Sample records for enhanced thermoelectric performance

  1. Superparamagnetic enhancement of thermoelectric performance.

    PubMed

    Zhao, Wenyu; Liu, Zhiyuan; Sun, Zhigang; Zhang, Qingjie; Wei, Ping; Mu, Xin; Zhou, Hongyu; Li, Cuncheng; Ma, Shifang; He, Danqi; Ji, Pengxia; Zhu, Wanting; Nie, Xiaolei; Su, Xianli; Tang, Xinfeng; Shen, Baogen; Dong, Xiaoli; Yang, Jihui; Liu, Yong; Shi, Jing

    2017-09-13

    The ability to control chemical and physical structuring at the nanometre scale is important for developing high-performance thermoelectric materials. Progress in this area has been achieved mainly by enhancing phonon scattering and consequently decreasing the thermal conductivity of the lattice through the design of either interface structures at nanometre or mesoscopic length scales or multiscale hierarchical architectures. A nanostructuring approach that enables electron transport as well as phonon transport to be manipulated could potentially lead to further enhancements in thermoelectric performance. Here we show that by embedding nanoparticles of a soft magnetic material in a thermoelectric matrix we achieve dual control of phonon- and electron-transport properties. The properties of the nanoparticles-in particular, their superparamagnetic behaviour (in which the nanoparticles can be magnetized similarly to a paramagnet under an external magnetic field)-lead to three kinds of thermoelectromagnetic effect: charge transfer from the magnetic inclusions to the matrix; multiple scattering of electrons by superparamagnetic fluctuations; and enhanced phonon scattering as a result of both the magnetic fluctuations and the nanostructures themselves. We show that together these effects can effectively manipulate electron and phonon transport at nanometre and mesoscopic length scales and thereby improve the thermoelectric performance of the resulting nanocomposites.

  2. Enhanced thermoelectric performance of graphene nanoribbon-based devices

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Hossain, Md Sharafat, E-mail: hossain@student.unimelb.edu.au; Huynh, Duc Hau; Nguyen, Phuong Duc

    There have been numerous theoretical studies on exciting thermoelectric properties of graphene nano-ribbons (GNRs); however, most of these studies are mainly based on simulations. In this work, we measure and characterize the thermoelectric properties of GNRs and compare the results with theoretical predictions. Our experimental results verify that nano-structuring and patterning graphene into nano-ribbons significantly enhance its thermoelectric power, confirming previous predictions. Although patterning results in lower conductance (G), the overall power factor (S{sup 2}G) increases for nanoribbons. We demonstrate that edge roughness plays an important role in achieving such an enhanced performance and support it through first principles simulations.more » We show that uncontrolled edge roughness, which is considered detrimental in GNR-based electronic devices, leads to enhanced thermoelectric performance of GNR-based thermoelectric devices. The result validates previously reported theoretical studies of GNRs and demonstrates the potential of GNRs for the realization of highly efficient thermoelectric devices.« less

  3. Investigating enhanced thermoelectric performance of graphene-based nano-structures.

    PubMed

    Hossain, Md Sharafat; Huynh, Duc Hau; Jiang, Liming; Rahman, Sharmin; Nguyen, Phuong Duc; Al-Dirini, Feras; Hossain, Faruque; Bahk, Je-Hyeong; Skafidas, Efstratios

    2018-03-08

    Recently, it has been demonstrated that graphene nano-ribbons (GNRs) exhibit superior thermoelectric performance compared to graphene sheets. However, the underlying mechanism behind this enhancement has not been systematically investigated and significant opportunity remains for further enhancement of the thermoelectric performance of GNRs by optimizing their charge carrier concentration. In this work, we modulate the carrier concentration of graphene-based nano-structures using a gate voltage and investigate the resulting carrier-concentration-dependent thermoelectric parameters using the Boltzmann transport equations. We investigate the effect of energy dependent scattering time and the role of substrate-induced charge carrier fluctuation in optimizing the Seebeck coefficient and power factor. Our approach predicts the scattering mechanism and the extent of the charge carrier fluctuation in different samples and explains the enhancement of thermoelectric performance of GNR samples. Subsequently, we propose a route towards the enhancement of thermoelectric performance of graphene-based devices which can also be applied to other two-dimensional materials.

  4. Enhanced thermoelectric performance of defected silicene nanoribbons

    NASA Astrophysics Data System (ADS)

    Zhao, W.; Guo, Z. X.; Zhang, Y.; Ding, J. W.; Zheng, X. J.

    2016-02-01

    Based on non-equilibrium Green's function method, we investigate the thermoelectric performance for both zigzag (ZSiNRs) and armchair (ASiNRs) silicene nanoribbons with central or edge defects. For perfect silicene nanoribbons (SiNRs), it is shown that with its width increasing, the maximum of ZT values (ZTM) decreases monotonously while the phononic thermal conductance increases linearly. For various types of edges and defects, with increasing defect numbers in longitudinal direction, ZTM increases monotonously while the phononic thermal conductance decreases. Comparing with ZSiNRs, defected ASiNRs possess higher thermoelectric performance due to higher Seebeck coefficient and lower thermal conductance. In particular, about 2.5 times enhancement to ZT values is obtained in ASiNRs with edge defects. Our theoretical simulations indicate that by controlling the type and number of defects, ZT values of SiNRs could be enhanced greatly which suggests their very appealing thermoelectric applications.

  5. Enhancing Thermoelectric Performance Using Nonlinear Transport Effects

    NASA Astrophysics Data System (ADS)

    Jiang, Jian-Hua; Imry, Yoseph

    2017-06-01

    We study nonlinear transport effects on the maximum efficiency and power for both inelastic and elastic thermoelectric generators. The former device refers to phonon-assisted hopping in double quantum dots, while the latter device is represented by elastic tunneling through a single quantum dot. We find that nonlinear thermoelectric transport can lead to enhanced efficiency and power for both types of devices. A comprehensive survey of various quantum-dot energy, temperature, and parasitic heat conduction reveals that the nonlinear transport-induced improvements of the maximum efficiency and power are overall much more significant for inelastic devices than for elastic devices, even for temperature biases as small as Th=1.2 Tc (Th and Tc are the temperatures of the hot and cold reservoirs, respectively). The underlying mechanism is revealed as due to the fact that, unlike the Fermi distribution, the Bose distribution is not bounded when the temperature bias increases. A large flux density of absorbed phonons leads to a great enhancement of the electrical current, output power, and energy efficiency, dominating over the concurrent increase of the parasitic heat current. Our study reveals that nonlinear transport effects can be a useful tool for improving thermoelectric performance.

  6. Remarkable enhancement in thermoelectric performance of BiCuSeO through biaxial strain modulation

    NASA Astrophysics Data System (ADS)

    Li, Chunhong; Guo, Donglin; Li, Kejian; Shao, Bin; Chen, Dengming; Ma, Yilong; Sun, Jianchun

    2018-03-01

    We propose to further enhance the thermoelectric performance of BiCuSeO using the biaxial strain. The effect of biaxial strain on the thermoelectric property of BiCuSeO is investigated by using the first-principles calculations combined with the Semiclaasical Boltzmann theory. When the biaxial strain is applied, the Seebeck coefficient is largely enhanced by tensile strain, while the electrical conductivity can be greatly enhanced by compressive strain. The largest zT value of 1.7 at 900 K is then conservatively estimated by using the experimental thermal conductivity, which is 4 times larger than that without biaxial strain. Our results indicate that the biaxial strain could be an effect method to enhance the thermoelectric performance of BiCuSeO.

  7. Using Thermoelectric Coolers to Enhance Loop Heat Pipe Performance

    NASA Technical Reports Server (NTRS)

    Ku, Jentung; Butler, Dan; Ottenstein, Laura; Birur, Gajanana

    2005-01-01

    Contents include the following: Loop Heat Pipe (LHP) operating temperature. LHP start-up issues. How Thermoelectric Cooler (TECs) can enhance LHP performance: start-up; operating temperature control. Experimental studies: LHP with one evaporator and one condenser; LHP with two evaporators and two condensers. Conclusion.

  8. Enhanced thermoelectric performance in three-dimensional superlattice of topological insulator thin films.

    PubMed

    Fan, Zheyong; Zheng, Jiansen; Wang, Hui-Qiong; Zheng, Jin-Cheng

    2012-10-16

    We show that certain three-dimensional (3D) superlattice nanostructure based on Bi2Te3 topological insulator thin films has better thermoelectric performance than two-dimensional (2D) thin films. The 3D superlattice shows a predicted peak value of ZT of approximately 6 for gapped surface states at room temperature and retains a high figure of merit ZT of approximately 2.5 for gapless surface states. In contrast, 2D thin films with gapless surface states show no advantage over bulk Bi2Te3. The enhancement of the thermoelectric performance originates from a combination of the reduction of lattice thermal conductivity by phonon-interface scattering, the high mobility of the topologically protected surface states, the enhancement of Seebeck coefficient, and the reduction of electron thermal conductivity by energy filtering. Our study shows that the nanostructure design of topological insulators provides a possible new way of ZT enhancement.

  9. Enhanced thermoelectric performance in three-dimensional superlattice of topological insulator thin films

    PubMed Central

    2012-01-01

    We show that certain three-dimensional (3D) superlattice nanostructure based on Bi2Te3 topological insulator thin films has better thermoelectric performance than two-dimensional (2D) thin films. The 3D superlattice shows a predicted peak value of ZT of approximately 6 for gapped surface states at room temperature and retains a high figure of merit ZT of approximately 2.5 for gapless surface states. In contrast, 2D thin films with gapless surface states show no advantage over bulk Bi2Te3. The enhancement of the thermoelectric performance originates from a combination of the reduction of lattice thermal conductivity by phonon-interface scattering, the high mobility of the topologically protected surface states, the enhancement of Seebeck coefficient, and the reduction of electron thermal conductivity by energy filtering. Our study shows that the nanostructure design of topological insulators provides a possible new way of ZT enhancement. PMID:23072433

  10. Enhanced thermoelectric performance in the Rashba semiconductor BiTeI through band gap engineering.

    PubMed

    Wu, Lihua; Yang, Jiong; Zhang, Tiansong; Wang, Shanyu; Wei, Ping; Zhang, Wenqing; Chen, Lidong; Yang, Jihui

    2016-03-02

    Rashba semiconductors are of great interest in spintronics, superconducting electronics and thermoelectrics. Bulk BiTeI is a new Rashba system with a giant spin-split band structure. 2D-like thermoelectric response has been found in BiTeI. However, as optimizing the carrier concentration, the bipolar effect occurs at elevated temperature and deteriorates the thermoelectric performance of BiTeI. In this paper, band gap engineering in Rashba semiconductor BiTeI through Br-substitution successfully reduces the bipolar effect and improves the thermoelectric properties. By utilizing the optical absorption and Burstein-Moss-effect analysis, we find that the band gap in Rashba semiconductor BiTeI increases upon bromine substitution, which is consistent with theoretical predictions. Bipolar transport is mitigated due to the larger band gap, as the thermally-activated minority carriers diminish. Consequently, the Seebeck coefficient keeps increasing with a corresponding rise in temperature, and thermoelectric performance can thus be enhanced with a ZT  =  0.5 at 570 K for BiTeI0.88Br0.12.

  11. High Performance Oxides-Based Thermoelectric Materials

    NASA Astrophysics Data System (ADS)

    Ren, Guangkun; Lan, Jinle; Zeng, Chengcheng; Liu, Yaochun; Zhan, Bin; Butt, Sajid; Lin, Yuan-Hua; Nan, Ce-Wen

    2015-01-01

    Thermoelectric materials have attracted much attention due to their applications in waste-heat recovery, power generation, and solid state cooling. In comparison with thermoelectric alloys, oxide semiconductors, which are thermally and chemically stable in air at high temperature, are regarded as the candidates for high-temperature thermoelectric applications. However, their figure-of-merit ZT value has remained low, around 0.1-0.4 for more than 20 years. The poor performance in oxides is ascribed to the low electrical conductivity and high thermal conductivity. Since the electrical transport properties in these thermoelectric oxides are strongly correlated, it is difficult to improve both the thermoelectric power and electrical conductivity simultaneously by conventional methods. This review summarizes recent progresses on high-performance oxide-based thermoelectric bulk-materials including n-type ZnO, SrTiO3, and In2O3, and p-type Ca3Co4O9, BiCuSeO, and NiO, enhanced by heavy-element doping, band engineering and nanostructuring.

  12. Convergence of separate orbits for enhanced thermoelectric performance of layered ZrS2

    NASA Astrophysics Data System (ADS)

    Ding, Guangqian; Chen, Jinfeng; Yao, Kailun; Gao, Guoying

    2017-07-01

    Minimizing the band splitting energy to approach orbital degeneracy has been shown as a route to improved thermoelectric performance. This represents an open opportunity in some promising layered materials where there is a separation of p orbitals at the valence band edge due to the crystal field splitting. In this work, using ab initio calculations and semiclassical Boltzmann transport theory, we try to figure out how orbital degeneracy influences the thermoelectric properties of layered transition-metal dichalcogenide ZrS2. We tune the splitting energy by applying compressive biaxial strain, and find out that near-degeneration at the {{Γ }} point can be achieved for around 3% strain. As expected, the enhanced density-of-states effective mass results in an increased power factor. Interestingly, we also find a marked decline in the lattice thermal conductivity due to the effect of strain on phonon velocities and scattering. The two effects synergetically enhance the figure of merit. Our results highlight the convenience of exploring this optimization route in layered thermoelectric materials with band structures similar to that of ZrS2.

  13. Enhancing Thermoelectric Performance of PbSe by Se Vacancies

    NASA Astrophysics Data System (ADS)

    Liu, Yefeng; You, Li; Wang, Chenyang; Zhang, Jiye; Yang, Jiong; Guo, Kai; Luo, Jun; Zhang, Wenqing

    2018-02-01

    Self-doped n-type PbSe1-δ thermoelectric compounds have been successfully synthesized by the melting and annealing method. The Se vacancies are created by intentionally produced deficiency of Se elements during the sample preparation. Such intrinsic doping can raise the electron concentration to a value as high as 1.2 × 1019 cm-3, leading to greatly improved electrical conductivity and power factor in the n-type PbSe1-δ . Furthermore, the presence of Se vacancies effectively enhances the phonon scattering, resulting in reduced lattice thermal conductivity. Thus, the thermoelectric performance of n-type PbSe1-δ is significantly improved by the formation of intrinsic Se vacancies. The achieved ZT value for the Se-vacancy-rich sample varies from ˜ 0.4 at 330 K to ˜ 1.0 at 675 K, which is comparable to those of the reported n-type PbSe materials with extrinsic doping. In addition, the average ZT of our n-type PbSe system reaches 0.77, which approaches the value of p-type PbTe.

  14. Realizing p-Type MoS2 with Enhanced Thermoelectric Performance by Embedding VMo2S4 Nanoinclusions.

    PubMed

    Kong, Shuang; Wu, Tianmin; Zhuang, Wei; Jiang, Peng; Bao, Xinhe

    2018-01-18

    Two-dimensional transition-metal dichalcogenide semiconductors (TMDCs) such as MoS 2 are attracting increasing interest as thermoelectric materials owing to their abundance, nontoxicity, and promising performance. Recently, we have successfully developed n-type MoS 2 thermoelectric material via oxygen doping. Nevertheless, an efficient thermoelectric module requires both n-type and p-type materials with similar compatibility factors. Here, we present a facile approach to obtain a p-type MoS 2 thermoelectric material with a maximum figure of merit of 0.18 through the introduction of VMo 2 S 4 as a second phase by vanadium doping. VMo 2 S 4 nanoinclusions, confirmed by X-ray powder diffraction (XRD) and transmission electron microscopy (TEM) measurements, not only improve the electrical conductivity by simultaneously increasing the carrier concentration and the mobility but also result in the reduction of lattice thermal conductivity by enhancing the interface phonon scattering. Our studies not only shed new light toward improving thermoelectric performance of TMDCs by a facile elemental doping strategy but also pave the way toward thermoelectric devices based on TMDCs.

  15. Chemical Potential Tuning and Enhancement of Thermoelectric Properties in Indium Selenides.

    PubMed

    Rhyee, Jong-Soo; Kim, Jin Hee

    2015-03-20

    Researchers have long been searching for the materials to enhance thermoelectric performance in terms of nano scale approach in order to realize phonon-glass-electron-crystal and quantum confinement effects. Peierls distortion can be a pathway to enhance thermoelectric figure-of-merit ZT by employing natural nano-wire-like electronic and thermal transport. The phonon-softening known as Kohn anomaly, and Peierls lattice distortion decrease phonon energy and increase phonon scattering, respectively, and, as a result, they lower thermal conductivity. The quasi-one-dimensional electrical transport from anisotropic band structure ensures high Seebeck coefficient in Indium Selenide. The routes for high ZT materials development of In₄Se₃ - δ are discussed from quasi-one-dimensional property and electronic band structure calculation to materials synthesis, crystal growth, and their thermoelectric properties investigations. The thermoelectric properties of In₄Se₃ - δ can be enhanced by electron doping, as suggested from the Boltzmann transport calculation. Regarding the enhancement of chemical potential, the chlorine doped In₄Se₃ - δ Cl 0.03 compound exhibits high ZT over a wide temperature range and shows state-of-the-art thermoelectric performance of ZT = 1.53 at 450 °C as an n -type material. It was proven that multiple elements doping can enhance chemical potential further. Here, we discuss the recent progress on the enhancement of thermoelectric properties in Indium Selenides by increasing chemical potential.

  16. Preparation and Enhanced Thermoelectric Performance of Cu2Se-SnSe Composite Materials

    NASA Astrophysics Data System (ADS)

    Peng, Zhi; He, Danqi; Mu, Xin; Zhou, Hongyu; Li, Cuncheng; Ma, Shifang; Ji, Pengxia; Hou, Weikang; Wei, Ping; Zhu, Wanting; Nie, Xiaolei; Zhao, Wenyu

    2018-03-01

    A series of p-type xCu2Se-SnSe (x = 0%, 0.10%, 0.15%, 0.20%, and 0.25%) composite thermoelectric materials have been prepared by the combination of ultrasonic dispersion and spark plasma sintering methods. The effects of secondary phase Cu2Se on the phase composition, microstructure, and thermoelectric properties of the composites were investigated. Microstructure characterization and elemental maps indicated Cu2Se grains uniformly distributed on the boundaries of the matrix. Transport measurements demonstrated that enhancement of the power factor and reduction of the thermal conductivity can be realized simultaneously by optimizing the adding content of Cu2Se. The highest ZT value of 0.51 at 773 K was achieved for the sample with x = 0.15%, increased by 24% compared with that of the SnSe matrix. These results demonstrate that optimizing the Cu2Se content can improve the thermoelectric performance of p-type SnSe polycrystalline materials.

  17. Preparation and Enhanced Thermoelectric Performance of Cu2Se-SnSe Composite Materials

    NASA Astrophysics Data System (ADS)

    Peng, Zhi; He, Danqi; Mu, Xin; Zhou, Hongyu; Li, Cuncheng; Ma, Shifang; Ji, Pengxia; Hou, Weikang; Wei, Ping; Zhu, Wanting; Nie, Xiaolei; Zhao, Wenyu

    2018-06-01

    A series of p-type xCu2Se-SnSe ( x = 0%, 0.10%, 0.15%, 0.20%, and 0.25%) composite thermoelectric materials have been prepared by the combination of ultrasonic dispersion and spark plasma sintering methods. The effects of secondary phase Cu2Se on the phase composition, microstructure, and thermoelectric properties of the composites were investigated. Microstructure characterization and elemental maps indicated Cu2Se grains uniformly distributed on the boundaries of the matrix. Transport measurements demonstrated that enhancement of the power factor and reduction of the thermal conductivity can be realized simultaneously by optimizing the adding content of Cu2Se. The highest ZT value of 0.51 at 773 K was achieved for the sample with x = 0.15%, increased by 24% compared with that of the SnSe matrix. These results demonstrate that optimizing the Cu2Se content can improve the thermoelectric performance of p-type SnSe polycrystalline materials.

  18. Chemical Potential Tuning and Enhancement of Thermoelectric Properties in Indium Selenides

    PubMed Central

    Rhyee, Jong-Soo; Kim, Jin Hee

    2015-01-01

    Researchers have long been searching for the materials to enhance thermoelectric performance in terms of nano scale approach in order to realize phonon-glass-electron-crystal and quantum confinement effects. Peierls distortion can be a pathway to enhance thermoelectric figure-of-merit ZT by employing natural nano-wire-like electronic and thermal transport. The phonon-softening known as Kohn anomaly, and Peierls lattice distortion decrease phonon energy and increase phonon scattering, respectively, and, as a result, they lower thermal conductivity. The quasi-one-dimensional electrical transport from anisotropic band structure ensures high Seebeck coefficient in Indium Selenide. The routes for high ZT materials development of In4Se3−δ are discussed from quasi-one-dimensional property and electronic band structure calculation to materials synthesis, crystal growth, and their thermoelectric properties investigations. The thermoelectric properties of In4Se3−δ can be enhanced by electron doping, as suggested from the Boltzmann transport calculation. Regarding the enhancement of chemical potential, the chlorine doped In4Se3−δCl0.03 compound exhibits high ZT over a wide temperature range and shows state-of-the-art thermoelectric performance of ZT = 1.53 at 450 °C as an n-type material. It was proven that multiple elements doping can enhance chemical potential further. Here, we discuss the recent progress on the enhancement of thermoelectric properties in Indium Selenides by increasing chemical potential. PMID:28788002

  19. High-Performance Thermoelectric Semiconductors

    NASA Technical Reports Server (NTRS)

    Fleurial, Jean-Pierre; Caillat, Thierry; Borshchevsky, Alexander

    1994-01-01

    Figures of merit almost double current state-of-art thermoelectric materials. IrSb3 is semiconductor found to exhibit exceptional thermoelectric properties. CoSb3 and RhSb3 have same skutterudite crystallographic structure as IrSb3, and exhibit exceptional transport properties expected to contribute to high thermoelectric performance. These three compounds form solid solutions. Combination of properties offers potential for development of new high-performance thermoelectric materials for more efficient thermoelectric power generators, coolers, and detectors.

  20. Computer modeling of thermoelectric generator performance

    NASA Technical Reports Server (NTRS)

    Chmielewski, A. B.; Shields, V.

    1982-01-01

    Features of the DEGRA 2 computer code for simulating the operations of a spacecraft thermoelectric generator are described. The code models the physical processes occurring during operation. Input variables include the thermoelectric couple geometry and composition, the thermoelectric materials' properties, interfaces and insulation in the thermopile, the heat source characteristics, mission trajectory, and generator electrical requirements. Time steps can be specified and sublimation of the leg and hot shoe is accounted for, as are shorts between legs. Calculations are performed for conduction, Peltier, Thomson, and Joule heating, the cold junction can be adjusted for solar radition, and the legs of the thermoelectric couple are segmented to enhance the approximation accuracy. A trial run covering 18 couple modules yielded data with 0.3% accuracy with regard to test data. The model has been successful with selenide materials, SiGe, and SiN4, with output of all critical operational variables.

  1. WSe2 nanoribbons: new high-performance thermoelectric materials.

    PubMed

    Chen, Kai-Xuan; Luo, Zhi-Yong; Mo, Dong-Chuan; Lyu, Shu-Shen

    2016-06-28

    In this work, for the first time, we systematically investigate the ballistic transport properties of WSe2 nanoribbons using first-principles methods. Armchair nanoribbons with narrow ribbon width are mostly semiconductive but the zigzag nanoribbons are metallic. Surprisingly, an enhancement in thermoelectric performance is discovered moving from monolayers to nanoribbons, especially armchair ones. The maximum room-temperature thermoelectric figure of merit of 2.2 for an armchair nanoribbon is discovered. This may be contributed to by the effects of the disordered edges, owing to the existence of dangling bonds at the ribbon edge. H-passivation has turned out to be an effective way to stabilize the edge atoms, which enhances the thermodynamic stability of the nanoribbons. In addition, after H-passivation, all of the armchair nanoribbons exhibit semiconductive properties with similar band gaps (∼1.3 eV). Our work provides instructional theoretical evidence for the application of armchair WSe2 nanoribbons as promising thermoelectric materials. The enhancement mechanism of the disordered edge effect can also encourage further exploration to achieve outstanding thermoelectric materials.

  2. High thermoelectric performance of graphite nanofibers.

    PubMed

    Tran, Van-Truong; Saint-Martin, Jérôme; Dollfus, Philippe; Volz, Sebastian

    2018-02-22

    Graphite nanofibers (GNFs) have been demonstrated to be a promising material for hydrogen storage and heat management in electronic devices. Here, by means of first-principles and transport simulations, we show that GNFs can also be an excellent material for thermoelectric applications thanks to the interlayer weak van der Waals interaction that induces low thermal conductance and a step-like shape in the electronic transmission with mini-gaps, which are necessary ingredients to achieve high thermoelectric performance. This study unveils that the platelet form of GNFs in which graphite layers are perpendicular to the fiber axis can exhibit outstanding thermoelectric properties with a figure of merit ZT reaching 3.55 in a 0.5 nm diameter fiber and 1.1 in a 1.1 nm diameter one. Interestingly, by introducing 14 C isotope doping, ZT can even be enhanced up to more than 5, and more than 8 if we include the effect of finite phonon mean free path, which demonstrates the amazing thermoelectric potential of GNFs.

  3. High performance p-type thermoelectric materials and methods of preparation

    NASA Technical Reports Server (NTRS)

    Caillat, Thierry (Inventor); Borshchevsky, Alexander (Inventor); Fleurial, Jean-Pierre (Inventor)

    2005-01-01

    The present invention is embodied in high performance p-type thermoelectric materials having enhanced thermoelectric properties and the methods of preparing such materials. In one aspect of the invention, p-type semiconductors of formula Zn4-xAxSb3-yBy wherein 0?x?4, A is a transition metal, B is a pnicogen, and 0?y?3 are formed for use in manufacturing thermoelectric devices with substantially enhanced operating characteristics and improved efficiency. Two methods of preparing p-type Zn4Sb3 and related alloys of the present invention include a crystal growth method and a powder metallurgy method.

  4. Nanowire-based thermoelectrics

    NASA Astrophysics Data System (ADS)

    Ali, Azhar; Chen, Yixi; Vasiraju, Venkata; Vaddiraju, Sreeram

    2017-07-01

    Research on thermoelectrics has seen a huge resurgence since the early 1990s. The ability of tuning a material’s electrical and thermal transport behavior upon nanostructuring has led to this revival. Nevertheless, thermoelectric performances of nanowires and related materials lag far behind those achieved with thin-film superlattices and quantum dot-based materials. This is despite the fact that nanowires offer many distinct advantages in enhancing the thermoelectric performances of materials. The simplicity of the strategy is the first and foremost advantage. For example, control of the nanowire diameters and their surface roughnesses will aid in enhancing their thermoelectric performances. Another major advantage is the possibility of obtaining high thermoelectric performances using simpler nanowire chemistries (e.g., elemental and binary compound semiconductors), paving the way for the fabrication of thermoelectric modules inexpensively from non-toxic elements. In this context, the topical review provides an overview of the current state of nanowire-based thermoelectrics. It concludes with a discussion of the future vision of nanowire-based thermoelectrics, including the need for developing strategies aimed at the mass production of nanowires and their interface-engineered assembly into devices. This eliminates the need for trial-and-error strategies and complex chemistries for enhancing the thermoelectric performances of materials.

  5. High performance P-type thermoelectric materials and methods of preparation

    NASA Technical Reports Server (NTRS)

    Caillat, Thierry (Inventor); Borshchevsky, Alexander (Inventor); Fleurial, Jean-Pierre (Inventor)

    2002-01-01

    The present invention is embodied in high performance p-type thermoelectric materials having enhanced thermoelectric properties and the methods of preparing such materials. In one aspect of the invention, p-type semiconductors of formula Zn.sub.4-x A.sub.x Sb.sub.3-y B.sub.y wherein 0.ltoreq.x.ltoreq.4, A is a transition metal, B is a pnicogen, and 0.ltoreq.y.ltoreq.3 are formed for use in manufacturing thermoelectric devices with substantially enhanced operating characteristics and improved efficiency. Two methods of preparing p-type Zn.sub.4 Sb.sub.3 and related alloys of the present invention include a crystal growth method and a powder metallurgy method.

  6. Thermoelectric ZT enhanced by asymmetric configuration in single-molecule-magnet junctions

    NASA Astrophysics Data System (ADS)

    Niu, Pengbin; Shi, Yunlong; Sun, Zhu; Nie, Yi-Hang; Luo, Hong-Gang

    2016-02-01

    In mesoscopic devices, many factors like the Coulomb and spin interactions can enhance the thermoelectric figure of merit ZT. Here we use a system consisting of a single-molecule magnet (SMM) connected to two ferromagnetic electrodes to consider the possible enhancement effects of thermoelectric efficiency. By introducing an asymmetric configuration to the transport junction, we find that this configuration can significantly enhance the thermoelectric ZT. The optimized asymmetric thermoelectric ZT is five times that of the ZT with a symmetric configuration or non-magnetic case. Due to this asymmetry, a non-zero charge thermopower at the electron-hole symmetry point is also found. These results demonstrate that the asymmetry of the transport junction helps to enhance thermoelectric efficiency and is useful for fabricating SMM-based thermoelectric devices.

  7. Significant enhancement in thermoelectric performance of nanostructured higher manganese silicides synthesized employing a melt spinning technique.

    PubMed

    Muthiah, Saravanan; Singh, R C; Pathak, B D; Avasthi, Piyush Kumar; Kumar, Rishikesh; Kumar, Anil; Srivastava, A K; Dhar, Ajay

    2018-01-25

    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. By employing this experimental strategy, an unprecedented ZT ∼ 0.82 at 800 K was realized in spark plasma sintered 5 at% Al-doped MnSi 1.73 HMS, melt spun at an optimized high cooling rate of ∼2 × 10 7 K s -1 . This enhancement in ZT represents a ∼25% increase over the best reported values thus far for HMS and primarily originates from a nano-crystalline microstructure consisting of a HMS matrix (20-40 nm) with excess Si (3-9 nm) uniformly distributed in it. This nanostructure, resulting from the high cooling rates employed during the melt-spinning of HMS, introduces a high density of nano-crystallite boundaries in a wide spectrum of nano-scale dimensions, which scatter the low-to-mid-wavelength heat-carrying phonons. This abundant phonon scattering results in a significantly reduced thermal conductivity of ∼1.5 W m -1 K -1 at 800 K, which primarily contributes to the enhancement in ZT.

  8. High performance p-type half-Heusler thermoelectric materials

    NASA Astrophysics Data System (ADS)

    Yu, Junjie; Xia, Kaiyang; Zhao, Xinbing; Zhu, Tiejun

    2018-03-01

    Half-Heusler compounds, which possess robust mechanical strength, good high temperature thermal stability and multifaceted physical properties, have been verified as a class of promising thermoelectric materials. During the last two decades, great progress has been made in half-Heusler thermoelectrics. In this review, we summarize some representative work of p-type half-Heusler materials, the thermoelectric performance of which has been remarkably enhanced in recent years. We introduce the features of the crystal and electronic structures of half-Heusler compounds, and successful strategies for optimizing electrical and thermal transport in the p-type RFeSb (R  =  V, Nb, Ta) and MCoSb (M  =  Ti, Zr, Hf) based systems, including band engineering, the formation of solid solutions and hierarchical phonon scattering. The outlook for future research directions of half-Heusler thermoelectrics is also presented.

  9. Compositional disorder and its effect on the thermoelectric performance of Zn₃P₂ nanowire-copper nanoparticle composites.

    PubMed

    Brockway, Lance; Vasiraju, Venkata; Vaddiraju, Sreeram

    2014-03-28

    Recent studies indicated that nanowire format of materials is ideal for enhancing the thermoelectric performance of materials. Most of these studies were performed using individual nanowires as the test elements. It is not currently clear whether bulk assemblies of nanowires replicate this enhanced thermoelectric performance of individual nanowires. Therefore, it is imperative to understand whether enhanced thermoelectric performance exhibited by individual nanowires can be extended to bulk assemblies of nanowires. It is also imperative to know whether the addition of metal nanoparticle to semiconductor nanowires can be employed for enhancing their thermoelectric performance further. Specifically, it is important to understand the effect of microstructure and composition on the thermoelectric performance on bulk compound semiconductor nanowire-metal nanoparticle composites. In this study, bulk composites composed of mixtures of copper nanoparticles with either unfunctionalized or 1,4-benzenedithiol (BDT) functionalized Zn₃P₂ nanowires were fabricated and analyzed for their thermoelectric performance. The results indicated that use of BDT functionalized nanowires for the fabrication of composites leads to interface-engineered composites that have uniform composition all across their cross-section. The interface engineering allows for increasing their Seebeck coefficients and electrical conductivities, relative to the Zn₃P₂ nanowire pellets. In contrast, the use of unfunctionalized Zn₃P₂ nanowires for the fabrication of composite leads to the formation of composites that are non-uniform in composition across their cross-section. Ultimately, the composites were found to have Zn₃P₂ nanowires interspersed with metal alloy nanoparticles. Such non-uniform composites exhibited very high electrical conductivities, but slightly lower Seebeck coefficients, relative to Zn₃P₂ nanowire pellets. These composites were found to show a very high zT of 0.23 at 770

  10. High Performance Graphene Nano-ribbon Thermoelectric Devices by Incorporation and Dimensional Tuning of Nanopores

    PubMed Central

    Sharafat Hossain, Md; Al-Dirini, Feras; Hossain, Faruque M.; Skafidas, Efstratios

    2015-01-01

    Thermoelectric properties of Graphene nano-ribbons (GNRs) with nanopores (NPs) are explored for a range of pore dimensions in order to achieve a high performance two-dimensional nano-scale thermoelectric device. We reduce thermal conductivity of GNRs by introducing pores in them in order to enhance their thermoelectric performance. The electrical properties (Seebeck coefficient and conductivity) of the device usually degrade with pore inclusion; however, we tune the pore to its optimal dimension in order to minimize this degradation, enhancing the overall thermoelectric performance (high ZT value) of our device. We observe that the side channel width plays an important role to achieve optimal performance while the effect of pore length is less pronounced. This result is consistent with the fact that electronic conduction in GNRs is dominated along its edges. Ballistic transport regime is assumed and a semi-empirical method using Huckel basis set is used to obtain the electrical properties, while the phononic system is characterized by Tersoff empirical potential model. The proposed device structure has potential applications as a nanoscale local cooler and as a thermoelectric power generator. PMID:26083450

  11. High Performance Graphene Nano-ribbon Thermoelectric Devices by Incorporation and Dimensional Tuning of Nanopores.

    PubMed

    Hossain, Md Sharafat; Al-Dirini, Feras; Hossain, Faruque M; Skafidas, Efstratios

    2015-06-17

    Thermoelectric properties of Graphene nano-ribbons (GNRs) with nanopores (NPs) are explored for a range of pore dimensions in order to achieve a high performance two-dimensional nano-scale thermoelectric device. We reduce thermal conductivity of GNRs by introducing pores in them in order to enhance their thermoelectric performance. The electrical properties (Seebeck coefficient and conductivity) of the device usually degrade with pore inclusion; however, we tune the pore to its optimal dimension in order to minimize this degradation, enhancing the overall thermoelectric performance (high ZT value) of our device. We observe that the side channel width plays an important role to achieve optimal performance while the effect of pore length is less pronounced. This result is consistent with the fact that electronic conduction in GNRs is dominated along its edges. Ballistic transport regime is assumed and a semi-empirical method using Huckel basis set is used to obtain the electrical properties, while the phononic system is characterized by Tersoff empirical potential model. The proposed device structure has potential applications as a nanoscale local cooler and as a thermoelectric power generator.

  12. Current Pulses Momentarily Enhance Thermoelectric Cooling

    NASA Technical Reports Server (NTRS)

    Snyder, G. Jeffrey; Fleurial, Jean-Pierre; Caillat, Thierry; Chen, Gang; Yang, Rong Gui

    2004-01-01

    The rates of cooling afforded by thermoelectric (Peltier) devices can be increased for short times by applying pulses of electric current greater than the currents that yield maximum steady-state cooling. It has been proposed to utilize such momentary enhancements of cooling in applications in which diode lasers and other semiconductor devices are required to operate for times of the order of milliseconds at temperatures too low to be easily obtainable in the steady state. In a typical contemplated application, a semiconductor device would be in contact with the final (coldest) somewhat taller stage of a multistage thermoelectric cooler. Steady current would be applied to the stages to produce steady cooling. Pulsed current would then be applied, enhancing the cooling of the top stage momentarily. The principles of operation are straightforward: In a thermoelectric device, the cooling occurs only at a junction at one end of the thermoelectric legs, at a rate proportional to the applied current. However, Joule heating occurs throughout the device at a rate proportional to the current squared. Hence, in the steady state, the steady temperature difference that the device can sustain increases with current only to the point beyond which the Joule heating dominates. If a pulse of current greater than the optimum current (the current for maximum steady cooling) is applied, then the junction becomes momentarily cooled below its lowest steady temperature until thermal conduction brings the resulting pulse of Joule heat to the junction and thereby heats the junction above its lowest steady temperature. A theoretical and experimental study of such transient thermoelectric cooling followed by transient Joule heating in response to current pulses has been performed. The figure presents results from one of the experiments. The study established the essential parameters that characterize the pulse cooling effect, including the minimum temperature achieved, the maximum

  13. Enhanced thermoelectric properties of graphene oxide patterned by nanoroads.

    PubMed

    Zhou, Si; Guo, Yu; Zhao, Jijun

    2016-04-21

    The thermoelectric properties of two-dimensional (2D) materials are of great interest for both fundamental science and device applications. Graphene oxide (GO), whose physical properties are highly tailorable by chemical and structural modifications, is a potential 2D thermoelectric material. In this report, we pattern nanoroads on GO sheets with epoxide functionalization, and investigate their ballistic thermoelectric transport properties based on density functional theory and the nonequilibrium Green's function method. These graphene oxide nanoroads (GONRDs) are all semiconductors with their band gaps tunable by the road width, edge orientation, and the structure of the GO matrix. These nanostructures show appreciable electrical conductance at certain doping levels and enhanced thermopower of 127-287 μV K(-1), yielding a power factor 4-22 times of the graphene value; meanwhile, the lattice thermal conductance is remarkably reduced to 15-22% of the graphene value; consequently, attaining the figure of merit of 0.05-0.75. Our theoretical results are not only helpful for understanding the thermoelectric properties of graphene and its derivatives, but also would guide the theoretical design and experimental fabrication of graphene-based thermoelectric devices of high performance.

  14. Boundary Engineering for the Thermoelectric Performance of Bulk Alloys Based on Bismuth Telluride.

    PubMed

    Mun, Hyeona; Choi, Soon-Mok; Lee, Kyu Hyoung; Kim, Sung Wng

    2015-07-20

    Thermoelectrics, which transports heat for refrigeration or converts heat into electricity directly, is a key technology for renewable energy harvesting and solid-state refrigeration. Despite its importance, the widespread use of thermoelectric devices is constrained because of the low efficiency of thermoelectric bulk alloys. However, boundary engineering has been demonstrated as one of the most effective ways to enhance the thermoelectric performance of conventional thermoelectric materials such as Bi2 Te3 , PbTe, and SiGe alloys because their thermal and electronic transport properties can be manipulated separately by this approach. We review our recent progress on the enhancement of the thermoelectric figure of merit through boundary engineering together with the processing technologies for boundary engineering developed most recently using Bi2 Te3 -based bulk alloys. A brief discussion of the principles and current status of boundary-engineered bulk alloys for the enhancement of the thermoelectric figure of merit is presented. We focus mainly on (1) the reduction of the thermal conductivity by grain boundary engineering and (2) the reduction of thermal conductivity without deterioration of the electrical conductivity by phase boundary engineering. We also discuss the next potential approach using two boundary engineering strategies for a breakthrough in the area of bulk thermoelectric alloys. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Phase-Defined van der Waals Schottky Junctions with Significantly Enhanced Thermoelectric Properties.

    PubMed

    Wang, Qiaoming; Yang, Liangliang; Zhou, Shengwen; Ye, Xianjun; Wang, Zhe; Zhu, Wenguang; McCluskey, Matthew D; Gu, Yi

    2017-07-06

    We demonstrate a van der Waals Schottky junction defined by crystalline phases of multilayer In 2 Se 3 . Besides ideal diode behaviors and the gate-tunable current rectification, the thermoelectric power is significantly enhanced in these junctions by more than three orders of magnitude compared with single-phase multilayer In 2 Se 3 , with the thermoelectric figure-of-merit approaching ∼1 at room temperature. Our results suggest that these significantly improved thermoelectric properties are not due to the 2D quantum confinement effects but instead are a consequence of the Schottky barrier at the junction interface, which leads to hot carrier transport and shifts the balance between thermally and field-driven currents. This "bulk" effect extends the advantages of van der Waals materials beyond the few-layer limit. Adopting such an approach of using energy barriers between van der Waals materials, where the interface states are minimal, is expected to enhance the thermoelectric performance in other 2D materials as well.

  16. Enhancing the thermoelectric performance of gamma-graphyne nanoribbons by introducing edge disorder.

    PubMed

    Cui, Xiao; Ouyang, Tao; Li, Jin; He, Chaoyu; Tang, Chao; Zhong, Jianxin

    2018-03-07

    Structure disorder especially edge disorder is unavoidable during the fabrication of nanomaterials. In this paper, using the non-equilibrium Green's function method, we investigate the influence of edge disorder on the thermoelectric performance of gamma(γ)-graphyne nanoribbons (GYNRs). Our results show that the high Seebeck coefficient in pristine γ-GYNR could still be preserved although edge disorder is introduced into the structure. Meanwhile, in these edge-disordered nanoribbons the suppression of thermal conductance including electronic and phononic contributions outweighs the reduction of electronic conductance. These two positive effects combine together, and finally boost the thermoelectric conversion efficiency of γ-GYNRs. The thermoelectric figure of merit ZT in the edge-disordered γ-GYNRs (the length and width are about 55.68 and 1.41 nm) could approach 2.5 at room temperature, and can even reach as high as 4.0 at 700 K, which is comparable to the efficiency of conventional energy conversion methods. The findings in this paper indicate that the edge-disordered γ-GYNRs are a promising candidate for efficient thermoelectric energy conversion and thermal management of nanodevices.

  17. Optimizing the thermoelectric performance of graphene nano-ribbons without degrading the electronic properties.

    PubMed

    Tran, Van-Truong; Saint-Martin, Jérôme; Dollfus, Philippe; Volz, Sebastian

    2017-05-24

    The enhancement of thermoelectric figure of merit ZT requires to either increase the power factor or reduce the phonon conductance, or even both. In graphene, the high phonon thermal conductivity is the main factor limiting the thermoelectric conversion. The common strategy to enhance ZT is therefore to introduce phonon scatterers to suppress the phonon conductance while retaining high electrical conductance and Seebeck coefficient. Although thermoelectric performance is eventually enhanced, all studies based on this strategy show a significant reduction of the electrical conductance. In this study we demonstrate that appropriate sources of disorder, including isotopes and vacancies at lowest electron density positions, can be used as phonon scatterers to reduce the phonon conductance in graphene ribbons without degrading the electrical conductance, particularly in the low-energy region which is the most important range for device operation. By means of atomistic calculations we show that the natural electronic properties of graphene ribbons can be fully preserved while their thermoelectric efficiency is strongly enhanced. For ribbons of width M = 5 dimer lines, room-temperature ZT is enhanced from less than 0.26 to more than 2.5. This study is likely to set the milestones of a new generation of nano-devices with dual electronic/thermoelectric functionalities.

  18. Thermoelectric power factor enhancement by ionized nanoparticle scattering

    NASA Astrophysics Data System (ADS)

    Bahk, Je-Hyeong; Bian, Zhixi; Zebarjadi, Mona; Santhanam, Parthiban; Ram, Rajeev; Shakouri, Ali

    2011-08-01

    We show theoretically that the thermoelectric power factor can be enhanced in degenerate semiconductors when embedded nanoparticles donate carriers to the matrix and replace conventional impurity dopants as scattering centers. Nanoparticle scattering rates calculated by the partial wave method indicate a mobility enhancement over materials with equivalent doping by isolated ionized impurities while the Seebeck coefficient remains nearly intact. We find that the thermoelectric power factor of In0.53Ga0.47As from 300 K to 800 K is enhanced by 15% - 30% by nanoparticles 3-4 nm in diameter.

  19. Size effect in thermoelectric materials

    NASA Astrophysics Data System (ADS)

    Mao, Jun; Liu, Zihang; Ren, Zhifeng

    2016-12-01

    Thermoelectric applications have attracted increasing interest recently due to its capability of converting waste heat into electricity without hazardous emissions. Materials with enhanced thermoelectric performance have been reported in recent two decades. The revival of research for thermoelectric materials began in early 1990s when the size effect is considered. Low-dimensional materials with exceptionally high thermoelectric figure of merit (ZT) have been presented, which broke the limit of ZT around unity. The idea of size effect in thermoelectric materials even inspired the later nanostructuring and band engineering strategies, which effectively enhanced the thermoelectric performance of bulk materials. In this overview, the size effect in low-dimensional thermoelectric materials is reviewed. We first discuss the quantum confinement effect on carriers, including the enhancement of electronic density of states, semimetal to semiconductor transition and carrier pocket engineering. Then, the effect of assumptions on theoretical calculations is presented. Finally, the effect of phonon confinement and interface scattering on lattice thermal conductivity is discussed.

  20. Enhancement of thermoelectric performance in strontium titanate by praseodymium substitution

    NASA Astrophysics Data System (ADS)

    Kovalevsky, A. V.; Yaremchenko, A. A.; Populoh, S.; Weidenkaff, A.; Frade, J. R.

    2013-02-01

    In order to identify the effects of Pr additions on thermoelectric properties of strontium titanate, crystal structure, electrical and thermal conductivity, and Seebeck coefficient of Sr1-xPrxTiO3 (x = 0.02-0.30) materials were studied at 400 < T < 1180 K under highly reducing atmosphere. The mechanism of electronic transport was found to be similar up to 10% of praseodymium content, where generation of the charge carriers upon substitution resulted in significant increase of the electrical conductivity, moderate decrease in Seebeck coefficient, and general improvement of the power factor. Formation of point defects in the course of substitution led to suppression of the lattice thermal conductivity, whilst the contribution from electronic component was increasing with carrier concentration. Possible formation of layered structures and growing distortion of the perovskite lattice resulted in relatively low thermoelectric performance for Sr0.80Pr0.20TiO3 and Sr0.70Pr0.30TiO3. The maximum dimensionless figure of merit was observed for Sr0.90Pr0.10TiO3 and amounted to ˜0.23 at 670 K and ˜0.34 at 1170 K, close to the values, obtained in similar conditions for the best bulk thermoelectrics, based on rare-earth substituted SrTiO3.

  1. Entropy as a Gene-Like Performance Indicator Promoting Thermoelectric Materials.

    PubMed

    Liu, Ruiheng; Chen, Hongyi; Zhao, Kunpeng; Qin, Yuting; Jiang, Binbin; Zhang, Tiansong; Sha, Gang; Shi, Xun; Uher, Ctirad; Zhang, Wenqing; Chen, Lidong

    2017-10-01

    High-throughput explorations of novel thermoelectric materials based on the Materials Genome Initiative paradigm only focus on digging into the structure-property space using nonglobal indicators to design materials with tunable electrical and thermal transport properties. As the genomic units, following the biogene tradition, such indicators include localized crystal structural blocks in real space or band degeneracy at certain points in reciprocal space. However, this nonglobal approach does not consider how real materials differentiate from others. Here, this study successfully develops a strategy of using entropy as the global gene-like performance indicator that shows how multicomponent thermoelectric materials with high entropy can be designed via a high-throughput screening method. Optimizing entropy works as an effective guide to greatly improve the thermoelectric performance through either a significantly depressed lattice thermal conductivity down to its theoretical minimum value and/or via enhancing the crystal structure symmetry to yield large Seebeck coefficients. The entropy engineering using multicomponent crystal structures or other possible techniques provides a new avenue for an improvement of the thermoelectric performance beyond the current methods and approaches. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Stress-controlled thermoelectric module for energy harvesting and its application for the significant enhancement of the power factor of Bi2Te3-based thermoelectrics

    NASA Astrophysics Data System (ADS)

    Korobeinikov, Igor V.; Morozova, Natalia V.; Lukyanova, Lidia N.; Usov, Oleg A.; Kulbachinskii, Vladimir A.; Shchennikov, Vladimir V.; Ovsyannikov, Sergey V.

    2018-01-01

    We propose a model of a thermoelectric module in which the performance parameters can be controlled by applied tuneable stress. This model includes a miniature high-pressure anvil-type cell and a specially designed thermoelectric module that is compressed between two opposite anvils. High thermally conductive high-pressure anvils that can be made, for instance, of sintered technical diamonds with enhanced thermal conductivity, would enable efficient heat absorption or rejection from a thermoelectric module. Using a high-pressure cell as a prototype of a stress-controlled thermoelectric converter, we investigated the effect of applied high pressure on the power factors of several single-crystalline thermoelectrics, including binary p-type Bi2Te3, and multi-component (Bi,Sb)2Te3 and Bi2(Te,Se,S)3 solid solutions. We found that a moderate applied pressure of a few GPa significantly enhances the power factors of some of these thermoelectrics. Thus, they might be more efficiently utilized in stress-controlled thermoelectric modules. In the example of one of these thermoelectrics crystallizing in the same rhombohedral structure, we examined the crystal lattice stability under moderate high pressures. We uncovered an abnormal compression of the rhombohedral lattice of (Bi0.25,Sb0.75)2Te3 along the c-axis in a hexagonal unit cell, and detected two phase transitions to the C2/m and C2/c monoclinic structures above 9.5 and 18 GPa, respectively.

  3. Enhanced thermoelectric performance realized in AgBiS2 composited AgBiSe2 through indium doping and mechanical alloying

    NASA Astrophysics Data System (ADS)

    Guan, Yingdong; Huang, Yi; Wu, Di; Feng, Dan; He, Mingkai; He, Jiaqing

    2018-05-01

    AgBiSe2 is deemed as a decent candidate of state-of-arts thermoelectric lead chalcogenides due to its intrinsically low lattice thermal conductivity. In this work, we report that a peak figure of merit of ˜0.9 can be realized at 773 K in n-type AgBiSe2 when it is simultaneously doped with indium and composited with AgBiS2 through the ball milling process. The enhancement of thermoelectric performance of AgBiSe2 largely comes from the significant reduction of thermal conductivity from ˜0.5 W/mK to 0.33 W/mK at 773 K, which is the record low value ever reported in this specific system. The decrease in thermal conductivity can be ascribed to the combination of grain size reduction and enhanced alloy scattering from S-Se substitution during the high energy ball milling processes.

  4. Enhancing thermoelectric properties of organic composites through hierarchical nanostructures

    PubMed Central

    Zhang, Kun; Zhang, Yue; Wang, Shiren

    2013-01-01

    Organic thermoelectric (TE) materials are very attractive due to easy processing, material abundance, and environmentally-benign characteristics, but their potential is significantly restricted by the inferior thermoelectric properties. In this work, noncovalently functionalized graphene with fullerene by π-π stacking in a liquid-liquid interface was integrated into poly(3,4-ethylenedioxythiophene) poly(styrenesulfonate). Graphene helps to improve electrical conductivity while fullerene enhances the Seebeck coefficient and hinders thermal conductivity, resulting in the synergistic effect on enhancing thermoelectric properties. With the integration of nanohybrids, the electrical conductivity increased from ~10000 to ~70000 S/m, the thermal conductivity changed from 0.2 to 2 W·K−1m−1 while the Seebeck coefficient was enhanced by around 4-fold. As a result, nanohybrids-based polymer composites demonstrated the figure of merit (ZT) as high as 6.7 × 10−2, indicating an enhancement of more than one order of magnitude in comparison to single-phase filler-based polymer composites with ZT at the level of 10−3. PMID:24336319

  5. Strain-induced enhancement of thermoelectric performance of TiS2 monolayer based on first-principles phonon and electron band structures

    NASA Astrophysics Data System (ADS)

    Li, Guanpeng; Yao, Kailun; Gao, Guoying

    2018-01-01

    Using first-principle calculations combined with Boltzmann transport theory, we investigate the biaxial strain effect on the electronic and phonon thermal transport properties of a 1 T (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 that the band gap experiences an indirect-direct-indirect transition with increasing tensile strain. The band convergence induced by the tensile strain increases the Seebeck coefficient and the power factor, while 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. The figure of merit can reach 0.95 (0.82) at an 8 percent tensile strain for the p-type (n-type) doping, which is much larger than that without strain. The present work suggests that the TiS2 monolayer is a good candidate for 2D thermoelectric materials, and that biaxial strain is a powerful tool with which to enhance thermoelectric performance.

  6. Strain-induced enhancement of thermoelectric performance of TiS2 monolayer based on first-principles phonon and electron band structures.

    PubMed

    Li, Guanpeng; Yao, Kailun; Gao, Guoying

    2018-01-05

    Using first-principle calculations combined with Boltzmann transport theory, we investigate the biaxial strain effect on the electronic and phonon thermal transport properties of a 1 T (CdI 2 -type) structural TiS 2 monolayer, a recent experimental two-dimensional (2D) material. It is found that the electronic band structure can be effectively modulated and that the band gap experiences an indirect-direct-indirect transition with increasing tensile strain. The band convergence induced by the tensile strain increases the Seebeck coefficient and the power factor, while 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. The figure of merit can reach 0.95 (0.82) at an 8 percent tensile strain for the p-type (n-type) doping, which is much larger than that without strain. The present work suggests that the TiS 2 monolayer is a good candidate for 2D thermoelectric materials, and that biaxial strain is a powerful tool with which to enhance thermoelectric performance.

  7. Enhanced thermoelectric performance of Nb-doped SrTiO3 by nano-inclusion with low thermal conductivity

    PubMed Central

    Wang, Ning; Chen, Haijun; He, Hongcai; Norimatsu, Wataru; Kusunoki, Michiko; Koumoto, Kunihito

    2013-01-01

    Authors reported an effective path to increase the electrical conductivity while to decrease the thermal conductivity, and thus to enhance the ZT value by nano-inclusions. By this method, the ZT value of Nb-doped SrTiO3 was enhanced 9-fold by yttria stabilized zirconia (YSZ) nano-inclusions. YSZ inclusions, located inside grain and in triple junction, can reduce the thermal conductivity by effective interface phonon scattering, enhance the electrical conductivity by promoting the abnormal grain growth, and thus lead to the obvious enhancement of ZT value, which strongly suggests that, it is possible to not only reduce the thermal conductivity, but also increase the electrical conductivity by nano-inclusions with low thermal conductivity. This study will give some useful enlightenment to the preparation of high-performance oxide thermoelectric materials. PMID:24316665

  8. Thermal conductivity engineering in width-modulated silicon nanowires and thermoelectric efficiency enhancement

    NASA Astrophysics Data System (ADS)

    Zianni, Xanthippi

    2018-03-01

    Width-modulated nanowires have been proposed as efficient thermoelectric materials. Here, the electron and phonon transport properties and the thermoelectric efficiency are discussed for dimensions above the quantum confinement regime. The thermal conductivity decreases dramatically in the presence of thin constrictions due to their ballistic thermal resistance. It shows a scaling behavior upon the width-modulation rate that allows for thermal conductivity engineering. The electron conductivity also decreases due to enhanced boundary scattering by the constrictions. The effect of boundary scattering is weaker for electrons than for phonons and the overall thermoelectric efficiency is enhanced. A ZT enhancement by a factor of 20-30 is predicted for width-modulated nanowires compared to bulk silicon. Our findings indicate that width-modulated nanostructures are promising for developing silicon nanostructures with high thermoelectric efficiency.

  9. Major enhancement of the thermoelectric performance in Pr/Nb-doped SrTiO3 under strain

    NASA Astrophysics Data System (ADS)

    Amin, B.; Singh, N.; Tritt, T. M.; Alshareef, H. N.; Schwingenschlögl, U.

    2013-07-01

    The electronic structure and thermoelectric properties of strained (biaxially and uniaxially) Sr0.95Pr0.05TiO3 and SrTi0.95Nb0.05O3 are investigated in the temperature range from 300 K to 1200 K. Substitutions of Pr at the Sr site and Nb at the Ti site generate n-type doping and thus improve the thermoelectric performance as compared to pristine SrTiO3. Further enhancement is achieved by the application of strain, for example, of the Seebeck coefficient by 21% for Sr0.95Pr0.05TiO3 and 10% for SrTi0.95Nb0.05O3 at room temperature in the case of 5% biaxial strain. At 1200 K, we predict figures of merit of 0.58 and 0.55 for 2.5% biaxially strained Sr0.95Pr0.05TiO3 and SrTi0.95Nb0.05O3, respectively, which are the highest values reported for rare earth doped SrTiO3.

  10. Enhancement of Thermoelectric Properties of PEDOT:PSS and Tellurium-PEDOT:PSS Hybrid Composites by Simple Chemical Treatment.

    PubMed

    Bae, Eun Jin; Kang, Young Hun; Jang, Kwang-Suk; Cho, Song Yun

    2016-01-05

    The thermoelectric properties of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) ( PSS) and tellurium- PSS (Te- PSS) hybrid composites were enhanced via simple chemical treatment. The performance of thermoelectric materials is determined by their electrical conductivity, thermal conductivity, and Seebeck coefficient. Significant enhancement of the electrical conductivity of PSS and Te- PSS hybrid composites from 787.99 and 11.01 to 4839.92 and 334.68 S cm(-1), respectively was achieved by simple chemical treatment with H2SO4. The power factor of the developed materials could be effectively tuned over a very wide range depending on the concentration of the H2SO4 solution used in the chemical treatment. The power factors of the developed thermoelectric materials were optimized to 51.85 and 284 μW m(-1) K(-2), respectively, which represent an increase of four orders of magnitude relative to the corresponding parameters of the untreated thermoelectric materials. Using the Te- PSS hybrid composites, a flexible thermoelectric generator that could be embedded in textiles was fabricated by a printing process. This thermoelectric array generates a thermoelectric voltage of 2 mV using human body heat.

  11. Wearable and flexible thermoelectric generator with enhanced package

    NASA Astrophysics Data System (ADS)

    Francioso, L.; De Pascali, C.; Taurino, A.; Siciliano, P.; De Risi, A.

    2013-05-01

    Present work shows recent progresses in thin film-based flexible and wearable thermoelectric generator (TEG), finalized to support energy scavenging and local storage for low consumption electronics in Ambient Assisted Living (AAL) applications and buildings integration. The proposed TEG is able to recover energy from heat dispersed into the environment converting a thermal gradient to an effective electrical energy available to power ultra-low consumption devices. A low cost fabrication process based on planar thin-film technology was optimized to scale down the TEG dimensions to micrometer range. The prototype integrates 2778 thermocouples of sputtered Sb2Te3 and Bi2Te3 thin films (1 μm thick) on an area of 25 cm2. The electrical properties of thermoelectric materials were investigated by Van der Pauw measurements. Transfer Length Method (TLM) analysis was performed on three different multi-layer contact schemes in order to select the best solution to use for the definition of the contact pads realized on each section of the thermoelectric array configuration to allow electrical testing of single production areas. Kapton polyimide film was used as flexible substrate in order to add comfortable lightweight and better wearability to the device. The realized TEG is able to autonomously recover the thermal gradient useful to thermoelectric generation thanks to an appropriate package designed and optimized by a thermal analysis based on finite element method (FEM). The proposed package solution consists in coupling the module realized onto Kapton foil to a PDMS layer opportunely molded to thermally insulate TEG cold junctions and enhance the thermal gradient useful for the energy scavenging. Simulations results were compared to experimental tests performed by a thermal infrared camera, in order to evaluate the real performance of the designed package. First tests conducted on the realized TEG indicate that the prototype is able to recover about 5°C between hot and

  12. Thermoelectric-figure-of-merit enhancement of silicon-germanium through nanocomposite concept

    NASA Astrophysics Data System (ADS)

    Wang, Dezhi

    SiGe alloy has been the thermoelectric material element of RTGs (Radioisotope thermoelectric power generators) for more than 20 years because of its good performance at high temperature. It also has a very high potential application in converting exhaust heat into useful electricity, which currently attracts a lot of research interest in the automotive industry where 40% of the energy was rejected as exhaust heat. However, its low conversion efficiency (8%) is a major concern although it is the best in practice. A new concept, namely Si-Ge nanocomposite, was proposed to enhance thermoelectric figure-of-merit. Fast heating pressure sintering was found to be an appropriate synthesizing method and a lab-made direct current-induced hot press system was established. It can reach l200°C within several minutes and many parameters can be controlled. The uniquely designed graphite die assembly can stand l60MPa pressure which is better than the best commercial products (127MPa). Numerous Si-Ge nanocomposite samples were pressed using our DC hot press. Fully dense n-type Si-Ge nanocomposite samples of nanoSi80nanoGe20P were finally obtained. The nanocomposite structure was characterized via XRD, SEM, EDS, and TEM. The proposed nanocomposite structure, dots in a matrix, was observed. Most importantly, the thermoelectric property measurements showed that the Si-Ge nanocomposite of n-type nanoSi80nanoGe20 possessed higher electrical conductivity but lower thermal conductivity, thus a higher ZT than that of n-type nanoSi80microGe20. This result proved that thermoelectric-figure-of-merit enhancement through the nanocomposite concept was the right direction.

  13. Basic principles for rational design of high-performance nanostructured silicon-based thermoelectric materials.

    PubMed

    Yang, Chun Cheng; Li, Sean

    2011-12-23

    Recently, nanostructured silicon-based thermoelectric materials have drawn great attention owing to their excellent thermoelectric performance in the temperature range around 450 °C, which is eminently applicable for concentrated solar thermal technology. In this work, a unified nanothermodynamic model is developed to investigate the predominant factors that determine the lattice thermal conductivity of nanocrystalline, nanoporous, and nanostructured bulk Si. A systematic study shows that the thermoelectric performance of these materials can be substantially enhanced by the following three basic principles: 1) artificial manipulation and optimization of roughness with surface/interface patterning/engineering; 2) grain-size reduction with innovative fabrication techniques in a controllable fashion; and 3) optimization of material parameters, such as bulk solid-vapor transition entropy, bulk vibrational entropy, dimensionality, and porosity, to decrease the lattice thermal conductivity. These principles may be used to rationally design novel nanostructured Si-based thermoelectric materials for renewable energy applications. Copyright © 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Thermoelectric Performance Enhancement by Surrounding Crystalline Semiconductors with Metallic Nanoparticles

    NASA Technical Reports Server (NTRS)

    Kim, Hyun-Jung; King, Glen C.; Park, Yeonjoon; Lee, Kunik; Choi, Sang H.

    2011-01-01

    Direct conversion of thermal energy to electricity by thermoelectric (TE) devices may play a key role in future energy production and utilization. However, relatively poor performance of current TE materials has slowed development of new energy conversion applications. Recent reports have shown that the dimensionless Figure of Merit, ZT, for TE devices can be increased beyond the state-of-the-art level by nanoscale structuring of materials to reduce their thermal conductivity. New morphologically designed TE materials have been fabricated at the NASA Langley Research Center, and their characterization is underway. These newly designed materials are based on semiconductor crystal grains whose surfaces are surrounded by metallic nanoparticles. The nanoscale particles are used to tailor the thermal and electrical conduction properties for TE applications by altering the phonon and electron transport pathways. A sample of bismuth telluride decorated with metallic nanoparticles showed less thermal conductivity and twice the electrical conductivity at room temperature as compared to pure Bi2Te3. Apparently, electrons cross easily between semiconductor crystal grains via the intervening metallic nanoparticle bridges, but phonons are scattered at the interfacing gaps. Hence, if the interfacing gap is larger than the mean free path of the phonon, thermal energy transmission from one grain to others is reduced. Here we describe the design and analysis of these new materials that offer substantial improvements in thermoelectric performance.

  15. Enhancement of Thermoelectric Properties of PEDOT:PSS and Tellurium-PEDOT:PSS Hybrid Composites by Simple Chemical Treatment

    PubMed Central

    Jin Bae, Eun; Hun Kang, Young; Jang, Kwang-Suk; Yun Cho, Song

    2016-01-01

    The thermoelectric properties of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) and tellurium-PEDOT:PSS (Te-PEDOT:PSS) hybrid composites were enhanced via simple chemical treatment. The performance of thermoelectric materials is determined by their electrical conductivity, thermal conductivity, and Seebeck coefficient. Significant enhancement of the electrical conductivity of PEDOT:PSS and Te-PEDOT:PSS hybrid composites from 787.99 and 11.01 to 4839.92 and 334.68 S cm−1, respectively was achieved by simple chemical treatment with H2SO4. The power factor of the developed materials could be effectively tuned over a very wide range depending on the concentration of the H2SO4 solution used in the chemical treatment. The power factors of the developed thermoelectric materials were optimized to 51.85 and 284 μW m−1 K−2, respectively, which represent an increase of four orders of magnitude relative to the corresponding parameters of the untreated thermoelectric materials. Using the Te-PEDOT:PSS hybrid composites, a flexible thermoelectric generator that could be embedded in textiles was fabricated by a printing process. This thermoelectric array generates a thermoelectric voltage of 2 mV using human body heat. PMID:26728992

  16. Review of electronic transport models for thermoelectric materials

    NASA Astrophysics Data System (ADS)

    Bulusu, A.; Walker, D. G.

    2008-07-01

    Thermoelectric devices have gained importance in recent years as viable solutions for applications such as spot cooling of electronic components, remote power generation in space stations and satellites etc. These solid-state devices have long been known for their reliability rather than their efficiency; they contain no moving parts, and their performance relies primarily on material selection, which has not generated many excellent candidates. Research in recent years has been focused on developing both thermoelectric structures and materials that have high efficiency. In general, thermoelectric research is two-pronged with (1) experiments focused on finding new materials and structures with enhanced thermoelectric performance and (2) analytical models that predict thermoelectric behavior to enable better design and optimization of materials and structures. While numerous reviews have discussed the importance of and dependence on materials for thermoelectric performance, an overview of how to predict the performance of various materials and structures based on fundamental quantities is lacking. In this paper we present a review of the theoretical models that were developed since thermoelectricity was first observed in 1821 by Seebeck and how these models have guided experimental material search for improved thermoelectric devices. A new quantum model is also presented, which provides opportunities for the optimization of nanoscale materials to enhance thermoelectric performance.

  17. Codoping in SnTe: Enhancement of Thermoelectric Performance through Synergy of Resonance Levels and Band Convergence

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Tan, Gangjian; Shi, Fengyuan; Hao, Shiqiang

    2015-04-22

    We report a significant enhancement of the thermoelectric performance of p-type SnTe over a broad temperature plateau with a peak ZT value of similar to 1.4 at 923 K through In/Cd codoping and a CdS nanostructuring approach. Indium and cadmium play different but complementary roles in modifying the valence band structure of SnTe. Specifically, In-doping introduces resonant levels inside the valence bands, leading to a considerably improved Seebeck coefficient at low temperature. Cd-doping, however, increases the Seebeck coefficient of SnTe remarkably in the mid- to high-temperature region via a convergence of the light and heavy hole bands and an enlargementmore » of the band gap. Combining the two dopants in SnTe yields enhanced Seebeck coefficient and power factor over a wide temperature range due to the synergy of resonance levels and valence band convergence, as demonstrated by the Pisarenko plot and supported by first-principles band structure calculations. Moreover, these codoped samples can be hierarchically structured on all scales (atomic point defects by doping, nanoscale precipitations by CdS nanostructuring, and mesoscale grains by SPS treatment) to achieve highly effective phonon scattering leading to strongly reduced thermal conductivities. In addition to the high maximum ZT the resultant large average ZT of similar to 0.8 between 300 and 923 K makes SnTe an attractive p-type material for high-temperature thermoelectric power generation.« less

  18. Fundamental and progress of Bi2Te3-based thermoelectric materials

    NASA Astrophysics Data System (ADS)

    Hong, Min; Chen, Zhi-Gang; Zou, Jin

    2018-04-01

    Thermoelectric materials, enabling the directing conversion between heat and electricity, are one of the promising candidates for overcoming environmental pollution and the upcoming energy shortage caused by the over-consumption of fossil fuels. Bi2Te3-based alloys are the classical thermoelectric materials working near room temperature. Due to the intensive theoretical investigations and experimental demonstrations, significant progress has been achieved to enhance the thermoelectric performance of Bi2Te3-based thermoelectric materials. In this review, we first explored the fundamentals of thermoelectric effect and derived the equations for thermoelectric properties. On this basis, we studied the effect of material parameters on thermoelectric properties. Then, we analyzed the features of Bi2Te3-based thermoelectric materials, including the lattice defects, anisotropic behavior and the strong bipolar conduction at relatively high temperature. Then we accordingly summarized the strategies for enhancing the thermoelectric performance, including point defect engineering, texture alignment, and band gap enlargement. Moreover, we highlighted the progress in decreasing thermal conductivity using nanostructures fabricated by solution grown method, ball milling, and melt spinning. Lastly, we employed modeling analysis to uncover the principles of anisotropy behavior and the achieved enhancement in Bi2Te3, which will enlighten the enhancement of thermoelectric performance in broader materials.

  19. Enhanced thermoelectric performance in Cu-intercalated BiTeI by compensation weakening induced mobility improvement

    DOE PAGES

    Wu, Lihua; Yang, Jiong; Chi, Miaofang; ...

    2015-09-23

    The low weighted carrier mobility has long been considered to be the key challenge for improvement of thermoelectric (TE) performance in BiTeI. The Rashba-effect-induced two-dimensional density of states in this bulk semiconductor is beneficial for thermopower enhancement, which makes it a prospective compound for TE applications. In this report, we show that intercalation of minor Cu-dopants can substantially alter the equilibria of defect reactions, selectively mediate the donor-acceptor compensation, and tune the defect concentration in the carrier conductive network. Consequently, the potential fluctuations responsible for electron scattering are reduced and the carrier mobility in BiTeI can be enhanced by amore » factor of two to three between 10 K and 300 K. The carrier concentration can also be optimized by tuning the Te/I composition ratio, leading to higher thermopower in this Rashba system. Cu-intercalation in BiTeI gives rise to higher power factor, slightly lower lattice thermal conductivity, and consequently improved figure of merit. Compared with pristine BiTe 0.98I 1.02, the TE performance in Cu 0.05BiTeI reveals a 150% and 20% enhancement at 300 and 520 K, respectively. Ultimately, these results demonstrate that defect equilibria mediated by selective doping in complex TE and energy materials could be an effective approach to carrier mobility and performance optimization.« less

  20. Roles of Cu in the Enhanced Thermoelectric Properties in Bi0.5Sb1.5Te₃.

    PubMed

    Hao, Feng; Qiu, Pengfei; Song, Qingfeng; Chen, Hongyi; Lu, Ping; Ren, Dudi; Shi, Xun; Chen, Lidong

    2017-03-01

    Recently, Cu-containing p-type Bi 0.5 Sb 1.5 Te₃ materials have shown high thermoelectric performances and promising prospects for practical application in low-grade waste heat recovery. However, the position of Cu in Bi 0.5 Sb 1.5 Te₃ is controversial, and the roles of Cu in the enhancement of thermoelectric performance are still not clear. In this study, via defects analysis and stability test, the possibility of Cu intercalation in p-type Bi 0.5 Sb 1.5 Te₃ materials has been excluded, and the position of Cu is identified as doping at the Sb sites. Additionally, the effects of Cu dopants on the electrical and thermal transport properties have been systematically investigated. Besides introducing additional holes, Cu dopants can also significantly enhance the carrier mobility by decreasing the Debye screen length and weakening the interaction between carriers and phonons. Meanwhile, the Cu dopants interrupt the periodicity of lattice vibration and bring stronger anharmonicity, leading to extremely low lattice thermal conductivity. Combining the suppression on the intrinsic excitation, a high thermoelectric performance-with a maximum thermoelectric figure of merit of around 1.4 at 430 K-has been achieved in Cu 0.005 Bi 0.5 Sb 1.495 Te₃, which is 70% higher than the Bi 0.5 Sb 1.5 Te₃ matrix.

  1. Designing high-performance layered thermoelectric materials through orbital engineering

    PubMed Central

    Zhang, Jiawei; Song, Lirong; Madsen, Georg K. H.; Fischer, Karl F. F.; Zhang, Wenqing; Shi, Xun; Iversen, Bo B.

