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Giuseppe Romano, Alexie M Kolpak
Boundary-engineering in nanostructures has the potential to dramatically impact the development of materials for high- efficiency conversion of thermal energy directly into electricity. In particular, nanostructuring of semiconductors can lead to strong suppression of heat transport with little degradation of electrical conductivity. Although this combination of material properties is promising for thermoelectric materials, it remains largely unexplored. In this work, we introduce a novel concept, the directional phonon suppression function, to unravel boundary-dominated heat transport in unprecedented detail...
March 24, 2017: Scientific Reports
Wenbin Zhou, Qingxia Fan, Qiang Zhang, Le Cai, Kewei Li, Xiaogang Gu, Feng Yang, Nan Zhang, Yanchun Wang, Huaping Liu, Weiya Zhou, Sishen Xie
It is a great challenge to substantially improve the practical performance of flexible thermoelectric modules due to the absence of air-stable n-type thermoelectric materials with high-power factor. Here an excellent flexible n-type thermoelectric film is developed, which can be conveniently and rapidly prepared based on the as-grown carbon nanotube continuous networks with high conductivity. The optimum n-type film exhibits ultrahigh power factor of ∼1,500 μW m(-1) K(-2) and outstanding stability in air without encapsulation...
March 24, 2017: Nature Communications
H Balout, P Boulet, M-C Record
The present theoretical study, performed using density-functional theory and Boltzmann transport theory formalisms, shows that under 2.246 % isotropic tensile strain, the two energy-lowest conduction bands of Mg2Si overlap. The two, threefold-degenerated orbitals become a unique, sixfold-degenerated orbital. It is demonstrated that such degeneracy implies an increase of the Seebeck coefficient, of the electrical conductivity, of the power factor, and in fine of the figure of merit.
April 2017: Journal of Molecular Modeling
Fabienne Michelini, Adeline Crépieux, Katawoura Beltako
We discuss some thermodynamic aspects of energy conversion in electronic nanosystems able to convert light energy into electrical or/and thermal energy using the non-equilibrium Green's function formalism. In a first part, we derive the photon energy and particle currents inside a nanosystem interacting with light and in contact with two electron reservoirs at different temperatures. Energy conservation is verified, and radiation laws are discussed from electron non-equilibrium Green's functions. We further use the photon currents to formulate the rate of entropy production for steady-state nanosystems, and we recast this rate in terms of efficiency for specific photovoltaic-thermoelectric nanodevices...
March 23, 2017: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Xingxing Xiao, Marc Widenmeyer, Wenjie Xie, Tianhua Zou, Songhak Yoon, Marco Scavini, Stefano Checchia, Zhicheng Zhong, Philipp Hansmann, Stefan Kilper, Andrei Kovalevsky, Anke Weidenkaff
A series of Ba1-xEuxTiO3-δ (0.1 ≤ x ≤ 0.9) phases with ∼40 nm particle size were synthesized via a Pechini method followed by annealing and sintering under a reducing atmosphere. The effects of Eu(2+) substitution on the BaTiO3 crystal structure and the thermoelectric transport properties were systematically investigated. According to synchrotron X-ray diffraction data only cubic perovskite structures were observed. On the local scale below about 20 Å (equal to ∼5 unit cells) deviations from the cubic structure model (Pm3[combining macron]m) were detected by evaluation of the pair distribution function (PDF)...
March 23, 2017: Physical Chemistry Chemical Physics: PCCP
Maureen J Lagos, Andreas Trügler, Ulrich Hohenester, Philip E Batson
Imaging of vibrational excitations in and near nanostructures is essential for developing low-loss infrared nanophotonics, controlling heat transport in thermal nanodevices, inventing new thermoelectric materials and understanding nanoscale energy transport. Spatially resolved electron energy loss spectroscopy has previously been used to image plasmonic behaviour in nanostructures in an electron microscope, but hitherto it has not been possible to map vibrational modes directly in a single nanostructure, limiting our understanding of phonon coupling with photons and plasmons...
March 22, 2017: Nature
Thomas J Salez, Bo Tao Huang, Maud Rietjens, Marco Bonetti, Cécile Wiertel-Gasquet, Michel Roger, Cleber Lopes Filomeno, Emmanuelle Dubois, Régine Perzynski, Sawako Nakamae
Currently, liquid thermocells are receiving increasing attention as an inexpensive alternative to conventional solid-state thermoelectrics for low-grade waste heat recovery applications. Here we present a novel path to increase the Seebeck coefficient of liquid thermoelectric materials using charged colloidal suspensions; namely, ionically stabilized magnetic nanoparticles (ferrofluids) dispersed in aqueous potassium ferro-/ferri-cyanide electrolytes. The dependency of thermoelectric potential on experimental parameters such as nanoparticle concentration and types of solute ions (lithium citrate and tetrabutylammonium citrate) is examined to reveal the relative contributions from the thermogalvanic potential of redox couples and the entropy of transfer of nanoparticles and ions...
