Showing papers on "Lead telluride published in 2013"

Synthesis and thermoelectric properties of compositional-modulated lead telluride-bismuth telluride nanowire heterostructures.

Abstract: We demonstrate the rational solution-phase synthesis of compositional modulated telluride nanowire heterostructures containing lead telluride (PbTe) and bismuth telluride (Bi2Te3). By tuning the ratio between PbTe and Bi2Te3 through adjusting the amount of critical reactants and precursors during the synthesis, the influence of composition on the thermoelectric properties of the nanowire heterostructures has been investigated in hot pressed nanocomposite pellets. Measurements of the thermoelectric properties show strongly reduced thermal conductivity that leads to an enhanced thermoelectric figure of merit (ZT) of 1.2 at 620 K.

Fermi surface and electron dispersion of PbTe doped with resonant Tl impurity from KKR-CPA calculations

Abstract: (Received 14 July 2013; revised manuscript received 24 September 2013; published 13 November 2013)We present results of a detailed study on the electron dispersions and Fermi surface of lead telluride dopedwith 2% of thallium, which is a resonant impurity in PbTe. Using the Korringa-Kohn-Rostoker method with thecoherent potential approximation (KKR-CPA), Bloch spectral functions (BSFs), which replace the dispersionrelations in alloys, are calculated, and BSF intensity maps over the Brillouin zone (alloy Fermi surface crosssections) are presented. It is shown that, close to the valence band edge, Tl does not create an isolated impurityband, but due to its resonant character, strongly disturbs the host electronic bands, leading to the disappearanceof sharp and well-defined electronic energy bands. The consequences of this effect on the transport propertiesare discussed and a qualitative explanation for the improvement in the thermoelectric properties of PbTe:Tl issuggested.DOI: 10.1103/PhysRevB.88.205205 PACS number(s): 72

Preparation of Ring-Shaped Thermoelectric Legs from PbTe Powders for Tubular Thermoelectric Modules

Abstract: Waste heat recovery—for example, in automotive applications—is a major field for thermoelectric research and future application. Commercially available thermoelectric modules are based on planar structures, whereas tubular modules may have advantages for integration and performance in the field of automotive waste heat recovery. One major drawback of tubular generator designs is the necessity for ring-shaped legs made from thermoelectric material. Cutting these geometries from sintered tablets leads to considerable loss of thermoelectric material and therefore high cost. Direct sintering of ring-shaped legs or tubes of thermoelectric material is a solution to this problem. However, sintering such rings with high homogeneity and density faces some difficulties related to the mechanical properties of typical thermoelectric materials such as lead telluride (PbTe)—particularly brittleness and high coefficient of thermal expansion. This work shows a process for production of thermoelectric rings made of p- and n-doped PbTe. Long tubes of PbTe have been sintered in a current-assisted sintering process with specially designed sintering molds, coated with a diffusion barrier, and finally cut into ring-shaped slices. To demonstrate the technology, a tubular thermoelectric module has been assembled using these PbTe rings.

Measurement of thermal conductivity of PbTe nanocrystal coated glass fibers by the 3ω method

Abstract: Fiber-based thermoelectric materials can conform to curved surfaces to form energy harvesting devices for waste heat recovery. Here we investigate the thermal conductivity in the axial direction of glass fibers coated with lead telluride (PbTe) nanocrystals using the self-heated 3ω method particularly at low frequency. While prior 3ω measurements on wire-like structures have only been demonstrated for high thermal conductivity materials, the present work demonstrates the suitability of the 3ω method for PbTe nanocrystal coated glass fibers where the low thermal conductivity and high aspect ratio result in a significant thermal radiation effect. We simulate the experiment using a finite-difference method that corrects the thermal radiation effect and extract the thermal conductivity of glass fibers coated by PbTe nanocrystals. The simulation method for radiation correction is shown to be generally much more accurate than analytical methods. We explore the effect of nanocrystal volume fraction on thermal conductivity and obtain results in the range of 0.50-0.93 W/mK near room temperature.

