Science.gov

Sample records for enhanced thermoelectric performance

  1. Enhanced Thermoelectric Performance in Rough Silicon Nanowires

    NASA Astrophysics Data System (ADS)

    Chen, Renkun; Hochbaum, Allon I.; Diaz Delgado, Raul; Liang, Wenjie; Garnett, Erik C.; Najarian, Mark; Majumdar, Arun; Yang, Peidong

    2008-03-01

    Due to the disparity between electron (<10 nm) and phonon ( ˜100 nm) mean free paths in silicon, nanostructured Si could effectively block phonon transport by boundary scattering while maintaining electron transport, thereby enhancing thermoelectric figure of merit, ZT. Here we report the wafer-scale electrochemical synthesis and thermoelectric characterization of rough Si nanowires with enhanced ZT, relative to the bulk material. Single nanowire measurements show that their electrical resistivity and Seebeck coefficient are similar to those of bulk Si with similar dopant concentration. Thin nanowires, however, exhibit a 100-fold reduction in thermal conductivity (k), yielding a large ZT = 0.6 at room temperature. Although bulk Si is a poor thermoelectric material, Si nanowire arrays show promise as high-performance, scalable thermoelectric materials.

  2. 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.

  3. Enhanced thermoelectric performance of rough silicon nanowires.

    PubMed

    Hochbaum, Allon I; Chen, Renkun; Delgado, Raul Diaz; Liang, Wenjie; Garnett, Erik C; Najarian, Mark; Majumdar, Arun; Yang, Peidong

    2008-01-10

    Approximately 90 per cent of the world's power is generated by heat engines that use fossil fuel combustion as a heat source and typically operate at 30-40 per cent efficiency, such that roughly 15 terawatts of heat is lost to the environment. Thermoelectric modules could potentially convert part of this low-grade waste heat to electricity. Their efficiency depends on the thermoelectric figure of merit ZT of their material components, which is a function of the Seebeck coefficient, electrical resistivity, thermal conductivity and absolute temperature. Over the past five decades it has been challenging to increase ZT > 1, since the parameters of ZT are generally interdependent. While nanostructured thermoelectric materials can increase ZT > 1 (refs 2-4), the materials (Bi, Te, Pb, Sb, and Ag) and processes used are not often easy to scale to practically useful dimensions. Here we report the electrochemical synthesis of large-area, wafer-scale arrays of rough Si nanowires that are 20-300 nm in diameter. These nanowires have Seebeck coefficient and electrical resistivity values that are the same as doped bulk Si, but those with diameters of about 50 nm exhibit 100-fold reduction in thermal conductivity, yielding ZT = 0.6 at room temperature. For such nanowires, the lattice contribution to thermal conductivity approaches the amorphous limit for Si, which cannot be explained by current theories. Although bulk Si is a poor thermoelectric material, by greatly reducing thermal conductivity without much affecting the Seebeck coefficient and electrical resistivity, Si nanowire arrays show promise as high-performance, scalable thermoelectric materials.

  4. Engineering Nanostructural Routes for Enhancing Thermoelectric Performance: Bulk to Nanoscale.

    PubMed

    Mohanraman, Rajeshkumar; Lan, Tian-Wey; Hsiung, Te-Chih; Amada, Dedi; Lee, Ping-Chung; Ou, Min-Nan; Chen, Yang-Yuan

    2015-01-01

    Thermoelectricity is a very important phenomenon, especially its significance in heat-electricity conversion. If thermoelectric devices can be effectively applied to the recovery of the renewable energies, such as waste heat and solar energy, the energy shortage, and global warming issues may be greatly relieved. This review focusses recent developments on the thermoelectric performance of a low-dimensional material, bulk nanostructured materials, conventional bulk materials etc. Particular emphasis is given on, how the nanostructure in nanostructured composites, confinement effects in one-dimensional nanowires and doping effects in conventional bulk composites plays an important role in ZT enhancement. PMID:26913280

  5. Engineering Nanostructural Routes for Enhancing Thermoelectric Performance: Bulk to Nanoscale

    PubMed Central

    Mohanraman, Rajeshkumar; Lan, Tian-Wey; Hsiung, Te-Chih; Amada, Dedi; Lee, Ping-Chung; Ou, Min-Nan; Chen, Yang-Yuan

    2015-01-01

    Thermoelectricity is a very important phenomenon, especially its significance in heat-electricity conversion. If thermoelectric devices can be effectively applied to the recovery of the renewable energies, such as waste heat and solar energy, the energy shortage, and global warming issues may be greatly relieved. This review focusses recent developments on the thermoelectric performance of a low-dimensional material, bulk nanostructured materials, conventional bulk materials etc. Particular emphasis is given on, how the nanostructure in nanostructured composites, confinement effects in one-dimensional nanowires and doping effects in conventional bulk composites plays an important role in ZT enhancement. PMID:26913280

  6. Engineering Nanostructural Routes for Enhancing Thermoelectric Performance: Bulk to Nanoscale.

    PubMed

    Mohanraman, Rajeshkumar; Lan, Tian-Wey; Hsiung, Te-Chih; Amada, Dedi; Lee, Ping-Chung; Ou, Min-Nan; Chen, Yang-Yuan

    2015-01-01

    Thermoelectricity is a very important phenomenon, especially its significance in heat-electricity conversion. If thermoelectric devices can be effectively applied to the recovery of the renewable energies, such as waste heat and solar energy, the energy shortage, and global warming issues may be greatly relieved. This review focusses recent developments on the thermoelectric performance of a low-dimensional material, bulk nanostructured materials, conventional bulk materials etc. Particular emphasis is given on, how the nanostructure in nanostructured composites, confinement effects in one-dimensional nanowires and doping effects in conventional bulk composites plays an important role in ZT enhancement.

  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 of CdO : Ag nanocomposites.

    PubMed

    Gao, Linjie; Wang, Shufang; Liu, Ran; Zha, Xinyu; Sun, Niefeng; Wang, Shujie; Wang, Jianglong; Fu, Guangsheng

    2016-07-26

    CdO : Ag nanocomposites with metallic Ag nanoparticles embedded in the polycrystalline CdO matrix were synthesized by the solid-state reaction method. The addition of Ag led to increased grain boundaries of CdO and created numerous CdO/Ag interfaces. By incorporating Ag into the CdO matrix, the power factor was increased which was probably due to the carrier energy filtering effect induced by the enhanced energy-dependent scattering of electrons. In addition, reduced thermal conductivity was also achieved by stronger phonon scattering from grain boundaries, CdO/Ag interfaces and Ag nanoparticles. These concomitant effects resulted in enhanced ZT values for all CdO : Ag nanocomposites, demonstrating that the strategy of introducing metallic Ag nanoparticles into the CdO host was very effective in optimizing the thermoelectric performance. PMID:27411573

  9. Phase Transition Enhanced Thermoelectric Performance in Copper Chalcogenides

    NASA Astrophysics Data System (ADS)

    Brown, David; Day, Tristan; Borup, Kasper; Christensen, Sebastian; Iversen, Bo; Snyder, G. Jeffrey

    2014-03-01

    Thermoelectric effects are characterized by the Seebeck coefficient or thermopower, which is related to the entropy associated with charge transport. For example, coupling spin entropy with the presence of charge carriers has enabled the enhancement of zT in cobalt oxides. We demonstrate that the coupling of a continuous phase transition to carrier transport in Cu2Se over a broad (360-410 K) temperature range results in a dramatic peak in thermopower, an increase in phonon and electron scattering, and a corresponding doubling of zT (to 0.7 at 406 K), and a similar but larger increase over a wider temperature range in the zT of Cu1.97Ag0.03Se (almost 1.0 at 400K). The use of structural entropy for enhanced thermopower could lead to new engineering approaches for thermoelectric materials with high zT and new green applications for thermoelectrics. Resnick Sustainibility Institute.

  10. Enhanced Thermoelectric Performance and Anomalous Seebeck Effects in Topological Insulators

    NASA Astrophysics Data System (ADS)

    Xu, Yong; Gan, Zhongxue; Zhang, Shou-Cheng

    2014-06-01

    Improving the thermoelectric figure of merit zT is one of the greatest challenges in material science. The recent discovery of topological insulators (TIs) offers new promise in this prospect. In this work, we demonstrate theoretically that zT is strongly size dependent in TIs, and the size parameter can be tuned to enhance zT to be significantly greater than 1. Furthermore, we show that the lifetime of the edge states in TIs is strongly energy dependent, leading to large and anomalous Seebeck effects with an opposite sign to the Hall effect. These striking properties make TIs a promising material for thermoelectric science and technology.

  11. 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.

  12. Inhomogeneous thermal conductivity enhances thermoelectric cooling

    NASA Astrophysics Data System (ADS)

    Lu, Tingyu; Zhou, Jun; Li, Nianbei; Yang, Ronggui; Li, Baowen

    2014-12-01

    We theoretically investigate the enhancement of thermoelectric cooling performance in thermoelectric refrigerators made of materials with inhomogeneous thermal conductivity, beyond the usual practice of enhancing thermoelectric figure of merit (ZT) of materials. The dissipation of the Joule heat in such thermoelectric refrigerators is asymmetric which can give rise to better thermoelectric cooling performance. Although the thermoelectric figure of merit and the coefficient-of-performance are slightly enhanced, both the maximum cooling power and the maximum cooling temperature difference can be enhanced significantly. This finding can be used to increase the heat absorption at the cold end. We further find that the asymmetric dissipation of Joule heat leads to thermal rectification.

  13. Enhanced thermoelectric performance of spark plasma sintered copper-deficient nanostructured copper selenide

    NASA Astrophysics Data System (ADS)

    Tyagi, Kriti; Gahtori, Bhasker; Bathula, Sivaiah; Jayasimhadri, M.; Singh, Niraj Kumar; Sharma, Sakshi; Haranath, D.; Srivastava, A. K.; Dhar, Ajay

    2015-06-01

    We report the thermoelectric properties of nanostructured Cu-deficient Cu2Se, which was synthesized by high energy ball milling followed by spark plasma sintering. Our method obtained a significant enhancement in the thermoelectric figure of merit (ZT), i.e., ~1.4 at 973 K, which was ~30% higher than its bulk counterpart. This enhancement in the thermoelectric performance was due mainly to a significant reduction in the lattice thermal conductivity, which was attributed to enhanced phonon scattering at various length scales by nanoscale defects as well as abundant nanograin boundaries. The nanoscale defects were characterized by transmission electron microscopy of the nanostructured Cu2-xSe samples, which formed the basis of the ZT enhancement.

  14. Enhanced Thermoelectric Performance of Nanostructured Bi2Te3 through Significant Phonon Scattering.

    PubMed

    Yang, Lei; Chen, Zhi-Gang; Hong, Min; Han, Guang; Zou, Jin

    2015-10-28

    N-type Bi2Te3 nanostructures were synthesized using a solvothermal method and in turn sintered using sparking plasma sintering. The sintered n-type Bi2Te3 pellets reserved nanosized grains and showed an ultralow lattice thermal conductivity (∼0.2 W m(-1) K(-1)), which benefits from high-density small-angle grain boundaries accommodated by dislocations. Such a high phonon scattering leads an enhanced ZT of 0.88 at 400 K. This study provides an efficient method to enhance thermoelectric performance of thermoelectric nanomaterials through nanostructure engineering, making the as-prepared n-type nanostructured Bi2Te3 as a promising candidate for room-temperature thermoelectric power generation and Peltier cooling. PMID:26451626

  15. Enhanced Thermoelectric Performance of Nanostructured Bi2Te3 through Significant Phonon Scattering.

    PubMed

    Yang, Lei; Chen, Zhi-Gang; Hong, Min; Han, Guang; Zou, Jin

    2015-10-28

    N-type Bi2Te3 nanostructures were synthesized using a solvothermal method and in turn sintered using sparking plasma sintering. The sintered n-type Bi2Te3 pellets reserved nanosized grains and showed an ultralow lattice thermal conductivity (∼0.2 W m(-1) K(-1)), which benefits from high-density small-angle grain boundaries accommodated by dislocations. Such a high phonon scattering leads an enhanced ZT of 0.88 at 400 K. This study provides an efficient method to enhance thermoelectric performance of thermoelectric nanomaterials through nanostructure engineering, making the as-prepared n-type nanostructured Bi2Te3 as a promising candidate for room-temperature thermoelectric power generation and Peltier cooling.

  16. 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

    2016-03-01

    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.

  17. 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

    2016-03-01

    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. PMID:26829207

  18. Enhanced thermoelectric performance of nanostructured topological insulator Bi{sub 2}Se{sub 3}

    SciTech Connect

    Sun, G. L.; Li, L. L.; Qin, X. Y. Li, D.; Zou, T. H.; Xin, H. X.; Ren, B. J.; Zhang, J.; Li, Y. Y.; Li, X. J.

    2015-02-02

    To enhance thermoelectric performance by utilizing topological properties of topological insulators has attracted increasing attention. Here, we show that as grain size decreases from microns to ∼80 nm in thickness, the electron mobility μ increases steeply from 12–15 cm{sup 2} V{sup −1} s{sup −1} to ∼600 cm{sup 2} V{sup −1} s{sup −1}, owing to the contribution of increased topologically protected conducting surfaces. Simultaneously, its lattice thermal conductivity is lowered by ∼30%–50% due to enhanced phonon scattering from the increased grain boundaries. As a result, thermoelectric figure of merit, ZT, of all the fine-grained samples is improved. Specifically, a maximum value of ZT = ∼0.63 is achieved for Bi{sub 2}Se{sub 3} at T = ∼570 K.

  19. Enhanced thermoelectric performance of nanostructured topological insulator Bi2Se3

    NASA Astrophysics Data System (ADS)

    Sun, G. L.; Li, L. L.; Qin, X. Y.; Li, D.; Zou, T. H.; Xin, H. X.; Ren, B. J.; Zhang, J.; Li, Y. Y.; Li, X. J.

    2015-02-01

    To enhance thermoelectric performance by utilizing topological properties of topological insulators has attracted increasing attention. Here, we show that as grain size decreases from microns to ˜80 nm in thickness, the electron mobility μ increases steeply from 12-15 cm2 V-1 s-1 to ˜600 cm2 V-1 s-1, owing to the contribution of increased topologically protected conducting surfaces. Simultaneously, its lattice thermal conductivity is lowered by ˜30%-50% due to enhanced phonon scattering from the increased grain boundaries. As a result, thermoelectric figure of merit, ZT, of all the fine-grained samples is improved. Specifically, a maximum value of ZT = ˜0.63 is achieved for Bi2Se3 at T = ˜570 K.

  20. Enhanced performance of dispenser printed MA n-type Bi₂Te₃ composite thermoelectric generators.

    PubMed

    Madan, Deepa; Wang, Zuoqian; Chen, Alic; Juang, Rei-Cheng; Keist, Jay; Wright, Paul K; Evans, Jim W

    2012-11-01

    This work presents performance advancements of dispenser printed composite thermoelectric materials and devices. Dispenser printed thick films allow for low-cost and scalable manufacturing of microscale energy harvesting devices. A maximum ZT value of 0.31 has been achieved for mechanically alloyed (MA) n-type Bi₂Te₃-epoxy composite films with 1 wt % Se cured at 350 °C. The enhancement of ZT is a result of increase in the electrical conductivity through the addition of Se, which ultimately lowers the sintering temperature (350 °C). A 62 single-leg thermoelectric generator (TEG) prototype with 5 mm ×700 μm × 120 μm printed element dimensions was fabricated on a custom designed polyimide substrate with thick metal contacts. The prototype device produced a power output of 25 μW at 0.23 mA current and 109 mV voltage for a temperature difference of 20 °C, which is sufficient for low power generation for autonomous microsystem applications.