    2016-01-01

    Thermoelectric technology, which possesses potential application in recycling industrial waste heat as energy, calls for novel high-performance materials. The systematic exploration of novel thermoelectric materials with excellent electronic transport properties is severely hindered by limited insight into the underlying bonding orbitals of atomic structures. Here we propose a simple yet successful strategy to discover and design high-performance layered thermoelectric materials through minimizing the crystal field splitting energy of orbitals to realize high orbital degeneracy. The approach naturally leads to design maps for optimizing the thermoelectric power factor through forming solid solutions and biaxial strain. Using this approach, we predict a series of potential thermoelectric candidates from layered CaAl2Si2-type Zintl compounds. Several of them contain nontoxic, low-cost and earth-abundant elements. Moreover, the approach can be extended to several other non-cubic materials, thereby substantially accelerating the screening and design of new thermoelectric materials. PMID:26948043

  2. Enhanced thermoelectric efficiency of porous silicene nanoribbons.

    PubMed

    Sadeghi, Hatef; Sangtarash, Sara; Lambert, Colin J

    2015-03-30

    There is a critical need to attain new sustainable materials for direct upgrade of waste heat to electrical energy via the thermoelectric effect. Here we demonstrate that the thermoelectric performance of silicene nanoribbons can be improved dramatically by introducing nanopores and tuning the Fermi energy. We predict that values of electronic thermoelectric figure of merit ZTe up to 160 are achievable, provided the Fermi energy is located approximately 100 meV above the charge neutrality point. Including the effect of phonons yields a value for the full figure of merit of ZT = 3.5. Furthermore the sign of the thermopower S can be varied with achievable values as high as S = +/- 500 μV/K. As a method of tuning the Fermi energy, we analyse the effect of doping the silicene with either a strong electron donor (TTF) or a strong electron acceptor (TCNQ) and demonstrate that adsorbed layers of the former increases ZTe to a value of 3.1, which is insensitive to temperature over the range 100 K - 400 K. This combination of a high, temperature-insensitive ZTe, and the ability to choose the sign of the thermopower identifies nanoporous silicene as an ideal thermoelectric material with the potential for unprecedented performance.

  3. Effect of microstructure on the thermoelectric performance of La{sub 1−x}Sr{sub x}CoO{sub 3}

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Viskadourakis, Z.; Department of Mechanical and Manufacturing Engineering, University of Cypruss, 75 Kallipoleos Avenue, P.O. Box 20537, 1678 Nicosia; Athanasopoulos, G.I.

    We present a case where the microstructure has a profound effect on the thermoelectric properties of oxide compounds. Specifically, we have investigated the effect of different sintering treatments on La{sub 1−x}Sr{sub x}CoO{sub 3} samples synthesized using the Pechini method. We found that the samples, which are dense and consist of inhomogeneously-mixed grains of different size, exhibit both higher Seebeck coefficient and thermoelectric figure of merit than the samples, which are porous and consist of grains with almost identical size. The enhancement of Seebeck coefficient in the dense samples is attributed to the so-called “energy-filtering” mechanism that is related to themore » energy barrier of the grain boundary. On the other hand, the thermal conductivity for the porous compounds is significantly reduced in comparison to the dense compounds. It is suggested that a fine-manipulation of grain size ratio combined with a fine-tuning of porosity could considerably enhance the thermoelectric performance of oxides. - Graphical abstract: The enhancement of the dimensionless thermoelectric figure ZT of merit is presented for two equally Sr-doped LaCoO3 compounds, possessing different microstructure, indicating the effect of the latter to the thermoelectric performance of the La{sub 1−x}Sr{sub x}CoO{sub 3} solid solution. - Highlights: • Electrical and thermal transport properties are affected by the microstructure in La{sub 1−x}Sr{sub x}CoO{sub 3} polycrystalline materials. • Coarse/fine grain size distribution enhances the Seebeck coefficient. • Porosity reduces the thermal conductivity in La{sub 1−x}Sr{sub x}CoO{sub 3} polycrystalline samples. • The combination of large/small grain ratio distribution with the high porosity may result to the enhancement of the thermoelectric performance of the material.« less

  4. Enhanced thermoelectric performance through grain boundary engineering in quaternary chalcogenide Cu2ZnSnSe4

    NASA Astrophysics Data System (ADS)

    Zhu, Yingcai; Liu, Yong; Tan, Xing; Ren, Guangkun; Yu, Meijuan; Hu, Tiandou; Marcelli, Augusto; Xu, Wei

    2018-04-01

    Quaternary chalcogenide Cu2ZnSnSe4 (CZTSe) is a promising wide band-gap p-type thermoelectric material. The structure and thermoelectric properties of lead substituted Cu2ZnSn1-xPbxSe4 are investigated. Lead primarily exists in the framework of PbSe as demonstrated by x-ray diffraction and calculation of x-ray absorption near-edge structure spectroscopy. The second phase distributes at the boundaries of CZTSe with thickness in several hundreds of nanometer. With appropriate grain boundary engineering, the enhancement of power factor and a decrease of thermal conductivity can be achieved simultaneously. As a result, a maximum figure of merit zT of 0.45 is obtained for the sample with x=0.02 at 723K.

  5. Heavily Doped PBSE with High Thermoelectric Performance

    NASA Technical Reports Server (NTRS)

    Snyder, G. Jeffrey (Inventor); Wang, Heng (Inventor); Pei, Yanzhong (Inventor)

    2015-01-01

    The present invention discloses heavily doped PbSe with high thermoelectric performance. Thermoelectric property measurements disclosed herein indicated that PbSe is high zT material for mid-to-high temperature thermoelectric applications. At 850 K a peak zT (is) greater than 1.3 was observed when n(sub H) approximately 1.0 X 10(exp 20) cm(exp -3). The present invention also discloses that a number of strategies used to improve zT of PbTe, such as alloying with other elements, nanostructuring and band modification may also be used to further improve zT in PbSe.

  6. Lanthanide Contraction as a Design Factor for High-Performance Half-Heusler Thermoelectric Materials.

    PubMed

    Liu, Yintu; Fu, Chenguang; Xia, Kaiyang; Yu, Junjie; Zhao, Xinbing; Pan, Hongge; Felser, Claudia; Zhu, Tiejun

    2018-06-25

    Forming solid solutions, as an effective strategy to improve thermoelectric performance, has a dilemma that alloy scattering will reduce both the thermal conductivity and carrier mobility. Here, an intuitive way is proposed to decouple the opposite effects, that is, using lanthanide contraction as a design factor to select alloying atoms with large mass fluctuation but small radius difference from the host atoms. Typical half-Heusler alloys, n-type (Zr,Hf)NiSn and p-type (Nb,Ta)FeSb solid solutions, are taken as paradigms to attest the validity of this design strategy, which exhibit greatly suppressed lattice thermal conductivity and maintained carrier mobility. Furthermore, by considering lanthanide contraction, n-type (Zr,Hf)CoSb-based alloys with high zT of ≈1.0 are developed. These results highlight the significance of lanthanide contraction as a design factor in enhancing the thermoelectric performance and reveal the practical potential of (Zr,Hf)CoSb-based half-Heusler compounds due to the matched n-type and p-type thermoelectric performance. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Electron mean-free-path filtering in Dirac material for improved thermoelectric performance.

    PubMed

    Liu, Te-Huan; Zhou, Jiawei; Li, Mingda; Ding, Zhiwei; Song, Qichen; Liao, Bolin; Fu, Liang; Chen, Gang

    2018-01-30

    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. Here we report through ab initio simulations that Dirac material can overcome this limitation. The monotonically decreasing trend of the electron MFP allows filtering of long-MFP electrons that are detrimental to the Seebeck coefficient, leading to a dramatically enhanced power factor. Using SnTe as a material platform, we uncover this MFP filtering effect as arising from its unique nonparabolic Dirac band dispersion. Room-temperature zT can be enhanced by nearly a factor of 3 if one designs nanostructures with grain sizes of ∼10 nm. Our work broadens the scope of the nanostructuring approach for improving the thermoelectric performance, especially for materials with topologically nontrivial electronic dynamics.

  8. Enhanced thermoelectric efficiency via orthogonal electrical and thermal conductances in phosphorene.

    PubMed

    Fei, Ruixiang; Faghaninia, Alireza; Soklaski, Ryan; Yan, Jia-An; Lo, Cynthia; Yang, Li

    2014-11-12

    Thermoelectric devices that utilize the Seebeck effect convert heat flow into electrical energy and are highly desirable for the development of portable, solid state, passively powered electronic systems. The conversion efficiencies of such devices are quantified by the dimensionless thermoelectric figure of merit (ZT), which is proportional to the ratio of a device's electrical conductance to its thermal conductance. In this paper, a recently fabricated two-dimensional (2D) semiconductor called phosphorene (monolayer black phosphorus) is assessed for its thermoelectric capabilities. First-principles and model calculations reveal not only that phosphorene possesses a spatially anisotropic electrical conductance, but that its lattice thermal conductance exhibits a pronounced spatial-anisotropy as well. The prominent electrical and thermal conducting directions are orthogonal to one another, enhancing the ratio of these conductances. As a result, ZT may reach the criterion for commercial deployment along the armchair direction of phosphorene at T = 500 K and is close to 1 even at room temperature given moderate doping (∼2 × 10(16) m(-2) or 2 × 10(12) cm(-2)). Ultimately, phosphorene hopefully stands out as an environmentally sound thermoelectric material with unprecedented qualities. Intrinsically, it is a mechanically flexible material that converts heat energy with high efficiency at low temperatures (∼300 K), one whose performance does not require any sophisticated engineering techniques.

  9. High performance thermoelectric materials and methods of preparation

    NASA Technical Reports Server (NTRS)

    Fleurial, Jean-Pierre (Inventor); Caillat, Thierry F. (Inventor); Borshchevsky, Alexander (Inventor)

    1997-01-01

    Transition metals (T) of Group VIII (Co, Rh and Ir) have been prepared as semiconductor alloys with Sb having the general formula TSb.sub.3. The skutterudite-type crystal lattice structure of these semiconductor alloys and their enhanced thermoelectric properties results in semiconductor materials which may be used in the fabrication of thermoelectric elements to substantially improve the efficiency of the resulting thermoelectric device. Semiconductor alloys having the desired skutterudite-type crystal lattice structure may be prepared in accordance with the present invention by using vertical gradient freeze techniques, liquid-solid phase sintering techniques, low temperature powder sintering and/or hot-pressing. Measurements of electrical and thermal transport properties of selected semiconductor materials prepared in accordance with the present invention, demonstrated high Hall mobilities (up to 8000 cm.sup.2.V.sup.-1.s.sup.-1), good Seebeck coefficients (up to 400 .mu.VK.sup.-1 between 300.degree. C. and 700.degree. C.), and low thermal conductivities (as low as 15 mW/cmK). Optimizing the transport properties of semiconductor materials prepared from elemental mixtures Co, Rh, Ir and Sb resulted in a two fold increase in the thermoelectric figure of merit (ZT) at temperatures as high as 400.degree. C. for thermoelectric elements fabricated from such semiconductor materials.

  10. Ga-Doping-Induced Carrier Tuning and Multiphase Engineering in n-type PbTe with Enhanced Thermoelectric Performance.

    PubMed

    Wang, Zhengshang; Wang, Guoyu; Wang, Ruifeng; Zhou, Xiaoyuan; Chen, Zhiyu; Yin, Cong; Tang, Mingjing; Hu, Qing; Tang, Jun; Ang, Ran

    2018-06-22

    P-type lead telluride (PbTe) emerged as a promising thermoelectric material for intermediate-temperature waste-heat-energy harvesting. However, n-type PbTe still confronted with a considerable challenge owing to its relatively low figure of merit ZT and conversion efficiency η, limiting widespread thermoelectric applications. Here, we report that Ga-doping in n-type PbTe can optimize carrier concentration and thus improve the power factor. Moreover, further experimental and theoretical evidence reveals that Ga-doping-induced multiphase structures with nano- to micrometer size can simultaneously modulate phonon transport, leading to dramatic reduction of lattice thermal conductivity. As a consequence, a tremendous enhancement of ZT value at 823 K reaches ∼1.3 for n-type Pb 0.97 Ga 0.03 Te. In particular, in a wide temperature range from 323 to 823 K, the average ZT ave value of ∼0.9 and the calculated conversion efficiency η of ∼13% are achieved by Ga doping. The present findings demonstrate the great potential in Ga-doped PbTe thermoelectric materials through a synergetic carrier tuning and multiphase engineering strategy.

  11. Advanced thermoelectric materials with enhanced crystal lattice structure and methods of preparation

    NASA Technical Reports Server (NTRS)

    Fleurial, Jean-Pierre (Inventor); Caillat, Thierry F. (Inventor); Borshchevsky, Alexander (Inventor)

    1998-01-01

    New skutterudite phases including Ru.sub.0.5 Pd.sub.0.5 Sb.sub.3, RuSb.sub.2 Te, and FeSb.sub.2 Te, have been prepared having desirable thermoelectric properties. In addition, a novel thermoelectric device has been prepared using skutterudite phase Fe.sub.0.5 Ni.sub.0.5 Sb.sub.3. The skutterudite-type crystal lattice structure of these semiconductor compounds and their enhanced thermoelectric properties results in semiconductor materials which may be used in the fabrication of thermoelectric elements to substantially improve the efficiency of the resulting thermoelectric device. Semiconductor materials having the desired skutterudite-type crystal lattice structure may be prepared in accordance with the present invention by using powder metallurgy techniques. Measurements of electrical and thermal transport properties of selected semiconductor materials prepared in accordance with the present invention, demonstrated high Hall mobilities and good Seebeck coefficients. These materials have low thermal conductivity and relatively low electrical resistivity, and are good candidates for low temperature thermoelectric applications.

  12. ZnTe Alloying Effect on Enhanced Thermoelectric Properties of p-Type PbTe.

    PubMed

    Ahn, Kyunghan; Shin, Hocheol; Im, Jino; Park, Sang Hyun; Chung, In

    2017-02-01

    We investigate the effect of ZnTe incorporation on PbTe to enhance thermoelectric performance. We report structural, microscopic, and spectroscopic characterizations, ab initio theoretical calculations, and thermoelectric transport properties of Pb 0.985 Na 0.015 Te-x% ZnTe (x = 0, 1, 2, 4). We find that the solid solubility limit of ZnTe in PbTe is less than 1 mol %. The introduction of 2% ZnTe in p-type Pb 0.985 Na 0.015 Te reduces the lattice thermal conductivity through the ZnTe precipitates at the microscale. Consequently, a maximum thermoelectric figure of merit (ZT) of 1.73 at 700 K is achieved for the spark plasma-sintered Pb 0.985 Na 0.015 Te-2% ZnTe, which arises from a decreased lattice thermal conductivity of ∼0.69 W m -1 K -1 at ∼700 K in comparison with Pb 0.985 Na 0.015 Te.

  13. Tailored semiconducting carbon nanotube networks with enhanced thermoelectric properties

    DOE PAGES

    Avery, Azure D.; Zhou, Ben H.; Lee, Jounghee; ...

    2016-04-04

    Thermoelectric power generation, allowing recovery of part of the energy wasted as heat, is emerging as an important component of renewable energy and energy efficiency portfolios. Although inorganic semiconductors have traditionally been employed in thermoelectric applications, organic semiconductors garner increasing attention as versatile thermoelectric materials. Here we present a combined theoretical and experimental study suggesting that semiconducting single-walled carbon nanotubes with carefully controlled chirality distribution and carrier density are capable of large thermoelectric power factors, higher than 340 μW m -1 K -2, comparable to the best-performing conducting polymers and larger than previously observed for carbon nanotube films. Furthermore, wemore » demonstrate that phonons are the dominant source of thermal conductivity in the networks, and that our carrier doping process significantly reduces the thermal conductivity relative to undoped networks. As a result, these findings provide the scientific underpinning for improved functional organic thermoelectric composites with carbon nanotube inclusions.« less

  14. Tailored semiconducting carbon nanotube networks with enhanced thermoelectric properties

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Avery, Azure D.; Zhou, Ben H.; Lee, Jounghee

    Thermoelectric power generation, allowing recovery of part of the energy wasted as heat, is emerging as an important component of renewable energy and energy efficiency portfolios. Although inorganic semiconductors have traditionally been employed in thermoelectric applications, organic semiconductors garner increasing attention as versatile thermoelectric materials. Here we present a combined theoretical and experimental study suggesting that semiconducting single-walled carbon nanotubes with carefully controlled chirality distribution and carrier density are capable of large thermoelectric power factors, higher than 340 μW m -1 K -2, comparable to the best-performing conducting polymers and larger than previously observed for carbon nanotube films. Furthermore, wemore » demonstrate that phonons are the dominant source of thermal conductivity in the networks, and that our carrier doping process significantly reduces the thermal conductivity relative to undoped networks. As a result, these findings provide the scientific underpinning for improved functional organic thermoelectric composites with carbon nanotube inclusions.« less

  15. Improved Thermoelectric Performance Achieved by Regulating Heterogeneous Phase in Half-Heusler TiNiSn-Based Materials

    NASA Astrophysics Data System (ADS)

    Chen, Jun-Liang; Liu, Chengyan; Miao, Lei; Gao, Jie; Zheng, Yan-yan; Wang, Xiaoyang; Lu, Jiacai; Shu, Mingzheng

    2018-06-01

    With excellent high-temperature stability (up to 1000 K) and favorable electrical properties for thermoelectric application, TiNiSn-based half-Heusler (HH) alloys are expected to be promising thermoelectric materials for the recovery of waste heat in the temperature ranging from 700 K to 900 K. However, their thermal conductivity is always relatively high (5-10 W/mK), making it difficult to further enhance their thermoelectric figure-of-merit ( ZT). In the past decade, introducing nano-scale secondary phases into the HH alloy matrix has been proven to be feasible for optimizing the thermoelectric performance of TiNiSn. In this study, a series of TiNiSn-based alloys have been successfully synthesized by a simple solid-state reaction. The content and composition of the heterogeneous phase (TiNi2Sn and Sn) is accurately regulated and, as a result, the thermal conductivity successfully reduced from 4.9 W m-1 K-1 to 3.0 Wm-1 K-1 (750 K) due to multi-scale phonon scattering. Consequently, a ZT value of 0.49 is achieved at 750 K in our TiNiSn-based thermoelectric materials. Furthermore, the thermal stability of TiNiSn alloys is enhanced through reducing the Sn substance phase.

  16. Improved Thermoelectric Performance Achieved by Regulating Heterogeneous Phase in Half-Heusler TiNiSn-Based Materials

    NASA Astrophysics Data System (ADS)

    Chen, Jun-Liang; Liu, Chengyan; Miao, Lei; Gao, Jie; Zheng, Yan-yan; Wang, Xiaoyang; Lu, Jiacai; Shu, Mingzheng

    2017-12-01

    With excellent high-temperature stability (up to 1000 K) and favorable electrical properties for thermoelectric application, TiNiSn-based half-Heusler (HH) alloys are expected to be promising thermoelectric materials for the recovery of waste heat in the temperature ranging from 700 K to 900 K. However, their thermal conductivity is always relatively high (5-10 W/mK), making it difficult to further enhance their thermoelectric figure-of-merit (ZT). In the past decade, introducing nano-scale secondary phases into the HH alloy matrix has been proven to be feasible for optimizing the thermoelectric performance of TiNiSn. In this study, a series of TiNiSn-based alloys have been successfully synthesized by a simple solid-state reaction. The content and composition of the heterogeneous phase (TiNi2Sn and Sn) is accurately regulated and, as a result, the thermal conductivity successfully reduced from 4.9 W m-1 K-1 to 3.0 Wm-1 K-1 (750 K) due to multi-scale phonon scattering. Consequently, a ZT value of 0.49 is achieved at 750 K in our TiNiSn-based thermoelectric materials. Furthermore, the thermal stability of TiNiSn alloys is enhanced through reducing the Sn substance phase.

  17. Enhanced thermoelectric performance driven by high-temperature phase transition in the phase change material Ge 4SbTe 5

    DOE PAGES

    Williams, Jared B.; Lara-Curzio, Edgar; Cakmak, Ercan; ...

    2015-05-15

    Phase change materials are identified for their ability to rapidly alternate between amorphous and crystalline phases and have large contrast in the optical/electrical properties of the respective phases. The materials are primarily used in memory storage applications, but recently they have also been identified as potential thermoelectric materials. Many of the phase change materials researched today can be found on the pseudo-binary (GeTe) 1-x(Sb 2Te 3) x tie-line. While many compounds on this tie-line have been recognized as thermoelectric materials, here we focus on Ge 4SbTe 5, a single phase compound just off of the (GeTe) 1-x(Sb 2Te 3) xmore » tie-line, that forms in a stable rocksalt crystal structure at room temperature. We find that stoichiometric and undoped Ge 4SbTe 5 exhibits a thermal conductivity of ~1.2 W/m-K at high temperature and a large Seebeck coefficient of ~250 μV/K. The resistivity decreases dramatically at 623 K due to a structural phase transition which lends to a large enhancement in both thermoelectric power factor and thermoelectric figure of merit at 823 K. In a more general sense the research presents evidence that phase change materials can potentially provide a new route to highly efficient thermoelectric materials for power generation at high temperature.« less

  18. New directions for nanoscale thermoelectric materials research

    NASA Technical Reports Server (NTRS)

    Dresselhaus, M. S.; Chen, G.; Tang, M. Y.; Yang, R. G.; Lee, H.; Wang, D. Z.; Ren, F.; Fleurial, J. P.; Gogna, P.

    2005-01-01

    Many of the recent advances in enhancing the thermoelectric figure of merit are linked to nanoscale phenomena with both bulk samples containing nanoscale constituents and nanoscale materials exhibiting enhanced thermoelectric performance in their own right. Prior theoretical and experimental proof of principle studies on isolated quantum well and quantum wire samples have now evolved into studies on bulk samples containing nanostructured constituents. In this review, nanostructural composites are shown to exhibit nanostructures and properties that show promise for thermoelectric applications. A review of some of the results obtained to date are presented.

  19. Terbium Ion Doping in Ca3Co4O9: A Step towards High-Performance Thermoelectric Materials

    PubMed Central

    Saini, Shrikant; Yaddanapudi, Haritha Sree; Tian, Kun; Yin, Yinong; Magginetti, David; Tiwari, Ashutosh

    2017-01-01

    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. In polycrystalline form, Ca3Co4O9 is known to exhibit much weaker thermoelectric response than in single crystal form. Here, we report the observation of enhanced thermoelectric response in polycrystalline Ca3Co4O9 on doping Tb ions in the material. Polycrystalline Ca3−xTbxCo4O9 (x = 0.0–0.7) samples were prepared by a solid-state reaction technique. Samples were thoroughly characterized using several state of the art techniques including XRD, TEM, SEM and XPS. Temperature dependent Seebeck coefficient, electrical resistivity and thermal conductivity measurements were performed. A record ZT of 0.74 at 800 K was observed for Tb doped Ca3Co4O9 which is the highest value observed till date in any polycrystalline sample of this system. PMID:28317853

  20. NREL Research Yields Significant Thermoelectric Performance | News | NREL

    Science.gov Websites

    Science paper, Large n- and p-type thermoelectric power factors from doped semiconducting single-walled negative charge carriers. These two types of material--called the p-type and the n-type legs, respectively heavily studied organic thermoelectric material, typically produce n-type materials that perform much

  1. Combination of Carrier Concentration Regulation and High Band Degeneracy for Enhanced Thermoelectric Performance of Cu3SbSe4.

    PubMed

    Zhang, Dan; Yang, Junyou; Jiang, Qinghui; Zhou, Zhiwei; Li, Xin; Xin, Jiwu; Basit, Abdul; Ren, Yangyang; He, Xu; Chu, Weijing; Hou, Jingdi

    2017-08-30

    The effect of Al-, Ga-, and In-doping on the thermoelectric (TE) properties of Cu 3 SbSe 4 has been comparatively studied on the basis of theoretical prediction and experimental validation. It is found that tiny Al/Ga/In substitution leads to a great enhancement of electrical conductivity with high carrier concentration and also large Seebeck coefficient due to the preserved high band degeneracy and thereby a remarkably high power factor. Ultimately, coupled with the depressed lattice thermal conductivity, all three elements (Al/Ga/In) substituted samples have obtained a highly improved thermoelectric performance with respect to undoped Cu 3 SbSe 4 . Compared to the samples at the same Al/In doping level, the slightly Ga-doped sample presents better TE performance over the wide temperature range, and the Cu 3 Sb 0.995 Ga 0.005 Se 4 sample presents a record high ZT value of 0.9 among single-doped Cu 3 SbSe 4 at 623 K, which is about 80% higher than that of pristine Cu 3 SbSe 4 . This work offers an alternative approach to boost the TE properties of Cu 3 SbSe 4 by selecting efficient dopant to weaken the coupling between electrical conductivity and Seebeck coefficient.

  2. Roles of Cu in the Enhanced Thermoelectric Properties in Bi0.5Sb1.5Te3

    PubMed Central

    Hao, Feng; Qiu, Pengfei; Song, Qingfeng; Chen, Hongyi; Lu, Ping; Ren, Dudi; Shi, Xun; Chen, Lidong

    2017-01-01

    Recently, Cu-containing p-type Bi0.5Sb1.5Te3 materials have shown high thermoelectric performances and promising prospects for practical application in low-grade waste heat recovery. However, the position of Cu in Bi0.5Sb1.5Te3 is controversial, and the roles of Cu in the enhancement of thermoelectric performance are still not clear. In this study, via defects analysis and stability test, the possibility of Cu intercalation in p-type Bi0.5Sb1.5Te3 materials has been excluded, and the position of Cu is identified as doping at the Sb sites. Additionally, the effects of Cu dopants on the electrical and thermal transport properties have been systematically investigated. Besides introducing additional holes, Cu dopants can also significantly enhance the carrier mobility by decreasing the Debye screen length and weakening the interaction between carriers and phonons. Meanwhile, the Cu dopants interrupt the periodicity of lattice vibration and bring stronger anharmonicity, leading to extremely low lattice thermal conductivity. Combining the suppression on the intrinsic excitation, a high thermoelectric performance—with a maximum thermoelectric figure of merit of around 1.4 at 430 K—has been achieved in Cu0.005Bi0.5Sb1.495Te3, which is 70% higher than the Bi0.5Sb1.5Te3 matrix. PMID:28772610

  3. Enhanced thermoelectric properties in bulk nanowire heterostructure-based nanocomposites through minority carrier blocking.

    PubMed

    Yang, Haoran; Bahk, Je-Hyeong; Day, Tristan; Mohammed, Amr M S; Snyder, G Jeffrey; Shakouri, Ali; Wu, Yue

    2015-02-11

    To design superior thermoelectric materials the minority carrier blocking effect in which the unwanted bipolar transport is prevented by the interfacial energy barriers in the heterogeneous nanostructures has been theoretically proposed recently. The theory predicts an enhanced power factor and a reduced bipolar thermal conductivity for materials with a relatively low doping level, which could lead to an improvement in the thermoelectric figure of merit (ZT). Here we show the first experimental demonstration of the minority carrier blocking in lead telluride-silver telluride (PbTe-Ag2Te) nanowire heterostructure-based nanocomposites. The nanocomposites are made by sintering PbTe-Ag2Te nanowire heterostructures produced in a highly scalable solution-phase synthesis. Compared with Ag2Te nanowire-based nanocomposite produced in similar method, the PbTe-Ag2Te nanocomposite containing ∼5 atomic % PbTe exhibits enhanced Seebeck coefficient, reduced thermal conductivity, and ∼40% improved ZT, which can be well explained by the theoretical modeling based on the Boltzmann transport equations when energy barriers for both electrons and holes at the heterostructure interfaces are considered in the calculations. For this p-type PbTe-Ag2Te nanocomposite, the barriers for electrons, that is, minority carriers, are primarily responsible for the ZT enhancement. By extending this approach to other nanostructured systems, it represents a key step toward low-cost solution-processable nanomaterials without heavy doping level for high-performance thermoelectric energy harvesting.

  4. Enhancement of the thermoelectric figure of merit in DNA-like systems induced by Fano and Dicke effects.

    PubMed

    Fu, Hua-Hua; Gu, Lei; Wu, Dan-Dan; Zhang, Zu-Quan

    2015-04-28

    We report a theoretical study highlighting the thermoelectric properties of biological and synthetic DNA molecules. Based on an effective tight-binding model of duplex DNA and by using the nonequilibrium Green's function technique, the thermal conductance, electrical conductance, Seebeck coefficient and thermoelectric figure of merit in the system are numerically calculated by varying the asymmetries of energies and electronic hoppings in the backbone sites to simulate the environmental complications and fluctuations. We find that due to the multiple transport paths in the DNA molecule, the Fano antiresonance occurs, and enhances the Seebeck coefficient and the figure of merit. When the energy difference is produced in every opposite backbone site, the Dicke effect appears. This effect gives rise to a semiconducting-metallic transition, and enhances the thermoelectric efficiency of the DNA molecule remarkably. Moreover, as the Fano antiresonance point is close to the Dicke resonance one, a giant enhancement in the thermoelectric figure of merit in the DNA molecule has been found. These results provide a scenario to obtain effective routes to enhance the thermoelectric efficiency in the DNA molecules, and suggest perspectives for future experiments intending to control the thermoelectric transport in DNA-like nanodevices.

  5. Significant enhancement in thermoelectric properties of polycrystalline Pr-doped SrTiO3-δ ceramics originating from nonuniform distribution of Pr dopants

    NASA Astrophysics Data System (ADS)

    Dehkordi, Arash Mehdizadeh; Bhattacharya, Sriparna; He, Jian; Alshareef, Husam N.; Tritt, Terry M.

    2014-05-01

    Recently, we have reported a significant enhancement (>70% at 500 °C) in the thermoelectric power factor (PF) of bulk polycrystalline Pr-doped SrTiO3 ceramics employing a novel synthesis strategy which led to the highest ever reported values of PF among doped polycrystalline SrTiO3. It was found that the formation of Pr-rich grain boundary regions gives rise to an enhancement in carrier mobility. In this Letter, we investigate the electronic and thermal transport in Sr1-xPrxTiO3 ceramics in order to determine the optimum doping concentration and to evaluate the overall thermoelectric performance. Simultaneous enhancement in the thermoelectric power factor and reduction in thermal conductivity in these samples resulted in more than 30% improvement in the dimensionless thermoelectric figure of merit (ZT) for the whole temperature range over all previously reported maximum values. Maximum ZT value of 0.35 was obtained at 500 °C.

  6. Development of Perovskite-Type Materials for Thermoelectric Application.

    PubMed

    Wu, Tingjun; Gao, Peng

    2018-06-12

    Oxide perovskite materials have a long history of being investigated for thermoelectric applications. Compared to the state-of-the-art tin and lead chalcogenides, these perovskite compounds have advantages of low toxicity, eco-friendliness, and high elemental abundance. However, because of low electrical conductivity and high thermal conductivity, the total thermoelectric performance of oxide perovskites is relatively poor. Variety of methods were used to enhance the TE properties of oxide perovskite materials, such as doping, inducing oxygen vacancy, embedding crystal imperfection, and so on. Recently, hybrid perovskite materials started to draw attention for thermoelectric application. Due to the low thermal conductivity and high Seebeck coefficient feature of hybrid perovskites materials, they can be promising thermoelectric materials and hold the potential for the application of wearable energy generators and cooling devices. This mini-review will build a bridge between oxide perovskites and burgeoning hybrid halide perovskites in the research of thermoelectric properties with an aim to further enhance the relevant performance of perovskite-type materials.

  7. Compressive strain induced enhancement in thermoelectric-power-factor in monolayer MoS2 nanosheet

    NASA Astrophysics Data System (ADS)

    Dimple; Jena, Nityasagar; De Sarkar, Abir

    2017-06-01

    Strain and temperature induced tunability in the thermoelectric properties in monolayer MoS2 (ML-MoS2) has been demonstrated using density functional theory coupled to semi-classical Boltzmann transport theory. Compressive strain, in general and uniaxial compressive strain (along the zig-zag direction), in particular, is found to be most effective in enhancing the thermoelectric power factor, owing to the higher electronic mobility and its sensitivity to lattice compression along this direction. Variation in the Seebeck coefficient and electronic band gap with strain is found to follow the Goldsmid-Sharp relation. n-type doping is found to raise the relaxation time-scaled thermoelectric power factor higher than p-type doping and this divide widens with increasing temperature. The relaxation time-scaled thermoelectric power factor in optimally n-doped ML-MoS2 is found to undergo maximal enhancement under the application of 3% uniaxial compressive strain along the zig-zag direction, when both the (direct) electronic band gap and the Seebeck coefficient reach their maximum, while the electron mobility drops down drastically from 73.08 to 44.15 cm2 V-1 s-1. Such strain sensitive thermoelectric responses in ML-MoS2 could open doorways for a variety of applications in emerging areas in 2D-thermoelectrics, such as on-chip thermoelectric power generation and waste thermal energy harvesting.

  8. Thermoelectric Performance of Na-Doped GeSe

    PubMed Central

    2017-01-01

    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. However, the electrical resistivity is large for all samples, leading to low power factors. Powder X-ray diffraction and scanning electron microscopy/energy-dispersive spectrometry results show the presence of a ternary impurity phase within the GeSe matrix for all doped samples, which suggests that the optimal carrier concentration cannot be reached by doping with Na. Nevertheless, the lattice thermal conductivity and carrier mobility of GeSe is similar to those of polycrystalline samples of the leading thermoelectric material SnSe, leading to quality factors of comparable magnitude. This implies that GeSe shows promise as a thermoelectric material if a more suitable dopant can be found. PMID:29302637

  9. In situ chemical oxidative polymerization preparation of poly(3,4-ethylenedioxythiophene)/graphene nanocomposites with enhanced thermoelectric performance.

    PubMed

    Xu, Kongli; Chen, Guangming; Qiu, Dong

    2015-05-01

    Three different in situ chemical oxidative polymerization routes, that is, (A) spin-coating and subsequent liquid layer polymerization, (B) spin-coating followed by vapor phase polymerization, and (C) in situ polymerization and then post-treatment by immersion in ethylene glycol (EG), have been developed to achieve poly(3,4-ethylenedioxythiophene)/reduced graphene oxide (PEDOT/rGO) nanocomposites. As demonstrated by scanning electron microscopic and energy-dispersive X-ray spectroscopic techniques, PEDOT has been successfully coated on the surface of the rGO nanosheets by each of the three preparation routes. Importantly, all of the nanocomposites display a greatly enhanced thermoelectric performance (power factors) relative to those of the corresponding neat PEDOT. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Flexible n-type thermoelectric composite films with enhanced performance through interface engineering and post-treatment.

    PubMed

    An, Hyeunhwan; Karas, Dale; Kim, Byung-Wook; Trabia, Sarah; Moon, Jaeyun

    2018-07-06

    Flexible thermoelectric (TE) materials, which are devices that convert thermal gradients to electrical energy, have attracted interest for practical energy-harvesting/recovery applications. However, as compared with p-type materials, the progress on the development of n-type TE flexible materials has been slow due to difficulties involved in n-type doping techniques. This study used high mobility carbon nanotubes (CNTs) to a uniformly mixed hybrid-composite, resulting in an enhanced power factor by increasing electrical conductivity. The energy filtering effect and stoichiometric composition of the material used, bismuth telluride (Bi 2 Te 3 ) correlated to a significant enhancement in TE performance, with a power factor of 225.9 μW m -1 K -2 at room temperature: a factor of 65 higher than as-fabricated composite film. This paper describes a simplified synthesis for the preparation of the composite film that eliminates time-intensive and cost-prohibitive processing, traditionally seen during extrusion and dicing inorganic manufacturing. The resulting post-annealed composite film consisting of Bi 2 Te 3 nanowire and CNTs demonstrate a promising candidate for material that can be used for an n-type TE device that has improved energy conversion efficiency.

  11. Flexible n-type thermoelectric composite films with enhanced performance through interface engineering and post-treatment

    NASA Astrophysics Data System (ADS)

    An, Hyeunhwan; Karas, Dale; Kim, Byung-Wook; Trabia, Sarah; Moon, Jaeyun

    2018-07-01

    Flexible thermoelectric (TE) materials, which are devices that convert thermal gradients to electrical energy, have attracted interest for practical energy-harvesting/recovery applications. However, as compared with p-type materials, the progress on the development of n-type TE flexible materials has been slow due to difficulties involved in n-type doping techniques. This study used high mobility carbon nanotubes (CNTs) to a uniformly mixed hybrid-composite, resulting in an enhanced power factor by increasing electrical conductivity. The energy filtering effect and stoichiometric composition of the material used, bismuth telluride (Bi2Te3) correlated to a significant enhancement in TE performance, with a power factor of 225.9 μW m‑1K‑2 at room temperature: a factor of 65 higher than as-fabricated composite film. This paper describes a simplified synthesis for the preparation of the composite film that eliminates time-intensive and cost-prohibitive processing, traditionally seen during extrusion and dicing inorganic manufacturing. The resulting post-annealed composite film consisting of Bi2Te3 nanowire and CNTs demonstrate a promising candidate for material that can be used for an n-type TE device that has improved energy conversion efficiency.

  12. Thermal transport and thermoelectric properties of beta-graphyne nanostructures.

    PubMed

    Ouyang, Tao; Hu, Ming

    2014-06-20

    Graphyne, an allotrope of graphene, is currently a hot topic in the carbon-based nanomaterials research community. Taking beta-graphyne as an example, we performed a comprehensive study of thermal transport and related thermoelectric properties by means of nonequilibrium Green's function (NEGF). Our simulation demonstrated that thermal conductance of beta-graphyne is only approximately 26% of that of the graphene counterpart and also shows evident anisotropy. Meanwhile, thermal conductance of armchair beta-graphyne nanoribbons (A-BGYNRs) presents abnormal stepwise width dependence. As for the thermoelectric property, we found that zigzag beta-graphyne nanoribbons (Z-BGYNRs) possess superior thermoelectric performance with figure of merit value achieving 0.5 at room temperature, as compared with graphene nanoribbons (~0.05). Aiming at obtaining a better thermoelectric coefficient, we also investigated Z-BGYNRs with geometric modulations. The results show that the thermoelectric performance can be enhanced dramatically (figure of merit exceeding 1.5 at room temperature), and such enhancement strongly depends on the width of the nanoribbons and location and quantity of geometric modulation. Our findings shed light on transport properties of beta-graphyne as high efficiency thermoelectrics. We anticipate that our simulation results could offer useful guidance for the design and fabrication of future thermoelectric devices.

  13. High Thermoelectric Performance by Convergence of Bands in IV-VI Semiconductors, Heavily Doped PbTe, and Alloys/Nanocomposites

    NASA Technical Reports Server (NTRS)

    Snyder, G. Jeffrey (Inventor); Pei, Yanzhong (Inventor)

    2015-01-01

    The present invention teaches an effective mechanism for enhancing thermoelectric performance through additional conductive bands. Using heavily doped p-PbTe materials as an example, a quantitative explanation is disclosed, as to why and how these additional bands affect the figure of merit. A high zT of approaching 2 at high temperatures makes these simple, likely more stable (than nanostructured materials) and Tl-free materials excellent for thermoelectric applications.

  14. Characteristic Evaluation on Cooling Performance of Thermoelectric Modules.

    PubMed

    Seo, Sae Rom; Han, Seungwoo

    2015-10-01

    The aim of this work is to develop a performance evaluation system for thermoelectric cooling modules. We describe the design of such a system, composed of a vacuum chamber with a heat sink along with a metal block to measure the absorbed heat Qc. The system has a simpler structure than existing water-cooled or air-cooled systems. The temperature difference between the cold and hot sides of the thermoelectric module ΔT can be accurately measured without any effects due to convection, and the temperature equilibrium time is minimized compared to a water-cooled system. The evaluation system described here can be used to measure characteristic curves of Qc as a function of ΔT, as well as the current-voltage relations. High-performance thermoelectric systems can therefore be developed using optimal modules evaluated with this system.

  15. Soft Chemistry, Coloring and Polytypism in Filled Tetrahedral Semiconductors: Toward Enhanced Thermoelectric and Battery Materials.

    PubMed

    White, Miles A; Medina-Gonzalez, Alan M; Vela, Javier

    2018-03-12

    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. Additionally, samples synthesized in solution phase have enhanced thermoelectric performance due to their decreased grain size. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  16. Combined electronic and thermodynamic approaches for enhancing the thermoelectric properties of Ti-doped PbTe.

    PubMed

    Komisarchik, G; Gelbstein, Y; Fuks, D

    2016-11-30

    Lead telluride based compounds are of great interest due to their enhanced thermoelectric transport properties. Nevertheless, the donor type impurities in this class of materials are currently mainly limited and alternative types of donor impurities are still required for optimizing the thermoelectric performance. In the current research titanium as a donor impurity in PbTe is examined. Although titanium is known to form resonant levels above the conduction band in PbTe, it does not enhance the thermo-power beyond the classical predictions. Recent experiments showed that alloying with a small amount of Ti (∼0.1 at%) gives a significant increase in the figure of merit. In the current research ab initio calculations were applied in order to correlate the reported experimental results with a thermoelectric optimization model. It was found that a Ti concentration of ∼1.4 at% in the Pb sublattice is expected to maximize the thermoelectric power factor. Using a statistical thermodynamic approach and in agreement with the previously reported appearance of a secondary intermetallic phase, the actual Ti solubility limit in PbTe is found to be ∼0.3 at%. Based on the proposed model, the mechanism for the formation of the previously observed secondary phase is attributed to phase separation reactions, characterized by a positive enthalpy of formation in the system. With extrapolation of the obtained ab initio results, it is demonstrated that lower Ti-doping concentrations than previously experimentally reported ones are expected to provide power factor values close to the maximal one, making doping with Ti a promising opportunity for the generation of highly efficient n-type PbTe-based thermoelectric materials.

  17. Nanocrystalline silicon: Lattice dynamics and enhanced thermoelectric properties

    DOE PAGES

    Claudio, Tania; Stein, Niklas; Stroppa, Daniel G.; ...

    2014-12-21

    In this study, silicon has several advantages when compared to other thermoelectric materials, but until recently it was not used for thermoelectric applications due to its high thermal conductivity, 156 W K -1 m -1 at room temperature. Nanostructuration as means to decrease thermal transport through enhanced phonon scattering has been a subject of many studies. In this work we have evaluated the effects of nanostructuration on the lattice dynamics of bulk nanocrystalline doped silicon. The samples were prepared by gas phase synthesis, followed by current and pressure assisted sintering. The heat capacity, density of phonons states, and elastic constantsmore » were measured, which all reveal a significant, ≈25%, reduction in the speed of sound. The samples present a significantly decreased lattice thermal conductivity, ≈25 W K -1 m -1, which, combined with a very high carrier mobility, results in a dimensionless figure of merit with a competitive value that peaks at ZT ≈ 0.57 at 973 °C. Due to its easily scalable and extremely low-cost production process, nanocrystalline Si prepared by gas phase synthesis followed by sintering could become the material of choice for high temperature thermoelectric generators.« less

  18. Unravelling the progressive role of rattlers in thermoelectric clathrate and strategies for performance improvement: Concurrently enhancing electronic transport and blocking phononic transport

    NASA Astrophysics Data System (ADS)

    Yang, Jia-Yue; Cheng, Long; Hu, Ming

    2017-12-01

    Intermetallic clathrates, one class of guest-host systems with perfectly crystalline structures, hold great potential to be the "phonon glass - electron crystal" thermoelectric materials. Previous studies focus on revealing the atomistic origins of blocked phononic transport, yet little attention is drawn to the enhanced electronic transport. In this work, we investigate the binary type-I M8Si46 (M = Sr, Ba, Tl, and Pb) clathrates and unravel how rattlers concurrently block phononic transport and enhance electronic transport from first-principles. By comparing the empty and filled clathrates, the lattice thermal conductivity is greatly reduced by a factor of 21 due to the decrease in phonon relaxation time for propagative phonons over 0-6 THz by 1.5 orders of magnitude. On the other hand, rattlers bridge charge gaps among cages by donating electrons and thus drastically increase electrical conductivity. The concurrent realization of blocked phononic transport and enhanced electronic transport boosts the figure-of-merit (ZT) of empty clathrate by 4 orders of magnitude. Furthermore, by manipulating metallic rattlers and n-type doping, the power factor is markedly improved and ZT can reach 0.55 at 800 K. These results provide a quantitative description of the guest-host interaction and coupling dynamics from first-principles. The proposed strategy of manipulating ratting atoms and in-situ doping offers important guidance to engineer clathrates with high thermoelectric performance.

  19. PEDOT:PSS/graphene quantum dots films with enhanced thermoelectric properties via strong interfacial interaction and phase separation.

    PubMed

    Du, Fei-Peng; Cao, Nan-Nan; Zhang, Yun-Fei; Fu, Ping; Wu, Yan-Guang; Lin, Zhi-Dong; Shi, Run; Amini, Abbas; Cheng, Chun

    2018-04-24

    The typical conductive polymer of PEDOT:PSS has recently attracted intensive attention in thermoelectric conversion because of its low cost and low thermal conductivity as well as high electrical conductivity. However, compared to inorganic counterparts, the relatively poor thermoelectric performance of PEDOT:PSS has greatly limited its development and high-tech applications. Here, we report a dramatic enhancement in the thermoelectric performance of PEDOT:PSS by constructing unique composite films with graphene quantum dots (GQDs). At room temperature, the electrical conductivity and Seebeck coefficient of PEDOT:PSS/GQDs reached to 7172 S/m and 14.6 μV/K, respectively, which are 30.99% and 113.2% higher than those of pristine PEDOT:PSS. As a result, the power factor of the optimized PEDOT:PSS/GQDs composite is 550% higher than that of pristine PEDOT:PSS. These significant improvements are attributed to the ordered alignment of PEDOT chains on the surface of GQDs, originated from the strong interfacial interaction between PEDOT:PSS and GQDs and the separation of PEDOT and PSS phases. This study evidently provides a promising route for PEDOT:PSS applied in high-efficiency thermoelectric conversion.

  20. Promising Thermoelectric Bulk Materials with 2D Structures.

    PubMed

    Zhou, Yiming; Zhao, Li-Dong

    2017-12-01

    Given that more than two thirds of all energy is lost, mostly as waste heat, in utilization processes worldwide, thermoelectric materials, which can directly convert waste heat to electricity, provide an alternative option for optimizing energy utilization processes. After the prediction that superlattices may show high thermoelectric performance, various methods based on quantum effects and superlattice theory have been adopted to analyze bulk materials, leading to the rapid development of thermoelectric materials. Bulk materials with two-dimensional (2D) structures show outstanding properties, and their high performance originates from both their low thermal conductivity and high Seebeck coefficient due to their strong anisotropic features. Here, the advantages of superlattices for enhancing the thermoelectric performance, the transport mechanism in bulk materials with 2D structures, and optimization methods are discussed. The phenomenological transport mechanism in these materials indicates that thermal conductivities are reduced in 2D materials with intrinsically short mean free paths. Recent progress in the transport mechanisms of Bi 2 Te 3 -, SnSe-, and BiCuSeO-based systems is summarized. Finally, possible research directions to enhance the thermoelectric performance of bulk materials with 2D structures are briefly considered. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Fabrication of Advanced Thermoelectric Materials by Hierarchical Nanovoid Generation

    NASA Technical Reports Server (NTRS)

    Park, Yeonjoon (Inventor); Elliott, James R. (Inventor); Stoakley, Diane M. (Inventor); Chu, Sang-Hyon (Inventor); King, Glen C. (Inventor); Kim, Jae-Woo (Inventor); Choi, Sang Hyouk (Inventor); Lillehei, Peter T. (Inventor)

    2011-01-01

    A novel method to prepare an advanced thermoelectric material has hierarchical structures embedded with nanometer-sized voids which are key to enhancement of the thermoelectric performance. Solution-based thin film deposition technique enables preparation of stable film of thermoelectric material and void generator (voigen). A subsequent thermal process creates hierarchical nanovoid structure inside the thermoelectric material. Potential application areas of this advanced thermoelectric material with nanovoid structure are commercial applications (electronics cooling), medical and scientific applications (biological analysis device, medical imaging systems), telecommunications, and defense and military applications (night vision equipments).

  2. Prediction of the High Thermoelectric Performance of Pnictogen Dichalcogenide Layered Compounds with Quasi-One-Dimensional Gapped Dirac-like Band Dispersion

    NASA Astrophysics Data System (ADS)

    Ochi, Masayuki; Usui, Hidetomo; Kuroki, Kazuhiko

    2017-12-01

    Thermoelectric power generation has been recognized as one of the most important technologies, and high-performance thermoelectric materials have long been pursued. However, because of the large number of candidate materials, this quest is extremely challenging, and it has become clear that a firm theoretical concept from the viewpoint of band-structure engineering is needed. We theoretically demonstrate that pnictogen dichalcogenide layered compounds, which originally attracted attention as a family of superconductors and have recently been investigated as thermoelectric materials, can exhibit very high thermoelectric performance with elemental substitution. Specifically, we clarify a promising guiding principle for material design and find that LaOAsSe2, a material that has yet to be synthesized, has a power factor that is 6 times as large as that of the known compound LaOBiS2 and can exhibit a very large Z T under some plausible assumptions. This large enhancement of the thermoelectric performance originates from the quasi-one-dimensional gapped Dirac-like band dispersion, which is realized by the square-lattice network. We offer one ideal limit of the band structure for thermoelectric materials. Because our target materials have high controllability of constituent elements and feasibility of carrier doping, experimental studies along this line are eagerly awaited.

  3. Intrinsically High Thermoelectric Performance in AgInSe2 n-Type Diamond-Like Compounds.

    PubMed

    Qiu, Pengfei; Qin, Yuting; Zhang, Qihao; Li, Ruoxi; Yang, Jiong; Song, Qingfeng; Tang, Yunshan; Bai, Shengqiang; Shi, Xun; Chen, Lidong

    2018-03-01

    Diamond-like compounds are a promising class of thermoelectric materials, very suitable for real applications. However, almost all high-performance diamond-like thermoelectric materials are p-type semiconductors. The lack of high-performance n-type diamond-like thermoelectric materials greatly restricts the fabrication of diamond-like material-based modules and their real applications. In this work, it is revealed that n-type AgInSe 2 diamond-like compound has intrinsically high thermoelectric performance with a figure of merit ( zT ) of 1.1 at 900 K, comparable to the best p-type diamond-like thermoelectric materials reported before. Such high zT is mainly due to the ultralow lattice thermal conductivity, which is fundamentally limited by the low-frequency Ag-Se "cluster vibrations," as confirmed by ab initio lattice dynamic calculations. Doping Cd at Ag sites significantly improves the thermoelectric performance in the low and medium temperature ranges. By using such high-performance n-type AgInSe 2 -based compounds, the diamond-like thermoelectric module has been fabricated for the first time. An output power of 0.06 W under a temperature difference of 520 K between the two ends of the module is obtained. This work opens a new window for the applications using the diamond-like thermoelectric materials.

  4. Enhanced thermoelectric performance of Pb doped Cu2SnSe3 synthesized employing spark plasma sintering

    NASA Astrophysics Data System (ADS)

    Shyam Prasad, K.; Rao, Ashok; Tyagi, Kriti; Singh Chauhan, Nagendra; Gahtori, Bhasker; Bathula, Sivaiah; Dhar, Ajay

    2017-05-01

    We report an enhancement in the thermoelectric performance of Cu2SnSe3 alloy on Pb doping, owing to a sharp increase in its power factor. The powder XRD pattern of all samples of Cu2Sn1-xPbxSe3 (0≤x≤0.03), prepared using solid state reaction, exhibited a cubic structure with a space group of F 4 ̅ 3 m . The results show that temperature dependent electrical resistivity, ρ(T) increases with increasing temperature thereby demonstrating that the samples display heavily doped semiconducting nature, which could be satisfactorily described by small polaron hopping model in the whole temperature range of measurement for all the samples. Both the resistivity and the Seebeck coefficient are reduced with 2 vol% Pb doping. The thermal conductivity of all the samples reduces with increasing temperature. Despite a decrease in Seebeck coefficient the power factor shows an increase on Pb doping, owing to a sharp surge in the electrical conductivity which results in an enhanced ZTmax 0.64 at 700 K for an optimized composition of Cu2Sn0.98Pb0.02Se3, which is nearly twice the value of the corresponding undoped counterpart.

  5. Pressure-induced enhancement in the thermoelectric properties of monolayer and bilayer SnSe2

    NASA Astrophysics Data System (ADS)

    Zou, Daifeng; Yu, Chuanbin; Li, Yuhao; Ou, Yun; Gao, Yongyi

    2018-03-01

    The electronic structures of monolayer and bilayer SnSe2 under pressure were investigated by using first-principles calculations including van der Waals interactions. For monolayer SnSe2, the variation of electronic structure under pressure is controlled by pressure-dependent lattice parameters. For bilayer SnSe2, the changes in electronic structure under pressure are dominated by intralayer and interlayer atomic interactions. The n-type thermoelectric properties of monolayer and bilayer SnSe2 under pressure were calculated on the basis of the semi-classical Boltzmann transport theory. It was found that the electrical conductivity of monolayer and bilayer SnSe2 can be enhanced under pressure, and such dependence can be attributed to the pressure-induced changes of the Se-Sn antibonding states in conduction band. Finally, the doping dependence of power factors of n-type monolayer and bilayer SnSe2 at three different pressures were estimated, and the results unveiled that thermoelectric performance of n-type monolayer and bilayer SnSe2 can be improved by applying external pressure. This study benefits to understand the nature of the transport properties for monolayer and bilayer SnSe2 under pressure, and it offers valuable insight for designing high-performance thermoelectric few-layered SnSe2 through strain engineering induced by external pressure.

  6. Discovery of high-performance low-cost n-type Mg3Sb2-based thermoelectric materials with multi-valley conduction bands

    PubMed Central

    Zhang, Jiawei; Song, Lirong; Pedersen, Steffen Hindborg; Yin, Hao; Hung, Le Thanh; Iversen, Bo Brummerstedt

    2017-01-01

    Widespread application of thermoelectric devices for waste heat recovery requires low-cost high-performance materials. The currently available n-type thermoelectric materials are limited either by their low efficiencies or by being based on expensive, scarce or toxic elements. Here we report a low-cost n-type material, Te-doped Mg3Sb1.5Bi0.5, that exhibits a very high figure of merit zT ranging from 0.56 to 1.65 at 300−725 K. Using combined theoretical prediction and experimental validation, we show that the high thermoelectric performance originates from the significantly enhanced power factor because of the multi-valley band behaviour dominated by a unique near-edge conduction band with a sixfold valley degeneracy. This makes Te-doped Mg3Sb1.5Bi0.5 a promising candidate for the low- and intermediate-temperature thermoelectric applications. PMID:28059069

  7. Enhanced electrical transport and thermoelectric properties in Ni doped Cu3SbSe4

    NASA Astrophysics Data System (ADS)

    Kumar, Aparabal; Dhama, P.; Das, Anish; Sarkar, Kalyan Jyoti; Banerji, P.

    2018-05-01

    In this study, we report the enhanced thermoelectric performance of Cu3SbSe4 by Ni doping at Cu site. Cu3-xNixSbSe4 (x = 0, 0.01, 0.03, 0.05) were prepared by melt growth, ball milling followed by spark plasma sintering. Structural characterization, phase analysis and surface morphology were carried out using X-ray diffraction, field emission scanning electron microscopy and energy dispersive X-ray spectroscopy. Electrical and thermal properties of all the samples were investigated in the temperature range 300 - 650 K. Decrease in electrical resistivity with Ni doping due to increase in carrier concentration with enhanced Seebeck coefficient via increase in density of state near the Fermi level gives a remarkably high power factor. At the same time, thermal conductivity was found to decrease due to increased carrier-phonon scattering and acoustic phonon scattering. Consequently, a remarkable enhancement in the thermoelectric figure of merit (ZT˜ 0.65) of Cu3-xNixSbSe4 was achieved for x = 0.01 sample. Thus, Ni doping is an effective approach to improve the efficiency of Cu3SbSe4.

  8. Ballistic thermoelectric properties of nitrogenated holey graphene nanostructures

    NASA Astrophysics Data System (ADS)

    Cao, Wei; Xiao, Huaping; Ouyang, Tao; Zhong, Jianxin

    2017-11-01

    In this study, we theoretically investigate the ballistic thermoelectric performance of a new two-dimensional material, nitrogenated holey graphene (NHG), using nonequilibrium Green's function method. The calculations show that compared to graphene, such novel single atomic layer structure exhibits better thermoelectric performance. At room temperature, the stable hole (electron) thermoelectric figure of merit ( Z T ) could approach 0.75 (0.2) and 0.6 (0.2) for zigzag-edged (Z-NHGNRs) and armchair-edged NHGNRs (A-NHGNRs), respectively. To achieve better thermoelectric performance, the effect of geometric engineering (chevron-type nanoribbons and rhomboid quantum dot) on the electronic and phononic transport properties of Z-NHGNRs is further discussed. The results indicate that structure modulation is indeed a viable approach to enhance the thermoelectric properties (the figure of merit could exceed 1.5 and 1.3 for the chevron-type and rhomboid quantum dot system, respectively). On analyzing the transport properties, such improvement on the figure of merit is mainly attributed to the increased Seebeck coefficient and reduced thermal conductance (including both electronic and phononic contributions). Our findings presented in this paper qualify NHG as a promising thermoelectric material and provide theoretical guidance for fabricating the outstanding thermoelectric devices.

  9. Intrinsically High Thermoelectric Performance in AgInSe2 n‐Type Diamond‐Like Compounds

    PubMed Central

    Qiu, Pengfei; Qin, Yuting; Zhang, Qihao; Li, Ruoxi; Song, Qingfeng; Tang, Yunshan; Bai, Shengqiang

    2017-01-01

    Abstract Diamond‐like compounds are a promising class of thermoelectric materials, very suitable for real applications. However, almost all high‐performance diamond‐like thermoelectric materials are p‐type semiconductors. The lack of high‐performance n‐type diamond‐like thermoelectric materials greatly restricts the fabrication of diamond‐like material‐based modules and their real applications. In this work, it is revealed that n‐type AgInSe2 diamond‐like compound has intrinsically high thermoelectric performance with a figure of merit (zT) of 1.1 at 900 K, comparable to the best p‐type diamond‐like thermoelectric materials reported before. Such high zT is mainly due to the ultralow lattice thermal conductivity, which is fundamentally limited by the low‐frequency Ag‐Se “cluster vibrations,” as confirmed by ab initio lattice dynamic calculations. Doping Cd at Ag sites significantly improves the thermoelectric performance in the low and medium temperature ranges. By using such high‐performance n‐type AgInSe2‐based compounds, the diamond‐like thermoelectric module has been fabricated for the first time. An output power of 0.06 W under a temperature difference of 520 K between the two ends of the module is obtained. This work opens a new window for the applications using the diamond‐like thermoelectric materials. PMID:29593972

  10. Thermoelectric efficiency of (1 - x)(GeTe) x(Bi2Se0.2Te2.8) and implementation into highly performing thermoelectric power generators.

    PubMed

    Koenig, J; Winkler, M; Dankwort, T; Hansen, A-L; Pernau, H-F; Duppel, V; Jaegle, M; Bartholomé, K; Kienle, L; Bensch, W

    2015-02-14

    Here we report for the first time on a complete simulation assisted "material to module" development of a high performance thermoelectric generator (TEG) based on the combination of a phase change material and established thermoelectrics yielding the compositions (1 - x)(GeTe) x(Bi(2)Se(0.2)Te(2.8)). For the generator design our approach for benchmarking thermoelectric materials is demonstrated which is not restricted to the determination of the intrinsically imprecise ZT value but includes the implementation of the material into a TEG. This approach is enabling a much more reliable benchmarking of thermoelectric materials for TEG application. Furthermore we analyzed the microstructure and performance close to in-operandi conditions for two different compositions in order to demonstrate the sensitivity of the material against processing and thermal cycling. For x = 0.038 the microstructure of the as-prepared material remains unchanged, consequently, excellent and stable thermoelectric performance as prerequisites for TEG production was obtained. For x = 0.063 we observed strain phenomena for the pristine state which are released by the formation of planar defects after thermal cycling. Consequently the thermoelectric performance degrades significantly. These findings highlight a complication for deriving the correlation of microstructure and properties of thermoelectric materials in general.

  11. BiCuSeO Thermoelectrics: An Update on Recent Progress and Perspective

    PubMed Central

    Zhang, Xiaoxuan; Chang, Cheng; Zhou, Yiming; Zhao, Li-Dong

    2017-01-01

    A BiCuSeO system has been reported as a promising thermoelectric material and has attracted great attention in the thermoelectric community since 2010. Recently, several remarkable studies have been reported and the ZT of BiCuSeO was pushed to a higher level. It motivates us to systematically summarize the recent reports on the BiCuSeO system. In this short review, we start with several attempts to optimize thermoelectric properties of BiCuSeO. Then, we introduce several opinions to explore the origins of low thermal conductivity for BiCuSeO. Several approaches to enhance thermoelectric performance are also summarized, including modulation doping, introducing dual-vacancies, and dual-doping, etc. At last, we propose some possible strategies for enhancing thermoelectric performance of BiCuSeO in future research. PMID:28772557

  12. High-performance and flexible thermoelectric films by screen printing solution-processed nanoplate crystals.

    PubMed

    Varghese, Tony; Hollar, Courtney; Richardson, Joseph; Kempf, Nicholas; Han, Chao; Gamarachchi, Pasindu; Estrada, David; Mehta, Rutvik J; Zhang, Yanliang

    2016-09-12

    Screen printing allows for direct conversion of thermoelectric nanocrystals into flexible energy harvesters and coolers. However, obtaining flexible thermoelectric materials with high figure of merit ZT through printing is an exacting challenge due to the difficulties to synthesize high-performance thermoelectric inks and the poor density and electrical conductivity of the printed films. Here, we demonstrate high-performance flexible films and devices by screen printing bismuth telluride based nanocrystal inks synthesized using a microwave-stimulated wet-chemical method. Thermoelectric films of several tens of microns thickness were screen printed onto a flexible polyimide substrate followed by cold compaction and sintering. The n-type films demonstrate a peak ZT of 0.43 along with superior flexibility, which is among the highest reported ZT values in flexible thermoelectric materials. A flexible thermoelectric device fabricated using the printed films produces a high power density of 4.1 mW/cm(2) with 60 °C temperature difference between the hot side and cold side. The highly scalable and low cost process to fabricate flexible thermoelectric materials and devices demonstrated here opens up many opportunities to transform thermoelectric energy harvesting and cooling applications.

  13. High-performance and flexible thermoelectric films by screen printing solution-processed nanoplate crystals

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Varghese, Tony; Hollar, Courtney; Richardson, Joseph

    Screen printing allows for direct conversion of thermoelectric nanocrystals into flexible energy harvesters and coolers. However, obtaining flexible thermoelectric materials with high figure of merit ZT through printing is an exacting challenge due to the difficulties to synthesize high-performance thermoelectric inks and the poor density and electrical conductivity of the printed films. Here, we demonstrate high-performance flexible films and devices by screen printing bismuth telluride based nanocrystal inks synthesized using a microwave-stimulated wet-chemical method. Thermoelectric films of several tens of microns thickness were screen printed onto a flexible polyimide substrate followed by cold compaction and sintering. The n-type films demonstratemore » a peak ZT of 0.43 along with superior flexibility, which is among the highest reported ZT values in flexible thermoelectric materials. A flexible thermoelectric device fabricated using the printed films produces a high power density of 4.1 mW/cm 2 with 60°C temperature difference between the hot side and cold side. In conclusion, the highly scalable and low cost process to fabricate flexible thermoelectric materials and devices demonstrated here opens up many opportunities to transform thermoelectric energy harvesting and cooling applications.« less

  14. High-performance and flexible thermoelectric films by screen printing solution-processed nanoplate crystals

    DOE PAGES

    Varghese, Tony; Hollar, Courtney; Richardson, Joseph; ...

    2016-09-12

    Screen printing allows for direct conversion of thermoelectric nanocrystals into flexible energy harvesters and coolers. However, obtaining flexible thermoelectric materials with high figure of merit ZT through printing is an exacting challenge due to the difficulties to synthesize high-performance thermoelectric inks and the poor density and electrical conductivity of the printed films. Here, we demonstrate high-performance flexible films and devices by screen printing bismuth telluride based nanocrystal inks synthesized using a microwave-stimulated wet-chemical method. Thermoelectric films of several tens of microns thickness were screen printed onto a flexible polyimide substrate followed by cold compaction and sintering. The n-type films demonstratemore » a peak ZT of 0.43 along with superior flexibility, which is among the highest reported ZT values in flexible thermoelectric materials. A flexible thermoelectric device fabricated using the printed films produces a high power density of 4.1 mW/cm 2 with 60°C temperature difference between the hot side and cold side. In conclusion, the highly scalable and low cost process to fabricate flexible thermoelectric materials and devices demonstrated here opens up many opportunities to transform thermoelectric energy harvesting and cooling applications.« less

  15. High-performance and flexible thermoelectric films by screen printing solution-processed nanoplate crystals

    PubMed Central

    Varghese, Tony; Hollar, Courtney; Richardson, Joseph; Kempf, Nicholas; Han, Chao; Gamarachchi, Pasindu; Estrada, David; Mehta, Rutvik J.; Zhang, Yanliang

    2016-01-01

    Screen printing allows for direct conversion of thermoelectric nanocrystals into flexible energy harvesters and coolers. However, obtaining flexible thermoelectric materials with high figure of merit ZT through printing is an exacting challenge due to the difficulties to synthesize high-performance thermoelectric inks and the poor density and electrical conductivity of the printed films. Here, we demonstrate high-performance flexible films and devices by screen printing bismuth telluride based nanocrystal inks synthesized using a microwave-stimulated wet-chemical method. Thermoelectric films of several tens of microns thickness were screen printed onto a flexible polyimide substrate followed by cold compaction and sintering. The n-type films demonstrate a peak ZT of 0.43 along with superior flexibility, which is among the highest reported ZT values in flexible thermoelectric materials. A flexible thermoelectric device fabricated using the printed films produces a high power density of 4.1 mW/cm2 with 60 °C temperature difference between the hot side and cold side. The highly scalable and low cost process to fabricate flexible thermoelectric materials and devices demonstrated here opens up many opportunities to transform thermoelectric energy harvesting and cooling applications. PMID:27615036

  16. Significant enhancement in thermoelectric properties of polycrystalline Pr-doped SrTiO{sub 3−δ} ceramics originating from nonuniform distribution of Pr dopants

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Dehkordi, Arash Mehdizadeh, E-mail: amehdiz@g.clemson.edu; Bhattacharya, Sriparna; He, Jian

    2014-05-12

    Recently, we have reported a significant enhancement (>70% at 500 °C) in the thermoelectric power factor (PF) of bulk polycrystalline Pr-doped SrTiO{sub 3} ceramics employing a novel synthesis strategy which led to the highest ever reported values of PF among doped polycrystalline SrTiO{sub 3}. It was found that the formation of Pr-rich grain boundary regions gives rise to an enhancement in carrier mobility. In this Letter, we investigate the electronic and thermal transport in Sr{sub 1−x}Pr{sub x}TiO{sub 3} ceramics in order to determine the optimum doping concentration and to evaluate the overall thermoelectric performance. Simultaneous enhancement in the thermoelectric power factormore » and reduction in thermal conductivity in these samples resulted in more than 30% improvement in the dimensionless thermoelectric figure of merit (ZT) for the whole temperature range over all previously reported maximum values. Maximum ZT value of 0.35 was obtained at 500 °C.« less

  17. High performance thermoelectric nanocomposite device

    DOEpatents

    Yang, Jihui [Lakeshore, CA; Snyder, Dexter D [Birmingham, MI

    2011-10-25

    A thermoelectric device includes a nanocomposite material with nanowires of at least one thermoelectric material having a predetermined figure of merit, the nanowires being formed in a porous substrate having a low thermal conductivity and having an average pore diameter ranging from about 4 nm to about 300 nm.

  18. Control system for thermoelectric refrigerator

    NASA Technical Reports Server (NTRS)

    Nelson, John L. (Inventor); Criscuolo, Lance (Inventor); Gilley, Michael D. (Inventor); Park, Brian V. (Inventor)

    1996-01-01

    Apparatus including a power supply (202) and control system is provided for maintaining the temperature within an enclosed structure (40) using thermoelectric devices (92). The apparatus may be particularly beneficial for use with a refrigerator (20) having superinsulation materials (46) and phase change materials (112) which cooperate with the thermoelectric device (92) to substantially enhance the overall operating efficiency of the refrigerator (20). The electrical power supply (202) and control system allows increasing the maximum power capability of the thermoelectric device (92) in response to increased heat loads within the refrigerator (20). The electrical power supply (202) and control system may also be used to monitor the performance of the cooling system (70) associated with the refrigerator (20).

  19. Development of a prototype thermoelectric space cooling system using phase change material to improve the performance

    NASA Astrophysics Data System (ADS)

    Zhao, Dongliang

    The thermoelectric cooling system has advantages over conventional vapor compression cooling devices, including compact in size, light in weight, high reliability, no mechanical moving parts, no refrigerant, being powered by direct current, and easily switching between cooling and heating modes. However, it has been long suffering from its relatively high cost and low energy efficiency, which has restricted its usage to niche applications, such as space missions, portable cooling devices, scientific and medical equipment, where coefficient of performance (COP) is not as important as reliability, energy availability, and quiet operation environment. Enhancement of thermoelectric cooling system performance generally relies on two methods: improving thermoelectric material efficiency and through thermoelectric cooling system thermal design. This research has been focused on the latter one. A prototype thermoelectric cooling system integrated with phase change material (PCM) thermal energy storage unit for space cooling has been developed. The PCM thermal storage unit used for cold storage at night, functions as the thermoelectric cooling system's heat sink during daytime's cooling period and provides relatively lower hot side temperature for the thermoelectric cooling system. The experimental test of the prototype system in a reduced-scale chamber has realized an average cooling COP of 0.87, with the maximum value of 1.22. Another comparison test for efficacy of PCM thermal storage unit shows that 35.3% electrical energy has been saved from using PCM for the thermoelectric cooling system. In general, PCM faces difficulty of poor thermal conductivity at both solid and liquid phases. This system implemented a finned inner tube to increase heat transfer during PCM charging (melting) process that directly impacts thermoelectric system's performance. A simulation tool for the entire system has been developed including mathematical models for a single thermoelectric module

  20. Pressure-induced enhancement in the thermoelectric properties of monolayer and bilayer SnSe2.

    PubMed

    Zou, Daifeng; Yu, Chuanbin; Li, Yuhao; Ou, Yun; Gao, Yongyi

    2018-03-01

    The electronic structures of monolayer and bilayer SnSe 2 under pressure were investigated by using first-principles calculations including van der Waals interactions. For monolayer SnSe 2 , the variation of electronic structure under pressure is controlled by pressure-dependent lattice parameters. For bilayer SnSe 2 , the changes in electronic structure under pressure are dominated by intralayer and interlayer atomic interactions. The n -type thermoelectric properties of monolayer and bilayer SnSe 2 under pressure were calculated on the basis of the semi-classical Boltzmann transport theory. It was found that the electrical conductivity of monolayer and bilayer SnSe 2 can be enhanced under pressure, and such dependence can be attributed to the pressure-induced changes of the Se-Sn antibonding states in conduction band. Finally, the doping dependence of power factors of n -type monolayer and bilayer SnSe 2 at three different pressures were estimated, and the results unveiled that thermoelectric performance of n -type monolayer and bilayer SnSe 2 can be improved by applying external pressure. This study benefits to understand the nature of the transport properties for monolayer and bilayer SnSe 2 under pressure, and it offers valuable insight for designing high-performance thermoelectric few-layered SnSe 2 through strain engineering induced by external pressure.

  1. Incorporation of MoS2 nanosheets in CoSb3 matrix as an efficient novel strategy to enhance its thermoelectric performance

    NASA Astrophysics Data System (ADS)

    Yadav, Suchitra; Chaudhary, Sujeet; Pandya, Dinesh K.

    2018-03-01

    The nanocomposite approach is considered as an effective way to improve the thermoelectric properties of bulk materials and we have exploited it by simultaneous though independent tackling of the electron and phonon transports. In the present study, through the strategy of anchoring the CoSb3 nanoparticles on the 2-dimensional nanosheets of MoS2, we demonstrate a controlled interplay of the newly created CoSb3/MoS2 interfaces in nanocomposites of varying concentration of MoS2 via significant enhancement of the phonon scattering without deterioration of electron transport. A concurrent occurrence of low energy carrier filtering on account of the interfacial potential barrier helps in beneficial manipulation of grain to grain carrier transport. The dimensionless figure of merit ZT maximizes to 0.53 at 600 K for the CoSb3/MoS2 nanocomposite containing 3 wt% of MoS2, 4-fold increase over the pristine CoSb3 in the 300-600 K range. This study paves the way towards improvement of the thermoelectric performance of p-type CoSb3 using 2D MoS2 as an interfacial additive.