New materials for thermoelectric applications : theory and experiment

Abstract: Alternative Strategies for Thermoelectric Materials Development A.P. Gonzalves, C.Godart.- Thermopower in Correlated Systems B. Sriram Shastry.- Thermoelectric Properties of Correlated Electron Systems Ln3 Pt4Ge6 and LnPt4Ge12 (Ln = Ce, Pr) and Non-Centrosymmetric X2T12P7 (X = Yb, Hf and T = Fe, Co) B. D. White et al.- Thermopower of the Correlated Narrow Gap Semiconductor FeSi and Comparison to RuSi J.M. Tomczak et al.- Highly Efficient Sefgmented P-Type Thermoelectric Leg Y. Sadia et al.- Charge Kondo Effect in Thermoelectric Properties of Lead Telluride Doped with Thallium Impurities T.A. Costi and V. Zlatic.- Changes of Thermoelectric Properties and Hardness after HPT Processing iof Micro- and Nanostructured Skutterudites G. Rogl et al.- Thermal Transport of a Delta-Doped Multilayer with Strongly Correlated Electrons V. Zlatic, J.K. Frerricks.- From Superconductivity Towards Thermoelectricity: Ge-based Skutterudites S. Humer et al.- Nonlinear Thermoelectric Response of Quantum Dots: Renormalized Dual Fermions out of Equilibrium S. Kirchner et al.- Nernst Effect of Iron Pnictide and Cuprate Superconductors: Signatures of Spin Density Wave and Stripe order Chr. Hess.- Monte-Carlo Approach to Stationary Non-Equilibrium of Mesoscopic Systems: A. Dirks et al.- Influence of Dirac Fermions on Magnetothermoelectric Transport in Iron-Based Superconductors M. Matusiak et al.- Inducing Current in one Dimensional Systems of Interacting Fermions M. Mierzejewski et al.- Spin-orbital Entangles States in Transition Metal Oxides: A.M. Oles.- The Out-of-Equilibrium Time-Dependent Gutzwiller Apprioximation: M. Fabrizio.-

Thermoelectric properties of PbTe with encapsulated bismuth secondary phase

Abstract: Lead Telluride (PbTe) with bismuth secondary phase embedded in the bulk has been prepared by matrix encapsulation technique X-Ray Diffraction results indicated crystalline PbTe, while Rietveld analysis showed that Bi did not substitute at either Pb or Te site, which was further confirmed by Raman and X-Ray Photoelectron Spectroscopy Scanning Electron Microscopy showed the expected presence of a secondary phase, while Energy Dispersive Spectroscopy results showed a slight deficiency of tellurium in the PbTe matrix, which might have occurred during synthesis due to higher vapor pressure of Te Transmission Electron Microscopy results did not show any nanometer sized Bi phase Seebeck coefficient (S) and electrical conductivity (sigma) were measured from room temperature to 725 K A decrease in S and sigma with increasing Bi content showed an increased scattering of electrons from PbTe-Bi interfaces, along with a possible electron acceptor role of Bi secondary phase An overall decrease in the power factor was thus observed Thermal conductivity, measured from 400K to 725K, was smaller at starting temperature with increasing Bi concentration, and almost comparable to that of PbTe at higher temperatures, indicating a more important role of electrons as compared to phonons at PbTe-Bi interfaces Still, a reasonable zT of 08 at 725K was achieved for undoped PbTe, but no improvement was found for bismuth added samples with micrometer inclusions (C) 2013 American Institute of Physics http://dxdoiorg/101063/14796148]

Stress-induced growth of single-crystalline lead telluride nanowires and their thermoelectric transport properties

Abstract: Uniform single-crystal lead telluride (PbTe) nanowires (NWs) were synthesized using a stress-induced method, which is an alternative technique for synthesizing PbTe NWs without a catalyst. The thermoelectrical transport measurement of a NW with a diameter of 217 nm exhibited a notable enhancement over the room-temperature thermopower of −342 μV K−1, which was approximately 95% larger than the bulk of PbTe. The power factor of 104 μW m−1 K−2 is also higher than any previously reported power factor in PbTe NWs.

Stabilities and reconstructions of PbTe crystal surfaces from density-functional theory

Abstract: Lead telluride (PbTe) is a well-known functional material with current applications in fields such as nanostructured thermoelectrics. Here, we report comprehensive first-principles simulations for ...

Electronic structure of lead telluride-based alloys, doped with vanadium

Abstract: The crystal structure, composition, galvanomagnetic properties in low magnetic fields (4.2 K ≤ T ≤ 300 K, B ≤ 0.07 T), and the Shubnikov–de Haas effect (T = 4.2 K, B ≤ 7 T) are studied in Pb1−x−ySnxVyTe (x = 0, 0.05–0.18) alloys synthesized by the Bridgman technique with variable vanadium impurity concentrations. It is shown that increasing the vanadium content leads to the formation of regions enriched in vanadium and of microscopic inclusions of compounds with compositions close to V3Te4. In Pb1−yVyTe stabilization of the Fermi level by a deep vanadium level, an insulator–metal transition, and a rise in the free electron concentration are observed as the vanadium content is increased. The variation in the free charge carrier concentration with increasing vanadium concentration in Pb1−yVyTe and Pb1−x−ySnxVyTe (x = 0.05–0.18) alloys is compared. Possible models for rearrangement of the electronic structure in Pb1−x−ySnxVyTe alloys with vanadium doping are discussed.