  1. Enhanced performance of dispenser printed MA n-type Bi₂Te₃ composite thermoelectric generators.

    PubMed

    Madan, Deepa; Wang, Zuoqian; Chen, Alic; Juang, Rei-Cheng; Keist, Jay; Wright, Paul K; Evans, Jim W

    2012-11-01

    This work presents performance advancements of dispenser printed composite thermoelectric materials and devices. Dispenser printed thick films allow for low-cost and scalable manufacturing of microscale energy harvesting devices. A maximum ZT value of 0.31 has been achieved for mechanically alloyed (MA) n-type Bi₂Te₃-epoxy composite films with 1 wt % Se cured at 350 °C. The enhancement of ZT is a result of increase in the electrical conductivity through the addition of Se, which ultimately lowers the sintering temperature (350 °C). A 62 single-leg thermoelectric generator (TEG) prototype with 5 mm ×700 μm × 120 μm printed element dimensions was fabricated on a custom designed polyimide substrate with thick metal contacts. The prototype device produced a power output of 25 μW at 0.23 mA current and 109 mV voltage for a temperature difference of 20 °C, which is sufficient for low power generation for autonomous microsystem applications. PMID:23130550

  2. Enhancement of Thermoelectric Performance by Reducing Phonon Thermal Conductance in Multiple Core-shell Nanowires

    PubMed Central

    Zhou, Wu-Xing; Chen, Ke-Qiu

    2014-01-01

    The thermoelectric properties of multiple core-shell nanowires are investigated by using nonequilibrium Green's function method and molecular dynamics simulations. The results show that the thermoelectric performance of multiple core-shell NWs can be improved observably with the increase of shell number compared with the single component NWs due to the significant reduction of phonon thermal conductance. The ZT value of multiple core-shell NWs can reach three times greater than that of the single component GaSb NWs at room temperature. Moreover, the ZT values of both the core-shell NWs and single component NWs are increased with the increasing temperature, but the ZT value of core-shell NWs increases more slowly than that of single component NWs. These results show that the single component NWs is suitable as thermoelectric material at much high temperature, but the multiple core-shell NWs is more suitable as thermoelectric material at room temperature. PMID:25413874

  3. Enhanced thermoelectric performance of (Ba,In) double-filled skutterudites via randomly arranged micropores

    SciTech Connect

    Yu, Jian; Zhao, Wen-Yu E-mail: zhangqj@whut.edu.cn; Wei, Ping; Zhu, Wan-Ting; Zhou, Hong-Yu; Liu, Zhi-Yuan; Tang, Ding-Guo; Lei, Bing; Zhang, Qing-Jie E-mail: zhangqj@whut.edu.cn

    2014-04-07

    Porous (Ba,In) double-filled skutterudite materials with pore diameter about 1–4 μm were prepared by the decomposition of metastable ZnSb inclusions induced by the Zn sublimation. Transport measurements revealed that the Seebeck coefficient was increased due to the electron filtering effect induced by nanostructures in the surfaces of pores, the electrical conductivity was almost unchanged because of the percolation effect of conducted network composed of filled skutterudites, and the lattice thermal conductivity was dramatically suppressed due to the enhanced pore-edge boundary scattering of long-wavelength phonons. As a result, a maximum ZT of 1.36 was obtained, increased by 22.5% as compared to that of the bulk material with same chemical composition. This work demonstrates that by introducing porous structures is thought to be an efficient approach to improve the thermoelectric performance of bulk materials.

  4. Improved Thermoelectric Performance via Piezoelectric Interaction

    NASA Astrophysics Data System (ADS)

    Montgomery, David

    2015-03-01

    Presented are the initial findings of enhanced voltage output in a hybrid thermoelectric piezoelectric generator (TPEG). We constructed TPEG by integrating insulating layers of polyvinylidene fluoride (PVDF) piezoelectric films between flexible thin film p-type and n-type thermoelectrics. The piezoelectric bound surface charge modifies the thermoelectric properties of the semiconductor electrodes which facilitates an increase in voltage. The TPEG voltage output has three contributions: traditional thermoelectric and piezoelectric terms, and a unique coupling term. A combined thermoelectric and piezoelectric model can be used to quantify the expected coupling voltage as a function of stress and thermal gradient. The fabrication, placement, and configuration of this interface allows for different device designs and affects overall performance. Under easily achievable stress and thermal gradient this new coupling effect can increase voltage output by 20%. Because of this piezoelectric modified thermoelectric effect these hybrid generators can out preform equivalent thermoelectric or piezoelectric generators.

  5. Ultrahigh power factor and enhanced thermoelectric performance of individual Te/TiS2 nanocables

    NASA Astrophysics Data System (ADS)

    Li, Rui; Dui, Jingna; Fu, Yunlong; Xu, Yanling; Zhou, Shaomin

    2016-10-01

    Here, we present the successful fabrication of Te/TiS2 heterostructure nanocables with enhanced thermoelectric (TE) performance by a two-step route (a facile solvothermal approach for Te nanowires and then the Te nanowires are used as templates for the controllable growth of the Te/TiS2 nanocables), which is scalable for practical nanodevice applications. The heterostructure nanocables of different sizes can be prepared by varying the synthetic composition. Measurements of the Seebeck coefficient (S), electrical conductivity (σ), and thermal conductivity (κ) are carried out on the same nanowires over a temperature range of 2-350 K. The heterostructure nanocables show an ultrahigh power factor (S2 σ) with a maximum value of 0.58 Wm-1 K-2, which comes from a high electrical conductivity and a strongly enhanced Seebeck coefficient. The figure of merit (ZT) can reach 1.91 at room temperature from a single nanocable with a diameter of 60 nm, which is thought to contribute to the formation of the hetero-phase core/shell structure. These results are expected to open up new application possibilities in nanoscale TE devices based on individual Te/TiS2 heterostructure nanocables.

  6. Ultrahigh power factor and enhanced thermoelectric performance of individual Te/TiS2 nanocables.

    PubMed

    Li, Rui; Dui, Jingna; Fu, Yunlong; Xu, Yanling; Zhou, Shaomin

    2016-10-14

    Here, we present the successful fabrication of Te/TiS2 heterostructure nanocables with enhanced thermoelectric (TE) performance by a two-step route (a facile solvothermal approach for Te nanowires and then the Te nanowires are used as templates for the controllable growth of the Te/TiS2 nanocables), which is scalable for practical nanodevice applications. The heterostructure nanocables of different sizes can be prepared by varying the synthetic composition. Measurements of the Seebeck coefficient (S), electrical conductivity (σ), and thermal conductivity (κ) are carried out on the same nanowires over a temperature range of 2-350 K. The heterostructure nanocables show an ultrahigh power factor (S(2) σ) with a maximum value of 0.58 Wm(-1) K(-2), which comes from a high electrical conductivity and a strongly enhanced Seebeck coefficient. The figure of merit (ZT) can reach 1.91 at room temperature from a single nanocable with a diameter of 60 nm, which is thought to contribute to the formation of the hetero-phase core/shell structure. These results are expected to open up new application possibilities in nanoscale TE devices based on individual Te/TiS2 heterostructure nanocables. PMID:27595302

  7. Ultrahigh power factor and enhanced thermoelectric performance of individual Te/TiS2 nanocables.

    PubMed

    Li, Rui; Dui, Jingna; Fu, Yunlong; Xu, Yanling; Zhou, Shaomin

    2016-10-14

    Here, we present the successful fabrication of Te/TiS2 heterostructure nanocables with enhanced thermoelectric (TE) performance by a two-step route (a facile solvothermal approach for Te nanowires and then the Te nanowires are used as templates for the controllable growth of the Te/TiS2 nanocables), which is scalable for practical nanodevice applications. The heterostructure nanocables of different sizes can be prepared by varying the synthetic composition. Measurements of the Seebeck coefficient (S), electrical conductivity (σ), and thermal conductivity (κ) are carried out on the same nanowires over a temperature range of 2-350 K. The heterostructure nanocables show an ultrahigh power factor (S(2) σ) with a maximum value of 0.58 Wm(-1) K(-2), which comes from a high electrical conductivity and a strongly enhanced Seebeck coefficient. The figure of merit (ZT) can reach 1.91 at room temperature from a single nanocable with a diameter of 60 nm, which is thought to contribute to the formation of the hetero-phase core/shell structure. These results are expected to open up new application possibilities in nanoscale TE devices based on individual Te/TiS2 heterostructure nanocables.

  8. Thermoelectric performance enhancement of calcium cobaltite through barium grain boundary segregation.

    PubMed

    Carvillo, Paulo; Chen, Yun; Boyle, Cullen; Barnes, Paul N; Song, Xueyan

    2015-09-21

    We report the dramatic increase of the Seebeck coefficient S and thermoelectric performance of calcium cobaltite Ca3Co4O9+δ ceramics through non-stoichiometric addition of minute amount of Ba. The nominal chemistry of polycrystal pellets are Ca3BaxCo4O9+δ (x = 0, 0.01, 0.05, and 0.1). At 323 K, S of Ca3Co4O9+δ is 135 μV K(-1), whereas S of Ba incorporated Ca3Ba0.05Co4O9+δ is 162.5 μV·K(-1), which is the highest S value near room temperature regime reported for calcium cobaltite. The increase of S for Ca3Ba0.05Co4O9+δ sample is accompanied by the decrease of the electrical resistivity ρ, resulting in high power factor S(2)/ρ of 843 μW·m(-1) K(-2) at 1007 K. Moreover, the thermal conductivities κ of Ca3BaxCo4O9+δ decrease with the increase of the Ba addition. The figure-of-merit ZT for Ca3Ba0.05Co4O9+δ reaches 0.52 at 1073 K and a factor of 2.5 increment in comparison with undoped Ca3Co4O9+δ. Nanostructure examinations show that the added Ba segregated at the Ca3Co4O9+δ grain boundaries, while the Ca3Co4O9+δ grain interior is free of Ba. Performance enhancement is attributed to the carrier filtering effect caused by the Ba segregation. In addition, Ba segregation promotes the better crystal alignment and the development of crystal texture. PMID:26357956

  9. Enhanced thermoelectric performance of n-type transformable AgBiSe2 polymorphs by indium doping

    NASA Astrophysics Data System (ADS)

    Liu, Xiaocun; Jin, Dou; Liang, Xin

    2016-09-01

    We demonstrate the improved thermoelectric properties of n-type lead-free transformable AgBiSe2 polymorphs by indium doping on silver sites. X-ray diffraction analysis suggests that complete solid solutions are well formed up to [In] = 0.02. Electrical conductivity and Seebeck coefficient behave in a routinely opposite manner due to the dominant role of the carrier concentration adjusted by the localized indium impurity levels, as also suggested by our density functional theory (DFT) calculations. As indium concentration increases, we observe a drastic variation of the thermoelectric transport properties with temperature, in the range of 450 to 580 K. By performing the isothermal electrical measurements, we attribute this interesting behavior to the ongoing α to β phase transformation process. The In 5s lone pair electrons, as indicated from our DFT calculations, increase the anharmonicity of the chemical bonds and enhance the phonon-phonon scattering. This, together with the introduced InAg .. point defects, further brings down the lattice thermal conductivity. The maximum thermoelectric figure of merit Z T is achieved at 773 K and increases from 0.3 for pristine AgBiSe2 to 0.7 for an optimal [In] = 0.015 doping, a more than two times enhancement.

  10. Solvothermal synthesis of wire-like SnxSb2Te3+x with an enhanced thermoelectric performance.

    PubMed

    Yang, Heng Quan; Miao, Lei; Liu, Cheng Yan; Wang, Xiao Yang; Peng, Ying; Zhang, Ai Juan; Zhou, Xiao Yuan; Wang, Guo Yu; Li, Chao; Huang, Rong

    2016-04-25

    Nanostructured tellurides have attracted increasing attention in thermoelectric applications for waste heat recovery and cooling devices. Here, we report on the synthesis of wire-like SnxSb2Te3+x (x = 0, 0.02 and 0.05) nanoparticles using elemental precursors in EG. The enhanced thermoelectric performance was achieved in alloyed samples due to the increase of carrier population in heavy valence band valleys by incorporating Sn(2+) at the Sb(3+) sublattice, enabling the simultaneous realization of low electrical resistivity along with a high Seebeck coefficient as well as the decline of thermal conductivity. Thus a boosted power factor and low thermal conductivity lead to the highest ZT value of 0.58 at 150 °C in the Sn0.02Sb2Te3.02 sample. Our research offers a general wet-chemical route for the preparation of one-dimensional nanomaterials and probably promotes the practical thermoelectric applications of Sb2Te3-based materials at low temperatures.

  11. Synthesis, characterization and enhanced thermoelectric performance of structurally ordered cable-like novel polyaniline-bismuth telluride nanocomposite

    NASA Astrophysics Data System (ADS)

    Chatterjee, Krishanu; Mitra, Mousumi; Kargupta, Kajari; Ganguly, Saibal; Banerjee, Dipali

    2013-05-01

    Bismuth telluride (Bi2Te3) nanorods and polyaniline (PANI) nanoparticles have been synthesized by employing solvothermal and chemical oxidative processes, respectively. Nanocomposites, comprising structurally ordered PANI preferentially grown along the surface of a Bi2Te3 nanorods template, are synthesized using in situ polymerization. X-ray powder diffraction, UV-vis and Raman spectral analysis confirm the highly ordered chain structure of PANI on Bi2Te3 nanorods, leading to a higher extent of doping, higher chain mobility and enhancement of the thermoelectric performance. Above 380 K, the PANI-Bi2Te3 nanocomposite with a core-shell/cable-like structure exhibits a higher thermoelectric power factor than either pure PANI or Bi2Te3. At room temperature the thermal conductivity of the composite is lower than that of its pure constituents, due to selective phonon scattering by the nanointerfaces designed in the PANI-Bi2Te3 nanocable structures. The figure of merit of the nanocomposite at room temperature is comparable to the values reported in the literature for bulk polymer-based composite thermoelectric materials.

  12. Solvothermal synthesis of wire-like SnxSb2Te3+x with an enhanced thermoelectric performance.

    PubMed

    Yang, Heng Quan; Miao, Lei; Liu, Cheng Yan; Wang, Xiao Yang; Peng, Ying; Zhang, Ai Juan; Zhou, Xiao Yuan; Wang, Guo Yu; Li, Chao; Huang, Rong

    2016-04-25

    Nanostructured tellurides have attracted increasing attention in thermoelectric applications for waste heat recovery and cooling devices. Here, we report on the synthesis of wire-like SnxSb2Te3+x (x = 0, 0.02 and 0.05) nanoparticles using elemental precursors in EG. The enhanced thermoelectric performance was achieved in alloyed samples due to the increase of carrier population in heavy valence band valleys by incorporating Sn(2+) at the Sb(3+) sublattice, enabling the simultaneous realization of low electrical resistivity along with a high Seebeck coefficient as well as the decline of thermal conductivity. Thus a boosted power factor and low thermal conductivity lead to the highest ZT value of 0.58 at 150 °C in the Sn0.02Sb2Te3.02 sample. Our research offers a general wet-chemical route for the preparation of one-dimensional nanomaterials and probably promotes the practical thermoelectric applications of Sb2Te3-based materials at low temperatures. PMID:27046535

  13. 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

  14. 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.