  2. Rare earth-doped materials with enhanced thermoelectric figure of merit

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Venkatasubramanian, Rama; Cook, Bruce Allen; Levin, Evgenii M.

    A thermoelectric material and a thermoelectric converter using this material. The thermoelectric material has a first component including a semiconductor material and a second component including a rare earth material included in the first component to thereby increase a figure of merit of a composite of the semiconductor material and the rare earth material relative to a figure of merit of the semiconductor material. The thermoelectric converter has a p-type thermoelectric material and a n-type thermoelectric material. At least one of the p-type thermoelectric material and the n-type thermoelectric material includes a rare earth material in at least one ofmore » the p-type thermoelectric material or the n-type thermoelectric material.« less

  3. Thermoelectric Transport in Nanocomposites.

    PubMed

    Liu, Bin; Hu, Jizhu; Zhou, Jun; Yang, Ronggui

    2017-04-15

    Thermoelectric materials which can convert energies directly between heat and electricity are used for solid state cooling and power generation. There is a big challenge to improve the efficiency of energy conversion which can be characterized by the figure of merit ( ZT ). In the past two decades, the introduction of nanostructures into bulk materials was believed to possibly enhance ZT . Nanocomposites is one kind of nanostructured material system which includes nanoconstituents in a matrix material or is a mixture of different nanoconstituents. Recently, nanocomposites have been theoretically proposed and experimentally synthesized to be high efficiency thermoelectric materials by reducing the lattice thermal conductivity due to phonon-interface scattering and enhancing the electronic performance due to manipulation of electron scattering and band structures. In this review, we summarize the latest progress in both theoretical and experimental works in the field of nanocomposite thermoelectric materials. In particular, we present various models of both phonon transport and electron transport in various nanocomposites established in the last few years. The phonon-interface scattering, low-energy electrical carrier filtering effect, and miniband formation, etc., in nanocomposites are discussed.

  4. Low-temperature thermoelectric power factor enhancement by controlling nanoparticle size distribution.

    PubMed

    Zebarjadi, Mona; Esfarjani, Keivan; Bian, Zhixi; Shakouri, Ali

    2011-01-12

    Coherent potential approximation is used to study the effect of adding doped spherical nanoparticles inside a host matrix on the thermoelectric properties. This takes into account electron multiple scatterings that are important in samples with relatively high volume fraction of nanoparticles (>1%). We show that with large fraction of uniform small size nanoparticles (∼1 nm), the power factor can be enhanced significantly. The improvement could be large (up to 450% for GaAs) especially at low temperatures when the mobility is limited by impurity or nanoparticle scattering. The advantage of doping via embedded nanoparticles compared to the conventional shallow impurities is quantified. At the optimum thermoelectric power factor, the electrical conductivity of the nanoparticle-doped material is larger than that of impurity-doped one at the studied temperature range (50-500 K) whereas the Seebeck coefficient of the nanoparticle doped material is enhanced only at low temperatures (∼50 K).

  5. Enhanced thermoelectric performance in ternary spinel Cu4Mn2Te4via the synergistic effect of tellurium deficiency and chlorine doping.

    PubMed

    Chen, Hong; Lin, Hua; Liu, Yi; Wu, Xin-Tao; Wu, Li-Ming

    2017-11-07

    The chemistry of copper-based chalcogenides has received considerable attention due to their diverse structures and potential applications in the area of thermoelectric (TE) materials. In this communication, a series of spinel-type Cu 4 Mn 2 Te 4 -based samples have been successfully prepared and their high TE performances are attributed to the enhanced power factor and low thermal conductivity via the synergistic effect of Te deficiency and Cl doping. Consequently, a maximum TE figure of merit (ZT) of ∼0.4 was achieved for the Cu 4 Mn 2 Te 3.93 Cl 0.03 sample at 700 K, which was about 100% enhanced in comparison with the undoped Cu 4 Mn 2 Te 4 sample and one of the highest ZT values reported for p-type spinel tellurides.

  6. Heterogeneous in-situ nanostructure contributes to the thermoelectric performance of Zn{sub 4}Sb{sub 3}

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Lin, Jianping; Ma, Lingzhi; Yang, Baifeng

    Single-phase Zn{sub 4}Sb{sub 3} and ZnSb-containing samples were prepared by Plasma Activated Sintering. An abrupt decrease of thermal conductivity was found at about 400 K, which is attributed to the microstructure change of Zn{sub 4}Sb{sub 3}. Nanoscale inclusions and compositional inhomogeneities were found in Zn{sub 4}Sb{sub 3} sample at 473 K by high-resolution transmission electron microscopy. The phonon scattering is enhanced by increasing grain boundaries and chaotic structure, which reduces the thermal conductivity and increases the thermoelectric performance of Zn{sub 4}Sb{sub 3} at elevated temperature. The Rietveld refinement results show that large ZnSb grains in ZnSb-containing samples will accommodate excessmore » Zn atoms, and then reduce thermoelectric performance.« less

  7. Precise measurement of the performance of thermoelectric modules

    NASA Astrophysics Data System (ADS)

    Díaz-Chao, Pablo; Muñiz-Piniella, Andrés; Selezneva, Ekaterina; Cuenat, Alexandre

    2016-08-01

    The potential exploitation of thermoelectric modules into mass market applications such as exhaust gas heat recovery in combustion engines requires an accurate knowledge of their performance. Further expansion of the market will also require confidence on the results provided by suppliers to end-users. However, large variation in performance and maximum operating point is observed for identical modules when tested by different laboratories. Here, we present the first metrological study of the impact of mounting and testing procedures on the precision of thermoelectric modules measurement. Variability in the electrical output due to mechanical pressure or type of thermal interface materials is quantified for the first time. The respective contribution of the temperature difference and the mean temperature to the variation in the output performance is quantified. The contribution of these factors to the total uncertainties in module characterisation is detailed.

  8. Enhanced thermoelectric performance of β-Zn4Sb3 based nanocomposites through combined effects of density of states resonance and carrier energy filtering.

    PubMed

    Zou, Tianhua; Qin, Xiaoying; Zhang, Yongsheng; Li, Xiaoguang; Zeng, Zhi; Li, Di; Zhang, Jian; Xin, Hongxing; Xie, Wenjie; Weidenkaff, Anke

    2015-12-15

    It is a major challenge to elevate the thermoelectric figure of merit ZT of materials through enhancing their power factor (PF) and reducing the thermal conductivity at the same time. Experience has shown that engineering of the electronic density of states (eDOS) and the energy filtering mechanism (EFM) are two different effective approaches to improve the PF. However, the successful combination of these two methods is elusive. Here we show that the PF of β-Zn4Sb3 can greatly benefit from both effects. Simultaneous resonant distortion in eDOS via Pb-doping and energy filtering via introduction of interface potentials result in a ~40% increase of PF and an approximately twofold reduction of the lattice thermal conductivity due to interface scattering. Accordingly, the ZT of β-Pb0.02Zn3.98Sb3 with 3 vol.% of Cu3SbSe4 nanoinclusions reaches a value of 1.4 at 648 K. The combination of eDOS engineering and EFM would potentially facilitate the development of high-performance thermoelectric materials.

  9. Performance evaluation of an automotive thermoelectric generator

    NASA Astrophysics Data System (ADS)

    Dubitsky, Andrei O.

    Around 40% of the total fuel energy in typical internal combustion engines (ICEs) is rejected to the environment in the form of exhaust gas waste heat. Efficient recovery of this waste heat in automobiles can promise a fuel economy improvement of 5%. The thermal energy can be harvested through thermoelectric generators (TEGs) utilizing the Seebeck effect. In the present work, a versatile test bench has been designed and built in order to simulate conditions found on test vehicles. This allows experimental performance evaluation and model validation of automotive thermoelectric generators. An electrically heated exhaust gas circuit and a circulator based coolant loop enable integrated system testing of hot and cold side heat exchangers, thermoelectric modules (TEMs), and thermal interface materials at various scales. A transient thermal model of the coolant loop was created in order to design a system which can maintain constant coolant temperature under variable heat input. Additionally, as electrical heaters cannot match the transient response of an ICE, modelling was completed in order to design a relaxed exhaust flow and temperature history utilizing the system thermal lag. This profile reduced required heating power and gas flow rates by over 50%. The test bench was used to evaluate a DOE/GM initial prototype automotive TEG and validate analytical performance models. The maximum electrical power generation was found to be 54 W with a thermal conversion efficiency of 1.8%. It has been found that thermal interface management is critical for achieving maximum system performance, with novel designs being considered for further improvement.

  10. Universal thermoelectric unit

    NASA Astrophysics Data System (ADS)

    Fedorov, M. I.; Engalychev, A. E.; Zaitsev, V. K.; Kaliazin, A. E.; Solomkin, F. Yu.

    1994-08-01

    The problems of energy supply of low power electric devices very often can be solved with thermoelectric generator even with low coefficient of performance, when other electric energy sources are not convenient. The problems of thermoelectric and construction choice for such generators are discussed in the paper. A series of domestic thermoelectric generators was designed by the authors. The work is based on designing an universal thermoelectric unit—a battery which consist of ten thermoelements. The coefficient of performance of the unit is about 4%. Any thermoelectric generator can be made as a combination of these units. Principal opportunity of production such thermoelectric generators on industrial scale was proved.

  11. Fabrication of Bi–Sb–Te Thermoelectric by Cold-Pressed Sintering for Motorcycle Exhaust.

    PubMed

    Kao, Mu-Jung; Chen, Ming-Jing

    2017-04-01

    This study was conducted on the Bi–Sb–Te thermoelectric material which is cold-pressed Sintering under 750 Mpa to make square thermoelectric pairs with size 8.2 mm × 8.2 mm and thicknesses 0.8 mm and 1.5 mm. The zone melting method was used to acquire P-type thermoelectric material Bi0.4Sb1.6Te3 and N-type thermoelectric material Bi2Te2.5Se0.5. At temperature 383 K, the measured Seebeck coefficient of Bi0.4Sb1.6Te3 is 222 μV/K, and its thermoelectric figure of merit ZT is 1.35. At temperature 400 K, the measured Seebeck coefficient of Bi2Te2.5Se0.5 is 210 μV/K, and its thermoelectric figure of merit ZT is 1.13. Using Solder paste Sn42Bi58 and copper electrode plate are in series connection with 16 pieces of P/N thermoelectric material to form thermoelectric modules. The thermoelectric module is actually pasted on the motorcycle waste heat source to be evaluated the performance, making the cold-end temperature dissipation heat can enhance the temperature difference between it so as to increase the output power. Increasing the leg thickness of thermoelectric module and making the about 35 °C temperature-difference of those can obviously enhance the performance of in terms of its voltage, its thermoelectric figure of merit ZT and output power of the thermoelectric modules.

  12. Enhanced thermoelectric performance of In2O3-based ceramics via Nanostructuring and Point Defect Engineering

    PubMed Central

    Lan, Jin-Le; Liu, Yaochun; Lin, Yuan-Hua; Nan, Ce-Wen; Cai, Qing; Yang, Xiaoping

    2015-01-01

    The issue of how to improve the thermoelectric figure of merit (ZT) in oxide semiconductors has been challenging for more than 20 years. In this work, we report an effective path to substantial reduction in thermal conductivity and increment in carrier concentration, and thus a remarkable enhancement in the ZT value is achieved. The ZT value of In2O3 system was enhanced 4-fold by nanostructuing (nano-grains and nano-inclusions) and point defect engineering. The introduction of point defects in In2O3 results in a glass-like thermal conductivity. The lattice thermal conductivity could be reduced by 60%, and extraordinary low lattice thermal conductivity (1.2 W m−1 K−1 @ 973 K) below the amorphous limit was achieved. Our work paves a path for enhancing the ZT in oxides by both the nanosturcturing and the point defect engineering for better phonon-glasses and electron-crystal (PGEC) materials. PMID:25586762

  13. High Power Factor and Enhanced Thermoelectric Performance of SnTe-AgInTe2: Synergistic Effect of Resonance Level and Valence Band Convergence.

    PubMed

    Banik, Ananya; Shenoy, U Sandhya; Saha, Sujoy; Waghmare, Umesh V; Biswas, Kanishka

    2016-10-05

    Understanding the basis of electronic transport and developing ideas to improve thermoelectric power factor are essential for production of efficient thermoelectric materials. Here, we report a significantly large thermoelectric power factor of ∼31.4 μW/cm·K 2 at 856 K in Ag and In co-doped SnTe (i.e., SnAg x In x Te 1+2x ). This is the highest power factor so far reported for SnTe-based material, which arises from the synergistic effects of Ag and In on the electronic structure and the improved electrical transport properties of SnTe. In and Ag play different but complementary roles in modifying the valence band structure of SnTe. In-doping introduces resonance levels inside the valence bands, leading to a significant improvement in the Seebeck coefficient at room temperature. On the other hand, Ag-doping reduces the energy separation between light- and heavy-hole valence bands by widening the principal band gap, which also results in an improved Seebeck coefficient. Additionally, Ag-doping in SnTe enhances the p-type carrier mobility. Co-doping of In and Ag in SnTe yields synergistically enhanced Seebeck coefficient and power factor over a broad temperature range because of the synergy of the introduction of resonance states and convergence of valence bands, which have been confirmed by first-principles density functional theory-based electronic structure calculations. As a consequence, we have achieved an improved thermoelectric figure of merit, zT ≈ 1, in SnAg 0.025 In 0.025 Te 1.05 at 856 K.

  14. The Influence of the Inner Topology of Cooling Units on the Performance of Automotive Exhaust-Based Thermoelectric Generators

    NASA Astrophysics Data System (ADS)

    Zhu, D. C.; Su, C. Q.; Deng, Y. D.; Wang, Y. P.; Liu, X.

    2017-11-01

    Automotive exhaust-based thermoelectric generators are currently a hot topic in energy recovery. The waste heat of automotive exhaust gas can be converted into electricity by means of thermoelectric modules. Generally, inserting fins into the cooling unit contributes to enhancing the heat transfer for a higher power output. However, the introduction of fins will result in a pressure drop in the cooling system. In current research, in order to enhance the heat transfer and avoid a large pressure drop, a cooling unit with cylindrical grooves on the interior surface was proposed. To evaluate the performance of the cylindrical grooves, different inner topologies, including a smooth interior surface,a smooth interior surface with inserted fins and an interior surface with cylindrical grooves, were compared. The results revealed that compared with the smooth interior surface, the smooth interior surface with inserted fins and the interior surface with cylindrical grooves both enhanced the heat transfer, but the interior surface with cylindrical grooves obtained a lower pressure drop. To improve the performance of the cylindrical grooves, different groove-depth ratios were tried, and the results showed that a groove-depth ratio of 0.081 could provide the best overall performance.

  15. The Influence of the Inner Topology of Cooling Units on the Performance of Automotive Exhaust-Based Thermoelectric Generators

    NASA Astrophysics Data System (ADS)

    Zhu, D. C.; Su, C. Q.; Deng, Y. D.; Wang, Y. P.; Liu, X.

    2018-06-01

    Automotive exhaust-based thermoelectric generators are currently a hot topic in energy recovery. The waste heat of automotive exhaust gas can be converted into electricity by means of thermoelectric modules. Generally, inserting fins into the cooling unit contributes to enhancing the heat transfer for a higher power output. However, the introduction of fins will result in a pressure drop in the cooling system. In current research, in order to enhance the heat transfer and avoid a large pressure drop, a cooling unit with cylindrical grooves on the interior surface was proposed. To evaluate the performance of the cylindrical grooves, different inner topologies, including a smooth interior surface,a smooth interior surface with inserted fins and an interior surface with cylindrical grooves, were compared. The results revealed that compared with the smooth interior surface, the smooth interior surface with inserted fins and the interior surface with cylindrical grooves both enhanced the heat transfer, but the interior surface with cylindrical grooves obtained a lower pressure drop. To improve the performance of the cylindrical grooves, different groove-depth ratios were tried, and the results showed that a groove-depth ratio of 0.081 could provide the best overall performance.

  16. A Solution Processable High-Performance Thermoelectric Copper Selenide Thin Film.

    PubMed

    Lin, Zhaoyang; Hollar, Courtney; Kang, Joon Sang; Yin, Anxiang; Wang, Yiliu; Shiu, Hui-Ying; Huang, Yu; Hu, Yongjie; Zhang, Yanliang; Duan, Xiangfeng

    2017-06-01

    A solid-state thermoelectric device is attractive for diverse technological areas such as cooling, power generation and waste heat recovery with unique advantages of quiet operation, zero hazardous emissions, and long lifetime. With the rapid growth of flexible electronics and miniature sensors, the low-cost flexible thermoelectric energy harvester is highly desired as a potential power supply. Herein, a flexible thermoelectric copper selenide (Cu 2 Se) thin film, consisting of earth-abundant elements, is reported. The thin film is fabricated by a low-cost and scalable spin coating process using ink solution with a truly soluble precursor. The Cu 2 Se thin film exhibits a power factor of 0.62 mW/(m K 2 ) at 684 K on rigid Al 2 O 3 substrate and 0.46 mW/(m K 2 ) at 664 K on flexible polyimide substrate, which is much higher than the values obtained from other solution processed Cu 2 Se thin films (<0.1 mW/(m K 2 )) and among the highest values reported in all flexible thermoelectric films to date (≈0.5 mW/(m K 2 )). Additionally, the fabricated thin film shows great promise to be integrated with the flexible electronic devices, with negligible performance change after 1000 bending cycles. Together, the study demonstrates a low-cost and scalable pathway to high-performance flexible thin film thermoelectric devices from relatively earth-abundant elements. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  17. Life Testing of Yb14MnSb11 for High Performance Thermoelectric Couples

    NASA Technical Reports Server (NTRS)

    Paik, Jong-Ah; Brandon, Erik; Caillat, Thierry; Ewell, Richard; Fleurial, Jean-Pierre

    2011-01-01

    The goal of this study is to verify the long term stability of Yb14MnSb11 for high performance thermoelectric (TE) couples. Three main requirements need to be satisfied to ensure the long term stability of thermoelectric couples: 1) stable thermoelectric properties, 2) stable bonding interfaces, and 3) adequate sublimation suppression. The efficiency of the couple is primarily based on the thermoelectric properties of the materials selected for the couple. Therefore, these TE properties should exhibit minimal degradation during the operating period of the thermoelectric couples. The stability of the bonding is quantified by low contact resistances of the couple interfaces. In order to ensure high efficiency, the contact resistances of the bonding interfaces should be negligible. Sublimation suppression is important because the majority of thermoelectric materials used for power generation have peak figures of merit at temperatures where sublimation rates are high. Controlling sublimation is also essential to preserve the efficiency of the couple. During the course of this research, three different life tests were performed with Yb14MnSb11 coupons. TE properties of Yb14MnSb11 exhibited no degradation after 6 months of aging at 1273K, and the electrical contact resistance between a thin metallization layer and the Yb14MnSb11 remained negligible after 1500hr aging at 1273K. A sublimation suppression layer for Yb14MnSb11 was developed and demonstrated for more than 18 months with coupon testing at 1273K. These life test data indicate that thermoelectric elements based on Yb14MnSb11 are a promising technology for use in future high performance thermoelectric power generating couples.

  18. Thermochemically evolved nanoplatelets of bismuth selenide with enhanced thermoelectric figure of merit

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ali, Zulfiqar; Cao, Chuanbao, E-mail: cbcao@bit.edu.cn; Butt, Faheem K.

    We firstly present a simple thermochemical method to fabricate high-quality Bi{sub 2}Se{sub 3} nanoplatelets with enhanced figure of merit using elemental bismuth and selenium powders as precursors. The crystal structure of as synthesized products is characterized via X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and high resolution transmission electron microscopy (HRTEM) measurements. Morphological and chemical synthetic parameters are investigated through a series of experiments; thickness and composition of the platelets are well controlled in large scale production. Subsequently spark plasma sintering (SPS) is performed to fabricate n-type nanostructured bulk thermoelectric materials. Raman Spectroscopy of the two selected samples with approximatelymore » of 50 and 100 nm thicknesses shows three vibrational modes. The lower thickness sample exhibits the maximum red shift of about 2.17 cm{sup -1} and maximum broadening of about 10 cm{sup -1} by in-plane vibrational mode E{sup 2}{sub g}. The enhanced value of figure of merit ∼0.41 is obtained for pure phase bismuth selenide to the best of our knowledge. We observe metallic conduction behavior while semiconducting behavior for nanostructured bismuth selenide is reported elsewhere which could be due to different synthetic techniques adopted. These results clearly suggest that our adopted synthetic technique has profound effect on the electronic and thermoelectric transport properties of this material.« less

  19. Enhanced thermoelectric properties via oxygen non-stoichiometry in La2NiO4 and SrTiO3

    NASA Astrophysics Data System (ADS)

    Pardo, Victor; Botana, Antia S.; Bach, Paul M.; Leboran, Victor; Rivadulla, Francisco; Baldomir, Daniel

    2013-03-01

    We present the results of transport properties calculations and experiments on various oxides. A large enhancement of the thermoelectric properties is predicted[1] via ab initio calculations for La2NiO4+δ, with electronic-only thermoelectric figure of merit (zT) values exceeding unity for oxygen excess δ <= 0.10. The effects of lattice strain (caused, e.g. by growth of thin films on different substrates) enhance even further the thermoelectric response. A similar result is obtained at very low electron-doping in bulk SrTiO3 via oxygen removal. This is analyzed experimentally via thermal annealing that depletes oxygen (~ 1 oxygen vacancy per 106 unit cells). In both these systems, the increase in conductivity reached in the metallic limit retains a large thermopower, with the corresponding enhancement of zT . In the case of SrTiO3, experiments indicate[2] that such a small oxygen vacancy level reduces drastically the thermal conductivity by introducing random scattering centers. In the talk, we will discuss the electronic structure origin of the enhancement of the thermoelectric response and how this can be tuned. Results are general and applicable to other non-stoichiometric oxides.

  20. Enhanced thermoelectric performance of Bi2Te3 through uniform dispersion of single wall carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Ahmad, Kaleem; Wan, Chunlei

    2017-10-01

    The advancement in nanostructured powder processing has attracted great interest as a cost effective and scalable strategy for high performance thermoelectric bulk materials. However, the level of technical breakthrough realized in quantum dot supperlattices/wires has not yet been demonstrated in these materials. Here, we report the first ever study on the uniform dispersion of single wall carbon nanotubes (SWCNTs) in nanostructured Bi2Te3 bulk, and their effect on thermoelectric parameters above room temperature. The Bi2Te3 based SWCNT composites were prepared through controlled powder processing, and their thermoelectric properties were finely tuned at the nanoscale by regulating various (0.5, 0.75, 1.0 and 1.5) vol% of SWCNTs in the matrix. The flexible ropes of SWCNT, making an interconnected network through the inter/trans granular positions of Bi2Te3, thus substantially change the transport properties of the composites. The perfect one-dimensional (1D) conducting structure of SWCNTs acts as a source of electrical transport through a percolating network, with significantly suppressed lattice thermal conductivity, via intensified boundary scattering. The remarkable increase in power factor is ascribed to energy filtering effects and excellent electrical transport of 1D SWCNTs in the composites. Consequently, with a considerable reduction in thermal conductivity, the figure of merit culminates in a several-fold improvement, at 0.5 vol% of SWCNTs, over pristine bulk Bi2Te3.

  1. Enhanced thermoelectric performance of Bi2Te3 through uniform dispersion of single wall carbon nanotubes.

    PubMed

    Ahmad, Kaleem; Wan, Chunlei

    2017-10-13

    The advancement in nanostructured powder processing has attracted great interest as a cost effective and scalable strategy for high performance thermoelectric bulk materials. However, the level of technical breakthrough realized in quantum dot supperlattices/wires has not yet been demonstrated in these materials. Here, we report the first ever study on the uniform dispersion of single wall carbon nanotubes (SWCNTs) in nanostructured Bi 2 Te 3 bulk, and their effect on thermoelectric parameters above room temperature. The Bi 2 Te 3 based SWCNT composites were prepared through controlled powder processing, and their thermoelectric properties were finely tuned at the nanoscale by regulating various (0.5, 0.75, 1.0 and 1.5) vol% of SWCNTs in the matrix. The flexible ropes of SWCNT, making an interconnected network through the inter/trans granular positions of Bi 2 Te 3 , thus substantially change the transport properties of the composites. The perfect one-dimensional (1D) conducting structure of SWCNTs acts as a source of electrical transport through a percolating network, with significantly suppressed lattice thermal conductivity, via intensified boundary scattering. The remarkable increase in power factor is ascribed to energy filtering effects and excellent electrical transport of 1D SWCNTs in the composites. Consequently, with a considerable reduction in thermal conductivity, the figure of merit culminates in a several-fold improvement, at 0.5 vol% of SWCNTs, over pristine bulk Bi 2 Te 3 .

  2. Thermoelectric Transport in Nanocomposites

    PubMed Central

    Liu, Bin; Hu, Jizhu; Zhou, Jun; Yang, Ronggui

    2017-01-01

    Thermoelectric materials which can convert energies directly between heat and electricity are used for solid state cooling and power generation. There is a big challenge to improve the efficiency of energy conversion which can be characterized by the figure of merit (ZT). In the past two decades, the introduction of nanostructures into bulk materials was believed to possibly enhance ZT. Nanocomposites is one kind of nanostructured material system which includes nanoconstituents in a matrix material or is a mixture of different nanoconstituents. Recently, nanocomposites have been theoretically proposed and experimentally synthesized to be high efficiency thermoelectric materials by reducing the lattice thermal conductivity due to phonon-interface scattering and enhancing the electronic performance due to manipulation of electron scattering and band structures. In this review, we summarize the latest progress in both theoretical and experimental works in the field of nanocomposite thermoelectric materials. In particular, we present various models of both phonon transport and electron transport in various nanocomposites established in the last few years. The phonon-interface scattering, low-energy electrical carrier filtering effect, and miniband formation, etc., in nanocomposites are discussed. PMID:28772777

  3. How much improvement in thermoelectric performance can come from reducing thermal conductivity?

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Gaultois, Michael W., E-mail: mgaultois@mrl.ucsb.edu; Sparks, Taylor D., E-mail: sparks@eng.utah.edu

    Large improvements in the performance of thermoelectric materials have come from designing materials with reduced thermal conductivity. Yet as the thermal conductivity of some materials now approaches their amorphous limit, it is unclear if microstructure engineering can further improve thermoelectric performance in these cases. In this contribution, we use large data sets to examine 300 compositions in 11 families of thermoelectric materials and present a type of plot that quickly reveals the maximum possible zT that can be achieved by reducing the thermal conductivity. This plot allows researchers to quickly distinguish materials where the thermal conductivity has been optimized frommore » those where improvement can be made. Moreover, through these large data sets we examine structure-property relationships to identify methods that decrease thermal conductivity and improve thermoelectric performance. We validate, with the data, that increasing (i) the volume of a unit cell and/or (ii) the number of atoms in the unit cell decreases the thermal conductivity of many classes of materials, without changing the electrical resistivity.« less

  4. Reliable Thermoelectric Module Design under Opposing Requirements from Structural and Thermoelectric Considerations

    NASA Astrophysics Data System (ADS)

    Karri, Naveen K.; Mo, Changki

    2018-06-01

    Structural reliability of thermoelectric generation (TEG) systems still remains an issue, especially for applications such as large-scale industrial or automobile exhaust heat recovery, in which TEG systems are subject to dynamic loads and thermal cycling. Traditional thermoelectric (TE) system design and optimization techniques, focused on performance alone, could result in designs that may fail during operation as the geometric requirements for optimal performance (especially the power) are often in conflict with the requirements for mechanical reliability. This study focused on reducing the thermomechanical stresses in a TEG system without compromising the optimized system performance. Finite element simulations were carried out to study the effect of TE element (leg) geometry such as leg length and cross-sectional shape under constrained material volume requirements. Results indicated that the element length has a major influence on the element stresses whereas regular cross-sectional shapes have minor influence. The impact of TE element stresses on the mechanical reliability is evaluated using brittle material failure theory based on Weibull analysis. An alternate couple configuration that relies on the industry practice of redundant element design is investigated. Results showed that the alternate configuration considerably reduced the TE element and metallization stresses, thereby enhancing the structural reliability, with little trade-off in the optimized performance. The proposed alternate configuration could serve as a potential design modification for improving the reliability of systems optimized for thermoelectric performance.

  5. Enhancement of thermoelectric figure of merit in zigzag graphene nanoribbons with periodic edge vacancies

    NASA Astrophysics Data System (ADS)

    Kolesnikov, D. V.; Sadykova, O. G.; Osipov, V. A.

    2017-06-01

    The influence of periodic edge vacancies and antidot arrays on the thermoelectric properties of zigzag graphene nanoribbons (ZGNRs) are investigated. Using Green’s function method, the tight-binding approximation for the electron Hamiltonian and the 4th nearest neighbor approximation for the phonon dynamical matrix, we calculate the Seebeck coefficient and the thermoelectric figure of merit. It is found that, at a certain periodic arrangement of vacancies on both edges of zigzag nanoribbon, a finite band gap opens and almost twofold degenerate energy levels appear. As a result, a marked increase in the Seebeck coefficient takes place. It is shown that an additional enhancement of the thermoelectric figure of merit can be achieved by a combination of periodic edge defects with an antidot array.

  6. Thermoelectric Signal Enhancement by Reconciling the Spin Seebeck and Anomalous Nernst Effects in Ferromagnet/Non-magnet Multilayers

    PubMed Central

    Lee, Kyeong-Dong; Kim, Dong-Jun; Yeon Lee, Hae; Kim, Seung-Hyun; Lee, Jong-Hyun; Lee, Kyung-Min; Jeong, Jong-Ryul; Lee, Ki-Suk; Song, Hyon-Seok; Sohn, Jeong-Woo; Shin, Sung-Chul; Park, Byong-Guk

    2015-01-01

    The utilization of ferromagnetic (FM) materials in thermoelectric devices allows one to have a simpler structure and/or independent control of electric and thermal conductivities, which may further remove obstacles for this technology to be realized. The thermoelectricity in FM/non-magnet (NM) heterostructures using an optical heating source is studied as a function of NM materials and a number of multilayers. It is observed that the overall thermoelectric signal in those structures which is contributed by spin Seebeck effect and anomalous Nernst effect (ANE) is enhanced by a proper selection of NM materials with a spin Hall angle that matches to the sign of the ANE. Moreover, by an increase of the number of multilayer, the thermoelectric voltage is enlarged further and the device resistance is reduced, simultaneously. The experimental observation of the improvement of thermoelectric properties may pave the way for the realization of magnetic-(or spin-) based thermoelectric devices. PMID:26020492

  7. Thermoelectric Signal Enhancement by Reconciling the Spin Seebeck and Anomalous Nernst Effects in Ferromagnet/Non-magnet Multilayers.

    PubMed

    Lee, Kyeong-Dong; Kim, Dong-Jun; Yeon Lee, Hae; Kim, Seung-Hyun; Lee, Jong-Hyun; Lee, Kyung-Min; Jeong, Jong-Ryul; Lee, Ki-Suk; Song, Hyon-Seok; Sohn, Jeong-Woo; Shin, Sung-Chul; Park, Byong-Guk

    2015-05-28

    The utilization of ferromagnetic (FM) materials in thermoelectric devices allows one to have a simpler structure and/or independent control of electric and thermal conductivities, which may further remove obstacles for this technology to be realized. The thermoelectricity in FM/non-magnet (NM) heterostructures using an optical heating source is studied as a function of NM materials and a number of multilayers. It is observed that the overall thermoelectric signal in those structures which is contributed by spin Seebeck effect and anomalous Nernst effect (ANE) is enhanced by a proper selection of NM materials with a spin Hall angle that matches to the sign of the ANE. Moreover, by an increase of the number of multilayer, the thermoelectric voltage is enlarged further and the device resistance is reduced, simultaneously. The experimental observation of the improvement of thermoelectric properties may pave the way for the realization of magnetic-(or spin-) based thermoelectric devices.

  8. Synergistic Strategy to Enhance the Thermoelectric Properties of CoSbS1-xSex Compounds via Solid Solution.

    PubMed

    Yao, Wei; Yang, Dingfeng; Yan, Yanci; Peng, Kunling; Zhan, Heng; Liu, Anping; Lu, Xu; Wang, Guoyu; Zhou, Xiaoyuan

    2017-03-29

    High thermal conductivity of CoSbS-based limited its own prospect application in thermoelectric energy conversion. Solid solution is an effective approach to optimize the performance of thermoelectric materials with high lattice thermal conductivity because of the enhanced phonons scattering from disorder atoms. In this paper, we have synthesized and measured the thermoelectric properties of solid solution CoSbS 1-x Se x (x = 0, 0.05, 0.10, 0.15, 0.20, 0.30) series samples. The collaborative optimization (enhancing the power factors and reducing the thermal conductivities) to add zT values were realized via substitution of S atoms with the isoelectronic Se atoms in the matrix. Meanwhile, the lowest room temperature lattice thermal conductivity in CoSbS-based materials is obtained (4.72 W m -1 K -1 ) at present. Benefiting from the results of synergistic strategy, a zT of 0.35 was achieved at 923 K for sample CoSbS 0.85 Se 0.15 , a 59% improvement as compared with that of the pristine CoSbS. Band calculation demonstrated that CoSbS 0.85 Se 0.15 present a similar band dispersion with CoSbS. The mechanism of point defect scattering for reducing the lattice thermal conductivity at room temperature, was also analyzed by the Callaway model. The contributions to decrease the room temperature lattice thermal conductivity from the mass and the strain fluctuation in the crystal are comparable. These results can also be extended to other high-efficiency thermoelectric materials with stiff bond and smaller Gruneisen parameters.

  9. Enhancement of Thermoelectric Properties in SnTe with (Ag, In) Co-Doping

    NASA Astrophysics Data System (ADS)

    Li, J. Q.; Yang, N.; Li, S. M.; Li, Y.; Liu, F. S.; Ao, W. Q.

    2018-01-01

    A lead-free SnTe compound shows good electrical property but high thermal conductivity, resulting in a low figure-of-merit ZT. We present a significant enhancement of the thermoelectric properties of p-type SnTe with (Ag, In) co-doping. The Ag and In co-doped Sn1-2 x Ag x In x Te ( x = 0.00, 0.01, 0.02, 0.03, 0.04 and 0.05) are prepared by melting, quenching and spark plasma sintering. A homogeneous NaCl-type SnTe-based solid solution forms in the alloys at low Ag and In content ( x ≤ 0.02), while a AgInTe2 minor secondary phase precipitates for higher x. Similar to In doping, the introduction of Ag and In at Sn sites in SnTe considerably increases the Seebeck coefficient and power factor by creating resonant levels near the Fermi energy. In addition, the Ag and In solute atoms in the SnTe-based solid solution and the minor secondary phase AgInTe2 enhance phonon scattering and thus significantly reduce the carrier and lattice thermal conductivity. Ag and In co-doping shows a collective advantage on the overall thermoelectric performance of SnTe or In-doped SnTe. A maximum ZT of 1.23 at 873 K and average ZT of 0.58 can be obtained in the alloy Sn1-2 x Ag x In x Te with x = 0.03.

  10. Hierarchical Architecturing for Layered Thermoelectric Sulfides and Chalcogenides.

    PubMed

    Jood, Priyanka; Ohta, Michihiro

    2015-03-16

    Sulfides are promising candidates for environment-friendly and cost-effective thermoelectric materials. In this article, we review the recent progress in all-length-scale hierarchical architecturing for sulfides and chalcogenides, highlighting the key strategies used to enhance their thermoelectric performance. We primarily focus on TiS₂-based layered sulfides, misfit layered sulfides, homologous chalcogenides, accordion-like layered Sn chalcogenides, and thermoelectric minerals. CS₂ sulfurization is an appropriate method for preparing sulfide thermoelectric materials. At the atomic scale, the intercalation of guest atoms/layers into host crystal layers, crystal-structural evolution enabled by the homologous series, and low-energy atomic vibration effectively scatter phonons, resulting in a reduced lattice thermal conductivity. At the nanoscale, stacking faults further reduce the lattice thermal conductivity. At the microscale, the highly oriented microtexture allows high carrier mobility in the in-plane direction, leading to a high thermoelectric power factor.

  11. Hierarchical Architecturing for Layered Thermoelectric Sulfides and Chalcogenides

    PubMed Central

    Jood, Priyanka; Ohta, Michihiro

    2015-01-01

    Sulfides are promising candidates for environment-friendly and cost-effective thermoelectric materials. In this article, we review the recent progress in all-length-scale hierarchical architecturing for sulfides and chalcogenides, highlighting the key strategies used to enhance their thermoelectric performance. We primarily focus on TiS2-based layered sulfides, misfit layered sulfides, homologous chalcogenides, accordion-like layered Sn chalcogenides, and thermoelectric minerals. CS2 sulfurization is an appropriate method for preparing sulfide thermoelectric materials. At the atomic scale, the intercalation of guest atoms/layers into host crystal layers, crystal-structural evolution enabled by the homologous series, and low-energy atomic vibration effectively scatter phonons, resulting in a reduced lattice thermal conductivity. At the nanoscale, stacking faults further reduce the lattice thermal conductivity. At the microscale, the highly oriented microtexture allows high carrier mobility in the in-plane direction, leading to a high thermoelectric power factor. PMID:28787992

  12. Nanostructures having high performance thermoelectric properties

    DOEpatents

    Yang, Peidong; Majumdar, Arunava; Hochbaum, Allon I.; Chen, Renkun; Delgado, Raul Diaz

    2015-12-22

    The invention provides for a nanostructure, or an array of such nanostructures, each comprising a rough surface, and a doped or undoped semiconductor. The nanostructure is an one-dimensional (1-D) nanostructure, such a nanowire, or a two-dimensional (2-D) nanostructure. The nanostructure can be placed between two electrodes and used for thermoelectric power generation or thermoelectric cooling.

  13. Nanostructures having high performance thermoelectric properties

    DOEpatents

    Yang, Peidong; Majumdar, Arunava; Hochbaum, Allon I; Chen, Renkun; Delgado, Raul Diaz

    2014-05-20

    The invention provides for a nanostructure, or an array of such nanostructures, each comprising a rough surface, and a doped or undoped semiconductor. The nanostructure is an one-dimensional (1-D) nanostructure, such a nanowire, or a two-dimensional (2-D) nanostructure. The nanostructure can be placed between two electrodes and used for thermoelectric power generation or thermoelectric cooling.

  14. Highly Enhanced Thermoelectric Properties of Bi/Bi2S3 Nanocomposites.

    PubMed

    Ge, Zhen-Hua; Qin, Peng; He, DongSheng; Chong, Xiaoyu; Feng, Dan; Ji, Yi-Hong; Feng, Jing; He, Jiaqing

    2017-02-08

    Bismuth sulfide (Bi 2 S 3 ) has been of high interest for thermoelectric applications due to the high abundance of sulfur on Earth. However, the low electrical conductivity of pristine Bi 2 S 3 results in a low figure of merit (ZT). In this work, Bi 2 S 3 @Bi core-shell nanowires with different Bi shell thicknesses were prepared by a hydrothermal method. The core-shell nanowires were densified to Bi/Bi 2 S 3 nanocomposite by spark plasma sintering (SPS), and the structure of the nanowire was maintained as the nanocomposite due to rapid SPS processing and low sintering temperature. The thermoelectric properties of bulk samples were investigated. The electrical conductivity of a bulk sample after sintering at 673 K for 5 min using Bi 2 S 3 @Bi nanowire powders prepared by treating Bi 2 S 3 nanowires in a hydrazine solution for 3 h is 3 orders of magnitude greater than that of a pristine Bi 2 S 3 sample. The nanocomposite possessed the highest ZT value of 0.36 at 623 K. This represents a new strategy for densifying core-shell powders to enhance their thermoelectric properties.

  15. On the best bandstructure for thermoelectric performance: A Landauer perspective

    NASA Astrophysics Data System (ADS)

    Jeong, Changwook; Kim, Raseong; Lundstrom, Mark S.

    2012-06-01

    The question of what bandstructure produces the best thermoelectric device performance is revisited from a Landauer perspective. We find that a delta-function transport distribution function (TDF) results in operation at the Mahan-Sofo upper limit for the thermoelectric figure-of-merit, ZT. We show, however, the Mahan-Sofo upper limit itself depends on the bandwidth (BW) of the dispersion, and therefore, a finite BW dispersion produces a higher ZT when the lattice thermal conductivity is finite. Including a realistic model for scattering profoundly changes the results. Instead of a narrow band, we find that a broad BW is best. The prospects of increasing ZT through high valley degeneracy or by distorting the density-of-states are discussed from a Landauer perspective. We conclude that while there is no simple answer to the question of what bandstructure produces the best thermoelectric performance, the important considerations can be expressed in terms of three parameters derived from the bandstructure—the density-of-states, D(E ), the number of channels, M(E ), and the mean-free-path, λ(E ).

  16. An efficient mechanism for enhancing the thermoelectricity of nanoribbons by blocking phonon transport in 2D materials.

    PubMed

    Liu, Yue-Yang; Zeng, Yu-Jia; Jia, Pin-Zhen; Cao, Xuan-Hao; Jiang, Xiangwei; Chen, Ke-Qiu

    2018-07-11

    Inspired by the novel mechanism of reducing thermal conductivity by local phonon resonance instead of by inducing structural defects, we investigate the effect of side branching on the thermoelectric properties of [Formula: see text] nanoribbons, and prove that side branching is a highly efficient mechanism for enhancing the thermoelectricity of different kinds of nanoribbons. For both armchair and zigzag [Formula: see text] nanoribbons, the side branches result in not only significant blocking of phonon transport but also notable increase of the Seebeck coefficient. Consequently, the thermoelectric figure of merit of the armchair [Formula: see text] nanoribbon is boosted from 0.72 to as high as 1.93, and the originally non-thermoelectric metallic zigzag [Formula: see text] nanoribbon is turned into a thermoelectric material due to the appearance of the band gap induced by the side branches. These results mean that the mechanism of branching is not only very efficient, but also takes effect regardless of the original properties of the nanoribbons, and thus will hold great promise for its application in the thermoelectric field.

  17. Benefits of Carrier-Pocket Anisotropy to Thermoelectric Performance: The Case of p -Type AgBiSe 2

    DOE PAGES

    Parker, David S.; May, Andrew F.; Singh, David J.

    2015-06-05

    Here we study theoretically the effects of anisotropy on the thermoelectric performance of p-type AgBiSe 2. We present an apparent realization of the thermoelectric benefits of one-dimensional plate-like carrier pocket anisotropy in the valence band of this material. Based on first principles calculations we find a substantial anisotropy in the electronic structure, likely favorable for thermoelectric performance, in the valence bands of the hexagonal phase of the silver chalcogenide thermoelectric AgBiSe 2, while the conduction bands are more isotropic, and in our experiments do not attain high performance. AgBiSe 2 has already exhibited a ZT value of 1.5 in amore » high-temperature disordered fcc phase, but room-temperature performance has not been demonstrated. We develop a theory for the ability of anisotropy to decouple the density-of-states and conductivity effective masses, pointing out the influence of this effect in the high performance thermoelectrics Bi 2Te 3 and PbTe. From our first principles and Boltzmann transport calculations we find that p-type AgBiSe 2 has substantial promise as a room temperature thermoelectric, and estimate its performance.« less

  18. Thermoelectric efficiency enhanced in a quantum dot with polarization leads, spin-flip and external magnetic field

    NASA Astrophysics Data System (ADS)

    Yao, Hui; Niu, Peng-Bin; Zhang, Chao; Xu, Wei-Ping; Li, Zhi-Jian; Nie, Yi-Hang

    2018-03-01

    We theoretically study the thermoelectric transport properties in a quantum dot system with two ferromagnetic leads, the spin-flip scattering and the external magnetic field. The results show that the spin polarization of the leads strongly influences thermoelectric coefficients of the device. For the parallel configuration the peak of figure of merit increases with the increase of polarization strength and non-collinear configuration trends to destroy the improvement of figure of merit induced by lead polarization. While the modulation of the spin-flip scattering on the figure of merit is effective only in the absence of external magnetic field or small magnetic field. In terms of improving the thermoelectric efficiency, the external magnetic field plays a more important role than spin-flip scattering. The thermoelectric efficiency can be significantly enhanced by the magnetic field for a given spin-flip scattering strength.

  19. Synthesis of the thermoelectric nanopowder recovered from the used thermoelectric modules.

    PubMed

    Lee, Kun-Jae; Jin, Yun-Ho; Kong, Man-Sik

    2014-10-01

    We fabricated the thermoelectric powder using the used thermoelectric modules in a vehicle. As a starting material, the used thermoelectric modules were collected and separated to substrate, electrode, solder, and thermoelectric parts by a thermal process. The separation process was performed in a wet process at the critical temperature. The solder in the module was the neighbor part of the thermoelectric material with the lowest melting temperature in the module. We focused on the thermal property of the solder to separate the thermoelectric chips in the module. After the separation process, we prepared the pure thermoelectric material by the chemical etching for an impurity removal. Also the thermoelectric nanopowder was fabricated by a chemical reduction reaction using the recycled thermoelectric materials. The recovered nanopowder was confirmed to the phase of bismuth telluride (Bi2Te3) with the particle size of -15 nm.

  20. Enhanced thermoelectric property of oxygen deficient nickel doped SnO2 for high temperature application

    NASA Astrophysics Data System (ADS)

    Paulson, Anju; Sabeer, N. A. Muhammad; Pradyumnan, P. P.

    2018-04-01

    Motivated by the detailed investigation on the thermoelectric performance of oxide materials our work concentrated on the influence of acceptor dopants and defect density in the lattice plane for the enhancement of thermoelectric power. The series of Sn1‑x Nix O2 (0.01 ≤ x ≤ 0.05) compositions were prepared by solid state reaction mechanism and found that 3 atomic percentage Ni doped SnO2 can be considered as a good candidate due to its promising electrical and transport properties. Defect lattices were introduced in the sample and the deviation from oxygen stochiometry was ensured using photoluminescence measurement. High power factor was obtained for the 3 atomic percentage nickel doped SnO2 due to the effective number of charge carrier concentration and the depletion of oxygen rich layers. Defect centered and acceptor doped SnO2 lattice opens a new door for energy harvesting at higher temperatures.

  1. Superlattice design for optimal thermoelectric generator performance

    NASA Astrophysics Data System (ADS)

    Priyadarshi, Pankaj; Sharma, Abhishek; Mukherjee, Swarnadip; Muralidharan, Bhaskaran

    2018-05-01

    We consider the design of an optimal superlattice thermoelectric generator via the energy bandpass filter approach. Various configurations of superlattice structures are explored to obtain a bandpass transmission spectrum that approaches the ideal ‘boxcar’ form, which is now well known to manifest the largest efficiency at a given output power in the ballistic limit. Using the coherent non-equilibrium Green’s function formalism coupled self-consistently with the Poisson’s equation, we identify such an ideal structure and also demonstrate that it is almost immune to the deleterious effect of self-consistent charging and device variability. Analyzing various superlattice designs, we conclude that superlattice with a Gaussian distribution of the barrier thickness offers the best thermoelectric efficiency at maximum power. It is observed that the best operating regime of this device design provides a maximum power in the range of 0.32–0.46 MW/m 2 at efficiencies between 54%–43% of Carnot efficiency. We also analyze our device designs with the conventional figure of merit approach to counter support the results so obtained. We note a high zT el   =  6 value in the case of Gaussian distribution of the barrier thickness. With the existing advanced thin-film growth technology, the suggested superlattice structures can be achieved, and such optimized thermoelectric performances can be realized.

  2. Thermoelectrics. Dense dislocation arrays embedded in grain boundaries for high-performance bulk thermoelectrics.

    PubMed

    Kim, Sang Il; Lee, Kyu Hyoung; Mun, Hyeon A; Kim, Hyun Sik; Hwang, Sung Woo; Roh, Jong Wook; Yang, Dae Jin; Shin, Weon Ho; Li, Xiang Shu; Lee, Young Hee; Snyder, G Jeffrey; Kim, Sung Wng

    2015-04-03

    The widespread use of thermoelectric technology is constrained by a relatively low conversion efficiency of the bulk alloys, which is evaluated in terms of a dimensionless figure of merit (zT). The zT of bulk alloys can be improved by reducing lattice thermal conductivity through grain boundary and point-defect scattering, which target low- and high-frequency phonons. Dense dislocation arrays formed at low-energy grain boundaries by liquid-phase compaction in Bi(0.5)Sb(1.5)Te3 (bismuth antimony telluride) effectively scatter midfrequency phonons, leading to a substantially lower lattice thermal conductivity. Full-spectrum phonon scattering with minimal charge-carrier scattering dramatically improved the zT to 1.86 ± 0.15 at 320 kelvin (K). Further, a thermoelectric cooler confirmed the performance with a maximum temperature difference of 81 K, which is much higher than current commercial Peltier cooling devices. Copyright © 2015, American Association for the Advancement of Science.

  3. High thermoelectric performances of monolayer SnSe allotropes.

    PubMed

    Hu, Zi-Yu; Li, Kai-Yue; Lu, Yong; Huang, Yan; Shao, Xiao-Hong

    2017-10-26

    α-SnSe is one of the most promising thermoelectric materials with low thermal conductivity and a high power factor. Since the thermoelectric properties of a material have a strong dependence on its crystal structure, we study the energetic and thermoelectric properties of four new monolayer phases of SnSe (β, γ, δ and ε) together with α-SnSe using the ab initio density functional theory method. The calculated electronic structures show that all five phases are semiconductors with different band gaps. The α, β, γ, and δ phases have an indirect band gap with the hybridization of sp 2 orbitals, whereas the ε phase has a direct band with the hybridization of sp 3 orbitals. The thermoelectric transport properties and coefficients are obtained from the electronic structure using semi-classical Boltzmann theory, and the results indicate that the four new phases of SnSe (β, γ, δ and ε) all have better thermoelectric properties compared with the reported α phase. The predicted ZT value for the β-SnSe phase is 2.06 at 300 K, suggesting that it has great potential for novel thermoelectric applications.

  4. High Performance High Temperature Thermoelectric Composites with Metallic Inclusions

    NASA Technical Reports Server (NTRS)

    Firdosy, Samad A. (Inventor); Kaner, Richard B. (Inventor); Ma, James M. (Inventor); Fleurial, Jean-Pierre (Inventor); Star, Kurt (Inventor); Bux, Sabah K. (Inventor); Ravi, Vilupanur A. (Inventor)

    2017-01-01

    The present invention provides a composite thermoelectric material. The composite thermoelectric material can include a semiconductor material comprising a rare earth metal. The atomic percent of the rare earth metal in the semiconductor material can be at least about 20%. The composite thermoelectric material can further include a metal forming metallic inclusions distributed throughout the semiconductor material. The present invention also provides a method of forming this composite thermoelectric material.

  5. Interpreting the Combustion Process for High-Performance ZrNiSn Thermoelectric Materials.

    PubMed

    Hu, Tiezheng; Yang, Dongwang; Su, Xianli; Yan, Yonggao; You, Yonghui; Liu, Wei; Uher, Ctirad; Tang, Xinfeng

    2018-01-10

    The ZrNiSn alloy, a member of the half-Heusler family of thermoelectric materials, shows great potential for mid-to-high-temperature power generation applications due to its excellent thermoelectric properties, robust mechanical properties, and good thermal stability. The existing synthesis processes of half-Heusler alloys are, however, rather time and energy intensive. In this study, single-phase ZrNiSn bulk materials were prepared by self-propagating high-temperature synthesis (SHS) combined with spark plasma sintering (SPS) for the first time. The analysis of thermodynamic and kinetic processes shows that the SHS reaction in the ternary ZrNiSn alloy is different from the more usual binary systems. It consists of a series of SHS reactions and mass transfers triggered by the SHS fusion of the binary Ni-Sn system that eventually culminates in the formation of single-phase ternary ZrNiSn in a very short time, which reduced the synthesis period from few days to less than an hour. Moreover, the nonequilibrium feature induces Ni interstitials in the structure, which simultaneously enhances the electrical conductivity and decreases the thermal conductivity, which is favorable for thermoelectric properties. The maximum thermoelectric figure of merit ZT of the SHS + SPS-processed ZrNiSn 1-x Sb x alloy reached 0.7 at 870 K. This study opens a new avenue for the fast and low-cost fabrication of half-Heusler thermoelectric materials.

  6. Nanowire Thermoelectric Devices

    NASA Technical Reports Server (NTRS)

    Borshchevsky, Alexander; Fleurial, Jean-Pierre; Herman, Jennifer; Ryan, Margaret

    2005-01-01

    Nanowire thermoelectric devices, now under development, are intended to take miniaturization a step beyond the prior state of the art to exploit the potential advantages afforded by shrinking some device features to approximately molecular dimensions (of the order of 10 nm). The development of nanowire-based thermoelectric devices could lead to novel power-generating, cooling, and sensing devices that operate at relatively low currents and high voltages. Recent work on the theory of thermoelectric devices has led to the expectation that the performance of such a device could be enhanced if the diameter of the wires could be reduced to a point where quantum confinement effects increase charge-carrier mobility (thereby increasing the Seebeck coefficient) and reduce thermal conductivity. In addition, even in the absence of these effects, the large aspect ratios (length of the order of tens of microns diameter of the order of tens of nanometers) of nanowires would be conducive to the maintenance of large temperature differences at small heat fluxes. The predicted net effect of reducing diameters to the order of tens of nanometers would be to increase its efficiency by a factor of .3. Nanowires made of thermoelectric materials and devices that comprise arrays of such nanowires can be fabricated by electrochemical growth of the thermoelectric materials in templates that contain suitably dimensioned pores (10 to 100 nm in diameter and 1 to 100 microns long). The nanowires can then be contacted in bundles to form devices that look similar to conventional thermoelectric devices, except that a production version may contain nearly a billion elements (wires) per square centimeter, instead of fewer than a hundred as in a conventional bulk thermoelectric device or fewer than 100,000 as in a microdevice. It is not yet possible to form contacts with individual nanowires. Therefore, in fabricating a nanowire thermoelectric device, one forms contacts on nanowires in bundles of the

  7. Solid-State Explosive Reaction for Nanoporous Bulk Thermoelectric Materials.

    PubMed

    Zhao, Kunpeng; Duan, Haozhi; Raghavendra, Nunna; Qiu, Pengfei; Zeng, Yi; Zhang, Wenqing; Yang, Jihui; Shi, Xun; Chen, Lidong

    2017-11-01

    High-performance thermoelectric materials require ultralow lattice thermal conductivity typically through either shortening the phonon mean free path or reducing the specific heat. Beyond these two approaches, a new unique, simple, yet ultrafast solid-state explosive reaction is proposed to fabricate nanoporous bulk thermoelectric materials with well-controlled pore sizes and distributions to suppress thermal conductivity. By investigating a wide variety of functional materials, general criteria for solid-state explosive reactions are built upon both thermodynamics and kinetics, and then successfully used to tailor material's microstructures and porosity. A drastic decrease in lattice thermal conductivity down below the minimum value of the fully densified materials and enhancement in thermoelectric figure of merit are achieved in porous bulk materials. This work demonstrates that controlling materials' porosity is a very effective strategy and is easy to be combined with other approaches for optimizing thermoelectric performance. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  8. High-performance and compact-designed flexible thermoelectric modules enabled by a reticulate carbon nanotube architecture

    PubMed Central

    Zhou, Wenbin; Fan, Qingxia; Zhang, Qiang; Cai, Le; Li, Kewei; Gu, Xiaogang; Yang, Feng; Zhang, Nan; Wang, Yanchun; Liu, Huaping; Zhou, Weiya; Xie, Sishen

    2017-01-01

    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. Inspired by the findings, we design and successfully fabricate the compact-configuration flexible TE modules, which own great advantages compared with the conventional π-type configuration modules and well integrate the superior thermoelectric properties of p-type and n-type carbon nanotube films resulting in a markedly high performance. Moreover, the research results are highly scalable and also open opportunities for the large-scale production of flexible thermoelectric modules. PMID:28337987

  9. Extraordinary Off-Stoichiometric Bismuth Telluride for Enhanced n-Type Thermoelectric Power Factor.

    PubMed

    Park, Kunsu; Ahn, Kyunghan; Cha, Joonil; Lee, Sanghwa; Chae, Sue In; Cho, Sung-Pyo; Ryee, Siheon; Im, Jino; Lee, Jaeki; Park, Su-Dong; Han, Myung Joon; Chung, In; Hyeon, Taeghwan

    2016-11-02

    Thermoelectrics directly converts waste heat into electricity and is considered a promising means of sustainable energy generation. While most of the recent advances in the enhancement of the thermoelectric figure of merit (ZT) resulted from a decrease in lattice thermal conductivity by nanostructuring, there have been very few attempts to enhance electrical transport properties, i.e., the power factor. Here we use nanochemistry to stabilize bulk bismuth telluride (Bi 2 Te 3 ) that violates phase equilibrium, namely, phase-pure n-type K 0.06 Bi 2 Te 3.18 . Incorporated potassium and tellurium in Bi 2 Te 3 far exceed their solubility limit, inducing simultaneous increase in the electrical conductivity and the Seebeck coefficient along with decrease in the thermal conductivity. Consequently, a high power factor of ∼43 μW cm -1 K -2 and a high ZT > 1.1 at 323 K are achieved. Our current synthetic method can be used to produce a new family of materials with novel physical and chemical characteristics for various applications.

  10. Thermoelectric properties and performance of flexible reduced graphene oxide films up to 3,000 K

    NASA Astrophysics Data System (ADS)

    Li, Tian; Pickel, Andrea D.; Yao, Yonggang; Chen, Yanan; Zeng, Yuqiang; Lacey, Steven D.; Li, Yiju; Wang, Yilin; Dai, Jiaqi; Wang, Yanbin; Yang, Bao; Fuhrer, Michael S.; Marconnet, Amy; Dames, Chris; Drew, Dennis H.; Hu, Liangbing

    2018-02-01

    The development of ultrahigh-temperature thermoelectric materials could enable thermoelectric topping of combustion power cycles as well as extending the range of direct thermoelectric power generation in concentrated solar power. However, thermoelectric operation temperatures have been restricted to under 1,500 K due to the lack of suitable materials. Here, we demonstrate a thermoelectric conversion material based on high-temperature reduced graphene oxide nanosheets that can perform reliably up to 3,000 K. After a reduction treatment at 3,300 K, the nanosheet film exhibits an increased conductivity to 4,000 S cm-1 at 3,000 K and a high power factor S2σ = 54.5 µW cm-1 K-2. We report measurements characterizing the film's thermoelectric properties up to 3,000 K. The reduced graphene oxide film also exhibits a high broadband radiation absorbance and can act as both a radiative receiver and a thermoelectric generator. The printable, lightweight and flexible film is attractive for system integration and scalable manufacturing.

  11. Few-quintuple Bi₂Te₃ nanofilms as potential thermoelectric materials.

    PubMed

    Zhou, Gang; Wang, Dong

    2015-01-29

    The thermoelectric transport properties of p-type Bi₂Te₃ nanofilms with various quintuple layers (QL) were systematically investigated based on ab initio electronic structure calculations and Boltzmann transport equations. Our results demonstrated that p-type few-quintuple Bi₂Te₃ nanofilms could exhibit high thermoelectric performance. It was found out that the 1QL Bi₂Te₃ nanofilm had the highest ZT value as compared with other nanofilms, which is mainly attributed to the significant enhancement of the density of states near the edge of the valence band resulting from the strong coupling between the top and bottom electronic states and the quantum confinement effect. The dependence of the thermoelectric transport properties on carrier concentration and temperature was also discussed in detail, which can be useful for searching high-efficiency few-quintuple Bi₂Te₃ thermoelectric nanofilms.

  12. Vacancy-induced dislocations within grains for high-performance PbSe thermoelectrics

    DOE PAGES

    Chen, Zhiwei; Ge, Binghui; Li, Wen; ...

    2017-01-04

    To minimize the lattice thermal conductivity in thermoelectrics, strategies typically focus on the scattering of low-frequency phonons by interfaces and high-frequency phonons by point defects. In addition, scattering of mid-frequency phonons by dense dislocations, localized at the grain boundaries, has been shown to reduce the lattice thermal conductivity and improve the thermoelectric performance. Here we propose a vacancy engineering strategy to create dense dislocations in the grains. In Pb 1$-$xSb 2x/3Se solid solutions, cation vacancies are intentionally introduced, where after thermal annealing the vacancies can annihilate through a number of mechanisms creating the desired dislocations homogeneously distributed within the grains.more » This leads to a lattice thermal conductivity as low as 0.4Wm -1 K -1 and a high thermoelectric figure of merit, which can be explained by a dislocation scattering model. As a result, the vacancy engineering strategy used here should be equally applicable for solid solution thermoelectrics and provides a strategy for improving zT.« less

  13. Computationally guided discovery of thermoelectric materials

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Gorai, Prashun; Stevanović, Vladan; Toberer, Eric S.

    The potential for advances in thermoelectric materials, and thus solid-state refrigeration and power generation, is immense. Progress so far has been limited by both the breadth and diversity of the chemical space and the serial nature of experimental work. In this Review, we discuss how recent computational advances are revolutionizing our ability to predict electron and phonon transport and scattering, as well as materials dopability, and we examine efficient approaches to calculating critical transport properties across large chemical spaces. When coupled with experimental feedback, these high-throughput approaches can stimulate the discovery of new classes of thermoelectric materials. Within smaller materialsmore » subsets, computations can guide the optimal chemical and structural tailoring to enhance materials performance and provide insight into the underlying transport physics. Beyond perfect materials, computations can be used for the rational design of structural and chemical modifications (such as defects, interfaces, dopants and alloys) to provide additional control on transport properties to optimize performance. Through computational predictions for both materials searches and design, a new paradigm in thermoelectric materials discovery is emerging.« less

  14. Computationally guided discovery of thermoelectric materials

    DOE PAGES

    Gorai, Prashun; Stevanović, Vladan; Toberer, Eric S.

    2017-08-22

    The potential for advances in thermoelectric materials, and thus solid-state refrigeration and power generation, is immense. Progress so far has been limited by both the breadth and diversity of the chemical space and the serial nature of experimental work. In this Review, we discuss how recent computational advances are revolutionizing our ability to predict electron and phonon transport and scattering, as well as materials dopability, and we examine efficient approaches to calculating critical transport properties across large chemical spaces. When coupled with experimental feedback, these high-throughput approaches can stimulate the discovery of new classes of thermoelectric materials. Within smaller materialsmore » subsets, computations can guide the optimal chemical and structural tailoring to enhance materials performance and provide insight into the underlying transport physics. Beyond perfect materials, computations can be used for the rational design of structural and chemical modifications (such as defects, interfaces, dopants and alloys) to provide additional control on transport properties to optimize performance. Through computational predictions for both materials searches and design, a new paradigm in thermoelectric materials discovery is emerging.« less

  15. Structurally-driven Enhancement of Thermoelectric Properties within Poly(3,4-ethylenedioxythiophene) thin Films

    PubMed Central

    Petsagkourakis, Ioannis; Pavlopoulou, Eleni; Portale, Giuseppe; Kuropatwa, Bryan A.; Dilhaire, Stefan; Fleury, Guillaume; Hadziioannou, Georges

    2016-01-01

    Due to the rising need for clean energy, thermoelectricity has raised as a potential alternative to reduce dependence on fossil fuels. Specifically, thermoelectric devices based on polymers could offer an efficient path for near-room temperature energy harvesters. Thus, control over thermoelectric properties of conducting polymers is crucial and, herein, the structural, electrical and thermoelectric properties of poly(3,4-ethylenedioxythiophene) (PEDOT) thin films doped with p-toluenesulfonate (Tos) molecules were investigated with regards to thin film processing. PEDOT:Tos thin films were prepared by in-situ polymerization of (3,4-ethylenedioxythiophene) monomers in presence of iron(III) p-toluenesulfonate with different co-solvents in order to tune the film structure. While the Seebeck coefficient remained constant, a large improvement in the electrical conductivity was observed for thin films processed with high boiling point additives. The increase of electrical conductivity was found to be solely in-plane mobility-driven. Probing the thin film structure by Grazing Incidence Wide Angle X-ray Scattering has shown that this behavior is dictated by the structural properties of the PEDOT:Tos films; specifically by the thin film crystallinity combined to the preferential edge-on orientation of the PEDOT crystallites. Consequentially enhancement of the power factor from 25 to 78.5 μW/mK2 has been readily obtained for PEDOT:Tos thin films following this methodology. PMID:27470637

  16. Structurally-driven Enhancement of Thermoelectric Properties within Poly(3,4-ethylenedioxythiophene) thin Films.

    PubMed

    Petsagkourakis, Ioannis; Pavlopoulou, Eleni; Portale, Giuseppe; Kuropatwa, Bryan A; Dilhaire, Stefan; Fleury, Guillaume; Hadziioannou, Georges

    2016-07-29

    Due to the rising need for clean energy, thermoelectricity has raised as a potential alternative to reduce dependence on fossil fuels. Specifically, thermoelectric devices based on polymers could offer an efficient path for near-room temperature energy harvesters. Thus, control over thermoelectric properties of conducting polymers is crucial and, herein, the structural, electrical and thermoelectric properties of poly(3,4-ethylenedioxythiophene) (PEDOT) thin films doped with p-toluenesulfonate (Tos) molecules were investigated with regards to thin film processing. Tos thin films were prepared by in-situ polymerization of (3,4-ethylenedioxythiophene) monomers in presence of iron(III) p-toluenesulfonate with different co-solvents in order to tune the film structure. While the Seebeck coefficient remained constant, a large improvement in the electrical conductivity was observed for thin films processed with high boiling point additives. The increase of electrical conductivity was found to be solely in-plane mobility-driven. Probing the thin film structure by Grazing Incidence Wide Angle X-ray Scattering has shown that this behavior is dictated by the structural properties of the Tos films; specifically by the thin film crystallinity combined to the preferential edge-on orientation of the PEDOT crystallites. Consequentially enhancement of the power factor from 25 to 78.5 μW/mK(2) has been readily obtained for Tos thin films following this methodology.

  17. Enhanced thermoelectric transport in modulation-doped GaN/AlGaN core/shell nanowires.

    PubMed

    Song, Erdong; Li, Qiming; Swartzentruber, Brian; Pan, Wei; Wang, George T; Martinez, Julio A

    2016-01-08

    The thermoelectric properties of unintentionally n-doped core GaN/AlGaN core/shell N-face nanowires are reported. We found that the temperature dependence of the electrical conductivity is consistent with thermally activated carriers with two distinctive donor energies. The Seebeck coefficient of GaN/AlGaN nanowires is more than twice as large as that for the GaN nanowires alone. However, an outer layer of GaN deposited onto the GaN/AlGaN core/shell nanowires decreases the Seebeck coefficient at room temperature, while the temperature dependence of the electrical conductivity remains the same. We attribute these observations to the formation of an electron gas channel within the heavily-doped GaN core of the GaN/AlGaN nanowires. The room-temperature thermoelectric power factor for the GaN/AlGaN nanowires can be four times higher than the GaN nanowires. Selective doping in bandgap engineered core/shell nanowires is proposed for enhancing the thermoelectric power.

  18. Thin-film thermoelectric devices with high room-temperature figures of merit.

    PubMed

    Venkatasubramanian, R; Siivola, E; Colpitts, T; O'Quinn, B

    2001-10-11

    Thermoelectric materials are of interest for applications as heat pumps and power generators. The performance of thermoelectric devices is quantified by a figure of merit, ZT, where Z is a measure of a material's thermoelectric properties and T is the absolute temperature. A material with a figure of merit of around unity was first reported over four decades ago, but since then-despite investigation of various approaches-there has been only modest progress in finding materials with enhanced ZT values at room temperature. Here we report thin-film thermoelectric materials that demonstrate a significant enhancement in ZT at 300 K, compared to state-of-the-art bulk Bi2Te3 alloys. This amounts to a maximum observed factor of approximately 2.4 for our p-type Bi2Te3/Sb2Te3 superlattice devices. The enhancement is achieved by controlling the transport of phonons and electrons in the superlattices. Preliminary devices exhibit significant cooling (32 K at around room temperature) and the potential to pump a heat flux of up to 700 W cm-2; the localized cooling and heating occurs some 23,000 times faster than in bulk devices. We anticipate that the combination of performance, power density and speed achieved in these materials will lead to diverse technological applications: for example, in thermochemistry-on-a-chip, DNA microarrays, fibre-optic switches and microelectrothermal systems.

  19. High-performance shape-engineerable thermoelectric painting

    PubMed Central

    Park, Sung Hoon; Jo, Seungki; Kwon, Beomjin; Kim, Fredrick; Ban, Hyeong Woo; Lee, Ji Eun; Gu, Da Hwi; Lee, Se Hwa; Hwang, Younghun; Kim, Jin-Sang; Hyun, Dow-Bin; Lee, Sukbin; Choi, Kyoung Jin; Jo, Wook; Son, Jae Sung

    2016-01-01

    Output power of thermoelectric generators depends on device engineering minimizing heat loss as well as inherent material properties. However, the device engineering has been largely neglected due to the limited flat or angular shape of devices. Considering that the surface of most heat sources where these planar devices are attached is curved, a considerable amount of heat loss is inevitable. To address this issue, here, we present the shape-engineerable thermoelectric painting, geometrically compatible to surfaces of any shape. We prepared Bi2Te3-based inorganic paints using the molecular Sb2Te3 chalcogenidometalate as a sintering aid for thermoelectric particles, with ZT values of 0.67 for n-type and 1.21 for p-type painted materials that compete the bulk values. Devices directly brush-painted onto curved surfaces produced the high output power of 4.0 mW cm−2. This approach paves the way to designing materials and devices that can be easily transferred to other applications. PMID:27834369

  20. Band Structures and Transport Properties of High-Performance Half-Heusler Thermoelectric Materials by First Principles.

    PubMed

    Fang, Teng; Zhao, Xinbing; Zhu, Tiejun

    2018-05-19

    Half-Heusler (HH) compounds, with a valence electron count of 8 or 18, have gained popularity as promising high-temperature thermoelectric (TE) materials due to their excellent electrical properties, robust mechanical capabilities, and good high-temperature thermal stability. With the help of first-principles calculations, great progress has been made in half-Heusler thermoelectric materials. In this review, we summarize some representative theoretical work on band structures and transport properties of HH compounds. We introduce how basic band-structure calculations are used to investigate the atomic disorder in n-type M NiSb ( M = Ti, Zr, Hf) compounds and guide the band engineering to enhance TE performance in p-type Fe R Sb ( R = V, Nb) based systems. The calculations on electrical transport properties, especially the scattering time, and lattice thermal conductivities are also demonstrated. The outlook for future research directions of first-principles calculations on HH TE materials is also discussed.

  1. Band Structures and Transport Properties of High-Performance Half-Heusler Thermoelectric Materials by First Principles

    PubMed Central

    Fang, Teng; Zhao, Xinbing

    2018-01-01

    Half-Heusler (HH) compounds, with a valence electron count of 8 or 18, have gained popularity as promising high-temperature thermoelectric (TE) materials due to their excellent electrical properties, robust mechanical capabilities, and good high-temperature thermal stability. With the help of first-principles calculations, great progress has been made in half-Heusler thermoelectric materials. In this review, we summarize some representative theoretical work on band structures and transport properties of HH compounds. We introduce how basic band-structure calculations are used to investigate the atomic disorder in n-type MNiSb (M = Ti, Zr, Hf) compounds and guide the band engineering to enhance TE performance in p-type FeRSb (R = V, Nb) based systems. The calculations on electrical transport properties, especially the scattering time, and lattice thermal conductivities are also demonstrated. The outlook for future research directions of first-principles calculations on HH TE materials is also discussed. PMID:29783759

  2. Extraordinary Thermoelectric Performance Realized in Hierarchically Structured AgSbSe2 with Ultralow Thermal Conductivity.

