiction in the position of the liquidus line on the Sb-rich side of the phase diagram and of the eutectic reaction, liquid ↔ CoSb3 + (Sb). As these data are crucial for the study of thermal stability of skutterudite based thermoelectric materials, a good knowledge on phase relations in the Sb-rich part of the Co–Sb phase diagram is needed. To obtain reliable data, experimental alloys covering 80 to 100 at.% of Sb were prepared and investigated by differential thermal analysis and phase analysis. The data were compared with existing literature information and thermodynamic re-assessment of this binary system based on the CALPHAD approach was done.

Isothermal section of the phase diagram and crystal structures of the compounds in the ternary system Tm–Cu–Sb at 870 K

The isothermal section of the Tm–Cu–Sb phase diagram at 870 K was constructed using X-ray phase analysis. The existence of one ternary compound was confirmed - TmCu1-xGe2 (x = 0.109) (structure type HfCuSi2, space group P4/nmm, Pearson code tP8-0.22, a = 4.24170(2), c = 9.73942(9) Å). New ternary copper antimonides Tm3Cu20+xSb11-x (x = 2) (structure type Dy3Cu20+xSb11-x, space group F-43 m, Pearson code cF272, a = 16.55784(4) Å) and TmCu4–xSb2 (x = 1.065) (structure type ErFe4Ge2 (LTM), space group Pnnm, Pearson code oP14–2.13, a = 7.00565(6), b = 7.83582(6), c = 4.25051(3) Å) were found. The crystal structures of compounds were refined by full-profile Rietveld method using X-ray powder diffraction data. The solubility of the third component in all binary phases was found to be negligible. The crystal structures of known ternary antimonides were analyzed and relationship among the crystal structures of compounds in the ternary system Tm–Cu–Sb was illustrated.

Experimental investigation and thermodynamic calculation of the Ge–In–Sb phase diagram

Phase diagram of the Ge–In–Sb ternary system was investigated using differential thermal analysis (DTA), scanning electron microscopy (SEM) with energy dispersive spectrometry (EDS), and X-ray powder diffraction (XRD) methods. Experimentally obtained results were compared with the results of thermodynamic calculation of phase equilibria using calculation of phase diagram (CALPHAD) method and literature data.Phase transition temperatures of alloys with overall compositions along three selected vertical sections Ge–In0.5Sb0.5, In–Ge0.5Sb0.5, and Sb–Ge0.5In0.5 were measured by DTA. Two ternary eutectic reactions, one quasi-binary eutectic reaction and liquidus temperatures were experimentally determined and compared with the results of thermodynamic calculation.Identification of coexisting phases in samples equilibrated at 400 °C and 550 °C were performed using SEM–EDS and XRD methods. Obtained results were compared with calculated isothermal sections of the Ge–In–Sb ternary system at associated temperatures.Calculated liquidus projection and invariant equilibria of the Ge–In–Sb ternary system was presented.

Experimental investigation and thermodynamic prediction of the Ag–Ge–Sb phase diagram

Phase diagram of the Ag–Ge–Sb ternary system has been investigated experimentally and extrapolated using optimized thermodynamic parameters for the constitutive binary systems. Experimental results obtained using differential thermal analysis (DTA), scanning electron microscopy (SEM) with energy dispersive spectrometry (EDS), and X-ray powder diffraction (XRD) methods were compared with predicted phase equilibria.Identification of coexisting phases in the chosen as-cast samples and samples annealed at 400°C was performed using SEM–EDS and XRD methods. Liquidus temperatures for selected samples with overall compositions along three vertical sections Ag–Ge0.5Sb0.5, Ge–Ag0.5Sb0.5 and Sb–Ge0.5Ag0.5 were measured by DTA. Ternary eutectic reaction was experimentally determined by means of applied experimental techniques.

