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nanostructured thermoelectric material

Yu Liu, Yu Zhang, Silvia Ortega, Maria Ibáñez, Khak Ho Lim, Albert Grau Carbonell, Sara Martí-Sànchez, Ka Ming Ng, Jordi Arbiol, Maksym V Kovalenko, Doris Cadavid, Andreu Cabot
Bottom-up approaches for producing bulk nanomaterials have traditionally lacked control over the crystallographic alignment of nanograins. This limitation has prevented nanocrystal-based nanomaterials from achieving optimized performances in numerous applications. Here we demonstrate the production of nanostructured BixSb2-xTe3 alloys with controlled stoichiometry and crystallographic texture through proper selection of the starting building blocks and the adjustment of the nanocrystal-to-nanomaterial consolidation process...
March 16, 2018: Nano Letters
Xin Liang, Lei Shen
In2 O3 (ZnO)k natural superlattices (where k is an integer), consisting of relatively earth abundant and non-toxic elements with coarsening-resistant nanostructures, are environmentally friendly materials with the potential for high temperature thermoelectric applications. Herein, we report our investigation of the high temperature thermoelectric properties of the In2 O3 (ZnO)4 superlattice bulk polycrystals that were singly and dually doped with Al and Ce. Transport property measurements revealed that Al and Ce did not only enter the ZnO blocks but also modified the InO2 single atomic layers...
February 20, 2018: Nanoscale
Isaac M Felix, Luiz Felipe C Pereira
Superlattices are ideal model systems for the realization and understanding of coherent (wave-like) and incoherent (particle-like) phonon thermal transport. Single layer heterostructures of graphene and hexagonal boron nitride have been produced recently with sharp edges and controlled domain sizes. In this study we employ nonequilibrium molecular dynamics simulations to investigate the thermal conductivity of superlattice nanoribbons with equal-sized domains of graphene and hexagonal boron nitride. We analyze the dependence of the conductivity with the domain sizes, and with the total length of the ribbons...
February 9, 2018: Scientific Reports
Hiromichi Ohta, Sung Wng Kim, Shota Kaneki, Atsushi Yamamoto, Tamotsu Hashizume
Thermoelectric conversion is an energy harvesting technology that directly converts waste heat from various sources into electricity by the Seebeck effect of thermoelectric materials with a large thermopower (S), high electrical conductivity (σ), and low thermal conductivity (κ). State-of-the-art nanostructuring techniques that significantly reduce κ have realized high-performance thermoelectric materials with a figure of merit (ZT = S2∙σ∙T∙κ-1) between 1.5 and 2. Although the power factor (PF = S2∙σ) must also be enhanced to further improve ZT, the maximum PF remains near 1...
January 2018: Advanced Science (Weinheim, Baden-Wurttemberg, Germany)
Yoshiaki Nakamura
The design and fabrication of nanostructured materials to control both thermal and electrical properties are demonstrated for high-performance thermoelectric conversion. We have focused on silicon (Si) because it is an environmentally friendly and ubiquitous element. High bulk thermal conductivity of Si limits its potential as a thermoelectric material. The thermal conductivity of Si has been reduced by introducing grains, or wires, yet a further reduction is required while retaining a high electrical conductivity...
2018: Science and Technology of Advanced Materials
Biao Xu, Tianli Feng, Matthias T Agne, Qing Tan, Zhe Li, Kazuki Imasato, Lin Zhou, Je-Hyeong Bahk, Xiulin Ruan, G Jefferey Snyder, Yue Wu
Dismantling and reconstructing canonical binary compounds by inserting a third agent can significantly modify their electronic and phonon structures. Therefore, it has inspired the semiconductor communities in various fields, such as electronic devices, radiation detectors and solar cells. Introducing this paradigm will potentially revolutionize thermoelectrics as well, which has been largely relying on simple binary compounds for decades. Here via a solution synthesis, we rebuild the eco-friendly and non-expensive Bi2S3 by adding disordered Bi and weakly bonded I...
January 22, 2018: Angewandte Chemie
Elisabetta Dimaggio, Giovanni Pennelli
Silicon is a material with very good thermoelectric properties, with regard to Seebeck coefficient and electrical conductivity. Low thermal conductivities, and hence high thermal to electrical conversion efficiencies, can be achieved in nanostructures which are smaller than the phonon mean free path but large enough to preserve the electrical conductivity. We demonstrate that it is possible to fabricate a leg of a thermoelectric generator based on large collections of long nanowires, placed perpendicularly to the two faces of a silicon wafer...