    PubMed

    Gao, Weihong; Wang, Zhenyou; Huang, Jin; Liu, Zihang

    2018-05-24

    Thermoelectric conversion from low-grade heat to electricity is regarded as the highly reliable and environmentally friendly technology in energy-harvesting area. However, how to develop efficient thermoelectric materials using a simple fabrication method is still a critical challenge in thermoelectric community. Here, we first fabricate the high thermoelectric performance of Ca-doped AgSbSe 2 with a hierarchical microstructure using a facile approach, namely, mechanical alloying (for only 30 min) and a quick hot-pressing method. The hierarchical microstructure, including point defects (atomic scale), dislocations, and nanoprecipitates (nanoscale) as well as grain boundaries (microscale), strongly scatters phonons with comparable sizes without deterioration of carrier mobility. Because of the higher carrier concentration of nanostructured AgSbSe 2 than that of coarse-grain AgSbSe 2 , power factor can also be improved slightly after nanostructuring. Ca doping further optimizes the carrier concentration and creates the point-defect scattering of phonons, leading to the ultralow lattice thermal conductivity ∼0.27 W m -1 K -1 at 673 K and thus largely improving the peak ZT up to 1.2. The high thermoelectric performance in combination with a facile fabrication method highlights AgSbSe 2 -based materials as robust thermoelectric candidates for energy harvesting.

  3. Intrinsically modified thermoelectric performance of alkaline-earth isovalently substituted [Bi2AE2O4][CoO2]y single crystals

    NASA Astrophysics Data System (ADS)

    Sun, N.; Dong, S. T.; Zhang, B. B.; Chen, Y. B.; Zhou, J.; Zhang, S. T.; Gu, Z. B.; Yao, S. H.; Chen, Y. F.

    2013-07-01

    Alkaline-earth elements isovalently substituted into a [Bi2AE2O4][CoO2]y (AE2 = Ca2, Sr2, and CaSr) single crystal with a layered structure were grown by the optical floating zone method. Structural characterization by X-ray diffraction and electron microscopy showed that the layers were oriented perpendicular to the c-axis, as well as the growth of direction was parallel to the ab-plane. The thermoelectric properties, including the Seebeck effect, electrical conductivity and thermal conductivity were investigated. The results of the thermoelectric measurements showed that the full substitution of Ca for Sr in [Bi2Sr2-xCaxO4][CoO2]y has the best overall thermoelectric performance. Compared with the other two cases studied, the full Ca substituted crystal [Bi2Ca2O4][CoO2]y exhibits both reduced resistivity and thermal conductivity, but not a reduced Seebeck coefficient. The enhanced thermoelectric property in [Bi2Ca2O4][CoO2]y is mainly due to lower structural symmetry, which is confirmed by electron microscopy characterization. This work demonstrates that even isovalently substitution can play a crucial role in the thermoelectric effect of layered cobalt oxides.

  4. Key to enhance thermoelectric performance by controlling crystal size of strontium titanate

    NASA Astrophysics Data System (ADS)

    Wang, Jun; Ye, Xinxin; Yaer, Xinba; Wu, Yin; Zhang, Boyu; Miao, Lei

    2015-09-01

    One-step molten salt synthesis process was introduced to fabricate nano to micrometer sized SrTiO3 powders in which effects of synthesis temperature, oxide-to-flux ratios and raw materials on the generation of SrTiO3 powders were examined. 100 nm or above sized pure SrTiO3 particles were obtained at relatively lower temperature of 900∘C. Micro-sized rhombohedral crystals with a maximum size of approximately 12 μm were obtained from SrCO3 or Sr(NO3)2 strontium source with 1:1 O/S ratio. Controlled crystal size and morphology of Nb-doped SrTiO3 particles are prepared by using this method to confirm the performance of thermoelectric properties. The Seebeck coefficient obtained is significantly high when compared with the reported data, and the high ratio of nano particles in the sample has a positive effect on the increase of Seebeck coefficient too, which is likely due to the energy filtering effect at large numbers of grain boundaries resulting from largely distributed structure.

  5. Bottom-up design of de novo thermoelectric hybrid materials using chalcogenide resurfacing

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Sahu, Ayaskanta; Russ, Boris; Su, Norman C.

    Hybrid organic/inorganic thermoelectric materials based on conducting polymers and inorganic nanostructures have been demonstrated to combine both the inherently low thermal conductivity of the polymer and the superior charge transport properties (high power factors) of the inorganic component. While their performance today still lags behind that of conventional inorganic thermoelectric materials, solution-processable hybrids have made rapid progress and also offer unique advantages not available to conventional rigid inorganic thermoelectrics, namely: (1) low cost fabrication on rigid and flexible substrates, as well as (2) engineering complex conformal geometries for energy harvesting/cooling. While the number of reports of new classes of viablemore » hybrid thermoelectric materials is growing, no group has reported a general approach for bottom-up design of both p- and n-type materials from one common base. Thus, unfortunately, the literature comprises mostly of disconnected discoveries, which limits development and calls for a first-principles approach for property manipulation analogous to doping in traditional semiconductor thermoelectrics. Here, molecular engineering at the organic/inorganic interface and simple processing techniques are combined to demonstrate a modular approach enabling de novo design of complex hybrid thermoelectric systems. Here, we chemically modify the surfaces of inorganic nanostructures and graft conductive polymers to yield robust solution processable p- and n-type inorganic/organic hybrid nanostructures. Our new modular approach not only offers researchers new tools to perform true bottom-up design of thermoelectric hybrids, but also strong performance advantages as well due to the quality of the designed interfaces. For example, we obtain enhanced power factors in existing (by up to 500% in Te/PEDOT:PSS) and novel (Bi 2S 3/PEDOT:PSS) p-type systems, and also generate water-processable and air-stable high performing n-type hybrid

  6. Bottom-up design of de novo thermoelectric hybrid materials using chalcogenide resurfacing

    DOE PAGES

    Sahu, Ayaskanta; Russ, Boris; Su, Norman C.; ...

    2017-01-01

    Hybrid organic/inorganic thermoelectric materials based on conducting polymers and inorganic nanostructures have been demonstrated to combine both the inherently low thermal conductivity of the polymer and the superior charge transport properties (high power factors) of the inorganic component. While their performance today still lags behind that of conventional inorganic thermoelectric materials, solution-processable hybrids have made rapid progress and also offer unique advantages not available to conventional rigid inorganic thermoelectrics, namely: (1) low cost fabrication on rigid and flexible substrates, as well as (2) engineering complex conformal geometries for energy harvesting/cooling. While the number of reports of new classes of viablemore » hybrid thermoelectric materials is growing, no group has reported a general approach for bottom-up design of both p- and n-type materials from one common base. Thus, unfortunately, the literature comprises mostly of disconnected discoveries, which limits development and calls for a first-principles approach for property manipulation analogous to doping in traditional semiconductor thermoelectrics. Here, molecular engineering at the organic/inorganic interface and simple processing techniques are combined to demonstrate a modular approach enabling de novo design of complex hybrid thermoelectric systems. Here, we chemically modify the surfaces of inorganic nanostructures and graft conductive polymers to yield robust solution processable p- and n-type inorganic/organic hybrid nanostructures. Our new modular approach not only offers researchers new tools to perform true bottom-up design of thermoelectric hybrids, but also strong performance advantages as well due to the quality of the designed interfaces. For example, we obtain enhanced power factors in existing (by up to 500% in Te/PEDOT:PSS) and novel (Bi 2S 3/PEDOT:PSS) p-type systems, and also generate water-processable and air-stable high performing n-type hybrid

  7. Low Sound Velocity Contributing to the High Thermoelectric Performance of Ag8SnSe6

    PubMed Central

    Li, Wen; Lin, Siqi; Ge, Binghui; Yang, Jiong; Zhang, Wenqing

    2016-01-01

    Conventional strategies for advancing thermoelectrics by minimizing the lattice thermal conductivity focus on phonon scattering for a short mean free path. Here, a design of slow phonon propagation as an effective approach for high‐performance thermoelectrics is shown. Taking Ag8SnSe6 as an example, which shows one of the lowest sound velocities among known thermoelectric semiconductors, the lattice thermal conductivity is found to be as low as 0.2 W m−1 K−1 in the entire temperature range. As a result, a peak thermoelectric figure of merit zT > 1.2 and an average zT as high as ≈0.8 are achieved in Nb‐doped materials, without relying on a high thermoelectric power factor. This work demonstrates not only a guiding principle of low sound velocity for minimal lattice thermal conductivity and therefore high zT, but also argyrodite compounds as promising thermoelectric materials with weak chemical bonds and heavy constituent elements. PMID:27980995

  8. Low Sound Velocity Contributing to the High Thermoelectric Performance of Ag8SnSe6.

    PubMed

    Li, Wen; Lin, Siqi; Ge, Binghui; Yang, Jiong; Zhang, Wenqing; Pei, Yanzhong

    2016-11-01

    Conventional strategies for advancing thermoelectrics by minimizing the lattice thermal conductivity focus on phonon scattering for a short mean free path. Here, a design of slow phonon propagation as an effective approach for high-performance thermoelectrics is shown. Taking Ag 8 SnSe 6 as an example, which shows one of the lowest sound velocities among known thermoelectric semiconductors, the lattice thermal conductivity is found to be as low as 0.2 W m -1 K -1 in the entire temperature range. As a result, a peak thermoelectric figure of merit zT > 1.2 and an average zT as high as ≈0.8 are achieved in Nb-doped materials, without relying on a high thermoelectric power factor. This work demonstrates not only a guiding principle of low sound velocity for minimal lattice thermal conductivity and therefore high zT , but also argyrodite compounds as promising thermoelectric materials with weak chemical bonds and heavy constituent elements.

  9. Enhancing thermoelectric properties through a three-terminal benzene molecule

    NASA Astrophysics Data System (ADS)

    Sartipi, Z.; Vahedi, J.

    2018-05-01

    The thermoelectric transport through a benzene molecule with three metallic terminals is discussed. Using general local and non-local transport coefficients, we investigated different conductance and thermopower coefficients within the linear response regime. Based on the Onsager coefficients which depend on the number of terminal efficiencies, efficiency at maximum power is also studied. In the three-terminal setup with tuning temperature differences, a great enhancement of the figure of merit is observed. Results also show that the third terminal model can be useful in improving the efficiency at maximum output power compared to the two-terminal model.

  10. Significant Enhancement in the Thermoelectric Properties of PEDOT:PSS Films through a Treatment with Organic Solutions of Inorganic Salts.

    PubMed

    Fan, Zeng; Du, Donghe; Yu, Zhimeng; Li, Pengcheng; Xia, Yijie; Ouyang, Jianyong

    2016-09-07

    Conducting polymers have promising thermoelectric application because they have many advantages including abundant elements, mechanical flexibility, and nontoxicity. The thermoelectric properties of conducting polymers strongly depend on their chemical structure and microstructure. Here, we report a novel and facile method to significantly enhance the thermoelectric properties of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) ( PSS) films through a treatment with organic solutions of inorganic salts. N,N-Dimethylformamide (DMF) and a common inorganic salt like zinc chloride (ZnCl2) are used as the solvent and solute of the solutions, respectively. The treatments can significantly increase both the Seebeck coefficient and electrical conductivity of the PSS films. The thermoelectric properties of the PSS films are sensitive to the experimental conditions, such as the salt concentration, treatment temperature, and the cation of the salts. After treatment at the optimal experimental conditions, the PSS films can exhibit a Seebeck coefficient of 26.1 μV/K and an electrical conductivity of over 1400 S/cm at room temperature. The corresponding power factor is 98.2 μW/(m·K(2)). The mechanism for the enhancement in the thermoelectric properties is attributed to the segregation of some PSSH chains from PSS and the conformation change of PEDOT chains as a result of the synergetic effects of inorganic salts and DMF.

  11. Effect of C and N Addition on Thermoelectric Properties of TiNiSn Half-Heusler Compounds.

    PubMed

    Dow, Hwan Soo; Kim, Woo Sik; Shin, Weon Ho

    2018-02-08

    We investigated the thermoelectric properties of the ternary half-Heusler compound, TiNiSn, when introducing C and N. The addition of C or N to TiNiSn leads to an enhanced power factor and a decreasing lattice thermal conductivity by point defect phonon scattering. The thermoelectric performances of TiNiSn alloys are significantly improved by adding 1 at. % TiN, TiC, and figure of merit ( ZT ) values of 0.43 and 0.34, respectively, can be obtained at 723 K. This increase in thermoelectric performance is very helpful in the commercialization of thermoelectric power generation in the mid-temperature range.

  12. Synthetic thermoelectric materials comprising phononic crystals

    DOEpatents

    El-Kady, Ihab F; Olsson, Roy H; Hopkins, Patrick; Reinke, Charles; Kim, Bongsang

    2013-08-13

    Synthetic thermoelectric materials comprising phononic crystals can simultaneously have a large Seebeck coefficient, high electrical conductivity, and low thermal conductivity. Such synthetic thermoelectric materials can enable improved thermoelectric devices, such as thermoelectric generators and coolers, with improved performance. Such synthetic thermoelectric materials and devices can be fabricated using techniques that are compatible with standard microelectronics.

  13. Performance of a Half-Heusler Thermoelectric Generator for Automotive Application

    DOE PAGES

    Szybist, James; Davis, Steven; Thomas, John; ...

    2018-04-03

    Thermoelectric generators (TEGs) have been researched and developed for harvesting energy from otherwise wasted heat. For automotive applications this will most likely involve using internal combustion engine exhaust as the heat source, with the TEG positioned after the catalyst system. Applications to exhaust gas recirculation systems and compressed air coolers have also been suggested. A thermoelectric generator based on half-Heusler thermoelectric materials was developed, engineered, and fabricated, targeting a gasoline passenger sedan application. This generator was installed on a gasoline engine exhaust system in a dynamometer cell, and positioned immediately downstream of the closecoupled three-way catalyst. The generator was characterizedmore » using a matrix of steady-state conditions representing the important portions of the engine map. Detailed performance results are presented. Measurements indicate the generator can produces over 300 W of power with 900 °C exhaust at relatively high flow rates, but less than 50 W when the exhaust is 600 °C and at lower flow rates. The latter condition is typical of standard test cycles and most driving scenarios.« less

  14. Performance of a Half-Heusler Thermoelectric Generator for Automotive Application

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Szybist, James; Davis, Steven; Thomas, John

    Thermoelectric generators (TEGs) have been researched and developed for harvesting energy from otherwise wasted heat. For automotive applications this will most likely involve using internal combustion engine exhaust as the heat source, with the TEG positioned after the catalyst system. Applications to exhaust gas recirculation systems and compressed air coolers have also been suggested. A thermoelectric generator based on half-Heusler thermoelectric materials was developed, engineered, and fabricated, targeting a gasoline passenger sedan application. This generator was installed on a gasoline engine exhaust system in a dynamometer cell, and positioned immediately downstream of the closecoupled three-way catalyst. The generator was characterizedmore » using a matrix of steady-state conditions representing the important portions of the engine map. Detailed performance results are presented. Measurements indicate the generator can produces over 300 W of power with 900 °C exhaust at relatively high flow rates, but less than 50 W when the exhaust is 600 °C and at lower flow rates. The latter condition is typical of standard test cycles and most driving scenarios.« less

  15. Performance comparison investigation on solar photovoltaic-thermoelectric generation and solar photovoltaic-thermoelectric cooling hybrid systems under different conditions

    NASA Astrophysics Data System (ADS)

    Wu, Shuang-Ying; Zhang, Yi-Chen; Xiao, Lan; Shen, Zu-Guo

    2018-07-01

    The performance of solar photovoltaic-thermoelectric generation hybrid system (PV-TGS) and solar photovoltaic-thermoelectric cooling hybrid system (PV-TCS) under different conditions were theoretically analysed and compared. To test the practicality of these two hybrid systems, the performance of stand-alone PV system was also studied. The results show that PV-TGS and PV-TCS in most cases will result in the system with a better performance than stand-alone PV system. The advantage of PV-TGS is emphasised in total output power and conversion efficiency which is even poorer in PV-TCS than that in stand-alone PV system at the ambient wind speed uw being below 3 m/s. However, PV-TCS has obvious advantage on lowering the temperature of PV cell. There is an obvious increase in tendency on the performance of PV-TGS and PV-TCS when the cooling capacity of two hybrid systems varies from around 0.06 to 0.3 W/K. And it is also proved that not just a-Si in PV-TGS can produce a better performance than the stand-alone PV system alone at most cases.

  16. Solution-Processed Cu2Se Nanocrystal Films with Bulk-Like Thermoelectric Performance.

    PubMed

    Forster, Jason D; Lynch, Jared J; Coates, Nelson E; Liu, Jun; Jang, Hyejin; Zaia, Edmond; Gordon, Madeleine P; Szybowski, Maxime; Sahu, Ayaskanta; Cahill, David G; Urban, Jeffrey J

    2017-06-05

    Thermoelectric power generation can play a key role in a sustainable energy future by converting waste heat from power plants and other industrial processes into usable electrical power. Current thermoelectric devices, however, require energy intensive manufacturing processes such as alloying and spark plasma sintering. Here, we describe the fabrication of a p-type thermoelectric material, copper selenide (Cu 2 Se), utilizing solution-processing and thermal annealing to produce a thin film that achieves a figure of merit, ZT, which is as high as its traditionally processed counterpart, a value of 0.14 at room temperature. This is the first report of a fully solution-processed nanomaterial achieving performance equivalent to its bulk form and represents a general strategy to reduce the energy required to manufacture advanced energy conversion and harvesting materials.

  17. High-performance thermoelectric nanocomposites from nanocrystal building blocks

    PubMed Central

    Ibáñez, Maria; Luo, Zhishan; Genç, Aziz; Piveteau, Laura; Ortega, Silvia; Cadavid, Doris; Dobrozhan, Oleksandr; Liu, Yu; Nachtegaal, Maarten; Zebarjadi, Mona; Arbiol, Jordi; Kovalenko, Maksym V.; Cabot, Andreu

    2016-01-01

    The efficient conversion between thermal and electrical energy by means of durable, silent and scalable solid-state thermoelectric devices has been a long standing goal. While nanocrystalline materials have already led to substantially higher thermoelectric efficiencies, further improvements are expected to arise from precise chemical engineering of nanoscale building blocks and interfaces. Here we present a simple and versatile bottom–up strategy based on the assembly of colloidal nanocrystals to produce consolidated yet nanostructured thermoelectric materials. In the case study on the PbS–Ag system, Ag nanodomains not only contribute to block phonon propagation, but also provide electrons to the PbS host semiconductor and reduce the PbS intergrain energy barriers for charge transport. Thus, PbS–Ag nanocomposites exhibit reduced thermal conductivities and higher charge carrier concentrations and mobilities than PbS nanomaterial. Such improvements of the material transport properties provide thermoelectric figures of merit up to 1.7 at 850 K. PMID:26948987

  18. High-performance thermoelectric nanocomposites from nanocrystal building blocks.

    PubMed

    Ibáñez, Maria; Luo, Zhishan; Genç, Aziz; Piveteau, Laura; Ortega, Silvia; Cadavid, Doris; Dobrozhan, Oleksandr; Liu, Yu; Nachtegaal, Maarten; Zebarjadi, Mona; Arbiol, Jordi; Kovalenko, Maksym V; Cabot, Andreu

    2016-03-07

    The efficient conversion between thermal and electrical energy by means of durable, silent and scalable solid-state thermoelectric devices has been a long standing goal. While nanocrystalline materials have already led to substantially higher thermoelectric efficiencies, further improvements are expected to arise from precise chemical engineering of nanoscale building blocks and interfaces. Here we present a simple and versatile bottom-up strategy based on the assembly of colloidal nanocrystals to produce consolidated yet nanostructured thermoelectric materials. In the case study on the PbS-Ag system, Ag nanodomains not only contribute to block phonon propagation, but also provide electrons to the PbS host semiconductor and reduce the PbS intergrain energy barriers for charge transport. Thus, PbS-Ag nanocomposites exhibit reduced thermal conductivities and higher charge carrier concentrations and mobilities than PbS nanomaterial. Such improvements of the material transport properties provide thermoelectric figures of merit up to 1.7 at 850 K.

  19. Enhanced thermoelectric transport in modulation-doped GaN/AlGaN core/shell nanowires

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Song, Erdong; Li, Qiming; Swartzentruber, Brian

    2015-11-25

    The thermoelectric properties of unintentionally n-doped core GaN/AlGaN core/shell N-face nanowires are reported. We found that the temperature dependence of the electrical conductivity is consistent with thermally activated carriers with two distinctive donor energies. The Seebeck coefficient of GaN/AlGaN nanowires is more than twice as large as that for the GaN nanowires alone. However, an outer layer of GaN deposited onto the GaN/AlGaN core/shell nanowires decreases the Seebeck coefficient at room temperature, while the temperature dependence of the electrical conductivity remains the same. We attribute these observations to the formation of an electron gas channel within the heavily-doped GaN coremore » of the GaN/AlGaN nanowires. The room-temperature thermoelectric power factor for the GaN/AlGaN nanowires can be four times higher than the GaN nanowires. As a result, selective doping in bandgap engineered core/shell nanowires is proposed for enhancing the thermoelectric power.« less

  20. Thermoelectric silicides: A review

    NASA Astrophysics Data System (ADS)

    Nozariasbmarz, Amin; Agarwal, Aditi; Coutant, Zachary A.; Hall, Michael J.; Liu, Jie; Liu, Runze; Malhotra, Abhishek; Norouzzadeh, Payam; Öztürk, Mehmet C.; Ramesh, Viswanath P.; Sargolzaeiaval, Yasaman; Suarez, Francisco; Vashaee, Daryoosh

    2017-05-01

    Traditional research on thermoelectric materials focused on improving the figure-of-merit z T to enhance the energy conversion efficiency. With further growth and commercialization of thermoelectric technology beyond niche applications, other factors such as materials availability, toxicity, cost, recyclability, thermal stability, chemical and mechanical properties, and ease of fabrication become important for making viable technologies. Several silicide alloys were identified that have the potential to fulfill these requirements. These materials are of interest due to their abundancy in earth’s crust (e.g., silicon), non-toxicity, and good physical and chemical properties. In this paper, an overview of the silicide thermoelectrics from traditional alloys to advanced material structures is presented. In addition, some of the most effective approaches as well as fundamental physical concepts for designing and developing efficient thermoelectric materials are presented and future perspectives are discussed.

  1. Enhanced thermoelectric response in the fractional quantum Hall effect

    NASA Astrophysics Data System (ADS)

    Roura-Bas, Pablo; Arrachea, Liliana; Fradkin, Eduardo

    2018-02-01

    We study the linear thermoelectric response of a quantum dot embedded in a constriction of a quantum Hall bar with fractional filling factors ν =1 /m within Laughlin series. We calculate the figure of merit Z T for the maximum efficiency at a fixed temperature difference. We find a significant enhancement of this quantity in the fractional filling in relation to the integer-filling case, which is a direct consequence of the fractionalization of the electron in the fractional quantum Hall state. We present simple theoretical expressions for the Onsager coefficients at low temperatures, which explicitly show that Z T and the Seebeck coefficient increase with m .

  2. Thickness-controlled electronic structure and thermoelectric performance of ultrathin SnS2 nanosheets.

    PubMed

    Li, Jun; Shen, Jinni; Ma, Zuju; Wu, Kechen

    2017-08-21

    The thermoelectric conversion efficiency of a material relies on a dimensionless parameter (ZT = S 2 σT/κ). It is a great challenge in enhancing the ZT value basically due to that the related transport factors of most of the bulk materials are inter-conditioned to each other, making it very difficult to simultaneously optimize these parameters. In this report, the negative correlation between power factor and thermal conductivity of nano-scaled SnS 2 multilayers is predicted by high-level first-principle computations combined with Boltzmann transport theory. By diminishing the thickness of SnS 2 nanosheet to about 3 L, the S and σ along a direction simultaneously increase whereas κ decreases, achieving a high ZT value of 1.87 at 800 K. The microscopic mechanisms for this unusual negative correlation in nano-scaled two dimensional (2D) material are elucidated and attributed to the quantum confinement effect. The results may open a way to explore the high ZT thermoelectric nano-devices for the practical thermoelectric applications.

  3. Solution-Processed Cu 2Se Nanocrystal Films with Bulk-Like Thermoelectric Performance

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Forster, Jason D.; Lynch, Jared J.; Coates, Nelson E.

    Thermoelectric power generation can play a key role in a sustainable energy future by converting waste heat from power plants and other industrial processes into usable electrical power. Current thermoelectric devices, however, require energy intensive manufacturing processes such as alloying and spark plasma sintering. Here, we describe the fabrication of a p-type thermoelectric material, copper selenide (Cu 2 Se), utilizing solution-processing and thermal annealing to produce a thin film that achieves a figure of merit, ZT, which is as high as its traditionally processed counterpart, a value of 0.14 at room temperature. This is the first report of amore » fully solution-processed nanomaterial achieving performance equivalent to its bulk form and represents a general strategy to reduce the energy required to manufacture advanced energy conversion and harvesting materials.« less

  4. Solution-Processed Cu 2Se Nanocrystal Films with Bulk-Like Thermoelectric Performance

    DOE PAGES

    Forster, Jason D.; Lynch, Jared J.; Coates, Nelson E.; ...

    2017-06-05

    Thermoelectric power generation can play a key role in a sustainable energy future by converting waste heat from power plants and other industrial processes into usable electrical power. Current thermoelectric devices, however, require energy intensive manufacturing processes such as alloying and spark plasma sintering. Here, we describe the fabrication of a p-type thermoelectric material, copper selenide (Cu 2 Se), utilizing solution-processing and thermal annealing to produce a thin film that achieves a figure of merit, ZT, which is as high as its traditionally processed counterpart, a value of 0.14 at room temperature. This is the first report of amore » fully solution-processed nanomaterial achieving performance equivalent to its bulk form and represents a general strategy to reduce the energy required to manufacture advanced energy conversion and harvesting materials.« less

  5. A 3D TCAD simulation of a thermoelectric module configured for thermoelectric power generation, cooling and heating

    NASA Astrophysics Data System (ADS)

    Gould, C. A.; Shammas, N. Y. A.; Grainger, S.; Taylor, I.; Simpson, K.

    2012-06-01

    This paper documents the 3D modeling and simulation of a three couple thermoelectric module using the Synopsys Technology Computer Aided Design (TCAD) semiconductor simulation software. Simulation results are presented for thermoelectric power generation, cooling and heating, and successfully demonstrate the basic thermoelectric principles. The 3D TCAD simulation model of a three couple thermoelectric module can be used in the future to evaluate different thermoelectric materials, device structures, and improve the efficiency and performance of thermoelectric modules.

  6. Enhanced performance of dye-sensitized solar cell using Bi2Te3 nanotube/ZnO nanoparticle composite photoanode by the synergistic effect of photovoltaic and thermoelectric conversion

    NASA Astrophysics Data System (ADS)

    Dou, Yuanyao; Wu, Fang; Fang, Liang; Liu, Gaobin; Mao, Caiying; Wan, Kai; Zhou, Miao

    2016-03-01

    Ultralong and highly crystalline rhombohedral Bi2Te3 nanotubes were fabricated by a two-step solution phase reaction. A novel photoanode architecture has been fabricated by embedding 0-2.5 wt.% Bi2Te3 nanotubes into ZnO nanoparticles. The photocurrent density-voltage (J-V) characteristics reveal that the dye sensitized solar cells (DSSCs) with Bi2Te3/ZnO composite photoanode exhibit significantly enhanced photovoltaic performance. Notably, the DSSC incorporating 1.5 wt.% Bi2Te3 in the ZnO photoanode demonstrates an energy conversion efficiency (η) of 4.27%, which is 44.3% higher than that of the bare ZnO photoanode. The electrochemical impedance spectroscopy (EIS) analysis shows that the Bi2Te3 nanotubes can provide a direct pathway for electron transportation, prolong the lifetime of electrons, suppress the charge recombination and improve the electron collection efficiency. The thermoelectric effect analysis indicates that with the increase of irradiation time, Bi2Te3/ZnO composite photoanode could convert both heat and photon energies to electrical energy simultaneously and slow down the decline of η. The calculated electron density (ns) further proves that the increment of short-circuit current density (Jsc) is attributed to Seebeck effect in the composite photoanode. These results suggest that compositing 1D thermoelectric nano-materials in photoanode is a promising route to improve the performance of DSSCs.

  7. AgI alloying in SnTe boosts the thermoelectric performance via simultaneous valence band convergence and carrier concentration optimization

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Banik, Ananya; Biswas, Kanishka, E-mail: kanishka@jncasr.ac.in

    SnTe, a Pb-free analogue of PbTe, was earlier assumed to be a poor thermoelectric material due to excess p-type carrier concentration and large energy separation between light and heavy hole valence bands. Here, we report the enhancement of the thermoelectric performance of p-type SnTe by Ag and I co-doping. AgI (1–6 mol%) alloying in SnTe modulates its electronic structure by increasing the band gap of SnTe, which results in decrease in the energy separation between its light and heavy hole valence bands, thereby giving rise to valence band convergence. Additionally, iodine doping in the Te sublattice of SnTe decreases themore » excess p-type carrier concentration. Due to significant decrease in hole concentration and reduction of the energy separation between light and heavy hole valence bands, significant enhancement in Seebeck coefficient was achieved at the temperature range of 600–900 K for Sn{sub 1−x}Ag{sub x}Te{sub 1−x}I{sub x} samples. A maximum thermoelectric figure of merit, zT, of ~1.05 was achieved at 860 K in high quality crystalline ingot of p-type Sn{sub 0.95}Ag{sub 0.05}Te{sub 0.95}I{sub 0.05}. - Graphical abstract: Significant decrease in hole concentration and reduction of the energy separation between light and heavy hole valence bands resulted in a maximum thermoelectric figure of merit, zT, of ~1.05 at 860 K in high quality crystalline ingot of p-type Sn{sub 0.95}Ag{sub 0.05}Te{sub 0.95}I{sub 0.05}. - Highlights: • AgI alloying in SnTe increases the principle band gap. • Hole concentration reduction and valence band convergence enhances thermopower of SnTe-AgI. • A maximum zT of ~1.05 was achieved at 860 K in p-type Sn{sub 0.95}Ag{sub 0.05}Te{sub 0.95}I{sub 0.05}.« less

  8. Thermoelectric performance of co-doped SnTe with resonant levels

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhou, Min; Han, Yemao; Li, Laifeng, E-mail: laifengli@mail.ipc.ac.cn, E-mail: wangheng83@gmail.com

    2016-07-25

    Some group III elements such as Indium are known to produce the resonant impurity states in IV-VI compounds. The discovery of these impurity states has opened up new ways for engineering the thermoelectric properties of IV-VI compounds. In this work, resonant states in SnTe were studied by co-doping with both resonant (In) and extrinsic (Ag, I) dopants. A characteristic nonlinear relationship was observed between the Hall carrier concentration (n{sub H}) and extrinsic dopant concentration (N{sub I}, N{sub Ag}) in the stabilization region, where a linear increase of dopant concentration does not lead to linear response in the measured n{sub H}.more » Upon substituting extrinsic dopants beyond a certain amount, the n{sub H} changed proportionally with additional dopants (Ag, I) (the doping region). The Seebeck coefficients are enhanced as the resonant impurity is introduced, whereas the use of extrinsic doping only induces minor changes. Modest zT enhancements are observed at lower temperatures, which lead to an increase in the average zT values over a broad range of temperatures (300–773 K). The improved average zT obtained through co-doping indicates the promise of fine carrier density control in maximizing the favorable effect of resonant levels for thermoelectric materials.« less

  9. High-performance thermoelectric mineral Cu12-xNixSb4S13 tetrahedrite

    NASA Astrophysics Data System (ADS)

    Suekuni, Koichiro; Tsuruta, Kojiro; Kunii, Masaru; Nishiate, Hirotaka; Nishibori, Eiji; Maki, Sachiko; Ohta, Michihiro; Yamamoto, Atsushi; Koyano, Mikio

    2013-01-01

    X-ray structural analysis and high-temperature thermoelectric properties measurements are performed on polycrystalline samples of artificial mineral Cu12-xNixSb4S13 tetrahedrite. Analysis of the atomic displacement parameter manifests low-energy vibration of Cu(2) out of CuS3 triangle plane. The vibration results in low lattice thermal conductivity of less than 0.5 W K-1 m-1. By tuning of the Ni composition x and decrease of electronic thermal conductivity, dimensionless thermoelectric figure of merit for x = 1.5 achieves 0.7 at 665 K, which is a considerably high value among p-type Pb-free sulfides. Because the tetrahedrite is an environmentally friendly material, it constitutes a good thermoelectric material for use in support of a sustainable society.

  10. A gigantically increased ratio of electrical to thermal conductivity and synergistically enhanced thermoelectric properties in interface-controlled TiO2-RGO nanocomposites.

    PubMed

    Nam, Woo Hyun; Lim, Young Soo; Kim, Woochul; Seo, Hyeon Kook; Dae, Kyun Seong; Lee, Soonil; Seo, Won-Seon; Lee, Jeong Yong

    2017-06-14

    We report synergistically enhanced thermoelectric properties through the independently controlled charge and thermal transport properties in a TiO 2 -reduced graphene oxide (RGO) nanocomposite. By the consolidation of TiO 2 -RGO hybrid powder using spark plasma sintering, we prepared an interface-controlled TiO 2 -RGO nanocomposite where its grain boundaries are covered with the RGO network. Both the enhancement in electrical conductivity and the reduction in thermal conductivity were simultaneously achieved thanks to the beneficial effects of the RGO network, and detailed mechanisms are discussed. This led to the gigantic increase in the ratio of electrical to thermal conductivity by six orders of magnitude and also the synergistic enhancement in the thermoelectric figure of merit by two orders. Our results present a strategy for the realization of 'phonon-glass electron-crystals' through interface control using graphene in graphene hybrid thermoelectric materials.

  11. Enhancement of the thermoelectric figure of merit in a ferromagnet-quantum dot-superconductor device due to intradot spin-flip scattering and ac field

    NASA Astrophysics Data System (ADS)

    Xu, Wei-Ping; Zhang, Yu-Ying; Li, Zhi-Jian; Nie, Yi-Hang

    2017-08-01

    We investigate the thermoelectric properties of a ferromagnet-quantum dot-superconductor hybrid system with the intradot spin-flip scattering and the external microwave field. The results indicate that the increase of figure of merit in the gap is very slight when the spin-flip scattering strength increases, but outside the gap it significantly increases with enhancing spin-flip scattering strength. The presence of microwave field results in photon-assisted Andreev reflection and induces the satellite peaks in conductance spectrum. The appropriate match of spin-flip scattering strength, microwave field strength and frequency can significantly enhances the figure of merit of thermoelectric conversion of the device, which can be used as a scheme improving thermoelectric efficiency using microwave frequency.

  12. High Electron Mobility and Disorder Induced by Silver Ion Migration Lead to Good Thermoelectric Performance in the Argyrodite Ag 8 SiSe 6

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Heep, Barbara K.; Weldert, Kai S.; Krysiak, Yasar

    Superionic chalcopyrites have recently attracted interest in their use as potential thermoelectric materials because of extraordinary low thermal conductivities. To overcome long-term stability issues in thermoelectric generators using superionic materials at evaluated temperatures, materials need to be found that show good thermoelectric performance at moderate temperatures. Here, we present the structural and thermoelectric properties of the argyrodite Ag 8SiSe 6, which exhibits promising thermoelectric performance close to room temperature.

  13. Evaluation of Thermoelectric Performance and Durability of Functionalized Skutterudite Legs

    NASA Astrophysics Data System (ADS)

    Skomedal, Gunstein; Kristiansen, Nils R.; Sottong, Reinhard; Middleton, Hugh

    2017-04-01

    Thermoelectric generators are a promising technology for waste heat recovery. As new materials and devices enter a market penetration stage, it is of interest to employ fast and efficient measurement methods to evaluate the long-term stability of thermoelectric materials in combination with metallization and coating (functionalized thermoelectric legs). We have investigated a method for measuring several thermoelectric legs simultaneously. The legs are put under a common temperature gradient, and the electrical characteristics of each leg are measured individually during thermal cycling. Using this method, one can test different types of metallization and coating applied to skutterudite thermoelectric legs and look at the relative changes over time. Postcharacterization of these initial tests with skutterudite legs using a potential Seebeck microprobe and an electron microscope showed that oxidation and interlayer diffusion are the main reasons for the gradual increase in internal resistance and the decrease in open-circuit voltage. Although we only tested skutterudite material in this work, the method is fully capable of testing all kinds of material, metallization, and coating. It is thus a promising method for studying the relationship between failure modes and mechanisms of functionalized thermoelectric legs.

  14. High-performance thermoelectricity in edge-over-edge zinc-porphyrin molecular wires.

    PubMed

    Noori, Mohammed; Sadeghi, Hatef; Lambert, Colin J

    2017-04-20

    If high efficiency organic thermoelectric materials could be identified, then these would open the way to a range of energy harvesting technologies and Peltier coolers using flexible and transparent thin-film materials. We have compared the thermoelectric properties of three zinc porphyrin (ZnP) dimers and a ZnP monomer and found that the "edge-over-edge" dimer formed from stacked ZnP rings possesses a high electrical conductance, negligible phonon thermal conductance and a high Seebeck coefficient of the order of 300 μV K -1 . These combine to yield a predicted room-temperature figure of merit of ZT ≈ 4, which is the highest room-temperature ZT ever reported for a single organic molecule. This high value of ZT is a consequence of the low phonon thermal conductance arising from the stacked nature of the porphyrin rings, which hinders phonon transport through the edge-over-edge molecule and enhances the Seebeck coefficient.

  15. Thermoelectric generators incorporating phase-change materials for waste heat recovery from engine exhaust

    DOEpatents

    Meisner, Gregory P; Yang, Jihui

    2014-02-11

    Thermoelectric devices, intended for placement in the exhaust of a hydrocarbon fuelled combustion device and particularly suited for use in the exhaust gas stream of an internal combustion engine propelling a vehicle, are described. Exhaust gas passing through the device is in thermal communication with one side of a thermoelectric module while the other side of the thermoelectric module is in thermal communication with a lower temperature environment. The heat extracted from the exhaust gasses is converted to electrical energy by the thermoelectric module. The performance of the generator is enhanced by thermally coupling the hot and cold junctions of the thermoelectric modules to phase-change materials which transform at a temperature compatible with the preferred operating temperatures of the thermoelectric modules. In a second embodiment, a plurality of thermoelectric modules, each with a preferred operating temperature and each with a uniquely-matched phase-change material may be used to compensate for the progressive lowering of the exhaust gas temperature as it traverses the length of the exhaust pipe.

  16. Enhanced thermoelectric power and electronic correlations in RuSe₂

    DOE PAGES

    Wang, Kefeng; Wang, Aifeng; Tomic, A.; ...

    2015-03-03

    We report the electronic structure, electric and thermal transport properties of Ru 1-xIr xSe₂ (x ≤ 0.2). RuSe₂ is a semiconductor that crystallizes in a cubic pyrite unit cell. The Seebeck coefficient of RuSe₂ exceeds -200 μV/K around 730 K. Ir substitution results in the suppression of the resistivity and the Seebeck coefficient, suggesting the removal of the peaks in density of states near the Fermi level. Ru 0.8Ir 0.2Se₂ shows a semiconductor-metal crossover at about 30 K. The magnetic field restores the semiconducting behavior. Our results indicate the importance of the electronic correlations in enhanced thermoelectricity of RuSb₂.

  17. Thermoelectric materials and devices

    NASA Technical Reports Server (NTRS)

    Park, Yeonjoon (Inventor); Choi, Sang H. (Inventor); King, Glen C. (Inventor); Elliott, James R. (Inventor); Talcott, Noel A. (Inventor)

    2011-01-01

    New thermoelectric materials comprise highly [111]-oriented twinned group IV alloys on the basal plane of trigonal substrates, which exhibit a high thermoelectric figure of merit and good material performance, and devices made with these materials.

  18. Synthesis and properties of nanocrystalline Bi-Te based thermoelectric materials for energy application

    NASA Astrophysics Data System (ADS)

    Almohaimeed, Sulaiman

    Thermoelectric phenomenon is the science associated with converting thermal energy into electricity based on the Seebeck effect. Bismuth telluride Bi 2Te3 is currently considered to be the state-of-the art thermoelectric material with high efficiency for low temperature applications and is therefore attractive for energy harvesting processes. Nanostructures thermoelectric materials provide a novel way to enhance thermoelectric properties and are considered to be the efficient building blocks for thermoelectric devices. In this work, n- and p-type bulk nanocrystalline Bismuth telluride thermoelectric materials were prepared by mechanical alloying / ball milling technique. The produced nano-crystalline powder were then consolidated using hot compaction under inert atmosphere. The novel processing of these materials maintained the nanostructure in both n- and p-type. Structural properties of the n- and p-types were characterized using X ray diffraction, scanning electron microscopy and transmission electron microscope. These techniques proved that the average grian size of the milled thermoelectric materials was about 20 nm. Accordingly, a Significant improvement in the figure of merit (ZT) is achieved through significant lattice thermal conductivity reduction and Seebeck coefficient improvement. The maximum ZT value for the n-type nanocrystalline thermoelectric was 1.67 at 373 K while the maximum ZT value for the p-type was 1.78 at the same temperature. These values are considered to be the highest values reported for similar materials. Evaluation of the mechanical properties was also performed through microhardness measurement using Vickers micro-hardness test, which shows an enhancement in mechanical properties for the produced materials.

  19. Thermoelectrically cooled cloud physics expansion chamber. [systems engineering and performance prediction

    NASA Technical Reports Server (NTRS)

    Buist, R. J.

    1977-01-01

    The design and fabrication of a thermoelectric chiller for use in chilling a liquid reservoir is described. Acceptance test results establish the accuracy of the thermal model and predict the unit performance under various conditions required by the overall spacelab program.

  20. Performance of a Thermoelectric Device with Integrated Heat Exchangers

    NASA Astrophysics Data System (ADS)

    Barry, Matthew M.; Agbim, Kenechi A.; Chyu, Minking K.

    2015-06-01

    Thermoelectric devices (TEDs) convert heat directly into electrical energy, making them well suited for waste heat recovery applications. An integrated thermoelectric device (iTED) is a restructured TED that allows more heat to enter the p-n junctions, thus producing a greater power output . An iTED has heat exchangers incorporated into the hot-side interconnectors with flow channels directing the working fluid through the heat exchangers. The iTED was constructed of p- and n-type bismuth-telluride semiconductors and copper interconnectors and rectangular heat exchangers. The performance of the iTED in terms of , produced voltage and current , heat input and conversion efficiency for various flow rates (), inlet temperatures (C) ) and load resistances () with a constant cold-side temperature ( = 0C) was conducted experimentally. An increase in had a greater effect on the performance than did an increase in . A 3-fold increase in resulted in a 3.2-, 3.1-, 9.7-, 3.5- and 2.8-fold increase in and respectively. For a constant of 50C, a 3-fold increase in from 3300 to 9920 resulted in 1.6-, 1.6-, 2.6-, 1.5- and 1.9-fold increases in , , , and respectively.

  1. Performance Analysis and Discussion on the Thermoelectric Element Footprint for PV-TE Maximum Power Generation

    NASA Astrophysics Data System (ADS)

    Li, Guiqiang; Zhao, Xudong; Jin, Yi; Chen, Xiao; Ji, Jie; Shittu, Samson

    2018-06-01

    Geometrical optimisation is a valuable way to improve the efficiency of a thermoelectric element (TE). In a hybrid photovoltaic-thermoelectric (PV-TE) system, the photovoltaic (PV) and thermoelectric (TE) components have a relatively complex relationship; their individual effects mean that geometrical optimisation of the TE element alone may not be sufficient to optimize the entire PV-TE hybrid system. In this paper, we introduce a parametric optimisation of the geometry of the thermoelectric element footprint for a PV-TE system. A uni-couple TE model was built for the PV-TE using the finite element method and temperature-dependent thermoelectric material properties. Two types of PV cells were investigated in this paper and the performance of PV-TE with different lengths of TE elements and different footprint areas was analysed. The outcome showed that no matter the TE element's length and the footprint areas, the maximum power output occurs when A n /A p = 1. This finding is useful, as it provides a reference whenever PV-TE optimisation is investigated.

  2. Enhancement of the thermoelectric efficiency in a T-shaped quantum dot system in the linear and nonlinear regimes

    NASA Astrophysics Data System (ADS)

    Gómez-Silva, G.; Orellana, P. A.; Anda, E. V.

    2018-02-01

    In the present work, we investigate the thermoelectric properties of a T-shaped double quantum dot system coupled to two metallic leads incorporating the intra-dot Coulomb interaction. We explore the role of the interference effects and Coulomb blockade on the thermoelectric efficiency of the system in the linear and nonlinear regimes. We studied as well the effect of a Van-Hove singularity of the leads density of states (DOS) at the neighborhood of the Fermi energy, a situation that can be obtained using a carbon nanotube, a graphene nano-ribbon or other contacts with one-dimensional properties. The system is studied above the Kondo temperature. The Coulomb blockade of the electronic charges is studied using the Hubbard III approximation, which properly describes the transport properties of this regime. In the linear response, our results show an enhancement of the thermopower and the figure of merit of the system. For a nonlinear situation, we calculate the thermoelectric efficiency and power output, concluding that the T-shaped double quantum dot is an efficient thermoelectric device. Moreover, we demonstrate the great importance of the DOS Van-Hove singularity at the neighborhood of the Fermi energy to obtain a very significant increase in the thermoelectric efficiency of the system.

  3. Stretchable and flexible thermoelectric polymer composites

    NASA Astrophysics Data System (ADS)

    Slobodian, P.; Riha, P.; Matyas, J.; Olejnik, R.

    2018-03-01

    Polymer composites were manufactured from pristine and oxidized multi-walled carbon nanotubes and ethylene-octene copolymer. The composites had thermoelectric properties and exhibit thermoelectric effect, that is, the conversion of temperature differences into electricity. Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy of the multi-walled carbon nanotubes in ethylene-octene copolymer matrix showed that the oxidation with HNO3 or KMnO4 enhanced its p-type electrical conductivity and that the thermoelectric power increase was proportional to the formation of new oxygen-containing functional groups on the surface of carbon nanotubes.

  4. Facile Preparation of Highly Conductive Metal Oxides by Self-Combustion for Solution-Processed Thermoelectric Generators.

    PubMed

    Kang, Young Hun; Jang, Kwang-Suk; Lee, Changjin; Cho, Song Yun

    2016-03-02

    Highly conductive indium zinc oxide (IZO) thin films were successfully fabricated via a self-combustion reaction for application in solution-processed thermoelectric devices. Self-combustion efficiently facilitates the conversion of soluble precursors into metal oxides by lowering the required annealing temperature of oxide films, which leads to considerable enhancement of the electrical conductivity of IZO thin films. Such enhanced electrical conductivity induced by exothermic heat from a combustion reaction consequently yields high performance IZO thermoelectric films. In addition, the effect of the composition ratio of In to Zn precursors on the electrical and thermoelectric properties of the IZO thin films was investigated. IZO thin films with a composition ratio of In:Zn = 6:2 at the low annealing temperature of 350 °C showed an enhanced electrical conductivity, Seebeck coefficient, and power factor of 327 S cm(-1), 50.6 μV K(-1), and 83.8 μW m(-1) K(-2), respectively. Moreover, the IZO thin film prepared at an even lower temperature of 300 °C retained a large power factor of 78.7 μW m(-1) K(-2) with an electrical conductivity of 168 S cm(-1). Using the combustive IZO precursor, a thermoelectric generator consisting of 15 legs was fabricated by a printing process. The thermoelectric array generated a thermoelectric voltage of 4.95 mV at a low temperature difference (5 °C). We suggest that the highly conductive IZO thin films by self-combustion may be utilized for fabricating n-type flexible printed thermoelectric devices.

  5. Chemical Welding on Semimetallic TiS2 Nanosheets for High-Performance Flexible n-Type Thermoelectric Films.

    PubMed

    Zhou, Yuan; Wan, Juanyong; Li, Qi; Chen, Lei; Zhou, Jiyang; Wang, Heao; He, Dunren; Li, Xiaorui; Yang, Yaocheng; Huang, Huihui

    2017-12-13

    Solution-based processing of two-dimensional (2D) materials provides the possibility of allowing these materials to be incorporated into large-area thin films, which can translate the interesting fundamental properties of 2D materials into available devices. Here, we report for the first time a novel chemical-welding method to achieve high-performance flexible n-type thermoelectric films using 2D semimetallic TiS 2 nanosheets. We employ chemically exfoliated TiS 2 nanosheets bridged with multivalent cationic metal Al 3+ to cross-link the nearby sheets during the film deposition process. We find that such a treatment can greatly enhance the stability of the film and can improve the power factor by simultaneously increasing the Seebeck coefficient and electrical conductivity. The resulting TiS 2 nanosheet-based flexible film shows a room temperature power factor of ∼216.7 μW m -1 K -2 , which is among the highest chemically exfoliated 2D transition-metal dichalcogenide nanosheet-based films and comparable to the best flexible n-type thermoelectric films, to our knowledge, indicating its potential applications in wearable electronics.

  6. Enhancement of thermoelectric characteristics in AlGaN/GaN films deposited on inverted pyramidal Si surfaces

    NASA Astrophysics Data System (ADS)

    Yalamarthy, Ananth Saran; So, Hongyun; Senesky, Debbie G.

    2017-07-01

    In this letter, we demonstrate an engineering strategy to boost thermoelectric power factor via geometry-induced properties of the pyramid structure. Aluminum gallium nitride (AlGaN)/GaN heterostructured films grown on inverted pyramidal silicon (Si) demonstrate higher power factor as compared to those grown on conventional flat Si substrates. We found that the magnitude of the Seebeck coefficient at room temperature increased from approximately 297 μVK-1 for the flat film to approximately 849 μVK-1 for the film on inverted pyramidal Si. In addition, the "effective" electrical conductivity of the AlGaN/GaN on the inverted pyramidal structure increased compared to the flat structure, generating an enhancement of thermoelectric power factor. The results demonstrate how manipulation of geometry can be used to achieve better thermoelectric characteristics in a manner that could be scaled to a variety of different material platforms.

  7. Thermoelectric Properties of Poly(selenophene- co-3, 4-ethylenedioxythiophene) via Electropolymerization

    NASA Astrophysics Data System (ADS)

    Gu, Hua; Ming, Shouli; Lin, Kaiwen; Liu, Hongtao; Chen, Shuai; Lu, Baoyang; Xu, Jingkun

    2017-05-01

    Conducting polymers as thermoelectric (TE) materials have drawn extensive attention most recently because they are intrinsically light weight, flexible, highly processable, abundant in nature, and have especially low thermal conductivity. Relative studies have been focused on several typical structures such as polyacetylene, polyaniline, polythiophenes. However, TE performance of polyselenophenes have drawn very little attention because of its unstability and difficulty in synthesis. Previously, our group demonstrated that polyselenophene revealed high Seebeck coefficient (>180 μV K-1), but their electrical conductivity was very low (typically 10-5-10-2 S cm-1). For the sake of improving the thermoelectric performance of polyselenophene, the simplest and most effective method is to copolymerize with other high-performance thermoelectric materials. Herein, 3,4-ethylenedioxythiophene (EDOT), the monomer precursor of poly(3,4-ethylenedioxythiophene) (probably the best organic thermoelectric materials so far) was chosen to copolymerize with selenophene (SE) under different feeding ratios via electropolymerization to improve the thermoelectric performance. It is found that the electrical conductivity of all the copolymer films was obviously enhanced with the highest value of 0.91 S cm-1 by inserting EDOT in the conjugated block, whereas their Seebeck coefficient was brought down to 12 μV K-1. In this work, We obtained four different feeding ratios copolymers of SE and EDOT, 2:1 (PA), 1:1 (PB), 1:2 (PC), and 1:5 (PD). The copolymers had improved electrical conductivity and environmental stability compared with polyselenophene. Furthermore, with increasing the feeding ratio of EDOT, the TE performance of the copolymers was significantly improved.

  8. Performance Model and Sensitivity Analysis for a Solar Thermoelectric Generator

    NASA Astrophysics Data System (ADS)

    Rehman, Naveed Ur; Siddiqui, Mubashir Ali

    2017-03-01

    In this paper, a regression model for evaluating the performance of solar concentrated thermoelectric generators (SCTEGs) is established and the significance of contributing parameters is discussed in detail. The model is based on several natural, design and operational parameters of the system, including the thermoelectric generator (TEG) module and its intrinsic material properties, the connected electrical load, concentrator attributes, heat transfer coefficients, solar flux, and ambient temperature. The model is developed by fitting a response curve, using the least-squares method, to the results. The sample points for the model were obtained by simulating a thermodynamic model, also developed in this paper, over a range of values of input variables. These samples were generated employing the Latin hypercube sampling (LHS) technique using a realistic distribution of parameters. The coefficient of determination was found to be 99.2%. The proposed model is validated by comparing the predicted results with those in the published literature. In addition, based on the elasticity for parameters in the model, sensitivity analysis was performed and the effects of parameters on the performance of SCTEGs are discussed in detail. This research will contribute to the design and performance evaluation of any SCTEG system for a variety of applications.

  9. Electrodeposition of bismuth:tellurium nanowire arrays into porous alumina templates for thermoelectric applications

    NASA Astrophysics Data System (ADS)

    Trahey, Lynn

    Bismuth telluride is a well-known thermoelectric material for refrigeration applications. Thermoelectrics possess several advantages over conventional refrigeration and power generation devices, yet are not widely-used due to low efficiencies. It has been predicted and shown experimentally that the efficiency of thermoelectric devices increases when the semiconducting materials have reduced dimensions. Therefore, the aim of this research was to show enhanced thermoelectric efficiency in one-dimensional nanowires. The nanowires were synthesized via electrochemical deposition into porous alumina templates. Electrodeposition is a versatile technique that ensures electrical continuity in the deposited material. The nanowire templates, porous alumina, were made by the double anodization of high-purity aluminum foil in oxalic acid solutions. This technique produces parallel, hexagonally packed, and nanometer-range diameter pores that can reach high aspect ratios (greater than 2000:1). The main anodization variables (electrolyte concentration, applied potential, 2nd anodization time, and temperature) were studied systematically in order to deconvolute their effects on the resulting pores and to obtain high aspect ratio pores. The porous alumina is of great importance because the pore dimensions determine the dimensions of the electrodeposited nanowires, which influence the thermoelectric performance of the nanowire arrays. Nanowire arrays were characterized in several ways. Powder X-ray diffraction was used to assess crystallinity and preferred orientation of the nanowires, revealing that the nanowires are highly crystalline and grow with strong preferred orientation such that the material is suited for optimal thermoelectric performance. Scanning electron microscopy was used to evaluate the nanowire nucleation percentage and growth-front uniformity, both of which were enhanced by pulsed-potential electrodeposition. Compositional analysis via electron microprobe indicates

  10. Silicide/Silicon Hetero-Junction Structure for Thermoelectric Applications.

    PubMed

    Jun, Dongsuk; Kim, Soojung; Choi, Wonchul; Kim, Junsoo; Zyung, Taehyoung; Jang, Moongyu

    2015-10-01

    We fabricated silicide/silicon hetero-junction structured thermoelectric device by CMOS process for the reduction of thermal conductivity with the scatterings of phonons at silicide/silicon interfaces. Electrical conductivities, Seebeck coefficients, power factors, and temperature differences are evaluated using the steady state analysis method. Platinum silicide/silicon multilayered structure showed an enhanced Seebeck coefficient and power factor characteristics, which was considered for p-leg element. Also, erbium silicide/silicon structure showed an enhanced Seebeck coefficient, which was considered for an n-leg element. Silicide/silicon multilayered structure is promising for thermoelectric applications by reducing thermal conductivity with an enhanced Seebeck coefficient. However, because of the high thermal conductivity of the silicon packing during thermal gradient is not a problem any temperature difference. Therefore, requires more testing and analysis in order to overcome this problem. Thermoelectric generators are devices that based on the Seebeck effect, convert temperature differences into electrical energy. Although thermoelectric phenomena have been used for heating and cooling applications quite extensively, it is only in recent years that interest has increased in energy generation.

  11. Thermoelectric performance of SrTiO3 enhanced by nanostructuring-self-assembled particulate film of nanocubes.

    PubMed

    Dang, Feng; Wan, Chunlei; Park, Nam-Hee; Tsuruta, Kazuki; Seo, Won-Seon; Koumoto, Kunihito

    2013-11-13

    Self-assembled particulate films with a uniform structure over a large area were prepared from La-SrTiO3 nanocubes for thermoelectric applications. UV irradiation was used to assist the formation of particulate film for decomposition of the organic phase in situ to obtain a mechanically robust structure at high temperature. The thermoelectric properties of the particulate film were measured after calcination at 1000 °C under a reductive atmosphere (Ar/H2 = 60/40). A Seebeck coefficient of S = -239 ± 24 μV/K, electrical conductivity of σ = 160 ± 5 S/cm, and thermal conductivity of κ ≈ 1.5 W/mK were obtained for a self-assembled particulate film (La: 5%) corresponding to a ZT value of 0.2 at room temperature, which exceeded that of a La-SrTiO3 single crystal with similar composition.

  12. Chemical intuition for high thermoelectric performance in monolayer black phosphorus, α-arsenene and aW-antimonene

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Peng, Bo; Zhang, Hao; Shao, Hezhu

    Identifying materials with intrinsically high thermoelectric performance remains a challenge even with the aid of a high-throughput search. Here, using a chemically intuitive approach based on the bond-orbital theory, three anisotropic 2D group-V materials (monolayer black phosphorus, α-arsenene, and aW-antimonene) are identified as candidates for high thermoelectric energy conversion efficiency. Concepts, such as bond length, bond angle, and bond strength, are used to explain the trends in their electronic properties, such as the band gap and the effective mass. Our first principles calculations confirm that high carrier mobilities and large Seebeck coefficients can be obtained at the same time inmore » these materials, due to complex Fermi surfaces originating from the anisotropic structures. An intuitive understanding of how the bonding character affects phonon transport is also provided with emphasis on the importance of bonding strength and bond anharmonicity. High thermoelectric performance is observed in these materials. In conclusion, our approach provides a powerful tool to identify new thermoelectric materials and evaluate their transport properties.« less

  13. Chemical intuition for high thermoelectric performance in monolayer black phosphorus, α-arsenene and aW-antimonene

    DOE PAGES

    Peng, Bo; Zhang, Hao; Shao, Hezhu; ...

    2017-11-21

    Identifying materials with intrinsically high thermoelectric performance remains a challenge even with the aid of a high-throughput search. Here, using a chemically intuitive approach based on the bond-orbital theory, three anisotropic 2D group-V materials (monolayer black phosphorus, α-arsenene, and aW-antimonene) are identified as candidates for high thermoelectric energy conversion efficiency. Concepts, such as bond length, bond angle, and bond strength, are used to explain the trends in their electronic properties, such as the band gap and the effective mass. Our first principles calculations confirm that high carrier mobilities and large Seebeck coefficients can be obtained at the same time inmore » these materials, due to complex Fermi surfaces originating from the anisotropic structures. An intuitive understanding of how the bonding character affects phonon transport is also provided with emphasis on the importance of bonding strength and bond anharmonicity. High thermoelectric performance is observed in these materials. In conclusion, our approach provides a powerful tool to identify new thermoelectric materials and evaluate their transport properties.« less

  14. Performance study of thermo-electric generator

    NASA Astrophysics Data System (ADS)

    Rohit, G.; Manaswini, D.; Kotebavi, Vinod; R, Nagaraja S.

    2017-07-01

    Devices like automobiles, stoves, ovens, boilers, kilns and heaters dissipate large amount of waste heat. Since most of this waste heat goes unused, the efficiency of these devices is drastically reduced. A lot of research is being conducted on the recovery of the waste heat, among which Thermoelectric Generators (TEG) is one of the popular method. TEG is a semiconductor device that produces electric potential difference when a thermal gradient develops on it. This paper deals with the study of performance of a TEG module for different hot surface temperatures. Performance characteristics used here are voltage, current and power developed by the TEG. One side of the TEG was kept on a hot plate where uniform heat flux was supplied to that. And the other side was cooled by supplying cold water. The results show that the output power increases significantly with increase in the temperature of the hot surface.

  15. Convergence of electronic bands for high performance bulk thermoelectrics.

    PubMed

    Pei, Yanzhong; Shi, Xiaoya; LaLonde, Aaron; Wang, Heng; Chen, Lidong; Snyder, G Jeffrey

    2011-05-05

    Thermoelectric generators, which directly convert heat into electricity, have long been relegated to use in space-based or other niche applications, but are now being actively considered for a variety of practical waste heat recovery systems-such as the conversion of car exhaust heat into electricity. Although these devices can be very reliable and compact, the thermoelectric materials themselves are relatively inefficient: to facilitate widespread application, it will be desirable to identify or develop materials that have an intensive thermoelectric materials figure of merit, zT, above 1.5 (ref. 1). Many different concepts have been used in the search for new materials with high thermoelectric efficiency, such as the use of nanostructuring to reduce phonon thermal conductivity, which has led to the investigation of a variety of complex material systems. In this vein, it is well known that a high valley degeneracy (typically ≤6 for known thermoelectrics) in the electronic bands is conducive to high zT, and this in turn has stimulated attempts to engineer such degeneracy by adopting low-dimensional nanostructures. Here we demonstrate that it is possible to direct the convergence of many valleys in a bulk material by tuning the doping and composition. By this route, we achieve a convergence of at least 12 valleys in doped PbTe(1-x)Se(x) alloys, leading to an extraordinary zT value of 1.8 at about 850 kelvin. Band engineering to converge the valence (or conduction) bands to achieve high valley degeneracy should be a general strategy in the search for and improvement of bulk thermoelectric materials, because it simultaneously leads to a high Seebeck coefficient and high electrical conductivity. ©2011 Macmillan Publishers Limited. All rights reserved

  16. Evaluation of Temperature-Dependent Effective Material Properties and Performance of a Thermoelectric Module

    NASA Astrophysics Data System (ADS)

    Chien, Heng-Chieh; Chu, En-Ting; Hsieh, Huey-Lin; Huang, Jing-Yi; Wu, Sheng-Tsai; Dai, Ming-Ji; Liu, Chun-Kai; Yao, Da-Jeng

    2013-07-01

    We devised a novel method to evaluate the temperature-dependent effective properties of a thermoelectric module (TEM): Seebeck coefficient ( S m), internal electrical resistance ( R m), and thermal conductance ( K m). After calculation, the effective properties of the module are converted to the average material properties of a p- n thermoelectric pillar pair inside the module: Seebeck coefficient ( S TE), electrical resistivity ( ρ TE), and thermal conductivity ( k TE). For a commercial thermoelectric module (Altec 1091) chosen to verify the novel method, the measured S TE has a maximum value at bath temperature of 110°C; ρ TE shows a positive linear trend dependent on the bath temperature, and k TE increases slightly with increasing bath temperature. The results show the method to have satisfactory measurement performance in terms of practicability and reliability; the data for tests near 23°C agree with published values.

  17. Surface oxidation and thermoelectric properties of indium-doped tin telluride nanowires.

    PubMed

    Li, Zhen; Xu, Enzhi; Losovyj, Yaroslav; Li, Nan; Chen, Aiping; Swartzentruber, Brian; Sinitsyn, Nikolai; Yoo, Jinkyoung; Jia, Quanxi; Zhang, Shixiong

    2017-09-14

    The recent discovery of excellent thermoelectric properties and topological surface states in SnTe-based compounds has attracted extensive attention in various research areas. Indium doped SnTe is of particular interest because, depending on the doping level, it can either generate resonant states in the bulk valence band leading to enhanced thermoelectric properties, or induce superconductivity that coexists with topological states. Here we report on the vapor deposition of In-doped SnTe nanowires and the study of their surface oxidation and thermoelectric properties. The nanowire growth is assisted by Au catalysts, and their morphologies vary as a function of substrate position and temperature. Transmission electron microscopy characterization reveals the formation of an amorphous surface in single crystalline nanowires. X-ray photoelectron spectroscopy studies suggest that the nanowire surface is composed of In 2 O 3 , SnO 2 , Te and TeO 2 which can be readily removed by argon ion sputtering. Exposure of the cleaned nanowires to atmosphere leads to rapid oxidation of the surface within only one minute. Characterization of electrical conductivity σ, thermopower S, and thermal conductivity κ was performed on the same In-doped nanowire which shows suppressed σ and κ but enhanced S yielding an improved thermoelectric figure of merit ZT compared to the undoped SnTe.

  18. Thermoelectric Properties of Topological Crystalline Insulator Nanowires

    NASA Astrophysics Data System (ADS)

    Xu, Enzhi

    Bulk lead telluride (PbTe) and its alloy compounds are well-known thermoelectric materials for electric power generation. Tin telluride (SnTe) which has the same rock-salt crystalline structure as PbTe has recently been demonstrated to host unique topological surface states that may favor improved thermoelectric properties. In this thesis work, we studied the thermoelectric properties of single-crystalline nanowires of the SnTe family compounds, i.e. undoped SnTe, PbTe, (Sn,Pb)Te alloy, and In-doped SnTe, all of which were grown by a vapor transport approach. We measured the thermopower S, electrical conductivity sigma and thermal conductivity kappa on each individual nanowire over a temperature range of 25 - 300 K, from which the thermoelectric figures of merit ZTs were determined. In comparison to PbTe nanowires, SnTe and (Sn,Pb)Te has lower thermopower but significantly higher electrical conductivity. Both SnTe and (Sn,Pb)Te nanowires showed enhanced thermopower and suppressed thermal conductivity, compared to their bulk counterparts. The enhancement of thermopower may result from the existence of topological surface states, while the suppression of thermal conductivity may relate to the increased phonon-surface scattering in nanowires. Moreover, indium doping suppresses both electrical and thermal conductivities but enhances thermopower, yielding an improved figure of merit ZT. Our results highlight nanostructuring in combination with alloying or doping as an important approach to enhancing thermoelectric properties. In spite of excellent thermoelectric properties and robust topological surface states, we found that the nanowire surface is subject to fast oxidation. In particular, we demonstrated that exposure of In-doped SnTe nanowires to air leads to surface oxidation within only one minute. Transmission electron microscopy characterization suggests the amorphous nature of the surface, and X-ray photoelectron spectroscopy studies identify the oxide species on

  19. Fabrications of Polyaniline Films by Pulse Electrodeposition in Acidic Solutions with Different Anions and Their Thermoelectric Performances

    NASA Astrophysics Data System (ADS)

    Yang, Weifang; Xu, Han; Li, Yuanyuan; Wang, Wei

    2017-08-01

    Polymerization of aniline was prepared by the pulse potentiostatic method in H3PO4, HClO4 and H2SO4 acidic solutions. The morphologies and thermoelectric performances were analyzed by scanning electron microscopy, Seebeck coefficient ( S) and resistivity ( R) measurements. The results show that flake polyaniline (PANI) films can be obtained in H3PO4 and HClO4 acidic solutions, and porous PANI films with nanofiber-overlapped structures can be prepared in H2SO4 solution under the same pulse parameters. PANI films prepared in the three solutions are all p-type thermoelectric materials. PANI films polymerized in H2SO4 solution possess the highest S (30.2 μV K-1) and lowest R (1.6 × 10-3 Ω m) compared with those prepared in H3PO4 and HClO4 solutions, indicating that nanofiber-overlapped structures formed in H2SO4 solution contribute better thermoelectric performance. In addition, the effects of pulse parameters (anodic potential φ a, anodic pulse duration t a and cathodic pulse duration t c) on the surface morphologies and thermoelectric performances of PANI films were systematically investigated.

  20. Exploring High-Performance n-Type Thermoelectric Composites Using Amino-Substituted Rylene Dimides and Carbon Nanotubes.

    PubMed

    Wu, Guangbao; Zhang, Zhi-Guo; Li, Yongfang; Gao, Caiyan; Wang, Xin; Chen, Guangming

    2017-06-27

    Taking advantage of the high electrical conductivity of a single-walled carbon nanotube (SWCNT) and the large Seebeck coefficient of rylene diimide, a convenient strategy is proposed to achieve high-performance n-type thermoelectric (TE) composites containing a SWCNT and amino-substituted perylene diimide (PDINE) or naphthalene diimide (NDINE). The obtained n-type composites display greatly enhanced TE performance with maximum power factors of 112 ± 8 (PDINE/SWCNT) and 135 ± 14 (NDINE/SWCNT) μW m -1 K -2 . A short doping time of 0.5 h can ensure high TE performance. The corresponding TE module consisting of five p-n junctions reaches a large output power of 3.3 μW under a 50 °C temperature gradient. In addition, the n-type composites exhibit high air stability and excellent thermal stability. This design strategy benefits the future fabricating of high-performance n-type TE materials and devices.

  1. Thermoelectric Properties of Epitaxial β-FeSi2 Thin Films on Si(111) and Approach for Their Enhancement

    NASA Astrophysics Data System (ADS)

    Taniguchi, Tatsuhiko; Sakane, Shunya; Aoki, Shunsuke; Okuhata, Ryo; Ishibe, Takafumi; Watanabe, Kentaro; Suzuki, Takeyuki; Fujita, Takeshi; Sawano, Kentarou; Nakamura, Yoshiaki

    2017-05-01

    We have investigated the intrinsic thermoelectric properties of epitaxial β-FeSi2 thin films and the impact of phosphorus (P) doping. Epitaxial β-FeSi2 thin films with single phase were grown on Si(111) substrates by two different techniques in an ultrahigh-vacuum molecular beam epitaxy (MBE) system: solid-phase epitaxy (SPE), where iron silicide films formed by codeposition of Fe and Si at room temperature were recrystallized by annealing at 530°C to form epitaxial β-FeSi2 thin films on Si(111) substrates, and MBE of β-FeSi2 thin films on epitaxial β-FeSi2 templates formed on Si(111) by reactive deposition epitaxy (RDE) at 530°C (RDE + MBE). Epitaxial SPE thin films based on codeposition had a flatter surface and more abrupt β-FeSi2/Si(111) interface than epitaxial RDE + MBE thin films. We investigated the intrinsic thermoelectric properties of the epitaxial β-FeSi2 thin films on Si(111), revealing lower thermal conductivity and higher electrical conductivity compared with bulk β-FeSi2. We also investigated the impact of doping on the Seebeck coefficient of bulk and thin-film β-FeSi2. A route to enhance the thermoelectric performance of β-FeSi2 is proposed, based on (1) fabrication of thin-film structures for high electrical conductivity and low thermal conductivity, and (2) proper choice of doping for high Seebeck coefficient.

  2. Low lattice thermal conductivity and good thermoelectric performance of cinnabar

    NASA Astrophysics Data System (ADS)

    Zhao, Yinchang; Dai, Zhenhong; Lian, Chao; Zeng, Shuming; Li, Geng; Ni, Jun; Meng, Sheng

    2017-11-01

    Based on the combination of first-principles calculations, Boltzmann transport equation, and electron-phonon interaction (EPI), we investigate the thermal and electronic transport properties of crystalline cinnabar (α -HgS ). The calculated lattice thermal conductivity κL is remarkably low, e.g., 0.60 Wm-1K-1 at 300 K , which is about 30 % of the value for the typical thermoelectric material PbTe. Via taking fully into account the k dependence of the electron relaxation time computed from the EPI matrix, the accurate numerical results of thermopower S , electrical conductivity σ , and electronic thermal conductivity κE are obtained. The calculated power factor S2σ is relatively high while the value of κE is negligible, which, together with the fairly low κL, leads to a good thermoelectric performance in the n -type doped α -HgS , with the figure of merit z T even exceeding 1.4. Our analyses reveal that (i) the large weighted phase space and the quite low phonon group velocity result in the low κL, (ii) the presence of flat band around the Fermi level combined with the large band gap causes the high S , and (iii) the small electron linewidths of the conduction band lead to a large relaxation time and thus a relatively high σ . These results support that α -HgS is a potential candidate for thermoelectric applications.