  15. Hot deformation induced defects and performance enhancement in FeSb{sub 2} thermoelectric materials

    SciTech Connect

    Wang, Yongzheng; Fu, Chenguang; Zhu, Tiejun E-mail: zhaoxb@zju.edu.cn; Hu, Lipeng; Jiang, Guangyu; Zhao, Xinbing E-mail: zhaoxb@zju.edu.cn; Zhao, Guanghui; Huo, Dexuan

    2013-11-14

    The effect of hot deformation induced defects and texture on thermoelectric properties of FeSb{sub 2} bulk crystals has been investigated. The transport properties of the samples along both parallel and perpendicular direction of pressing were measured from 3 K to 300 K. The results showed that thermal conductivity of the deformed samples was significantly reduced. After twice deformation, the thermal conductivity of the sample along the perpendicular direction of pressing was decreased to 4 W/mK, which was only one third of that before deformation. Transmission electron microscopy observation revealed the presence of high density of lattice defects in the deformed samples. The lattice thermal conductivity was analyzed using the Debye-Callaway approximation, and the results showed that the deformation induced lattice imperfections play an important role in enhancing phonon scattering. In addition, both the electrical resistivity and Seebeck coefficient exhibited a weak anisotropy in the deformed samples. The figure of merit ZT of the bulk FeSb{sub 2} was significantly improved from 0.010 to 0.021 after deformation.

  16. 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.

  17. Enhanced thermoelectric performance and novel nanopores in AgSbTe{sub 2} prepared by melt spinning

    SciTech Connect

    Du, Baoli; Li, Han; Xu, Jingjing; Tang, Xinfeng; Uher, Ctirad

    2011-01-15

    We report a melt-spinning spark-plasma-sintering synthesis process of the polycrystalline p-type material composed of AgSbTe{sub 2} coarse grains and evenly formed 5-10 nm pores that occur primarily on the surface of matrix grains. The formation mechanism of nanopores and their influences on the thermoelectric properties have been studied and correlated. Microstructure analysis shows that the as-prepared sample can be regarded as a nanocomposite of matrix and in situ generated nanopores evenly coated on matrix grains. For the single-phase component and the possible energy-filter effect caused by the nanopores, the electrical transport properties are improved. Moreover, the thermal conductivity is significantly reduced by strong phonon scattering effect resulted from the nanopores. The thermoelectric performance of the as prepared sample enhances greatly and a ZT of 1.65 at 570 K is achieved, increasing{approx}200% compared with the sample prepared by traditional melt and slow-cooling method. -- Graphical abstract: Representative nanostructure of AgSbTe{sub 2} sample (a) ribbons obtained after melt spinning (b) bulk AgSbTe{sub 2} material obtained after spark plasma sintering. Display Omitted

  18. Enhanced Thermoelectric Performance in Cu-Intercalated BiTeI by Compensation Weakening Induced Mobility Improvement

    PubMed Central

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

    2015-01-01

    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 a 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 BiTe0.98I1.02, the TE performance in Cu0.05BiTeI reveals a 150% and 20% enhancement at 300 and 520 K, respectively. 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. PMID:26394841

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

    DOE PAGES

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

    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 BiTe0.98I1.02, the TE performance in Cu0.05BiTeI 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. Enhanced thermoelectric performance in Cu-intercalated BiTeI by compensation weakening induced mobility improvement

    SciTech Connect

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

    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 a 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 BiTe0.98I1.02, the TE performance in Cu0.05BiTeI 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.

  1. 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

  2. High Performance Bulk Thermoelectric Materials

    SciTech Connect

    Ren, Zhifeng

    2013-03-31

    Over 13 plus years, we have carried out research on electron pairing symmetry of superconductors, growth and their field emission property studies on carbon nanotubes and semiconducting nanowires, high performance thermoelectric materials and other interesting materials. As a result of the research, we have published 104 papers, have educated six undergraduate students, twenty graduate students, nine postdocs, nine visitors, and one technician.

  3. Spinodally Decomposed PbSe-PbTe Nanoparticles for High-Performance Thermoelectrics: Enhanced Phonon Scattering and Unusual Transport Behavior.

    PubMed

    Kim, Min-Seok; Lee, Woo-Jin; Cho, Ki-Hyun; Ahn, Jae-Pyoung; Sung, Yun-Mo

    2016-07-26

    Dramatic enhancements in the figure of merit have been obtained in bulk thermoelectric materials by doping, band engineering, and nanostructuring. Especially, in p-type thermoelectrics, high figure of merits near 2.0 have been reported in a few papers through the reduction in lattice thermal conductivity and the advancement in power factors. However, there exists no report on the n-type systems showing high figure of merits because of their intrinsically low Seebeck coefficients. Here, we demonstrate that a nanostructured bulk n-type thermoelectric material that was assembled by sintering spinodally decomposed lead chalcogenide nanoparticles having a composition of PbSe0.5Te0.5 reaches a high figure of merit of 1.85. The spinodally decomposed nanoparticles permit our thermoelectric material to have extremely low lattice thermal conductivity and a high power factor as a result of nanostructuring, electronic optimization, insertion of an impurity phase and phase change in local areas. We propose that this interesting concept would be one of the promising approaches that overcome limitation arising from the fact that most parameters in the figure of merit are closely correlated. PMID:27397515

  4. Supramolecular Thermo-Electrochemical Cells: Enhanced Thermoelectric Performance by Host-Guest Complexation and Salt-Induced Crystallization.

    PubMed

    Zhou, Hongyao; Yamada, Teppei; Kimizuka, Nobuo

    2016-08-24

    Thermo-electrochemical cells have potential to generate thermoelectric voltage 1 order higher than that given by semiconductor materials. To overcome the current issues in thermoelectric energy conversion, it is of paramount importance to grow and fulfill the full potential of thermo-electrochemical cells. Here we report a rational supramolecular methodology that yielded the highest Seebeck coefficient of ca. 2.0 mV K(-1) around ambient temperatures. This is based on the encapsulation of triiodide ions in α-cyclodextrin, whose equilibrium is shifted to the complexation at lower temperatures, whereas it is inverted at elevated temperatures. This temperature-dependent host-guest interaction provides a concentration gradient of redox ion pairs between two electrodes, leading to the eminent performance of the thermo-electrochemical cells. The figure of merit for this system, zT reached a high value of 5 × 10(-3). The introduction of host-guest chemistry to thermoelectric cells thus provides a new perspective in thermoelectric energy conversion. PMID:27508406

  5. Supramolecular Thermo-Electrochemical Cells: Enhanced Thermoelectric Performance by Host-Guest Complexation and Salt-Induced Crystallization.

    PubMed

    Zhou, Hongyao; Yamada, Teppei; Kimizuka, Nobuo

    2016-08-24

    Thermo-electrochemical cells have potential to generate thermoelectric voltage 1 order higher than that given by semiconductor materials. To overcome the current issues in thermoelectric energy conversion, it is of paramount importance to grow and fulfill the full potential of thermo-electrochemical cells. Here we report a rational supramolecular methodology that yielded the highest Seebeck coefficient of ca. 2.0 mV K(-1) around ambient temperatures. This is based on the encapsulation of triiodide ions in α-cyclodextrin, whose equilibrium is shifted to the complexation at lower temperatures, whereas it is inverted at elevated temperatures. This temperature-dependent host-guest interaction provides a concentration gradient of redox ion pairs between two electrodes, leading to the eminent performance of the thermo-electrochemical cells. The figure of merit for this system, zT reached a high value of 5 × 10(-3). The introduction of host-guest chemistry to thermoelectric cells thus provides a new perspective in thermoelectric energy conversion.

  6. Metal nanoparticle decorated n-type Bi2Te3-based materials with enhanced thermoelectric performances

    NASA Astrophysics Data System (ADS)

    Wang, Shanyu; Li, Han; Lu, Ruiming; Zheng, Gang; Tang, Xinfeng

    2013-07-01

    In this study, n-type Cu and Zn metal nanoparticle decorated Bi2(Te0.9Se0.1)3 ingots were prepared by a large-scale zone melting technique, with the concept of ‘nanoparticle-in-alloy’ to separately tune the electrical and thermal transport properties. Cu and Zn additions play multiple but different roles in the materials, whereas both of them form metal nanoinclusions embedded in van der Waals gaps or grain boundaries, exerting influences on thermoelectric properties. Cu addition, accommodated in the tetrahedral vacancies formed by four Te(1) atoms, effectively adjusts the electron concentration by donating its valence electron, and appreciably optimizes the power factor. Coupled with the significant frustration of heat-carrying phonons by Cu nanoinclusions, a highest ZT of 1.15 can be achieved for the 1 at.% Cu sample, which is an ∼20% improvement compared with that of commercial halogen-doped ingots. Zn addition, however, acting as weak donor, noticeably increases the density of state effective mass and Seebeck coefficient, and gives rise to a high ZT of 1.1. In particular, the kilogram-grade production technique coupled with the high ZT makes metal nanoparticle decorated n-type materials very promising for commercial applications.

  7. Enhanced Thermoelectric Performance of Cu2CdSnSe4 by Mn Doping: Experimental and First Principles Studies

    PubMed Central

    Liu, F. S.; Zheng, J. X.; Huang, M. J.; He, L. P.; Ao, W. Q.; Pan, F.; Li, J. Q.

    2014-01-01

    Serials of Mn doping by substituting Cd sites on Cu2CdSnSe4 are prepared by the melting method and the spark plasma sintering (SPS) technique to form Cu2Cd1−xMnxSnSe4. Our experimental and theoretical studies show that the moderate Mn doping by substituting Cd sites is an effective method to improve the thermoelectric performance of Cu2CdSnSe4. The electrical resistivity is decreased by about a factor of 4 at 723 K after replacing Cd with Mn, but the seebeck coefficient decreases only slightly from 356 to 289 μV/K, resulting in the significant increase of the power factor. Although the thermal conductivity increases with the doping content of Mn, the figure of merit (ZT) is still increased from 0.06 (x = 0) to 0.16 (x = 0.10) at 723 K, by a factor of 2.6. To explore the mechanisms behind the experimental results, we have performed an ab initio study on the Mn doping effect and find that the Fermi level of Cu2CdSnSe4 is shifted downward to the valence band, thus improving the hole concentration and enhancing the electrical conductivity at the low level doping content. Optimizing the synthesis process and scaling Cu2Cd1−xMnxSnSe4 to nanoparticles may further improve the ZT value significantly by improving the electrical conductivity and enhancing the phonon scattering to decrease the thermal conductivity. PMID:25047225

  8. Enhanced thermoelectric performance in Cd doped CuInTe{sub 2} compounds

    SciTech Connect

    Cheng, N.; Liu, R.; Bai, S.; Shi, X. Chen, L.

    2014-04-28

    CuIn{sub 1−x}Cd{sub x}Te{sub 2} materials (x = 0, 0.02, 0.05, and 0.1) are prepared using melting-annealing method and the highly densified bulk samples are obtained through Spark Plasma Sintering. The X-ray diffraction data confirm that nearly pure chalcopyrite structures are obtained in all the samples. Due to the substitution of Cd at In sites, the carrier concentration is greatly increased, leading to much enhanced electrical conductivity and power factor. The single parabolic band model is used to describe the electrical transport properties of CuInTe{sub 2} and the low temperature Hall mobility is also modeled. By combing theoretical model and experiment data, the optimum carrier concentration in CuInTe{sub 2} is proposed to explain the greatly enhanced power factors in the Cd doped CuInTe{sub 2}. In addition, the thermal conductivity is reduced by extra phonon scattering due to the atomic mass and radius fluctuations between Cd and In atoms. The maximum zTs are observed in CuIn{sub 0.98}Cd{sub 0.02}Te{sub 2} and CuIn{sub 0.9}Cd{sub 0.1}Te{sub 2} samples, which are improved by over 100% at room temperature and around 20% at 600 K.

  9. Enhanced thermoelectric performance by the combination of alloying and doping in TiCoSb-based half-Heusler compounds

    NASA Astrophysics Data System (ADS)

    Qiu, Pengfei; Huang, Xiangyang; Chen, Xihong; Chen, Lidong

    2009-11-01

    TiCoSb-based half-Heusler compounds have been prepared and their thermoelectric properties are studied. By isoelectronic alloying on the Ti site with Zr, although both the thermal conductivity and electrical conductivity are suppressed, the Seebeck coefficient is improved remarkably with a highest value of -420 μV/K for Ti0.5Zr0.5CoSb at 600 K, which provides a larger space to optimize the thermoelectric performance. To further improve the performance of the TiCoSb-based isoelectronic alloy, doping Ni on the Co site was explored. It is found that small amount of Ni doping results in a great increase in the electrical conductivity, still with a relative large Seebeck coefficient. Ti0.6Hf0.4Co0.87Ni0.13Sb sample exhibits a peak power factor of 23.4μW/cmK2, which is the highest value for n-type TiCoSb-based half-Heusler compounds reported so far. As a result, a maximum dimensionless figure of merit of 0.70 has been achieved at 900 K for Ti0.6Hf0.4Co0.87Ni0.13Sb.

  10. Preferential Scattering by Interfacial Charged Defects for Enhanced Thermoelectric Performance in Few-layered n-type Bi2Te3

    PubMed Central

    Puneet, Pooja; Podila, Ramakrishna; Karakaya, Mehmet; Zhu, Song; He, Jian; Tritt, Terry M.; Dresselhaus, Mildred S.; Rao, Apparao M.

    2013-01-01

    Over the past two decades several nano-structuring methods have helped improve the figure of merit (ZT) in the state-of-the art bulk thermoelectric materials. While these methods could enhance the thermoelectric performance of p-type Bi2Te3, it was frustrating to researchers that they proved ineffective for n-type Bi2Te3 due to the inevitable deterioration of its thermoelectric properties in the basal plane. Here, we describe a novel chemical-exfoliation spark-plasma-sintering (CE-SPS) nano-structuring process, which transforms the microstructure of n-type Bi2Te3 in an extraordinary manner without compromising its basal plane properties. The CE-SPS processing leads to preferential scattering of electrons at charged grain boundaries, and thereby increases the electrical conductivity despite the presence of numerous grain boundaries, and mitigates the bipolar effect via band occupancy optimization leading to an upshift (by ~ 100 K) and stabilization of the ZT peak over a broad temperature range of ~ 150 K. PMID:24225424

  11. High performance thermoelectric nanocomposite device

    DOEpatents

    Yang, Jihui; Snyder, Dexter D.

    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.

  12. 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.

  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. PMID:27035740

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

    PubMed Central

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

    2015-01-01

    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. PMID:26666813

  15. Enhanced Thermoelectric Efficiency of Porous Silicene Nanoribbons

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    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.

  16. Enhanced Thermoelectric Efficiency of Porous Silicene Nanoribbons

    PubMed Central

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

    2015-01-01

    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. PMID:25820162

  17. 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.

  18. Mechanically-exfoliated stacks of thin films of Bi2Te3 topological insulators with enhanced thermoelectric performance

    NASA Astrophysics Data System (ADS)

    Goyal, V.; Teweldebrhan, D.; Balandin, A. A.

