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Natalya A Zimbovskaya, Abraham Nitzan
In this work, we theoretically study steady state thermoelectric transport through a single-molecule junction with a long chain-like bridge. Electron transmission through the system is computed using a tight-binding model for the bridge. We analyze dependences of thermocurrent on the bridge length in unbiased and biased systems operating within and beyond the linear response regime. It is shown that the length-dependent thermocurrent is controlled by the lineshape of electron transmission in the interval corresponding to the HOMO/LUMO transport channel...
January 14, 2018: Journal of Chemical Physics
Mirosław Gierczak, Joanna Prażmowska-Czajka, Andrzej Dziedzic
This paper describes the design, manufacturing and characterization of newly developed mixed thick-/thin film thermoelectric microgenerators based on magnetron sputtered constantan (copper-nickel alloy) and screen-printed silver layers. The thermoelectric microgenerator consists of sixteen thermocouples made on a 34.2 × 27.5 × 0.25 mm³ alumina substrate. One of thermocouple arms was made of magnetron-sputtered constantan (Cu-Ni alloy), the second was a Ag-based screen-printed film. The length of each thermocouple arm was equal to 27 mm, and their width 0...
January 12, 2018: Materials
Pilkwang Kim, Ji Hoon Ryoo, Cheol-Hwan Park
The low-energy quasiparticles of Weyl semimetals are a condensed-matter realization of the Weyl fermions introduced in relativistic field theory. Chiral anomaly, the nonconservation of the chiral charge under parallel electric and magnetic fields, is arguably the most important phenomenon of Weyl semimetals and has been explained as an imbalance between the occupancies of the gapless, zeroth Landau levels with opposite chiralities. This widely accepted picture has served as the basis for subsequent studies...
December 29, 2017: Physical Review Letters
Jian Liu, Li Qiu, Riccardo Alessandri, Xinkai Qiu, Giuseppe Portale, JingJin Dong, Wytse Talsma, Gang Ye, Aprizal Akbar Sengrian, Paulo C T Souza, Maria Antonietta Loi, Ryan C Chiechi, Siewert J Marrink, Jan C Hummelen, L Jan Anton Koster
In this contribution, for the first time, the molecular n-doping of a donor-acceptor (D-A) copolymer achieving 200-fold enhancement of electrical conductivity by rationally tailoring the side chains without changing its D-A backbone is successfully improved. Instead of the traditional alkyl side chains for poly{[N,N'-bis(2-octyldodecyl)-naphthalene-1,4,5,8-bis(dicarboximide)-2,6-diyl](NDI)-alt-5,5'-(2,2'-bithiophene)} (N2200), polar triethylene glycol type side chains is utilized and a high electrical conductivity of 0...
January 11, 2018: Advanced Materials
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
Hong Chen, Yu-Kun Chen, Hua Lin, Jin-Ni Shen, Li-Ming Wu, Xin-Tao Wu
A quaternary narrow-band-gap semiconductor, Ba2Cr4GeSe10, has been discovered by solid-state reaction. It features a new structure type and crystallizes in the triclinic space group P1̅ (No. 2). The featured 2D anionic layers are constructed by condensed CrSe6 octahedra that are stacking along the c axis, with dispersed GeSe4 tetrahedra and located Ba2+ cations forming these layers. The energy-band structure shows a clear separation between the region of electronic conduction and the zone of electronic insulation...
January 11, 2018: Inorganic Chemistry
Temesgen D Desissa, Nikola Kanas, Sathya P Singh, Kjell Wiik, Mari-Ann Einarsrud, Truls Norby
Diffusivity on the A- and B-site of polycrystalline perovskite CaMnO3-δ with Ca deficiency and spinel CaMn2O4 (marokite) as a secondary phase was studied using chemical tracers and secondary ion mass spectrometry (SIMS) complemented by electron probe microanalysis (EPMA). Thin films containing Sr and Co chemical tracers were deposited on the polished surface of the polycrystalline composite sample followed by annealing at 800-1200 °C for 96 h. Diffusion profiles for each tracer were determined with SIMS, followed by calculation of diffusion coefficients by fitting to appropriate models...