January 22, 2018: Nanotechnology
Laith A Algharagholy, Tom Pope, Colin J Lambert
We show that carbon-based nanostructured materials are a novel testbed for controlling thermoelectricity and have the potential to underpin the development of new cost-effective environmentally-friendly thermoelectric materials. In single-molecule junctions, it is known that transport resonances associated with the discrete molecular levels play a key role in the thermoelectric performance, but such resonances have not been exploited in carbon nanotubes (CNTs). Here we study junctions formed from tapered CNTs and demonstrate that such structures possess transport resonances near the Fermi level, whose energetic location can be varied by applying strain, resulting in an ability to tune the sign of their Seebeck coefficient...
January 17, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Te-Huan Liu, Jiawei Zhou, Mingda Li, Zhiwei Ding, Qichen Song, Bolin Liao, Liang Fu, Gang Chen
Recent advancements in thermoelectric materials have largely benefited from various approaches, including band engineering and defect optimization, among which the nanostructuring technique presents a promising way to improve the thermoelectric figure of merit (zT) by means of reducing the characteristic length of the nanostructure, which relies on the belief that phonons' mean free paths (MFPs) are typically much longer than electrons'. Pushing the nanostructure sizes down to the length scale dictated by electron MFPs, however, has hitherto been overlooked as it inevitably sacrifices electrical conduction...
January 16, 2018: Proceedings of the National Academy of Sciences of the United States of America
Markus Joos, Giacomo Cerretti, Igor Veremchuk, Patrick Hofmann, Hajo Frerichs, Dalaver H Anjum, Tobias Reich, Ingo Lieberwirth, Martin Panthöfer, Wolfgang G Zeier, Wolfgang Tremel
The Magnéli phase V6O11 was synthesized in gram amounts from a powder mixture of V6O11/V7O13 and vanadium metal, using the spark plasma sintering (SPS) technique. Its structure was determined with synchrotron X-ray powder diffraction data from a phase-pure sample synthesized by conventional solid-state synthesis. A special feature of Magnéli-type oxides is a combination of crystallographic shear and intrinsic disorder that leads to relatively low lattice thermal conductivities. SPS prepared V6O11 has a relatively low thermal conductivity of κ = 2...
January 11, 2018: Inorganic Chemistry
Saravanan Muthiah, R C Singh, B D Pathak, Piyush Kumar Avasthi, Rishikesh Kumar, Anil Kumar, A K Srivastava, Ajay Dhar
The limited thermoelectric performance of p-type Higher Manganese Silicides (HMS) in terms of their low figure-of-merit (ZT), which is far below unity, is the main bottle-neck for realising an efficient HMS based thermoelectric generator, which has been recognized as the most promising material for harnessing waste-heat in the mid-temperature range, owing to its thermal stability, earth-abundant and environmentally friendly nature of its constituent elements. We report a significant enhancement in the thermoelectric performance of nanostructured HMS synthesized using rapid solidification by optimizing the cooling rates during melt-spinning followed by spark plasma sintering of the resulting melt-spun ribbons...
January 10, 2018: Nanoscale
Sonia Agata Barczak, John Halpin, Jim Buckman, Rodolphe Decourt, Michael Pollet, Ronald I Smith, Donald Maclaren, Jan-Willem G Bos
Half-Heusler alloys based on TiNiSn are promising thermoelectric materials characterised by large power factors, good mechanical and thermal stabilities; but they are limited by large thermal conductivities. A variety of strategies have been used to disrupt their thermal transport, including alloying with heavy, generally expensive, elements and nanostructuring, enabling figures of merit, ZT ≥ 1 at elevated temperatures (>773 K). Here, we demonstrate an alternative strategy that is based around the partial segregation of excess Cu leading to grain-by-grain compositional variations, the formation of extruded Cu 'wetting' layers between grains and - most importantly - the presence of statistically distributed interstitials that reduce the thermal conductivity effectively through point-defect scattering...
January 9, 2018: ACS Applied Materials & Interfaces
Zongqing Ren, Jaeho Lee
Artificial nanostructures have improved prospects of thermoelectric systems by enabling selective scattering of phonons and demonstrating significant thermal conductivity reductions. While the low thermal conductivity provides necessary temperature gradients for thermoelectric conversion, the heat generation is detrimental to electronic systems where high thermal conductivity are preferred. The contrasting needs of thermal conductivity are evident in thermoelectric cooling systems, which call for a fundamental breakthrough...