    2010-09-01

    The authors report on "graphene-like" mechanical exfoliation of single-crystal Bi2Te3 films and thermoelectric characterization of the stacks of such films. Thermal conductivity of the resulting "pseudosuperlattices" was measured by the "hot disk" and "laser flash" techniques. The room temperature in-plane (cross-plane) thermal conductivity of the stacks decreases by a factor of ˜2.4 (3.5) as compared to bulk. The thermal conductivity reduction with preserved electrical properties leads to strong increase in the thermoelectric figure of merit. It is suggested that the film thinning to few-quintuples and tuning of the Fermi level can help in achieving the topological-insulator surface transport regime with an extraordinary thermoelectric efficiency.

  19. Decoupling interrelated parameters for designing high performance thermoelectric materials.

    PubMed

    Xiao, Chong; Li, Zhou; Li, Kun; Huang, Pengcheng; Xie, Yi

    2014-04-15

    synergistically enhanced thermoelectric properties. This occurs through a significant reduction of thermal conductivity, without the deterioration of thermopower and electrical conductivity. In addition, we introduce the concept of spin entropy in wide band gap semiconductor nanocrystals, which acts to fully disentangle the otherwise interconnected quantities for synergistically optimized thermoelectric performance. Finally, we discuss a new concept we developed that is based on an ultrathin-nanosheet composite that we fabricated from ultrathin nanosheets of atomic thickness. These retain the original strong two-dimensional electron gas (2DEG) and allow for decoupled optimization of the three thermoelectric parameters, which improves thermoelectric performance.

  20. Enhanced thermoelectric performance driven by high-temperature phase transition in the phase change material Ge4SbTe5

    DOE PAGES

    Williams, Jared B.; Lara-Curzio, Edgar; Cakmak, Ercan; Watkins, Thomas R.; Morelli, Donald T.

    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(Sb2Te3)x tie-line. While many compounds on this tie-line have been recognized as thermoelectric materials, here we focus on Ge4SbTe5, a single phase compound just off of the (GeTe)1-x(Sb2Te3)x tie-line, that forms in a stable rocksalt crystal structure atmore » room temperature. We find that stoichiometric and undoped Ge4SbTe5 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

  1. 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.

  2. Performance testing of thermoelectric generators at JPL

    NASA Technical Reports Server (NTRS)

    Rouklove, P.; Truscello, V.

    1974-01-01

    Results of life tests of thermoelectric generators ranging in output power from 800 microwatts to 170 watts. Emphasis is placed on the results obtained from tests of three advanced prototypes - a high-performance generator, a transit-type generator, and a ring converter. In addition, the results of life tests of a number of generators representing Nimbus, Pioneer, and Viking technology are presented.

  3. 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.

  4. 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. PMID:27254307

  5. Engineering Band Structure via the Site Preference of Pb(2+) in the In(+) Site for Enhanced Thermoelectric Performance of In6Se7.

    PubMed

    Cui, Jiaolin; Cheng, Min; Wu, Wenchang; Du, Zhengliang; Chao, Yimin

    2016-09-01

    Although binary In-Se based alloys have in recent years gained interest as thermoelectric (TE) candidates, little attention has been paid to In6Se7-based compounds. Substituting Pb in In6Se7, preference for Pb(2+) in the In(+) site has been observed, allowing Fermi level (Fr) shift toward the conduction band, where the localized state conduction becomes dominant. Consequently, the Hall carrier concentration (nH) has been significantly enhanced with the highest nH value being about 2-3 orders of magnitude higher than that of the Pb-free sample. Meanwhile, the lattice thermal conductivity (κL) tends to be reduced as the nH value increases, owing to an increased phonon scattering on carriers. As a result, a significantly enhanced TE performance has been achieved with the highest TE figure of merit (ZT) of 0.4 at ∼850 K. This ZT value is 27 times that of intrinsic In6Se7 (ZT = 0.015 at 640 K), which proves a successful band structure engineering through site preference of Pb in In6Se7.

  6. Engineering Band Structure via the Site Preference of Pb(2+) in the In(+) Site for Enhanced Thermoelectric Performance of In6Se7.

    PubMed

    Cui, Jiaolin; Cheng, Min; Wu, Wenchang; Du, Zhengliang; Chao, Yimin

    2016-09-01

    Although binary In-Se based alloys have in recent years gained interest as thermoelectric (TE) candidates, little attention has been paid to In6Se7-based compounds. Substituting Pb in In6Se7, preference for Pb(2+) in the In(+) site has been observed, allowing Fermi level (Fr) shift toward the conduction band, where the localized state conduction becomes dominant. Consequently, the Hall carrier concentration (nH) has been significantly enhanced with the highest nH value being about 2-3 orders of magnitude higher than that of the Pb-free sample. Meanwhile, the lattice thermal conductivity (κL) tends to be reduced as the nH value increases, owing to an increased phonon scattering on carriers. As a result, a significantly enhanced TE performance has been achieved with the highest TE figure of merit (ZT) of 0.4 at ∼850 K. This ZT value is 27 times that of intrinsic In6Se7 (ZT = 0.015 at 640 K), which proves a successful band structure engineering through site preference of Pb in In6Se7. PMID:27541319

  7. Effect of heat transfer on the performance of thermoelectric generator-driven thermoelectric refrigerator system

    NASA Astrophysics Data System (ADS)

    Chen, Lingen; Meng, Fankai; Sun, Fengrui

    2012-01-01

    A model of thermoelectric generator-driven thermoelectric refrigerator with external heat transfer is proposed. The performance of the combined thermoelectric refrigerator device obeying Newton's heat transfer law is analyzed using the combination of finite time thermodynamics and non-equilibrium thermodynamics. Two analytical formulae for cooling load vs. working electrical current, and the coefficient of performance (COP) vs. working electrical current, are derived. For a fixed total heat transfer surface area of four heat exchangers, the allocations of the heat transfer surface area among the four heat exchangers are optimized for maximizing the cooling load and the coefficient of performance (COP) of the combined thermoelectric refrigerator device. For a fixed total number of thermoelectric elements, the ratio of number of thermoelectric elements of the generator to the total number of thermoelectric elements is also optimized for maximizing both the cooling load and the COP of the combined thermoelectric refrigerator device. The influences of thermoelectric element allocation and heat transfer area allocation are analyzed by detailed numerical examples. Optimum working electrical current for maximum cooling load and COP at different total number of thermoelectric elements and different total heat transfer area are obtained, respectively.

  8. Enhanced thermoelectric performance driven by high-temperature phase transition in the phase change material Ge4SbTe5

    SciTech Connect

    Williams, Jared B.; Lara-Curzio, Edgar; Cakmak, Ercan; Watkins, Thomas R.; Morelli, Donald T.

    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(Sb2Te3)x tie-line. While many compounds on this tie-line have been recognized as thermoelectric materials, here we focus on Ge4SbTe5, a single phase compound just off of the (GeTe)1-x(Sb2Te3)x tie-line, that forms in a stable rocksalt crystal structure at room temperature. We find that stoichiometric and undoped Ge4SbTe5 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.

  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. Effect of different surfactants and thicknesses on electrodeposited films of bismuth telluride and its thermoelectric performance

    NASA Astrophysics Data System (ADS)

    Kulsi, Chiranjit; Mitra, Mousumi; Kargupta, Kajari; Ganguly, Saibal; Banerjee, Dipali; Goswami, Shyamaprosad

    2015-10-01

    Thin films of bismuth telluride using various surfactants such as sodium dodecyl sulfate (SDS) and polyvinylpyrrolidone (PVP) have been electrochemically deposited. The influence of different surfactants on crystal orientation and morphology was investigated and correlated with the thermoelectric performance of the electrodeposited films. Since thickness affects the thermoelectric performance compared to the surfactant, thickness- dependent thermoelectric performance has also been investigated. The carrier mobilities of the films obtained are significantly enhanced due to improved surface morphology using different surfactants. Between the two surfactants, films with SDS exhibited the higher value of thermoelectric power, power factor, and figure of merit, which is due to the effect of micelle formation. The XRD pattern of all the films, which are electrodeposited without surfactant or using SDS and PVP, showed preferred crystal orientation along the (018) direction. The roles of organic molecules in the development of nanoparticles with improved thermoelectric properties have been investigated.

  11. Enhancing the thermoelectric performance and bridging the p- and n-type carrier asymmetry of Bi2Te3 thin films via topological surface states

    NASA Astrophysics Data System (ADS)

    Liu, Huijun; Zhang, Zhenyu

    2015-03-01

    It has been recognized that some of the best thermoelectric materials are also topological insulators (TIs), yet whether these two classes of materials are inherently connected remains mysterious and conceptually perplexing. Here we combine first-principles calculations and Boltzmann theory to study the thermoelectric properties of Bi2Te3 thin films in the few quintuple layer regime, and demonstrate how the ZT values of such strong three-dimensional TIs can be tuned by both the film thickness and relaxation time of the topological surface states relative to the bulk states. We first show that when the surface and bulk states have comparable relaxation times, such films could actually have higher ZT values in the non-TI regime than those in the TI regime. Nevertheless, the very existence and robustness of the topological surface states in the TI regime offers unique new design strategies to not only significantly enhance their ZT values, but also potentially bridge the long-standing challenge of p- and n-type carrier asymmetry faced by the broad thermoelectric research and industrial communities. We acknowledge financial support from the National Natural Science Foundation (Grant Nos. 51172167 and 1134006), and MOST of China (Grant Nos. 2013CB632502 and 2014CB921103).

  12. 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.

  13. 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. PMID:25782971

  14. 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.

  15. Tailored semiconducting carbon nanotube networks with enhanced thermoelectric properties

    NASA Astrophysics Data System (ADS)

    Avery, Azure D.; Zhou, Ben H.; Lee, Jounghee; Lee, Eui-Sup; Miller, Elisa M.; Ihly, Rachelle; Wesenberg, Devin; Mistry, Kevin S.; Guillot, Sarah L.; Zink, Barry L.; Kim, Yong-Hyun; Blackburn, Jeffrey L.; Ferguson, Andrew J.

    2016-04-01

    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, we 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. These findings provide the scientific underpinning for improved functional organic thermoelectric composites with carbon nanotube inclusions.

  16. Tailored semiconducting carbon nanotube networks with enhanced thermoelectric properties

    NASA Astrophysics Data System (ADS)

    Avery, Azure D.; Zhou, Ben H.; Lee, Jounghee; Lee, Eui-Sup; Miller, Elisa M.; Ihly, Rachelle; Wesenberg, Devin; Mistry, Kevin S.; Guillot, Sarah L.; Zink, Barry L.; Kim, Yong-Hyun; Blackburn, Jeffrey L.; Ferguson, Andrew J.

    2016-04-01

    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, we 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. These findings provide the scientific underpinning for improved functional organic thermoelectric composites with carbon nanotube inclusions.

  17. Tailored semiconducting carbon nanotube networks with enhanced thermoelectric properties

    DOE PAGES

    Avery, Azure D.; Zhou, Ben H.; Lee, Jounghee; Lee, Eui -Sup; Miller, Elisa M.; Ihly, Rachelle; Wesenberg, Devin; Mistry, Kevin S.; Guillot, Sarah L.; Zink, Barry L.; et al

    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, we demonstrate thatmore » 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

  18. Enhancing the thermoelectric figure of merit in engineered graphene nanoribbons

    PubMed Central

    Sangtarash, Sara; Lambert, Colin J

    2015-01-01

    Summary We demonstrate that thermoelectric properties of graphene nanoribbons can be dramatically improved by introducing nanopores. In monolayer graphene, this increases the electronic thermoelectric figure of merit ZT e from 0.01 to 0.5. The largest values of ZT e are found when a nanopore is introduced into bilayer graphene, such that the current flows from one layer to the other via the inner surface of the pore, for which values as high as ZT e = 2.45 are obtained. All thermoelectric properties can be further enhanced by tuning the Fermi energy of the leads. PMID:26171293

  19. 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

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

    PubMed

    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

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

    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.

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

    PubMed

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

    2016-03-07

    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.

  3. 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

  4. Nano-materials for enhanced thermoelectric efficiencies

    NASA Astrophysics Data System (ADS)

    Boukai, Akram

    2010-04-01

    Energy is the ultimate currency that drives the world economy. Without energy, the global economy would cease to function normally. Most of the world's energy comes from the burning of fossil fuels such as coal and oil. Unfortunately, these fossil fuels are limited and pollute the atmosphere. The rising costs and demand of energy products and the alarming rate of global warming have focused research efforts into alternative forms of renewable energy. Thermoelectrics are one class of renewable energy producing devices. Thermoelectrics operate by converting temperature differences into electrical power and vice versa. They find limited use due to their low efficiencies and high cost. This article will review the operation of thermoelectrics and their current state-of-the-art. It will also explore future promising research endeavors that aim to increase their efficiency.

  5. Tellurium as a high-performance elemental thermoelectric

    PubMed Central

    Lin, Siqi; Li, Wen; Chen, Zhiwei; Shen, Jiawen; Ge, Binghui; Pei, Yanzhong

    2016-01-01

    High-efficiency thermoelectric materials require a high conductivity. It is known that a large number of degenerate band valleys offers many conducting channels for improving the conductivity without detrimental effects on the other properties explicitly, and therefore, increases thermoelectric performance. In addition to the strategy of converging different bands, many semiconductors provide an inherent band nestification, equally enabling a large number of effective band valley degeneracy. Here we show as an example that a simple elemental semiconductor, tellurium, exhibits a high thermoelectric figure of merit of unity, not only demonstrating the concept but also filling up the high performance gap from 300 to 700 K for elemental thermoelectrics. The concept used here should be applicable in general for thermoelectrics with similar band features. PMID:26751919

  6. Enhancement of automotive exhaust heat recovery by thermoelectric devices

    SciTech Connect

    Ibrahim, Essam; Szybist, James P; Parks, II, James E

    2010-01-01

    In an effort to improve automobile fuel economy, an experimental study is undertaken to explore practical aspects of implementing thermoelectric devices for exhaust gas energy recovery. A highly instrumented apparatus consisting of a hot (exhaust gas) and a cold (coolant liquid) side rectangular ducts enclosing the thermoelectric elements has been built. Measurements of thermoelectric voltage output and flow and surface temperatures were acquired and analyzed to investigate the power generation and heat transfer properties of the apparatus. Effects of inserting aluminum wool packing material inside the hot side duct on augmentation of heat transfer from the gas stream to duct walls were studied. Data were collected for both the unpacked and packed cases to allow for detection of packing influence on flow and surface temperatures. Effects of gas and coolant inlet temperatures as well as gas flow rate on the thermoelectric power output were examined. The results indicate that thermoelectric power production is increased at higher gas inlet temperature or flow rate. However, thermoelectric power generation decreases with a higher coolant temperature as a consequence of the reduced hot-cold side temperature differential. For the hot-side duct, a large temperature gradient exists between the gas and solid surface temperature due to poor heat transfer through the gaseous medium. Adding the packing material inside the exhaust duct enhanced heat transfer and hence raised hot-side duct surface temperatures and thermoelectric power compared to the unpacked duct, particularly where the gas-to-surface temperature differential is highest. Therefore it is recommended that packing of exhaust duct becomes common practice in thermoelectric waste energy harvesting applications.