March 22, 2017: Physical Chemistry Chemical Physics: PCCP
Chia-Chi Yu, Hsin-Jay Wu, Ping-Yuan Deng, Matthias T Agne, G Jeffrey Snyder, Jinn P Chu
The thermal stability of joints in thermoelectric (TE) modules, which are degraded during interdiffusion between the TE material and the contacting metal, needs to be addressed in order to utilize TE technology for competitive, sustainable energy applications. Herein, we deposit a 200 nm-thick Zr-based thin-film metallic glass (TFMG), which acts as an effective diffusion barrier layer with low electrical contact resistivity, on a high-zT Se-doped AgSbTe2 substrate. The reaction couples structured with TFMG/TE are annealed at 673 K for 8-360 hours and analyzed by electron microscopy...
March 22, 2017: Scientific Reports
Silvia Di Lecce, Tim Albrecht, Fernando Bresme
Thermal gradients induce concentration gradients in alkali halide solutions, and the salt migrates towards hot or cold regions depending on the average temperature of the solution. This effect has been interpreted using the heat of transport, which provides a route to rationalize thermophoretic phenomena. Early theories provide estimates of the heat of transport at infinite dilution. These values are used to interpret thermodiffusion (Soret) and thermoelectric (Seebeck) effects. However, accessing heats of transport of individual ions at finite concentration remains an outstanding question both theoretically and experimentally...
March 21, 2017: Scientific Reports
Benoît Boucher, Rabih Al Rahal Al Orabi, Bruno Fontaine, Yuri Grin, Régis Gautier, Jean-François Halet
The possible existence of group 6 TM3 compounds with T = Cr, Mo, W and M = Ga, In is investigated with the aid of density functional theory calculations. Their most probable crystal structure is expected to be of the FeGa3 type tetragonal space group P42/mnm. All compounds are computed to be semiconductors with a band gap ranging from 0.08 to 0.43 eV, at the modified Becke-Johnson level of theory. The thermoelectric properties are analyzed via calculations based on Boltzmann transport equation under a constant relaxation time approximation...
March 20, 2017: Inorganic Chemistry
Haldun Sevincli
The critical points and the corresponding singularities in the density of states of crystals were first classified by Van Hove with respect to their dimensionality and energy-momentum dispersions. Here, different from saddle-point Van Hove singularities, the occurrence of a continuum of critical points, which give rise to strong singularities in two-dimensional elemental hexagonal lattices, is shown using a minimal tight-binding formalism. The model predicts quartic energy-momentum dispersions in spite of quadratic or linear ones, which is also the origin of the strong singularity...
March 20, 2017: Nano Letters
Xiaolong Xu, Qingjun Song, Haifeng Wang, Pan Li, Kun Zhang, Yilun Wang, Kai Yuan, Zichen Yang, Yu Ye, Lun Dai
The group IV-VI compound tin selenide (SnSe) has recently attracted particular interest due to its unexpectedly low thermal conductivity and high power factor, showing great promise for thermoelectric applications. With an orthorhombic lattice structure, SnSe displays intriguing anisotropic properties due to the low symmetry of the puckered in-plane lattice structure. When thermoelectric materials, like SnSe, have decreased dimensionality, their thermoelectric conversion efficiency may be improved due to increased power factor and decreased thermal conductivity...
March 20, 2017: ACS Applied Materials & Interfaces
Chaohua Zhang, Hongkuan Ng, Zhong Li, Khiam Aik Khor, Qihua Xiong
Minority carrier blocking through hetero-interfaces barriers has been theoretically proposed to enhance the thermoelectric figure of merit ZT of bismuth telluride based nanocomposites at elevated temperatures recently (Phys. Rev. B 2016, 93, 165209). Here, to experimentally realize this strategy, liquid-phase sintering process enabled by excess Te is applied to the solution-processed BixSb2-xTe3 nanocomposites for introducing interfacial energy barriers. The controlling parameters in the liquid-phase sintering process such as the amount of excess Te, sintering temperature and holding time, and the Bi composition (x) are systemically tuned and investigated to thoroughly understand the minority carrier blocking mechanism...
March 20, 2017: ACS Applied Materials & Interfaces
In Hwan Jung, Cheon Taek Hong, Un-Hak Lee, Young Hun Kang, Kwang-Suk Jang, Song Yun Cho
We studied the thermoelectric properties of a diketopyrrolopyrrole-based semiconductor (PDPP3T) via a precisely tuned doping process using Iron (III) chloride. In particular, the doping states of PDPP3T film were linearly controlled depending on the dopant concentration. The outstanding Seebeck coefficient of PDPP3T assisted the excellent power factors (PFs) over 200 μW m(-1)K(-2) at the broad range of doping concentration (3-8 mM) and the maximum PF reached up to 276 μW m(-1)K(-2), which is much higher than that of poly(3-hexylthiophene), 56 μW m(-1)K(-2)...