Experimental investigation and thermodynamic calculations of the Al–Cu–Sb phase diagram

Phase diagram of the Al–Cu–Sb ternary system was investigated experimentally by DTA and SEM–EDS methods and theoretically by CALPHAD method. The liquidus projection, invariant equilibria, three vertical sections: Sb–Al0.5Cu0.5, Al–Cu0.5Sb0.5 and Cu–Al0.5Sb0.5 as well as isothermal sections at 400°C and 200°C were predicted using COST MP0602 thermodynamic database. In addition, phase transition temperatures of the selected samples with compositions along calculated isopleths were experimentally determined using DTA. Experimentally obtained phase transition temperatures were compared with the results of thermodynamic calculation. Predicted isothermal sections at 400°C and 200°C were compared with the results of the SEM–EDS analysis from this work. In both cases, a good agreement between theoretical calculations and experimental results was obtained.

Phase equilibrium and intermediate phases in the Eu–Sb system

Rapid heating rate thermal analysis, X-ray diffraction, fluorescence spectrometry, and differential dissolution method were used to study the high-temperature phase equilibrium in the Eu–Sb system within the composition range between 37 and 96 at% Sb. The techniques were effective in determination of the vapor–solid–liquid equilibrium since intermediate phases except Eu 4Sb 3 evaporated incongruently after melting. A thermal procedure was developed to determine the liquidus and solidus lines of the T−x diagram. Six stable phases were identified: two phases, EuSb 2 and Eu 4Sb 3, melt congruently at 1045±10 °C and 1600±15 °C, the Eu 2Sb 3, Eu 11Sb 10, Eu 5Sb 4, and Eu 5Sb 3 phases melt incongruently at 850±8 °C, 950±10 °C, 1350±15 °C, and 1445±15 °C, respectively. The exact composition shifting of Sb-rich decomposable phases towards Eu 4Sb 3, the most refractory compound, was determined. The topology of the Eu–Sb phase diagram was considered together with that of the Yb–Sb system.

Experimental investigation and thermodynamic prediction of the Au–Cu–Sb phase diagram

Phase diagram of the ternary Au–Cu–Sb system was investigated experimentally by DTA and SEM–EDS methods and analytically by CALPHAD method. The liquids projection, invariant equilibrium, several vertical sections and isothermal section at 300 °C were predicted using COST 531 thermodynamic database. Phase transition temperatures of alloys along four predicted vertical sections of the Au–Cu–Sb ternary system with molar ratios Au:Cu = 1, Cu:Sb = 1, Au:Sb = 1 and x(Au) = 0.2 were measured by DTA (differential thermal analysis). Predicted isothermal section at 300 °C was compared with the results of the SEM (scanning electron microscope) with EDS (energy dispersive spectrometry) analysis from this work. This Au–Cu–Sb system belongs to the group of gold alloys, as potential candidates for new lead-free solder materials.

Experimental investigation and thermodynamic prediction of the Ni–Pb–Sb phase diagram

The phase diagram of the ternary Ni–Pb–Sb system was investigated experimentally by differential scanning calorimetry (DSC) and scanning electron microscopy (SEM) with energy dispersive spectrometry (EDS) methods, and predicted using the calculation of phase diagrams (CALPHAD) method. The phase transition temperatures of alloys along three predicted vertical sections of the Ni–Pb–Sb ternary system, with molar ratio Ni:Sb=1:3, Ni:Pb=1, and x(Sb)=0.6, were measured by DSC. The predicted isothermal section at 700 °C was compared with the results of the SEM–EDS analysis in this work.

Experimental investigation and thermodynamic calculation of Bi–Ga–Sb phase diagram

Phase diagram of the Bi–Ga–Sb ternary system has been investigated by DTA and SEM with EDS measurements. Phase transition temperatures in four vertical sections and isothermal section at 500°C were studied. Experimental results were compared with calculated phase diagram by the Calphad method.

