Tellurium System Research Articles

Thermodynamics of Liquid Alloys and Vapor–Liquid Equilibrium in the Antimony–Tellurium System

The partial and integral thermodynamic functions of formation and evaporation of antimony-tellurium melts were calculated based on the vapor pressure values of the components in the Sb–Sb2Te3 and Sb2Te3–Te systems. It is shown that integral functions of evaporation enthalpy and entropy insignificantly change in value from the alloy corresponding to the Sb2Te3 composition and slightly decrease in the direction of antimony and tellurium on the state diagram. However, they can be described by a linear dependence in the entire concentration interval of solutions existence within the experiment error. The boundaries of liquid and vapor coexistence fields at atmospheric pressure (101.3 kPa) and in vacuum (0.9 kPa) were calculated based on the partial pressure values of melt components. It is shown that the separation of antimony alloys with tellurium by distillation into elements at atmospheric pressure is difficult because of high boiling temperatures of antimony-based alloys. It would require a significant number of condensate re-evaporation cycles in a vacuum. The results aim at creating the fundamental physical and chemical foundations of the distillation technologies for processing melted chalcogenide systems. The second aim is to issue effective practical recommendations necessary for developing and improving the process of extracting rare metals from polymetallic mattes by vacuum-thermal method.Graphical

Van der Waals nanomesh electronics on arbitrary surfaces

Chemical bonds, including covalent and ionic bonds, endow semiconductors with stable electronic configurations but also impose constraints on their synthesis and lattice-mismatched heteroepitaxy. Here, the unique multi-scale van der Waals (vdWs) interactions are explored in one-dimensional tellurium (Te) systems to overcome these restrictions, enabled by the vdWs bonds between Te atomic chains and the spontaneous misfit relaxation at quasi-vdWs interfaces. Wafer-scale Te vdWs nanomeshes composed of self-welding Te nanowires are laterally vapor grown on arbitrary surfaces at a low temperature of 100 °C, bringing greater integration freedoms for enhanced device functionality and broad applicability. The prepared Te vdWs nanomeshes can be patterned at the microscale and exhibit high field-effect hole mobility of 145 cm2/Vs, ultrafast photoresponse below 3 μs in paper-based infrared photodetectors, as well as controllable electronic structure in mixed-dimensional heterojunctions. All these device metrics of Te vdWs nanomesh electronics are promising to meet emerging technological demands.

Thermodynamic Modeling of the Uranium–Tellurium System: Estimation of the Uncertainties by a Bayesian Approach

Under irradiation, the formation of fission products in the (U,Pu)O2 fuel with time has a substantial effect on its chemistry. In particular, migration of the most volatile fission products (Cs, Te, I, Mo) from the center to the periphery of the fuel pellet is induced by the large radial thermal gradient. To predict the thermodynamic properties of the irradiated fuel, thermodynamic modeling of the complex multi-component (Cs-I-Te-Mo)–(U-Pu)–O system is performed using the CALPHAD method. In this work, the thermodynamic assessment of the U–Te sub-system is performed. The literature review reveals a lack of experimental data as well as scattering and inconsistency of some of the data. In particular, no thermodynamic data exist on the liquid. From this review, input thermodynamic and phase diagram data are carefully selected. The Gibbs energy functions are then adjusted by fitting these data. An overall good agreement is obtained with all the selected data except for the enthalpy of formation for UTe which is underestimated by 13% by our model. This could be due to an inconsistency between the enthalpy of formation and vapor pressure data. In a second step, the uncertainties on the thermodynamic parameters and their propagation on the calculated thermodynamic and phase diagram data are estimated using a Bayesian approach. The analysis shows that there are too many parameters (22) for too few data points (120 points). The uncertainties are thus large on some of the calculated data. Moreover the inconsistency of some of the data and the lack of thermodynamic data for the liquid makes the model uncertain. New experimental data such as heat capacity, enthalpy of formation for the compounds, and chemical potentials or activities for the liquid phase would improve the reliability of our model. Measurements of phase diagram data in the U–UTe2 region are also required. However this work provides the first detailed uncertainty analysis of the U–Te CALPHAD model. Moreover our approach, contrary to other Bayesian methods, provides an analytical posterior probability distribution and analytical credible intervals for the calculated thermodynamic quantities. It also speeds up the simulation of the uncertainty estimations on the phase diagram.