Microwave Sintering of Bi 2 Te 3 - and PbTe-Based Alloys: Structure and Thermoelectric Properties

Abstract: Microwave sintering is well known as an expeditious process in applications involving ceramics and biomaterials. For powders in the nanometer range, rapid microwave heating could reduce material exposure to elevated temperatures, thus preserving nanostructures in the resulting materials. To investigate the potential of this technique for thermoelectric (TE) materials, we have prepared samples of bismuth-telluride- and lead-telluride-based alloys from powders, for both materials, having sizes of partially agglomerated particles distributed from 0.15 μm to 7 μm. Sintering of the cold-pressed powders was carried out in a microwave furnace for 900 s at temperatures in the range of 583 K to 623 K for bismuth telluride and 793 K to 813 K for lead telluride specimens. For optimized sintering times and temperatures, the samples obtained showed relative densities of almost 95%. Scanning electron microscopy shows some residual porosity and a reduction of grain size, up to a factor of 5 for PbTe, compared with optimized hot-extruded specimens. For bismuth telluride samples, the TE performance in the range of 300 K to 460 K is poor, which is attributed to the arbitrary texture obtained from cold pressing of a highly anisotropic alloy prior to its sintering. In contrast, PbTe exhibits isotropic properties, hence deficiency of texturing is not expected to have a negative impact on its TE properties. Harman measurements show a value of ZT = 0.42 at 617 K for PbTe p-type sintered samples, which is comparable to hot-extruded alloys from similar powders. The present work demonstrates that microwave sintering is a promising alternative to other powder consolidation techniques for polycrystalline materials exhibiting isotropic TE properties.

Improved Thermoelectric Properties of Se-Doped n-Type PbTe 1- x Se x (0 ≤ x ≤ 1)

Abstract: Enhancement of the thermoelectric figure of merit is of prime importance for any thermoelectric material. Lead telluride has received attention as a potential thermoelectric material. In this work, the effect of Se substitution has been systematically investigated in PbTe1−xSex. The thermoelectric properties of synthesized alloys were measured in the temperature range of 300 K to 873 K. For the particular composition of x = 0.5, α was highest at ~292 μV/K, while k was lowest at ~0.75 W/m-K, resulting in the highest dimensionless figure of merit of ZT ≈ 0.95 at 600 K. The increase in thermopower for x = 0.5 can be attributed to the high distortion in the crystal lattice which leads to the formation of defect states. These defect states scatter the majority charge carriers, leading to high thermopower and high electrical resistivity. The dramatic reduction of the thermal conductivity for x = 0.5 can be attributed to phonon scattering by defect states.

Electronic Structure, Lattice Dynamics and Thermoelectric Properties of PbTe from First-Principles Calculation

Abstract: The electronic structure and the lattice dynamics of lead telluride (PbTe) are investigated by using the density functional theory. The thermoelectric properties are then calculated using the semi-classical Boltzmann theory. Moreover, the relationships among the thermoelectric properties, the electronic structure and the lattice dynamics are also studied. Some strategies aiming at optimizing the thermoelectric properties are proposed. The related theoretical calculations therefore give a valuable insight on how to further enhance the thermoelectric properties of PbTe.

Structural aspects of changes induced in PbTe by doping with Mn, In and Ga

Abstract: The paper presents the extended results of structural investigations of Pb0.9Mn0.1Te, and Pb0.9Mn0.1Te systems doped with In (2 at.%) and Ga (4 at.%) by means of EXAFS (extended X-ray absorption fine structure) technique. EXAFS measurements performed at Te–, Mn–, In– and Ga–K absorption edges at different temperatures are complemented with X-ray diffraction, flame absorption and X-ray fluorescence analysis. That way the complete information about elemental concentration; crystal structure; local environment around constitutive and impurity atoms (including their displacements from the regular lattice positions); local and long-range ordering; and the overall influence of doping on the host crystal structure is derived. The obtained results represent an important step towards understanding the structural aspects of doping of lead telluride-based semiconductors with Mn and group III elements and their connection to electronic and optical phenomena important for their applications.

Probing of local electron states in Pb 1 − x Sn x Te(In) narrow-gap semiconductors by laser terahertz radiation

Abstract: Local electron states in indium-doped lead telluride-based solid solutions exhibit a number of features which separate them from the diversity of impurity states in semiconductors. These features are most pronounced in terahertz photoconductivity. The results of the corresponding experiments performed during the last years and supported by the Russian Foundation for Basic Research are reviewed.