March 20, 2017: Scientific Reports
Shrikant Saini, Haritha Sree Yaddanapudi, Kun Tian, Yinong Yin, David Magginetti, Ashutosh Tiwari
The potential of thermoelectric materials to generate electricity from the waste heat can play a key role in achieving a global sustainable energy future. In order to proceed in this direction, it is essential to have thermoelectric materials that are environmentally friendly and exhibit high figure of merit, ZT. Oxide thermoelectric materials are considered ideal for such applications. High thermoelectric performance has been reported in single crystals of Ca3Co4O9. However, for large scale applications single crystals are not suitable and it is essential to develop high-performance polycrystalline thermoelectric materials...
March 20, 2017: Scientific Reports
Ekaterina A Dolgopolova, Amy J Brandt, Otega Ejegbavwo, Audrey S Duke, Thathsara D Maddumapatabandi, Randima P Galhenage, Bryon W Larson, Obadiah Reid, Salai Cheettu Ammal, Andreas Heyden, Mvs Chandrashekhar, Vitalie Stavila, Donna A Chen, Natalia B Shustova
Development of porous well-defined hybrid materials (e.g., metal-organic frameworks (MOFs)) will add a new dimension to a wide number of applications ranging from supercapacitors and electrodes to "smart" membranes and thermoelectrics. From this perspective, understanding and tailoring electronic properties of MOFs is a key fundamental challenge that could unlock the full potential of these materials. In this work, we focused on the fundamental insights responsible for the electronic properties of three distinct classes of bimetallic systems, Mx-yM'y-MOFs, MxM'y-MOFs, and Mx(ligand-M'y)-MOFs, in which the second metal (M') incorporation occurs through: (i) metal (M) replacement in the framework nodes (type I), (ii) metal node extension (type II), and (iii) metal coordination to the organic ligand (type III), respectively...
March 18, 2017: Journal of the American Chemical Society
Zi-Zhen Lin, Cong-Liang Huang, Wen-Kai Zhen, Yan-Hui Feng, Xin-Xin Zhang, Ge Wang
The hot-wire method is applied in this paper to probe the thermal conductivity (TC) of Cu and Ni nanoparticle packed beds (NPBs). A different decrease tendency of TC versus porosity than that currently known is discovered. The relationship between the porosity and nanostructure is investigated to explain this unusual phenomenon. It is found that the porosity dominates the TC of the NPB in large porosities, while the TC depends on the contact area between nanoparticles in small porosities. Meanwhile, the Vickers hardness (HV) of NPBs is also measured...
December 2017: Nanoscale Research Letters
Ching-Hwa Ho, Ya-Han Chen, Yung-Kang Kuo, C W Liu
The semiconductor optoelectronic properties of an inorganic (Bi(Bi2S3)9I3)2/3 hexagonal nano-/micro-rod are firstly explored herein. Transmittance and thermoreflectance measurements show that (Bi(Bi2S3)9I3)2/3 hexagonal rods possess an indirect gap of 0.73 eV and a direct gap of 1.08 eV, respectively. Hot-probe measurements of (Bi(Bi2S3)9I3)2/3 reveal the p-type semiconductor behavior and high thermoelectric voltage. Polarized Raman measurements of the m-plane (Bi(Bi2S3)9I3)2/3 (along c and perpendicular to the c axis) identify the structural anisotropy of the hexagonal nano-/micro-rod...
March 16, 2017: Chemical Communications: Chem Comm
Er-Tao Hu, Yuan Yao, Kai-Yan Zang, Xin-Xing Liu, An-Qing Jiang, Jia-Jin Zheng, Ke-Han Yu, Wei Wei, Yu-Xiang Zheng, Rong-Jun Zhang, Song-You Wang, Hai-Bin Zhao, Osamu Yoshie, Young-Pak Lee, Cai-Zhuang Wang, David W Lynch, Jun-Peng Guo, Liang-Yao Chen
In this work, 4-layered SiO2/Bi2Te3/SiO2/Cu film structures were designed and fabricated and the optical properties investigated in the wavelength region of 250-1200 nm for their promising applications for direct solar-thermal-electric conversion. A typical 4-layered film sample with the structure SiO2 (66.6 nm)/Bi2Te3 (7.0 nm)/SiO2 (67.0 nm)/Cu (>100.0 nm) was deposited on a Si or K9-glass substrate by magnetron sputtering. The experimental results agree well with the simulated ones showing an average optical absorption of 96...
March 16, 2017: Scientific Reports
Zhenzhen Qin, Guangzhao Qin, Xu Zuo, Zhihua Xiong, Ming Hu
Two-dimensional (2D) materials with graphene as a representative have been intensively studied for a long time. Recently, monolayer gallium nitride (ML GaN) with honeycomb structure was successfully fabricated in experiments, generating enormous research interest for its promising applications in nano- and opto-electronics. Considering all these applications are inevitably involved with thermal transport, systematic investigation of the phonon transport properties of 2D GaN is in demand. In this paper, by solving the Boltzmann transport equation (BTE) based on first-principles calculations, we performed a comprehensive study of the phonon transport properties of ML GaN, with detailed comparison to bulk GaN, 2D graphene, silicene and ML BN with similar honeycomb structure...
March 15, 2017: Nanoscale
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