  7. Interference enhanced thermoelectricity in quinoid type structures.

    PubMed

    Strange, M; Seldenthuis, J S; Verzijl, C J O; Thijssen, J M; Solomon, G C

    2015-02-28

    Quantum interference (QI) effects in molecular junctions may be used to obtain large thermoelectric responses. We study the electrical conductance G and the thermoelectric response of a series of molecules featuring a quinoid core using density functional theory, as well as a semi-empirical interacting model Hamiltonian describing the π-system of the molecule which we treat in the GW approximation. Molecules with a quinoid type structure are shown to have two distinct destructive QI features close to the frontier orbital energies. These manifest themselves as two dips in the transmission, that remain separated, even when either electron donating or withdrawing side groups are added. We find that the position of the dips in the transmission and the frontier molecular levels can be chemically controlled by varying the electron donating or withdrawing character of the side groups as well as the conjugation length inside the molecule. This feature results in a very high thermoelectric power factor S(2)G and figure of merit ZT, where S is the Seebeck coefficient, making quinoid type molecules potential candidates for efficient thermoelectric devices. PMID:25725747

  8. Interference enhanced thermoelectricity in quinoid type structures

    SciTech Connect

    Strange, M. Solomon, G. C.; Seldenthuis, J. S.; Verzijl, C. J. O.; Thijssen, J. M.

    2015-02-28

    Quantum interference (QI) effects in molecular junctions may be used to obtain large thermoelectric responses. We study the electrical conductance G and the thermoelectric response of a series of molecules featuring a quinoid core using density functional theory, as well as a semi-empirical interacting model Hamiltonian describing the π-system of the molecule which we treat in the GW approximation. Molecules with a quinoid type structure are shown to have two distinct destructive QI features close to the frontier orbital energies. These manifest themselves as two dips in the transmission, that remain separated, even when either electron donating or withdrawing side groups are added. We find that the position of the dips in the transmission and the frontier molecular levels can be chemically controlled by varying the electron donating or withdrawing character of the side groups as well as the conjugation length inside the molecule. This feature results in a very high thermoelectric power factor S{sup 2}G and figure of merit ZT, where S is the Seebeck coefficient, making quinoid type molecules potential candidates for efficient thermoelectric devices.

  9. 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.

  10. 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.

  11. 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.

  12. Thermoelectric performance of classical topological insulator nanowires

    NASA Astrophysics Data System (ADS)

    Gooth, Johannes; Göran Gluschke, Jan; Zierold, Robert; Leijnse, Martin; Linke, Heiner; Nielsch, Kornelius

    2015-01-01

    There is currently substantial effort being invested into creating efficient thermoelectric (TE) nanowires based on topological insulator (TI) chalcogenide-type materials. A key premise of these efforts is the assumption that the generally good TE properties that these materials exhibit in bulk form will translate into similarly good or even better TE performance of the same materials in nanowire form. Here, we calculate TE performance of TI nanowires based on Bi2Te3, Sb2Te3 and Bi2Se3 as a function of diameter and Fermi level. We show that the TE performance of TI nanowires does not derive from the properties of the bulk material in a straightforward way. For all investigated systems the competition between surface states and bulk channel causes a significant modification of the TE transport coefficients if the diameter is reduced into the sub 10 μm range. Key aspects are that the surface and bulk states are optimized at different Fermi levels or have different polarity as well as the high surface to volume ratio of the nanowires. This limits the maximum TE performance of TI nanowires and thus their application in efficient TE devices.

  13. Power factor enhancement in solution-processed organic n-type thermoelectric materials through side chain design

    NASA Astrophysics Data System (ADS)

    Russ, Boris; Robb, Maxwell J.; Brunetti, Fulvio G.; Miller, Levi; Patel, Shrayesh; Ho, Victor; Urban, Jeffrey J.; Chabinyc, Michael L.; Hawker, Craig J.; Segalman, Rachel A.

    2014-03-01

    Building efficient organic thermoelectric architectures requires complementary p-type (hole transporting) and n-type (electron transporting) components. While several high performance hole-transporting polymers have been developed, the design of n-type organics has proven challenging, and thermoelectric studies of organic n-type systems are scarce. We investigate the properties of a series of charged perylene diimide (PDI) derivatives. Charged side chains in these materials enable both water solubility and self-doping. We show that changing the length of the alkyl spacer between the charged end groups and the PDI core dramatically improves thin film thermoelectric properties. The top derivatives in our study demonstrated the highest power factor reported for n-type solution-processed films. By complementing thermoelectric characterization of these variants with insight on the electronic and structural property changes from optical spectroscopy, EPR, and GIWAXS experiments, our findings shape a promising molecular design strategy for future enhancements in thermoelectric performance.

  14. Band structure engineering through orbital interaction for enhanced thermoelectric power factor

    SciTech Connect

    Zhu, Hong; Sun, Wenhao; Ceder, Gerbrand; Armiento, Rickard; Lazic, Predrag

    2014-02-24

    Band structure engineering for specific electronic or optical properties is essential for the further development of many important technologies including thermoelectrics, optoelectronics, and microelectronics. In this work, we report orbital interaction as a powerful tool to finetune the band structure and the transport properties of charge carriers in bulk crystalline semiconductors. The proposed mechanism of orbital interaction on band structure is demonstrated for IV-VI thermoelectric semiconductors. For IV-VI materials, we find that the convergence of multiple carrier pockets not only displays a strong correlation with the s-p and spin-orbit coupling but also coincides with the enhancement of power factor. Our results suggest a useful path to engineer the band structure and an enticing solid-solution design principle to enhance thermoelectric performance.

  15. Enhancing efficiency and power of quantum-dots resonant tunneling thermoelectrics in three-terminal geometry by cooperative effects

    SciTech Connect

    Jiang, Jian-Hua

    2014-11-21

    We propose a scheme of multilayer thermoelectric engine where one electric current is coupled to two temperature gradients in three-terminal geometry. This is realized by resonant tunneling through quantum dots embedded in two thermal and electrical resisting polymer matrix layers between highly conducting semiconductor layers. There are two thermoelectric effects, one of which is pertaining to inelastic transport processes (if energies of quantum dots in the two layers are different), while the other exists also for elastic transport processes. These two correspond to the transverse and longitudinal thermoelectric effects, respectively, and are associated with different temperature gradients. We show that cooperation between the two thermoelectric effects leads to markedly improved figure of merit and power factor, which is confirmed by numerical calculation using material parameters. Such enhancement is robust against phonon heat conduction and energy level broadening. Therefore, we demonstrated cooperative effect as an additional way to effectively improve performance of thermoelectrics in three-terminal geometry.

  16. 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.

  17. 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

    2015-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-06-01

    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.

  19. 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

  20. Theoretical Approach to Predict the Performance of Thermoelectric Generator Modules

    NASA Astrophysics Data System (ADS)

    Elarusi, Abdulmunaem H.; Fagehi, Hassan; Lee, Hosung; Attar, Alaa

    2016-10-01

    The aim of this work was to examine the validity of the thermoelectric modules' performance predicted by formulating the effective thermoelectric material properties. The three maximum parameters (output power, current, and efficiency) are defined in terms of the average temperature of the thermoelectric generator (TEG). These three maximum parameters, which are either taken from commercial TEG modules or measurements for particular operating conditions, are used to define the effective material properties (Seebeck coefficient, thermal conductivity, and electrical resistivity). The commercial performance curves provided by the manufacturer were compared with the results obtained here by the effective material properties with the simple standard thermoelectric equations. It has been found that this technique predicts the performance of four commercial thermoelectric modules with fair to good accuracy. The characteristics of the TEGs were represented using the normalized charts constructed by formulating the parameters as a fraction of over the maximum parameters. The normalized charts would be universal for any given TEG module once the thermoelectric material is known.

  1. 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.

  2. Experimental Investigation on Effect of Adhesives on Thermoelectric Generator Performance

    NASA Astrophysics Data System (ADS)

    Singh, Baljit; Remeli, Muhammad Fairuz; Chet, Ding Lai; Oberoi, Amandeep; Date, Abhijit; Akbarzadeh, Aliakbar

    2015-06-01

    Thermoelectric generators (TEGs) convert heat energy into electricity. Currently, these devices are attached to heat exchangers by means of mechanical devices such as clamps or fixtures with nuts and bolts. These mechanical devices are not suitable for use in harsh environments due to problems with rusting and maintenance. To eliminate the need for such mechanical devices, various kinds of adhesives used to attach thermoelectric generators to heat exchangers are investigated experimentally in this work. These adhesives have been selected based on their thermal properties and also their stability to work in harsh environments to avoid damage to the integrity of the attachment over long periods of time. Stainless-steel plates were attached to a thermoelectric generator using the adhesives. The introduction of the adhesive as a means of attachment for thermoelectric generators contributes to increase the thermal resistance to heat transfer across the TEG. The adhesive layers increased the thermal resistance of the thermoelectric generator by 16% to 109%. This work examines the effect of the adhesives on the thermal performance and power output of a single thermoelectric generator for various heat inputs.

  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)

    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.

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

    NASA Astrophysics Data System (ADS)

    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.

  5. 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

  6. Molten gallium flux synthesis of known thermoelectric and novel magnetic inorganic clathrate compounds: Improving thermoelectric performance

    NASA Astrophysics Data System (ADS)

    Bryan, John Daniel

    Molten gallium metal has been used as a solvent to grow large single crystals of known inorganic thermoelectric clathrates Sr8Ga 16Ge30, Ba8Ga16Ge30, and Ba8Ga16Si30. X-ray diffraction, thermal analysis, electron microprobe, Glow Discharge Mass Spectrometry, temperature dependent electrical conductivity and Seebeck coefficient measurements characterized the single crystals. The Thermoelectric performance was shown to be heavily dependent on the synthetic conditions including container choice, thermal history and impurity concentration. Inorganic Clathrates have attracted intense interest in last several years as potential new materials for thermoelectric devices. If a small to moderate increase in thermoelectric performance over the currently used materials is realized, substantial environmental and technological gains could be achieved. Since thermoelectric refrigeration modules require no moving parts or heat exchange gas (freon) they offer significant advantages over conventional refrigeration technology that tends to fail due to the finite lifetime of the pumping equipment. High temperature devices are also extremely useful for power generation in harsh unforgiving environments where excess heat is available. The thermoelectric performance, primarily at room temperature, of these compounds was found to be heavily dependent on the synthetic procedures used to obtain them. A flux growth procedure was developed to overcome the problems of the traditional melt-quench-anneal solid-state chemical approach. This procedure yielded large single crystals of the Sr8Ga16Ge 30, Ba8Ga16Ge30 and Ba8Ga 16Si30 compounds which ready facilitated their chemical and electronic study. Finally, an outlook on the application of these compounds as thermoelectric devices is given. Application of the flux method to other systems was also successful in the discovery of two new inorganic clathrate compounds: type IV Eu4Ga 8Ge16 and type V Yb8Ga16Ge14. The Eu4Ga8Ge16 compound was found to

  7. 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.

  8. Thermoelectric performance enhancement of Mg2Sn based solid solutions by band convergence and phonon scattering via Pb and Si/Ge substitution for Sn.

    PubMed

    Mao, Jun; Wang, Yumei; Ge, Binghui; Jie, Qing; Liu, Zihang; Saparamadu, Udara; Liu, Weishu; Ren, Zhifeng

    2016-07-27

    In this study, the thermoelectric properties of Mg2Sn0.98-xPbxSb0.02 were first studied, and then Mg2Sn0.93-xSixPb0.05Sb0.02 and Mg2Sn0.93-xGexPb0.05Sb0.02 were accordingly investigated. The results showed that the formation of Mg2Sn0.98-xPbxSb0.02 solid solutions effectively reduced the lattice thermal conductivity of Mg2Sn. The room temperature lattice thermal conductivity of Mg2Sn0.98Sb0.02 is ∼5.2 W m(-1) K(-1) but only ∼2.5 W m(-1) K(-1) for Mg2Sn0.73Pb0.25Sb0.02, a reduction of ∼52%. Further alloying Mg2Sn0.98-xPbxSb0.02 with Mg2Si or Mg2Ge to form Mg2Sn0.93-xSixPb0.05Sb0.02 or Mg2Sn0.93-xGexPb0.05Sb0.02 reduced the lattice thermal conductivity significantly due to enhanced phonon scattering by point defects as well as nanoparticles. Moreover, bipolar thermal conductivities were suppressed due to the larger bandgap of Mg2Si and Mg2Ge than Mg2Sn. Furthermore, similar to the pseudo-binary Mg2Sn-Mg2Si and Mg2Sn-Mg2Ge systems, band convergence was also observed in pseudo-ternary Mg2Sn0.93-xSixPb0.05Sb0.02 and Mg2Sn0.93-xGexPb0.05Sb0.02 materials. The convergence of conduction bands led to higher PFs at lower temperatures for Mg2Sn0.93-xSixPb0.05Sb0.02 and Mg2Sn0.93-xGexPb0.05Sb0.02 materials. As a result, higher peak ZTs of ∼1.3 for Mg2Sn0.63Si0.3Pb0.05Sb0.02 and ∼1.2 for Mg2Sn0.68Ge0.25Pb0.05Sb0.02 were achieved. PMID:27412367

  9. Optimization of thermoelectric performance in semiconducting polymers for understanding charge transport and flexible thermoelectric applications

    NASA Astrophysics Data System (ADS)

    Glaudell, Anne; Chabinyc, Michael

    2014-03-01

    Organic electronic materials have been widely considered for a variety of energy conversion applications, from photovoltaics to LEDs. Only very recently have organic materials been considered for thermoelectric applications - converting between temperature gradients and electrical potential. The intrinsic disorder in semiconducting polymers leads to an inherently low thermal conductivity, a key parameter in thermoelectric performance. The ability to solution deposit on flexible substrates opens up niche applications including personal cooling and conformal devices. Here work is presented on the electrical conductivity and thermopower of thin film semiconducting polymers, including P3HT and PBTTT-C14. Thermoelectric properties are explored over a wide range of conductivities, from nearly insulating to beyond 100 S/cm, enabled by employing different doping mechanisms, including molecular charge-transfer doping with F4TCNQ and vapor doping with a fluoroalkyl trichlorosilane (FTS). Temperature-dependent measurements suggest competing charge transport mechanisms, likely due to the mixed ordered/disordered character of these polymers. These results show promise for organic materials for thermoelectric applications, and recent results on thin film devices will also be presented.

  10. Correlation between dimensional crossover and thermoelectric performance in conducting polymer

    NASA Astrophysics Data System (ADS)

    Jo, Junhyeon; Oh, In-Seon; Jin, Mi-Jin; Yoo, Jung-Woo

    Conjugated polymers are emerging as attractive thermoelectric materials, resulting from low thermal conductivity, easy process and variable potentials for change. Recently, there are significant improvements of the Seebeck coefficient (S) and electric conductivity (σ) in the conjugated polymers by adding chemical additives to reform its ordinary disordered structure system. However, the relation between thermoelectricity and charge transport in the system is not well understood, which gives us a new challenge to improve thermoelectricity in the organic system. Here, we studied thermoelectric performance of dimethyl sulfoxide (DMSO) doped poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) with adding variable amounts of fluorosurfactant Zonyl. The charge transport in this disordered system was analyzed within variable range hopping (VRH), which showed the change of hopping dimensionality with further molecular dopants. The morphological change and its effect on charge transport and thermoelectric performance were further investigated through AFM, XPS, etc. As a result, we found the optimal condition for increasing both the Seebeck coefficient and electric conductivity, resulting in a significant improvement for the power factor (S2 σ) .