Synthesis and characterisation of the compound CoSbS

In the search for new intermetallic materials with high thermoelectric performances, the Co–Sb–S ternary system has been explored and polycrystalline CoSbS samples have been prepared by a vapour phase technique starting from the pure elements. The crystal cell of CoSbS belongs to the Pbca space group and shows an orthorhombic structural arrangement with the following lattice parameters: a = 5.8341(2) A; b = 5.9477(2) A, and c = 11.6540(4) A. The structure belongs to the pyrite–marcasite family, as Co forms tilted corner- and edge-sharing octahedra with three Sb and three S atoms. Scanning electronic microscopy (SEM), electron-probe microanalysis (EPMA) and X-ray powder diffraction were used to investigate the microstructure and to carry out the structural analysis; the crystal structure was refined by the Rietveld method using the DBWS-9807 program. The thermal stability of CoSbS was investigated referring to the ternary Co–S–Sb phase diagram and by differential thermal analysis (DTA) measurements. Thermoelectric power measurements at room temperature were also performed by a home-made instrument.

Solution Synthesis of a New Thermoelectric Zn1+xSb Nanophase and Its Structure Determination Using Automated Electron Diffraction Tomography

Engineering materials with specific physical properties have recently focused on the effect of nanoscopic inhomogeneities at the 10 nm scale. Such features are expected to scatter medium- and long-wavelength phonons thereby lowering the thermal conductivity of the system. Low thermal conductivity is a prerequisite for effective thermoelectric materials, and the challenge is to limit the transport of heat by phonons, without simultaneously decreasing charge transport. A solution-phase technique was devised for synthesis of thermoelectric "Zn(4)Sb(3)" nanocrystals as a precursor for phase segregation into ZnSb and a new Zn-Sb intermetallic phase, Zn(1+delta)Sb, in a peritectoid reaction. Our approach uses activated metal nanoparticles as precursors for the synthesis of this intermetallic compound. The small particle size of the reactants ensures minimum diffusion paths, low activation barriers, and low reaction temperatures, thereby eliminating solid-solid diffusion as the rate-limiting step in conventional bulk-scale solid-state synthesis. Both phases were identified and structurally characterized by automated electron diffraction tomography combined with precession electron diffraction. An ab initio structure solution based on electron diffraction data revealed two different phases. The new pseudo-hexagonal phase, Zn(1+delta)Sb, was identified and classified within the structural diversity of the Zn-Sb phase diagram.

Thermodynamic investigation of the Pb – Sb system

The enthalpies of mixing of lead – antimony alloys were determined at 973 K in the range 0.2 < X Sb < 0.6 by direct liquid–liquid reaction calorimetry (DLLRC). The results are compared with data of the literature. The mixing enthalpies in the Pb – Sb liquid phase are weakly negative over the entire investigated concentration range with a minimum at Δ mix H m = −70 J mol −1 at X Sb = 0.4. In addition, the Pb – Sb phase diagram on the Pb-rich side was revised using differential scanning calorimetry (DSC). The coordinates of the eutectic point have been ensured. An optimization of the binary Pb – Sb system was finally performed. The calculated phase diagram and thermodynamic functions agree well with experimental data.

Experimental investigation and thermodynamic calculation of the Cu–In–Sb phase diagram

The phase diagram of the Cu–In–Sb ternary system is of importance in predicting the interface reaction between In-based solder materials and the Cu substrate. The liquidus surface, invariant equilibria and four vertical sections of the Cu–In–Sb ternary system were calculated by the CALPHAD method using binary thermodynamic parameters included in the COST531 database. Alloys, representing two isopleths from indium corner with molar ratio of copper and antimony equal to 1/3 and 1/1 and two isopleths from antimony corner with molar ratio of indium and copper equal to 3/1 and 1/1 were measured with the DTA (Differential Thermal Analysis) and DSC (Differential Scanning Calorimetry). The experimentally determined phase transition temperatures were compared with calculation results and good mutual agreement was noticed.

Interaction of the Components in the Ni—Zn—Sb Ternary System at 570 K.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Isothermal Cross‐Section of the Cu—Ho—Sb Phase Diagram at 500 °C.

AbstractFor Abstract see ChemInform Abstract in Full Text.