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Ning Wang, Jiajun Chen, Kun Zhang, Mingming Chen, Hongzhi Jia
As thermoelectric coolers (TECs) have become highly integrated in high-heat-flux chips and high-power devices, the parasitic effect between component layers has become increasingly obvious. In this paper, a cyclic correction method for the TEC model is proposed using the equivalent parameters of the proposed simplified model, which were refined from the intrinsic parameters and parasitic thermal conductance. The results show that the simplified model agrees well with the data of a commercial TEC under different heat loads...
November 21, 2017: Scientific Reports
Mingxing Piao, Jin Chu, Xiao Wang, Yao Chi, Heng Zhang, Chaolong Li, Haofei Shi, Min-Kyu Joo
Two-dimensional (2D) materials have gained great attention as a promising thermoelectric (TE) material due to their unique density of state with confined electrons and holes. Here, we synthesized 1T phase tungsten disulfide (WS2) nanosheets with high TE performance via hydrothermal method. Flexible WS2 nanosheets restacked thin films were fabricated by employing vacuum filtration technique. The measured electrical conductivity was 45 S/cm with Seebeck coefficient of +30 μV/K at room temperature, indicating a p-type characteristic...
November 21, 2017: Nanotechnology
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
Wenyu Zhao, Zhiyuan Liu, Zhigang Sun, Qingjie Zhang, Ping Wei, Xin Mu, Hongyu Zhou, Cuncheng Li, Shifang Ma, Danqi He, Pengxia Ji, Wanting Zhu, Xiaolei Nie, Xianli Su, Xinfeng Tang, Baogen Shen, Xiaoli Dong, Jihui Yang, Yong Liu, Jing Shi
This corrects the article DOI: 10.1038/nature23667.
November 16, 2017: Nature
Grigory Skoblin, Jie Sun, August Yurgens
We use a split top gate to induce doping of opposite signs in different parts of a graphene field-effect transistor, thereby effectively forming a graphene thermocouple. The thermocouple is sensitive to the electronic temperature in graphene, which can be several hundred kelvin higher than the ambient one at sufficiently high bias current. Combined with the high thermoelectric power of graphene, this allows for i) simple measurements of the electronic temperature and ii) building thermoelectric radiation detectors...
November 14, 2017: Scientific Reports
Feridoon Azough, Samuel S Jackson, Dursun Ekren, Robert Freer, Marco Molinari, Stephen R Yeandel, Pooja M Panchmatia, Stephen C Parker, David Hernandez Maldonado, Demie M Kepaptsoglou, Quentin M Ramasse
To help understand the factors controlling the performance of one of the most promising n-type oxide thermoelectrics SrTiO3, we need to explore structural control at the atom level. In Sr1-xLa2x/3TiO3 ceramics (0.0 ≤ x ≤ 0.9), we determined that the thermal conductivity can be reduced and controlled through an interplay of La substitution and A-site vacancies and the formation of a layered structure. The decrease in thermal conductivity with La and A-site vacancy substitution dominates the trend in the overall thermoelectric response...
November 14, 2017: ACS Applied Materials & Interfaces
J Felix Shin, Hongjun Niu, Jonathan Alaria, John B Claridge, Matthew J Rosseinsky
Highly dense CaMn1-xRexO3 (0 ≤ x ≤ 0.04) samples were prepared by solid-state synthesis. The effect of Re doping was assessed by the characterisation of crystal structure, oxygen content, and electrical and thermal transport properties. The oxidation state of the substituted Re was determined by X-ray absorption near edge spectra to be Re(7+), and led to expansion of the lattice and an increase in electron carrier concentration due to the formation of Mn(3+). The thermal behaviour of the electrical conductivity and the thermopower over a wide temperature range allowed identification of different conduction mechanisms: (1) below 110 K, 3D variable range hopping, (2) between 110 and 650 K, small polaron transport, and (3) above 650 K, activation of carriers over a mobility edge...