January 11, 2018: Physical Chemistry Chemical Physics: PCCP
Dana Ben-Ayoun, Yatir Sadia, Yaniv Gelbstein
In thermoelectric (TE) generators, maximizing the efficiency of conversion of direct heat to electricity requires the reduction of any thermal and electrical contact resistances between the TE legs and the metallic contacts. This requirement is especially challenging in the development of intermediate to high-temperature TE generators. PbTe-based TE materials are known to be highly efficient up to temperatures of around 500 °C; however, only a few practical TE generators based on these materials are currently commercially available...
January 10, 2018: Materials
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
Adili Aiyiti, Shiqian Hu, Chengru Wang, Qing Xi, Zhaofang Cheng, Minggang Xia, Yanling Ma, Jianbo Wu, Jie Guo, Qilang Wang, Jun Zhou, Jie Chen, Xiangfan Xu, Baowen Li
Modifying phonon thermal conductivity in nanomaterials is important not only for fundamental research but also for practical applications. However, the experiments on tailoring thermal conductivity in nanoscale, especially in two-dimensional materials, are rare due to technical challenges. In this work, we demonstrate the in situ thermal conduction measurement of MoS2 and find that its thermal conductivity can be continuously tuned to a required value from crystalline to amorphous limits. The reduction of thermal conductivity is understood from phonon-defect scattering that decreases the phonon transmission coefficient...
January 10, 2018: Nanoscale
Yen-Hao Lin, Tsung-Chi Lee, Yu-Sheng Hsiao, Wei-Keng Lin, Wha-Tzong Whang, Chun-Hua Chen
P-phenediamino-modified graphene (PDG) has been newly synthesized via a facile green one-step chemical route as a functionalized graphene-based additive to copolymerize with aniline for fabricating innovative PDG/polyaniline conducting polymer composites (PDG/PANI) containing very special semi-interpenetrating networks (S-IPNs). The S-IPNs which not only provide additional pathways by creating chemically-bonded PDG and PANI for smoothly transporting carriers, but greatly reduce the amount of graphene required to less than a few percent could effectively improve the overall electric conductivity and thus the thermoelectric performance...
January 10, 2018: ACS Applied Materials & Interfaces
Juan Camilo Alvarez Quiceno, Gustavo Dalpian, Adalberto Fazzio, Jorge M Osorio-Guillén
IrGa3 is an intermetallic compound which is expected to be a metal, but a study on the electronic properties of this material to confirm its metallic character is not available in the literature. In this work, we report for the first time a first-principles Density Functional Theory and semiclassical Boltzmann theory study of the structural, electronic and transport properties of this material. The inclusion of the spin-orbit coupling term is crucial to calculate accurately the electronic properties of this compound...
January 9, 2018: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Xin Yin, Jing-Yuan Liu, Ling Chen, Li-Ming Wu
Materials that can directly convert electricity into heat, i.e., thermoelectric materials, have attracted renewed attention globally for sustainable energy applications. As one of the state-of-the-art thermoelectric materials, In4Se3 features an interesting crystal structure of quasi-two-dimensional sheets comprising In/Se chains that provide a platform to achieve a Peierls distortion and support a charge density wave instability. Single-crystal In4Se3-δ (δ = 0.65) shows strong anisotropy in its thermoelectric properties with a very high ZT of 1...
January 9, 2018: Accounts of Chemical Research
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
A Kao, J Gao, K Pericleous
In the undercooled solidification of pure metals, the dendrite tip velocity has been shown experimentally to have a strong dependence on the intensity of an external magnetic field, exhibiting several maxima and minima. In the experiments conducted in China, the undercooled solidification dynamics of pure Ni was studied using the glass fluxing method. Visual recordings of the progress of solidification are compared at different static fields up to 6 T. The introduction of microscopic convective transport through thermoelectric magnetohydrodynamics is a promising explanation for the observed changes of tip velocities...