  11. Ultrahigh power factor and thermoelectric performance in hole-doped single-crystal SnSe.

    PubMed

    Zhao, Li-Dong; Tan, Gangjian; Hao, Shiqiang; He, Jiaqing; Pei, Yanling; Chi, Hang; Wang, Heng; Gong, Shengkai; Xu, Huibin; Dravid, Vinayak P; Uher, Ctirad; Snyder, G Jeffrey; Wolverton, Chris; Kanatzidis, Mercouri G

    2016-01-01

    Thermoelectric technology, harvesting electric power directly from heat, is a promising environmentally friendly means of energy savings and power generation. The thermoelectric efficiency is determined by the device dimensionless figure of merit ZT(dev), and optimizing this efficiency requires maximizing ZT values over a broad temperature range. Here, we report a record high ZT(dev) ∼1.34, with ZT ranging from 0.7 to 2.0 at 300 to 773 kelvin, realized in hole-doped tin selenide (SnSe) crystals. The exceptional performance arises from the ultrahigh power factor, which comes from a high electrical conductivity and a strongly enhanced Seebeck coefficient enabled by the contribution of multiple electronic valence bands present in SnSe. SnSe is a robust thermoelectric candidate for energy conversion applications in the low and moderate temperature range.

  12. Critical Role of Processing on the Thermoelectric Performance of Doped Semiconducting Polymers

    NASA Astrophysics Data System (ADS)

    Patel, Shrayesh; Glaudell, Anne; Chabinyc, Michael

    The ability to convert excess waste heat into useable energy can significantly help meet the global energy demands. One may capture this waste heat through thermoelectrics devices. In a thermoelectric material, the charge carriers transport both electrical current and heat. Consequently, under a temperature difference (ΔT), a carrier concentration gradient results in a voltage (ΔV), which is related to the Seebeck coefficient, α = - Δ V/ ΔT. One of the challenges lies in finding materials that simultaneously have low thermal conductivity (κ) , high electrical conductivity (σ) , and high Seebeck coefficient (α) . Conjugated semiconducting polymers can potentially meet this demand due to their inherent low thermal conductivity and high electrical conductivity through sufficient doping. Here, we report on the critical role of thermal processing on the enhancement of thermoelectric properties of conjugated polymer thin films. These films were doping using three different mechanisms: acid (toluene sulfonic acid), charge transfer (F4TCNQ), and vapor (fluorinated-alkyl trichlorosilane). These thermoelectrics properties will be correlated to the structural and morphological properties of the doped thin-films through various synchrotron X-ray scattering techniques. Lastly, to further elucidate the charge transport mechanism driving the thermoelectric performance, we report on the temperature-dependent measurements of both the Seebeck coefficient and electrical conductivity.

  13. Nanocrystalline silicon: Lattice dynamics and enhanced thermoelectric properties

    SciTech Connect

    Claudio, Tania; Stein, Niklas; Stroppa, Daniel G.; Klobes, Benedikt; Koza, Michael Marek; Kudejova, Petra; Petermann, Nils; Wiggers, Hartmut; Schierning, Gabi; Hermann, Raphaël P.

    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 constants 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.

  14. Nanocrystalline silicon: Lattice dynamics and enhanced thermoelectric properties

    DOE PAGES

    Claudio, Tania; Stein, Niklas; Stroppa, Daniel G.; Klobes, Benedikt; Koza, Michael Marek; Kudejova, Petra; Petermann, Nils; Wiggers, Hartmut; Schierning, Gabi; Hermann, Raphaël P.

    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 constants were measured,more » 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

  15. Nanocrystalline silicon: lattice dynamics and enhanced thermoelectric properties.

    PubMed

    Claudio, Tania; Stein, Niklas; Stroppa, Daniel G; Klobes, Benedikt; Koza, Michael Marek; Kudejova, Petra; Petermann, Nils; Wiggers, Hartmut; Schierning, Gabi; Hermann, Raphaël P

    2014-12-21

    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 constants 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. PMID:24848359

  16. Enhanced Thermoelectric Properties in Tailored Semiconducting SWCNT Networks

    NASA Astrophysics Data System (ADS)

    Avery, A. D.; Zhou, B. H.; Lee, J.; Lee, E.; Miller, E. M.; Ihly, R.; Wesenberg, D.; Mistry, K. S.; Guillot, S. L.; Zink, B. L.; Kim, Y.; Blackburn, J. L.; Ferguson, A. J.

    Single-walled carbon nanotubes (SWCNTs) are a versatile electronic material being explored as cost-effective, high-performance alternative in a variety of renewable energy applications. In this talk, we present a series of experiments designed to probe the thermal and electrical transport through networks of semiconducting SWCNT dispersed in matrices of polyfluorene polymers. We measured electrical transport as a function of hole density to explore the coupling between the electrical conductivity and Seebeck coefficient (thermopower) in the s-SWCNT networks. These networks exhibit large thermopowers > 1000 μV/K at very low hole densities. Thermopower values remain high at high doping levels, resulting in thermoelectric power factors greater than 340 μW/m K. Finally, we present measurements that demonstrate our doping process significantly reduces the thermal conductivity relative to undoped networks suggesting s-SWCNTs are a viable material for realizing thermally stable room temperature thermoelectric devices fashioned from inexpensive and abundant organic constituents.

  17. Enhanced thermoelectric performance in the p-type half-Heusler (Ti/Zr/Hf)CoSb0.8Sn0.2 system via phase separation.

    PubMed

    Rausch, Elisabeth; Balke, Benjamin; Ouardi, Siham; Felser, Claudia

    2014-12-14

    A novel approach for optimization of the thermoelectric properties of p-type Heusler compounds with a C1b structure was investigated. A successful recipe for achieving intrinsic phase separation in the n-type material based on the TiNiSn system is isoelectronic partial substitution of Ti with its heavier homologues Zr and Hf. We applied this concept to the p-type system MCoSb0.8Sn0.2 by a systematic investigation of samples with different compositions at the Ti position (M = Ti, Zr, Hf, Ti0.5Zr0.5, Zr0.5Hf0.5, and Ti0.5Hf0.5). We thus achieved an approximately 40% reduction of the thermal conductivity and a maximum figure of merit ZT of 0.9 at 700 °C. This is a 80% improvement in peak ZT from 0.5 to 0.9 at 700 °C compared to the best published value of an ingot p-type half-Heusler compound. Thus far, comparable good thermoelectric p-type materials of this structure type have only been realized by a nanostructuring process via ball milling of premelted ingot samples followed by a rapid consolidation method, like hot pressing. The herein-presented simple arc-melting fabrication method reduces the fabrication time as compared to this multi-step nanostructuring process. The high mechanical stability of the Heusler compounds is favorable for the construction of thermoelectric modules. The Vickers hardness values are close to those of the n-type material, leading to good co-processability of both materials.

  18. Air-tolerant Fabrication and Enhanced Thermoelectric Performance of n-Type Single-walled Carbon Nanotubes Encapsulating 1,1'-Bis(diphenylphosphino)ferrocene.

    PubMed

    Nonoguchi, Yoshiyuki; Iihara, Yu; Ohashi, Kenji; Murayama, Tomoko; Kawai, Tsuyoshi

    2016-09-01

    The thermally-triggered n-type doping of single-walled carbon nanotubes is demonstrated using 1,1'-bis(diphenylphosphino)ferrocene, a novel n-type dopant. Through a simple thermal vacuum process, the phosphine compounds are moderately encapsulated inside single-walled carbon nanotubes. The encapsulation into SWNTs is carefully characterized using Raman/X-ray spectroscopy and transmission electron microscopy. This easy-to-handle doping with air-stable precursors for n-type SWNTs enables the large-scale fabrication of thermoelectric materials showing an excellent power factor exceeding approximately 240 μW mK(-2) .

  19. Air-tolerant Fabrication and Enhanced Thermoelectric Performance of n-Type Single-walled Carbon Nanotubes Encapsulating 1,1'-Bis(diphenylphosphino)ferrocene.

    PubMed

    Nonoguchi, Yoshiyuki; Iihara, Yu; Ohashi, Kenji; Murayama, Tomoko; Kawai, Tsuyoshi

    2016-09-01

    The thermally-triggered n-type doping of single-walled carbon nanotubes is demonstrated using 1,1'-bis(diphenylphosphino)ferrocene, a novel n-type dopant. Through a simple thermal vacuum process, the phosphine compounds are moderately encapsulated inside single-walled carbon nanotubes. The encapsulation into SWNTs is carefully characterized using Raman/X-ray spectroscopy and transmission electron microscopy. This easy-to-handle doping with air-stable precursors for n-type SWNTs enables the large-scale fabrication of thermoelectric materials showing an excellent power factor exceeding approximately 240 μW mK(-2) . PMID:27439731

  20. 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.

  1. Significant enhancement of the thermoelectric figure of merit of polycrystalline Si films by reducing grain size

    NASA Astrophysics Data System (ADS)

    Valalaki, K.; Vouroutzis, N.; Nassiopoulou, A. G.

    2016-08-01

    The thermoelectric properties of p-type polycrystalline silicon thin films deposited by low pressure chemical vapour deposition (LPCVD) were accurately determined at room temperature and the thermoelectric figure of merit was deduced as a function of film thickness, ranging from 100 to 500 nm. The effect of film thickness on their thermoelectric performance is discussed. More than threefold increase in the thermoelectric figure of merit of the 100 nm thick polysilicon film was observed compared to the 500 nm thick film, reaching a value as high as 0.033. This enhancement is mainly the result of the smaller grain size in the thinner films. With the decrease in grain size the resistivity of the films is increased twofold and electrical conductivity decreased, however the Seebeck coefficient is increased by 30% and the thermal conductivity is decreased eightfold, being mainly at the origin of the increased figure of merit of the 100 nm film. Our experimental results were compared to known theoretical models and the possible mechanisms involved are presented and discussed.

  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

    2015-04-01

    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. PMID:25838382

  3. 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

    2015-04-01

    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.

  4. Nanostructures boost the thermoelectric performance of PbS

    SciTech Connect

    Johnsen, Simon; He, Jiaqing; Androulakis, John; Dravid, Vinayak; Todorov, Iliya; Chung, Duck Young; Kanatzidis, Mercouri G.

    2011-02-18

    In situ nanostructuring in bulk thermoelectric materials through thermo-dynamic phase segregation has established itself as an effective paradigm for optimizing the performance of thermoelectric materials. In bulk PbTe small compositional variations create coherent and semicoherent nanometer sized precipitates embedded in a PbTe matrix, where they can impede phonon propagation at little or no expense to the electronic properties. In this paper the nanostructuring paradigm is for the first time extended to a bulk PbS based system, which despite obvious advantages of price and abundancy, so far has been largely disregarded in thermoelectric research due to inferior room temperature thermoelectric properties relative to the pristine fellow chalcogenides, PbSe and PbTe. Herein we report on the synthesis, microstructural morphology and thermoelectric properties of two phase (PbS)1-x(PbTe)xx = 0–0.16 samples. We have found that the addition of only a few percent PbTe to PbS results in a highly nanostructured material, where PbTe precipitates are coherently and semicoherently embedded in a PbS matrix. The present (PbS)1-x(PbTe)x nanostructured samples show substantial decreases in lattice thermal conductivity relative to pristine PbS, while the electronic properties are left largely unaltered. This in turn leads to a marked increase in the thermoelectric figure of merit. This study underlines the efficiency of the nanostructuring approach and strongly supports its generality and applicability to other material systems. We demonstrate that these PbS-based materials, which are made primarily from abundant Pb and S, outperform optimally n-type doped pristine PbTe above 770 K.

  5. 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.

  6. Mechanical robust BiSbTe alloys with superior thermoelectric performance: A case study of stable hierarchical nanostructured thermoelectric materials

    NASA Astrophysics Data System (ADS)

    Su, Xianli; Zheng, Yun; Tang, Xinfeng; Uher, Ctirad; Tang's Group Team; Uher's Group Team

    2015-03-01

    Poor machinability and susceptibility to brittle fracture of commercial ingots often impose significant limitations on the manufacturing process and durability of thermoelectric devices. In this study, melt spinning combined with plasma activated sintering (MS-PAS) method is employed with commercial p-type zone-melted (ZM) ingots of Bi0.5Sb1.5Te3. This fast synthesis approach achieves hierarchical structures and in-situ nanoscale precipitates, resulting in the simultaneous improvement of thermoelectric performance and mechanical properties. Benefitting from a strong suppression of the lattice thermal conductivity, a peak ZT of 1.22 is achieved at 340 K in MS-PAS synthesized structures, representing about a 40% enhancement over that of ZM ingots. Moreover, MS-PAS specimens with hierarchical structures exhibit superior machinability and mechanical properties with an almost 30% enhancement in the fracture toughness, eightfold and a factor of six increase in the compressive and flexural strength respectively. We wish to acknowledge support from the National Basic Research Program of China (973 program) under Project 2013CB632502.

  7. Enhanced Thermoelectricity in High-Temperature β-Phase Copper(I) Selenides Embedded with Cu2Te Nanoclusters.

    PubMed

    Butt, Sajid; Xu, Wei; Farooq, Muhammad U; Ren, Guang K; Zhang, Qinghua; Zhu, Yingcai; Khan, Sajid U; Liu, Lijuan; Yu, Meijuan; Mohmed, Fida; Lin, Yuanhua; Nan, Ce-Wen

    2016-06-22

    We report remarkably enhanced thermoelectric performance of Te doped Cu2Se in midtemperature range. Through ball-milling process followed by spark plasma sintering (SPS), nanoscale Cu2Te clusters were embeded in the matrix of Cu2Se, inducing a drastic enhancement of thermoelectric performance by reducing the thermal conductivity without degrading the power factor. A large ZT value of 1.9 was achieved at 873 K for Cu2Se1.9Te0.1, which is about 2 times larger than that of the pure Cu2Se. The nanoscale heat management by Cu2Te nanoclusters in superionic conductors opens up an avenue for thermoelectric materials research. PMID:27135808

  8. A Facile Surfactant-Assisted Reflux Method for the Synthesis of Single-Crystalline Sb2Te3 Nanostructures with Enhanced Thermoelectric Performance.

    PubMed

    Yang, Heng Quan; Miao, Lei; Liu, Cheng Yan; Li, Chao; Honda, Sawao; Iwamoto, Yuji; Huang, Rong; Tanemura, Sakae

    2015-07-01

    Antimony telluride (Sb2Te3) and its based alloys are of importance to p-type semiconductors for thermoelectric applications near room temperature. Herein, we report a simple, low-energy intensive, and scalable surfactant-assisted reflux method for the synthesis of Sb2Te3 nanoparticles in the solvent ethylene glycol (EG) at low temperatures (120-180 °C). The formation mechanism of platelike Sb2Te3 nanoparticles is proposed. Also, it is found that the size, shape, and chemical composition of the products could be controlled by the introduction of organic surfactants (CTAB, PVP, etc.) or inorganic salts (EDTA-Na2, NaOH, etc.). Additionally, the collected Sb2Te3 nanoparticles were further fabricated into nanostructured pellets using cold-compaction and annealing techniques. Low resistivity [(7.37-19.4) × 10(-6) Ω m], moderate Seebeck coefficient (103-141 μV K(-1)), and high power factor (10-16 × 10(-4) W m(-1) K(-2)) have been achieved in our Sb2Te3-nanostructured bulk materials. The relatively low thermal conductivity (1.32-1.55 W m(-1) K(-1)) is attained in the nanobulk made of PVP-modified nanoparticles, and values of ZT in the range of 0.24-0.37 are realized at temperatures ranging from 50 to 200 °C. Our researches set forth a new avenue in promoting practical applications of Sb2Te3-based thermoelectric power generation or cooling devices. PMID:26060933

  9. 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

  10. 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.