  3. Nanostructured Bulk Thermoelectric Generator for Efficient Power Harvesting for Self-powered Sensor Networks

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zhang, Yanliang; Butt, Darryl; Agarwal, Vivek

    2015-07-01

    The objective of this Nuclear Energy Enabling Technology research project is to develop high-efficiency and reliable thermoelectric generators for self-powered wireless sensors nodes utilizing thermal energy from nuclear plant or fuel cycle. The power harvesting technology has crosscutting significance to address critical technology gaps in monitoring nuclear plants and fuel cycle. The outcomes of the project will lead to significant advancement in sensors and instrumentation technology, reducing cost, improving monitoring reliability and therefore enhancing safety. The self-powered wireless sensor networks could support the long-term safe and economical operation of all the reactor designs and fuel cycle concepts, as well asmore » spent fuel storage and many other nuclear science and engineering applications. The research is based on recent breakthroughs in high-performance nanostructured bulk (nanobulk) thermoelectric materials that enable high-efficiency direct heat-to-electricity conversion over a wide temperature range. The nanobulk thermoelectric materials that the research team at Boise State University and University of Houston has developed yield up to a 50% increase in the thermoelectric figure of merit, ZT, compared with state-of-the-art bulk counterparts. This report focuses on the selection of optimal thermoelectric materials for this project. The team has performed extensive study on two thermoelectric materials systems, i.e. the half-Heusler materials, and the Bismuth-Telluride materials. The report contains our recent research results on the fabrication, characterization and thermoelectric property measurements of these two materials.« less

  4. Synthesis and thermoelectric properties of Rashba semiconductor BiTeBr with intensive texture.

    PubMed

    Xin, Jia-Zhan; Fu, Chen-Guang; Shi, Wu-Jun; Li, Guo-Wei; Auffermann, Gudrun; Qi, Yan-Peng; Zhu, Tie-Jun; Zhao, Xin-Bing; Felser, Claudia

    2018-01-01

    Bismuth tellurohalides with Rashba-type spin splitting exhibit unique Fermi surface topology and are developed as promising thermoelectric materials. However, BiTeBr, which belongs to this class of materials, is rarely investigated in terms of the thermoelectric transport properties. In the study, polycrystalline bulk BiTeBr with intensive texture was synthesized via spark plasma sintering (SPS). Additionally, its thermoelectric properties above room temperature were investigated along both the in-plane and out-plane directions, and they exhibit strong anisotropy. Low sound velocity along two directions is found and contributes to its low lattice thermal conductivity. Polycrystalline BiTeBr exhibits relatively good thermoelectric performance along the in-plane direction, with a maximum dimensionless figure of merit (ZT) of 0.35 at 560 K. Further enhancements of ZT are expected by utilizing systematic optimization strategies.

  5. Effect of crystal size distribution on thermoelectric performance for Lanthanum-doped strontium titanate bulk material

    NASA Astrophysics Data System (ADS)

    Zhang, Boyu; Wang, Jun; Yaer, Xinba; Huo, Zhenzhen; Wu, Yin; Li, Yan; Miao, Lei; Liu, Chengyan; Zou, Tao; Ma, Wen

    2015-07-01

    Effect of crystal size distribution on thermoelectric performance of Lanthanum-doped strontium titanate (La-SrTiO3) ceramics are investigated in this study. Thermoelectric performance measurement, coupled with microstructure studies, shows that the electrical conductivity strongly depends on the crystal size, potential barrier on the grain boundary and porosity. Meantime, because the average potential barriers height are increased along with the reduction of crystal size, the Seebeck coefficients are increased by energy filtering effect at the large number of grain boundaries. As a result, by controlling of crystal size distribution, ZT value of La-SrTiO3 is improved.

  6. Thermoelectric refrigerator having improved temperature stabilization means

    DOEpatents

    Falco, Charles M.

    1982-01-01

    A control system for thermoelectric refrigerators is disclosed. The thermoelectric refrigerator includes at least one thermoelectric element that undergoes a first order change at a predetermined critical temperature. The element functions as a thermoelectric refrigerator element above the critical temperature, but discontinuously ceases to function as a thermoelectric refrigerator element below the critical temperature. One example of such an arrangement includes thermoelectric refrigerator elements which are superconductors. The transition temperature of one of the superconductor elements is selected as the temperature control point of the refrigerator. When the refrigerator attempts to cool below the point, the metals become superconductors losing their ability to perform as a thermoelectric refrigerator. An extremely accurate, first-order control is realized.

  7. Co-precipitation synthesis of nanostructured Cu3SbSe4 and its Sn-doped sample with high thermoelectric performance.

    PubMed

    Li, Di; Li, Rui; Qin, Xiao-Ying; Song, Chun-Jun; Xin, Hong-Xing; Wang, Ling; Zhang, Jian; Guo, Guang-lei; Zou, Tian-Hua; Liu, Yong-Fei; Zhu, Xiao-Guang

    2014-01-28

    Large-scale fabrication of nanostructured Cu3SbSe4 and its Sn-doped sample Cu3Sb0.98Sn0.02Se4 through a low-temperature co-precipitation route is reported. The effects of hot-pressing temperatures, time and Sn doping on the thermoelectric properties of Cu3SbSe4 are explored. The maximum figure of merit ZTmax obtained here reaches 0.62 for the un-doped Cu3SbSe4, which is three times as large as that of Cu3SbSe4 synthesized by the fusion method. Due to the ameliorated power factor by optimized carrier concentration and the reduced lattice thermal conductivity by enhanced phonon scattering at grain interfaces, Sn doping leads to an improvement of thermoelectric performance as compared to Cu3SbSe4. The maximum ZT for Cu3Sb0.98Sn0.02Se4 is 1.05 in this work, which is 50% larger than the largest value reported.

  8. Thermoelectric properties of PEDOT nanowire/PEDOT hybrids.

    PubMed

    Zhang, Kun; Qiu, Jingjing; Wang, Shiren

    2016-04-21

    Freestanding poly(3,4-ethylenedioxythiophene) (PEDOT) nanowires were synthesized by template-confined in situ polymerization, and then integrated into polystyrene sulfonate (PSS)-doped PEDOT and tosylate-doped PEDOT hosts, respectively. The hybrid morphologies were characterized by atomic force microscopy, indicating the homogeneous dispersion of PEDOT nanowires. The thermoelectric properties of the resultant hybrids were measured, and the power factor was found to be enhanced by 9-fold in comparison with PSS mixed with 5 vol% dimethyl sulfoxide while the low thermal conductivity was still maintained. Such a significant improvement could be attributed to the synergistic effects of interfacial energy filtering, component contributions, and changes of carrier concentrations in the host materials. Upon addition of 0.2 wt% PEDOT nanowires, the resultant composites demonstrated a power factor as high as 446.6 μW m(-1) K(-2) and the thermoelectric figure of merit could reach 0.44 at room temperature. The thermoelectric devices were investigated by using the PEDOT nanowire/PEDOT hybrid as a p-type leg and nitrogen-doped graphene as an n-type leg. The normalized power output was as high as ∼0.5 mW m(-2) for a temperature gradient of ΔT = 10.1 °C, indicating great potential for practical applications. These findings open up a new route towards high-performance organic thermoelectric materials and devices.

  9. Solar thermoelectric generators

    NASA Technical Reports Server (NTRS)

    1977-01-01

    The methods, the findings and the conclusions of a study for the design of a Solar Thermoelectric Generator (STG) intended for use as a power source for a spacecraft orbiting the planet Mercury are discussed. Several state-of-the-art thermoelectric technologies in the intended application were considered. The design of various STG configurations based on the thermoelectric technology selected from among the various technologies was examined in detail and a recommended STG design was derived. The performance characteristics of the selected STG technology and associated design were studied in detail as a function of the orbital characteristics of the STG in Mercury and throughout the orbit of Mercury around the sun.

  10. Thermoelectricity Generation and Electron-Magnon Scattering in a Natural Chalcopyrite Mineral from a Deep-Sea Hydrothermal Vent.

    PubMed

    Ang, Ran; Khan, Atta Ullah; Tsujii, Naohito; Takai, Ken; Nakamura, Ryuhei; Mori, Takao

    2015-10-26

    Current high-performance thermoelectric materials require elaborate doping and synthesis procedures, particularly in regard to the artificial structure, and the underlying thermoelectric mechanisms are still poorly understood. Here, we report that a natural chalcopyrite mineral, Cu1+x Fe1-x S2 , obtained from a deep-sea hydrothermal vent can directly generate thermoelectricity. The resistivity displayed an excellent semiconducting character, and a large thermoelectric power and high power factor were found in the low x region. Notably, electron-magnon scattering and a large effective mass was detected in this region, thus suggesting that the strong coupling of doped carriers and antiferromagnetic spins resulted in the natural enhancement of thermoelectric properties during mineralization reactions. The present findings demonstrate the feasibility of thermoelectric energy generation and electron/hole carrier modulation with natural materials that are abundant in the Earth's crust. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. Thermoelectricity in atom-sized junctions at room temperatures

    PubMed Central

    Tsutsui, Makusu; Morikawa, Takanori; Arima, Akihide; Taniguchi, Masateru

    2013-01-01

    Atomic and molecular junctions are an emerging class of thermoelectric materials that exploit quantum confinement effects to obtain an enhanced figure of merit. An important feature in such nanoscale systems is that the electron and heat transport become highly sensitive to the atomic configurations. Here we report the characterization of geometry-sensitive thermoelectricity in atom-sized junctions at room temperatures. We measured the electrical conductance and thermoelectric power of gold nanocontacts simultaneously down to the single atom size. We found junction conductance dependent thermoelectric voltage oscillations with period 2e2/h. We also observed quantum suppression of thermovoltage fluctuations in fully-transparent contacts. These quantum confinement effects appeared only statistically due to the geometry-sensitive nature of thermoelectricity in the atom-sized junctions. The present method can be applied to various nanomaterials including single-molecules or nanoparticles and thus may be used as a useful platform for developing low-dimensional thermoelectric building blocks. PMID:24270238

  12. Pb-for-Bi substitution for enhancing thermoelectric characteristics of [(Bi,Pb)2Ba2O4+/-ω]0.5CoO2

    NASA Astrophysics Data System (ADS)

    Sakai, K.; Karppinen, M.; Chen, J. M.; Liu, R. S.; Sugihara, S.; Yamauchi, H.

    2006-06-01

    We report strongly enhanced thermoelectric characteristics for a misfit-layered oxide, [Bi2Ba2O4±ω]0.5CoO2, in a wide temperature range, as achieved through substituting up to 20% of Bi by Pb. The Pb substitution kept the thermal conductivity (κ) unchanged but decreased the electrical resistivity (ρ) and increased the Seebeck coefficient (S) simultaneously, such that a three-fold enhancement in the thermoelectric figure of merit, Z (≡S2/ρκ), was realized. At the same time x-ray absorption near-edge structure data indicated that the valence and spin states of Co are not affected by the Pb-for-Bi substitution.

  13. Performance testing of thermoelectric generators including Voyager and LES 8/9 flight results

    NASA Technical Reports Server (NTRS)

    Garvey, L.; Stapfer, G.

    1979-01-01

    Several thermoelectric generators ranging in output power from 0.5 to 155 W have been completed or are undergoing testing at JPL. These generators represent a wide range of technologies, using Bi2Te3, PbTe and SiGe thermoelectric materials. Several of these generators are of a developmental type, such as HPG S/N2, and others are representative of Transit and Multi-Hundred Watt (MHW) Technology. Representative flight performance data of LES 8/9 and Voyager RTG's are presented and compared with the DEGRA computer program based on the data observed from tests of SiGe couples, modules and MHW generators.

  14. Optimal Number of Thermoelectric Couples in a Heat Pipe Assisted Thermoelectric Generator for Waste Heat Recovery

    NASA Astrophysics Data System (ADS)

    Liu, Tongjun; Wang, Tongcai; Luan, Weiling; Cao, Qimin

    2017-05-01

    Waste heat recovery through thermoelectric generators is a promising way to improve energy conversion efficiency. This paper proposes a type of heat pipe assisted thermoelectric generator (HP-TEG) system. The expandable evaporator and condenser surface of the heat pipe facilitates the intensive assembly of thermoelectric (TE) modules to compose a compact device. Compared with a conventional layer structure thermoelectric generator, this system is feasible for the installment of more TE couples, thus increasing power output. To investigate the performance of the HP-TEG and the optimal number of TE couples, a theoretical model was presented and verified by experiment results. Further theoretical analysis results showed the performance of the HP-TEG could be further improved by optimizing the parameters, including the inlet air temperature, the thermal resistance of the heating section, and thermal resistance of the cooling structure. Moreover, applying a proper number of TE couples is important to acquire the best power output performance.

  15. Thermoelectric characterization of individual bismuth selenide topological insulator nanoribbons.

    PubMed

    Tang, Hao; Wang, Xiaomeng; Xiong, Yucheng; Zhao, Yang; Zhang, Yin; Zhang, Yan; Yang, Juekuan; Xu, Dongyan

    2015-04-21

    Bismuth selenide (Bi2Se3) nanoribbons have attracted tremendous research interest recently to study the properties of topologically protected surface states that enable new opportunities to enhance the thermoelectric performance. However, the thermoelectric characterization of individual Bi2Se3 nanoribbons is rare due to the technological challenges in the measurements. One challenge is to ensure good contacts between the nanoribbon and electrodes in order to determine the thermal and electrical properties accurately. In this work, we report the thermoelectric characterization of individual Bi2Se3 nanoribbons via a suspended microdevice method. Through careful measurements, we have demonstrated that contact thermal resistance is negligible after the electron-beam-induced deposition (EBID) of platinum/carbon (Pt/C) composites at the contacts between the nanoribbon and electrodes. It is shown that the thermal conductivity of the Bi2Se3 nanoribbons is less than 50% of the bulk value over the whole measurement temperature range, which can be attributed to enhanced phonon boundary scattering. Our results indicate that intrinsic Bi2Se3 nanoribbons prepared in this work are highly doped n-type semiconductors, and therefore the Fermi level should be in the conduction band and no topological transport behavior can be observed in the intrinsic system.

  16. High-Performance Silicon-Germanium-Based Thermoelectric Modules for Gas Exhaust Energy Scavenging

    NASA Astrophysics Data System (ADS)

    Romanjek, K.; Vesin, S.; Aixala, L.; Baffie, T.; Bernard-Granger, G.; Dufourcq, J.

    2015-06-01

    Some of the energy used in transportation and industry is lost as heat, often at high-temperatures, during conversion processes. Thermoelectricity enables direct conversion of heat into electricity, and is an alternative to the waste-heat-recovery technology currently used, for example turbines and other types of thermodynamic cycling. The performance of thermoelectric (TE) materials and modules has improved continuously in recent decades. In the high-temperature range ( T hot side > 500°C), silicon-germanium (SiGe) alloys are among the best TE materials reported in the literature. These materials are based on non-toxic elements. The Thermoelectrics Laboratory at CEA (Commissariat à l'Energie Atomique et aux Energies Alternatives) has synthesized n and p-type SiGe pellets, manufactured TE modules, and integrated these into thermoelectric generators (TEG) which were tested on a dedicated bench with hot air as the source of heat. SiGe TE samples of diameter 60 mm were created by spark-plasma sintering. For n-type SiGe doped with phosphorus the peak thermoelectric figure of merit reached ZT = 1.0 at 700°C whereas for p-type SiGe doped with boron the peak was ZT = 0.75 at 700°C. Thus, state-of-the-art conversion efficiency was obtained while also achieving higher production throughput capacity than for competing processes. A standard deviation <4% in the electrical resistance of batches of ten pellets of both types was indicative of high reproducibility. A silver-paste-based brazing technique was used to assemble the TE elements into modules. This assembly technique afforded low and repeatable electrical contact resistance (<3 nΩ m2). A test bench was developed for measuring the performance of TE modules at high temperatures (up to 600°C), and thirty 20 mm × 20 mm TE modules were produced and tested. The results revealed the performance was reproducible, with power output reaching 1.9 ± 0.2 W for a 370 degree temperature difference. When the temperature

  17. Low-Temperature Thermoelectric Properties of Fe2VAl with Partial Cobalt Doping

    NASA Astrophysics Data System (ADS)

    Liu, Chang; Morelli, Donald T.

    2012-06-01

    Ternary metallic alloy Fe2VAl with a pseudogap in its energy band structure has received intensive scrutiny for potential thermoelectric applications. Due to the sharp change in the density of states profile near the Fermi level, interesting transport properties can be triggered to render possible enhancement in the overall thermoelectric performance. Previously, this full-Heusler-type alloy was partially doped with cobalt at the iron sites to produce a series of compounds with n-type conductivity. Their thermoelectric properties in the temperature range of 300 K to 850 K were reported. In this research, efforts were made to extend the investigation on (Fe1- x Co x )2VAl to the low-temperature range. Alloy samples were prepared by arc-melting and annealing. Seebeck coefficient, electrical resistivity, and thermal conductivity measurements were performed from 80 K to room temperature. The effects of cobalt doping on the material's electronic and thermal properties are discussed.

  18. Performance Analysis of a Thermoelectric Solar Collector Integrated with a Heat Pump

    NASA Astrophysics Data System (ADS)

    Lertsatitthanakorn, C.; Jamradloedluk, J.; Rungsiyopas, M.; Therdyothin, A.; Soponronnarit, S.

    2013-07-01

    A novel heat pump system is proposed. A thermoelectric solar collector was coupled to a solar-assisted heat pump (TESC-HP) to work as an evaporator. The cooling effect of the system's refrigerant allowed the cold side of the system's thermoelectric modules to work at lower temperature, improving the conversion efficiency. The TESC-HP system mainly consisted of transparent glass, an air gap, an absorber plate that acted as a direct expansion-type collector/evaporator, an R-134a piston-type hermetic compressor, a water-cooled plate-type condenser, thermoelectric modules, and a water storage tank. Test results indicated that the TESC-HP has better coefficient of performance (COP) and conversion efficiency than the separate units. For the meteorological conditions in Mahasarakham, the COP of the TESC-HP system can reach 5.48 when the average temperature of 100 L of water is increased from 28°C to 40°C in 60 min with average ambient temperature of 32.5°C and average solar intensity of 815 W/m2, whereas the conversion efficiency of the TE power generator was around 2.03%.

  19. Thermoelectric Properties of Silicon Germanium: An Investigation of the Reduction of Lattice Thermal Conductivity and Enhancement of Power Factor

    NASA Astrophysics Data System (ADS)

    Lahwal, Ali Sadek

    Thermoelectric materials are of technological interest owing to their ability of direct thermal-to-electrical energy conversion. In thermoelectricity, thermal gradients can be used to generate an electrical power output. Recent efforts in thermoelectrics are focused on developing higher efficient power generation materials. In this dissertation, the overall goal is to investigate both the n-type and p-type of the state of the art thermoelectric material, silicon germanium (SiGe), for high temperature power generation. Further improvement of thermoelectric performance of Si-Ge alloys hinges upon how to significantly reduce the as yet large lattice thermal conductivity, and optimizing the thermoelectric power factor PF. Our methods, in this thesis, will be into two different approaches as follow: The first approach is manipulating the lattice thermal conductivity of n and p-type SiGe alloys via direct nanoparticle inclusion into the n-type SiGe matrix and, in a different process, using a core shell method for the p-type SiGe. This approach is in line with the process of in-situ nanocomposites. Nanocomposites have become a new paradigm for thermoelectric research in recent years and have resulted in the reduction of thermal conductivity via the nano-inclusion and grain boundary scattering of heat-carrying phonons. To this end, a promising choice of nano-particle to include by direct mixing into a SiGe matrix would be Yttria Stabilized Zirconia ( YSZ). In this work we report the preparation and thermoelectric study of n-type SiGe + YSZ nanocomposites prepared by direct mechanical mixing followed by Spark Plasma Sintering (SPS) processing. Specifically, we experimentally investigated the reduction of lattice thermal conductivity (kappaL) in the temperature range (30--800K) of n-type Si 80Ge20P2 alloys with the incorporation of YSZ nanoparticles (20 ˜ 40 nm diameter) into the Si-Ge matrix. These samples synthesized by SPS were found to have densities > 95% of the

  20. Thermoelectric pump performance analysis computer code

    NASA Technical Reports Server (NTRS)

    Johnson, J. L.

    1973-01-01

    A computer program is presented that was used to analyze and design dual-throat electromagnetic dc conduction pumps for the 5-kwe ZrH reactor thermoelectric system. In addition to a listing of the code and corresponding identification of symbols, the bases for this analytical model are provided.

  1. Study of thermal stability of Cu{sub 2}Se thermoelectric material

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Bohra, Anil, E-mail: anilbohra786@gmail.com; Bhatt, Ranu; Bhattacharya, Shovit

    2016-05-23

    Sustainability of thermoelectric parameter in operating temperature range is a key consideration factor for fabricating thermoelectric generator or cooler. In present work, we have studied the stability of thermoelectric parameter of Cu{sub 2}Se within the temperature range of 50-800°C. Temperature dependent Seebeck coefficients and electrical resistivity measurement are performed under three continuous thermal cycles. X-ray diffraction pattern shows the presence of mixed cubic-monoclinic Cu{sub 2}Se phase in bare pellet which transforms to pure α-Cu{sub 2}Se phase with repeating thermal cycle. Significant enhancement in Seebeck coefficient and electrical resistivity is observed which may be attributed to (i) Se loss observed inmore » EDS and (ii) the phase transformation from mixed cubic-monoclinic structure to pure monoclinic α-Cu{sub 2}Se phase.« less

  2. Recent progress in half-Heusler thermoelectric materials

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Huang, Lihong; Zhang, Qinyong; Yuan, Bo

    2016-04-15

    Highlights: • Summarize the recent progress and advances in HH thermoelectric materials. • Preparing nanocomposites could reduce thermal conductivity. • Introducing enhance phonon scattering could further reduce the thermal conductivity. • Forming ternary systems to reducing the cost effectively. • The new class of HHs presents another opportunity to further optimize the HH system. - Abstract: Half-Heusler (HH) thermoelectric (TE) materials have been attracting extensive research interest over the last two decades, owing to their thermal stability, mechanical strength, and moderate ZT. This material system are potential candidates for medium to high temperature applications, which is close to the temperaturemore » range of most industrial waste heat sources. In this mini-review article, we briefly summarize the recent progress and advances in HH thermoelectric materials. Some effectively available approaches, such as HH nanocomposites to reduce thermal conductivity, using larger atomic mass and size differences to enhance phonon scattering to further reduce the thermal conductivity, forming ternary systems following the cost effective approach. In addition, new thermoelectric HH members are also discussed in this article, which points out that many new HH compounds may be possible for TE applications.« less

  3. Thermoelectric converter

    DOEpatents

    Kim, C.K.

    1974-02-26

    This invention relates in general to thermoelectric units and more particularly to a tubular thermoelectric unit which includes an array of tandemly arranged radially tapered annular thermoelectric pellets having insulation material of a lower density than the thermoelectric pellets positioned between each pellet. (Official Gazette)

  4. Highly Efficient Multilayer Thermoelectric Devices

    NASA Technical Reports Server (NTRS)

    Boufelfel, Ali

    2006-01-01

    Multilayer thermoelectric devices now at the prototype stage of development exhibit a combination of desirable characteristics, including high figures of merit and high performance/cost ratios. These devices are capable of producing temperature differences of the order of 50 K in operation at or near room temperature. A solvent-free batch process for mass production of these state-of-the-art thermoelectric devices has also been developed. Like prior thermoelectric devices, the present ones have commercial potential mainly by virtue of their utility as means of controlled cooling (and/or, in some cases, heating) of sensors, integrated circuits, and temperature-critical components of scientific instruments. The advantages of thermoelectric devices for such uses include no need for circulating working fluids through or within the devices, generation of little if any noise, and high reliability. The disadvantages of prior thermoelectric devices include high power consumption and relatively low coefficients of performance. The present development program was undertaken in the hope of reducing the magnitudes of the aforementioned disadvantages and, especially, obtaining higher figures of merit for operation at and near room temperature. Accomplishments of the program thus far include development of an algorithm to estimate the heat extracted by, and the maximum temperature drop produced by, a thermoelectric device; solution of the problem of exchange of heat between a thermoelectric cooler and a water-cooled copper block; retrofitting of a vacuum chamber for depositing materials by sputtering; design of masks; and fabrication of multilayer thermoelectric devices of two different designs, denoted I and II. For both the I and II designs, the thicknesses of layers are of the order of nanometers. In devices of design I, nonconsecutive semiconductor layers are electrically connected in series. Devices of design II contain superlattices comprising alternating electron

  5. Thermoelectric properties of a trilayer graphene nanoribbon

    NASA Astrophysics Data System (ADS)

    Orellana, Pedro; Cortes, Natalia; Rosales, Luis; Pacheco, Monica; Chico, Leonor

    2015-03-01

    In this work the electronic and thermoelectric properties of a three-layer graphene with AAA stacking type are studied. By using a tight-binding model analytical expressions for the transmission and density of states are obtained. Thermoelectric properties are analyzed by numerical integration and results for thermopower and figure of merit, electronic conductance and thermal conductance are obtained. The results show that the interference effects present in this system, like Fano effect, directly affect the behavior of these thermoelectric properties and as well as the Wiedemann-Franz law. There is an enhancement of the thermopower of the system and a violation of the Wiedemann-Franz law in the region of energies close the Fano antiresonances and this has as a consequence an enhancement of the figure of merit of the system. FONDECYT 1140571, 1140388, CONICYT ACT 1204, DGIP/ USM internal Grant 11.14.68.

  6. Numerical and Experimental Investigation on the Performance of a Thermoelectric Cooling Automotive Seat

    NASA Astrophysics Data System (ADS)

    Su, Chuqi; Dong, Wenbin; Deng, Yadong; Wang, Yiping; Liu, Xun

    2017-11-01

    Heating, ventilating and air conditioning (HVAC) is the most significant auxiliary load in vehicles and largely increases extra emissions. Therefore, thermoelectric cooling automotive seat, a relatively new technology, is used in an attempt to reduce HVAC consumption and improve thermal comfort. In this study, three design schemes of the thermoelectric cooler (TEC) are proposed. Then the numerical simulation is used to analyze their heat transfer performance, and evaluate the improvement of the seat cooling in terms of the occupant back thermal comfort. Moreover, an experiment is conducted to validate the accuracy of the simulation results. The experimental results show that: (1) an average reduction in air temperature of 4°C in 60 s is obtained; (2) the temperature of the occupant's back drops from 33.5°C to 25.7°C in cooperation with the HVAC system; (3) back thermal comfort is greatly improved. As expected, the thermoelectric cooling automotive seat is able to provide an improvement in the occupant's thermal comfort at a reduced energy consumption rate, which makes it promising for vehicular application.

  7. Numerical and Experimental Investigation on the Performance of a Thermoelectric Cooling Automotive Seat

    NASA Astrophysics Data System (ADS)

    Su, Chuqi; Dong, Wenbin; Deng, Yadong; Wang, Yiping; Liu, Xun

    2018-06-01

    Heating, ventilating and air conditioning (HVAC) is the most significant auxiliary load in vehicles and largely increases extra emissions. Therefore, thermoelectric cooling automotive seat, a relatively new technology, is used in an attempt to reduce HVAC consumption and improve thermal comfort. In this study, three design schemes of the thermoelectric cooler (TEC) are proposed. Then the numerical simulation is used to analyze their heat transfer performance, and evaluate the improvement of the seat cooling in terms of the occupant back thermal comfort. Moreover, an experiment is conducted to validate the accuracy of the simulation results. The experimental results show that: (1) an average reduction in air temperature of 4°C in 60 s is obtained; (2) the temperature of the occupant's back drops from 33.5°C to 25.7°C in cooperation with the HVAC system; (3) back thermal comfort is greatly improved. As expected, the thermoelectric cooling automotive seat is able to provide an improvement in the occupant's thermal comfort at a reduced energy consumption rate, which makes it promising for vehicular application.

  8. Universal Majorana thermoelectric noise

    NASA Astrophysics Data System (ADS)

    Smirnov, Sergey

    2018-04-01

    Thermoelectric phenomena resulting from an interplay between particle flows induced by electric fields and temperature inhomogeneities are extremely insightful as a tool providing substantial knowledge about the microscopic structure of a given system. By tuning, e.g., parameters of a nanoscopic system coupled via tunneling mechanisms to two contacts, one may achieve various situations where the electric current induced by an external bias voltage competes with the electric current excited by the temperature difference of the two contacts. Even more exciting physics emerges when the system's electronic degrees freedom split to form Majorana fermions which make the thermoelectric dynamics universal. Here, we propose revealing these unique universal signatures of Majorana fermions in strongly nonequilibrium quantum dots via noise of the thermoelectric transport beyond linear response. It is demonstrated that whereas mean thermoelectric quantities are only universal at large-bias voltages, the noise of the electric current excited by an external bias voltage and the temperature difference of the contacts is universal at any bias voltage. We provide truly universal, i.e., independent of the system's parameters, thermoelectric ratios between nonlinear response coefficients of the noise and mean current at large-bias voltages where experiments may easily be performed to uniquely detect these truly universal Majorana thermoelectric signatures.

  9. Optimization of thermoelectric performance of SrSi2-based alloys via the modification in band structure and phonon-point-defect scattering

    PubMed Central

    Kuo, Yung-Kang; Ramachandran, Balakrishnan; Lue, Chin-Shan

    2014-01-01

    Thermoelectric properties of alkaline-earth-metal disilicides are strongly dependent on their electronic band structure in the vicinity of the Fermi level. In particular, the strontium disilicide, SrSi2 with a narrow band gap of about few tens of meV is composed of non-toxic, naturally abundant elements, and its thermoelectric properties are very sensitive to the substitution/alloying with third elements. In this article, we summarize the thermoelectric performance of substituted and Sr-deficient/Sr-rich SrSi2 alloys to realize the high thermoelectric figure-of-merit (ZT) for practical applications in the electronic and thermoelectric aspects, and also to explore the alternative routes to further improve its ZT value. PMID:25505784

  10. Thermionic Energy Conversion (TEC) topping thermoelectrics

    NASA Technical Reports Server (NTRS)

    Morris, J. F.

    1981-01-01

    Performance expectations for thermionic and thermoelectric energy conversion systems are reviewed. It is noted that internal radiation effects diminish thermoelectric figures of merit significantly at 1000 K and substantially at 2000 K; the effective thermal conductivity contribution of intrathermoelectric radiative dissipation increases with the third power of temperature. It is argued that a consideration of thermoelectric power generation with high temperature heat sources should include utilization of thermionic energy conversion (TEC) topping thermoelectrics. However TEC alone or TEC topping more efficient conversion systems like steam or gas turbines, combined cycles, or Stirling engines would be more desirable generally.

  11. Design, crystal growth, and physical properties of low-temperature thermoelectric materials

    NASA Astrophysics Data System (ADS)

    Fuccillo, Michael K.

    Thermoelectric materials serve as the foundation for two important modern technologies, namely 1) solid-state cooling, which enables small-area refrigeration without vibrations or moving parts, and 2) thermoelectric power generation, which has important implications for waste heat recovery and improved sources of alternative energy. Although the overall field of thermoelectrics research has been active for decades, and several consumer and industrial products have already been commercialized, the design and synthesis of new thermoelectrics that outperform long-standing state of the art materials has proven extremely challenging. This is particularly true for low-temperature refrigeration applications, which is the focus of this work; however, scientific advances in this area generally support power generation as well. In order to achieve more efficient materials for virtually all thermoelectric applications, improved materials design principles must be developed and synthetic procedures must be better understood. We aim to contribute to these goals by studying two classes of materials, namely 1) the tetradymites Bi2TeSe 2 and Bi2Te2Se, which are close relatives of state of the art thermoelectric cooling materials, and 2) Kondo insulating (-like) FeSb2 and FeSi, which possess anomalously enhanced low-temperature thermoelectric properties that arise from exotic electronic and magnetic properties. The organization of this dissertation is as follows: Chapter 1 is a brief perspective on solid-state chemistry. Chapter 2 presents experimental methods for synthesizing and characterizing thermoelectric materials. In Chapter 3, two original research projects are discussed: first, work on the tetradymite Bi2TeSe2 doped with Sb to achieve an n- to p-type transition, and second, the tetradymite Bi2Te2Se with chemical defects through two different methods. Chapter 4 gives the magnetic and transport properties of FeSb 2--RuSb2 alloys, a family of compounds exemplifying what we

  12. Origin of high thermoelectric performance of FeNb1−xZr/HfxSb1−ySny alloys: A first-principles study

    PubMed Central

    Zhang, Xiwen; Wang, Yuanxu; Yan, Yuli; Wang, Chao; Zhang, Guangbiao; Cheng, Zhenxiang; Ren, Fengzhu; Deng, Hao; Zhang, Jihua

    2016-01-01

    The previous experimental work showed that Hf- or Zr-doping has remarkably improved the thermoelectric performance of FeNbSb. Here, the first-principles method was used to explore the possible reason for such phenomenon. The substitution of X (Zr/Hf) atoms at Nb sites increases effective hole-pockets, total density of states near the Fermi level (EF), and hole mobility to largely enhance electrical conductivity. It is mainly due to the shifting the EF to lower energy and the nearest Fe atoms around X atoms supplying more d-states to hybrid with X d-states at the vicinity of the EF. Moreover, we find that the X atoms indirectly affect the charge distribution around Nb atoms via their nearest Fe atoms, resulting in the reduced energy difference in the valence band edge, contributing to enhanced Seebeck coefficients. In addition, the further Bader charge analysis shows that the reason of more holes by Hf-doping than Zr in the experiment is most likely derived from Hf atoms losing less electrons and the stronger hybridization between Hf atoms and their nearest Fe atoms. Furthermore, we predict that Hf/Sn co-doping may be an effective strategy to further optimize the thermoelectric performance of half-Heusler (HH) compounds. PMID:27604826

  13. Estimation of Thermoelectric Generator Performance by Finite Element Modeling

    NASA Astrophysics Data System (ADS)

    Ziolkowski, P.; Poinas, P.; Leszczynski, J.; Karpinski, G.; Müller, E.

    2010-09-01

    Prediction of thermoelectric performance parameters by numerical methods is an inherent part of thermoelectric generator (TEG) development and allows for time- and cost-saving assessment of material combinations and variations of crucial design parameters (e.g., shape, pellet length, and thermal coupling). Considering the complexity of a TEG system and its numerous affecting factors, the clarity and the flexibility of a mathematical treatment comes to the fore. Comfortable tools are provided by commercial finite element modeling (FEM) software offering powerful geometry interfaces, mesh generators, solvers, and postprocessing options. We describe the level of development and the simulation results of a three dimensional (3D) TEG FEM. Using ANSYS 11.0, we implemented and simulated a TEG module geometry under various conditions. Comparative analytical one dimensional (1D) results and a direct comparison with inhouse-developed TEG simulation software show the consistency of results. Several pellet aspect ratios and contact property configurations (thermal/electrical interface resistance) were evaluated for their impact on the TEG performance as well as parasitic effects such as convection, radiation, and conductive heat bypass. The scenarios considered revealed the highest efficiency decay for convectionally loaded setups (up to 4.8%pts), followed by the impacts of contact resistances (up to 4.8%pts), by radiation (up to 0.56%pts), and by thermal conduction of a solid filling material within the voids of the module construction (up to 0.14%pts).

  14. PERFORMANCE TESTS OF SNAP 10A THERMOELECTRIC ELEMENTS

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Bergdorf, C.G.

    1961-08-30

    Apparatus for the performanee testing of SNAP 10A thermoelectric elements was designed, constructed, and is now in operation. Elements may be tested for any desired length of tfme up to 1400 deg F and in a vacuum of 1 x 10/ sup -5/ of Hg. The equipment used for these tcsts may also be utilized for measuring Seebeck coefficient and resistance as a function of temperature. Element performance is derived from the data on voltages and temperatures. The performance variables which are reported in graphic form are as follows: loaded output voltage at any desired DELTA T; open circuit outputmore » voltage at any desired DELTA T; power output under optimum load conditions; current produced under matched load conditions; and internal resistance of the element. (auth)« less

  15. A study of hear sink performance in air and soil for use in a thermoelectric energy harvesting device

    NASA Technical Reports Server (NTRS)

    Snyder, J.; Lawrence, E. E.

    2002-01-01

    A suggested application of a thermoelectric generator is to exploit the natural temperature difference between the air and the soil to generate small amounts of electrical energy. Since the conversion efficiency of even the best thermoelectric generators available is very low, the performance of the heat sinks providing the heat flow is critical. By providing a constant heat input to various heat sinks, field tests of their thermal conductances in soil and in air were performed. Aprototype device without a thermoelectric generator was constructed, buried, and monitored to experimentally measure the heat flow achievable in such a system. Theoretical considerations for design and selection of improved heat sinks are also presented. In particular, the method of shape factoranalysis is used to give rough estimates and upper bounds for the thermal conductance of a passive heat sink buried in soil.

  16. Heat Management in Thermoelectric Power Generators

    PubMed Central

    Zebarjadi, M.

    2016-01-01

    Thermoelectric power generators are used to convert heat into electricity. Like any other heat engine, the performance of a thermoelectric generator increases as the temperature difference on the sides increases. It is generally assumed that as more heat is forced through the thermoelectric legs, their performance increases. Therefore, insulations are typically used to minimize the heat losses and to confine the heat transport through the thermoelectric legs. In this paper we show that to some extend it is beneficial to purposely open heat loss channels in order to establish a larger temperature gradient and therefore to increase the overall efficiency and achieve larger electric power output. We define a modified Biot number (Bi) as an indicator of requirements for sidewall insulation. We show cooling from sidewalls increases the efficiency for Bi values less than one, and decreases the efficiency for Bi values larger than one. PMID:27033717

  17. Systems and methods for the synthesis of high thermoelectric performance doped-SnTe materials

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ren, Zhifeng; Zhang, Qian; Chen, Gang

    A thermoelectric composition comprising tin (Sn), tellurium (Te) and at least one dopant that comprises a peak dimensionless figure of merit (ZT) of 1.1 and a Seebeck coefficient of at least 50 .mu.V/K and a method of manufacturing the thermoelectric composition. A plurality of components are disposed in a ball-milling vessel, wherein the plurality of components comprise tin (Sn), tellurium (Te), and at least one dopant such as indium (In). The components are subsequently mechanically and thermally processed, for example, by hot-pressing. In response to the mechanical-thermally processing, a thermoelectric composition is formed, wherein the thermoelectric composition comprises a dimensionlessmore » figure of merit (ZT) of the thermoelectric composition is at least 0.8, and wherein a Seebeck coefficient of the thermoelectric composition is at least 50 .mu.V/K at any temperature.« less

  18. Simulations for the Development of Thermoelectric Measurements

    NASA Astrophysics Data System (ADS)

    Zabrocki, Knud; Ziolkowski, Pawel; Dasgupta, Titas; de Boor, Johannes; Müller, Eckhard

    2013-07-01

    In thermoelectricity, continuum theoretical equations are usually used for the calculation of the characteristics and performance of thermoelectric elements, modules or devices as a function of external parameters (material, geometry, temperatures, current, flow, load, etc.). An increasing number of commercial software packages aimed at applications, such as COMSOL and ANSYS, contain vkernels using direct thermoelectric coupling. Application of these numerical tools also allows analysis of physical measurement conditions and can lead to specifically adapted methods for developing special test equipment required for the determination of TE material and module properties. System-theoretical and simulation-based considerations of favorable geometries are taken into account to create draft sketches in the development of such measurement systems. Particular consideration is given to the development of transient measurement methods, which have great advantages compared with the conventional static methods in terms of the measurement duration required. In this paper the benefits of using numerical tools in designing measurement facilities are shown using two examples. The first is the determination of geometric correction factors in four-point probe measurement of electrical conductivity, whereas the second example is focused on the so-called combined thermoelectric measurement (CTEM) system, where all thermoelectric material properties (Seebeck coefficient, electrical and thermal conductivity, and Harman measurement of zT) are measured in a combined way. Here, we want to highlight especially the measurement of thermal conductivity in a transient mode. Factors influencing the measurement results such as coupling to the environment due to radiation, heat losses via the mounting of the probe head, as well as contact resistance between the sample and sample holder are illustrated, analyzed, and discussed. By employing the results of the simulations, we have developed an

  19. Investigation of the photovoltaic cell/ thermoelectric element hybrid system performance

    NASA Astrophysics Data System (ADS)

    Cotfas, D. T.; Cotfas, P. A.; Machidon, O. M.; Ciobanu, D.

    2016-06-01

    The PV/TEG hybrid system, consisting of the photovoltaic cells and thermoelectric element, is presented in the paper. The dependence of the PV/TEG hybrid system parameters on the illumination levels and the temperature is analysed. The maxim power values of the photovoltaic cell, of the thermoelectric element and of the PV/TEG system are calculated and a comparison between them is presented and analysed. An economic analysis is also presented.

  20. Enhanced stability and thermoelectric figure-of-merit in copper selenide by lithium doping

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kang, Stephen Dongmin; Pöhls, Jan-Hendrik; Aydemir, Umut

    Superionic thermoelectric materials have been shown to have high figure-of-merits, leading to expectations for efficient high-temperature thermoelectric generators. These compounds exhibit extremely high cation diffusivity, comparable to that of a liquid, which is believed to be associated with the low thermal conductivity that makes superionic materials good for thermoelectrics. However, the superionic behavior causes cation migration that leads to device deterioration, being the main obstacle for practical applications. It has been reported that lithium doping in superionic Cu2-xSe leads to suppression of the Cu ion diffusivity, but whether the material will retain the promising thermoelectric properties had not yet beenmore » investigated. Here, we report a maximum zT>1.4 from Li0.09Cu1.9Se, which is higher than what we find in the undoped samples. The high temperature effective weighted mobility of the doped sample is found higher than Cu2-xSe, while the lattice thermal conductivity remains similar. We find signatures of suppressed bipolar conduction due to an enlarged band gap. Our findings set forth a possible route for tuning the stability of superionic thermoelectric materials.« less

  1. Enhanced Thermoelectric Properties of Cu 2ZnSnSe 4 with Ga-doping

    DOE PAGES

    Wei, Kaya; Beauchemin, Laura; Wang, Hsin; ...

    2015-08-10

    Gallium doped Cu 2ZnSnSe 4 quaternary chalcogenides with and without excess Cu were synthesized by elemental reaction and densified using hot pressing in order to investigate their high temperature thermoelectric properties. The resistivity, , and Seebeck coefficient, S, for these materials decrease with increased Ga-doping while both mobility and effective mass increase with Ga doping. The power factor (S 2/ρ) therefore increases with Ga-doping. The highest thermoelectric figure of merit (ZT = 0.39 at 700 K) was obtained for the composition that had the lowest thermal conductivity. Our results suggest an approach to achieving optimized thermoelectric properties and are partmore » of the continuing effort to explore different quaternary chalcogenide compositions and structure types, as this class of materials continues to be of interest for thermoelectrics applications.« less

  2. Effect of Thermoelectric Cooling (TEC) module and the water flow heatsink on Photovoltaic (PV) panel performance

    NASA Astrophysics Data System (ADS)

    Amelia, A. R.; Jusoh, MA; Shamira Idris, Ida

    2017-11-01

    Photovoltaic (PV) panel suffers in low conversion efficiency of the output performance affected by the elevated operating temperature of the PV panel. It is important to keep the PV panel to operate at low temperature. To address this issue, this paper proposes the cooling system using thermoelectric cooling (TEC) and water block heatsink for enhancing the PV panel output performance. These both types cooling system were designed located on the back side of the PV panel to cool down the operating temperature of the PV panel. To evaluate the function for the existing cooling systems, the experiment was subsequently performed for PV panel without and with different design of the cooling system in outdoor weather conditions. By comparing the experimental results, it is concluded that by the hybrid cooling system which combining TEC module and the water block heatsink could improve the output performance of the PV panel. By the reduction temperature of the PV panel by 16.04 %, the average output power of the PV panel has been boosted up from 8.59 W to 9.03 W. In short, the output power of the PV panel was enhanced by the reduction of the operating temperature of the PV panel.

  3. Taguchi optimization of bismuth-telluride based thermoelectric cooler

    NASA Astrophysics Data System (ADS)

    Anant Kishore, Ravi; Kumar, Prashant; Sanghadasa, Mohan; Priya, Shashank

    2017-07-01

    In the last few decades, considerable effort has been made to enhance the figure-of-merit (ZT) of thermoelectric (TE) materials. However, the performance of commercial TE devices still remains low due to the fact that the module figure-of-merit not only depends on the material ZT, but also on the operating conditions and configuration of TE modules. This study takes into account comprehensive set of parameters to conduct the numerical performance analysis of the thermoelectric cooler (TEC) using a Taguchi optimization method. The Taguchi method is a statistical tool that predicts the optimal performance with a far less number of experimental runs than the conventional experimental techniques. Taguchi results are also compared with the optimized parameters obtained by a full factorial optimization method, which reveals that the Taguchi method provides optimum or near-optimum TEC configuration using only 25 experiments against 3125 experiments needed by the conventional optimization method. This study also shows that the environmental factors such as ambient temperature and cooling coefficient do not significantly affect the optimum geometry and optimum operating temperature of TECs. The optimum TEC configuration for simultaneous optimization of cooling capacity and coefficient of performance is also provided.

  4. Band structure modification of the thermoelectric Heusler-phase TiFe2Sn via Mn substitution.

    PubMed

    Zou, Tianhua; Jia, Tiantian; Xie, Wenjie; Zhang, Yongsheng; Widenmeyer, Marc; Xiao, Xingxing; Weidenkaff, Anke

    2017-07-19

    Doping (or substitution)-induced modification of the electronic structure to increase the electronic density of states (eDOS) near the Fermi level is considered as an effective strategy to enhance the Seebeck coefficient, and may consequently boost the thermoelectric performance. Through density-functional theory calculations of Mn-substituted TiFe 2-x Mn x Sn compounds, we demonstrate that the d-states of the substituted Mn atoms induce a strong resonant level near the Fermi energy. Our experimental results are in good agreement with the calculations. They show that Mn substitution results in a large increase of the Seebeck coefficient, arising from an enhanced eDOS in Heusler compounds. The results prove that a proper substitution position and element selection can increase the eDOS, leading to a higher Seebeck coefficient and thermoelectric performance of ecofriendly materials.

  5. Effect of potassium doping on electronic structure and thermoelectric properties of topological crystalline insulator

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Roychowdhury, Subhajit; Biswas, Kanishka, E-mail: kanishka@jncasr.ac.in; Sandhya Shenoy, U.

    2016-05-09

    Topological crystalline insulator (TCI), Pb{sub 0.6}Sn{sub 0.4}Te, exhibits metallic surface states protected by crystal mirror symmetry with negligibly small band gap. Enhancement of its thermoelectric performances needs tuning of its electronic structure particularly through engineering of its band gap. While physical perturbations tune the electronic structure of TCI by breaking of the crystal mirror symmetry, chemical means such as doping have been more attractive recently as they result in better thermoelectric performance in TCIs. Here, we demonstrate that K doping in TCI, Pb{sub 0.6}Sn{sub 0.4}Te, breaks the crystal mirror symmetry locally and widens electronic band gap, which is confirmed bymore » direct electronic absorption spectroscopy and electronic structure calculations. K doping in Pb{sub 0.6}Sn{sub 0.4}Te increases p-type carrier concentration and suppresses the bipolar conduction via widening a band gap, which collectively boosts the thermoelectric figure of merit (ZT) to 1 at 708 K.« less

  6. Thermoelectric Properties of Complex Oxide Heterostructures

    NASA Astrophysics Data System (ADS)

    Cain, Tyler Andrew

    Thermoelectrics are a promising energy conversion technology for power generation and cooling systems. The thermal and electrical properties of the materials at the heart of thermoelectric devices dictate conversion efficiency and technological viability. Studying the fundamental properties of potentially new thermoelectric materials is of great importance for improving device performance and understanding the electronic structure of materials systems. In this dissertation, investigations on the thermoelectric properties of a prototypical complex oxide, SrTiO3, are discussed. Hybrid molecular beam epitaxy (MBE) is used to synthesize La-doped SrTiO3 thin films, which exhibit high electron mobilities and large Seebeck coefficients resulting in large thermoelectric power factors at low temperatures. Large interfacial electron densities have been observed in SrTiO3/RTiO 3 (R=Gd,Sm) heterostructures. The thermoelectric properties of such heterostructures are investigated, including the use of a modulation doping approach to control interfacial electron densities. Low-temperature Seebeck coefficients of extreme electron-density SrTiO3 quantum wells are shown to provide insight into their electronic structure.

  7. Near-field three-terminal thermoelectric heat engine

    NASA Astrophysics Data System (ADS)

    Jiang, Jian-Hua; Imry, Yoseph

    2018-03-01

    We propose a near-field inelastic thermoelectric heat engine where quantum dots are used to effectively rectify the charge flow of photocarriers. The device converts near-field heat radiation into useful electrical power. Heat absorption and inelastic transport can be enhanced by introducing two continuous spectra separated by an energy gap. The thermoelectric transport properties of the heat engine are studied in the linear-response regime. Using a small band-gap semiconductor as the absorption material, we show that the device achieves very large thermopower and thermoelectric figure of merit, as well as considerable power factor. By analyzing thermal-photocarrier generation and conduction, we reveal that the Seebeck coefficient and the figure of merit have oscillatory dependence on the thickness of the vacuum gap. Meanwhile, the power factor, the charge, and thermal conductivity are significantly improved by near-field radiation. Conditions and guiding principles for powerful and efficient thermoelectric heat engines are discussed in details.

  8. Promising thermoelectric properties of phosphorenes.

    PubMed

    Sevik, Cem; Sevinçli, Hâldun

    2016-09-02

    Electronic, phononic, and thermoelectric transport properties of single layer black- and blue-phosphorene structures are investigated with first-principles based ballistic electron and phonon transport calculations employing hybrid functionals. The maximum values of room temperature thermoelectric figure of merit, ZT corresponding to armchair and zigzag directions of black-phosphorene, ∼0.5 and ∼0.25, are calculated as rather smaller than those obtained with first-principles based semiclassical Boltzmann transport theory calculations. On the other hand, the maximum value of room temperature ZT of blue-phosphorene is predicted to be substantially high and remarkable values as high as 2.5 are obtained for elevated temperatures. Besides the fact that these figures are obtained at the ballistic limit, our findings mark the strong possibility of high thermoelectric performance of blue-phosphorene in new generation thermoelectric applications.

  9. Mo(3)Sb(7-x)Te(x) for Thermoelectric Power Generation

    NASA Technical Reports Server (NTRS)

    Snyder, G. Jeffrey; Gascoin, Frank S.; Rasmussen, Julia

    2009-01-01

    Compounds having compositions of Mo(3)Sb(7-x)Te(x) (where x = 1.5 or 1.6) have been investigated as candidate thermoelectric materials. These compounds are members of a class of semiconductors that includes previously known thermoelectric materials. All of these compounds have complex crystalline and electronic structures. Through selection of chemical compositions and processing conditions, it may be possible to alter the structures to enhance or optimize thermoelectric properties.

  10. Classification of Valleytronics in Thermoelectricity

    PubMed Central

    Norouzzadeh, Payam; Vashaee, Daryoosh

    2016-01-01

    The theory of valleytronics as a material design tool for engineering both thermal and electrical transport properties is presented. It is shown that the interplay among the valleytronics parameters such as the degeneracy of the band, intervalley transitions, effective mass, scattering exponent, and the Fermi energy may deteriorate or ameliorate any or all of the main thermoelectric properties. A flowchart classifying the different paths through which the valleytronics can influence the thermoelectric figure-of-merit ZT is derived and discussed in detail. To exemplify the application of the flowchart, valleytronics in four different semiconductors, Mg2Si, Si0.8Ge0.2, AlxGa1−xAs and clathrate Si46-VIII were studied, which showed different trends. Therefore, a degenerate multivalley bandstructure, which is typically anticipated for a good thermoelectric material, cannot be a general design rule for ZT enhancement and a detailed transport study is required to engineer the optimum bandstructure. PMID:26972331

  11. Atomically thick bismuth selenide freestanding single layers achieving enhanced thermoelectric energy harvesting.

    PubMed

    Sun, Yongfu; Cheng, Hao; Gao, Shan; Liu, Qinghua; Sun, Zhihu; Xiao, Chong; Wu, Changzheng; Wei, Shiqiang; Xie, Yi

    2012-12-19

    Thermoelectric materials can realize significant energy savings by generating electricity from untapped waste heat. However, the coupling of the thermoelectric parameters unfortunately limits their efficiency and practical applications. Here, a single-layer-based (SLB) composite fabricated from atomically thick single layers was proposed to optimize the thermoelectric parameters fully. Freestanding five-atom-thick Bi(2)Se(3) single layers were first synthesized via a scalable interaction/exfoliation strategy. As revealed by X-ray absorption fine structure spectroscopy and first-principles calculations, surface distortion gives them excellent structural stability and a much increased density of states, resulting in a 2-fold higher electrical conductivity relative to the bulk material. Also, the surface disorder and numerous interfaces in the Bi(2)Se(3) SLB composite allow for effective phonon scattering and decreased thermal conductivity, while the 2D electron gas and energy filtering effect increase the Seebeck coefficient, resulting in an 8-fold higher figure of merit (ZT) relative to the bulk material. This work develops a facile strategy for synthesizing atomically thick single layers and demonstrates their superior ability to optimize the thermoelectric energy harvesting.

  12. Investigation of doped Perovskite systems RAIO3 using density functional theory based electronic structure and thermoelectric studies

    NASA Astrophysics Data System (ADS)

    Sandeep; Rai, D. P.; Shankar, A.; Ghimire, M. P.; Thapa, R. K.

    2016-10-01

    Samarium doping effects on the thermoelectric properties in Eu1-xSmxAlO3 (x=0%, 50%, and 100%) were studied using first principles calculations based thermal transport property measurement. The result indicate that the compound is an intrinsic n-type material. Samarium doping has a positive effect on the overall thermoelectric performance of the Eu1-xSmxAlO3 system, with sharp increase in figure of merit (ZT) observed when x=0, 50 and 100% up to 150K. Compared to x=0 and 100%, the case of x=50% was found to have more positive increment in ZT value suggesting that the doing to have positive effect on figure of merit in Eu1-xSmxAlO3. Furthermore, all the samples show stable thermoelectric compatibility factors over a broad temperature range from 700 to 1000 K, which could have great benefits for their practical applications. It is concluded that the overall thermoelectric performance of the Eu1-xSmxAlO3 could be highly enhanced using doping techniques.

  13. High-performance flat-panel solar thermoelectric generators with high thermal concentration.

    PubMed

    Kraemer, Daniel; Poudel, Bed; Feng, Hsien-Ping; Caylor, J Christopher; Yu, Bo; Yan, Xiao; Ma, Yi; Wang, Xiaowei; Wang, Dezhi; Muto, Andrew; McEnaney, Kenneth; Chiesa, Matteo; Ren, Zhifeng; Chen, Gang

    2011-05-01

    The conversion of sunlight into electricity has been dominated by photovoltaic and solar thermal power generation. Photovoltaic cells are deployed widely, mostly as flat panels, whereas solar thermal electricity generation relying on optical concentrators and mechanical heat engines is only seen in large-scale power plants. Here we demonstrate a promising flat-panel solar thermal to electric power conversion technology based on the Seebeck effect and high thermal concentration, thus enabling wider applications. The developed solar thermoelectric generators (STEGs) achieved a peak efficiency of 4.6% under AM1.5G (1 kW m(-2)) conditions. The efficiency is 7-8 times higher than the previously reported best value for a flat-panel STEG, and is enabled by the use of high-performance nanostructured thermoelectric materials and spectrally-selective solar absorbers in an innovative design that exploits high thermal concentration in an evacuated environment. Our work opens up a promising new approach which has the potential to achieve cost-effective conversion of solar energy into electricity. © 2011 Macmillan Publishers Limited. All rights reserved

  14. High-performance flat-panel solar thermoelectric generators with high thermal concentration

    NASA Astrophysics Data System (ADS)

    Kraemer, Daniel; Poudel, Bed; Feng, Hsien-Ping; Caylor, J. Christopher; Yu, Bo; Yan, Xiao; Ma, Yi; Wang, Xiaowei; Wang, Dezhi; Muto, Andrew; McEnaney, Kenneth; Chiesa, Matteo; Ren, Zhifeng; Chen, Gang

    2011-07-01

    The conversion of sunlight into electricity has been dominated by photovoltaic and solar thermal power generation. Photovoltaic cells are deployed widely, mostly as flat panels, whereas solar thermal electricity generation relying on optical concentrators and mechanical heat engines is only seen in large-scale power plants. Here we demonstrate a promising flat-panel solar thermal to electric power conversion technology based on the Seebeck effect and high thermal concentration, thus enabling wider applications. The developed solar thermoelectric generators (STEGs) achieved a peak efficiency of 4.6% under AM1.5G (1 kW m-2) conditions. The efficiency is 7-8 times higher than the previously reported best value for a flat-panel STEG, and is enabled by the use of high-performance nanostructured thermoelectric materials and spectrally-selective solar absorbers in an innovative design that exploits high thermal concentration in an evacuated environment. Our work opens up a promising new approach which has the potential to achieve cost-effective conversion of solar energy into electricity.

  15. Superionic phase transition in silver chalcogenide nanocrystals realizing optimized thermoelectric performance.

    PubMed

    Xiao, Chong; Xu, Jie; Li, Kun; Feng, Jun; Yang, Jinlong; Xie, Yi

    2012-03-07

    Thermoelectric has long been recognized as a potentially transformative energy conversion technology due to its ability to convert heat directly into electricity. However, how to optimize the three interdependent thermoelectric parameters (i.e., electrical conductivity σ, Seebeck coefficient S, and thermal conductivity κ) for improving thermoelectric properties is still challenging. Here, we put forward for the first time the semiconductor-superionic conductor phase transition as a new and effective way to selectively optimize the thermoelectric power factor based on the modulation of the electric transport property across the phase transition. Ultra low value of thermal conductivity was successfully retained over the whole investigated temperature range through the reduction of grain size. As a result, taking monodisperse Ag(2)Se nanocrystals for an example, the maximized ZT value can be achieved around the temperature of phase transition. Furthermore, along with the effective scattering of short-wavelength phonons by atomic defects created by alloying, the alloyed ternary silver chalcogenide compounds, monodisperse Ag(4)SeS nanocrystals, show better ZT value around phase transition temperature, which is cooperatively contributed by superionic phase transition and alloying at nanoscale. © 2012 American Chemical Society

  16. Potential for high thermoelectric performance in n-type Zintl compounds: A case study of Ba doped KAlSb 4

    DOE PAGES

    Ortiz, Brenden R.; Gorai, Prashun; Krishna, Lakshmi; ...

    2017-01-11

    High-throughput calculations (first-principles density functional theory and semi-empirical transport models) have the potential to guide the discovery of new thermoelectric materials. Herein we have computationally assessed the potential for thermoelectric performance of 145 complex Zintl pnictides. Of the 145 Zintl compounds assessed, 17% show promising n-type transport properties, compared with only 6% showing promising p-type transport. We predict that n-type Zintl compounds should exhibit high mobility μ n while maintaining the low thermal conductivity κ L typical of Zintl phases. Thus, not only do candidate n-type Zintls outnumber their p-type counterparts, but they may also exhibit improved thermoelectric performance. Frommore » the computational search, we have selected n-type KAlSb 4 as a promising thermoelectric material. Synthesis and characterization of polycrystalline KAlSb 4 reveals non-degenerate n-type transport. With Ba substitution, the carrier concentration is tuned between 10 18 and 10 19 e – cm –3 with a maximum Ba solubility of 0.7% on the K site. High temperature transport measurements confirm a high μ n (50 cm 2 V –1 s –1) coupled with a near minimum κ L (0.5 W m –1 K –1) at 370 °C. Together, these properties yield a zT of 0.7 at 370 °C for the composition K 0.99Ba 0.01AlSb 4. As a result, based on the theoretical predictions and subsequent experimental validation, we find significant motivation for the exploration of n-type thermoelectric performance in other Zintl pnictides.« less

  17. Potential for high thermoelectric performance in n-type Zintl compounds: A case study of Ba doped KAlSb 4

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Ortiz, Brenden R.; Gorai, Prashun; Krishna, Lakshmi

    High-throughput calculations (first-principles density functional theory and semi-empirical transport models) have the potential to guide the discovery of new thermoelectric materials. Herein we have computationally assessed the potential for thermoelectric performance of 145 complex Zintl pnictides. Of the 145 Zintl compounds assessed, 17% show promising n-type transport properties, compared with only 6% showing promising p-type transport. We predict that n-type Zintl compounds should exhibit high mobility μ n while maintaining the low thermal conductivity κ L typical of Zintl phases. Thus, not only do candidate n-type Zintls outnumber their p-type counterparts, but they may also exhibit improved thermoelectric performance. Frommore » the computational search, we have selected n-type KAlSb 4 as a promising thermoelectric material. Synthesis and characterization of polycrystalline KAlSb 4 reveals non-degenerate n-type transport. With Ba substitution, the carrier concentration is tuned between 10 18 and 10 19 e – cm –3 with a maximum Ba solubility of 0.7% on the K site. High temperature transport measurements confirm a high μ n (50 cm 2 V –1 s –1) coupled with a near minimum κ L (0.5 W m –1 K –1) at 370 °C. Together, these properties yield a zT of 0.7 at 370 °C for the composition K 0.99Ba 0.01AlSb 4. As a result, based on the theoretical predictions and subsequent experimental validation, we find significant motivation for the exploration of n-type thermoelectric performance in other Zintl pnictides.« less

  18. Thermoelectricity in fullerene-metal heterojunctions.

    PubMed

    Yee, Shannon K; Malen, Jonathan A; Majumdar, Arun; Segalman, Rachel A

    2011-10-12

    Thermoelectricty in heterojunctions, where a single-molecule is trapped between metal electrodes, has been used to understand transport properties at organic-inorganic interfaces. (1) The transport in these systems is highly dependent on the energy level alignment between the molecular orbitals and the Fermi level (or work function) of the metal contacts. To date, the majority of single-molecule measurements have focused on simple small molecules where transport is dominated through the highest occupied molecular orbital. (2, 3) In these systems, energy level alignment is limited by the absence of electrode materials with low Fermi levels (i.e., large work functions). Alternatively, more controllable alignment between molecular orbitals and the Fermi level can be achieved with molecules whose transport is dominated by the lowest unoccupied molecular orbital (LUMO) because of readily available metals with lower work functions. Herein, we report molecular junction thermoelectric measurements of fullerene molecules (i.e., C(60), PCBM, and C(70)) trapped between metallic electrodes (i.e., Pt, Au, Ag). Fullerene junctions demonstrate the first strongly n-type molecular thermopower corresponding to transport through the LUMO, and the highest measured magnitude of molecular thermopower to date. While the electronic conductance of fullerenes is highly variable, due to fullerene's variable bonding geometries with the electrodes, the thermopower shows predictable trends based on the alignment of the LUMO with the work function of the electrodes. Both the magnitude and trend of the thermopower suggest that heterostructuring organic and inorganic materials at the nanoscale can further enhance thermoelectric performance, therein providing a new pathway for designing thermoelectric materials.

  19. Thermoelectric skutterudite compositions and methods for producing the same

    DOEpatents

    Ren, Zhifeng; Yang, Jian; Yan, Xiao; He, Qinyu; Chen, Gang; Hao, Qing

    2014-11-11

    Compositions related to skutterudite-based thermoelectric materials are disclosed. Such compositions can result in materials that have enhanced ZT values relative to one or more bulk materials from which the compositions are derived. Thermoelectric materials such as n-type and p-type skutterudites with high thermoelectric figures-of-merit can include materials with filler atoms and/or materials formed by compacting particles (e.g., nanoparticles) into a material with a plurality of grains each having a portion having a skutterudite-based structure. Methods of forming thermoelectric skutterudites, which can include the use of hot press processes to consolidate particles, are also disclosed. The particles to be consolidated can be derived from (e.g., grinded from), skutterudite-based bulk materials, elemental materials, other non-Skutterudite-based materials, or combinations of such materials.

  20. Thermoelectric Skutterudite Compositions and Methods for Producing the Same

    NASA Technical Reports Server (NTRS)

    Yang, Jian (Inventor); Yan, Xiao (Inventor); Ren, Zhifeng (Inventor); Hao, Qing (Inventor); He, Qinyu (Inventor); Chen, Gang (Inventor)

    2014-01-01

    Compositions related to skutterudite-based thermoelectric materials are disclosed. Such compositions can result in materials that have enhanced ZT values relative to one or more bulk materials from which the compositions are derived. Thermoelectric materials such as n-type and p-type skutterudites with high thermoelectric figures-of-merit can include materials with filler atoms and/or materials formed by compacting particles (e.g., nanoparticles) into a material with a plurality of grains each having a portion having a skutterudite-based structure. Methods of forming thermoelectric skutterudites, which can include the use of hot press processes to consolidate particles, are also disclosed. The particles to be consolidated can be derived from (e.g., grinded from), skutterudite-based bulk materials, elemental materials, other non-Skutterudite-based materials, or combinations of such materials.

  1. Synergistic Impacts of Electrolyte Adsorption on the Thermoelectric Properties of Single-Walled Carbon Nanotubes.

    PubMed

    Nakano, Motohiro; Nakashima, Takuya; Kawai, Tsuyoshi; Nonoguchi, Yoshiyuki

    2017-08-01

    Single-walled carbon nanotubes are promising candidates for light-weight and flexible energy materials. Recently, the thermoelectric properties of single-walled carbon nanotubes have been dramatically improved by ionic liquid addition; however, controlling factors remain unsolved. Here the thermoelectric properties of single-walled carbon nanotubes enhanced by electrolytes are investigated. Complementary characterization with absorption, Raman, and X-ray photoelectron spectroscopy reveals that shallow hole doping plays a partial role in the enhanced electrical conductivity. The molecular factors controlling the thermoelectric properties of carbon nanotubes are systematically investigated in terms of the ionic functionalities of ionic liquids. It is revealed that appropriate ionic liquids show a synergistic enhancement in conductivity and the Seebeck coefficient. The discovery of significantly precise doping enables the generation of thermoelectric power factor exceeding 460 µW m - 1 K -2 . © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  2. Thermoelectric materials having porosity

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Heremans, Joseph P.; Jaworski, Christopher M.; Jovovic, Vladimir

    A thermoelectric material and a method of making a thermoelectric material are provided. In certain embodiments, the thermoelectric material comprises at least 10 volume percent porosity. In some embodiments, the thermoelectric material has a zT greater than about 1.2 at a temperature of about 375 K. In some embodiments, the thermoelectric material comprises a topological thermoelectric material. In some embodiments, the thermoelectric material comprises a general composition of (Bi.sub.1-xSb.sub.x).sub.u(Te.sub.1-ySe.sub.y).sub.w, wherein 0.ltoreq.x.ltoreq.1, 0.ltoreq.y.ltoreq.1, 1.8.ltoreq.u.ltoreq.2.2, 2.8.ltoreq.w.ltoreq.3.2. In further embodiments, the thermoelectric material includes a compound having at least one group IV element and at least one group VI element. In certain embodiments,more » the method includes providing a powder comprising a thermoelectric composition, pressing the powder, and sintering the powder to form the thermoelectric material.« less

  3. Enhancement of Thermoelectric Properties in Cold Pressed Nickel Doped Bismuth Sulfide Compounds

    NASA Astrophysics Data System (ADS)

    Fitriani, Fitriani; Said, Suhana Mohd; Rozali, Shaifulazuar; Salleh, Mohd Faiz Mohd; Sabri, Mohd Faizul Mohd; Bui, Duc Long; Nakayama, Tadachika; Raihan, Ovik; Megat Hasnan, Megat Muhammad Ikhsan; Bashir, Mohamed Bashir Ali; Kamal, Farhan

    2018-05-01

    Nanostructured Ni doped Bi2S3 (Bi2-xNixS3, 0 ≤ x ≤ 0.07) is explored as a candidate for telluride free thermoelectric material, through a combination process of mechanical alloying with subsequent consolidation by cold pressing followed with a sintering process. The cold pressing method was found to impact the thermoelectric properties in two ways: (1) introduction of the dopant atom in the interstitial sites of the crystal lattice which results in an increase in carrier concentration, and (2) introduction of a porous structure which reduces the thermal conductivity. The electrical resistivity of Bi2S3 was decreased by adding Ni atoms, which shows a minimum value of 2.35 × 10-3 Ω m at 300 °C for Bi1.99Ni0.01S3 sample. The presence of porous structures gives a significant effect on reduction of thermal conductivity, by a reduction of 59.6% compared to a high density Bi2S3. The thermal conductivity of Bi2-xNixS3 ranges from 0.31 to 0.52 W/m K in the temperature range of 27 °C (RT) to 300 °C with the lowest κ values of Bi2S3 compared to the previous works. A maximum ZT value of 0.13 at 300 °C was achieved for Bi1.99Ni0.01S3 sample, which is about 2.6 times higher than (0.05) of Bi2S3 sample. This work show an optimization pathway to improve thermoelectric performance of Bi2S3 through Ni doping and introduction of porosity.

  4. Zintl Phases for Thermoelectric Applications

    NASA Technical Reports Server (NTRS)

    Snyder, G. Jeffrey (Inventor); Toberer, Eric (Inventor); Zevalkink, Alex (Inventor)

    2014-01-01

    The inventors demonstrate herein that various Zintl compounds can be useful as thermoelectric materials for a variety of applications. Specifically, the utility of Ca3AlSb3, Ca5Al2Sb6, Ca5In2Sb6, Ca5Ga2Sb6, is described herein. Carrier concentration control via doping has also been demonstrated, resulting in considerably improved thermoelectric performance in the various systems described herein.

  5. Strikingly enhanced cooling performance for a micro-cooler using unique Cu nanowire array with high electrical conductivity and fast heat transfer behavior

    NASA Astrophysics Data System (ADS)

    Tan, Ming; Wang, Xiuzhen; Hao, Yanming; Deng, Yuan

    2017-06-01

    It was found that phonons/electrons are less scattered along (1 1 1)-preferred Cu nanowires than in ordinary structure films and that the interface of Cu nanowires electrode and thermoelectric materials are more compatible. Here highly ordered, high-crystal-quality, high-density Cu nanowire array was successfully fabricated by a magnetron sputtering method. The Cu nanowire array was successfully incorporated using mask-assisted deposition technology as electrodes for thin-film thermoelectric coolers, which would greatly improve electrical/thermal transport and enhance performance of micro-coolers. The cooling performance of the micro-cooler with Cu nanowire array electrode is over 200% higher than that of the cooler with ordinary film electrode.

  6. Design Optimization of a Thermoelectric Cooling Module Using Finite Element Simulations

    NASA Astrophysics Data System (ADS)

    Abid, Muhammad; Somdalen, Ragnar; Rodrigo, Marina Sancho

    2018-05-01

    The thermoelectric industry is concerned about the size reduction, cooling performance and, ultimately, the production cost of thermoelectric modules. Optimization of the size and performance of a commercially available thermoelectric cooling module is considered using finite element simulations. Numerical simulations are performed on eight different three-dimensional geometries of a single thermocouple, and the results are further extended for a whole module as well. The maximum temperature rise at the hot and cold sides of a thermocouple is determined by altering its height and cross-sectional area. The influence of the soldering layer is analyzed numerically using temperature dependent and temperature independent thermoelectric properties of the solder material and the semiconductor pellets. Experiments are conducted to test the cooling performance of the thermoelectric module and the results are compared with the results obtained through simulations. Finally, cooling rate and maximum coefficient of performance (COPmax) are computed using convective and non-convective boundary conditions.

  7. Effect of Ag doping and annealing on thermoelectric properties of PbTe

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Bala, Manju, E-mail: Manjubala474@gmail.com; Tripathi, T. S.; Avasthi, D. K.

    2015-06-24

    The present study reveals that annealing Ag doped PbTe thin films enhance thermoelectric properties. Phase formation was identified by using X-ray diffraction measurement. Annealing increases the crystallinity of both undoped and Ag doped PbTe. Electrical resistivity and thermoelectric power measurements are done using four probe and bridge method respectively. The increase in thermoelectric power of Ag doped PbTe is 29 % in comparison to undoped PbTe and it further increases to 34 % after annealing at 250{sup o} C for 1 hour whereas thermoelectric power increases by 14 % on annealing undoped PbTe thin films at same temperature.

  8. Design, manufacturing and testing of a portable vaccine carrier box employing thermoelectric module and heat pipe.

    PubMed

    Putra, N

    2009-01-01

    Vaccination is a highly effective method and a cheap tool for preventing certain infectious diseases. Routine immunization programs protect most of the world's children from diseases that claim millions of lives each year. There are many practical problems impeding vaccine delivery, especially to maintain the cold chain system, which is the means for storing and transporting vaccines in a potent state from the manufacturer to the person being immunized at a temperature of 2-8 degrees C. The development of the solid state thermoelectric cooling system has permitted newly developed packages that are capable of meeting many requirements and applications where environmental concern, size, weight, performance and noise are an issue. This paper describes the development of a vaccine carrier box. A combination of a thermoelectric module and a heat pipe is used for the cooling system. The position of the heat pipe as a heat sink on the hot side of the thermoelectric module will enhance the thermoelectric performance. The minimum temperature in the cabin of the vaccine carrier box reached -10 degrees C, which indicates that the design of the vaccine carrier box can maintain the vaccine at desired temperatures.