February 28, 2018: Philosophical Transactions. Series A, Mathematical, Physical, and Engineering Sciences
P Bouisset, M Nohl, A Bouville, G Leclerc
Atmospheric nuclear weapons tests carried out by the United States, the former Soviet Union, the United Kingdom, France and China between 1945 and 1980 resulted in radioactive fallout over the earth's surface of long-lived radionuclides, such as 137Cs, 239+240Pu and 238Pu that could be detected more than 50 years after their production. In addition, the burnup in the upper atmosphere of a thermoelectric generator fueled by 238Pu, SNAP-9A, contributed to the inventory of 238Pu deposited on the ground. In order to estimate the deposition densities of 137Cs, 239+240Pu and 238Pu in French Polynesia, we collected undisturbed soil samples up to 30 cm deep at eight sites in two islands (Hiva Oa, 139°W - 10°S and Raivavae, 148°W - 24°S) in 2015-2016...
January 4, 2018: Journal of Environmental Radioactivity
Weon Ho Shin, Jong Wook Roh, Byungki Ryu, Hye Jung Chang, Hyun Sik Kim, Soonil Lee, Won-Seon Seo, Kyunghan Ahn
It has been in difficulty in forming well-distributed nano- and meso-sized inclusions in a Bi2Te3-based matrix and thereby realizing no degradation of carrier mobility at interfaces between matrix and inclusions for high thermoelectric performances. Herein, we successfully synthesize multi-structured thermoelectric Bi0.4Sb1.6Te3 materials with Fe-rich nano-precipitates and sub-micron sized FeTe2 inclusions by a conventional solid state reaction followed by melt-spinning and spark plasma sintering that could be a facile preparation method for scale-up production...
January 5, 2018: ACS Applied Materials & Interfaces
Laaya Shaabani, Sima Aminorroaya-Yamini, Jacob Byrnes, Ali Akbar Nezhad, Graeme R Blake
Recently, hole-doped GeSe materials have been predicted to exhibit extraordinary thermoelectric performance owing largely to extremely low thermal conductivity. However, experimental research on the thermoelectric properties of GeSe has received less attention. Here, we have synthesized polycrystalline Na-doped GeSe compounds, characterized their crystal structure, and measured their thermoelectric properties. The Seebeck coefficient decreases with increasing Na content up to x = 0.01 due to an increase in the hole carrier concentration and remains roughly constant at higher concentrations of Na, consistent with the electrical resistivity variation...
December 31, 2017: ACS Omega
Zhen Wang, Congcong Fan, Zhixuan Shen, Chenqiang Hua, Qifeng Hu, Feng Sheng, Yunhao Lu, Hanyan Fang, Zhizhan Qiu, Jiong Lu, Zhengtai Liu, Wanling Liu, Yaobo Huang, Zhu-An Xu, D W Shen, Yi Zheng
SnSe is a promising thermoelectric material with record-breaking figure of merit. However, to date a comprehensive understanding of the electronic structure and most critically, the self-hole-doping mechanism in SnSe is still absent. Here we report the highly anisotropic electronic structure of SnSe investigated by angle-resolved photoemission spectroscopy, in which a unique pudding-mould-shaped valence band with quasi-linear energy dispersion is revealed. We prove that p-type doping in SnSe is extrinsically controlled by local phase segregation of SnSe2 microdomains via interfacial charge transferring...
January 3, 2018: Nature Communications
Pawan Kumar, D V Maheswar Repaka, Kedar Hippalgaonkar
We have developed a new and accurate technique to measure temperature dependent in-plane Seebeck coefficient and electrical conductivity of organic and inorganic thin films. The measurement device consists of one heater, two thermometers, and a four-probe configuration which is patterned on a substrate of choice using a simple shadow mask. The high resolution in temperature measurements and repeatability of resistance thermometry is leveraged while enabling simple implementation using only a shadow mask for patterning...
December 2017: Review of Scientific Instruments
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