Thermodynamics of the Formation and Vaporization of Melts in an Aluminum Telluride–Tellurium System

Thermodynamics of the Formation and Vaporization of Melts in an Aluminum Telluride–Tellurium System

Successive phase transitions and magnetization plateau in the spin-1 triangular-lattice antiferromagnet Ba2La2NiTe2O12 with small easy-axis anisotropy

The crystal structure and magnetic properties of the spin-1 triangular-lattice antiferromagnet Ba$_2$La$_2$NiTe$_2$O$_{12}$ are reported. Its crystal structure is trigonal $R\bar{3}$, which is the same as that of Ba$_2$La$_2$NiW$_2$O$_{12}$ [Y. Doi et al., J. Phys.: Condens. Matter 29, 365802 (2017)]. However, the exchange interaction $J/k_{\mathrm{B}}\simeq19$ K is much greater than that observed in the tungsten system. At zero magnetic field, Ba$_2$La$_2$NiTe$_2$O$_{12}$ undergoes successive magnetic phase transitions at $T_{\mathrm{N}1}=9.8$ K and $T_{\mathrm{N}2}=8.9$ K. The ground state is accompanied by a weak ferromagnetic moment. These results indicate that the ground-state spin structure is a triangular structure in a plane perpendicular to the triangular lattice owing to the small easy-axis-type anisotropy. The magnetization curve exhibits the one-third plateau characteristic of a two-dimensional triangular-lattice Heisenberg-like antiferromagnet. Exchange constants are also evaluated using density functional theory (DFT). The DFT results demonstrate the large difference in the exchange constants between tellurium and tungsten systems and the good two-dimensionality of the tellurium system.

Topological phase transitions driven by strain in monolayer tellurium

Two-dimensional (2D) Xenes of a single type of element can offer fascinating electronic properties, such as massless Dirac fermions for extremely high charge-carrier mobility and topological insulators for dissipationless electron transport. However, the realization of either the massless Dirac fermions or the topological insulator in a same element system via a simple physical method has rarely been reported, which is of great importance for the development of next-generation electronic devices. Here, by using first-principles calculations, we identify that a 2D square tellurium system can be effectively tuned to realize either the massless Dirac fermions or the topological insulator phase. The 2D square tellurium system shows three structural phases via strain effect, i.e., buckled square, buckled rectangular, and planar square phases, which exhibit extraordinary topological properties. There are four anisotropic Dirac points in the buckled square phase, in which the Fermi velocity can be as high as 9.44 × 10 5 m / s . The buckled rectangular phase can behave as a quantum spin Hall insulator with a band gap of 0.24 eV, pointing towards promising applications for room-temperature devices. There also exist nodal lines in buckled square/planar square structures in the non-spin-orbit-coupling case. These findings extend the knowledge on single-layer materials and promote future applications of the 2D tellurium systems.

Chemical Insights into the Antioxidant Mechanisms of Alkylseleno and Alkyltelluro Phenols: Periodic Relatives Behaving Differently.

The possible antioxidant reaction mechanisms of recently synthesized and tested alkylseleno (telluro) phenols have been explored using density functional theory by considering two solvents physiologically relevant, water and pentylethanoate (PE). In addition, the possible pathway for the antioxidant regeneration with ascorbic acid has been investigated. Results show that selenium and tellurium systems follow different chemical behaviors. In particular, the alkylseleno phenol (ebselenol) antioxidant activity is justified through a sequential proton loss-electron-transfer mechanism in water media, whereas in PE the hydrogen-atom transfer process is favored. In the case of the tellurium derivative, the oxygen-transfer mechanism represents the preferential one. Furthermore, electronic properties have been analyzed to rationalize the different reactivity of the selenium- and tellurium-containing systems. To confirm the results, smaller but similar systems were also investigated. The calculated data support the different mechanism (Se vs. Te) proposals.

Thermodynamic Analysis of Alloys in Sodium–Tellurium System in Liquid and Solid States

The whole set of available data on the thermodynamic properties of liquid alloys and solid phases in the sodium–tellurium system is considered, beginning from the first study in 1970 and till the recent reports in 2015. The application of the sodium–tellurium system in chemical power cells is discussed.

Modeling of the thermodynamic properties of lead–tellurium liquid alloys

Application of the Redlich–Kister polynomial with varied number of parameters for describing the concentration dependence of thermodynamic systems of liquid metallic systems with a strong interaction between their components is considered for the example of the lead–tellurium system. Particular attention is given to the range of dilute solutions of tellurium in liquid lead.

Peri-substituted phosphorus-tellurium systems-an experimental and theoretical investigation of the P···Te through-space interaction.

A series of peri-substituted phosphorus-tellurium systems R'Te-Acenap-PR2 (R' = Ph, p-An, Nap, Mes, Tip; Acenap = acenaphthene-5,6-diyl (-C12H8); R = (i)Pr, Ph) exhibiting large "through-space" spin-spin coupling constants and the "onset" of three-center four-electron type interactions is presented. The influence of the substituents at the phosphorus and tellurium atoms as well as their behavior upon oxidation (with S, Se) or metal-coordination (Pt, Au) is discussed using NMR spectroscopy, single-crystal X-ray diffraction, and advanced density functional theory studies including NBO, AIM, and ELI-D analyses.