  9. Achieving high thermoelectric performance of Cu1.8S composites with WSe2 nanoparticles.

    PubMed

    Qin, Peng; Ge, Zhen-Hua; Chen, Yue-Xing; Chong, Xiaoyu; Feng, Jing; He, Jiaqing

    2018-08-24

    Polycrystalline p-type Cu 1.8 S composites with WSe 2 nanoparticles were fabricated by the mechanical alloying method combined with the spark plasma sintering technique. The Seebeck coefficient was significantly enhanced by the optimized carrier concentration, while the thermal conductivity was simultaneously decreased due to the refined grain and WSe 2 nanoparticles. An enhanced Seebeck coefficient of 110 μV K -1 and a reduced thermal conductivity of 0.68 W m -1 K -1 were obtained for the Cu 1.8 S + 1 wt% WSe 2 sample at 773 K, resulting in a remarkably enhanced peak ZT of 1.22 at 773 K, which is 2.5 times higher than that (0.49 at 773 K) of a pristine Cu 1.8 S sample. The cheap and environmentally friendly Cu 1.8 S-based materials with enhanced properties may find promising applications in thermoelectric devices.

  10. Thermomechanical In Situ Monitoring of Bi2Te3 Thin Film and Its Relationship with Microstructure and Thermoelectric Performances

    NASA Astrophysics Data System (ADS)

    Jeong, Min-Woo; Na, Sekwon; Shin, Haishan; Park, Hong-Bum; Lee, Hoo-Jeong; Joo, Young-Chang

    2018-04-01

    Performance enhancement has been studied for thin-film thermoelectric materials for small-scale energy applications. The microstructural evolution of bismuth telluride (Bi2Te3) was investigated with respect to performance enhancement via in situ thermomechanical analysis due to the post-annealing process. The thermomechanical behavior of Bi2Te3 changes gradually at approximately 200 °C with the formation of a quintuple-layer structure, which was confirmed by X-ray diffraction, transmission electron microscopy and Raman spectroscopy. It was found that highly oriented (006), (0015) was formed with a quintuple-layer structure parallel to the substrate, and the Eg 2Raman vibration mode of Bi2Te3 significantly increased after forming the layer structure with decreased defects. Therefore, the slope of the stress curve was affected by the longer atomic distance of the van der Waals bonds with the formation of (00l) oriented layered-structure grain. The decreased number of defects in the layer structure affects the electrical and thermal properties of the Bi2Te3 thin film. Due to the microstructural evolution, the power factor of Bi2Te3 was enhanced by approximately 14.8 times by the quintuple-layer structure of Bi2Te3 formed during the annealing process, which contributed to a better understanding of the performance enhancement via post-annealing and to research on other highly oriented layer structure materials.

  11. Localized Vibrations of Bi Bilayer Leading to Ultralow Lattice Thermal Conductivity and High Thermoelectric Performance in Weak Topological Insulator n-Type BiSe.

    PubMed

    Samanta, Manisha; Pal, Koushik; Pal, Provas; Waghmare, Umesh V; Biswas, Kanishka

    2018-05-02

    Realization of high thermoelectric performance in n-type semiconductors is of imperative need on account of the dearth of efficient n-type thermoelectric materials compared to the p-type counterpart. Moreover, development of efficient thermoelectric materials based on Te-free compounds is desirable because of the scarcity of Te in the Earth's crust. Herein, we report the intrinsic ultralow thermal conductivity and high thermoelectric performance near room temperature in n-type BiSe, a Te-free solid, which recently has emerged as a weak topological insulator. BiSe possesses a layered structure consisting of a bismuth bilayer (Bi 2 ) sandwiched between two Bi 2 Se 3 quintuple layers [Se-Bi-Se-Bi-Se], resembling natural heterostructure. High thermoelectric performance of BiSe is realized through the ultralow lattice thermal conductivity (κ lat of ∼0.6 W/mK at 300 K), which is significantly lower than that of Bi 2 Se 3 (κ lat of ∼1.8 W/mK at 300 K), although both of them belong to the same layered homologous family (Bi 2 ) m (Bi 2 Se 3 ) n . Phonon dispersion calculated from first-principles and the experimental low-temperature specific heat data indicate that soft localized vibrations of bismuth bilayer in BiSe are responsible for its ultralow κ lat . These low energy optical phonon branches couple strongly with the heat carrying acoustic phonons, and consequently suppress the phonon mean free path leading to low κ lat . Further optimization of thermoelectric properties of BiSe through Sb substitution and spark plasma sintering (SPS) results in high ZT ∼ 0.8 at 425 K along the pressing direction, which is indeed remarkable among Te-free n-type thermoelectric materials near room temperature.

  12. Numerical Investigation on the Performance of an Automotive Thermoelectric Generator with Exhaust-Module-Coolant Direct Contact

    NASA Astrophysics Data System (ADS)

    Wang, Yiping; Tang, Yulin; Deng, Yadong; Su, Chuqi

    2017-12-01

    Energy conservation and environmental protection have typically been a concern of research. Researchers have confirmed that in automotive engines, just 12-25% of the fuel energy converts into effective work and 30-40% gets wasted in the form of exhaust. Saidur et al. (Energy Policy 37:3650, 2009) and Hasanuzzaman et al. (Energy 36:233, 2011). It will be significant to enhance fuel availability and decrease environmental pollution if the waste heat in the exhaust could be recovered. Thermoelectric generators (TEGs), which can translate heat into electricity, have become a topic of interest for vehicle exhaust waste heat recovery. In conventional automotive TEGs, the thermoelectric modules (TEMs) are arranged between the exhaust tank and the coolant tank. The TEMs do not contact the hot exhaust and coolant, which leads to low heat transfer efficiency. Moreover, to provide enough packing force to keep good contact with the exhaust tank and the coolant tank, the framework required is so robust that the TEGs become too heavy. Therefore, in current study, an automotive TEG was designed which included one exhaust channel, one coolant channel and several TEMs. In the TEG, the TEMs which contacted the exhaust and coolant directly were inserted into the walls of each coolant channel. To evaluate the performance of the automotive TEG, the flow field and temperature field were computed by computational fluid dynamics (CFD). Based on the temperature distribution obtained by CFD and the performance parameters of the modules, the total power generation was obtained by some proved empirical formulas. Compared with conventional automotive TEGs, the power generation per unit volume exhaust was boosted.

  13. Numerical Investigation on the Performance of an Automotive Thermoelectric Generator with Exhaust-Module-Coolant Direct Contact

    NASA Astrophysics Data System (ADS)

    Wang, Yiping; Tang, Yulin; Deng, Yadong; Su, Chuqi

    2018-06-01

    Energy conservation and environmental protection have typically been a concern of research. Researchers have confirmed that in automotive engines, just 12-25% of the fuel energy converts into effective work and 30-40% gets wasted in the form of exhaust. Saidur et al. (Energy Policy 37:3650, 2009) and Hasanuzzaman et al. (Energy 36:233, 2011). It will be significant to enhance fuel availability and decrease environmental pollution if the waste heat in the exhaust could be recovered. Thermoelectric generators (TEGs), which can translate heat into electricity, have become a topic of interest for vehicle exhaust waste heat recovery. In conventional automotive TEGs, the thermoelectric modules (TEMs) are arranged between the exhaust tank and the coolant tank. The TEMs do not contact the hot exhaust and coolant, which leads to low heat transfer efficiency. Moreover, to provide enough packing force to keep good contact with the exhaust tank and the coolant tank, the framework required is so robust that the TEGs become too heavy. Therefore, in current study, an automotive TEG was designed which included one exhaust channel, one coolant channel and several TEMs. In the TEG, the TEMs which contacted the exhaust and coolant directly were inserted into the walls of each coolant channel. To evaluate the performance of the automotive TEG, the flow field and temperature field were computed by computational fluid dynamics (CFD). Based on the temperature distribution obtained by CFD and the performance parameters of the modules, the total power generation was obtained by some proved empirical formulas. Compared with conventional automotive TEGs, the power generation per unit volume exhaust was boosted.

  14. High-accuracy direct ZT and intrinsic properties measurement of thermoelectric couple devices.

    PubMed

    Kraemer, D; Chen, G

    2014-04-01

    Advances in thermoelectric materials in recent years have led to significant improvements in thermoelectric device performance and thus, give rise to many new potential applications. In order to optimize a thermoelectric device for specific applications and to accurately predict its performance ideally the material's figure of merit ZT as well as the individual intrinsic properties (Seebeck coefficient, electrical resistivity, and thermal conductivity) should be known with high accuracy. For that matter, we developed two experimental methods in which the first directly obtains the ZT and the second directly measures the individual intrinsic leg properties of the same p/n-type thermoelectric couple device. This has the advantage that all material properties are measured in the same sample direction after the thermoelectric legs have been mounted in the final device. Therefore, possible effects from crystal anisotropy and from the device fabrication process are accounted for. The Seebeck coefficients, electrical resistivities, and thermal conductivities are measured with differential methods to minimize measurement uncertainties to below 3%. The thermoelectric couple ZT is directly measured with a differential Harman method which is in excellent agreement with the calculated ZT from the individual leg properties. The errors in both the directly measured and calculated thermoelectric couple ZT are below 5% which is significantly lower than typical uncertainties using commercial methods. Thus, the developed technique is ideal for characterizing assembled couple devices and individual thermoelectric materials and enables accurate device optimization and performance predictions. We demonstrate the methods by measuring a p/n-type thermoelectric couple device assembled from commercial bulk thermoelectric Bi2Te3 elements in the temperature range of 30 °C-150 °C and discuss the performance of the couple thermoelectric generator in terms of its efficiency and materials

  15. On the tuning of electrical and thermal transport in thermoelectrics: an integrated theory–experiment perspective

    DOE PAGES

    Yang, Jiong; Xi, Lili; Qiu, Wujie; ...

    2016-02-26

    During the last two decades, we have witnessed great progress in research on thermoelectrics. There are two primary focuses. One is the fundamental understanding of electrical and thermal transport, enabled by the interplay of theory and experiment; the other is the substantial enhancement of the performance of various thermoelectric materials, through synergistic optimisation of those intercorrelated transport parameters. In this article, we review some of the successful strategies for tuning electrical and thermal transport. For electrical transport, we start from the classical but still very active strategy of tuning band degeneracy (or band convergence), then discuss the engineering of carriermore » scattering, and finally address the concept of conduction channels and conductive networks that emerge in complex thermoelectric materials. For thermal transport, we summarise the approaches for studying thermal transport based on phonon–phonon interactions valid for conventional solids, as well as some quantitative efforts for nanostructures. We also discuss the thermal transport in complex materials with chemical-bond hierarchy, in which a portion of the atoms (or subunits) are weakly bonded to the rest of the structure, leading to an intrinsic manifestation of part-crystalline part-liquid state at elevated temperatures. In this review, we provide a summary of achievements made in recent studies of thermoelectric transport properties, and demonstrate how they have led to improvements in thermoelectric performance by the integration of modern theory and experiment, and point out some challenges and possible directions.« less

  16. Thermoelectric module

    DOEpatents

    Kortier, William E.; Mueller, John J.; Eggers, Philip E.

    1980-07-08

    A thermoelectric module containing lead telluride as the thermoelectric mrial is encapsulated as tightly as possible in a stainless steel canister to provide minimum void volume in the canister. The lead telluride thermoelectric elements are pressure-contacted to a tungsten hot strap and metallurgically bonded at the cold junction to iron shoes with a barrier layer of tin telluride between the iron shoe and the p-type lead telluride element.

  17. Superlattice-based thin-film thermoelectric modules with high cooling fluxes

    PubMed Central

    Bulman, Gary; Barletta, Phil; Lewis, Jay; Baldasaro, Nicholas; Manno, Michael; Bar-Cohen, Avram; Yang, Bao

    2016-01-01

    In present-day high-performance electronic components, the generated heat loads result in unacceptably high junction temperatures and reduced component lifetimes. Thermoelectric modules can, in principle, enhance heat removal and reduce the temperatures of such electronic devices. However, state-of-the-art bulk thermoelectric modules have a maximum cooling flux qmax of only about 10 W cm−2, while state-of-the art commercial thin-film modules have a qmax <100 W cm−2. Such flux values are insufficient for thermal management of modern high-power devices. Here we show that cooling fluxes of 258 W cm−2 can be achieved in thin-film Bi2Te3-based superlattice thermoelectric modules. These devices utilize a p-type Sb2Te3/Bi2Te3 superlattice and n-type δ-doped Bi2Te3−xSex, both of which are grown heteroepitaxially using metalorganic chemical vapour deposition. We anticipate that the demonstration of these high-cooling-flux modules will have far-reaching impacts in diverse applications, such as advanced computer processors, radio-frequency power devices, quantum cascade lasers and DNA micro-arrays. PMID:26757675

  18. Impact of energy filtering and carrier localization on the thermoelectric properties of granular semiconductors

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Narducci, Dario, E-mail: dario.narducci@unimib.it; Consorzio DeltaTi Research; Selezneva, Ekaterina

    2012-09-15

    Energy filtering has been widely considered as a suitable tool to increase the thermoelectric performances of several classes of materials. In its essence, energy filtering provides a way to increase the Seebeck coefficient by introducing a strongly energy-dependent scattering mechanism. Under certain conditions, however, potential barriers may lead to carrier localization, that may also affect the thermoelectric properties of a material. A model is proposed, actually showing that randomly distributed potential barriers (as those found, e.g., in polycrystalline films) may lead to the simultaneous occurrence of energy filtering and carrier localization. Localization is shown to cause a decrease of themore » actual carrier density that, along with the quantum tunneling of carriers, may result in an unexpected increase of the power factor with the doping level. The model is corroborated toward experimental data gathered by several authors on degenerate polycrystalline silicon and lead telluride. - Graphical abstract: In heavily doped semiconductors potential barriers may lead to both carrier energy filtering and localization. This may lead to an enhancement of the thermoelectric properties of the material, resulting in an unexpected increase of the power factor with the doping level. Highlights: Black-Right-Pointing-Pointer Potential barriers are shown to lead to carrier localization in thermoelectric materials. Black-Right-Pointing-Pointer Evidence is put forward of the formation of a mobility edge. Black-Right-Pointing-Pointer Energy filtering and localization may explain the enhancement of power factor in degenerate semiconductors.« less

  19. Novel Transition Metal Compounds with Promising Thermoelectric Properties

    NASA Technical Reports Server (NTRS)

    Caillat, T.; Borshchevsky, A.; Fleurial, J. -P.

    1993-01-01

    Progress in the search for new high temperature thermoelectric materials at the Jet Propulsion Laboratory is reviewed. Novel transition metal compounds were selected as potential new high performance thermoelectric materials and criteria of selection are presented and discussed. Samples of these new compounds were prepared at JPL by a variety of techniques. Encouraging experimental results obtained on several of these compounds are reported and show that they have the potential to be the next generation of thermoelectric materials.

  20. The effect of shallow vs. deep level doping on the performance of thermoelectric materials

    NASA Astrophysics Data System (ADS)

    Song, Qichen; Zhou, Jiawei; Meroueh, Laureen; Broido, David; Ren, Zhifeng; Chen, Gang

    2016-12-01

    It is well known that the efficiency of a good thermoelectric material should be optimized with respect to doping concentration. However, much less attention has been paid to the optimization of the dopant's energy level. Thermoelectric materials doped with shallow levels may experience a dramatic reduction in their figures of merit at high temperatures due to the excitation of minority carriers that reduces the Seebeck coefficient and increases bipolar heat conduction. Doping with deep level impurities can delay the excitation of minority carriers as it requires a higher temperature to ionize all dopants. We find through modeling that, depending on the material type and temperature range of operation, different impurity levels (shallow or deep) will be desired to optimize the efficiency of a thermoelectric material. For different materials, we further clarify where the most preferable position of the impurity level within the bandgap falls. Our research provides insight on why different dopants often affect thermoelectric transport properties differently and directions in searching for the most appropriate dopants for a thermoelectric material in order to maximize the device efficiency.

  1. Enhanced thermoelectric properties of phase-separating bismuth selenium telluride thin films via a two-step method

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Takashiri, Masayuki, E-mail: takashiri@tokai-u.jp; Kurita, Kensuke; Hagino, Harutoshi

    2015-08-14

    A two-step method that combines homogeneous electron beam (EB) irradiation and thermal annealing has been developed to enhance the thermoelectric properties of nanocrystalline bismuth selenium telluride thin films. The thin films, prepared using a flash evaporation method, were treated with EB irradiation in a N{sub 2} atmosphere at room temperature and an acceleration voltage of 0.17 MeV. Thermal annealing was performed under Ar/H{sub 2} (5%) at 300 °C for 60 min. X-ray diffraction was used to determine that compositional phase separation between bismuth telluride and bismuth selenium telluride developed in the thin films exposed to higher EB doses and thermal annealing. We proposemore » that the phase separation was induced by fluctuations in the distribution of selenium atoms after EB irradiation, followed by the migration of selenium atoms to more stable sites during thermal annealing. As a result, thin film crystallinity improved and mobility was significantly enhanced. This indicates that the phase separation resulting from the two-step method enhanced, rather than disturbed, the electron transport. Both the electrical conductivity and the Seebeck coefficient were improved following the two-step method. Consequently, the power factor of thin films that underwent the two-step method was enhanced to 20 times (from 0.96 to 21.0 μW/(cm K{sup 2}) that of the thin films treated with EB irradiation alone.« less

  2. Mechanochemical synthesis of high thermoelectric performance bulk Cu 2X (X = S, Se) materials

    DOE PAGES

    Yang, Dongwang; Su, Xianli; Yan, Yonggao; ...

    2016-11-01

    We devised a single-step mechanochemical synthesis/densification procedure for Cu 2X (X = S, Se) thermoelectric materials via applying a pressure of 3 GPa to a stoichiometric admixture of elemental Cu and X for 3 min at room temperature. The obtained bulk materials were single-phase, nearly stoichiometric structures with a relative packing density of 97% or higher. The structures contained high concentration of atomic scale defects and pores of 20-200 nm diameter. The above attributes gave rise to a high thermoelectric performance: at 873 K, the ZT value of Cu2S reached 1.07, about 2.1 times the value typical of samples grownmore » from the melt. The ZT value of Cu 2Se samples reached in excess of 1.2, close to the state-of-the-art value.« less

  3. Gate-Tuned Thermoelectric Power in Black Phosphorus.

    PubMed

    Saito, Yu; Iizuka, Takahiko; Koretsune, Takashi; Arita, Ryotaro; Shimizu, Sunao; Iwasa, Yoshihiro

    2016-08-10

    The electric field effect is a useful means of elucidating intrinsic material properties as well as for designing functional devices. The electric-double-layer transistor (EDLT) enables the control of carrier density in a wide range, which is recently proved to be an effective tool for the investigation of thermoelectric properties. Here, we report the gate-tuning of thermoelectric power in a black phosphorus (BP) single crystal flake with the thickness of 40 nm. Using an EDLT configuration, we successfully control the thermoelectric power (S) and find that the S of ion-gated BP reached +510 μV/K at 210 K in the hole depleted state, which is much higher than the reported bulk single crystal value of +340 μV/K at 300 K. We compared this experimental data with the first-principles-based calculation and found that this enhancement is qualitatively explained by the effective thinning of the conduction channel of the BP flake and nonuniformity of the channel owing to the gate operation in a depletion mode. Our results provide new opportunities for further engineering BP as a thermoelectric material in nanoscale.

  4. p × n-Type Transverse Thermoelectrics: A Novel Type of Thermal Management Material

    NASA Astrophysics Data System (ADS)

    Tang, Yang; Cui, Boya; Zhou, Chuanle; Grayson, Matthew

    2015-06-01

    In this paper we review the recently identified p × n-type transverse thermoelectrics and study the thermoelectric properties of the proposed candidate materials. Anisotropic electron and hole conductivity arise from either an artificially engineered band structure or from appropriately anisotropic crystals, and result in orthogonal p-type and n-type directional Seebeck coefficients, inducing a non-zero off-diagonal transverse Seebeck coefficient with appropriately oriented currents. Such materials have potential for new applications of thermoelectric materials in transverse Peltier cooling and transverse thermal energy harvesting. In this paper we review general transverse thermoelectric phenomena to identify advantages of p × n-type transverse thermoelectrics compared with previously studied transverse thermoelectric phenomena. An intuitive overview of the band structure of one such p × n-material, the InAs/GaSb type-II superlattice, is introduced, and the plot of thermoelectric performance as a function of superlattice structure is calculated, as an example of how band structures can be optimized for the best transverse thermoelectric performance.

  5. Thermoelectric Energy Harvesting Using Phase Change Materials (PCMs) in High Temperature Environments in Aircraft

    NASA Astrophysics Data System (ADS)

    Elefsiniotis, A.; Becker, Th.; Schmid, U.

    2014-06-01

    Wireless, energy-autonomous structural health-monitoring systems in aircraft have the potential of reducing total maintenance costs. Thermoelectric energy harvesting, which seems the best choice for creating truly autonomous health monitoring sensors, is the principle behind converting waste heat to useful electrical energy through the use of thermoelectric generators. To enhance the temperature difference across the two sides of a thermoelectric generator, i.e. increasing heat flux and energy production, a phase change material acting as thermal mass is attached on one side of the thermoelectric generators while the other side is placed on the aircraft structure. The application area under investigation for this paper is the pylon aft fairing, located near the engine of an aircraft, with temperatures reaching on the inside up to 350 °C. Given these harsh operational conditions, the performance of a device, containing erythritol as a phase change material, is evaluated. The harvested energy reaching values up to 81.4 J can be regulated by a power management module capable of storing the excess energy and recovering it from the medium powering a sensor node and a wireless transceiver.

  6. Mechanical properties of thermoelectric n-type magnesium silicide synthesized employing in situ spark plasma reaction sintering

    NASA Astrophysics Data System (ADS)

    Muthiah, Saravanan; Singh, R. C.; Pathak, B. D.; Dhar, Ajay

    2017-07-01

    Thermoelectric devices employing magnesium silicide (Mg2Si) offer an inexpensive and non-toxic solution for green energy generation compared to other existing conventional thermoelectric materials in the mid-temperature range. However, apart from the thermoelectric performance, their mechanical properties are equally important in order to avoid the catastrophic failure of their modules during actual operation. In the present study, we report the synthesis of Mg2Si co-doped with Bi and Sb employing in situ spark plasma reaction sintering and investigate its broad range of mechanical properties. The mechanical properties of the sintered co-doped Mg2Si suggest a significantly enhanced value of hardness ~5.4  ±  0.2 GPa and an elastic modulus ~142.5  ±  6 GPa with a fracture toughness of ~1.71  ±  0.1 MPa  √m. The thermal shock resistance, which is one of the most vital parameter for designing thermoelectric devices, was found to be ~300 W m-1, which is higher than most of the other existing state-of-the-art mid-temperature thermoelectric materials. The friction and wear characteristics of sintered co-doped Mg2Si have been reported for the first time, in order to realize the sustainability of their thermoelectric modules under actual hostile environmental conditions.

  7. Camel-back band-induced power factor enhancement of thermoelectric lead-tellurium from Boltzmann transport calculations

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wang, X. G., E-mail: wang2006@mail.ustc.edu.cn; Wang, L., E-mail: sqtb@mail.ustc.edu.cn; Liu, J., E-mail: jingliu@mail.ustc.edu.cn

    2014-03-31

    Band structures of PbTe can be abnormally bended via dual-doping on both the cationic and anionic sites to form camel-back multivalley energy band structures near the band edge. As a result, additional carrier pockets and strong intervalley scattering of carriers are introduced. Boltzmann transport calculations indicate that their contradictory effects yield remarkably enhanced power factor due to the improved thermopower and almost unchanged electrical conductivity in low temperature and high carrier concentration ranges. These findings prove dual-doping-induced band bending as an effective approach to improve the thermoelectric properties of PbTe and other similar materials.

  8. Thermoelectric properties of doped BaHfO{sub 3}

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Dixit, Chandra Kr., E-mail: ckparadise@gmail.com, E-mail: sharmarameshfgiet@gmail.com; Bhamu, K. C.; Sharma, Ramesh, E-mail: ckparadise@gmail.com, E-mail: sharmarameshfgiet@gmail.com

    2016-05-06

    We have studied the structural stability, electronic structure, optical properties and thermoelectric properties of doped BaHfO{sub 3} by full potential linearized augmented plane wave (FP-LAPW) method. The electronic structure of BaHfO{sub 3} doped with Sr shows enhances the indirect band gaps of 3.53 eV, 3.58 eV. The charge density plots show strong ionic bonding in Ba-Hf, and ionic and covalent bonding between Hf and O. Calculations of the optical spectra, viz., the dielectric function, refractive index and extinction coefficient are performed for the energy range are calculated and analyzed. Thermoelectric properties of semi conducting are also reported first time. Themore » doped BaHfO{sub 3} is approximately wide band gap semiconductor with the large p-type Seebeck coefficient. The power factor of BaHfO{sub 3} is increased with Sr doping, decreases because of low electrical resistivity and thermal conductivity.« less

  9. Enhancement of thermoelectric properties in the Nb–Co–Sn half-Heusler/Heusler system through spontaneous inclusion of a coherent second phase

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Buffon, Malinda L. C., E-mail: mandibuffon@mrl.ucsb.edu; Verma, Nisha; Lamontagne, Leo

    Half-Heusler XYZ compounds with an 18 valence electron count are promising thermoelectric materials, being thermally and chemically stable, deriving from relatively earth-abundant components, and possessing appropriate electrical transport properties. The typical drawback with this family of compounds is their high thermal conductivity. A strategy for reducing thermal conductivity is through the inclusion of secondary phases designed to minimize negative impact on other properties. Here, we achieve this through the addition of excess Co to half-Heusler NbCoSn, which introduces precipitates of a semi-coherent NbCo{sub 2}Sn Heusler phase. A series of NbCo{sub 1+x}Sn materials are characterized here using X-ray and neutron diffractionmore » studies and electron microscopy. Electrical and thermal transport measurements and electronic structure calculations are used to understand property evolution. We find that annealing has an important role to play in determining antisite ordering and properties. Antisite disorder in the as-prepared samples improves thermoelectric performance through the reduction of thermal conductivity, but annealing during the measurement degrades properties to resemble those of the annealed samples. Similar to the more widely studied TiNi{sub 1+x}Sn system, Co addition to the NbCoSn phase results in improved thermoelectric performance through a decrease in thermal conductivity which results in a 20% improvement in the thermoelectric figure of merit, zT.« less

  10. Thermomechanical In Situ Monitoring of Bi2Te3 Thin Film and Its Relationship with Microstructure and Thermoelectric Performances

    NASA Astrophysics Data System (ADS)

    Jeong, Min-Woo; Na, Sekwon; Shin, Haishan; Park, Hong-Bum; Lee, Hoo-Jeong; Joo, Young-Chang

    2018-07-01

    Performance enhancement has been studied for thin-film thermoelectric materials for small-scale energy applications. The microstructural evolution of bismuth telluride (Bi2Te3) was investigated with respect to performance enhancement via in situ thermomechanical analysis due to the post-annealing process. The thermomechanical behavior of Bi2Te3 changes gradually at approximately 200 °C with the formation of a quintuple-layer structure, which was confirmed by X-ray diffraction, transmission electron microscopy and Raman spectroscopy. It was found that highly oriented (006), (0015) was formed with a quintuple-layer structure parallel to the substrate, and the E g 2 Raman vibration mode of Bi2Te3 significantly increased after forming the layer structure with decreased defects. Therefore, the slope of the stress curve was affected by the longer atomic distance of the van der Waals bonds with the formation of (00 l) oriented layered-structure grain. The decreased number of defects in the layer structure affects the electrical and thermal properties of the Bi2Te3 thin film. Due to the microstructural evolution, the power factor of Bi2Te3 was enhanced by approximately 14.8 times by the quintuple-layer structure of Bi2Te3 formed during the annealing process, which contributed to a better understanding of the performance enhancement via post-annealing and to research on other highly oriented layer structure materials.

  11. An impurity intermediate band due to Pb doping induced promising thermoelectric performance of Ca5In2Sb6.

    PubMed

    Feng, Zhenzhen; Wang, Yuanxu; Yan, Yuli; Zhang, Guangbiao; Yang, Jueming; Zhang, Jihua; Wang, Chao

    2015-06-21

    Band engineering is one of the effective approaches for designing ideal thermoelectric materials. Introducing an intermediate band in the band gap of semiconducting thermoelectric compounds may largely increase the carrier concentration and improve the electrical conductivity of these compounds. We test this hypothesis by Pb doping in Zintl Ca5In2Sb6. In the current work, we have systematically investigated the electronic structure and thermoelectric performances of substitutional doping with Pb on In sites at a doping level of 5% (0.2 e per cell) for Ca5In2Sb6 by using density functional theory combined with semi-classical Boltzmann theory. It is found that in contrast to Zn doping, Pb doping introduces a partially filled intermediate band in the band gap of Ca5In2Sb6, which originates from the Pb s states by weakly hybridizing with the Sb p states. Such an intermediate band dramatically increases the electrical conductivity of Ca5In2Sb6 and has little detrimental effect on its Seebeck coefficient, which may increase its thermoelectric figure of merit, ZT. Interestingly, a maximum ZT value of 2.46 may be achieved at 900 K for crystalline Pb-doped Ca5In2Sb6 when the carrier concentration is optimized. Therefore, Pb-doped Ca5In2Sb6 may be a promising thermoelectric material.

  12. Performance Analysis and Optimization of Concentrating Solar Thermoelectric Generator

    NASA Astrophysics Data System (ADS)

    Lamba, Ravita; Manikandan, S.; Kaushik, S. C.

    2018-06-01

    A thermodynamic model for a concentrating solar thermoelectric generator considering the Thomson effect combined with Fourier heat conduction, Peltier, and Joule heating has been developed and optimized in MATLAB environment. The temperatures at the hot and cold junctions of the thermoelectric generator were evaluated by solving the energy balance equations at both junctions. The effects of the solar concentration ratio, input electrical current, number of thermocouples, and electrical load resistance ratio on the power output and energy and exergy efficiencies of the system were studied. Optimization studies were carried out for the STEG system, and the optimum number of thermocouples, concentration ratio, and resistance ratio determined. The results showed that the optimum values of these parameters are different for conditions of maximum power output and maximum energy and exergy efficiency. The optimum values of the concentration ratio and load resistance ratio for maximum energy efficiency of 5.85% and maximum exergy efficiency of 6.29% were found to be 180 and 1.3, respectively, with corresponding power output of 4.213 W. Furthermore, at higher concentration ratio (C = 600), the optimum number of thermocouples was found to be 101 for maximum power output of 13.75 W, maximum energy efficiency of 5.73%, and maximum exergy efficiency of 6.16%. Moreover, the optimum number of thermocouple was the same for conditions of maximum power output and energy and exergy efficiency. The results of this study may provide insight for design of actual concentrated solar thermoelectric generator systems.

  13. Hinge-like structure induced unusual properties of black phosphorus and new strategies to improve the thermoelectric performance

    PubMed Central

    Qin, Guangzhao; Yan, Qing-Bo; Qin, Zhenzhen; Yue, Sheng-Ying; Cui, Hui-Juan; Zheng, Qing-Rong; Su, Gang

    2014-01-01

    We systematically investigated the geometric, electronic and thermoelectric (TE) properties of bulk black phosphorus (BP) under strain. The hinge-like structure of BP brings unusual mechanical responses such as anisotropic Young's modulus and negative Poisson's ratio. A sensitive electronic structure of BP makes it transform among metal, direct and indirect semiconductors under strain. The maximal figure of merit ZT of BP is found to be 0.72 at 800 K that could be enhanced to 0.87 by exerting an appropriate strain, revealing BP could be a potential medium-high temperature TE material. Such strain-induced enhancements of TE performance are often observed to occur at the boundary of the direct-indirect band gap transition, which can be attributed to the increase of degeneracy of energy valleys at the transition point. By comparing the structure of BP with SnSe, a family of potential TE materials with hinge-like structure are suggested. This study not only exposes various novel properties of BP under strain, but also proposes effective strategies to seek for better TE materials. PMID:25374306

  14. Giant Pressure-Induced Enhancement of Seebeck Coefficient and Thermoelectric Efficiency in SnTe

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Baker, Jason; Kumar, Ravhi; Park, Changyong

    The thermoelectric properties of polycrystalline SnTe have been measured up to 4.5 GPa at 330 K. SnTe shows an enormous enhancement in Seebeck coefficient, greater than 200 % after 3 GPa, which correlates to a known pressure-induced structural phase transition that is observed through simultaneous in situ X-ray diffraction measurement. We also measured electrical resistance and relative changes to the thermal conductivity, enabling the determination of relative changes in the dimensionless figure of merit (ZT), which increases dramatically after 3 GPa, reaching 350 % of the lowest pressure ZT value. Our results demonstrate a fundamental relationship between structure and thermoelectricmore » behaviours and suggest that pressure is an effective tool to control them.« less

  15. Giant Pressure-Induced Enhancement of Seebeck Coefficient and Thermoelectric Efficiency in SnTe

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Baker, Jason; Kumar, Ravhi; Park, Changyong

    The thermoelectric properties of polycrystalline SnTe have been measured up to 4.5 GPa at 330 K. SnTe shows an enormous enhancement in Seebeck coefficient, greater than 200 % after 3 GPa, which correlates to a known pressure-induced structural phase transition that is observed through simultaneous in situ X-ray diffraction measurement. Electrical resistance and relative changes to the thermal conductivity were also measured, enabling the determination of relative changes in the dimensionless figure of merit (ZT), which increases dramatically after 3 GPa, reaching 350 % of the lowest pressure ZT value. The results demonstrate a fundamental relationship between structure and thermoelectricmore » behaviours and suggest that pressure is an effective tool to control them.« less

  16. Giant Pressure-Induced Enhancement of Seebeck Coefficient and Thermoelectric Efficiency in SnTe

    DOE PAGES

    Baker, Jason; Kumar, Ravhi; Park, Changyong; ...

    2017-10-30

    The thermoelectric properties of polycrystalline SnTe have been measured up to 4.5 GPa at 330 K. SnTe shows an enormous enhancement in Seebeck coefficient, greater than 200 % after 3 GPa, which correlates to a known pressure-induced structural phase transition that is observed through simultaneous in situ X-ray diffraction measurement. We also measured electrical resistance and relative changes to the thermal conductivity, enabling the determination of relative changes in the dimensionless figure of merit (ZT), which increases dramatically after 3 GPa, reaching 350 % of the lowest pressure ZT value. Our results demonstrate a fundamental relationship between structure and thermoelectricmore » behaviours and suggest that pressure is an effective tool to control them.« less

  17. Hybrid thermoelectric solar collector design and analysis

    NASA Technical Reports Server (NTRS)

    Roberts, A. S., Jr.; Shaheen, K. E.

    1982-01-01

    A flat-plate solar collector is conceived where energy cascades through thermoelectric power modules generating direct-current electricity. The intent of this work was to choose a collector configuration and to perform a steady-state thermal performance assessment. A set of energy balance equations were written and solved numerically for the purpose of optimizing collector thermal and electrical performance. The collector design involves finned columns of thermoelectric modules imbedded in the absorber plate (hot junction) over a parallel array of vertical tubes. The thermoelectric power output is limited by the small hot-junction/cold-junction temperature difference which can be maintained under steady-state conditions. The electric power per unit tube pass area is found to have a maximum as a function of a geometric parameter, while electric power is maximized with respect to an electric resistance ratio. Although the electric power efficiency is small, results indicate that there is sufficient electric power production to drive a coolant circulator, suggesting the potential for a stand-alone system.

  18. Computational identification of promising thermoelectric materials among known quasi-2D binary compounds

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Gorai, Prashun; Toberer, Eric S.; Stevanović, Vladan

    Quasi low-dimensional structures are abundant among known thermoelectric materials, primarily because of their low lattice thermal conductivities. In this work, we have computationally assessed the potential of 427 known binary quasi-2D structures in 272 different chemistries for thermoelectric performance. To assess the thermoelectric performance, we employ an improved version of our previously developed descriptor for thermoelectric performance [Yan et al., Energy Environ. Sci., 2015, 8, 983]. The improvement is in the explicit treatment of van der Waals interactions in quasi-2D materials, which leads to significantly better predictions of their crystal structures and lattice thermal conductivities. The improved methodology correctly identifiesmore » known binary quasi-2D thermoelectric materials such as Sb2Te3, Bi2Te3, SnSe, SnS, InSe, and In2Se3. As a result, we propose candidate quasi-2D binary materials, a number of which have not been previously considered for thermoelectric applications.« less

  19. Recent advances in 2D thermoelectric materials

    NASA Astrophysics Data System (ADS)

    Yu, Jiabing; Sun, Qiang; Jena, Puru

    2016-12-01

    The waste heat generated by car engines, power plants, home furnaces and other fossil fuel-burning machinery play an adverse role in the climate. Development of efficient, light-weight, cost-effective, and environmentally-benign thermoelectric materials can help in converting wasted heat into useable energy, thus helping the environment. In this brief review we discuss theoretical methods that can complement experimental search for efficient thermoelectric materials. Using Boltzmann transport theory with a constant relaxation time approximation and non-equilibrium Green's function approach we study thermoelectric parameters by focusing on two dimensional materials ranging from graphene and graphdiyne to phosphorene, transition metal dichalogenides and metal carbides. In some circumstances, the reduced dimension is found to increase the Seebeck coefficient and decrease the thermal conductivity, necessary for improving thermoelectric conversion performance. We also suggest some future studies in this topic.

  20. Carbon-Nanotube-Based Thermoelectric Materials and Devices

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Blackburn, Jeffrey L.; Ferguson, Andrew J.; Cho, Chungyeon

    Conversion of waste heat to voltage has the potential to significantly reduce the carbon footprint of a number of critical energy sectors, such as the transportation and electricity-generation sectors, and manufacturing processes. Thermal energy is also an abundant low-flux source that can be harnessed to power portable/wearable electronic devices and critical components in remote off-grid locations. As such, a number of different inorganic and organic materials are being explored for their potential in thermoelectric-energy-harvesting devices. Carbon-based thermoelectric materials are particularly attractive due to their use of nontoxic, abundant source-materials, their amenability to high-throughput solution-phase fabrication routes, and the high specificmore » energy (i.e., W g-1) enabled by their low mass. Single-walled carbon nanotubes (SWCNTs) represent a unique 1D carbon allotrope with structural, electrical, and thermal properties that enable efficient thermoelectric-energy conversion. Here, the progress made toward understanding the fundamental thermoelectric properties of SWCNTs, nanotube-based composites, and thermoelectric devices prepared from these materials is reviewed in detail. This progress illuminates the tremendous potential that carbon-nanotube-based materials and composites have for producing high-performance next-generation devices for thermoelectric-energy harvesting.« less

  1. Carbon-Nanotube-Based Thermoelectric Materials and Devices

    DOE PAGES

    Blackburn, Jeffrey L.; Ferguson, Andrew J.; Cho, Chungyeon; ...

    2018-01-22

    Conversion of waste heat to voltage has the potential to significantly reduce the carbon footprint of a number of critical energy sectors, such as the transportation and electricity-generation sectors, and manufacturing processes. Thermal energy is also an abundant low-flux source that can be harnessed to power portable/wearable electronic devices and critical components in remote off-grid locations. As such, a number of different inorganic and organic materials are being explored for their potential in thermoelectric-energy-harvesting devices. Carbon-based thermoelectric materials are particularly attractive due to their use of nontoxic, abundant source-materials, their amenability to high-throughput solution-phase fabrication routes, and the high specificmore » energy (i.e., W g-1) enabled by their low mass. Single-walled carbon nanotubes (SWCNTs) represent a unique 1D carbon allotrope with structural, electrical, and thermal properties that enable efficient thermoelectric-energy conversion. Here, the progress made toward understanding the fundamental thermoelectric properties of SWCNTs, nanotube-based composites, and thermoelectric devices prepared from these materials is reviewed in detail. This progress illuminates the tremendous potential that carbon-nanotube-based materials and composites have for producing high-performance next-generation devices for thermoelectric-energy harvesting.« less

  2. Carbon-Nanotube-Based Thermoelectric Materials and Devices.

    PubMed

    Blackburn, Jeffrey L; Ferguson, Andrew J; Cho, Chungyeon; Grunlan, Jaime C

    2018-03-01

    Conversion of waste heat to voltage has the potential to significantly reduce the carbon footprint of a number of critical energy sectors, such as the transportation and electricity-generation sectors, and manufacturing processes. Thermal energy is also an abundant low-flux source that can be harnessed to power portable/wearable electronic devices and critical components in remote off-grid locations. As such, a number of different inorganic and organic materials are being explored for their potential in thermoelectric-energy-harvesting devices. Carbon-based thermoelectric materials are particularly attractive due to their use of nontoxic, abundant source-materials, their amenability to high-throughput solution-phase fabrication routes, and the high specific energy (i.e., W g -1 ) enabled by their low mass. Single-walled carbon nanotubes (SWCNTs) represent a unique 1D carbon allotrope with structural, electrical, and thermal properties that enable efficient thermoelectric-energy conversion. Here, the progress made toward understanding the fundamental thermoelectric properties of SWCNTs, nanotube-based composites, and thermoelectric devices prepared from these materials is reviewed in detail. This progress illuminates the tremendous potential that carbon-nanotube-based materials and composites have for producing high-performance next-generation devices for thermoelectric-energy harvesting. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. High Tc Superconducting Magnet Excited by a Semiconductor Thermoelectric Element

    NASA Astrophysics Data System (ADS)

    Kuriyama, T.; Ono, M.; Tabe, S.; Oguchi, A.; Okamura, T.

    2006-04-01

    A high Tc superconducting (HTS) magnet excited by a thermal electromotive force of a thermoelectric element is studied. This HTS magnet has the advantages of compactness, lightweight and continuous excitation in comparison with conventional HTS magnets, because this HTS magnet does not need a large external power source. In this system, a heat input into the cryogenic environment is necessary to excite the thermoelectric element for constant operation. This heat generation, however, causes a rise in temperature of an HTS coil and reduces the system performance. In this paper, a newly designed magnet system which adopted a two-stage GM cryocooler was investigated. It enabled us to control the temperature of a thermoelectric element and that of an HTS coil independently. The temperature of the HTS coil could be kept at 10-20 K at the second stage of the GM cryocooler, while the thermoelectric element could be excited at higher temperature in the range of 50-70 K at the first stage, where the performance of the thermoelectric element was higher. The experimental results on this HTS magnet are shown and the possibility of the thermoelectric element as a main power source of the HTS magnets is discussed.

  4. Development of Thermoelectric Power Generation and Peltier Cooling Properties of Materials for Thermoelectric Cryocooling Devices

    DTIC Science & Technology

    2015-05-12

    method. AAMU would like to continue, given future research funding, with our new design for the thermoelectric and photovoltaic systems and hybrid...nanofabrication to develop nanostructured thermoelectric (TE) materials for application in high-efficiency thermoelectric power generators and solid...Distribution Unlimited Final Report: Development of Thermoelectric Power Generation and Peltier Cooling Properties of Materials for Thermoelectric

  5. Flexible thermoelectric device to harvest waste heat from the laptop

    NASA Astrophysics Data System (ADS)

    Salhi, Imane; Belhora, Fouad; Hajjaji, Abdelowahed; Jay, Jacques; Boughaleb, Yahia

    2017-05-01

    Recovering waste heat from integrated circuits of a laptop using thermoelectricity effects seems to be an appropriate process to enhance its efficiency. Thermoelectricity, as an energy harvesting process, helps to gain on both sides: financially as it reduces the energy consumption and environmentally as it minimizes the carbon footprint. This paper presents a flexible thermoelectric generator module which is developed to harvest waste heat of the laptop to power up some external loads. First, a theoretical analysis of the system is provided where both thermal and electrical models are exposed. Second, an estimation of the power density harvested by only one thermoelectric leg is given. This estimation can reach 0.01 µW/cm2 and it is confirmed by a numerical simulation based on the finite element method. Afterwards, this power density is improved to become 0.4 µW/cm2 by adding a heat sink in the cold side showing that the thermal resistances of the air and of the heat sink play a crucial role in transferring the temperature gradient to the thermoelectric (TE) material. Finally, it is indicated that the power harvested can be enough to power up portion of the circuitry or other important micro-accessories by using numerous thermoelectric modules.

  6. Enhanced Thermoelectric Properties of Polycrystalline SnSe via LaCl₃ Doping.

    PubMed

    Li, Fu; Wang, Wenting; Ge, Zhen-Hua; Zheng, Zhuanghao; Luo, Jingting; Fan, Ping; Li, Bo

    2018-01-28

    LaCl₃ doped polycrystalline SnSe was synthesized by combining mechanical alloying (MA) process with spark plasma sintering (SPS). It is found that the electrical conductivity is enhanced after doping due to the increased carrier concentration and carrier mobility, resulting in optimization of the power factor at 750 K combing with a large Seebeck coefficient over 300 Μvk -1 . Meanwhile, all the samples exhibit lower thermal conductivity below 1.0 W/mK in the whole measured temperature. The lattice thermal conductivity for the doped samples was reduced, which effectively suppressed the increscent of the total thermal conductivity because of the improved electrical conductivity. As a result, a ZT value of 0.55 has been achieved for the composition of SnSe-1.0 wt % LaCl₃ at 750 K, which is nearly four times higher than the undoped one and reveals that rare earth element is an effective dopant for optimization of the thermoelectric properties of SnSe.

  7. Strain-induced bi-thermoelectricity in tapered carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Algharagholy, L. A. A.; Pope, T.; Lambert, C. J.

    2018-03-01

    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. These results reveal that tapered CNTs form a new class of bi-thermoelectric materials, exhibiting both positive and negative thermopower. This ability to change the sign of the Seebeck coefficient allows the thermovoltage in carbon-based thermoelectric devices to be boosted by placing CNTs with alternating-sign Seebeck coefficients in tandem.

  8. Influence of defect distribution on the thermoelectric properties of FeNbSb based materials.

    PubMed

    Guo, Shuping; Yang, Kaishuai; Zeng, Zhi; Zhang, Yongsheng

    2018-05-21

    Doping and alloying are important methodologies to improve the thermoelectric performance of FeNbSb based materials. To fully understand the influence of point defects on the thermoelectric properties, we have used density functional calculations in combination with the cluster expansion and Monte Carlo methods to examine the defect distribution behaviors in the mesoscopic FeNb1-xVxSb and FeNb1-xTixSb systems. We find that V and Ti exhibit different distribution behaviors in FeNbSb at low temperature: forming the FeNbSb-FeVSb phase separations in the FeNb1-xVxSb system but two thermodynamically stable phases in FeNb1-xTixSb. Based on the calculated effective mass and band degeneracy, it seems the doping concentration of V or Ti in FeNbSb has little effect on the electrical properties, except for one of the theoretically predicted stable Ti phases (Fe6Nb5Ti1Sb6). Thus, an essential methodology to improve the thermoelectric performance of FeNbSb should rely on phonon scattering to decrease the thermal conductivity. According to the theoretically determined phase diagrams of Fe(Nb,V)Sb and Fe(Nb,Ti)Sb, we propose the (composition, temperature) conditions for the experimental synthesis to improve the thermoelectric performance of FeNbSb based materials: lowering the experimental preparation temperature to around the phase boundary to form a mixture of the solid solution and phase separation. The point defects in the solid solution effectively scatter the short-wavelength phonons and the (coherent or incoherent) interfaces introduced by the phase separation can additionally scatter the middle-wavelength phonons to further decrease the thermal conductivity. Moreover, the induced interfaces could enhance the Seebeck coefficient as well, through the energy filtering effect. Our results give insight into the understanding of the impact of the defect distribution on the thermoelectric performance of materials and strengthen the connection between theoretical predictions and

  9. Enhanced Thermoelectric Properties of Double-Filled CoSb3 via High-Pressure Regulating.

    PubMed

    Wang, Libin; Deng, Le; Qin, Jieming; Jia, Xiaopeng

    2018-05-24

    It has been discussed for a long time that synthetic pressure can effectively optimize thermoelectric properties. The beneficial effect of synthesis pressures on thermoelectric properties has been discussed for a long time. In this paper, it is theoretically and experimentally demonstrated that appropriate synthesis pressures can increase the figure of merit (ZT) through optimizing thermal transport and electronic transport properties. Indium and barium atoms double-filled CoSb 3 samples were prepared use high-pressure and high-temperature technique for half an hour. X-ray diffraction and some structure analysis were used to reveal the relationship between microstructures and thermoelectric properties. In 0.15 Ba 0.35 Co 4 Sb 12 samples were synthesized by different pressures; sample synthesized by 3 GPa has the best electrical transport properties, and sample synthesized by 2.5 GPa has the lowest thermal conductivity. The maximum ZT value of sample synthesized by 3.0 GPa reached 1.18.

  10. Thermoelectric transport properties of high mobility organic semiconductors

    NASA Astrophysics Data System (ADS)

    Venkateshvaran, Deepak; Broch, Katharina; Warwick, Chris N.; Sirringhaus, Henning

    2016-09-01

    Transport in organic semiconductors has traditionally been investigated using measurements of the temperature and gate voltage dependent mobility of charge carriers within the channel of organic field-effect transistors (OFETs). In such measurements, the behavior of charge carrier mobility with temperature and gate voltage, studied together with carrier activation energies, provide a metric to quantify the extent of disorder within these van der Waals bonded materials. In addition to the mobility and activation energy, another potent but often-overlooked transport coefficient useful in understanding disorder is the Seebeck coefficient (also known as thermoelectric power). Fundamentally, the Seebeck coefficient represents the entropy per charge carrier in the solid state, and thus proves powerful in distinguishing materials in which charge carriers move freely from those where a high degree of disorder causes the induced carriers to remain trapped. This paper briefly covers the recent highlights in the field of organic thermoelectrics, showing how significant strides have been made both from an applied standpoint as well as from a viewpoint of fundamental thermoelectric transport physics. It shall be illustrated how thermoelectric transport parameters in organic semiconductors can be tuned over a significant range, and how this tunability facilitates an enhanced performance for heat-to-electricity conversion as well as quantifies energetic disorder and the nature of the density of states (DOS). The work of the authors shall be spotlighted in this context, illustrating how Seebeck coefficient measurements in the polymer indacenodithiophene-co-benzothiadiazole (IDTBT) known for its ultra-low degree of torsion within the polymer backbone, has a trend consistent with low disorder. 1 Finally, using examples of the small molecules C8-BTBT and C10-DNTT, it shall be discussed how the Seebeck coefficient can aid the estimation of the density and distribution of trap states

  11. Cuc(s) 0.33WO3 compound nanomaterial-incorporated thin film enhances output of thermoelectric conversion in ambient temperature environment

    NASA Astrophysics Data System (ADS)

    Cheng, Chih-Yi; Chen, Guan-Lin; Hu, Po-Sheng

    2018-03-01

    Cs0.33WO3 nanomaterial absorbs a range of near-infrared (NIR) wavelength spanning 900-2400 nm, of which the main contributor of heat energy may be utilized for electrical generation. In this research, the capability of Cs0.33WO3 nanomaterial in enhancing the output of a thermoelectric (TE) device by trapping the absorbed heat at the hot-side surface of the device is investigated. The material is synthesized through a combination of the processes of co-precipitation and wet nano-grinding, and the characterization of its structural and optical properties was carried out using X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and visible-near-infrared absorption spectroscopy. Likewise, the photothermal property of Cs0.33WO3 nanomaterial, in the form of solution or solid film, is assessed to gain better insight into its effects on the electrical output of the TE device, utilizing a laser with wavelength of 808 nm, a solar simulator, and sunlight in ambient environment. Moreover, the photoelectric property of the Cs0.33WO3 nanomaterial-incorporated TE device was evaluated in four different types of weather condition, sunny, sunny with partly cloudy, cloudy, and rainy; and our results indicate that Cs0.33WO3 nanomaterial is capable of enhancing the output of thermoelectric conversion in an ambient environment. In a complete sunny day, when compared with a bare thermoelectric device, the coating of Cs0.33WO3 nanomaterial with concentration of 0.66 wt% demonstrated a rise of 13.1% in the maximal attainable temperature and a corresponding increase of 291% in maximal output voltage.

  12. Mat-like flexible thermoelectric system based on rigid inorganic bulk materials

    NASA Astrophysics Data System (ADS)

    Park, Hwanjoo; Kim, Donggyu; Eom, Yoomin; Wijethunge, Dimuthu; Hwang, Junphil; Kim, Hoon; Kim, Woochul

    2017-12-01

    This paper reports on a mat-like flexible thermoelectric system (FTES) based on rigid inorganic bulk materials, i.e. Bi-Te compounds. Inorganic bulk materials exhibit higher thermoelectric performance and can create a larger temperature drop due to their considerable height compared with organics and printable inorganics, meaning the FTES can produce an impressive power output. We show that the FTES, wherein both a thermoelectric module and a heat sink are integrated, is flexible enough to be adapted to any irregularly shaped surface. In the FTES, p- and n-type legs composed of a thermoelectric module are placed inside holders, which are connected to one another using flexible wires. Powered by a portable battery, the FTES was used to refrigerate human skin. As a result, a temperature drop of approximately 4 K was experimentally demonstrated, which humans felt as ‘cold’ or ‘very cold’, based on analysis. This indicates the feasibility of using the proposed FTES to control the temperature of the human body, even when using a portable battery. This was also applied to body heat harvesting. The FTES generated approximately 88 µW of power, which is sufficient to operate most wearable and/or implantable sensors. Our analysis based on human thermoregulatory modeling indicates that both refrigeration and power generation capacity can be further enhanced by improving the thermal contact between the FTES and human skin. The FTES shows potential for wearable refrigeration and body heat harvesting.

  13. Superatom Thermoelectric Materials

    DTIC Science & Technology

    2012-07-30

    Superatom Thermoelectric Materials 2cd Multifunctional Materials for Defense Workshop 30 July 2012 Materials & Manufacturing Directorate AFRL...number. 1. REPORT DATE 30 JUL 2012 2. REPORT TYPE 3. DATES COVERED 00-00-2012 to 00-00-2012 4. TITLE AND SUBTITLE Superatom Thermoelectric ...Advantages of Superatoms • Fullerenes/Fullerides • Progress • Conlcusions Thermoelectric Architecture • Two materials in contact – N and P

  14. Component for thermoelectric generator

    DOEpatents

    Purdy, David L.

    1977-01-01

    In a thermoelectric generator, a component comprises a ceramic insulator, having over limited areas thereof, each area corresponding to a terminal end of thermoelectric wires, a coating of a first metal which adheres to the insulator, and an electrical thermoelectric junction including a second metal which wets said first metal and adheres to said terminal ends but does not wet said insulator, and a cloth composed of electrically insulating threads interlaced with thermoelectric wires.

  15. Higher thermoelectric performance of Zintl phases (Eu0.5Yb0.5)1-xCaxMg2Bi2 by band engineering and strain fluctuation.

    PubMed

    Shuai, Jing; Geng, Huiyuan; Lan, Yucheng; Zhu, Zhuan; Wang, Chao; Liu, Zihang; Bao, Jiming; Chu, Ching-Wu; Sui, Jiehe; Ren, Zhifeng

    2016-07-19

    Complex Zintl phases, especially antimony (Sb)-based YbZn0.4Cd1.6Sb2 with figure-of-merit (ZT) of ∼1.2 at 700 K, are good candidates as thermoelectric materials because of their intrinsic "electron-crystal, phonon-glass" nature. Here, we report the rarely studied p-type bismuth (Bi)-based Zintl phases (Ca,Yb,Eu)Mg2Bi2 with a record thermoelectric performance. Phase-pure EuMg2Bi2 is successfully prepared with suppressed bipolar effect to reach ZT ∼ 1. Further partial substitution of Eu by Ca and Yb enhanced ZT to ∼1.3 for Eu0.2Yb0.2Ca0.6Mg2Bi2 at 873 K. Density-functional theory (DFT) simulation indicates the alloying has no effect on the valence band, but does affect the conduction band. Such band engineering results in good p-type thermoelectric properties with high carrier mobility. Using transmission electron microscopy, various types of strains are observed and are believed to be due to atomic mass and size fluctuations. Point defects, strain, dislocations, and nanostructures jointly contribute to phonon scattering, confirmed by the semiclassical theoretical calculations based on a modified Debye-Callaway model of lattice thermal conductivity. This work indicates Bi-based (Ca,Yb,Eu)Mg2Bi2 is better than the Sb-based Zintl phases.

  16. Confinement- and strain-induced enhancement of thermoelectric properties in LaNiO3/LaAlO3(001 ) superlattices

    NASA Astrophysics Data System (ADS)

    Geisler, Benjamin; Pentcheva, Rossitza

    2018-05-01

    By combining ab initio simulations including an on-site Coulomb repulsion term and Boltzmann theory, we explore the thermoelectric properties of (LaNiO3)n /(LaAlO3)n (001) superlattices (n =1 ,3 ) and identify a strong dependence on confinement, spacer thickness, and epitaxial strain. While the system with n =3 shows modest values of the Seebeck coefficient and power factor, the simultaneous reduction of the LaNiO3 region and the LaAlO3 spacer thickness to single layers results in a strong enhancement, in particular of the in-plane values. This effect can be further tuned by using epitaxial strain as a control parameter: Under tensile strain corresponding to the lateral lattice constant of SrTiO3 we predict in- and cross-plane Seebeck coefficients of ±600 μ V /K and an in-plane power factor of 11 μ W /K2cm for an estimated relaxation time of τ =4 fs around room temperature. These values are comparable to some of the best performing oxide systems such as La-doped SrTiO3 or layered cobaltates and are associated with the opening of a small gap (0.29 eV) induced by the concomitant effect of octahedral tilting and Ni-site disproportionation. This establishes oxide superlattices at the verge of a metal-to-insulator transition driven by confinement and strain as promising candidates for thermoelectric materials.

  17. Enhanced magnetic and thermoelectric properties in epitaxial polycrystalline SrRuO3 thin films.

    PubMed

    Woo, Sungmin; Lee, Sang A; Mun, Hyeona; Choi, Young Gwan; Zhung, Chan June; Shin, Soohyeon; Lacotte, Morgane; David, Adrian; Prellier, Wilfrid; Park, Tuson; Kang, Won Nam; Lee, Jong Seok; Kim, Sung Wng; Choi, Woo Seok

    2018-03-01

    Transition metal oxide thin films show versatile electric, magnetic, and thermal properties which can be tailored by deliberately introducing macroscopic grain boundaries via polycrystalline solids. In this study, we focus on the modification of magnetic and thermal transport properties by fabricating single- and polycrystalline epitaxial SrRuO 3 thin films using pulsed laser epitaxy. Using the epitaxial stabilization technique with an atomically flat polycrystalline SrTiO 3 substrate, an epitaxial polycrystalline SrRuO 3 thin film with the crystalline quality of each grain comparable to that of its single-crystalline counterpart is realized. In particular, alleviated compressive strain near the grain boundaries due to coalescence is evidenced structurally, which induced the enhancement of ferromagnetic ordering of the polycrystalline epitaxial thin film. The structural variations associated with the grain boundaries further reduce the thermal conductivity without deteriorating the electronic transport, and lead to an enhanced thermoelectric efficiency in the epitaxial polycrystalline thin films, compared with their single-crystalline counterpart.

  18. Enhanced thermoelectric properties of N-type polycrystalline In4Se3-x compounds via thermally induced Se deficiency

    NASA Astrophysics Data System (ADS)

    Zhao, Ran; Shu, Yu-Tian; Guo, Fu

    2014-03-01

    In4Se3-x compound is considered as a potential thermoelectric material due to its comparably low thermal conductivity among all existing ones. While most studies investigated In4Se3-x thermoelectric properties by controlling selennium or other dopants concentrations, in the current study, it was found that even for a fixed initial In/Se ratio, the resulting In/Se ratio varied significantly with different thermal processing histories (i.e., melting and annealing), which also resulted in varied thermoelectric properties as well as fracture surface morphologies of In4Se3-x polycrystalline specimens. Single phase polycrystalline In4Se3-x compounds were synthesized by combining a sequence of melting, annealing, pulverizing, and spark plasma sintering. The extension of previous thermal history was observed to significantly improve the electrical conductivity (about 121%) and figure of merit (about 53%) of In4Se3-x polycrystalline compounds. The extended thermal history resulted in the increase of Se deficiency (x) from 0.39 to 0.53. This thermally induced Se deficiency was observed to associate with increasing carrier mobility but decreasing concentration, which differs from the general trend observed for the initially adjusted Se deficiency at room temperature. Unusually large dispersed grains with nanosize layers were observed in specimens with the longest thermal history. The mechanism(s) by which previous thermal processing enhances carrier mobility and affect microstructural evolution are briefly discussed.

  19. Note: extraction of temperature-dependent interfacial resistance of thermoelectric modules.

    PubMed

    Chen, Min

    2011-11-01

    This article discusses an approach for extracting the temperature dependency of the electrical interfacial resistance associated with thermoelectric devices. The method combines a traditional module-level test rig and a nonlinear numerical model of thermoelectricity to minimize measurement errors on the interfacial resistance. The extracted results represent useful data to investigating the characteristics of thermoelectric module resistance and comparing performance of various modules. © 2011 American Institute of Physics

  20. Thermoelectric clathrates of type I.

    PubMed

    Christensen, Mogens; Johnsen, Simon; Iversen, Bo Brummerstedt

    2010-01-28

    Thermoelectric clathrates hold significant promise for high temperature applications with zT values exceeding 1.3. The inorganic clathrates have been shown to be both chemically and thermally stable at high temperatures, and high performance can be obtained from both single crystals and processed powders. The clathrates also show excellent compatibility factors in segmented module applications. For a materials chemist it is furthermore of great importance that the clathrates exhibit a very rich chemistry with the ability for substitution of many different elements. This allows delicate tuning of both the crystal structure as well as the physical properties. With all these assets, it is not surprising that clathrates have been intensely investigated in the thermoelectric community during the past decade. The present perspective provides a review of the many studies concerned with the synthesis, crystal structure and thermoelectric properties of clathrates with emphasis on the type I clathrate.

  1. Contrasting role of antimony and bismuth dopants on the thermoelectric performance of lead selenide

    DOE PAGES

    Lee, Yeseul; Lo, Shih -Han; Chen, Changqiang; ...

    2014-05-02

    Increasing the conversion efficiency of thermoelectric materials is a key scientific driver behind a worldwide effort to enable heat to electricity power generation at competitive cost. Here we report an increased performance for antimony-doped lead selenide with a thermoelectric figure of merit of ~1.5 at 800 K. This is in sharp contrast to bismuth doped lead selenide, which reaches a figure of merit of <1. Substituting antimony or bismuth for lead achieves maximum power factors between ~23–27μW cm –1 K –2 at temperatures above 400 K. The addition of small amounts (~0.25 mol%) of antimony generates extensive nanoscale precipitates, whereasmore » comparable amounts of bismuth results in very few or no precipitates. The antimony-rich precipitates are endotaxial in lead selenide, and appear remarkably effective in reducing the lattice thermal conductivity. As a result, the corresponding bismuth-containing samples exhibit smaller reduction in lattice thermal conductivity.« less

  2. Thermoelectric properties of single-layered SnSe sheet.

    PubMed

    Wang, Fancy Qian; Zhang, Shunhong; Yu, Jiabing; Wang, Qian

    2015-10-14

    Motivated by the recent study of inspiring thermoelectric properties in bulk SnSe [Zhao et al., Nature, 2014, 508, 373] and the experimental synthesis of SnSe sheets [Chen et al., J. Am. Chem. Soc., 2013, 135, 1213], we have carried out systematic calculations for a single-layered SnSe sheet focusing on its stability, electronic structure and thermoelectric properties by using density functional theory combined with Boltzmann transport theory. We have found that the sheet is dynamically and thermally stable with a band gap of 1.28 eV, and the figure of merit (ZT) reaches 3.27 (2.76) along the armchair (zigzag) direction with optimal n-type carrier concentration, which is enhanced nearly 7 times compared to its bulk counterpart at 700 K due to quantum confinement effect. Furthermore, we designed four types of thermoelectric couples by assembling single-layered SnSe sheets with different transport directions and doping types, and found that their efficiencies are all above 13%, which are higher than those of thermoelectric couples made of commercial bulk Bi2Te3 (7%-8%), suggesting the great potential of single-layered SnSe sheets for heat-electricity conversion.

  3. Ambipolar surface state thermoelectric power of topological insulator Bi2Se3.

    PubMed

    Kim, Dohun; Syers, Paul; Butch, Nicholas P; Paglione, Johnpierre; Fuhrer, Michael S

    2014-01-01

    We measure gate-tuned thermoelectric power of mechanically exfoliated Bi2Se3 thin films in the topological insulator regime. The sign of the thermoelectric power changes across the charge neutrality point as the majority carrier type switches from electron to hole, consistent with the ambipolar electric field effect observed in conductivity and Hall effect measurements. Near the charge neutrality point and at low temperatures, the gate-dependent thermoelectric power follows the semiclassical Mott relation using the expected surface state density of states but is larger than expected at high electron doping, possibly reflecting a large density of states in the bulk gap. The thermoelectric power factor shows significant enhancement near the electron-hole puddle carrier density ∼0.5 × 10(12) cm(-2) per surface at all temperatures. Together with the expected reduction of lattice thermal conductivity in low-dimensional structures, the results demonstrate that nanostructuring and Fermi level tuning of three-dimensional topological insulators can be promising routes to realize efficient thermoelectric devices.

  4. Enhanced thermoelectric properties of n-type NbCoSn half-Heusler by improving phase purity

    DOE PAGES

    He, Ran; Huang, Lihong; Wang, Yumei; ...

    2016-06-01

    In this paper, we report the thermoelectric properties of NbCoSn-based n-type half-Heuslers (HHs) that were obtained through arc melting, ball milling, and hot pressing process. With 10% Sb substitution at the Sn site, we obtained enhanced n-type properties with a maximum power factor reaching ~35 μW cm -1 K -2 and figure of merit (ZT) value ~0.6 in NbCoSn 0.9Sb 0.1. The ZT is doubled compared to the previous report. In addition, the specific power cost ($ W -1) is decreased by ~68% comparing to HfNiSn-based n-type HH because of the elimination of Hf.

  5. Thermal Management of Vehicle Electronic Payloads Using Nanofluids and Thermoelectric Devices--Modeling and Analysis (PREPRINT)

    DTIC Science & Technology

    2011-03-01

    Transfer Engineering, Vol. 30, No. 14, pp. 1136-1150. Chang, Y.W., Chang, C.C., Ke, M.T. and Chen, S.L. (2009) ’ Thermoelectric air-cooling module for...2005) ’An assessment of module cooling enhancement with thermoelectric coolers’, Journal of Heat Transfer-Transactions of the Asme, Vol. 127, No. 1, pp...nanoparticle out outer loop p nanoparticle TEC thermoelectric module w water UNCLASSIFIED UNCLASSIFIED Page 23 of 28 Tables Table 1

  6. Thermoelectric properties of Si/CoSi2 sub-micrometer composites prepared by melt-spinning technique

    NASA Astrophysics Data System (ADS)

    Xie, Jun; Ohishi, Yuji; Ichikawa, Satoshi; Muta, Hiroaki; Kurosaki, Ken; Yamanaka, Shinsuke

    2017-05-01

    We here report on the influence of CoSi2 precipitates on the thermoelectric properties of heavily doped p-type Si. A simple self-assembly process using a melt-spinning technique followed by spark plasma sintering is introduced to prepare bulk Si/CoSi2 composites with a nominal composition of (Si0.99B0.01)95Co5. Scanning and transmission electron microscopy observations present clear evidence of a sub-micrometer CoSi2 phase with a size ranging from 50 to 500 nm. These sub-micrometer precipitates resulted in a retention of the high electrical performance of heavily doped Si, while simultaneously reducing thermal conductivity by over 20% compared to a coarse CoSi2 phase (1-10 μm) in a comparative sample prepared by arc melting and spark plasma sintering. As a result, a figure of merit ZT value of 0.21 at 1073 K was achieved in the sub-micrometer Si/CoSi2, an increase of 16% compared with the ZT value for homogeneous p-type Si with a similar carrier concentration. This suggests that the self-assembled sub-micrometer inclusions effectively enhanced the thermoelectric performance of Si-based thermoelectric materials.

  7. On-chip cooling by superlattice-based thin-film thermoelectrics.

    PubMed

    Chowdhury, Ihtesham; Prasher, Ravi; Lofgreen, Kelly; Chrysler, Gregory; Narasimhan, Sridhar; Mahajan, Ravi; Koester, David; Alley, Randall; Venkatasubramanian, Rama

    2009-04-01

    There is a significant need for site-specific and on-demand cooling in electronic, optoelectronic and bioanalytical devices, where cooling is currently achieved by the use of bulky and/or over-designed system-level solutions. Thermoelectric devices can address these limitations while also enabling energy-efficient solutions, and significant progress has been made in the development of nanostructured thermoelectric materials with enhanced figures-of-merit. However, fully functional practical thermoelectric coolers have not been made from these nanomaterials due to the enormous difficulties in integrating nanoscale materials into microscale devices and packaged macroscale systems. Here, we show the integration of thermoelectric coolers fabricated from nanostructured Bi2Te3-based thin-film superlattices into state-of-the-art electronic packages. We report cooling of as much as 15 degrees C at the targeted region on a silicon chip with a high ( approximately 1,300 W cm-2) heat flux. This is the first demonstration of viable chip-scale refrigeration technology and has the potential to enable a wide range of currently thermally limited applications.

  8. Phase Transitions of Thermoelectric TAGS-85.

    PubMed

    Kumar, Anil; Vermeulen, Paul A; Kooi, Bart J; Rao, Jiancun; van Eijck, Lambert; Schwarzmüller, Stefan; Oeckler, Oliver; Blake, Graeme R

    2017-12-18

    The alloys (GeTe) x (AgSbTe 2 ) 100-x , commonly known as TAGS-x, are among the best performing p-type thermoelectric materials for the composition range 80 ≤ x ≤ 90 and in the temperature range 200-500 °C. They adopt a rhombohedrally distorted rocksalt structure at room temperature and are reported to undergo a reversible phase transition to a cubic structure at ∼250 °C. However, we show that, for the optimal x = 85 composition (TAGS-85), both the structural and thermoelectric properties are highly sensitive to the initial synthesis method employed. Single-phase rhombohedral samples exhibit the best thermoelectric properties but can only be obtained after an annealing step at 600 °C during initial cooling from the melt. Under faster cooling conditions, the samples obtained are inhomogeneous, containing multiple rhombohedral phases with a range of lattice parameters and exhibiting inferior thermoelectric properties. We also find that when the room-temperature rhombohedral phase is heated, an intermediate trigonal structure containing ordered cation vacancy layers is formed at ∼200 °C, driven by the spontaneous precipitation of argyrodite-type Ag 8 GeTe 6 which alters the stoichiometry of the TAGS-85 matrix. The rhombohedral and trigonal phases of TAGS-85 coexist up to 380 °C, above which a single cubic phase is obtained and the Ag 8 GeTe 6 precipitates redissolve into the matrix. On subsequent cooling a mixture of rhombohedral, trigonal, and Ag 8 GeTe 6 phases is again obtained. Initially single-phase samples exhibit thermoelectric power factors of up to 0.0035 W m -1 K -2 at 500 °C, a value that is maintained on subsequent thermal cycling and which represents the highest power factor yet reported for undoped TAGS-85. Therefore, control over the structural homogeneity of TAGS-85 as demonstrated here is essential in order to optimize the thermoelectric performance.

  9. Thermoelectric Properties of SnS with Na-Doping.

    PubMed

    Zhou, Binqiang; Li, Shuai; Li, Wen; Li, Juan; Zhang, Xinyue; Lin, Siqi; Chen, Zhiwei; Pei, Yanzhong

    2017-10-04

    Tin sulfide (SnS), a low-cost compound from the IV-VI semiconductors, has attracted particular attention due to its great potential for large-scale thermoelectric applications. However, pristine SnS shows a low carrier concentration, which leads to a low thermoelectric performance. In this work, sodium is utilized to substitute Sn to increase the hole concentration and consequently improve the thermoelectric power factor. The resultant Hall carrier concentration up to ∼10 19 cm -3 is the highest concentration reported so far for this compound. This further leads to the highest thermoelectric figure of merit, zT of 0.65, reported so far in polycrystalline SnS. The temperature-dependent Hall mobility shows a transition of carrier-scattering source from a grain boundary potential below 400 K to acoustic phonons at higher temperatures. The electronic transport properties can be well understood by a single parabolic band (SPB) model, enabling a quantitative guidance for maximizing the thermoelectric power factor. Using the experimental lattice thermal conductivity, a maximal zT of 0.8 at 850 K is expected when the carrier concentration is further increased to ∼1 × 10 20 cm -3 , according to the SPB model. This work not only demonstrates SnS as a promising low-cost thermoelectric material but also details the material parameters that fundamentally determine the thermoelectric properties.