  11. High Thermoelectric Performance in Copper Telluride

    SciTech Connect

    He, Ying; Zhang, Tiansong; Shi, Xun; Wei, Su-Huai; Chen, Lidong

    2015-06-21

    Recently, Cu 2-δ S and Cu 2-δ Se were reported to have an ultralow thermal conductivity and high thermoelectric figure of merit zT. Thus, as a member of the copper chalcogenide group, Cu 2-δ Te is expected to possess superior zTs because Te is less ionic and heavy. However, the zT value is low in the Cu2Te sintered using spark plasma sintering, which is typically used to fabricate high-density bulk samples. In addition, the extra sintering processes may change the samples’ compositions as well as their physical properties, especially for Cu2Te, which has many stable and meta-stable phases as well as weaker ionic bonding between Cu and Te as compared with Cu2S and Cu2Se. In this study, high-density Cu2Te samples were obtained using direct annealing without a sintering process. In the absence of sintering processes, the samples’ compositions could be well controlled, leading to substantially reduced carrier concentrations that are close to the optimal value. The electrical transports were optimized, and the thermal conductivity was considerably reduced. The zT values were significantly improved—to 1.1 at 1000 K—which is nearly 100% improvement. Furthermore, this method saves substantial time and cost during the sample’s growth. The study demonstrates that Cu 2-δ X (X=S, Se and Te) is the only existing system to show high zTs in the series of compounds composed of three sequential primary group elements.

  12. High Thermoelectric Performance in Copper Telluride

    DOE PAGES

    He, Ying; Zhang, Tiansong; Shi, Xun; Wei, Su-Huai; Chen, Lidong

    2015-06-21

    Recently, Cu 2-δ S and Cu 2-δ Se were reported to have an ultralow thermal conductivity and high thermoelectric figure of merit zT. Thus, as a member of the copper chalcogenide group, Cu 2-δ Te is expected to possess superior zTs because Te is less ionic and heavy. However, the zT value is low in the Cu2Te sintered using spark plasma sintering, which is typically used to fabricate high-density bulk samples. In addition, the extra sintering processes may change the samples’ compositions as well as their physical properties, especially for Cu2Te, which has many stable and meta-stable phasesmore » as well as weaker ionic bonding between Cu and Te as compared with Cu2S and Cu2Se. In this study, high-density Cu2Te samples were obtained using direct annealing without a sintering process. In the absence of sintering processes, the samples’ compositions could be well controlled, leading to substantially reduced carrier concentrations that are close to the optimal value. The electrical transports were optimized, and the thermal conductivity was considerably reduced. The zT values were significantly improved—to 1.1 at 1000 K—which is nearly 100% improvement. Furthermore, this method saves substantial time and cost during the sample’s growth. The study demonstrates that Cu 2-δ X (X=S, Se and Te) is the only existing system to show high zTs in the series of compounds composed of three sequential primary group elements.« less

  13. Enhanced power factor and high-pressure effects in (Bi,Sb){sub 2}(Te,Se){sub 3} thermoelectrics

    SciTech Connect

    Ovsyannikov, Sergey V. E-mail: sergey2503@gmail.com; Morozova, Natalia V.; Korobeinikov, Igor V.; Vokhmyanin, Alexander P.; Shchennikov, Vladimir V.; Lukyanova, Lidia N.; Usov, Oleg A.; Kutasov, Vsevolod A.; Manakov, Andrey Y.; Likhacheva, Anna Y.; Ancharov, Alexey I.; Berger, Ivan F.; Kulbachinskii, Vladimir A.; Okada, Taku

    2015-04-06

    We investigated the effects of applied high pressure on thermoelectric, electric, structural, and optical properties of single-crystalline thermoelectrics, Bi{sub 2}Te{sub 3}, Bi{sub x}Sb{sub 2−x}Te{sub 3} (x = 0.4, 0.5, 0.6), and Bi{sub 2}Te{sub 2.73}Se{sub 0.27} with the high thermoelectric performance. We established that moderate pressure of about 2–4 GPa can greatly enhance the thermoelectric power factor of all of them. X-ray diffraction and Raman studies on Bi{sub 2}Te{sub 3} and Bi{sub 0.5}Sb{sub 1.5}Te{sub 3} found anomalies at similar pressures, indicating a link between crystal structure deformation and physical properties. We speculate about possible mechanisms of the power factor enhancement and suppose that pressure/stress tuning can be an effective tool for the optimization of the thermoelectric performance.

  14. High thermoelectric performance of the distorted bismuth(110) layer.

    PubMed

    Cheng, L; Liu, H J; Zhang, J; Wei, J; Liang, J H; Jiang, P H; Fan, D D; Sun, L; Shi, J

    2016-07-14

    The thermoelectric properties of the distorted bismuth(110) layer are investigated using first-principles calculations combined with the Boltzmann transport equation for both electrons and phonons. To accurately predict the electronic and transport properties, the quasiparticle corrections with the GW approximation of many-body effects have been explicitly included. It is found that a maximum ZT value of 6.4 can be achieved for n-type systems, which essentially stemmed from the weak scattering of electrons. Moreover, we demonstrate that the distorted Bi layer retains high ZT values in relatively broad regions of both temperature and carrier concentration. Our theoretical work emphasizes that the deformation potential constant characterizing the electron-phonon scattering strength is an important paradigm for searching high thermoelectric performance materials. PMID:27302907

  15. Enhanced thermoelectric power and electronic correlations in RuSe₂

    DOE PAGES

    Wang, Kefeng; Wang, Aifeng; Tomic, A.; Wang, Limin; Abeykoon, A. M. Milinda; Dooryhee, E.; Billinge, S. J.L.; Petrovic, C.

    2015-03-03

    We report the electronic structure, electric and thermal transport properties of Ru₁₋xIrxSe₂ (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. Ru₀.₈Ir₀.₂Se₂ 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.

  16. Enhanced thermoelectric power and electronic correlations in RuSe₂

    SciTech Connect

    Wang, Kefeng; Wang, Aifeng; Tomic, A.; Wang, Limin; Abeykoon, A. M. Milinda; Dooryhee, E.; Billinge, S. J.L.; Petrovic, C.

    2015-03-03

    We report the electronic structure, electric and thermal transport properties of Ru₁₋xIrxSe₂ (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. Ru₀.₈Ir₀.₂Se₂ 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 performance of spin Seebeck effect in Fe3O4/Pt-based thin film heterostructures

    NASA Astrophysics Data System (ADS)

    Ramos, R.; Anadón, A.; Lucas, I.; Uchida, K.; Algarabel, P. A.; Morellón, L.; Aguirre, M. H.; Saitoh, E.; Ibarra, M. R.

    2016-10-01

    We report a systematic study on the thermoelectric performance of spin Seebeck devices based on Fe3O4/Pt junction systems. We explore two types of device geometries: a spin Hall thermopile and spin Seebeck multilayer structures. The spin Hall thermopile increases the sensitivity of the spin Seebeck effect, while the increase in the sample internal resistance has a detrimental effect on the output power. We found that the spin Seebeck multilayers can overcome this limitation since the multilayers exhibit the enhancement of the thermoelectric voltage and the reduction of the internal resistance simultaneously, therefore resulting in significant power enhancement. This result demonstrates that the multilayer structures are useful for improving the thermoelectric performance of the spin Seebeck effect.

  18. Modeling and theoretical efficiency of a silicon nanowire based thermoelectric junction with area enhancement

    NASA Astrophysics Data System (ADS)

    Seong, M.; Sadhu, J. S.; Ma, J.; Ghossoub, M. G.; Sinha, S.

    2012-06-01

    Recent experimental work suggests that individual silicon nanowires with rough surfaces possess a thermoelectric figure of merit as high as 0.6 near room temperature. This paper addresses the possibility of using an array of such nanowires in a thermoelectric junction for generation. Employing a model of frequency dependent phonon boundary scattering, we estimate the effective thermal conductivity of the array and investigate heat flow through the junction. We show that charge transport is largely unaffected by the roughness scales considered. Enhancing the area for heat exchange at an individual 200 μm × 200 μm p-n junction yields significant temperature differences across the junction leading to power >0.6 mW and efficiency >1.5% for a junction with effective thermal conductivity <5 W/mK, when the source and sink are at 450 K and 300 K, respectively. We show that relatively short nanowires of ˜50 μm length are sufficient for obtaining peak power and reasonable efficiency. This substantially reduces the challenge of engineering low resistivity electrical contacts that critically affect power and efficiency. This paper provides insight into how fundamental transport in relation to bulk heat transfer and charge transport, affects the performance of thermoelectric junctions based on nanostructured materials.

  19. Modeling and theoretical efficiency of a silicon nanowire based thermoelectric junction with area enhancement

    SciTech Connect

    Seong, M; Sadhu, JS; Ma, J; Ghossoub, MG; Sinha, S

    2012-06-15

    Recent experimental work suggests that individual silicon nanowires with rough surfaces possess a thermoelectric figure of merit as high as 0.6 near room temperature. This paper addresses the possibility of using an array of such nanowires in a thermoelectric junction for generation. Employing a model of frequency dependent phonon boundary scattering, we estimate the effective thermal conductivity of the array and investigate heat flow through the junction. We show that charge transport is largely unaffected by the roughness scales considered. Enhancing the area for heat exchange at an individual 200 mu m x 200 mu m p-n junction yields significant temperature differences across the junction leading to power >0.6 mW and efficiency >1.5% for a junction with effective thermal conductivity <5 W/mK, when the source and sink are at 450 K and 300 K, respectively. We show that relatively short nanowires of similar to 50 mu m length are sufficient for obtaining peak power and reasonable efficiency. This substantially reduces the challenge of engineering low resistivity electrical contacts that critically affect power and efficiency. This paper provides insight into how fundamental transport in relation to bulk heat transfer and charge transport, affects the performance of thermoelectric junctions based on nanostructured materials. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4728189

  20. Spectacular enhancement of thermoelectric phenomena in chemically synthesized graphene nanoribbons with substitution atoms.

    PubMed

    Zberecki, K; Swirkowicz, R; Wierzbicki, M; Barnaś, J

    2016-07-21

    We analyze theoretically the transport and thermoelectric properties of graphene nanoribbons of a specific geometry, which have been synthesized recently from polymers [Cai, et al., Nature, 2011, 466, 470]. When such nanoribbons are modified at one of the two edges by Al or N substitutions, they acquire a ferromagnetic moment localized at the modified edge. We present numerical results on the electronic structure and thermoelectric properties (including also spin thermoelectricity) of the modified nanoribbons. The results show that such nanoribbons can display large thermoelectric efficiency in certain regions of chemical potential, where the corresponding electric and spin figures of merit achieve unusually large values. The enhancement of thermoelectric efficiency follows from a reduced phonon heat conductance of the nanoribbons and from their peculiar electronic band structure. Thus, such nanoribbons are promising for practical applications in nanoelectronic and spintronic devices. PMID:27331357

  1. Methods for Enhancing the Thermal Durability of High-Temperature Thermoelectric Materials

    NASA Astrophysics Data System (ADS)

    Skomedal, Gunstein; Kristiansen, Nils R.; Engvoll, Marianne; Middleton, Hugh

    2014-06-01

    Thermoelectric materials, for example skutterudites and magnesium silicides, are being investigated as promising materials for medium-to-high-temperature waste heat recovery in transport and in industry. A crucial aspect of the success of a thermoelectric material is its stability over time when exposed to rapid heating and cooling. In this work different aspects of the degradation of these thermoelectric materials at high temperature were examined. Initial thermal durability was studied, and several candidate coatings were evaluated to enhance durability by protecting the materials from oxidation and sublimation during thermal cycles in air for up to 500 h and up to 873 K. The samples were characterized by SEM and EDS. The results showed it is possible to reduce degradation of the thermoelectric material without compromising overall thermoelectric efficiency.

  2. Spectacular enhancement of thermoelectric phenomena in chemically synthesized graphene nanoribbons with substitution atoms.

    PubMed

    Zberecki, K; Swirkowicz, R; Wierzbicki, M; Barnaś, J

    2016-07-21

    We analyze theoretically the transport and thermoelectric properties of graphene nanoribbons of a specific geometry, which have been synthesized recently from polymers [Cai, et al., Nature, 2011, 466, 470]. When such nanoribbons are modified at one of the two edges by Al or N substitutions, they acquire a ferromagnetic moment localized at the modified edge. We present numerical results on the electronic structure and thermoelectric properties (including also spin thermoelectricity) of the modified nanoribbons. The results show that such nanoribbons can display large thermoelectric efficiency in certain regions of chemical potential, where the corresponding electric and spin figures of merit achieve unusually large values. The enhancement of thermoelectric efficiency follows from a reduced phonon heat conductance of the nanoribbons and from their peculiar electronic band structure. Thus, such nanoribbons are promising for practical applications in nanoelectronic and spintronic devices.

  3. Effect of microstructure on the thermoelectric performance of La1-xSrxCoO3

    NASA Astrophysics Data System (ADS)

    Viskadourakis, Z.; Athanasopoulos, G. I.; Kasotakis, E.; Giapintzakis, J.

    2016-11-01

    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 La1-xSrxCoO3 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 the 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.

  4. Prospects for improvement in LED performance using thermoelectrics

    NASA Astrophysics Data System (ADS)

    Semenyuk, V.; Dekhtiaruk, R.

    2012-06-01

    A generalized approach to cooling of localized heat sources is given with emphasis on light emitting diodes (LEDs) thermal management. Considered is the thermal model of the system containing a LED with its internal thermal resistance, thermoelectric cooler (TEC) and a heat sink. The problem of optimal matching of system components is solved with consideration of 3-dimensional heat spreading in the system elements. The method of optimal integration of a TEC into the system is described. Particularly, the LED with the maximum power of 11.8 W is under consideration. It is shown that with optimized TEC the LED performance can be increased considerably.

  5. Performance Prediction of Commercial Thermoelectric Cooler Modules using the Effective Material Properties

    NASA Astrophysics Data System (ADS)

    Lee, HoSung; Attar, Alaa M.; Weera, Sean L.

    2015-06-01

    This work examines the validity of formulating the effective thermoelectric material properties as a way to predict thermoelectric module performance. The three maximum parameters (temperature difference, current, and cooling power) of a thermoelectric cooler were formulated on the basis of the hot junction temperature. Then, the effective material properties (Seebeck coefficient, electrical resistance, and thermal conductivity) were defined in terms of the three maximum parameters that were taken from either a commercial thermoelectric cooler module or the measurements. It is demonstrated that the simple standard equation with the effective material properties predicts well the performance curves of the four selected commercial products. Normalized parameters over the maximum parameters were also formulated to present the characteristics of the thermoelectric coolers along with the normalized charts. The normalized charts would be universal for a given thermoelectric material.

  6. Thermoelectric power enhancement by way of flow impedance for fixed thermal input conditions

    NASA Astrophysics Data System (ADS)

    Amaral, Calil; Brandão, Caio; Sempels, Éric V.; Lesage, Frédéric J.