January 26, 2018: Nanotechnology
Miles A White, Alan M Medina-Gonzalez, Javier Vela
Filled tetrahedral semiconductors are a rich family of compounds with tunable electronic structure, making them ideal for applications in thermoelectrics, photovoltaics, and battery anodes. Furthermore, these materials crystallize in a plethora of related structures that are very close in energy, giving rise to polytypism through the manipulation of synthetic parameters. This Minireview highlights recent advances in the solution-phase synthesis and nanostructuring of these materials. These methods enable the synthesis of metastable phases and polytypes that were previously unobtainable...
November 28, 2017: Chemistry: a European Journal
Alexander Boehnke, Ulrike Martens, Christian Sterwerf, Alessia Niesen, Torsten Huebner, Marvin von der Ehe, Markus Meinert, Timo Kuschel, Andy Thomas, Christian Heiliger, Markus Münzenberg, Günter Reiss
Spin caloritronics studies the interplay between charge-, heat- and spin-currents, which are initiated by temperature gradients in magnetic nanostructures. A plethora of new phenomena has been discovered that promises, e.g., to make wasted heat in electronic devices useable or to provide new read-out mechanisms for information. However, only few materials have been studied so far with Seebeck voltages of only some microvolt, which hampers applications. Here, we demonstrate that half-metallic Heusler compounds are hot candidates for enhancing spin-dependent thermoelectric effects...
November 20, 2017: Nature Communications
Tiva Sharifi, Xiang Zhang, Gelu Costin, Sadegh Yazdi, Cristiano F Woellner, Yang Liu, Chandra Sekhar Tiwary, Pulickel Ajayan
We show that thermoelectric materials can function as electrocatalysts and use thermoelectric voltage generated to initiate and boost electrocatalytic reactions. The electrocatalytic activity is promoted by the use of nanostructured thermoelectric materials in a hydrogen evolution reaction (HER) by the thermoelectricity generated from induced temperature gradients. This phenomenon is demonstrated using two-dimensional layered thermoelectric materials Sb2Te3 and Bi0.5Sb1.5Te3 where a current density approaching ∼50 mA/cm(2) is produced at zero potential for Bi0...
November 13, 2017: Nano Letters
Sarah Friedensen, Jerome T Mlack, Marija Drndić
Focused ion beam milling allows manipulation of the shape and size of nanostructures to create geometries potentially useful for opto-electronics, thermoelectrics, and quantum computing. We focus on using the ion beam to control the thickness of Bi2Se3 and to create nanowires from larger structures. Changes in the material structure of Bi2Se3 nanomaterials that have been milled using a focused ion beam are presented. In order to characterize the effects of ion beam processing on the samples, we use a variety of techniques including analytical transmission electron microscopy and atomic force microscopy...
October 18, 2017: Scientific Reports
Duc-The Ngo, Le Thanh Hung, Ngo Van Nong
We demonstrate an advanced approach using state of the art in situ transmission electron microscopy (TEM) to understand the interplay between nanostructures and thermoelectric (TE) properties of high-performance Mg-doped Zn4 Sb3 TE systems. By using the technique, microstructure and crystal evolutions of TE material have been dynamically captured as a function of temperature from 300 K to 573 K. On heating, we have clearly observed precipitation and growth of a Zn-rich secondary phase as nanoinclusions in the matrix of primary Zn4 Sb3 phase...
January 5, 2018: Chemphyschem: a European Journal of Chemical Physics and Physical Chemistry
Takao Mori
Thermoelectrics (TE), the direct solid-state conversion of waste heat to electricity, is a promising field with potential wide-scale application for power generation. Intrinsic conflicts in the requirements for high electrical conductivity but (a) low thermal conductivity and (b) a large Seebeck coefficient have made enhancing TE performance difficult. Several recent striking advances in the field are reviewed. In regard to the former conflict, notable bottom-up nanostructuring methods for phonon-selective scattering are discovered, namely using nanosheets, dislocations, and most strikingly a process to fabricate nano-micropores leading to a 100% enhancement in the figure of merit (ZT ≈ 1...
December 2017: Small
Giuseppe Sansone, Andrea Ferretti, Lorenzo Maschio
Within the semiclassical Boltzmann transport theory in the constant relaxation-time approximation, we perform an ab initio study of the transport properties of selected systems, including crystalline solids and nanostructures. A local (Gaussian) basis set is adopted and exploited to analytically evaluate band velocities as well as to access full and range-separated hybrid functionals (such as B3LYP, PBE0, or HSE06) at a moderate computational cost. As a consequence of the analytical derivative, our approach is computationally efficient and does not suffer from problems related to band crossings...
September 21, 2017: Journal of Chemical Physics
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