  10. THERMOELECTRIC POWER HARVESTING SYSTEMS

    EPA Science Inventory

    Energy production based on fossil fuels negatively impacts the environment and is not sustainable. Recent advances in the area of nanotechnology have lead to improved performance of direct energy conversion devices such as thermoelectric generators. However, these efforts have...

  11. Determination of Thermoelectric Module Efficiency A Survey

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Wang, Hsin; McCarty, Robin; Salvador, James R.

    2014-01-01

    The development of thermoelectrics (TE) for energy conversion is in the transition phase from laboratory research to device development. There is an increasing demand to accurately determine the module efficiency, especially for the power generation mode. For many thermoelectrics, the figure of merit, ZT, of the material sometimes cannot be fully realized at the device level. Reliable efficiency testing of thermoelectric modules is important to assess the device ZT and provide the end-users with realistic values on how much power can be generated under specific conditions. We conducted a general survey of efficiency testing devices and their performance. The resultsmore » indicated the lack of industry standards and test procedures. This study included a commercial test system and several laboratory systems. Most systems are based on the heat flow meter method and some are based on the Harman method. They are usually reproducible in evaluating thermoelectric modules. However, cross-checking among different systems often showed large errors that are likely caused by unaccounted heat loss and thermal resistance. Efficiency testing is an important area for the thermoelectric community to focus on. A follow-up international standardization effort is planned.« less

  12. The Next Generation Thermoelectric Materials

    NASA Astrophysics Data System (ADS)

    Tritt, Terry M.

    1999-11-01

    Recently there been renewed interest in materials for thermoelectric refrigeration and power generation applications.^1, 2 Many new materials and new classes of materials are being investigated for potential thermoelectric applications. An introduction to thermoelectric refrigeration and power generation, the advantages and disadvantages and potential applications will be discussed. An overview of some of the current thermoelectric materials under investigation and the criteria for selection of new materials will be given. To be promising as a thermoelectric material, a material must have a high Seebeck coefficient, α, high electrical conductivity, σ, and a low thermal conductivity, λ. These parameters go into the material's dimensionless figure of merit ZT = α ^2σT/λ. Our research at Clemson is focused on a number of new materials, quasicrystals and pentatelluride materials, which show promise for thermoelectrics and these systems will be briefly discussed. Demonstrations of thermoelectric devices will be shown and discussed. 1.) Thermoelectric Materials: New Directions and Approaches, MRS Volumes 478 and 545, edited by Terry M. Tritt et. al. 2.) G. Mahan, B. Sales and J. Sharp, Physics Today, March 50, 42, 1997

  13. Thermoelectric system

    DOEpatents

    Reiners, Eric A.; Taher, Mahmoud A.; Fei, Dong; McGilvray, Andrew N.

    2007-10-30

    In one particular embodiment, an internal combustion engine is provided. The engine comprises a block, a head, a piston, a combustion chamber defined by the block, the piston, and the head, and at least one thermoelectric device positioned between the combustion chamber and the head. In this particular embodiment, the thermoelectric device is in direct contact with the combustion chamber. In another particular embodiment, a cylinder head configured to sit atop a cylinder bank of an internal combustion engine is provided. The cylinder head comprises a cooling channel configured to receive cooling fluid, valve seats configured for receiving intake and exhaust valves, and thermoelectric devices positioned around the valve seats.

  14. Bi2O2Se nanosheet: An excellent high-temperature n-type thermoelectric material

    NASA Astrophysics Data System (ADS)

    Yu, Jiabing; Sun, Qiang

    2018-01-01

    Motivated by the recent synthesis of an ultrathin film of layered Bi2O2Se [Wu et al., Nat. Nanotechnol. 12, 530 (2017); Wu et al., Nano Lett. 17, 3021 (2017)], we have systematically studied the thermoelectric properties of a Bi2O2Se nanosheet using first principles density functional theory combined with semiclassical Boltzmann transport theory. The calculated results indicate that the Bi2O2Se nanosheet exhibits a figure of merit (ZT) of 3.35 for optimal n-type doping at 800 K, which is much larger than the ZT value of 2.6 at 923 K in SnSe known as the most efficient thermoelectric material [Zhao et al., Nature 508, 373 (2014)]. Equally important, the high ZT in the n-type doped Bi2O2Se nanosheet highlights the efficiency of the reduced dimension on improving thermoelectric performance as compared with strain engineering by which the ZT of n-type doped bulk Bi2O2Se cannot be effectively enhanced.

  15. Influence of rare earth doping on thermoelectric properties of SrTiO3 ceramics

    NASA Astrophysics Data System (ADS)

    Liu, J.; Wang, C. L.; Li, Y.; Su, W. B.; Zhu, Y. H.; Li, J. C.; Mei, L. M.

    2013-12-01

    Thermoelectric properties of SrTiO3 ceramics, doped with different rare earth elements, were investigated in this work. It's found that the ionic radius of doping elements plays an important role on thermoelectric properties: SrTiO3 ceramics doped with large rare earth ions (such as La, Nd, and Sm) exhibit large power factors, and those doped with small ions (such as Gd, Dy, Er, and Y) exhibit low thermal conductivities. Therefore, a simple approach for enhancing the thermoelectric performance of SrTiO3 ceramics is proposed: mainly doped with large ions to obtain a large power factor and, simultaneously, slightly co-doped with small ions to obtain a low thermal conductivity. Based on this rule, Sr0.8La0.18Yb0.02TiO3 ceramics were prepared, whose ZT value at 1 023 K reaches 0.31, increasing by a factor of 19% compared with the single-doped counterpart Sr0.8La0.2TiO3 (ZT = 0.26).

  16. Large thermoelectric efficiency of doped polythiophene junction: A density functional study

    NASA Astrophysics Data System (ADS)

    Golsanamlou, Zahra; Bagheri Tagani, Meysam; Rahimpour Soleimani, Hamid

    2018-06-01

    The thermoelectric properties of polythiophene (PT) coupled to the Au (111) electrodes are studied based on density functional theory with nonequilibrium Green function formalism. Specially, the effect of Li and Cl adsorbents on the thermoelectric efficiency of the PT junction is investigated in different concentrations of the dopants for two lengths of the PT. Results show that the presence of dopants can bring the structural changes in the oligomer and modify the arrangement of the molecular levels leading to the dramatic changes in the transmission spectra of the junction. Therefore, the large enhancement in thermopower and consequently figure of merit is obtained by dopants which makes the doped PT junction as a beneficial thermoelectric device.

  17. Three novel electrochemical electrodes for the fabrication of conducting polymer/SWCNTs layered nanostructures and their thermoelectric performance.

    PubMed

    Shi, Hui; Liu, Congcong; Jiang, Qinglin; Xu, Jingkun; Lu, Baoyang; Jiang, Fengxing; Zhu, Zhengyou

    2015-06-19

    Single-walled carbon nanotubes (SWCNTs), PSS/SWCNTs, and SWCNTs/ PSS nanofilms were used as working electrodes to electrodeposit polyaniline (PANI) in a mixed alcohol solution of isopropyl alcohol (IPA), boron trifluoride ethyl ether (BFEE), and polyethylene glycol (PEG). The thermoelectric (TE) performances of the resulting nanofilms were systematically investigated. SWCNTs/ PSS/PANI nanofilms showed a relatively high electrical conductivity value of 232.0 S cm(-1). The Seebeck coefficient was enhanced and exhibited the values of 33.8, 25.6, and 23.0 μV K(-1) for the SWCNTs/PANI, PEDOT:PSS/SWCNTs/PANI, and SWCNTs/ PSS/PANI films, respectively. The maximum power factor achieved was 12.3 μW m(-1) K(-2). This technique offers a facile and versatile approach to a class of layered nanostructures, and it may provide a general strategy for fabricating a new generation of conducting polymer/SWCNTs materials for further practical applications.

  18. Effect of Topology Structure on the Output Performance of an Automobile Exhaust Thermoelectric Generator

    NASA Astrophysics Data System (ADS)

    Fang, W.; Quan, S. H.; Xie, C. J.; Ran, B.; Li, X. L.; Wang, L.; Jiao, Y. T.; Xu, T. W.

    2017-05-01

    The majority of the thermal energy released in an automotive internal combustion cycle is exhausted as waste heat through the tail pipe. This paper describes an automobile exhaust thermoelectric generator (AETEG), designed to recycle automobile waste heat. A model of the output characteristics of each thermoelectric device was established by testing their open circuit voltage and internal resistance, and combining the output characteristics. To better describe the relationship, the physical model was transformed into a topological model. The connection matrix was used to describe the relationship between any two thermoelectric devices in the topological structure. Different topological structures produced different power outputs; their output power was maximised by using an iterative algorithm to optimize the series-parallel electrical topology structure. The experimental results have shown that the output power of the optimal topology structure increases by 18.18% and 29.35% versus that of a pure in-series or parallel topology, respectively, and by 10.08% versus a manually defined structure (based on user experience). The thermoelectric conversion device increased energy efficiency by 40% when compared with a traditional car.

  19. Superconducting thermoelectric generator

    DOEpatents

    Metzger, J.D.; El-Genk, M.S.

    1994-01-01

    Thermoelectricity is produced by applying a temperature differential to dissimilar electrically conducting or semiconducting materials, thereby producing a voltage that is proportional to the temperature difference. Thermoelectric generators use this effect to directly convert heat into electricity; however, presently-known generators have low efficiencies due to the production of high currents which in turn cause large resistive heating losses. Some thermoelectric generators operate at efficiencies between 4% and 7% in the 800{degrees} to 1200{degrees}C range. According to its major aspects and bradly stated, the present invention is an apparatus and method for producing electricity from heat. In particular, the invention is a thermoelectric generator that juxtaposes a superconducting material and a semiconducting material - so that the superconducting and the semiconducting materials touch - to convert heat energy into electrical energy without resistive losses in the temperature range below the critical temperature of the superconducting material. Preferably, an array of superconducting material is encased in one of several possible configurations within a second material having a high thermal conductivity, preferably a semiconductor, to form a thermoelectric generator.

  20. The 5-kwe reactor thermoelectric system summary

    NASA Technical Reports Server (NTRS)

    Vanosdol, J. H. (Editor)

    1973-01-01

    Design of the 5-kwe reactor thermoelectric system was initiated in February 1972 and extended through the conceptual design phase into the preliminary design phase. Design effort was terminated in January, 1973. This report documents the system and component requirements, design approaches, and performance and design characteristics for the 5-kwe system. Included is summary information on the reactor, radiation shields, power conversion systems, thermoelectric pump, radiator/structure, liquid metal components, and the control system.

  1. Synthesis and Characterization of Thermoelectric Oxides at Macro- and Nano-scales

    NASA Astrophysics Data System (ADS)

    Ma, Feiyue

    Thermoelectric materials can directly convert a temperature difference into electrical voltage and vice versa. Due to this unique property, thermoelectric materials are widely used in industry and scientific laboratories for temperature sensing and thermal management applications. Waste heat harvesting, another potential application of thermoelectric materials, has long been limited by the low conversion efficiency of the materials. Potential high temperature applications, such as power plant waste heat harvesting and combustion engine exhaust heat recovery, make thermoelectric oxides a very promising class of thermoelectric materials. In this thesis, the synthesis and characterization of thermoelectric oxide materials are explored. In the first part of this thesis, the measurement methodologies and instrumentation processes employed to investigate different thermoelectric properties, such as the Seebeck coefficient and carrier concentration at the bulk scale and the thermal conductivity at the nanoscale, are detailed. Existing scientific and engineering challenges associated with these measurements are also reviewed. To overcome such problems, original parts and methodologies have been designed. Three fully functional systems were ultimately developed for the characterization of macroscale thermoelectric properties as well as localized thermal conductivity. In the second part of the thesis, the synthesis of NaxCo 2O4, a thermoelectric oxide material, is discussed. Modification of both composition and structure were carried out so as to optimize the thermoelectric performance of NaxCo2O4. Nanostructuring methods, such as ball milling, electrospinning, auto-combustion synthesis, and core-shell structure fabrication, have been developed to refine the grain size of NaxCo2O4 in order to reduce its thermal conductivity. However, the structure of the nanostructured materials is very unstable at high temperature and limited improvement on thermoelectric performance is

  2. Advances in thermoelectric materials research: Looking back and moving forward.

    PubMed

    He, Jian; Tritt, Terry M

    2017-09-29

    High-performance thermoelectric materials lie at the heart of thermoelectrics, the simplest technology applicable to direct thermal-to-electrical energy conversion. In its recent 60-year history, the field of thermoelectric materials research has stalled several times, but each time it was rejuvenated by new paradigms. This article reviews several potentially paradigm-changing mechanisms enabled by defects, size effects, critical phenomena, anharmonicity, and the spin degree of freedom. These mechanisms decouple the otherwise adversely interdependent physical quantities toward higher material performance. We also briefly discuss a number of promising materials, advanced material synthesis and preparation techniques, and new opportunities. The renewable energy landscape will be reshaped if the current trend in thermoelectric materials research is sustained into the foreseeable future. Copyright © 2017 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works.

  3. Ion beam irradiation effect on thermoelectric properties of Bi2Te3 and Sb2Te3 thin films

    NASA Astrophysics Data System (ADS)

    Fu, Gaosheng; Zuo, Lei; Lian, Jie; Wang, Yongqiang; Chen, Jie; Longtin, Jon; Xiao, Zhigang

    2015-09-01

    Thermoelectric energy harvesting is a very promising application in nuclear power plants for self-maintained wireless sensors. However, the effects of intensive radiation on the performance of thermoelectric materials under relevant reactor environments such as energetic neutrons are not fully understood. In this work, radiation effects of bismuth telluride (Bi2Te3) and antimony telluride (Sb2Te3) thermoelectric thin film samples prepared by E-beam evaporation are investigated using Ne2+ ion irradiations at different fluences of 5 × 1014, 1015, 5 × 1015 and 1016 ions/cm2 with the focus on the transport and structural properties. Electrical conductivities, Seebeck coefficients and power factors are characterized as ion fluence changes. X-ray diffraction (XRD) and transmission electron microscopy (TEM) of the samples are obtained to assess how phase and microstructure influence the transport properties. Carrier concentration and Hall mobility are obtained from Hall effect measurements, which provide further insight into the electrical conductivity and Seebeck coefficient mechanisms. Positive effects of ion irradiations from Ne2+ on thermoelectric material property are observed to increase the power factor to 208% for Bi2Te3 and 337% for Sb2Te3 materials between fluence of 1 and 5 × 1015 cm2, due to the increasing of the electrical conductivity as a result of ionization radiation-enhanced crystallinity. However, under a higher fluence, 5 × 1015 cm2 in this case, the power factor starts to decrease accordingly, limiting the enhancements of thermoelectric materials properties under intensive radiation environment.

  4. Thermoelectric properties of semiconductor nanowire networks

    DOE PAGES

    Roslyak, Oleksiy; Piryatinski, Andrei

    2016-03-28

    To examine the thermoelectric (TE) properties of a semiconductor nanowire (NW) network, we propose a theoretical approach mapping the TE network on a two-port network. In contrast to a conventional single-port (i.e., resistor)network model, our model allows for large scale calculations showing convergence of TE figure of merit, ZT, with an increasing number of junctions. Using this model, numerical simulations are performed for the Bi 2Te 3 branched nanowire (BNW) and Cayley tree NW (CTNW) network. We find that the phonon scattering at the network junctions plays a dominant role in enhancing the network ZT. Specifically, disordered BNW and CTNWmore » demonstrate an order of magnitude higher ZT enhancement compared to their ordered counterparts. Formation of preferential TE pathways in CTNW makes the network effectively behave as its BNW counterpart. In conclusion, we provide formalism for simulating large scale nanowire networks hinged upon experimentally measurable TE parameters of a single T-junction.« less

  5. A Model for Predicting Thermoelectric Properties of Bi2Te3

    NASA Technical Reports Server (NTRS)

    Lee, Seungwon; VonAllmen, Paul

    2009-01-01

    A parameterized orthogonal tight-binding mathematical model of the quantum electronic structure of the bismuth telluride molecule has been devised for use in conjunction with a semiclassical transport model in predicting the thermoelectric properties of doped bismuth telluride. This model is expected to be useful in designing and analyzing Bi2Te3 thermoelectric devices, including ones that contain such nano - structures as quantum wells and wires. In addition, the understanding gained in the use of this model can be expected to lead to the development of better models that could be useful for developing other thermoelectric materials and devices having enhanced thermoelectric properties. Bi2Te3 is one of the best bulk thermoelectric materials and is widely used in commercial thermoelectric devices. Most prior theoretical studies of the thermoelectric properties of Bi2Te3 have involved either continuum models or ab-initio models. Continuum models are computationally very efficient, but do not account for atomic-level effects. Ab-initio models are atomistic by definition, but do not scale well in that computation times increase excessively with increasing numbers of atoms. The present tight-binding model bridges the gap between the well-scalable but non-atomistic continuum models and the atomistic but poorly scalable ab-initio models: The present tight-binding model is atomistic, yet also computationally efficient because of the reduced (relative to an ab-initio model) number of basis orbitals and flexible parameterization of the Hamiltonian.

  6. Correlated thermoelectrics

    NASA Astrophysics Data System (ADS)

    Zlatić, V.

    2008-05-01

    In the first part of these lecture notes we introduce the phenomenological equations for describing the heat and charge transport in thermoelectric samples. We discuss the solution obtained for various boundary conditions that are appropriate for the homogeneous and inhomogeneous thermoelectrics. In the second part we develop the formalism for a linear-response many-body description of the transport properties of correlated electrons. By properly determining the local heat-current operator we show that the Jonson-Mahan theorem applies to the Hamiltonians that are commonly used for the intermetallic compounds with Cerium, Europium and Ytterbium ions, so the various thermal-transport coefficient integrands are related by powers of frequency. We illustrate how to use this formalism by calculating the thermoelectric properties of the periodic Anderson model and, then, show that these results explain the experimental data on heavy fermions and valence fluctuators. Finally, we calculate the thermoelectric properties of the Falicov-Kimball model and use the results to explain the anomalous features of the intermetallic compounds in which one observes the valence-change transition.

  7. Thermoelectric refrigerator

    NASA Technical Reports Server (NTRS)

    Park, Brian V. (Inventor); Smith, Jr., Malcolm C. (Inventor); McGrath, Ralph D. (Inventor); Gilley, Michael D. (Inventor); Criscuolo, Lance (Inventor); Nelson, John L. (Inventor)

    1996-01-01

    A refrigerator is provided which combines the benefits of superinsulation materials with thermoelectric devices and phase change materials to provide an environmentally benign system that is energy efficient and can maintain relatively uniform temperatures for extended periods of time with relatively low electrical power requirements. The refrigerator includes a thermoelectric assembly having a thermoelectric device with a hot sink and a cold sink. The superinsulation materials include a plurality of vacuum panels. The refrigerator is formed from an enclosed structure having a door. The vacuum panels may be contained within the walls of the enclosed structure and the door. By mounting the thermoelectric assembly on the door, the manufacturer of the enclosed structure is simplified and the overall R rating of the refrigerator increased. Also an electrical motor and propellers may be mounted on the door to assist in the circulation of air to improve the efficiency of the cold sink and the hot sink. A propeller and/or impeller is preferably mounted within the refrigerator to assist in establishing the desired air circulation flow path.

  8. Excellent thermoelectricity performance of p-type SnSe along b axis

    NASA Astrophysics Data System (ADS)

    Li, Chunhong; Guo, Donglin; Li, Kejian; Shao, Bin; Chen, Dengming; Ma, Yilong; Sun, Jianchun

    2018-02-01

    The electronic and thermoelectric properties of SnSe were calculated using the first-principles calculations and the semiclassical Boltzmann theory. The accurate electronic structure (calculated by the TB-mBJ) resulted in the trend changing between the Seebeck coefficient and the electrical conductivity, which were in good agreement with the experimental data. During the Pnma phase, the maximal zT value increased from 0.32 to 1.62 as the temperature rose. During the Cmcm phase, the maximal zT value increased from 4.03 to 4.33 as the temperature rose. The theoretical investigation provided valuable insight into the relationship between the electronic structure and thermoelectric transport properties of SnSe material.

  9. Engineering of charge carriers via a two-dimensional heterostructure to enhance the thermoelectric figure of merit.

    PubMed

    Ding, Guangqian; Wang, Cong; Gao, Guoying; Yao, Kailun; Dun, Chaochao; Feng, Chunbao; Li, Dengfeng; Zhang, Gang

    2018-04-19

    High band degeneracy and glassy phonon transport are two remarkable features of highly efficient thermoelectric (TE) materials. The former promotes the power factor, while the latter aims to break the lower limit of lattice thermal conductivity through phonon scattering. Herein, we use the unique possibility offered by a two-dimensional superlattice-monolayer structure (SLM) to engineer the band degeneracy, charge density and phonon spectrum to maximize the thermoelectric figure of merit (ZT). First-principles calculations with Boltzmann transport equations reveal that the conduction bands of ZrSe2/HfSe2 SLM possess a highly degenerate level which gives a high n-type power factor; at the same time, the stair-like density of states yields a high Seebeck coefficient. These characteristics are absent in the individual monolayers. In addition, the SLM shows a suppressed lattice thermal conductivity along the superlattice period as phonons are effectively scattered by the interfaces. An intrinsic ZT of 5.3 (300 K) is achieved in n-type SLM, and it is 3.2 in the p-type counterpart. Compared with the theoretical predictions calculated with the same level of accuracy, these values are at least four-fold higher than those in the two parent materials, monolayer ZrSe2 and HfSe2. Our results provide a new strategy for the maximum thermoelectric performance, and clearly demonstrate the advantage of two-dimensional material heterostructures in the application of renewable energy.

  10. Thermoelectric properties of Bi1-xSnxCuSeO solid solutions.

    PubMed

    Yang, Yuqing; Liu, Xiaocun; Liang, Xin

    2017-02-21

    We report the enhanced thermoelectric properties of p-type BiCuSeO by tin doping on bismuth sites. Powder X-ray diffraction analysis and Hall measurements indicated effective tin doping in all samples. We found that the doping efficiency of Sn is lower than expected, as seen from the measured carrier concentration. First-principles calculations indicate that the Sn lone pair modifies the band structure at the Fermi level, with the consequent effect observed in the electrical transport and Seebeck coefficient measurements. An enhanced thermoelectric power factor of ∼2.5 μW cm -1 K -2 was reached at 773 K. No significant effect of Sn doping on the thermal conductivity was found; a thermoelectric figure of merit value (ZT) of 0.3 at 773 K is achieved for Bi 0.9 Sn 0.1 CuSeO, which is more than twice that of the pristine BiCuSeO.

  11. High Thermoelectric Power Factor of High‐Mobility 2D Electron Gas

    PubMed Central

    Kim, Sung Wng; Kaneki, Shota; Yamamoto, Atsushi

    2017-01-01

    Abstract 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 = S 2∙σ∙T∙κ−1) between 1.5 and 2. Although the power factor (PF = S 2∙σ) must also be enhanced to further improve ZT, the maximum PF remains near 1.5–4 mW m−1 K−2 due to the well‐known trade‐off relationship between S and σ. At a maximized PF, σ is much lower than the ideal value since impurity doping suppresses the carrier mobility. A metal‐oxide‐semiconductor high electron mobility transistor (MOS‐HEMT) structure on an AlGaN/GaN heterostructure is prepared. Applying a gate electric field to the MOS‐HEMT simultaneously modulates S and σ of the high‐mobility electron gas from −490 µV K−1 and ≈10−1 S cm−1 to −90 µV K−1 and ≈104 S cm−1, while maintaining a high carrier mobility (≈1500 cm2 V−1 s−1). The maximized PF of the high‐mobility electron gas is ≈9 mW m−1 K−2, which is a two‐ to sixfold increase compared to state‐of‐the‐art practical thermoelectric materials. PMID:29375980

  12. High Thermoelectric Power Factor of High-Mobility 2D Electron Gas.

    PubMed

    Ohta, Hiromichi; Kim, Sung Wng; Kaneki, Shota; Yamamoto, Atsushi; Hashizume, Tamotsu

    2018-01-01

    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 = S 2 ∙σ∙ T ∙κ -1 ) between 1.5 and 2. Although the power factor (PF = S 2 ∙σ) must also be enhanced to further improve ZT , the maximum PF remains near 1.5-4 mW m -1 K -2 due to the well-known trade-off relationship between S and σ. At a maximized PF, σ is much lower than the ideal value since impurity doping suppresses the carrier mobility. A metal-oxide-semiconductor high electron mobility transistor (MOS-HEMT) structure on an AlGaN/GaN heterostructure is prepared. Applying a gate electric field to the MOS-HEMT simultaneously modulates S and σ of the high-mobility electron gas from -490 µV K -1 and ≈10 -1 S cm -1 to -90 µV K -1 and ≈10 4 S cm -1 , while maintaining a high carrier mobility (≈1500 cm 2 V -1 s -1 ). The maximized PF of the high-mobility electron gas is ≈9 mW m -1 K -2 , which is a two- to sixfold increase compared to state-of-the-art practical thermoelectric materials.

  13. Search for thermoelectrics with high figure of merit in half-Heusler compounds with multinary substitution

    NASA Astrophysics Data System (ADS)

    Choudhary, Mukesh K.; Ravindran, P.

    2018-04-01

    In order to improve the thermoelectric performance of TiCoSb we have substituted 50% of Ti equally with Zr and Hf at Ti site and Sb with Sn and Se equally at Sb site. The electronic structure of Ti0.5Zr0.25Hf0.25CoSn0.5Se0.5 is investigated using the full potential linearized augmented plane wave method and the thermoelectric transport properties are calculated on the basis of semi-classical Boltzmann transport theory. Our band structure calculations show that Ti0.5Zr0.25Hf0.25CoSn0.5Se0.5 has semiconducting behavior with indirect band gap value of 0.98 eV which follow the empirical rule of 18 valence-electron content to bring semiconductivity in half Heusler compounds, indicating that one can have semiconducting behavior in multinary phase of half Heusler compounds if they full fill the 18 VEC rule and this open-up the possibility of designing thermoelectrics with high figure of merit in half Heusler compounds. We show that at high temperature of around 700K Ti0.5Zr0.25Hf0.25CoSn0.5Se0.5 has high thermoelectric figure of merit of ZT = 1.05 which is higher than that of TiCoSb (˜ 0.95) suggesting that by going from ternary to multinary phase system one can enhance the thermoelectric figure of merit at higher temperatures.

  14. Misfit layer compounds and ferecrystals: Model systems for thermoelectric nanocomposites

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Merrill, Devin R.; Moore, Daniel B.; Bauers, Sage R.

    A basic summary of thermoelectric principles is presented in a historical context, following the evolution of the field from initial discovery to modern day high-zT materials. A specific focus is placed on nanocomposite materials as a means to solve the challenges presented by the contradictory material requirements necessary for efficient thermal energy harvest. Misfit layer compounds are highlighted as an example of a highly ordered anisotropic nanocomposite system. Their layered structure provides the opportunity to use multiple constituents for improved thermoelectric performance, through both enhanced phonon scattering at interfaces and through electronic interactions between the constituents. Recently, a class ofmore » metastable, turbostratically-disordered misfit layer compounds has been synthesized using a kinetically controlled approach with low reaction temperatures. The kinetically stabilized structures can be prepared with a variety of constituent ratios and layering schemes, providing an avenue to systematically understand structure-function relationships not possible in the thermodynamic compounds. We summarize the work that has been done to date on these materials. The observed turbostratic disorder has been shown to result in extremely low cross plane thermal conductivity and in plane thermal conductivities that are also very small, suggesting the structural motif could be attractive as thermoelectric materials if the power factor could be improved. The first 10 compounds in the [(PbSe) 1+δ] m(TiSe₂) n family (m, n ≤ 3) are reported as a case study. As n increases, the magnitude of the Seebeck coefficient is significantly increased without a simultaneous decrease in the in-plane electrical conductivity, resulting in an improved thermoelectric power factor.« less

  15. Misfit layer compounds and ferecrystals: Model systems for thermoelectric nanocomposites

    DOE PAGES

    Merrill, Devin R.; Moore, Daniel B.; Bauers, Sage R.; ...

    2015-04-22

    A basic summary of thermoelectric principles is presented in a historical context, following the evolution of the field from initial discovery to modern day high-zT materials. A specific focus is placed on nanocomposite materials as a means to solve the challenges presented by the contradictory material requirements necessary for efficient thermal energy harvest. Misfit layer compounds are highlighted as an example of a highly ordered anisotropic nanocomposite system. Their layered structure provides the opportunity to use multiple constituents for improved thermoelectric performance, through both enhanced phonon scattering at interfaces and through electronic interactions between the constituents. Recently, a class ofmore » metastable, turbostratically-disordered misfit layer compounds has been synthesized using a kinetically controlled approach with low reaction temperatures. The kinetically stabilized structures can be prepared with a variety of constituent ratios and layering schemes, providing an avenue to systematically understand structure-function relationships not possible in the thermodynamic compounds. We summarize the work that has been done to date on these materials. The observed turbostratic disorder has been shown to result in extremely low cross plane thermal conductivity and in plane thermal conductivities that are also very small, suggesting the structural motif could be attractive as thermoelectric materials if the power factor could be improved. The first 10 compounds in the [(PbSe) 1+δ] m(TiSe₂) n family (m, n ≤ 3) are reported as a case study. As n increases, the magnitude of the Seebeck coefficient is significantly increased without a simultaneous decrease in the in-plane electrical conductivity, resulting in an improved thermoelectric power factor.« less

  16. Misfit Layer Compounds and Ferecrystals: Model Systems for Thermoelectric Nanocomposites

    PubMed Central

    Merrill, Devin R.; Moore, Daniel B.; Bauers, Sage R.; Falmbigl, Matthias; Johnson, David C.

    2015-01-01

    A basic summary of thermoelectric principles is presented in a historical context, following the evolution of the field from initial discovery to modern day high-zT materials. A specific focus is placed on nanocomposite materials as a means to solve the challenges presented by the contradictory material requirements necessary for efficient thermal energy harvest. Misfit layer compounds are highlighted as an example of a highly ordered anisotropic nanocomposite system. Their layered structure provides the opportunity to use multiple constituents for improved thermoelectric performance, through both enhanced phonon scattering at interfaces and through electronic interactions between the constituents. Recently, a class of metastable, turbostratically-disordered misfit layer compounds has been synthesized using a kinetically controlled approach with low reaction temperatures. The kinetically stabilized structures can be prepared with a variety of constituent ratios and layering schemes, providing an avenue to systematically understand structure-function relationships not possible in the thermodynamic compounds. We summarize the work that has been done to date on these materials. The observed turbostratic disorder has been shown to result in extremely low cross plane thermal conductivity and in plane thermal conductivities that are also very small, suggesting the structural motif could be attractive as thermoelectric materials if the power factor could be improved. The first 10 compounds in the [(PbSe)1+δ]m(TiSe2)n family (m, n ≤ 3) are reported as a case study. As n increases, the magnitude of the Seebeck coefficient is significantly increased without a simultaneous decrease in the in-plane electrical conductivity, resulting in an improved thermoelectric power factor. PMID:28788045

  17. Compliant Interfacial Layers in Thermoelectric Devices

    NASA Technical Reports Server (NTRS)

    Firdosy, Samad A. (Inventor); Li, Billy Chun-Yip (Inventor); Ravi, Vilupanur A. (Inventor); Fleurial, Jean-Pierre (Inventor); Caillat, Thierry (Inventor); Anjunyan, Harut (Inventor)

    2017-01-01

    A thermoelectric power generation device is disclosed using one or more mechanically compliant and thermally and electrically conductive layers at the thermoelectric material interfaces to accommodate high temperature differentials and stresses induced thereby. The compliant material may be metal foam or metal graphite composite (e.g. using nickel) and is particularly beneficial in high temperature thermoelectric generators employing Zintl thermoelectric materials. The compliant material may be disposed between the thermoelectric segments of the device or between a thermoelectric segment and the hot or cold side interconnect of the device.

  18. High Temperature Integrated Thermoelectric Ststem and Materials

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Mike S. H. Chu

    2011-06-06

    benefits. Two composition systems, specifically 1.0 SrO - 0.8 x 1.03 TiO2 - 0.2 x 1.03 NbO2.5 and 0.97 TiO2 - 0.03 NbO2.5, have been identified as good base line compositions for n-type thermoelectric compositions in future module design. Tests of these materials at an outside company were promising using that company's processing and material expertise. There was no unique p-type thermoelectric compositions identified in phase I work other than several current cobaltite materials. Ca3Co4O9 will be the primary p-type material for the future module design until alternative materials are developed. BaTiO3 and rare earth titanate based dielectric compositions show both p-type and n-type behavior even though their electrical conductivities were very low. Further research and development of these materials for thermoelectric applications is planned in the future. A preliminary modeling and optimization of a thermoelectric generator (TEG) that uses the n-type 1.0 SrO - 1.03 x 0.8 TiO2 - 1.03 x 0.2 NbO2.5 was performed. Future work will combine development of ceramic powders and manufacturing expertise at TAM, development of SPS at TAM or a partner organization, and thermoelectric material/module testing, modeling, optimization, production at several partner organizations.« less

  19. Lead telluride as a thermoelectric material for thermoelectric power generation

    NASA Astrophysics Data System (ADS)

    Dughaish, Z. H.

    2002-09-01

    The specialized applications of thermoelectric generators are very successful and have motivated a search for materials with an improved figure of merit Z, and also for materials which operate at elevated temperatures. Lead telluride, PbTe, is an intermediate thermoelectric power generator. Its maximum operating temperature is 900 K. PbTe has a high melting point, good chemical stability, low vapor pressure and good chemical strength in addition to high figure of merit Z. Recently, research in thermoelectricity aims to obtain new improved materials for autonomous sources of electrical power in specialized medical, terrestial and space applications and to obtain an unconventional energy source after the oil crises of 1974. Although the efficiency of thermoelectric generators is rather low, typically ∼5%, the other advantages, such as compactness, silent, reliability, long life, and long period of operation without attention, led to a wide range of applications. PbTe thermoelectric generators have been widely used by the US army, in space crafts to provide onboard power, and in pacemakers batteries. The general physical properties of lead telluride and factors affecting the figure of merit have been reviewed. Various possibilities of improving the figure of merit of the material have been given, including effect of grain size on reducing the lattice thermal conductivity λL. Comparison of some transport properties of lead telluride with other thermoelectric materials and procedures of preparing compacts with transport properties very close to the single crystal values from PbTe powder by cold and hot-pressing techniques are discussed.

  20. Performance Simulation of a Flat-Plate Thermoelectric Module Consisting of Square Truncated Pyramid Elements

    NASA Astrophysics Data System (ADS)

    Oki, Sae; Suzuki, Ryosuke O.

    2017-05-01

    The performance of a flat-plate thermoelectric (TE) module consisting of square truncated pyramid elements is simulated using commercial software and original TE programs. Assuming that the temperatures of both the hot and cold surfaces are constant, the performance can be varied by changing the element shape and element alignment pattern. When the angle between the edge and the base is 85° and the small square surfaces of all n-type element faces are connected to the low-temperature surface, the efficiency becomes the largest among all the 17 examined shapes and patterns. By changing the shape to match the temperature distribution, the performance of the TE module is maximized.

  1. Perovskite- and Heusler based materials for thermoelectric converters

    NASA Astrophysics Data System (ADS)

    Weidenkaff, Anke

    2015-03-01

    The broad application of thermoelectric converters in future energy technologies requires the development of active, stable, low cost and sustainable materials. Semiconductors based on perovskite and heusler structures show substantial potential for thermoelectric energy conversion processes. Their good performance can be explained based on their suitable band structure, adjusted charge carrier density, mass and mobility, limited phonon transport, electron filtering possibilities, strongly correlated electronic systems, etc. These properties are widely tuneable by following theoretical concepts and a deep composition-structure-property understanding to change the composition, structure and size of the crystallites in innovative scalable synthesis procedures. Improved thermoelectric materials are developed, synthesised and tested in diverse high temperature applications to improve the efficiency and energy density of the thermoelectric conversion process. The lecture will provide a summary on the field of advanced perovskite-type ceramics and Heusler compounds gaining importance for a large number of future energy technologies.

  2. An argyrodite-type Ag9GaSe6 liquid-like material with ultralow thermal conductivity and high thermoelectric performance.

    PubMed

    Jiang, Binbin; Qiu, Pengfei; Chen, Hongyi; Zhang, Qihao; Zhao, Kunpeng; Ren, Dudi; Shi, Xun; Chen, Lidong

    2017-10-24

    We report a ternary argyrodite-type Ag 9 GaSe 6 compound as a promising thermoelectric material in a moderate temperature range. Due to high carrier mobility and ultralow lattice thermal conductivity, a maximum ZT of 1.1 was obtained with stoichiometric Ag 9 GaSe 6 at 800 K. Via introducing slight Se-deficiency to optimize the carrier concentration, the maximum ZT is further enhanced to 1.3.

  3. Thermoelectric properties of hole-doped SrTiO3 thin films

    NASA Astrophysics Data System (ADS)

    Ferreiro-Vila, Elias; Sarantopoulos, Alexandros; Leboran, Victor; Bui, Cong-Tinh; Rivadulla, Francisco; Condense matter Chemistry Group Team

    2014-03-01

    Two dimensional conductors are expected to show an improved thermoelectric performance due the positive effect of quantum confinement on the thermoelectric power, and the decrease of thermal conductivity by interface boundary scattering. The recent report of a large increase of the thermoelectric power in quantum wells of Nb-doped SrTiO3 (STO) seems to be in agreement with this hypothesis. However, extrinsic effects like the existence of oxygen vacancies that propagate away from the interface cannot be ruled out, and the results are far from clear. Here we will show the thermoelectric properties (electrical conductivity, Seebeck coefficient, and Hall effect), of epitaxial thin-films of (La,Nb)-doped STO. The films have been deposited by PLD on different substrates (STO, LAO...) to study the effect of tensile/compressive stress on the thermoelectric properties of the system. The oxygen pressure during the deposition was carefully controlled to tune the amount of oxygen vacancies and to compare with the cation doping. We have performed a systematic study of the transport properties as a function of thickness and doping, which along with the effect of stress, allows to understand the effect of charge density and dimensionality in an oxide system with promising thermoelectric properties.

  4. Thermoelectric Polymers and their Elastic Aerogels.

    PubMed

    Khan, Zia Ullah; Edberg, Jesper; Hamedi, Mahiar Max; Gabrielsson, Roger; Granberg, Hjalmar; Wågberg, Lars; Engquist, Isak; Berggren, Magnus; Crispin, Xavier

    2016-06-01

    Electronically conducting polymers constitute an emerging class of materials for novel electronics, such as printed electronics and flexible electronics. Their properties have been further diversified to introduce elasticity, which has opened new possibility for "stretchable" electronics. Recent discoveries demonstrate that conducting polymers have thermoelectric properties with a low thermal conductivity, as well as tunable Seebeck coefficients - which is achieved by modulating their electrical conductivity via simple redox reactions. Using these thermoelectric properties, all-organic flexible thermoelectric devices, such as temperature sensors, heat flux sensors, and thermoelectric generators, are being developed. In this article we discuss the combination of the two emerging fields: stretchable electronics and polymer thermoelectrics. The combination of elastic and thermoelectric properties seems to be unique for conducting polymers, and difficult to achieve with inorganic thermoelectric materials. We introduce the basic concepts, and state of the art knowledge, about the thermoelectric properties of conducting polymers, and illustrate the use of elastic thermoelectric conducting polymer aerogels that could be employed as temperature and pressure sensors in an electronic-skin. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  5. Staircase Quantum Dots Configuration in Nanowires for Optimized Thermoelectric Power

    PubMed Central

    Li, Lijie; Jiang, Jian-Hua

    2016-01-01

    The performance of thermoelectric energy harvesters can be improved by nanostructures that exploit inelastic transport processes. One prototype is the three-terminal hopping thermoelectric device where electron hopping between quantum-dots are driven by hot phonons. Such three-terminal hopping thermoelectric devices have potential in achieving high efficiency or power via inelastic transport and without relying on heavy-elements or toxic compounds. We show in this work how output power of the device can be optimized via tuning the number and energy configuration of the quantum-dots embedded in parallel nanowires. We find that the staircase energy configuration with constant energy-step can improve the power factor over a serial connection of a single pair of quantum-dots. Moreover, for a fixed energy-step, there is an optimal length for the nanowire. Similarly for a fixed number of quantum-dots there is an optimal energy-step for the output power. Our results are important for future developments of high-performance nanostructured thermoelectric devices. PMID:27550093

  6. Prospective high thermoelectric performance of the heavily p -doped half-Heusler compound CoVSn

    DOE PAGES

    Shi, Hongliang; Ming, Wenmei; Parker, David S.; ...

    2017-05-11

    The electronic structure and transport properties of the half-Heusler compound CoVSn are studied in this paper systematically by combining first-principles electronic structure calculations and Boltzmann transport theory. The band structure at the valence-band edge is complex with multiple maxima derived from hybridized transition element d states. The result is a calculated thermopower larger than 200 μV /Κ within a wide range of doping concentrations and temperatures for heavily doped p-type CoVSn. The thermoelectric properties additionally benefit from the corrugated shapes of the hole pockets in our calculated isoenergy surfaces. Our calculated power factor S 2σ/τ (with respect to an averagemore » unknown scattering time) of CoVSn is comparable to that of FeNbSb. A smaller lattice thermal conductivity can be expected from the smaller group velocities of acoustical modes compared to FeNbSb. Finally, overall, good thermoelectric performance for CoVSn can be expected by considering the electronic transport and lattice thermal conductivity.« less

  7. Prospective high thermoelectric performance of the heavily p -doped half-Heusler compound CoVSn

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Shi, Hongliang; Ming, Wenmei; Parker, David S.

    The electronic structure and transport properties of the half-Heusler compound CoVSn are studied in this paper systematically by combining first-principles electronic structure calculations and Boltzmann transport theory. The band structure at the valence-band edge is complex with multiple maxima derived from hybridized transition element d states. The result is a calculated thermopower larger than 200 μV /Κ within a wide range of doping concentrations and temperatures for heavily doped p-type CoVSn. The thermoelectric properties additionally benefit from the corrugated shapes of the hole pockets in our calculated isoenergy surfaces. Our calculated power factor S 2σ/τ (with respect to an averagemore » unknown scattering time) of CoVSn is comparable to that of FeNbSb. A smaller lattice thermal conductivity can be expected from the smaller group velocities of acoustical modes compared to FeNbSb. Finally, overall, good thermoelectric performance for CoVSn can be expected by considering the electronic transport and lattice thermal conductivity.« less

  8. Solar thermoelectric generator

    DOEpatents

    Toberer, Eric S.; Baranowski, Lauryn L.; Warren, Emily L.

    2016-05-03

    Solar thermoelectric generators (STEGs) are solid state heat engines that generate electricity from concentrated sunlight. A novel detailed balance model for STEGs is provided and applied to both state-of-the-art and idealized materials. STEGs can produce electricity by using sunlight to heat one side of a thermoelectric generator. While concentrated sunlight can be used to achieve extremely high temperatures (and thus improved generator efficiency), the solar absorber also emits a significant amount of black body radiation. This emitted light is the dominant loss mechanism in these generators. In this invention, we propose a solution to this problem that eliminates virtually all of the emitted black body radiation. This enables solar thermoelectric generators to operate at higher efficiency and achieve said efficient with lower levels of optical concentration. The solution is suitable for both single and dual axis solar thermoelectric generators.

  9. Pressure tuning of pnicogen chalcogenide thermoelectrics

    NASA Astrophysics Data System (ADS)

    Scheidemantel, Thomas J.

    The thought of a cooling device or power generator with no moving parts seems almost a part of science fiction. Such devices do exist. They are used in a small niche of applications ranging from the cooling of individual solid state components to generating power aboard deep space telescopes. In this document, we present research that attempts to further improve and understand presently used and potentially new thermoelectric materials. To accomplish this we will use the well established technique of pressure tuning, along with first-principles calculations to study the effects of arsenic on currently used room temperature thermoelectric materials. The small size of arsenic may provide extra degrees of freedom in these currently used alloys. We found that pressure provides a route to the phase of As2Te 3 that is isostructural with the rhombohedral (R3¯ m) structures of Bi2Te3 and Sb2Te 3. The ambient pressure phase of As2Te3 is monoclinic. We also found that As2Te3 is more soluble in group V-VI alloys containing Sb2Se3 than in Bi2Te 3 or Sb2Te3 alone. We also present a new host for low-dimensional thermoelectric structures. Some thermoelectric properties are enhanced by lowering the dimensionality of some materials. Current research though uses hosts and techniques that are expensive and not feasible for scaling up to commercial levels. We present a host and some techniques that may make this up-scaling a reality.

  10. Field-effect modulation of the thermoelectric characteristics of silicon nanowires on plastic substrates.

    PubMed

    Choi, Jinyong; Jeon, Youngin; Cho, Kyoungah; Kim, Sangsig

    2016-12-02

    In this study, we demonstrate the substantial enhancement of the thermoelectric power factors of silicon nanowires (SiNWs) on plastic substrates achievable by field-effect modulation. The Seebeck coefficient and electrical conductivity are adjusted by varying the charge carrier concentration via electrical modulation with a gate voltage in the 0 to ±5 range, thus enhancing the power factors from 2.08 to 935 μW K -2 m -1 ) for n-type SiNWs, and from 453 to 944 μW K -2 m -1 ) for p-type SiNWs. The electrically modulated thermoelectric characteristics of SiNWs are analyzed and discussed.

  11. Electronic fitness function for screening semiconductors as thermoelectric materials

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Xing, Guangzong; Sun, Jifeng; Li, Yuwei

    Here, we introduce a simple but efficient electronic fitness function (EFF) that describes the electronic aspect of the thermoelectric performance. This EFF finds materials that overcome the inverse relationship between σ and S based on the complexity of the electronic structures regardless of specific origin (e.g., isosurface corrugation, valley degeneracy, heavy-light bands mixture, valley anisotropy or reduced dimensionality). This function is well suited for application in high throughput screening. We applied this function to 75 different thermoelectric and potential thermoelectric materials including full- and half-Heuslers, binary semiconductors, and Zintl phases. We find an efficient screening using this transport function. Themore » EFF identifies known high-performance p- and n-type Zintl phases and half-Heuslers. In addition, we find some previously unstudied phases with superior EFF.« less

  12. Electronic fitness function for screening semiconductors as thermoelectric materials

    DOE PAGES

    Xing, Guangzong; Sun, Jifeng; Li, Yuwei; ...

    2017-11-17

    Here, we introduce a simple but efficient electronic fitness function (EFF) that describes the electronic aspect of the thermoelectric performance. This EFF finds materials that overcome the inverse relationship between σ and S based on the complexity of the electronic structures regardless of specific origin (e.g., isosurface corrugation, valley degeneracy, heavy-light bands mixture, valley anisotropy or reduced dimensionality). This function is well suited for application in high throughput screening. We applied this function to 75 different thermoelectric and potential thermoelectric materials including full- and half-Heuslers, binary semiconductors, and Zintl phases. We find an efficient screening using this transport function. Themore » EFF identifies known high-performance p- and n-type Zintl phases and half-Heuslers. In addition, we find some previously unstudied phases with superior EFF.« less

  13. Thermoelectric Outer Planets Spacecraft (TOPS)

    NASA Technical Reports Server (NTRS)

    1973-01-01

    The research and advanced development work is reported on a ballistic-mode, outer planet spacecraft using radioisotope thermoelectric generator (RTG) power. The Thermoelectric Outer Planet Spacecraft (TOPS) project was established to provide the advanced systems technology that would allow the realistic estimates of performance, cost, reliability, and scheduling that are required for an actual flight mission. A system design of the complete RTG-powered outer planet spacecraft was made; major technical innovations of certain hardware elements were designed, developed, and tested; and reliability and quality assurance concepts were developed for long-life requirements. At the conclusion of its active phase, the TOPS Project reached its principal objectives: a development and experience base was established for project definition, and for estimating cost, performance, and reliability; an understanding of system and subsystem capabilities for successful outer planets missions was achieved. The system design answered long-life requirements with massive redundancy, controlled by on-board analysis of spacecraft performance data.

  14. Hybrid-Type Organic Thermoelectric Materials Containing Nanoparticles as a Carrier Transport Promoter

    NASA Astrophysics Data System (ADS)

    Oshima, Keisuke; Inoue, Junta; Sadakata, Shifumi; Shiraishi, Yukihide; Toshima, Naoki

    2017-05-01

    Carbon nanotubes (CNTs) have recently received much attention as thermoelectric materials. Although the carrier mobility within a single CNT is very high, the charge carrier transport between CNTs is quite slow. We have utilized nanoparticles (NPs) for promotion of the carrier transport between CNTs for improving their thermoelectric performance. Poly(vinyl chloride) (PVC) was used as a binder of the CNTs. Thus, hybrid-type organic thermoelectric materials containing the NPs were constructed from Pd NPs, CNTs, and PVC. The thermoelectric properties were slightly improved in the three-component films by only mixing the separately-prepared Pd NPs. The NPs of a polymer complex, poly(nickel 1,1,2,2-ethenetetrathiolate) (n-PETT), were also used as a charge carrier transport promoter instead of the Pd NPs to produce n-PETT/CNT/PVC hybrid films. Treatment of the three-component films with methanol produced a high thermoelectric power factor and low thermal conductivity, resulting in a high "apparent" thermoelectric performance ( ZT ˜ 0.3 near room temperature) although the thermal conductivity was measured in the through-plane direction, which is a different direction from that for the electrical conductivity.

  15. A bottom-up route to enhance thermoelectric figures of merit in graphene nanoribbons

    PubMed Central

    Sevinçli, Hâldun; Sevik, Cem; Çaın, Tahir; Cuniberti, Gianaurelio

    2013-01-01

    We propose a hybrid nano-structuring scheme for tailoring thermal and thermoelectric transport properties of graphene nanoribbons. Geometrical structuring and isotope cluster engineering are the elements that constitute the proposed scheme. Using first-principles based force constants and Hamiltonians, we show that the thermal conductance of graphene nanoribbons can be reduced by 98.8% at room temperature and the thermoelectric figure of merit, ZT, can be as high as 3.25 at T = 800 K. The proposed scheme relies on a recently developed bottom-up fabrication method, which is proven to be feasible for synthesizing graphene nanoribbons with an atomic precision. PMID:23390578

  16. High Efficiency Thermoelectric Materials and Devices

    NASA Technical Reports Server (NTRS)

    Kochergin, Vladimir (Inventor)

    2013-01-01

    Growth of thermoelectric materials in the form of quantum well super-lattices on three-dimensionally structured substrates provide the means to achieve high conversion efficiency of the thermoelectric module combined with inexpensiveness of fabrication and compatibility with large scale production. Thermoelectric devices utilizing thermoelectric materials in the form of quantum well semiconductor super-lattices grown on three-dimensionally structured substrates provide improved thermoelectric characteristics that can be used for power generation, cooling and other applications..

  17. Selection Criteria for New Materials For Thermoelectric Applications

    NASA Astrophysics Data System (ADS)

    Tritt, T. M.

    1997-11-01

    Recently there has been renewed interest in materials for thermoelectric refrigeration and power generation applications.(Terry M. Tritt, Science, 272, 1276, 1996),(G. Mahan, B. Sales and J. Sharp, Physics Today, March 50, 42, 1997) We have established a multidisciplinary program within the Physics Department and in collaboration with the Chemistry Department at Clemson University. The focus of our research utilizes a broad understanding of solid state physics coupled with solid state chemistry to synthesize and fully characterize promising materials for their potential as the "next generation" thermoelectric materials. An introduction to thermoelectric materials and the criteria for their selection and potential for applications will be given. To be promising as a thermoelectric material, a material must have a high Seebeck coefficient, α, high electrical conductivity, σ, and a low thermal conductivity, λ. These parameters go into the materials dimensionless figure of merit ZT = α^2σT/λ. We will discuss these parameters in relation to this materials performance as a potential thermoelectric material. We will also discuss some of the materials that are currently being investigated in the program at Clemson University.

  18. A Review on the Fabrication of Polymer-Based Thermoelectric Materials and Fabrication Methods

    PubMed Central

    Kamarudin, Muhammad Akmal; Sahamir, Shahrir Razey; Datta, Robi Shankar; Long, Bui Duc; Mohd Sabri, Mohd Faizul; Mohd Said, Suhana

    2013-01-01

    Thermoelectricity, by converting heat energy directly into useable electricity, offers a promising technology to convert heat from solar energy and to recover waste heat from industrial sectors and automobile exhausts. In recent years, most of the efforts have been done on improving the thermoelectric efficiency using different approaches, that is, nanostructuring, doping, molecular rattling, and nanocomposite formation. The applications of thermoelectric polymers at low temperatures, especially conducting polymers, have shown various advantages such as easy and low cost of fabrication, light weight, and flexibility. In this review, we will focus on exploring new types of polymers and the effects of different structures, concentrations, and molecular weight on thermoelectric properties. Various strategies to improve the performance of thermoelectric materials will be discussed. In addition, a discussion on the fabrication of thermoelectric devices, especially suited to polymers, will also be given. Finally, we provide the challenge and the future of thermoelectric polymers, especially thermoelectric hybrid model. PMID:24324378

  19. Three novel electrochemical electrodes for the fabrication of conducting polymer/SWCNTs layered nanostructures and their thermoelectric performance

    NASA Astrophysics Data System (ADS)

    Shi, Hui; Liu, Congcong; Jiang, Qinglin; Xu, Jingkun; Lu, Baoyang; Jiang, Fengxing; Zhu, Zhengyou

    2015-06-01

    Single-walled carbon nanotubes (SWCNTs), PEDOT:PSS/SWCNTs, and SWCNTs/PEDOT:PSS nanofilms were used as working electrodes to electrodeposit polyaniline (PANI) in a mixed alcohol solution of isopropyl alcohol (IPA), boron trifluoride ethyl ether (BFEE), and polyethylene glycol (PEG). The thermoelectric (TE) performances of the resulting nanofilms were systematically investigated. SWCNTs/PEDOT:PSS/PANI nanofilms showed a relatively high electrical conductivity value of 232.0 S cm-1. The Seebeck coefficient was enhanced and exhibited the values of 33.8, 25.6, and 23.0 μV K-1 for the SWCNTs/PANI, PEDOT:PSS/SWCNTs/PANI, and SWCNTs/PEDOT:PSS/PANI films, respectively. The maximum power factor achieved was 12.3 μW m-1 K-2. This technique offers a facile and versatile approach to a class of layered nanostructures, and it may provide a general strategy for fabricating a new generation of conducting polymer/SWCNTs materials for further practical applications.

  20. Encapsulation of high temperature thermoelectric modules

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Salvador, James R.; Sakamoto, Jeffrey; Park, Youngsam

    A method of encapsulating a thermoelectric device and its associated thermoelectric elements in an inert atmosphere and a thermoelectric device fabricated by such method are described. These thermoelectric devices may be intended for use under conditions which would otherwise promote oxidation of the thermoelectric elements. The capsule is formed by securing a suitably-sized thin-walled strip of oxidation-resistant metal to the ceramic substrates which support the thermoelectric elements. The thin-walled metal strip is positioned to enclose the edges of the thermoelectric device and is secured to the substrates using gap-filling materials. The strip, substrates and gap-filling materials cooperatively encapsulate the thermoelectricmore » elements and exclude oxygen and water vapor from atmospheric air so that the elements may be maintained in an inert, non-oxidizing environment.« less

  1. Enhanced thermoelectric performance of amorphous Nb based oxynitrides

    NASA Astrophysics Data System (ADS)

    Music, Denis; Geyer, Richard W.; Hans, Marcus

    2015-12-01

    Using density functional theory, amorphous Nb0.27Ru0.06O0.56N0.10 was designed to facilitate a combination of an enhanced Seebeck coefficient and low electrical resistivity. Based on a positive Cauchy pressure, ductile behavior is expected. To verify these predictions, the transport and mechanical properties of amorphous thin films were evaluated. Metallic electrical resistivity and the Seebeck coefficient of -94 μV K-1 are obtained, which is consistent with our predictions. As there is no crack formation, these samples can be perceived as ductile. We demonstrate that the power factor can be increased by an order of magnitude, while keeping the thermal fatigue low.

  2. Origins of enhanced thermoelectric power factor in topologically insulating Bi{sub 0.64}Sb{sub 1.36}Te{sub 3} thin films

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Liu, Wei; State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, Wuhan 430070; Chi, Hang

    2016-01-25

    In this research, we report the enhanced thermoelectric power factor in topologically insulating thin films of Bi{sub 0.64}Sb{sub 1.36}Te{sub 3} with a thickness of 6–200 nm. Measurements of scanning tunneling spectroscopy and electronic transport show that the Fermi level lies close to the valence band edge, and that the topological surface state (TSS) is electron dominated. We find that the Seebeck coefficient of the 6 nm and 15 nm thick films is dominated by the valence band, while the TSS chiefly contributes to the electrical conductivity. In contrast, the electronic transport of the reference 200 nm thick film behaves similar to bulk thermoelectric materialsmore » with low carrier concentration, implying the effect of the TSS on the electronic transport is merely prominent in the thin region. The conductivity of the 6 nm and 15 nm thick film is obviously higher than that in the 200 nm thick film owing to the highly mobile TSS conduction channel. As a consequence of the enhanced electrical conductivity and the suppressed bipolar effect in transport properties for the 6 nm thick film, an impressive power factor of about 2.0 mW m{sup −1} K{sup −2} is achieved at room temperature for this film. Further investigations of the electronic transport properties of TSS and interactions between TSS and the bulk band might result in a further improved thermoelectric power factor in topologically insulating Bi{sub 0.64}Sb{sub 1.36}Te{sub 3} thin films.« less

  3. Ionic thermoelectric gating organic transistors

    PubMed Central

    Zhao, Dan; Fabiano, Simone; Berggren, Magnus; Crispin, Xavier

    2017-01-01

    Temperature is one of the most important environmental stimuli to record and amplify. While traditional thermoelectric materials are attractive for temperature/heat flow sensing applications, their sensitivity is limited by their low Seebeck coefficient (∼100 μV K−1). Here we take advantage of the large ionic thermoelectric Seebeck coefficient found in polymer electrolytes (∼10,000 μV K−1) to introduce the concept of ionic thermoelectric gating a low-voltage organic transistor. The temperature sensing amplification of such ionic thermoelectric-gated devices is thousands of times superior to that of a single thermoelectric leg in traditional thermopiles. This suggests that ionic thermoelectric sensors offer a way to go beyond the limitations of traditional thermopiles and pyroelectric detectors. These findings pave the way for new infrared-gated electronic circuits with potential applications in photonics, thermography and electronic-skins. PMID:28139738

  4. Thermoelectric Products

    NASA Technical Reports Server (NTRS)

    1988-01-01

    Instead of bulky coils and compressors used in conventional refrigeration systems, UST design engineers drew on thermo-electric technology. UST's precision temperature chambers (PTC's) feature small thermoelectric modules that measure not much more than 1 square inch and operate on unique phenomenon of heat exchange. When electric current flows through specialized metallic crystals, heat is produced; when current direction is reversed cooling is produced.

  5. Parametric Optimization of Thermoelectric Generators for Waste Heat Recovery

    NASA Astrophysics Data System (ADS)

    Huang, Shouyuan; Xu, Xianfan

    2016-10-01

    This paper presents a methodology for design optimization of thermoelectric-based waste heat recovery systems called thermoelectric generators (TEGs). The aim is to maximize the power output from thermoelectrics which are used as add-on modules to an existing gas-phase heat exchanger, without negative impacts, e.g., maintaining a minimum heat dissipation rate from the hot side. A numerical model is proposed for TEG coupled heat transfer and electrical power output. This finite-volume-based model simulates different types of heat exchangers, i.e., counter-flow and cross-flow, for TEGs. Multiple-filled skutterudites and bismuth-telluride-based thermoelectric modules (TEMs) are applied, respectively, in higher and lower temperature regions. The response surface methodology is implemented to determine the optimized TEG size along and across the flow direction and the height of thermoelectric couple legs, and to analyze their covariance and relative sensitivity. A genetic algorithm is employed to verify the globality of the optimum. The presented method will be generally useful for optimizing heat-exchanger-based TEG performance.

  6. Thermoelectric performance of various benzo-difuran wires

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Péterfalvi, Csaba G.; Grace, Iain; Manrique, Dávid Zs.

    2014-05-07

    Using a first principles approach to electron transport, we calculate the electrical and thermoelectrical transport properties of a series of molecular wires containing benzo-difuran subunits. We demonstrate that the side groups introduce Fano resonances, the energy of which is changing with the electronegativity of selected atoms in it. We also study the relative effect of single, double, or triple bonds along the molecular backbone and find that single bonds yield the highest thermopower, approximately 22 μV/K at room temperature, which is comparable with the highest measured values for single-molecule thermopower reported to date.

  7. Realizing high figure of merit in heavy-band p-type half-Heusler thermoelectric materials.

    PubMed

    Fu, Chenguang; Bai, Shengqiang; Liu, Yintu; Tang, Yunshan; Chen, Lidong; Zhao, Xinbing; Zhu, Tiejun

    2015-09-02

    Solid-state thermoelectric technology offers a promising solution for converting waste heat to useful electrical power. Both high operating temperature and high figure of merit zT are desirable for high-efficiency thermoelectric power generation. Here we report a high zT of ∼1.5 at 1,200 K for the p-type FeNbSb heavy-band half-Heusler alloys. High content of heavier Hf dopant simultaneously optimizes the electrical power factor and suppresses thermal conductivity. Both the enhanced point-defect and electron-phonon scatterings contribute to a significant reduction in the lattice thermal conductivity. An eight couple prototype thermoelectric module exhibits a high conversion efficiency of 6.2% and a high power density of 2.2 W cm(-2) at a temperature difference of 655 K. These findings highlight the optimization strategy for heavy-band thermoelectric materials and demonstrate a realistic prospect of high-temperature thermoelectric modules based on half-Heusler alloys with low cost, excellent mechanical robustness and stability.

  8. Constructing nanoporous carbon nanotubes/Bi2Te3 composite for synchronous regulation of the electrical and thermal performances

    NASA Astrophysics Data System (ADS)

    Zhang, Qihao; Xu, Leilei; Zhou, Zhenxing; Wang, Lianjun; Jiang, Wan; Chen, Lidong

    2017-02-01

    Porous nanograined thermoelectric materials exhibit low thermal conductivity due to scattering of phonons by pores, which are favorable for thermoelectric applications. However, the benefit is not large enough to overcome the deficiency in the electrical performance. Herein, an approach is presented to reduce the thermal conductivity and synchronously enhance the electrical conductivity through constructing a nanoporous thermoelectric composite. Carbon nanotubes (CNTs) are truncated and homogeneously dispersed within the Bi2Te3 matrix by a cryogenic grinding (CG) technique for the first time, which efficiently suppress the Bi2Te3 grain growth and create nanopores with the size ranging from dozens to hundreds of nanometers. The lattice thermal conductivity is substantially decreased by broad wavelength phonon scattering resulting from nanopores, increased grain boundaries, and newly formed interfaces. Meanwhile, the electrical conductivity is improved due to the enhanced carrier mobility, which may originate from the bridging effect between the Bi2Te3 grains and CNTs. The maximum ZT is improved by almost a factor of 2 due to the simultaneous optimization of electrical and thermal performances. Our study demonstrates the superiority of constructing a bulk thermoelectric composite with nanopores by the uniform dispersion of CNTs through a CG technique for enhanced thermoelectric properties, which provides a wider approach to thermoelectric nanostructure engineering.

  9. The best thermoelectric.

    PubMed Central

    Mahan, G D; Sofo, J O

    1996-01-01

    What electronic structure provides the largest figure of merit for thermoelectric materials? To answer that question, we write the electrical conductivity, thermopower, and thermal conductivity as integrals of a single function, the transport distribution. Then we derive the mathematical function for the transport distribution, which gives the largest figure of merit. A delta-shaped transport distribution is found to maximize the thermoelectric properties. This result indicates that a narrow distribution of the energy of the electrons participating in the transport process is needed for maximum thermoelectric efficiency. Some possible realizations of this idea are discussed. PMID:11607692

  10. Complex thermoelectric materials.

    PubMed

    Snyder, G Jeffrey; Toberer, Eric S

    2008-02-01

    Thermoelectric materials, which can generate electricity from waste heat or be used as solid-state Peltier coolers, could play an important role in a global sustainable energy solution. Such a development is contingent on identifying materials with higher thermoelectric efficiency than available at present, which is a challenge owing to the conflicting combination of material traits that are required. Nevertheless, because of modern synthesis and characterization techniques, particularly for nanoscale materials, a new era of complex thermoelectric materials is approaching. We review recent advances in the field, highlighting the strategies used to improve the thermopower and reduce the thermal conductivity.

  11. Detailed Modeling and Irreversible Transfer Process Analysis of a Multi-Element Thermoelectric Generator System

    NASA Astrophysics Data System (ADS)

    Xiao, Heng; Gou, Xiaolong; Yang, Suwen

    2011-05-01

    Thermoelectric (TE) power generation technology, due to its several advantages, is becoming a noteworthy research direction. Many researchers conduct their performance analysis and optimization of TE devices and related applications based on the generalized thermoelectric energy balance equations. These generalized TE equations involve the internal irreversibility of Joule heating inside the thermoelectric device and heat leakage through the thermoelectric couple leg. However, it is assumed that the thermoelectric generator (TEG) is thermally isolated from the surroundings except for the heat flows at the cold and hot junctions. Since the thermoelectric generator is a multi-element device in practice, being composed of many fundamental TE couple legs, the effect of heat transfer between the TE couple leg and the ambient environment is not negligible. In this paper, based on basic theories of thermoelectric power generation and thermal science, detailed modeling of a thermoelectric generator taking account of the phenomenon of energy loss from the TE couple leg is reported. The revised generalized thermoelectric energy balance equations considering the effect of heat transfer between the TE couple leg and the ambient environment have been derived. Furthermore, characteristics of a multi-element thermoelectric generator with irreversibility have been investigated on the basis of the new derived TE equations. In the present investigation, second-law-based thermodynamic analysis (exergy analysis) has been applied to the irreversible heat transfer process in particular. It is found that the existence of the irreversible heat convection process causes a large loss of heat exergy in the TEG system, and using thermoelectric generators for low-grade waste heat recovery has promising potential. The results of irreversibility analysis, especially irreversible effects on generator system performance, based on the system model established in detail have guiding significance for

  12. Modeling a Thermoelectric Generator Applied to Diesel Automotive Heat Recovery

    NASA Astrophysics Data System (ADS)

    Espinosa, N.; Lazard, M.; Aixala, L.; Scherrer, H.

    2010-09-01

    Thermoelectric generators (TEGs) are outstanding devices for automotive waste heat recovery. Their packaging, lack of moving parts, and direct heat to electrical conversion are the main benefits. Usually, TEGs are modeled with a constant hot-source temperature. However, energy in exhaust gases is limited, thus leading to a temperature decrease as heat is recovered. Therefore thermoelectric properties change along the TEG, affecting performance. A thermoelectric generator composed of Mg2Si/Zn4Sb3 for high temperatures followed by Bi2Te3 for low temperatures has been modeled using engineering equation solver (EES) software. The model uses the finite-difference method with a strip-fins convective heat transfer coefficient. It has been validated on a commercial module with well-known properties. The thermoelectric connection and the number of thermoelements have been addressed as well as the optimum proportion of high-temperature material for a given thermoelectric heat exchanger. TEG output power has been estimated for a typical commercial vehicle at 90°C coolant temperature.

  13. Thermoelectric System Absorbing Waste Heat from a Steel Ladle

    NASA Astrophysics Data System (ADS)

    Lu, Baiyi; Meng, Xiangning; Zhu, Miaoyong; Suzuki, Ryosuke O.

    2018-06-01

    China's iron and steel industry has made great progress in energy savings and emission reductions with the application of many waste heat recovery technologies. However, most of the medium and low temperature waste heat and radiant waste heat has not been effectively utilized. This paper proposes a thermoelectric system that generates electricity by absorbing the radiant heat from the surface of steel ladles in a steel plant. The thermoelectric behavior of modules in this system is analyzed by a numerical simulation method. The effects of external resistance and module structure on thermoelectric performance are also discussed in the temperature range of the wall surface of a steel ladle. The results show that the wall temperature has a significant influence on the thermoelectric behavior of the module, so its uniformity and stability should be considered in practical application. The ratio of the optimum external resistance to the internal resistance of the thermoelectric module is in the range of 1.6-2.0, which indicates the importance of external load optimization for a given thermoelectric system. In addition, the output power and the conversion efficiency of the module can be significantly improved by increasing the length of the thermoelectric legs and adopting a double-layer structure. Finally, through the optimization of external resistance and structure, the power output can reach 83-304 W/m2. This system is shown to be a promising approach for energy recovery.

  14. Thermoelectric System Absorbing Waste Heat from a Steel Ladle

    NASA Astrophysics Data System (ADS)

    Lu, Baiyi; Meng, Xiangning; Zhu, Miaoyong; Suzuki, Ryosuke O.

    2018-01-01

    China's iron and steel industry has made great progress in energy savings and emission reductions with the application of many waste heat recovery technologies. However, most of the medium and low temperature waste heat and radiant waste heat has not been effectively utilized. This paper proposes a thermoelectric system that generates electricity by absorbing the radiant heat from the surface of steel ladles in a steel plant. The thermoelectric behavior of modules in this system is analyzed by a numerical simulation method. The effects of external resistance and module structure on thermoelectric performance are also discussed in the temperature range of the wall surface of a steel ladle. The results show that the wall temperature has a significant influence on the thermoelectric behavior of the module, so its uniformity and stability should be considered in practical application. The ratio of the optimum external resistance to the internal resistance of the thermoelectric module is in the range of 1.6-2.0, which indicates the importance of external load optimization for a given thermoelectric system. In addition, the output power and the conversion efficiency of the module can be significantly improved by increasing the length of the thermoelectric legs and adopting a double-layer structure. Finally, through the optimization of external resistance and structure, the power output can reach 83-304 W/m2. This system is shown to be a promising approach for energy recovery.

  15. Superior thermoelectric performance in PbTe-PbS pseudo-binary. Extremely low thermal conductivity and modulated carrier concentration

    DOE PAGES

    Wu, D.; Zhao, L. -D.; Tong, X.; ...

    2015-05-19

    Lead chalcogenides have exhibited their irreplaceable role as thermoelectric materials at the medium temperature range, owing to highly degenerate electronic bands and intrinsically low thermal conductivities. PbTe-PbS pseudo-binary has been paid extensive attentions due to the even lower thermal conductivity which originates largely from the coexistence of both alloying and phase-separated precipitations. To investigate the competition between alloying and phase separation and its pronounced effect on the thermoelectric performance in PbTe-PbS, we systematically studied Spark Plasma Sintered (SPSed), 3 at% Na- doped (PbTe) 1-x(PbS)x samples with x=10%, 15%, 20%, 25%, 30% and 35% by means of transmission electron microscopy (TEM)more » observations and theoretical calculations. Corresponding to the lowest lattice thermal conductivity as a result of the balance between point defect- and precipitates- scattering, the highest figure of merit ZT~2.3 was obtained at 923 K when PbS phase fraction x is at 20%. The consistently lower lattice thermal conductivities in SPSed samples compared with corresponding ingots, resulting from the powdering and follow-up consolidation processes, also contribute to the observed superior ZT. Notably, the onset of carrier concentration modulation ~600 K due to excessive Na’s diffusion and re-dissolution leads to the observed saturations of electrical transport properties, which is believed equally crucial to the outstanding thermoelectric performance of SPSed PbTe-PbS samples.« less

  16. Thermoelectric heat exchange element

    DOEpatents

    Callas, James J.; Taher, Mahmoud A.

    2007-08-14

    A thermoelectric heat exchange module includes a first substrate including a heat receptive side and a heat donative side and a series of undulatory pleats. The module may also include a thermoelectric material layer having a ZT value of 1.0 or more disposed on at least one of the heat receptive side and the heat donative side, and an electrical contact may be in electrical communication with the thermoelectric material layer.