ALD Growth of PbTe and PbSe Superlattices for Thermoelectric Applications

Abstract: For this study PbTe and PbSe thin films have been prepared on silicon substrates with native oxide by Atomic Layer Deposition (ALD) using lead (II)bis(2,2,6,6-tetramethyl-3,5-heptanedionato) (Pb(C11H19O2)2), (trimethylsilyl) telluride ((Me3Si)2Te) and bis-(triethyl silyl) selane ((Et3Si)2Se) as ALD precursors for lead, tellurium and selenium . Instead of classic layer by layer ALD growth the initial ALD nucleation of lead telluride was found to follow the Vollmer-Weber island growth model. We found a strong dependence of the nucleation process on the temperature. In this project, we present the optimized conditions for growing PbTe and PbSe thin films within the ALD process window range of 170 °C to 210 °C and discuss early nanolaminate structures. Results of various physical characterizations techniques and analysis are reported.

Thermoelectric Materials and Methods for Synthesis Thereof

Abstract: Materials having improved thermoelectric properties are disclosed. In some embodiments, lead telluride/selenide based materials with improved figure of merit and mechanical properties are disclosed. In some embodiments, the lead telluride/selenide based materials of the present disclosure are p-type thermoelectric materials formed by adding sodium (Na), silicon (Si) or both to thallium doped lead telluride materials. In some embodiments, the lead telluride/selenide based materials are formed by doping lead telluride/selenides with potassium.

One-step method for preparing graphene/lead telluride nano composite by means of coreduction

Abstract: The invention belongs to the field of materials, and particularly relates to a preparation method of a graphene/lead telluride nano composite. The preparation method includes: adding inorganic substance containing lead and compound containing telluric to a reactor containing deionized water, adding alkali, continuously stirring until the solution becomes transparent and clear, adding graphite oxide for fully dissolving, continuing to stir to obtain mixed sol, and adding reductant for fully dissolving; subjecting obtained mixture to constant-temperature reaction to obtain graphene/lead telluride nano composite powder precipitate; washing, centrifugally separating, and washing again and filtering; and vacuum drying the powder to obtain the graphene/lead telluride nano composite. Manufacturing cost of the composite can be reduced greatly, process is simple, scale production is easy to realize, using of massive organic solvent in the reaction can be avoided, and environmental protection is benefited. The prepared graphene/lead telluride nano composite is widely applicable to solar cells, thermoelectric devices, infrared optical elements, infrared thin-film devices, semi-conductor detectors and the like, and is promising in application prospect.

Dynamics of oxide phases on the surface of single- and polycrystalline Pb 1 − x Sn x Te films upon their investigation by the raman light scattering method

Abstract: We have studied Raman spectra of single- and polycrystalline Pb1 − xSnxTe (0 ≤ x ≤ 1) films on different substrates in relation to the intensity of the laser action. The composition of oxide phases on the surface of lead-tin telluride films has been described, and their modification as a result of photostimulated oxidation of the surface during measurements of spectra has been analyzed. We have shown that, for films with a small mole fraction of tin telluride (x ≤ 0.26), irrespective of the crystalline state, predominant oxidation of tellurium with the formation of the compound TeO2 takes place during the laser action. In films with a high content of tin, at a laser-action intensity higher than 1000 μW, tellurium dioxide TeO2 on the surface is replaced with tin dioxide SnO2.

Evaluation of optical constants of Tl4PbTe3 thin films with different thicknesses

Abstract: Thallium lead telluride (Tl4PbTe3) was prepared by direct reaction of high purity elemental thallium, lead and tellurium. Tl4PbTe3 thin films were prepared on well cleaned glass and silicon (100) substrates by electron beam evaporation. X-ray diffraction studies revealed that the films with low thickness were amorphous and the crystallinity increased with increasing film thickness. The thicker films were polycrystalline in nature and exhibited single phase structure. The composition of the chemical constituents present in the deposited Tl4PbTe3 thin films with different thicknesses was determined using energy dispersive analysis of X-ray. Spectroscopic ellipsometry was employed to determine the film thickness and optical constants. A two layer model was used to describe the experimental ellipsometric data. The refractive index and extinction coefficient were sensitive to the film thickness and increased with increasing the film thickness. The optical transmittance and reflectance spectra were dependent strongly on film thickness. The optical band gap decreased with the increase of thickness of the film.