November 22, 2017: Physical Chemistry Chemical Physics: PCCP
Jianhui Yang, Qiang Fan, Xinlu Cheng
The electronic, vibrational and thermoelectric transport characteristics of AgInTe2 and AgGaTe2 with chalcopyrite structure have been investigated. The electronic structures are calculated using the density-functional theory within the generalized gradient approximation (GGA) of Perdew-Burke-Ernzerhof functional considering the Hubbard-U exchange correlation. The band-gaps of AgInTe2 and AgGaTe2 are much larger than previous standard GGA functional results and agree well with the existing experimental data...
October 2017: Royal Society Open Science
Yan Zhang, Mengying Xie, Vana Adamaki, Hamideh Khanbareh, Chris R Bowen
Energy harvesting is a topic of intense interest that aims to convert ambient forms of energy such as mechanical motion, light and heat, which are otherwise wasted, into useful energy. In many cases the energy harvester or nanogenerator converts motion, heat or light into electrical energy, which is subsequently rectified and stored within capacitors for applications such as wireless and self-powered sensors or low-power electronics. This review covers the new and emerging area that aims to directly couple energy harvesting materials and devices with electro-chemical systems...
November 10, 2017: Chemical Society Reviews
Guanpeng Li, Kailun Yao, G Y Gao
Using first-principle calculations combined with Boltzmann transport theory, we investigate the biaxial strain effect on the electronic and phonon thermal transport properties of 1T (CdI2-type) structural TiS2 monolayer, a recent experimental two-dimensional (2D) material. It is found that the electronic band structure can be effectively modulated and the band gap experiences the indirect-direct-indirect transition with increasing tensile strain. The band convergence induced by the tensile strain increases the Seebeck coefficient and the power factor, meanwhile the lattice thermal conductivity is decreased under the tensile strain due to the decreasing group velocity and the increasing scattering chances between the acoustic phonon modes and the optical phonon modes, which together greatly increase the thermoelectric performance...
November 10, 2017: Nanotechnology
Denis Music, Keke Chang, Paul Schmidt, Felix N Braun, Martin Heller, Steffen Hermsen, Peter J Pöllmann, Till Schulzendorff, Cedric Wagner
Oxidation of Bi2Te3 (space group R [Formula: see text] m) has been investigated using experimental and theoretical means. Based on calorimetry, x-ray photoelectron spectroscopy and thermodynamic modelling, Bi2Te3 is at equilibrium with Bi2O3 and TeO2, whereby the most stable compound is Bi2Te3, followed by Bi2O3. The reactivity of Bi towards oxygen is expected to be higher than that of Te. This notion is supported by density functional theory. The strongest bond is formed between Bi and Te, followed by Bi-O...
November 9, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Yu Su, Xiaodong Wang, Qing Yu, Qingping Cao, U Ruett, Dongxian Zhang, Jianzhong Jiang
The temperature dependence of atomic structural evolution in the liquid Ag50Ga50 alloy has been studied by using in situ high energy X-ray diffraction (XRD) experiment combined with the first-principles molecular dynamics (FPMD) simulations. The experimental data show a reversible structural crossover at the temperature about 1050 K. Changes in both electrical resistivity and absolute thermoelectric power at about 1100 K strongly support the XRD results. Additionally, FPMD simulations reveal an abnormal temperature dependent behavior of partial coordination number and atomic diffusivity at about 1200 K, elucidating that the partition experimentally observed changes in structure and properties could be linked with the repartition between Ag and Ga atoms in the liquid at around 1050-1200 K...
November 9, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Joaquin Miranda Mena, Thomas Gruhn
We employed density functional theory, Monte Carlo simulations and a mean field model to study phase separation in thermoelectric Ni(Ti,Zr)(Sb,Sn) half-Heusler materials, simultaneously alloyed in the (Ti,Zr)- and (Sb,Sn) sublattices. We found that the material shows demixing and ordering phenomena as the temperature is lowered. Below a critical temperature, which depends on the overall stoichiometry, demixing occurs within the sublattices. Typically, a strong demixing in the (Ti,Zr) sublattice is accompanied by a weaker demixing in the (Sb,Sn) sublattice stoichiometry...