  17. Nanocomposites with high thermoelectric figures of merit

    NASA Technical Reports Server (NTRS)

    Dresselhaus, Mildred (Inventor); Ren, Zhifeng (Inventor); Chen, Gang (Inventor)

    2008-01-01

    The present invention is generally directed to nanocomposite thermoelectric materials that exhibit enhanced thermoelectric properties. The nanocomposite materials include two or more components, with at least one of the components forming nano-sized structures within the composite material. The components are chosen such that thermal conductivity of the composite is decreased without substantially diminishing the composite's electrical conductivity. Suitable component materials exhibit similar electronic band structures. For example, a band-edge gap between at least one of a conduction band or a valence band of one component material and a corresponding band of the other component material at interfaces between the components can be less than about 5k.sub.BT, wherein k.sub.B is the Boltzman constant and T is an average temperature of said nanocomposite composition.

  18. Nanocomposites with High Thermoelectric Figures of Merit

    NASA Technical Reports Server (NTRS)

    Chen, Gang (Inventor); Ren, Zhifeng (Inventor); Dresselhaus, Mildred (Inventor)

    2015-01-01

    The present invention is generally directed to nanocomposite thermoelectric materials that exhibit enhanced thermoelectric properties. The nanocomposite materials include two or more components, with at least one of the components forming nano-sized structures within the composite material. The components are chosen such that thermal conductivity of the composite is decreased without substantially diminishing the composite's electrical conductivity. Suitable component materials exhibit similar electronic band structures. For example, a band-edge gap between at least one of a conduction band or a valence band of one component material and a corresponding band of the other component material at interfaces between the components can be less than about 5k(sub B)T, wherein k(sub B) is the Boltzman constant and T is an average temperature of said nanocomposite composition.

  19. Nanocomposites with high thermoelectric figures of merit

    NASA Technical Reports Server (NTRS)

    Ren, Zhifeng (Inventor); Chen, Gang (Inventor); Dresselhaus, Mildred (Inventor)

    2012-01-01

    The present invention is generally directed to nanocomposite thermoelectric materials that exhibit enhanced thermoelectric properties. The nanocomposite materials include two or more components, with at least one of the components forming nano-sized structures within the composite material. The components are chosen such that thermal conductivity of the composite is decreased without substantially diminishing the composite's electrical conductivity. Suitable component materials exhibit similar electronic band structures. For example, a band-edge gap between at least one of a conduction band or a valence band of one component material and a corresponding band of the other component material at interfaces between the components can be less than about 5k.sub.BT, wherein k.sub.B is the Boltzman constant and T is an average temperature of said nanocomposite composition.

  20. Side-Chain Effects on the Thermoelectric Properties of Fluorene-Based Copolymers.

    PubMed

    Liang, Ansheng; Zhou, Xiaoyan; Zhou, Wenqiao; Wan, Tao; Wang, Luhai; Pan, Chengjun; Wang, Lei

    2017-09-01

    Three conjugated polymers with alkyl chains of different lengths are designed and synthesized, and their structure-property relationship as organic thermoelectric materials is systematically elucidated. All three polymers show similar photophysical properties, thermal properties, and mechanical properties; however, their thermoelectric performance is influenced by the length of their side chains. The length of the alkyl chain significantly influences the electrical conductivity of the conjugated polymers, and polymers with a short alkyl chain exhibit better conductivity than those with a long alkyl chain. The length of the alkyl chain has little effect on the Seebeck coefficient. Only a slight increase in the Seebeck coefficient is observed with the increasing length of the alkyl chain. The purpose of this study is to provide comprehensive insight into fine-tuning the thermoelectric properties of conjugated polymers as a function of side-chain engineering, thereby providing a novel perspective into the design of high-performance thermoelectric conjugated polymers. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Thermoelectric Power in Bilayer Graphene Device with Ionic Liquid Gating.

    PubMed

    Chien, Yung-Yu; Yuan, Hongtao; Wang, Chang-Ran; Lee, Wei-Li

    2016-02-08

    The quest for materials showing large thermoelectric power has long been one of the important subjects in material science and technology. Such materials have great potential for thermoelectric cooling and also high figure of merit ZT thermoelectric applications. We have fabricated bilayer graphene devices with ionic-liquid gating in order to tune its band gap via application of a perpendicular electric field on a bilayer graphene. By keeping the Fermi level at charge neutral point during the cool-down, we found that the charge puddles effect can be greatly reduced and thus largely improve the transport properties at low T in graphene-based devices using ionic liquid gating. At (Vig, Vbg) = (-1 V, +23 V), a band gap of about 36.6 ± 3 meV forms, and a nearly 40% enhancement of thermoelectric power at T = 120 K is clearly observed. Our works demonstrate the feasibility of band gap tuning in a bilayer graphene using ionic liquid gating. We also remark on the significant influence of the charge puddles effect in ionic-liquid-based devices.

  2. Thermoelectric power of PrMg3

    NASA Astrophysics Data System (ADS)

    Isikawa, Yosikazu; Somiya, Kazuya; Koyanagi, Huruto; Mizushima, Toshio; Kuwai, Tomohiko; Tayama, Takashi

    2010-01-01

    PrMg3 is supposed to be one of the strongly correlated electron systems originated from the hybridization between the Pr 4f and conduction electrons, because the gigantic electronic specific heat coefficient C/T was observed at low temperatures. However, a typical behaviour of - ln T dependence was not observed in the temperature dependence of the electrical resistivity. The thermoelectric power S is a powerful tool to investigate the density of states at the Fermi energy. We measured carefully the thermoelectric power of PrMg3 in the temperature range between 2 and 300 K. S is extremely small, ranged within ±1 μV/K over the whole temperature. The value of S/T at low temperature limit was also significantly smaller than expected from the specific heat results. We therefore conclude that the density of state at the Fermi level is not enhanced in PrMg3.

  3. Thermoelectricity for future sustainable energy technologies

    NASA Astrophysics Data System (ADS)

    Weidenkaff, Anke

    2017-07-01

    Thermoelectricity is a general term for a number of effects describing the direct interconversion of heat and electricity. Thermoelectric devices are therefore promising, environmental-friendly alternatives to conventional power generators or cooling units. Since the mid-90s, research on thermoelectric properties and their applications has steadily increased. In the course of years, the development of high-temperature resistant TE materials and devices has emerged as one of the main areas of interest focusing both on basic research and practical applications. A wide range of innovative and cost-efficient material classes has been studied and their properties improved. This has also led to advances in synthesis and metrology. The paper starts out with thermoelectric history, basic effects underlying thermoelectric conversion and selected examples of application. The main part focuses on thermoelectric materials including an outline of the design rules, a review on the most common materials and the feasibility of improved future high-temperature thermoelectric converters.

  4. Analysis and Experimental Investigation of Optimum Design of Thermoelectric Cooling/Heating System for Car Seat Climate Control (CSCC)

    NASA Astrophysics Data System (ADS)

    Elarusi, Abdulmunaem; Attar, Alaa; Lee, HoSung

    2018-02-01

    The optimum design of a thermoelectric system for application in car seat climate control has been modeled and its performance evaluated experimentally. The optimum design of the thermoelectric device combining two heat exchangers was obtained by using a newly developed optimization method based on the dimensional technique. Based on the analytical optimum design results, commercial thermoelectric cooler and heat sinks were selected to design and construct the climate control heat pump. This work focuses on testing the system performance in both cooling and heating modes to ensure accurate analytical modeling. Although the analytical performance was calculated using the simple ideal thermoelectric equations with effective thermoelectric material properties, it showed very good agreement with experiment for most operating conditions.

  5. Enhancing the Thermoelectric Figure of Merit by Low-Dimensional Electrical Transport in Phonon-Glass Crystals.

    PubMed

    Mi, Xue-Ya; Yu, Xiaoxiang; Yao, Kai-Lun; Huang, Xiaoming; Yang, Nuo; Lü, Jing-Tao

    2015-08-12

    Low-dimensional electronic and glassy phononic transport are two important ingredients of highly efficient thermoelectric materials, from which two branches of thermoelectric research have emerged. One focuses on controlling electronic transport in the low dimension, while the other focuses on multiscale phonon engineering in the bulk. Recent work has benefited much from combining these two approaches, e.g., phonon engineering in low-dimensional materials. Here we propose to employ the low-dimensional electronic structure in bulk phonon-glass crystals as an alternative way to increase the thermoelectric efficiency. Through first-principles electronic structure calculations and classical molecular dynamics simulations, we show that the π-π-stacking bis(dithienothiophene) molecular crystal is a natural candidate for such an approach. This is determined by the nature of its chemical bonding. Without any optimization of the material parameters, we obtained a maximum room-temperature figure of merit, ZT, of 1.48 at optimal doping, thus validating our idea.

  6. Simulation Analysis of Tilted Polyhedron-Shaped Thermoelectric Elements

    NASA Astrophysics Data System (ADS)

    Meng, Xiangning; Suzuki, Ryosuke O.

    2015-06-01

    The generation of thermoelectricity is considered a promising approach to harness the waste heat generated in industries, automobiles, gas fields, and other man-made processes. The waste heat can be converted to electricity via a thermoelectric (TE) generator. In this light, the generator performance depends on the geometric configuration of its constituent elements as well as their material properties. Our previous work reported TE behaviors for modules consisting of parallelogram-shaped elements, because elements with tilted laminate structures provide increased mechanical stability and efficient heat-transferring ability from the hot surface to the cold surface. Here, we study TE elements in the shape of a polyhedron that is obtained by mechanically truncating the edges of a parallelogram element in order to further enhance the generator performance and reduce TE material usage. The TE performance of the modules consisting of these polyhedron elements is numerically simulated by using the finite-volume method. The output power, voltage, and current of the polyhedral TE module are greater than those of the parallelogram-element module. The polyhedron shape positively affects heat transfer and the flow of electric charges in the light of increasing the efficiency of conversion from heat to electricity. By varying the shape of the truncated portions, we determine the optimal shape that enables homogeneous heat flux distribution and slow diffusion of thermal energy to obtain the better efficiency of conversion of heat into electricity. We believe that the findings of our study can significantly contribute to the design policy in TE generation.

  7. Complex oxides useful for thermoelectric energy conversion

    DOEpatents

    Majumdar, Arunava [Orinda, CA; Ramesh, Ramamoorthy [Moraga, CA; Yu, Choongho [College Station, TX; Scullin, Matthew L [Berkeley, CA; Huijben, Mark [Enschede, NL

    2012-07-17

    The invention provides for a thermoelectric system comprising a substrate comprising a first complex oxide, wherein the substrate is optionally embedded with a second complex oxide. The thermoelectric system can be used for thermoelectric power generation or thermoelectric cooling.

  8. Effect of Cooling Units on the Performance of an Automotive Exhaust-Based Thermoelectric Generator

    NASA Astrophysics Data System (ADS)

    Su, C. Q.; Zhu, D. C.; Deng, Y. D.; Wang, Y. P.; Liu, X.

    2017-05-01

    Currently, automotive exhaust-based thermoelectric generators (AETEGs) are a hot topic in energy recovery. In order to investigate the influence of coolant flow rate, coolant flow direction and cooling unit arrangement in the AETEG, a thermoelectric generator (TEG) model and a related test bench are constructed. Water cooling is adopted in this study. Due to the non-uniformity of the surface temperature of the heat source, the coolant flow direction would affect the output performance of the TEG. Changing the volumetric flow rate of coolant can increase the output power of multi-modules connected in series or/and parallel as it can improve the temperature uniformity of the cooling unit. Since the temperature uniformity of the cooling unit has a strong influence on the output power, two cooling units are connected in series or parallel to research the effect of cooling unit arrangements on the maximum output power of the TEG. Experimental and theoretical analyses reveal that the net output power is generally higher with cooling units connected in parallel than cooling units connected in series in the cooling system with two cooling units.

  9. Enhanced Thermoelectric Properties of Polyaniline Nanofilms Induced by Self-Assembled Supramolecules.

    PubMed

    Wang, Liming; Yao, Qin; Xiao, Juanxiu; Zeng, Kaiyang; Shi, Wei; Qu, Sanyin; Chen, Lidong

    2016-07-05

    Polyaniline (PANI) is one of the most promising candidates for flexible organic thermoelectric (TE) applications owing to its relatively low cost and high stability. Herein, the self-assembled supramolecule (SAS) (3,6-dioctyldecyloxy-1,4-benzenedicarboxylic acid) was used as an additive and was introduced into PANI films as a template. Raman spectroscopy, X-ray diffraction, and conductive atomic force microscopy analyses demonstrated that the highly ordered chain structure of PANI was achieved by chemical interactions between PANI and the SAS. Moreover, the ordered regions in the PANI-SAS film increased with a decrease in the film thickness. Consequently, the TE properties of PANI-SAS films were not only much higher than those of PANI films, but they also increased with a decrease in film thickness. The maximum TE power factor of the PANI-SAS film reached 31 μW m(-1)  K(-2) , which is approximately six times higher than the power factor of a PANI film with a similar thickness. This work offers a promising way to prepare PANI thin films with enhanced TE properties. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Thermoelectric transport in Cu7PSe6 with high copper ionic mobility.

    PubMed

    Weldert, Kai S; Zeier, Wolfgang G; Day, Tristan W; Panthöfer, Martin; Snyder, G Jeffrey; Tremel, Wolfgang

    2014-08-27

    Building on the good thermoelectric performances of binary superionic compounds like Cu2Se, Ag2Se and Cu2S, a better and more detailed understanding of phonon-liquid electron-crystal (PLEC) thermoelectric materials is desirable. In this work we present the thermoelectric transport properties of the compound Cu7PSe6 as the first representative of the class of argyrodite-type ion conducting thermoelectrics. With a huge variety of possible compositions and high ionic conductivity even at room temperature, the argyrodites represent a very good model system to study structure-property relationships for PLEC thermoelectric materials. We particularly highlight the extraordinary low thermal conductivity of Cu7PSe6 below the glass limit, which can be associated with the molten copper sublattice leading to a softening of phonon modes.

  11. Validation, Optimization and Simulation of a Solar Thermoelectric Generator Model

    NASA Astrophysics Data System (ADS)

    Madkhali, Hadi Ali; Hamil, Ali; Lee, HoSung

    2017-12-01

    This study explores thermoelectrics as a viable option for small-scale solar thermal applications. Thermoelectric technology is based on the Seebeck effect, which states that a voltage is induced when a temperature gradient is applied to the junctions of two differing materials. This research proposes to analyze, validate, simulate, and optimize a prototype solar thermoelectric generator (STEG) model in order to increase efficiency. The intent is to further develop STEGs as a viable and productive energy source that limits pollution and reduces the cost of energy production. An empirical study (Kraemer et al. in Nat Mater 10:532, 2011) on the solar thermoelectric generator reported a high efficiency performance of 4.6%. The system had a vacuum glass enclosure, a flat panel (absorber), thermoelectric generator and water circulation for the cold side. The theoretical and numerical approach of this current study validated the experimental results from Kraemer's study to a high degree. The numerical simulation process utilizes a two-stage approach in ANSYS software for Fluent and Thermal-Electric Systems. The solar load model technique uses solar radiation under AM 1.5G conditions in Fluent. This analytical model applies Dr. Ho Sung Lee's theory of optimal design to improve the performance of the STEG system by using dimensionless parameters. Applying this theory, using two cover glasses and radiation shields, the STEG model can achieve a highest efficiency of 7%.

  12. Thermoelectric properties of topological insulator BaSn2

    NASA Astrophysics Data System (ADS)

    Guo, San-Dong; Qiu, Liang

    2017-01-01

    Recently, \\text{BaS}{{\\text{n}}2} has been predicted to be a strong topological insulator by the first-principle calculations. It is well known that topological insulators have a close connection to thermoelectric materials, such as the \\text{B}{{\\text{i}}2}\\text{T}{{\\text{e}}3} family. In this work, we investigate thermoelectric properties of \\text{BaS}{{\\text{n}}2} by the first-principles calculations combined with the Boltzmann transport theory. The electronic part is carried out by a modified Becke and Johnson (mBJ) exchange potential, including spin-orbit coupling (SOC), while the phonon part is performed using a generalized gradient approximation (GGA). It was found that the electronic transport coefficients between the in-plane and cross-plane directions showed strong anisotropy, while lattice-lattice thermal conductivities demonstrated almost complete isotropy. Calculated results revealed a very low lattice thermal conductivity for \\text{BaS}{{\\text{n}}2} , and the corresponding average lattice thermal conductivity at room temperature is 1.69 \\text{W}~{{\\text{m}}-1}~{{\\text{K}}-1} , which is comparable or lower than those of lead chalcogenides and bismuth-tellurium systems as classic thermoelectric materials. Due to the complicated scattering mechanism, calculating the scattering time τ is challenging. By using an empirical τ ={{10}-14} s, the n-type figure of merit ZT is greater than 0.40 in wide temperature ranges. Experimentally, it is possible to attain better thermoelectric performance by strain or tuning size parameters. This work indicates that \\text{BaS}{{\\text{n}}2} may be a potential thermoelectric material, which can stimulate further theoretical and experimental work.

  13. Integration of dye-sensitized solar cells, thermoelectric modules and electrical storage loop system to constitute a novel photothermoelectric generator.

    PubMed

    Chang, Ho; Yu, Zhi-Rong

    2012-08-01

    This study self-develops a novel type of photothermoelectric power generation modules. Dye-sensitized solar cells (DSSCs) serve as the photoelectric conversion system and a copper (Cu) heat-transfer nanofilm coating on both sides of the thermoelectric generator (TEG) acts as a thermoelectric conversion system. Thus module assembly absorbs light and generates electricity by DSSCs, and also recycles waste heat and generates power by the TEG. In addition, a set of pulsating heat pipes (PHP) filled with Cu nanofluid is placed on the cooling side to increase cooling effects and enhance the power generation efficiency. Results show that when the heat source of thermoelectric modules reaches 90 degrees C, TEG power output is increased by 85.7%. Besides, after thermoelectric modules are heated by additional heat source at 80 degrees C, the electrical energy generated by them can let a NiMH cell (1.25 V) be sufficiently charged in about 30 minutes. When photothermoelectric modules is illumined by simulated light, the temperature difference of two sides of TEG can reach 7 degrees C and the thermoelectric conversion efficiency is 2.17%. Furthermore, the power output of the thermoelectric modules is 11.48 mW/cm2, enhancing 1.4 % compared to merely using DSSCs module.

  14. Recent Progress on PEDOT-Based Thermoelectric Materials

    PubMed Central

    Wei, Qingshuo; Mukaida, Masakazu; Kirihara, Kazuhiro; Naitoh, Yasuhisa; Ishida, Takao

    2015-01-01

    The thermoelectric properties of poly(3,4-ethylenedioxythiophene) (PEDOT)-based materials have attracted attention recently because of their remarkable electrical conductivity, power factor, and figure of merit. In this review, we summarize recent efforts toward improving the thermoelectric properties of PEDOT-based materials. We also discuss thermoelectric measurement techniques and several unsolved problems with the PEDOT system such as the effect of water absorption from the air and the anisotropic thermoelectric properties. In the last part, we describe our work on improving the power output of thermoelectric modules by using PEDOT, and we outline the potential applications of polymer thermoelectric generators. PMID:28787968

  15. Recent Progress on PEDOT-Based Thermoelectric Materials.

    PubMed

    Wei, Qingshuo; Mukaida, Masakazu; Kirihara, Kazuhiro; Naitoh, Yasuhisa; Ishida, Takao

    2015-02-16

    The thermoelectric properties of poly(3,4-ethylenedioxythiophene) (PEDOT)-based materials have attracted attention recently because of their remarkable electrical conductivity, power factor, and figure of merit. In this review, we summarize recent efforts toward improving the thermoelectric properties of PEDOT-based materials. We also discuss thermoelectric measurement techniques and several unsolved problems with the PEDOT system such as the effect of water absorption from the air and the anisotropic thermoelectric properties. In the last part, we describe our work on improving the power output of thermoelectric modules by using PEDOT, and we outline the potential applications of polymer thermoelectric generators.

  16. Strategies for discovery and optimization of thermoelectric materials: Role of real objects and local fields

    NASA Astrophysics Data System (ADS)

    Zhu, Hao; Xiao, Chong

    2018-06-01

    Thermoelectric materials provide a renewable and eco-friendly solution to mitigate energy shortages and to reduce environmental pollution via direct heat-to-electricity conversion. Discovery of the novel thermoelectric materials and optimization of the state-of-the-art material systems lie at the core of the thermoelectric society, the basic concept behind these being comprehension and manipulation of the physical principles and transport properties regarding thermoelectric materials. In this mini-review, certain examples for designing high-performance bulk thermoelectric materials are presented from the perspectives of both real objects and local fields. The highlights of this topic involve the Rashba effect, Peierls distortion, local magnetic field, and local stress field, which cover several aspects in the field of thermoelectric research. We conclude with an overview of future developments in thermoelectricity.

  17. Thermoelectric properties of cobalt antimonide>-based skutterudites

    NASA Astrophysics Data System (ADS)

    Yang, Jian

    Solid state cooling and power generation based on thermoelectric principles are regarded as one of the technologies with the potential of solving the current energy crisis. Thermoelectric devices could be widely used in waste heat recovery, small scale power generation and refrigeration. It has no moving parts and is environmental friendly. The limitation to its application is due to its low efficiency. Most of the current commercialized thermoelectric materials have figure of merit (ZT) around 1. To be comparable with kitchen refrigerator, ZT≃ 3 is required at room temperature. Skutterudites have emerged as member of the novel materials, which potentially have a higher ZT. In the dissertation, my investigation will be focused on the optimization of CoSb3-based skutterudites. Starting with Co and Sb elements, CoSb3 will form through a high energy ball mill. Unfortunately, even after 20 hours, only a small percentage of the powders have transformed in into CoSb3. Then the powders will be compacted into bulk samples by DC-controlled hot press. CoSb3 single phase will form after press. Characterization of the structure and thermoelectric properties will be presented with details. The effects of synthesis conditions on thermoelectric properties of skutterudites were studied and discussed. Several possible methods of improving the ZT of N type skutterudites were applied. The highest obtained ZT thus far is ˜1.2 from Yb doped CoSb3. For a group of samples with nominal composition YbxCo4Sb12, the increased Yb concentration in our samples not only enhanced the power factor due to electron doping effect but also decreased the thermal conductivity due to a stronger rattling effect. In addition, the increased grain boundary density per unit volume due to the small grains in our bulk skutterudite materials may have also helped to enhance the phonon scattering and thus to reduce the thermal conductivity. Single and double doping methods with different combinations were also

  18. New evaluation parameter for wearable thermoelectric generators

    NASA Astrophysics Data System (ADS)

    Wijethunge, Dimuthu; Kim, Woochul

    2018-04-01

    Wearable devices constitute a key application area for thermoelectric devices. However, owing to new constraints in wearable applications, a few conventional device optimization techniques are not appropriate and material evaluation parameters, such as figure of merit (zT) and power factor (PF), tend to be inadequate. We illustrated the incompleteness of zT and PF by performing simulations and considering different thermoelectric materials. The results indicate a weak correlation between device performance and zT and PF. In this study, we propose a new evaluation parameter, zTwearable, which is better suited for wearable applications compared to conventional zT. Owing to size restrictions, gap filler based device optimization is extremely critical in wearable devices. With respect to the occasions in which gap fillers are used, expressions for power, effective thermal conductivity (keff), and optimum load electrical ratio (mopt) are derived. According to the new parameters, the thermal conductivity of the material has become much more critical now. The proposed new evaluation parameter, namely, zTwearable, is extremely useful in the selection of an appropriate thermoelectric material among various candidates prior to the commencement of the actual design process.

  19. Modeling thermoelectric transport in organic materials.

    PubMed

    Wang, Dong; Shi, Wen; Chen, Jianming; Xi, Jinyang; Shuai, Zhigang

    2012-12-28

    Thermoelectric energy converters can directly convert heat to electricity using semiconducting materials via the Seebeck effect and electricity to heat via the Peltier effect. Their efficiency depends on the dimensionless thermoelectric figure of merit of the material, which is defined as zT = S(2)σT/κ with S, σ, κ, and T being the Seebeck coefficient, electrical conductivity, thermal conductivity, and absolute temperature respectively. Organic materials for thermoelectric applications have attracted great attention. In this review, we present our recent progress made in developing theories and computational schemes to predict the thermoelectric figure of merit at the first-principles level. The methods have been applied to model thermoelectric transport in closely-packed molecular crystals and one-dimensional conducting polymer chains. The physical insight gained in these studies will help in the design of efficient organic thermoelectric materials.

  20. Measurement and simulation of thermoelectric efficiency for single leg

    NASA Astrophysics Data System (ADS)

    Hu, Xiaokai; Yamamoto, Atsushi; Ohta, Michihiro; Nishiate, Hirotaka

    2015-04-01

    Thermoelectric efficiency measurements were carried out on n-type bismuth telluride legs with the hot-side temperature at 100 and 150 °C. The electric power and heat flow were measured individually. Water coolant was utilized to maintain the cold-side temperature and to measure heat flow out of the cold side. Leg length and vacuum pressure were studied in terms of temperature difference across the leg, open-circuit voltage, internal resistance, and heat flow. Finite-element simulation on thermoelectric generation was performed in COMSOL Multiphysics, by inputting two-side temperatures and thermoelectric material properties. The open-circuit voltage and resistance were in good agreement between the measurement and simulation. Much larger heat flows were found in measurements, since they were comprised of conductive, convective, and radiative contributions. Parasitic heat flow was measured in the absence of bismuth telluride leg, and the conductive heat flow was then available. Finally, the maximum thermoelectric efficiency was derived in accordance with the electric power and the conductive heat flow.

  1. Enhanced phonon scattering by nanovoids in high thermoelectric power factor polysilicon thin films

    NASA Astrophysics Data System (ADS)

    Dunham, Marc T.; Lorenzi, Bruno; Andrews, Sean C.; Sood, Aditya; Asheghi, Mehdi; Narducci, Dario; Goodson, Kenneth E.

    2016-12-01

    The ability to tune the thermal conductivity of semiconductor materials is of interest for thermoelectric applications, in particular, for doped silicon, which can be readily integrated in electronic microstructures and have a high thermoelectric power factor. Here, we examine the impact of nanovoids on the thermal conductivity of highly doped, high-power factor polysilicon thin films using time-domain thermoreflectance. Voids are formed through ion implantation and annealing, evolving from many small (˜4 nm mean diameter) voids after 500 °C anneal to fewer, larger (˜29 nm mean diameter) voids with a constant total volume fraction after staged thermal annealing to 1000 °C. The thermal conductivity is reduced to 65% of the non-implanted reference film conductivity after implantation and 500 °C anneal, increasing with anneal temperature until fully restored after 800 °C anneal. The void size distributions are determined experimentally using small-angle and wide-angle X-ray scattering. While we believe multiple physical mechanisms are at play, we are able to corroborate the positive correlation between measurements of thermal conductivity and void size with Monte Carlo calculations and a scattering probability based on Matthiessen's rule. The data suggest an opportunity for thermal conductivity suppression combined with the high power factor for increased material zT and efficiency of nanostructured polysilicon as a thermoelectric material.

  2. Recent Development of Thermoelectric Polymers and Composites.

    PubMed

    Yao, Hongyan; Fan, Zeng; Cheng, Hanlin; Guan, Xin; Wang, Chen; Sun, Kuan; Ouyang, Jianyong

    2018-03-01

    Thermoelectric materials can be used as the active materials in thermoelectric generators and as Peltier coolers for direct energy conversion between heat and electricity. Apart from inorganic thermoelectric materials, thermoelectric polymers have been receiving great attention due to their unique advantages including low cost, high mechanical flexibility, light weight, low or no toxicity, and intrinsically low thermal conductivity. The power factor of thermoelectric polymers has been continuously rising, and the highest ZT value is more than 0.25 at room temperature. The power factor can be further improved by forming composites with nanomaterials. This article provides a review of recent developments on thermoelectric polymers and polymer composites. It focuses on the relationship between thermoelectric properties and the materials structure, including chemical structure, microstructure, dopants, and doping levels. Their thermoelectric properties can be further improved to be comparable to inorganic counterparts in the near future. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Self-Tuning n-Type Bi2(Te,Se)3/SiC Thermoelectric Nanocomposites to Realize High Performances up to 300 °C.

    PubMed

    Pan, Yu; Aydemir, Umut; Sun, Fu-Hua; Wu, Chao-Feng; Chasapis, Thomas C; Snyder, G Jeffrey; Li, Jing-Feng

    2017-11-01

    Bi 2 Te 3 thermoelectric materials are utilized for refrigeration for decades, while their application of energy harvesting requires stable thermoelectric and mechanical performances at elevated temperatures. This work reveals that a steady zT of ≈0.85 at 200 to 300 °C can be achieved by doping small amounts of copper iodide (CuI) in Bi 2 Te 2.2 Se 0.8 -silicon carbide (SiC) composites, where SiC nanodispersion enhances the flexural strength. It is found that CuI plays two important roles with atomic Cu/I dopants and CuI precipitates. The Cu/I dopants show a self-tuning behavior due to increasing solubility with increasing temperatures. The increased doping concentration increases electrical conductivity at high temperatures and effectively suppresses the intrinsic excitation. In addition, a large reduction of lattice thermal conductivity is achieved due to the "in situ" CuI nanoprecipitates acting as phonon-scattering centers. Over 60% reduction of bipolar thermal conductivity is achieved, raising the maximum useful temperature of Bi 2 Te 3 for substantially higher efficiency. For module applications, the reported materials are suitable for segmentation with a conventional ingot. This leads to high device ZT values of ≈0.9-1.0 and high efficiency up to 9.2% from 300 to 573 K, which can be of great significance for power generation from waste heat.

  4. Non-contact method for characterization of small size thermoelectric modules.

    PubMed

    Manno, Michael; Yang, Bao; Bar-Cohen, Avram

    2015-08-01

    Conventional techniques for characterization of thermoelectric performance require bringing measurement equipment into direct contact with the thermoelectric device, which is increasingly error prone as device size decreases. Therefore, the novel work presented here describes a non-contact technique, capable of accurately measuring the maximum ΔT and maximum heat pumping of mini to micro sized thin film thermoelectric coolers. The non-contact characterization method eliminates the measurement errors associated with using thermocouples and traditional heat flux sensors to test small samples and large heat fluxes. Using the non-contact approach, an infrared camera, rather than thermocouples, measures the temperature of the hot and cold sides of the device to determine the device ΔT and a laser is used to heat to the cold side of the thermoelectric module to characterize its heat pumping capacity. As a demonstration of the general applicability of the non-contact characterization technique, testing of a thin film thermoelectric module is presented and the results agree well with those published in the literature.

  5. Study of the Performances of a Thermoelectric Generator Based on a Catalytic Meso-Scale H₂/C₃H₈ Fueled Combustor.

    PubMed

    Abedi, Hossein; Merotto, Laura; Fanciulli, Carlo; Donde, Roberto; De Luliis, Silvana; Passaretti, Francesca

    2017-03-01

    In this work the thermoelectric generator (TEG) based on catalytic combustion already developed in our lab has been further investigated and improved. The system made of two thermoelectric (TE) modules coupled with a catalytic combustor has been used in this work to obtain higher overall efficiency by adding hydrogen to the fuel mixture. Since implementation of hydrogen as a fuel has shown low and stable combustion temperature in literature, it is expected to achieve good overall efficiency of TEG. Moreover, hydrogen can be used to improve the system inducing self-ignition. Focus of the present work is the implementation of different mixture proportions, varying the amount of hydrogen, and the investigation of their effects on the overall efficiency. The overall TEG efficiency, has been evaluated by parallel characterization of thermoelectric modules and exhaust gases composition. The system performances have been characterized using different mixtures: the results indicate that addition of H₂ to the fuel contribute to increase the chemical and overall TEG efficiency respect to previous work, producing up to 5.92 W of electrical power. Finally, the effects of H₂ for on self-ignition conditions have been investigated finding the minimum H₂ amount for different gas flow rates.

  6. Realizing high figure of merit in heavy-band p-type half-Heusler thermoelectric materials

    PubMed Central

    Fu, Chenguang; Bai, Shengqiang; Liu, Yintu; Tang, Yunshan; Chen, Lidong; Zhao, Xinbing; Zhu, Tiejun

    2015-01-01

    Solid-state thermoelectric technology offers a promising solution for converting waste heat to useful electrical power. Both high operating temperature and high figure of merit zT are desirable for high-efficiency thermoelectric power generation. Here we report a high zT of ∼1.5 at 1,200 K for the p-type FeNbSb heavy-band half-Heusler alloys. High content of heavier Hf dopant simultaneously optimizes the electrical power factor and suppresses thermal conductivity. Both the enhanced point-defect and electron–phonon scatterings contribute to a significant reduction in the lattice thermal conductivity. An eight couple prototype thermoelectric module exhibits a high conversion efficiency of 6.2% and a high power density of 2.2 W cm−2 at a temperature difference of 655 K. These findings highlight the optimization strategy for heavy-band thermoelectric materials and demonstrate a realistic prospect of high-temperature thermoelectric modules based on half-Heusler alloys with low cost, excellent mechanical robustness and stability. PMID:26330371

  7. Thermoelectric Energy Conversion: Future Directions and Technology Development Needs

    NASA Technical Reports Server (NTRS)

    Fleurial, Jean-Pierre

    2007-01-01

    This viewgraph presentation reviews the process of thermoelectric energy conversion along with key technology needs and challenges. The topics include: 1) The Case for Thermoelectrics; 2) Advances in Thermoelectrics: Investment Needed; 3) Current U.S. Investment (FY07); 4) Increasing Thermoelectric Materials Conversion Efficiency Key Science Needs and Challenges; 5) Developing Advanced TE Components & Systems Key Technology Needs and Challenges; 6) Thermoelectrics; 7) 200W Class Lightweight Portable Thermoelectric Generator; 8) Hybrid Absorption Cooling/TE Power Cogeneration System; 9) Major Opportunities in Energy Industry; 10) Automobile Waste Heat Recovery; 11) Thermoelectrics at JPL; 12) Recent Advances at JPL in Thermoelectric Converter Component Technologies; 13) Thermoelectrics Background on Power Generation and Cooling Operational Modes; 14) Thermoelectric Power Generation; and 15) Thermoelectric Cooling.

  8. Decreasing the Effective Thermal Conductivity in Glass Supported Thermoelectric Layers.

    PubMed

    Bethke, Kevin; Andrei, Virgil; Rademann, Klaus

    2016-01-01

    As thermoelectric devices begin to make their way into commercial applications, the emphasis is put on decreasing the thermal conductivity. In this purely theoretical study, finite element analysis is used to determine the effect of a supporting material on the thermal conductivity of a thermoelectric module. The simulations illustrate the heat transfer along a sample, consisting from Cu, Cu2O and PbTe thermoelectric layers on a 1 mm thick Pyrex glass substrate. The influence of two different types of heating, at a constant temperature and at a constant heat flux, is also investigated. It is revealed that the presence of a supporting material plays an important role on lowering the effective thermal conductivity of the layer-substrate ensemble. By using thinner thermoelectric layers the effective thermal conductivity is further reduced, almost down to the value of the glass substrate. As a result, the temperature gradient becomes steeper for a fixed heating temperature, which allows the production of devices with improved performance under certain conditions. Based on the simulation results, we also propose a model for a robust thin film thermoelectric device. With this suggestion, we invite the thermoelectric community to prove the applicability of the presented concept for practical purposes.

  9. Decreasing the Effective Thermal Conductivity in Glass Supported Thermoelectric Layers

    PubMed Central

    Bethke, Kevin; Andrei, Virgil; Rademann, Klaus

    2016-01-01

    As thermoelectric devices begin to make their way into commercial applications, the emphasis is put on decreasing the thermal conductivity. In this purely theoretical study, finite element analysis is used to determine the effect of a supporting material on the thermal conductivity of a thermoelectric module. The simulations illustrate the heat transfer along a sample, consisting from Cu, Cu2O and PbTe thermoelectric layers on a 1 mm thick Pyrex glass substrate. The influence of two different types of heating, at a constant temperature and at a constant heat flux, is also investigated. It is revealed that the presence of a supporting material plays an important role on lowering the effective thermal conductivity of the layer-substrate ensemble. By using thinner thermoelectric layers the effective thermal conductivity is further reduced, almost down to the value of the glass substrate. As a result, the temperature gradient becomes steeper for a fixed heating temperature, which allows the production of devices with improved performance under certain conditions. Based on the simulation results, we also propose a model for a robust thin film thermoelectric device. With this suggestion, we invite the thermoelectric community to prove the applicability of the presented concept for practical purposes. PMID:26982458

  10. Functionalized Poly(3,4-ethylenedioxy bithiophene) Films for Tuning Electrochromic and Thermoelectric Properties.

    PubMed

    Hu, Yongjing; Liu, Xiaofang; Jiang, Fengxing; Zhou, Weiqiang; Liu, Congcong; Duan, Xuemin; Xu, Jingkun

    2017-10-05

    Conductive thiophene-based polymers have garnered great attention for use in organic electron materials such as electrochromic and thermoelectric materials. However, they suffer from poor electron transport properties and long-term stability, leading to limited development eventually. Here, we proposed a strategy of functionalized thiophene-based polymers with oligo(ethylene glycol) or alkyl side chains and synthesized a series of poly(3,4-ethylenedioxy bithiophene)s (PEDTs) to tune their electrochromic and thermoelectric properties. An alkyl group bearing electronic ability at the thiophene ring effectively achieved a large increase in the electrical conductivity with nearly invariable Seebeck coefficient, resulting in an enhancement by 1 order of magnitude for the thermoelectric power factor. Moreover, the electrochromic properties of functionalized PEDTs gained an effective improvement in the optical contrast and coloration efficiency as well as stability with multicolor changes between neutral and oxidized states. The functionalized PEDTs can be proposed as an alternative strategy to tune the electrochromic and thermoelectric properties for organic polymer materials.

  11. Electronic and thermal transport study of sinusoidally corrugated nanowires aiming to improve thermoelectric efficiency.

    PubMed

    Park, K H; Martin, P N; Ravaioli, U

    2016-01-22

    Improvement of thermoelectric efficiency has been very challenging in the solid-state industry due to the interplay among transport coefficients which measure the efficiency. In this work, we modulate the geometry of nanowires to interrupt thermal transport with causing only a minimal impact on electronic transport properties, thereby maximizing the thermoelectric power generation. As it is essential to scrutinize comprehensively both electronic and thermal transport behaviors for nano-scale thermoelectric devices, we investigate the Seebeck coefficient, the electrical conductance, and the thermal conductivity of sinusoidally corrugated silicon nanowires and eventually look into an enhancement of the thermoelectric figure-of-merit [Formula: see text] from the modulated nanowires over typical straight nanowires. A loss in the electronic transport coefficient is calculated with the recursive Green function along with the Landauer formalism, and the thermal transport is simulated with the molecular dynamics. In contrast to a small influence on the thermopower and the electrical conductance of the geometry-modulated nanowires, a large reduction of the thermal conductivity yields an enhancement of the efficiency by 10% to 35% from the typical nanowires. We find that this approach can be easily extended to various structures and materials as we consider the geometrical modulation as a sole source of perturbation to the system.

  12. Development of High Power Density Micro-Thermoelectric Generators

    NASA Astrophysics Data System (ADS)

    Zhang, Wenhua

    Thermoelectric generators (TEGs) are promising for the waste heat recovery in virtue of the ability to directly convert heat to electricity. Despite of their relatively low energy conversion efficiency, TEGs have many advantages including high reliability, long lifetime, and environmental friendliness. Especially, compared to conventional heat engines, TEGs are compact, scalable, and can be easily driven by small temperature differences. Potential applications of TEGs include thermal sensing, thermal management, and thermal energy harvesting to power wireless sensors and microelectronic devices such as wearable medical sensors and wristwatches. This dissertation presents my work on development of high power density non-flexible and flexible micro-TEGs for thermal energy harvesting in the ambient environment. Micro- TEGs are developed by a bottom-up approach combing electroplating and microfabrication processes. Pulsed electroplating is mainly adopted to deposit thermoelectric materials in the device fabrication. First, I collaborated with Dr. Zhou in our lab and systematically studied the effect of deposition parameters on composition, microstructure, and thermoelectric properties of the electroplated Bi2Te3 and Sb2 Te3 thin films. We demonstrated that thermoelectric properties of both Bi2Te3 and Sb2Te3 films can be enhanced by tuning the pulse off-to-on ratio. After the fundamental study on the deposition conditions, morphology, and thermoelectric properties of the electroplated materials, we fabricated a high power density cross-plane micro-TEG on the SiO2/Si substrate by integrating the pulsed electroplating with microfabrication processes. The TEG consists of a total of 127 pairs of n-type Bi2Te3 and ptype Sb2Te3 thermoelectric pillars embedded in a SU-8 matrix to enhance the overall mechanical strength of the device. Both bottom and top electrical connections are formed by electroplating, which is advantageous because of facile and low cost fabrication and low

  13. Correlation between defect transition levels and thermoelectric operational temperature of doped CrSi2

    NASA Astrophysics Data System (ADS)

    Singh, Abhishek; Pandey, Tribhuwan

    2014-03-01

    The performance of a thermoelectric material is quantified by figure of merit ZT. The challenge in achieving high ZT value requires simultaneously high thermopower, high electrical conductivity and low thermal conductivity at optimal carrier concentration. So far doping is the most versatile approach used for modifying thermoelectric properties. Previous studies have shown that doping can significantly improve the thermoelectric performance, however the tuning the operating temperature of a thermoelectric device is a main issue. Using first principles density functional theory, we report for CrSi2, a linear relationship between thermodynamic charge state transition levels of defects and temperature at which thermopower peaks. We show for doped CrSi2 that the peak of thermopower occurs at the temperature Tm, which corresponds to the position of defect transition level. Therefore, by modifying the defect transition level, a thermoelectric material with a given operational temperature can be designed. The authors thankfully acknowledge support from ADA under NpMASS.

  14. Electrodeposition of zinc antimony alloy thermoelectric materials

    NASA Astrophysics Data System (ADS)

    Hairin, A. L. N.; Romainor, M. N.; Othman, R.; Daud, F. D. M.

    2018-01-01

    Zinc antimonite, Zn4Sb3 is a promising thermoelectric material because of its high thermoelectric performance and abundance of Zn and Sb in nature. Thus, in this study, samples of Zn-Sb alloy were prepared using electrodeposition method because of its simple experimental set-up, which also carried out in the room temperature. From the XRD results, all samples deposited exhibit Zn-Sb alloy compositions. The best results were S1 and S3 as they had dominant peaks that showed the crystal lattice of Zn4Sb3. From the SEM images, the surface morphology of Zn-Sb alloy deposited samples showed were all-irregular, course and rough structures. While, the atoms arrangement of the deposited samples were all flowery-like. Based on physical properties characterization, the best samples; S1 (0.1M ZnCl2-0.1M SbCl3, 100mA, 120min) and S3 (0.1M ZnCl2-0.1M SbCl3, 50mA, 120min), were selected and investigated their thermoelectric performances; electrical conductivity and Seebeck coefficient, to determine their power factor, PF. Heat capacity of the samples was also examined to relate it with thermal conductivity of Zn-Sb deposited samples. For thermoelectric performance, S1 obtained power factor of 1.37x10-7V/K. Ω.cm at 102°C with the Seebeck coefficient of 181μV/K. While as for S3, the power factor was 1.58x10-7V/K. Ω.cm with Seebeck coefficient of 113μV/K at 101°C. From DSC analysis, it showed that S3 obtained higher Cp than S1. Cp for S3 was 46.8093mJ/°C while S1 was 38.3722mJ/°C.

  15. Tuning thermoelectricity in a Bi 2Se 3 topological insulator via varied film thickness

    DOE PAGES

    Guo, Minghua; Wang, Zhenyu; Xu, Yong; ...

    2016-01-12

    We report thermoelectric transport studies on Bi 2Se 3 topological insulator thin films with varied thickness grown by molecular beam epitaxy. We find that the Seebeck coefficient and thermoelectric power factor decrease systematically with the reduction of film thickness. These experimental observations can be explained quantitatively by theoretical calculations based on realistic electronic band structure of the Bi 2Se 3 thin films. Lastly, this work illustrates the crucial role played by the topological surface states on the thermoelectric transport of topological insulators, and sheds new light on further improvement of their thermoelectric performance.

  16. Thermoelectric applications as related to biomedical engineering for NASA Johnson Space Center

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Kramer, C.D.

    1997-07-01

    This paper presents current NASA biomedical developments and applications using thermoelectrics. Discussion will include future technology enhancements that would be most beneficial to the application of thermoelectric technology. A great deal of thermoelectric applications have focused on electronic cooling. As with all technological developments within NASA, if the application cannot be related to the average consumer, the technology will not be mass-produced and widely available to the public (a key to research and development expenditures and thermoelectric companies). Included are discussions of thermoelectric applications to cool astronauts during launch and reentry. The earth-based applications, or spin-offs, include such innovations asmore » tank and race car driver cooling, to cooling infants with high temperatures, as well as, the prevention of hair loss during chemotherapy. In order to preserve the scientific value of metabolic samples during long-term space missions, cooling is required to enable scientific studies. Results of one such study should provide a better understanding of osteoporosis and may lead to a possible cure for the disease. In the space environment, noise has to be kept to a minimum. In long-term space applications such as the International Space Station, thermoelectric technology provides the acoustic relief and the reliability for food, as well as, scientific refrigeration/freezers. Applications and future needs are discussed as NASA moves closer to a continued space presence in Mir, International Space Station, and Lunar-Mars Exploration.« less

  17. Hydrogenated Nano-/Micro-Crystalline Silicon Thin-Films for Thermoelectrics

    NASA Astrophysics Data System (ADS)

    Acosta, E.; Wight, N. M.; Smirnov, V.; Buckman, J.; Bennett, N. S.

    2018-06-01

    Thermoelectric technology has not yet been able to reach full-scale market penetration partly because most commercial materials employed are scarce/costly, environmentally unfriendly and in addition provide low conversion efficiency. The necessity to tackle some of these hurdles leads us to investigate the suitability of n-type hydrogenated microcrystalline silicon (μc-Si: H) in the fabrication of thermoelectric devices, produced by plasma enhanced chemical vapour deposition (PECVD), which is a mature process of proven scalability. This study reports an approach to optimise the thermoelectric power factor (PF) by varying the dopant concentration by means of post-annealing without impacting film morphology, at least for temperatures below 550°C. Results show an improvement in PF of more than 80%, which is driven by a noticeable increase of carrier mobility and Seebeck coefficient in spite of a reduction in carrier concentration. A PF of 2.08 × 10-4 W/mK2 at room temperature is reported for n-type films of 1 μm thickness, which is in line with the best values reported in recent literature for similar structures.

  18. Hydrogenated Nano-/Micro-Crystalline Silicon Thin-Films for Thermoelectrics

    NASA Astrophysics Data System (ADS)

    Acosta, E.; Wight, N. M.; Smirnov, V.; Buckman, J.; Bennett, N. S.

    2017-11-01

    Thermoelectric technology has not yet been able to reach full-scale market penetration partly because most commercial materials employed are scarce/costly, environmentally unfriendly and in addition provide low conversion efficiency. The necessity to tackle some of these hurdles leads us to investigate the suitability of n-type hydrogenated microcrystalline silicon (μc-Si: H) in the fabrication of thermoelectric devices, produced by plasma enhanced chemical vapour deposition (PECVD), which is a mature process of proven scalability. This study reports an approach to optimise the thermoelectric power factor (PF) by varying the dopant concentration by means of post-annealing without impacting film morphology, at least for temperatures below 550°C. Results show an improvement in PF of more than 80%, which is driven by a noticeable increase of carrier mobility and Seebeck coefficient in spite of a reduction in carrier concentration. A PF of 2.08 × 10-4 W/mK2 at room temperature is reported for n-type films of 1 μm thickness, which is in line with the best values reported in recent literature for similar structures.

  19. Cost Scaling of a Real-World Exhaust Waste Heat Recovery Thermoelectric Generator: A Deeper Dive

    NASA Technical Reports Server (NTRS)

    Hendricks, Terry J.; Yee, Shannon; LeBlanc, Saniya

    2015-01-01

    Cost is equally important to power density or efficiency for the adoption of waste heat recovery thermoelectric generators (TEG) in many transportation and industrial energy recovery applications. In many cases the system design that minimizes cost (e.g., the $/W value) can be very different than the design that maximizes the system's efficiency or power density, and it is important to understand the relationship between those designs to optimize TEG performance-cost compromises. Expanding on recent cost analysis work and using more detailed system modeling, an enhanced cost scaling analysis of a waste heat recovery thermoelectric generator with more detailed, coupled treatment of the heat exchangers has been performed. In this analysis, the effect of the heat lost to the environment and updated relationships between the hot-side and cold-side conductances that maximize power output are considered. This coupled thermal and thermoelectric treatment of the exhaust waste heat recovery thermoelectric generator yields modified cost scaling and design optimization equations, which are now strongly dependent on the heat leakage fraction, exhaust mass flow rate, and heat exchanger effectiveness. This work shows that heat exchanger costs most often dominate the overall TE system costs, that it is extremely difficult to escape this regime, and in order to achieve TE system costs of $1/W it is necessary to achieve heat exchanger costs of $1/(W/K). Minimum TE system costs per watt generally coincide with maximum power points, but Preferred TE Design Regimes are identified where there is little cost penalty for moving into regions of higher efficiency and slightly lower power outputs. These regimes are closely tied to previously-identified low cost design regimes. This work shows that the optimum fill factor Fopt minimizing system costs decreases as heat losses increase, and increases as exhaust mass flow rate and heat exchanger effectiveness increase. These findings have

  20. Thermoelectric materials with filled skutterudite structure for thermoelectric devices

    NASA Technical Reports Server (NTRS)

    Fleurial, Jean-Pierre (Inventor); Borshchevsky, Alex (Inventor); Caillat, Thierry (Inventor); Morelli, Donald T. (Inventor); Meisner, Gregory P. (Inventor)

    2002-01-01

    A class of thermoelectric compounds based on the skutterudite structure with heavy filling atoms in the empty octants and substituting transition metals and main-group atoms. High Seebeck coefficients and low thermal conductivities are achieved in combination with large electrical conductivities in these filled skutterudites for large ZT values. Substituting and filling methods are disclosed to synthesize skutterudite compositions with desired thermoelectric properties. A melting and/or sintering process in combination with powder metallurgy techniques is used to fabricate these new materials.

  1. Electronic cooling using thermoelectric devices

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    Zebarjadi, M., E-mail: m.zebarjadi@rutgers.edu; Institute of Advanced Materials, Devices, and Nanotechnology, Rutgers University, Piscataway, New Jersey 08854

    2015-05-18

    Thermoelectric coolers or Peltier coolers are used to pump heat in the opposite direction of the natural heat flux. These coolers have also been proposed for electronic cooling, wherein the aim is to pump heat in the natural heat flux direction and from hot spots to the colder ambient temperature. In this manuscript, we show that for such applications, one needs to use thermoelectric materials with large thermal conductivity and large power factor, instead of the traditionally used high ZT thermoelectric materials. We further show that with the known thermoelectric materials, the active cooling cannot compete with passive cooling, andmore » one needs to explore a new set of materials to provide a cooling solution better than a regular copper heat sink. We propose a set of materials and directions for exploring possible materials candidates suitable for electronic cooling. Finally, to achieve maximum cooling, we propose to use thermoelectric elements as fins attached to copper blocks.« less

  2. The long-term performance degradation of a radioisotope thermoelectric generator using silicon germanium

    NASA Technical Reports Server (NTRS)

    Stapfer, G.; Truscello, V. C.

    1976-01-01

    The successful utilization of a radioisotope thermoelectric generator (RTG) as the power source for spaceflight missions requires that the performance of such an RTG be predictable throughout the mission. Several mechanisms occur within the generator which tend to degrade the performance as a function of operating time. The impact which these mechanisms have on the available output power of an RTG depends primarily on such factors as time, temperature and self-limiting effects. The relative magnitudes, rates and temperature dependency of these various degradation mechanisms have been investigated separately by coupon experiments as well as 4-couple and 18-couple module experiments. This paper discusses the different individual mechanisms and summarizes their combined influence on the performance of an RTG. Also presented as part of the RTG long-term performance characteristics is the sensitivity of the available RTG output power to variations of the individual degradation mechanisms thus identifying the areas of greatest concern for a successful long-term mission.

  3. Optimal Design of a Thermoelectric Cooling/Heating System for Car Seat Climate Control (CSCC)

    NASA Astrophysics Data System (ADS)

    Elarusi, Abdulmunaem; Attar, Alaa; Lee, Hosung

    2017-04-01

    In the present work, the optimum design of thermoelectric car seat climate control (CSCC) is studied analytically in an attempt to achieve high system efficiency. Optimal design of a thermoelectric device (element length, cross-section area and number of thermocouples) is carried out using our newly developed optimization method based on the ideal thermoelectric equations and dimensional analysis to improve the performance of the thermoelectric device in terms of the heating/cooling power and the coefficient of performance (COP). Then, a new innovative system design is introduced which also includes the optimum input current for the initial (transient) startup warming and cooling before the car heating ventilation and air conditioner (HVAC) is active in the cabin. The air-to-air heat exchanger's configuration was taken into account to investigate the optimal design of the CSCC.

  4. Thermoelectric plastics: from design to synthesis, processing and structure–property relationships

    PubMed Central

    Kroon, Renee; Mengistie, Desalegn Alemu; Kiefer, David; Hynynen, Jonna; Ryan, Jason D.; Yu, Liyang

    2016-01-01

    Thermoelectric plastics are a class of polymer-based materials that combine the ability to directly convert heat to electricity, and vice versa, with ease of processing. Potential applications include waste heat recovery, spot cooling and miniature power sources for autonomous electronics. Recent progress has led to surging interest in organic thermoelectrics. This tutorial review discusses the current trends in the field with regard to the four main building blocks of thermoelectric plastics: (1) organic semiconductors and in particular conjugated polymers, (2) dopants and counterions, (3) insulating polymers, and (4) conductive fillers. The design and synthesis of conjugated polymers that promise to show good thermoelectric properties are explored, followed by an overview of relevant structure–property relationships. Doping of conjugated polymers is discussed and its interplay with processing as well as structure formation is elucidated. The use of insulating polymers as binders or matrices is proposed, which permit the adjustment of the rheological and mechanical properties of a thermoelectric plastic. Then, nanocomposites of conductive fillers such as carbon nanotubes, graphene and inorganic nanowires in a polymer matrix are introduced. A case study examines poly(3,4-ethylenedioxythiophene) (PEDOT) based materials, which up to now have shown the most promising thermoelectric performance. Finally, a discussion of the advantages provided by bulk architectures e.g. for wearable applications highlights the unique advantages that thermoelectric plastics promise to offer. PMID:27385496

  5. High Thermoelectric Performance of In4Se3-Based Materials and the Influencing Factors.

    PubMed

    Yin, Xin; Liu, Jing-Yuan; Chen, Ling; Wu, Li-Ming

    2018-02-20

    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, In 4 Se 3 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 In 4 Se 3-δ (δ = 0.65) shows strong anisotropy in its thermoelectric properties with a very high ZT of 1.48 at 705 K in the b-c plane (one of the highest values for an n-type thermoelectric material to date) but a much lower ZT of approximately 0.5 in the a-b plane. Because of the random dispersion of grains and the grain boundary effect, the electrical transport properties of polycrystalline In 4 Se 3 are poor, which is the main impediment to improve their performance. The In4-site in the In 4 Se 3 unit cell is substitutional for dopants such as Pb, which increases the carrier concentration by 2 orders of magnitude and the electrical conductivity to 143 S/cm. Furthermore, the electrical conductivity markedly increases to approximately 160 S/cm when Cu is doped into the interstitial site but remains as low as 30 S/cm with In1/In2/In3-site dopants, e.g., Ni, Zn, Ga, and Sn. In particular, the In4-site dopant ytterbium introduces a pinning level that highly localizes the charge carriers; thus, the electrical conductivity is maintained within an order of magnitude of 30 S/cm. Meanwhile, ytterbium also creates resonance states around the Fermi level that increase the Seebeck coefficient to -350 μV/K, the highest value at the ZT peak. However, the maximum solubility of the dopant may be limited by the Se-vacancy concentration. In addition, a Se vacancy also destroys the regular lattice vibrations and weakens phonon transport. Finally, nanoinclusions can effectively scatter the middle wavelength phonons, resulting in a

  6. Thermoelectric properties optimization of Fe2VGa by tuning electronic density of states via titanium doping

    NASA Astrophysics Data System (ADS)

    Wei, Pai-Chun; Huang, Ta-Sung; Lin, Shu-Wei; Guo, Guang-Yu; Chen, Yang-Yuan

    2015-10-01

    We report the correlation between thermoelectric properties and electronic band structure of thermoelectric Heusler alloy Fe2V1-xTixGa by comparing experimental measurements with theoretical calculations. The electrical resistivity data show that the semiconducting-like behavior of pure Fe2VGa is transformed to a more metallic-like behavior at x = 0.1. Meanwhile, an enhancement of the Seebeck coefficient was observed for all Ti doped specimens at elevated temperatures with a peak value of 57 μV/K for x = 0.05 at 300 K. The experimental results can be elucidated by the calculated band structure, i.e., a gradual shifting of the Fermi level from the middle of the pseudogap to the region of valence bands. With optimized doping, the thermoelectric power factor can be significantly enhanced to 3.95 mW m-1 K-2 at room temperature, which is comparable to the power factors of Bi2Te3-based compounds. The synergy of thermal conductivity reduction due to the alloying effect and the significant increase of the thermoelectric power factor leads to higher order zT values than that of prime Fe2VGa.

  7. semiconducting nanostructures: morphology and thermoelectric properties

    NASA Astrophysics Data System (ADS)

    Culebras, Mario; Torán, Raquel; Gómez, Clara M.; Cantarero, Andrés

    2014-08-01

    Semiconducting metallic oxides, especially perosvkite materials, are great candidates for thermoelectric applications due to several advantages over traditionally metallic alloys such as low production costs and high chemical stability at high temperatures. Nanostructuration can be the key to develop highly efficient thermoelectric materials. In this work, La 1- x Ca x MnO 3 perosvkite nanostructures with Ca as a dopant have been synthesized by the hydrothermal method to be used in thermoelectric applications at room temperature. Several heat treatments have been made in all samples, leading to a change in their morphology and thermoelectric properties. The best thermoelectric efficiency has been obtained for a Ca content of x=0.5. The electrical conductivity and Seebeck coefficient are strongly related to the calcium content.

  8. Oxygen partial pressure dependence of thermoelectric power factor in polycrystalline n-type SrTiO3: Consequences for long term stability in thermoelectric oxides

    NASA Astrophysics Data System (ADS)

    Sharma, Peter A.; Brown-Shaklee, Harlan J.; Ihlefeld, Jon F.

    2017-04-01

    The Seebeck coefficient and electrical conductivity have been measured as functions of oxygen partial pressure over the range of 10-22 to 10-1 atm at 1173 K for a 10% niobium-doped SrTiO3 ceramic with a grain size comparable to the oxygen diffusion length. Temperature-dependent measurements performed from 320 to 1275 K for as-prepared samples reveal metallic-like conduction and good thermoelectric properties. However, upon exposure to progressively increasing oxygen partial pressure, the thermoelectric power factor decreased over time scales of 24 h, culminating in a three order of magnitude reduction over the entire operating range. Identical measurements on single crystal samples show negligible changes in the power factor so that the instability of ceramic samples is primarily tied to the kinetics of grain boundary diffusion. This work provides a framework for understanding the stability of thermoelectric properties in oxides under different atmospheric conditions. The control of the oxygen atmosphere remains a significant challenge in oxide thermoelectrics.

  9. The performance of a combined solar photovoltaic (PV) and thermoelectric generator (TEG) system

    NASA Astrophysics Data System (ADS)

    Bjørk, R.; Nielsen, K. K.

    2015-10-01

    The performance of a combined solar photovoltaic (PV) and thermoelectric generator (TEG) system is examined using an analytical model for four different types of commercial PVs and a commercial bismuth telluride TEG. The TEG is applied directly on the back of the PV, so that the two devices have the same temperature. The PVs considered are crystalline Si (c-Si), amorphous Si (a-Si), copper indium gallium (di)selenide (CIGS) and cadmium telluride (CdTe) cells. The degradation of PV performance with temperature is shown to dominate the increase in power produced by the TEG, due to the low efficiency of the TEG. For c-Si, CIGS and CdTe PV cells the combined system produces a lower power and has a lower efficiency than the PV alone, whereas for an a-Si cell the total system performance may be slightly increased by the TEG.

  10. Development of advanced thermoelectric materials

    NASA Technical Reports Server (NTRS)

    1984-01-01

    The development of an advanced thermoelectric material for radioisotope thermoelectric generator (RTG) applications is reported. A number of materials were explored. The bulk of the effort, however, was devoted to improving silicon germanium alloys by the addition of gallium phosphide, the synthesis and evaluation of lanthanum chrome sulfide and the formulation of various mixtures of lanthanum sulfide and chrome sulfide. It is found that each of these materials exhibits promise as a thermoelectric material.

  11. Silicon-Based Thermoelectrics: Harvesting Low Quality Heat Using Economically Printed Flexible Nanostructured Stacked Thermoelectric Junctions

    DOE Office of Scientific and Technical Information (OSTI.GOV)

    None

    2010-03-01

    Broad Funding Opportunity Announcement Project: UIUC is experimenting with silicon-based materials to develop flexible thermoelectric devices—which convert heat into energy—that can be mass-produced at low cost. A thermoelectric device, which resembles a computer chip, creates electricity when a different temperature is applied to each of its sides. Existing commercial thermoelectric devices contain the element tellurium, which limits production levels because tellurium has become increasingly rare. UIUC is replacing this material with microscopic silicon wires that are considerably cheaper and could be equally effective. Improvements in thermoelectric device production could return enough wasted heat to add up to 23% to ourmore » current annual electricity production.« less

  12. Laser-powered thermoelectric generators operating at cryogenic temperatures

    NASA Astrophysics Data System (ADS)

    Harutyunyan, S. R.; Vardanyan, V. H.; Kuzanyan, A. S.; Nikoghosyan, V. R.; Kunii, S.; Winzer, K.; Wood, K. S.; Gulian, A. M.

    2005-11-01

    A thermoelectric generator, operating in a cryostat at liquid helium temperatures, is described. Energy to the generator is supplied via an external laser beam. For this prototype device the associated heat load at permanent operation is comparable with the heat load associated with power delivery via metallic wires. Estimates indicate that still better performance can be enabled with existing thermoelectric materials, thereby far exceeding efficiency of traditional cryostat wiring. We used a prototype generator to produce electric power for measuring critical currents in Nb3Sn-films at 4K.

  13. Thermoelectric Properties of Selenides Spinels

    NASA Technical Reports Server (NTRS)

    Snyder, G.; Caillat, T.; Fleurial, J-P.

    2000-01-01

    Many compounds with the spinel structure type have been analyzed for their thermoelectric properties. Published data was used to augment experimental results presented here to select promising thermoelectric spinels.

  14. Thermoelectric properties of SnSe2 monolayer.

    PubMed

    Li, Guanpeng; Ding, Guangqian; Gao, Guoying

    2017-01-11

    The 2H (MoS 2 -type) phase of 2D transition metal dichalcogenides (TMDCs) has been extensively studied and exhibits excellent electronic and optoelectronic properties, but the high phonon thermal conductivity is detrimental to the thermoelectric performances. Here, we use first-principles methods combined with Boltzmann transport theory to calculate the electronic and phononic transport properties of 1T (CdI 2 -type) SnSe 2 monolayer, a recently realized 2D metal dichalcogenide semiconductor. The calculated band gap is 0.85 eV, which is a little larger than the bulk value. Lower phonon thermal conductivity and higher power factor are obtained in 1T-SnSe 2 monolayer compared to 2H-TMDCs monolayers. The low phonon thermal conductivity (3.27 W mK -1 at room temperature) is mainly due to the low phonon frequency of acoustic modes and the coupling of acoustic modes with optical modes. We also find that the p-type has better thermoelectric performance than the n-type, and the figure of merit within p-type can reach 0.94 at 600 K for 1T-SnSe 2 monolayer, which is higher than those of most 2H-TMDCs monolayers, making 1T-SnSe 2 monolayer a promising candidate for thermoelectric applications.

  15. Thermoelectric properties of nanocrystalline Sb2Te3 thin films: experimental evaluation and first-principles calculation, addressing effect of crystal grain size.

    PubMed

    Morikawa, Satoshi; Inamoto, Takuya; Takashiri, Masayuki

    2018-02-16

    The effect of crystal grain size on the thermoelectric properties of nanocrystalline antimony telluride (Sb 2 Te 3 ) thin films was investigated by experiments and first-principles studies using a developed relaxation time approximation. The Sb 2 Te 3 thin films were deposited on glass substrates using radio-frequency magnetron sputtering. To change the crystal grain size of the Sb 2 Te 3 thin films, thermal annealing was performed at different temperatures. The crystal grain size, lattice parameter, and crystal orientation of the thin films were estimated using XRD patterns. The carrier concentration and in-plane thermoelectric properties of the thin films were measured at room temperature. A theoretical analysis was performed using a first-principles study based on density functional theory. The electronic band structures of Sb 2 Te 3 were calculated using different lattice parameters, and the thermoelectric properties were predicted based on the semi-classical Boltzmann transport equation in the relaxation time approximation. In particular, we introduced the effect of carrier scattering at the grain boundaries into the relaxation time approximation by estimating the group velocities from the electronic band structures. Finally, the experimentally measured thermoelectric properties were compared with those obtained by calculation. As a result, the calculated thermoelectric properties were found to be in good agreement with the experimental results. Therefore, we can conclude that introducing the effect of carrier scattering at the grain boundaries into the relaxation time approximation contributes to enhance the accuracy of a first-principles calculation relating to nanocrystalline materials.

  16. Thermoelectric properties of nanocrystalline Sb2Te3 thin films: experimental evaluation and first-principles calculation, addressing effect of crystal grain size

    NASA Astrophysics Data System (ADS)

    Morikawa, Satoshi; Inamoto, Takuya; Takashiri, Masayuki

    2018-02-01

    The effect of crystal grain size on the thermoelectric properties of nanocrystalline antimony telluride (Sb2Te3) thin films was investigated by experiments and first-principles studies using a developed relaxation time approximation. The Sb2Te3 thin films were deposited on glass substrates using radio-frequency magnetron sputtering. To change the crystal grain size of the Sb2Te3 thin films, thermal annealing was performed at different temperatures. The crystal grain size, lattice parameter, and crystal orientation of the thin films were estimated using XRD patterns. The carrier concentration and in-plane thermoelectric properties of the thin films were measured at room temperature. A theoretical analysis was performed using a first-principles study based on density functional theory. The electronic band structures of Sb2Te3 were calculated using different lattice parameters, and the thermoelectric properties were predicted based on the semi-classical Boltzmann transport equation in the relaxation time approximation. In particular, we introduced the effect of carrier scattering at the grain boundaries into the relaxation time approximation by estimating the group velocities from the electronic band structures. Finally, the experimentally measured thermoelectric properties were compared with those obtained by calculation. As a result, the calculated thermoelectric properties were found to be in good agreement with the experimental results. Therefore, we can conclude that introducing the effect of carrier scattering at the grain boundaries into the relaxation time approximation contributes to enhance the accuracy of a first-principles calculation relating to nanocrystalline materials.

  17. Experimental Investigation of a Temperature-Controlled Car Seat Powered by an Exhaust Thermoelectric Generator

    NASA Astrophysics Data System (ADS)

    Du, H.; Wang, Y. P.; Yuan, X. H.; Deng, Y. D.; Su, C. Q.

    2016-03-01

    To improve the riding comfort and rational utilization of the electrical energy captured by an automotive thermoelectric generator (ATEG), a temperature-controlled car seat was constructed to adjust the temperature of the car seat surface. Powered by the ATEG and the battery, the seat-embedded air conditioner can improve the riding comfort using a thermoelectric device to adjust the surface temperature of the seat, with an air duct to regulate the cold side and hot side of the thermoelectric device. The performance of the thermoelectric cooler (TEC) and theoretical analysis on the optimum state of the TEC device are put forward. To verify the rationality of the air duct design and to ensure sufficient air supply, the velocity field of the air duct system was obtained by means of the finite element method. To validate the reliability of the numerical simulation, the air velocity around the thermoelectric device was measured by a wind speed transmitter. The performance of the temperature-controlled car seat has been validated and is in good agreement with bench tests and real vehicle tests.

  18. Thermoelectric Figure-of-Merit of Nanostructured Silicon with a Low Concentration of Germanium

    NASA Astrophysics Data System (ADS)

    Zhu, Gaohua; Lee, Hohyun; Lan, Yucheng; Wang, Xiaowei; Joshi, Giri; Wang, Dezhi; Yang, Jian; Dresselhaus, Mildred; Chen, Gang; Ren, Zhifeng

    2009-03-01

    The thermoelectric properties of nanostructured silicon (Si) with a low concentration of germanium (Ge) are investigated. A low concentration of Ge leads to a significant cost reduction of the final product since Ge is at least 100 times more expensive than Si. By using only 5 atomic % Ge (Si95Ge5), we have achieved a thermoelectric figure-of-merit (ZT) of 0.95, similar to the ZT in the large grained Si80Ge20 alloy that is three times more expensive, and is almost four times that of the large grained bulk Si. The enhancement in the thermoelectric ZT for the nanostructured Si95Ge5 is mostly due to the reduced thermal conductivity caused by phonon scattering at the increased grain boundaries and the Ge alloying effect.

  19. Enhancement of thermoelectric power factor of Sr2CoMoO6 double perovskite by annealing in reducing atmosphere

    NASA Astrophysics Data System (ADS)

    Tanwar, Khagesh; Saxena, Mandvi; Maiti, Tanmoy

    2017-10-01

    In general, n-type thermoelectric materials are rather difficult to design. This study particularly pivoted on designing potential environmentally benign oxides based n-type thermoelectric material. We synthesized Sr2CoMoO6 (SCMO) polycrystalline ceramics via the solid-state synthesis route. XRD, SEM, and thermoelectric measurements were carried out for phase constitution, microstructure analysis, and to determine its potential for thermoelectric applications. As-sintered SCMO sample showed an insulator like behavior till 640 °C after which it exhibited an n-type non-degenerate semiconductor behavior followed by a p-n type conduction switching. To stabilize a high temperature n-type behavior, annealing of SCMO in reducing atmosphere (H2) at 1000 °C was carried out. After annealing, the SCMO demonstrated an n-type semiconductor behavior throughout the temperature range of measurement. The electrical conductivity (σ) and the power factor (S2σ) were found to be increased manifold in the annealed SCMO double perovskite.

  20. (Indium, Aluminum) co-doped Zinc Oxide as a Novel Material System for Quantum-Well Multilayer Thermoelectrics

    NASA Astrophysics Data System (ADS)

    Teehan, Sean

    Waste heat recovery from low efficiency industrial processes requires high performance thermoelectric materials to meet challenging requirements. The efficiency such a device is quantified by the dimensionless figure of merit ZT=S2sigmaT/kappa, where S is the Seebeck coefficient, sigma is the electrical conductivity, T is the absolute temperature and kappa is the thermal conductivity. For practical applications these devices are only cost-effective if the ZT is higher than 2. Theoretically it has been proven that by engineering nanostructures with lower dimensionality one can significantly increase ZT. A superlattice, or a system of 2-dimensional multilayer quantum wells has previously shown the potential to be used for thermoelectric structures. However, the use of conventional materials within these structures has only allowed this at low temperatures and has utilized cross-plane transport. This study focuses on both high temperature range operation and the in-plane transport properties of such structures, which benefit from both quantum confinement and an enhancement in density of states near EF. The n-type structures are fabricated by alternately sputtering barrier and well materials of Al-doped ZnO (AZO) and indium co-doped AZO, respectively. Samples investigated consist of 50 periods with targeted layer thicknesses of 10nm, which results in sufficient sampling material as well as quantum well effects. The indium doping level within the quantum well was controlled by varying the target power, and ultimately results in a 3x improvement in power factor (S 2sigma) over the parent bulk materials. The film characterization was determined by X-ray reflectometry, transmission electron microscopy, X-ray diffraction, auger electron spectroscopy, as well as other relevant techniques. In addition, process optimization was performed on material parameters such as layer thickness, interface roughness, and band-gap offset which all play a major role in determining the