Thermodynamic assessment of the palladium–tellurium (Pd–Te) system

Among the fission products formed in nuclear fuels, the platinum-group metal palladium and the chalcogen element tellurium exhibit strong interaction. It is therefore of interest to be able to predict the chemical equilibria involving the Pd and Te fission products. A thermodynamic assessment is carried out using the Calphad (Calculation of Phase Diagram) method to investigate the behaviour of Pd–Te alloy system in nuclear fuels under irradiation and under waste disposal conditions. The Pd–Te binary description was optimized using experimental data found in literature including thermodynamic properties and phase diagram data. To validate the calculated phase diagram and thermodynamic properties, the results are compared with data from the literature. Both calculated and experimental phase diagrams and thermodynamic properties are in good agreement in the whole Pd–Te composition range.

Thermoelectric properties of ternary phases of thallium–tin–tellurium system

In this paper, we present the measurements of conductivity and of thermoelectric power. Measurements were taken for the temperature range of 100–330 K for the three ternary phases of Tl–Sn–Te system. The potential of these compounds as thermoelectric materials was studied.

Modeling of selenium telluride glass

AbstractWe develop model interaction potentials for the heterogeneous selenium–tellurium system based on ab initio molecular simulations and a cluster expansion technique. The model potentials are used in classical Monte Carlo simulations to characterize the structure of SeTe glass in the canonical ensemble. The simulated structure is in good qualitative agreement with available experimental data.1. Computed structure of SeTe glass (20 Å × 20 Å × 20 Å subset). The smaller (gray) atoms are selenium, and the larger (blue) atoms are tellurium. The SeTe glass consists of homopolar Se and Te chains with very little heteropolar bonding.image1. Computed structure of SeTe glass (20 Å × 20 Å × 20 Å subset). The smaller (gray) atoms are selenium, and the larger (blue) atoms are tellurium. The SeTe glass consists of homopolar Se and Te chains with very little heteropolar bonding.(© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Experimental and Theoretical Investigations of Tellurium(IV) Diimides and Imidotelluroxanes: X-ray Structures of B(C6F5)3 Adducts of OTe(μ-NtBu)2TeNtBu, [OTe(μ-NtBu)2Te(μ-O)]2 and tBuNH2

The hydrolysis of (t)BuNTe(mu-N(t)Bu)(2)TeN(t)Bu (1) with 1 or 2 equiv of (C(6)F(5))(3)B.H(2)O results in the successive replacement of terminal imido groups by oxo ligands to give the telluroxane-Lewis acid adducts (C(6)F(5))(3)B.OTe(mu-N(t)Bu)(2)TeN(t)Bu (2) and [(C(6)F(5))(3)B.OTe(mu-N(t)Bu)(2)Te(mu-O)](2) (3), which were characterized by multinuclear NMR spectroscopy and X-ray crystallography. The Te=O distance in 2 is 1.870(2) A. The di-adduct 3 involves the association of four (t)()BuNTeO monomers to give a tetramer in which both terminal Te=O groups [d(TeO) = 1.866(3) A] are coordinated to B(C(6)F(5))(3). The central Te(2)O(2) ring in 3 is distinctly unsymmetrical [d(TeO) = 1.912(3) and 2.088(2) A]. The X-ray structure of (C(6)F(5))(3)B.NH(2)(t)()Bu (4), the byproduct of these hydrolysis reactions, is also reported. The geometries and energies of tellurium(IV) diimides and imido telluroxanes were determined using quantum chemical calculations. The calculated energies for the reactions E(NR)(2) + Te(NR)(2) (E = S, Se, Te; R = H, Me, (t)Bu, SiMe(3)) confirm that cyclodimerization of tellurium(IV) diimides is strongly exothermic. In the mixed-chalcogen systems, the cycloaddition is energetically favorable for the Se/Te combination. The calculated energies for the further oligomerization of the dimers XE(mu-NMe)(2)EX (E = Se, Te; X = NMe, O) indicate that the formation of tetramers is strongly exothermic for the tellurium systems but endothermic (X = NMe) or thermoneutral (X = O) for the selenium systems, consistent with experimental observations.