November 22, 2017: Physical Chemistry Chemical Physics: PCCP
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
Jeongmin Kim, Somi Yoo, Hongjae Moon, Se Yun Kim, Dong-Su Ko, Jong Wook Roh, Wooyoung Lee
The electrical conductivity and Seebeck coefficient of RuO2 nanosheets are enhanced by metal nanoparticle doping using Ag-acetate solutions. In this study, RuO2 monolayer and bilayer nanosheets exfoliated from layered alkali metal ruthenates are transferred to Si substrates for device fabrication, and the temperature dependence of their conductivity and Seebeck coefficients is investigated. For pristine RuO2 nanosheets, the sign of the Seebeck coefficient changes with temperature from 350 K to 450 K. This indicates that the dominant type of charge carrier is dependent on the temperature, and the RuO2 nanosheets show ambipolar carrier transport behavior...
November 8, 2017: Nanotechnology
Woosun Jang, Jiwoo Lee, Chihun In, Hyunyong Choi, Aloysius Soon
Despite the ubiquitous nature of the Peltier effect in low-dimensional thermoelectric devices, the influence of finite temperature on the electronic structure and transport in the Dirac heterointerfaces of the few-layer graphene and layered tetradymite, Sb2Te3 (which coincidently have excellent thermoelectric properties) are not well understood. In this work, using the first-principles density-functional theory calculations, we investigate the detailed atomic and electronic structure of these Dirac heterointerfaces of graphene and Sb2Te3 and further re-examine the effect of finite temperature on the electronic band structures using a phenomenological temperature-broadening model based on Fermi-Dirac statistics...
November 17, 2017: ACS Applied Materials & Interfaces
Ju Zhang, Xiwen Zhang, Yuanxu Wang
Previous experiments showed that Hf/Sb co-doping in ZrNiSn impressively improved the electrical conductivity (σ). To explore the physical reasons for this improvement, the electronic structures of HfxZr1-xNiSn1-ySby (x = 0, 0.25, 0.5; y = 0, 0.02) have been systematically investigated by using the first-principles method and semiclassical Boltzmann transport theory. 50% Hf doping at Zr site in ZrNiSn simultaneously increases the degeneracy and dispersion of energy bands near the conduction band edge, which are helpful to optimizing Seebeck coefficient and slightly improving σ...
November 6, 2017: Scientific Reports
Minhyun Jung, Kyungkwan Kim, Bumjin Kim, Kwang-Jae Lee, Jae-Wook Kang, Sanghun Jeon
Paper-based electronic devices are attracting considerable attention, because the paper platform has unique attributes such as flexibility and eco-friendliness. Here we report on what is claimed to be the firstly fully integrated vertically-stacked nanocellulose-based tactile sensor, which is capable of simultaneously sensing temperature and pressure. The pressure and temperature sensors are operated using different principles and are stacked vertically, thereby minimizing the interference effect. For the pressure sensor, which utilizes the piezoresistance principle under pressure, the conducting electrode was inkjet printed on the TEMPO-oxidized-nanocellulose patterned with micro-sized pyramids, and the counter electrode was placed on the nanocellulose film...
November 16, 2017: Nanoscale
Cheng-Lun Hsin, Yu-Ting Liu, Yue-Yun Tsai
Thermal conductivity is an intriguing physical property in the nanometer or quantum regime. In this study, we report the growth and thermal conductivity of β-FeSi2 thin film and single crystalline nanowires. The sample structures and chemical composition were identified by standard microscopy techniques. The temperature-dependent thermal conductivity of the thin film was measured by the 3ω method, whereas that of the nanowires was conducted by a suspended pattern technique. Temperature-dependent thermal conductivity was found to increase gradually from 300 to 500 K due to the effect of surface scattering...
November 6, 2017: Nanotechnology
Guodong Li, Umut Aydemir, Bo Duan, Matthias T Agne, Hongtao Wang, Max Wood, Qingjie Zhang, Pengcheng Zhai, William A Goddard, G Jeffrey Snyder
Both n- and p-type lead telluride (PbTe)-based thermoelectric (TE) materials display high TE efficiency, but the low fracture strength may limit their commercial applications. To find ways to improve these macroscopic mechanical properties, we report here the ideal strength and deformation mechanism of PbTe using density functional theory calculations. This provides structure-property relationships at the atomic scale that can be applied to estimate macroscopic mechanical properties such as fracture toughness...
November 13, 2017: ACS Applied Materials & Interfaces
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