Charge Kondo Effect in Thermoelectric Properties of Lead Telluride Doped with Thallium Impurities

Abstract: We investigate the thermoelectric properties of PbTe doped with a small concentration x of Tl impurities acting as acceptors and described by Anderson impurities with negative on-site correlation energy. The resulting charge Kondo effect naturally accounts for a number of the low temperature anomalies in this system, including the unusual doping dependence of the carrier concentration, the Fermi level pinning and the self-compensation effect. The Kondo anomalies in the low temperature resistivity at temperatures \(T\leq 10\, \mathrm { K}\) and the x-dependence of the residual resistivity are also in good agreement with experiment. Our model also captures the qualitative aspects of the thermopower at higher temperatures \(T>300\, \mathrm { K}\) for high dopings (\(x>0.6 \)) where transport is expected to be largely dominated by carriers in the heavy hole band of PbTe.

Preparation method for lead telluride-based thermoelectric coating material

Abstract: The invention belongs to the field of a thermoelectric material and in particular relates to a preparation method for a lead telluride-based thermoelectric coating material The preparation method comprises the following steps of: using graphite as an anode, Cu, Ni, Al, Au, Ag or graphite as a cathode; carrying out electro-deposition for 3-8 hours in an electrolyte solution at a temperature of 25 DEG C to 65 DEG C; depositing on the surface of the cathode to obtain a PbTe or PbTeTl thermoelectric coating The electro-deposition method provided by the invention has high efficiency, can obtain PbTe with a controllable thickness and uniform components and a PbTe-based thermoelectric material containing dopant; the electric potential of the electro-deposition or current density is controlled to realize the co-deposition of two or more metals, and to form the PbTe or the PbTeTl coating The preparation method has low cost, high efficiency and strong operability

Superconductive graphite synthesized slice, preparation method therefor and applications thereof

Abstract: The invention relates to a superconductive graphite synthesized slice, a preparation method therefor and applications thereof. The main principle is that by utilizing lateral and vertical conduction characteristics of a semiconductor, an N-shaped semiconductor is employed to increase the lateral heat conduction rate of graphite materials, so that the temperature of a heat source can be reduced rapidly. The preparation raw materials of the synthesized slice comprise semiconductor telluride and graphite materials. The semiconductor telluride can be one of cadmium telluride, lead telluride and bismuth telluride or two thereof, or three thereof. The heat conduction coefficient of the synthesized slice is 750-1650 w/m.k. The temperature of electronic products can be reduced to about 40 DEG C rapidly. The synthesized slice can be used for any portable and vehicle electronic device and high-power heat-generating electronic device, the temperature of the electronic devices can be reduced rapidly, the running speed can be faster, and the functions of the electronic devices can be optimized so that large programs can be installed.

Synthesis and Analyses of Thermoelectric Lead Telluride

Abstract: The influence of chemical composition effects, modes of synthesis, pressing on the structural states and electrical qualities of lead telluride has been investigated. The analyses indicated that thermoelectric parameters of the investigated materials depend on technological factors. The results revealed that conductivity is n-type in stoichiometric composition equilibrium and lead-excess states, while conductivity is p-type in tellurium-excess states. The maximum value of the Seebeck coefficient, which characterizes the thermoelectric materials, was obtained at d = 0.8-1.0 mm for powder fractions and 0.75-1.0 GPa for pressed.

Photoconductivity of vanadium-doped lead telluride in the terahertz spectral region

Abstract: It is shown that PbTe:V single crystals are photosensitive in the terahertz spectral region up to the wavelength 280 μm. The measurements are conducted in the temperature range from 8 to 300 K. In this temperature range, the dark conductivity of the crystals exhibits the activation character of the temperature dependence and varies by four orders of magnitude, which is due to Fermi-level pinning 20 meV below the bottom of the conduction band. As the temperature is elevated and, correspondingly, the conductivity increases, the amplitude of the photoresponse substantially increases. This result is interpreted in the context of the model that takes into account significant broadening of the vanadium impurity level and its shift to the bottom of the conduction band with increasing temperature.

Method for producing semiconductor structures n-pbte:bi with improved thermoelectric power

Abstract: A method for producing semiconductor structures n-PbTe:Bi with improved thermoelectric power includes the method of open vacuum evaporation, wherein the starting materials are vaporized from the compound synthesized in advance under the temperature T=(970±10) K on the glass-ceramic substrate under the temperature T. As a starting material lead telluride doped with bismuth n-PbTe:Bi with dopant content of 0.05 atm. % is used.

On the Debye-Waller Factor and Debye Temperature of Dendrite-Shaped PbTe

Abstract: In this study, the phonon dispersion curve of dendrite-shaped lead telluride (PbTe), a nano structured material is obtained by shell model and the thermal parameters are calculated and compared with experimental results.