Equilibria of simple thioenol/thiocarbonyl pairs. Comparison with the oxygen analogs and with the parent selenium and tellurium systems. A theoretical study

Thiocarbonyl–thioenol and carbonyl–enol equilibria (CH3C(X)R ⇌ H2CC(XH)R, X = S, O) were calculated by high level ab initio and density functional quantum mechanical methods for R = H, Me, Et, i-Pr, i-Bu, t-Bu, SiH3, CN, Ph, CH2Y (Y = Ph, CN, CF3, CHCH2), cyclic (CH2)nCX, n = 4–6, (PhCH2)2CS, PhCH2C(S)CHPh2 and i-Bu2CS. A detailed study when R = H, Me shows that B3LYP/6-31G(d,p) overestimates ΔH(thiocarbonyl–thioenol) by ca. 2 kcal mol−1. Isodesmic equations are used to evaluate separately the effect of R on each of the four species. A good agreement exists between the theoretical and the available experimental values. The ΔH(thiocarbonyl–thioenol) values of ca. −5.5 to 8 kcal mol−1 are much smaller than the ΔH(carbonyl–enol) values of ca. 5–17 kcal mol−1. A correlation exists between the ΔH terms of the two series. For R = H, Me the ΔH(CH3C(X)R − CH2 C(XH)R) values at the B3LYP/6-31G(d,p) level decrease as X is changed to a heavier chalcogen; e.g., when R = Me, ΔH = 14.9 (X = O), 6.1 (X = S), 1.7 (X = Se), −0.2 (est., X = Te).

Thermal dissociation of copper chalcogenides during melting

An attempt was undertaken to describe the mechanism of dissociation of copper chalcogenides during melting. Two-stage schemes of the dissociation of the Cu 2 B VI compounds (B VI is S, Se, or Te) were proposed. It was suggested that in the copper-sulfur and copper-selenium melts, Cu2BVI and CuBVI associates exist, whereas in the copper tellurium systems, Cu 2 Te and Cu 5 Te 3 associates exist. The interpretation of available data on magnetic susceptibility was given in terms of suggested associates in Cu-Te alloys.

A thermodynamic and structural analysis of selenium - tellurium melts

The thermodynamic properties of the selenium - tellurium system are analysed in terms of a novel regular solution model with multiple connectivity. The model is an extension of the regular solution model that discriminates between two forms of tellurium atom according to their connectivity (number of first neighbours). In the resulting ternary system, the chemical equilibrium between these two forms of tellurium is taken into account. The model can be solved in either the Bragg - Williams or the quasi-chemical approximation. A very good representation of the thermodynamic properties is obtained. Moreover, the model predicts a temperature and concentration evolution of the number of first neighbours in the liquid in close agreement with independent neutron scattering measurements. As a result, this model provides a simple insight into the mechanisms that are responsible for the complex thermodynamic and structural behaviour of the Se - Te system.

Electrochemical investigations of a copper—tellurium system and determination of the band gap for α-Cu 2Te

The activity of copper in various phases of the copper—tellurium system as a function of the metal to nonmetal ratios has been determind with the help of solid-state coulometric titrations in the temperature region between 350 and 450°C. Homogenous phases of the CuTe system have been found between Cu/Te ratios equal to about 2 1.92 [α-phase (Cu 2Te)], 1.43 1.39 [β-phase (Cu 4Te 3)] and 1.32 1.30 [γ-phase (CuTe)]. Analysis of the experimental data shows that the semiconducting properties of α-Cu 2Te and the change of the thermodynamic quantities with composition are due to changes of the thermodynamic quantities of the electrons as a component. The change of the thermodynamic quantities of the electrons are composed of those of the free electrons and electron holes. From the electrochemical measurements, besides partial molar enthalpy curves of electrons, the energetic band gap can be calculated and is about 0.673 eV for α-cuprous telluride.

A study of the phases in the bismuth - tellurium system

Bi 2Te 3 crystallizes in rhombohedral system, space group R3̄m. The hexagonal cell, a = 4.395(3) A ̊ and c = 30.44(1) A ̊ , contains three formula units. D x = 7.83 Mgm −3, μ = 64.17 mm −1. Its structure, refined from a single crystal, consists of 15 layers stacked along the ”c-axis“ and presents the combination of 3-layer stacks of (TeBiTeBiTe) composition. The coordination polyhedron of each atom is a distorted octahedron. The comparison of calculated and observed powder diffraction patterns allowed us to put in evidence a texture effect. A single crystal of the new phase Bi 8Te 9 has been obtained by thermal annealing. Preliminary diffraction study shows an hexagonal lattice with a = 4.41 A ̊ and c ≈ 103 A ̊ . A model of structure is proposed.

Reversible threshold switching in the Zn-doped selenium and tellurium system

Threshold switching in bulk amorphous samples of (Se0.7Te0.3)100-xZnx has been studied experimentally. It is observed that above a certain voltage across the sample the current through the material rises to a very high value without any increase in the potential across the sample. This threshold value of the voltage depends upon the zinc concentration in the material and the temperature of the sample. The switching behaviour is completely reversible in nature.