    2014-12-01

    Liquid-to-liquid thermoelectric generators are now being considered for the purpose of converting low cost heat to electricity for local energy uses. The importance in investigating their system efficiency lies in the fact that the generator's purpose is to maintain a heat source and a heat sink for its embedded thermoelectric modules. Of particular importance is the generator's ability to maintain an asymmetric thermal field across its embedded modules since this mechanism partially dictates the devices' thermal to electric conversion efficiency. Indeed, since the modules' semiconductor materials' ability to generate an electromotive force is dependent on the quality of the thermal dipole across the material, gains in thermoelectric generator energy conversion efficiency are made possible with thermal system management. In an effort to improve the system conversion efficiency of a liquid-to-liquid thermoelectric generator (TEG), the present work builds upon recent advancements in TEG inner pipe flow optimisation by investigating the thermoelectric power enhancement brought upon by flow impeding panel inserts in a thermoelectric generator's flow channels for fixed thermal input conditions and with respect to varying insert panel densities. The pumping penalty associated with the flow impedance is measured in order to present and to discuss the net thermoelectric power enhancement.

  7. Enhanced thermoelectric power of single-wall carbon nanotube film blended with ionic liquid

    NASA Astrophysics Data System (ADS)

    Horike, Shohei; Misaki, Masahiro; Koshiba, Yasuko; Saito, Takeshi; Ishida, Kenji

    2016-03-01

    We have investigated the thermoelectric power of single-wall carbon nanotubes (SWCNTs) with an ionic liquid (IL). The SWCNT/IL films showed simultaneous increase in electrical conductivity and the Seebeck coefficient compared with the pristine SWCNT. No thermoelectric power was observed for the IL. The X-ray diffraction pattern and impedance diagram showed a unique behavior with the concentration of IL, which implies that the interaction between the SWCNTs and IL enhances the thermoelectric power of the SWCNTs. As a result of the simultaneous increase in these parameters, the power factor exhibited a 10-fold increase.

  8. 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.

  9. Rational synthesis of ultrathin n-type Bi2Te3 nanowires with enhanced thermoelectric properties.

    PubMed

    Zhang, Genqiang; Kirk, Benjamin; Jauregui, Luis A; Yang, Haoran; Xu, Xianfan; Chen, Yong P; Wu, Yue

    2012-01-11

    A rational yet scalable solution phase method has been established, for the first time, to obtain n-type Bi(2)Te(3) ultrathin nanowires with an average diameter of 8 nm in high yield (up to 93%). Thermoelectric properties of bulk pellets fabricated by compressing the nanowire powder through spark plasma sintering have been investigated. Compared to the current commercial n-type Bi(2)Te(3)-based bulk materials, our nanowire devices exhibit an enhanced ZT of 0.96 peaked at 380 K due to a significant reduction of thermal conductivity derived from phonon scattering at the nanoscale interfaces in the bulk pellets, which corresponds to a 13% enhancement compared to that of the best n-type commercial Bi(2)Te(2.7)Se(0.3) single crystals (~0.85) and is comparable to the best reported result of n-type Bi(2)Te(2.7)Se(0.3) sample (ZT = 1.04) fabricated by the hot pressing of ball-milled powder. The uniformity and high yield of the nanowires provide a promising route to make significant contributions to the manufacture of nanotechnology-based thermoelectric power generation and solid-state cooling devices with superior performance in a reliable and a reproducible way.

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

    SciTech Connect

    Ali, Zulfiqar; Cao, Chuanbao Butt, Faheem K.; Tahir, Muhammad; Tanveer, M.; Aslam, Imran; Rizwan, Muhammad; Idrees, Faryal; Khalid, Syed; Butt, Sajid

    2014-11-15

    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 approximately 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.

  11. Minority carrier blocking to enhance the thermoelectric figure of merit in narrow-band-gap semiconductors

    NASA Astrophysics Data System (ADS)

    Bahk, Je-Hyeong; Shakouri, Ali

    2016-04-01

    We present detailed theoretical predictions on the enhancement of the thermoelectric figure of merit by minority carrier blocking with heterostructure barriers in bulk narrow-band-gap semiconductors. Bipolar carrier transport, which is often significant in a narrow-band-gap material, is detrimental to the thermoelectric energy conversion efficiency as it suppresses the Seebeck coefficient and increases the thermal conductivity. When the minority carriers are selectively prevented from participating in conduction while the transport of majority carriers is relatively unaffected by one-sided heterobarriers, the thermoelectric figure of merit can be drastically enhanced. Thermoelectric transport properties such as Seebeck coefficient, electrical conductivity, and electronic thermal conductivity including the bipolar term are calculated with and without the barriers based on the near-equilibrium Boltzmann transport equations under the relaxation time approximation to investigate the effects of minority carrier barriers on the thermoelectric figure of merit. For this, we provide details of carrier transport modeling and fitting results of experimental data for three important material systems, B i2T e3 -based alloys, M g2S i1 -xS nx , and S i1 -xG ex , that represent, respectively, near-room-temperature (300 K-500 K), midtemperature (600 K-900 K), and high-temperature (>1000 K ) applications. Theoretical maximum enhancement of thermoelectric figure of merit that can be achieved by minority carrier blocking is quantified and discussed for each of these semiconductors.

  12. 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.

  13. Ultrahigh-Power-Factor Carbon Nanotubes and an Ingenious Strategy for Thermoelectric Performance Evaluation.

    PubMed

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

    2016-07-01

    An ingenious strategy is put forward to evaluate accurately the thermoelectric performance of carbon nanotube (CNT) thin films, including thermal conductivity, electrical conductivity, and Seebeck coefficient in the same direction. The results reveal that the as-prepared CNT interconnected films and CNT fibers possess enormous potential of thermoelectric applications because of their ultrahigh power factors. PMID:27199099

  14. Numerical Examination of the Performance of a Thermoelectric Cooler with Peltier Heating and Cooling

    NASA Astrophysics Data System (ADS)

    Kim, Chang Nyung; Kim, Jeongho

    2015-10-01

    There has recently been much progress in the development of materials with higher thermoelectric performance, leading to the design of thermoelectric devices for generation of electricity and for heating or cooling. Local heating can be achieved by current flow through an electric resistance, and local heating and cooling can be performed by Peltier heating and cooling. In this study, we developed computer software that can be used to predict the Seebeck and Peltier effects for thermoelectric devices. The temperature, electric potential, heat flow, electric current, and coefficient of performance were determined, with the objective of investigating the Peltier effect in a thermoelectric device. In addition to Peltier heating and cooling, Joule and Thomson heating were quantitatively evaluated for the thermoelectric device.

  15. Enhanced thermoelectric power in two-dimensional transition metal dichalcogenide monolayers

    NASA Astrophysics Data System (ADS)

    Pu, Jiang; Kanahashi, Kaito; Cuong, Nguyen Thanh; Chen, Chang-Hsiao; Li, Lain-Jong; Okada, Susumu; Ohta, Hiromichi; Takenobu, Taishi

    2016-07-01

    The carrier-density-dependent conductance and thermoelectric properties of large-area Mo S2 and WS e2 monolayers are simultaneously investigated using the electrolyte gating method. The sign of the thermoelectric power changes across the transistor off-state in the ambipolar WS e2 transistor as the majority carrier density switches from electron to hole. The thermopower and thermoelectric power factor of monolayer samples are one order of magnitude larger than that of bulk materials, and their carrier-density dependences exhibit a quantitative agreement with the semiclassical Mott relation based on the two-dimensional energy band structure, concluding the thermoelectric properties are enhanced by the low-dimensional effect.

  16. 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

  17. 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

    2016-01-01

    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/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. PMID:27615036

  18. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

    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.

  20. 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.

  1. A high performance photothermal film with spherical shell-type metallic nanocomposites for solar thermoelectric conversion

    NASA Astrophysics Data System (ADS)

    Kosuga, Atsuko; Yamamoto, Yasuyuki; Miyai, Moe; Matsuzawa, Mie; Nishimura, Yushi; Hidaka, Shimpei; Yamamoto, Kohei; Tanaka, Shin; Yamamoto, Yojiro; Tokonami, Shiho; Iida, Takuya

    2015-04-01

    A photothermal film (PTF) with densely assembled gold nanoparticle-fixed beads on a polymer substrate is fabricated. Remarkably, a temperature rise higher than 40 °C is achieved in the PTF with only 100 seconds of artificial solar irradiation, and the output power of the thermoelectric device was enhanced to be one order higher than that without PTF. These results will pioneer a rapid solar thermoelectric device.A photothermal film (PTF) with densely assembled gold nanoparticle-fixed beads on a polymer substrate is fabricated. Remarkably, a temperature rise higher than 40 °C is achieved in the PTF with only 100 seconds of artificial solar irradiation, and the output power of the thermoelectric device was enhanced to be one order higher than that without PTF. These results will pioneer a rapid solar thermoelectric device. Electronic supplementary information (ESI) available: Table S1. See DOI: 10.1039/c5nr00943j

  2. Enhanced Molecular Packing of a Conjugated Polymer with High Organic Thermoelectric Power Factor.

    PubMed

    Ma, Wei; Shi, Ke; Wu, Yang; Lu, Zuo-Yu; Liu, Han-Yu; Wang, Jie-Yu; Pei, Jian

    2016-09-21

    The detailed relationship between film morphology and the performance of solution processed n-type organic thermoelectric (TE) devices is investigated. It is interesting to find that the better ordered molecular packing of n-type polymer can be achieved by adding a small fraction of dopant molecules, which is not observed before. The better ordered structure will be favorable for the charge carrier mobility. Meanwhile, dopant molecules improve free carrier concentration via doping reaction. As a result, a significantly enhanced electrical conductivity (12 S cm(-1)) and power factor (25.5 μW m(-1) K(-2)) of TE devices are obtained. Furthermore, the phase separation of conjugated polymer/dopants is observed for the first time with resonant soft X-ray scattering. Our results indicate that the miscibility of conjugated polymers and dopants plays an important role on controlling the morphology and doping efficiency of TE devices.

  3. Enhanced Molecular Packing of a Conjugated Polymer with High Organic Thermoelectric Power Factor.

    PubMed

    Ma, Wei; Shi, Ke; Wu, Yang; Lu, Zuo-Yu; Liu, Han-Yu; Wang, Jie-Yu; Pei, Jian

    2016-09-21

    The detailed relationship between film morphology and the performance of solution processed n-type organic thermoelectric (TE) devices is investigated. It is interesting to find that the better ordered molecular packing of n-type polymer can be achieved by adding a small fraction of dopant molecules, which is not observed before. The better ordered structure will be favorable for the charge carrier mobility. Meanwhile, dopant molecules improve free carrier concentration via doping reaction. As a result, a significantly enhanced electrical conductivity (12 S cm(-1)) and power factor (25.5 μW m(-1) K(-2)) of TE devices are obtained. Furthermore, the phase separation of conjugated polymer/dopants is observed for the first time with resonant soft X-ray scattering. Our results indicate that the miscibility of conjugated polymers and dopants plays an important role on controlling the morphology and doping efficiency of TE devices. PMID:27579521

  4. Numerical and Experimental Investigation for Heat Transfer Enhancement by Dimpled Surface Heat Exchanger in Thermoelectric Generator

    NASA Astrophysics Data System (ADS)

    Wang, Yiping; Li, Shuai; Yang, Xue; Deng, Yadong; Su, Chuqi

    2016-03-01

    For vehicle thermoelectric exhaust energy recovery, the temperature difference between the heat exchanger and the coolant has a strong influence on the electric power generation, and ribs are often employed to enhance the heat transfer of the heat exchanger. However, the introduction of ribs will result in a large unwanted pressure drop in the exhaust system which is unfavorable for the engine's efficiency. Therefore, how to enhance the heat transfer and control the pressure drop in the exhaust system is quite important for thermoelectric generators (TEG). In the current study, a symmetrical arrangement of dimpled surfaces staggered in the upper and lower surfaces of the heat exchanger was proposed to augment heat transfer rates with minimal pressure drop penalties. The turbulent flow characteristics and heat transfer performance of turbulent flow over the dimpled surface in a flat heat exchanger was investigated by numerical simulation and temperature measurements. The heat transfer capacity in terms of Nusselt number and the pressure loss in terms of Fanning friction factors of the exchanger were compared with those of the flat plate. The pressure loss and heat transfer characteristics of dimples with a depth-to-diameter ratio ( h/D) at 0.2 were investigated. Finally, a quite good heat transfer performance with minimal pressure drop heat exchanger in a vehicle TEG was obtained. And based on the area-averaged surface temperature of the heat exchanger and the Seeback effect, the power generation can be improved by about 15% at Re = 25,000 compared to a heat exchanger with a flat surface.

  5. Phase transition enhanced thermoelectric figure-of-merit in copper chalcogenides

    SciTech Connect

    Brown, David R.; Day, Tristan; Snyder, G. Jeffrey; Borup, Kasper A.; Christensen, Sebastian; Iversen, Bo B.

    2013-11-01

    While thermoelectric materials can be used for solid state cooling, waste heat recovery, and solar electricity generation, low values of the thermoelectric figure of merit, zT, have led to an efficiency too low for widespread use. Thermoelectric effects are characterized by the Seebeck coefficient or thermopower, which is related to the entropy associated with charge transport. For example, coupling spin entropy with the presence of charge carriers has enabled the enhancement of zT in cobalt oxides. We demonstrate that the coupling of a continuous phase transition to carrier transport in Cu{sub 2}Se over a broad (360–410 K) temperature range results in a dramatic peak in thermopower, an increase in phonon and electron scattering, and a corresponding doubling of zT (to 0.7 at 406 K), and a similar but larger increase over a wider temperature range in the zT of Cu{sub 1.97}Ag{sub .03}Se (almost 1.0 at 400 K). The use of structural entropy for enhanced thermopower could lead to new engineering approaches for thermoelectric materials with high zT and new green applications for thermoelectrics.

  6. Phase transition enhanced thermoelectric figure-of-merit in copper chalcogenides

    NASA Astrophysics Data System (ADS)

    Brown, David R.; Day, Tristan; Borup, Kasper A.; Christensen, Sebastian; Iversen, Bo B.; Snyder, G. Jeffrey

    2013-11-01

    While thermoelectric materials can be used for solid state cooling, waste heat recovery, and solar electricity generation, low values of the thermoelectric figure of merit, zT, have led to an efficiency too low for widespread use. Thermoelectric effects are characterized by the Seebeck coefficient or thermopower, which is related to the entropy associated with charge transport. For example, coupling spin entropy with the presence of charge carriers has enabled the enhancement of zT in cobalt oxides. We demonstrate that the coupling of a continuous phase transition to carrier transport in Cu2Se over a broad (360-410 K) temperature range results in a dramatic peak in thermopower, an increase in phonon and electron scattering, and a corresponding doubling of zT (to 0.7 at 406 K), and a similar but larger increase over a wider temperature range in the zT of Cu1.97Ag.03Se (almost 1.0 at 400 K). The use of structural entropy for enhanced thermopower could lead to new engineering approaches for thermoelectric materials with high zT and new green applications for thermoelectrics.

  7. Modified silicon-germanium alloys with improved performance. [thermoelectric material

    NASA Technical Reports Server (NTRS)

    Pisharody, R. K.; Garvey, L. P.

    1978-01-01

    This paper discusses the results of a program on the modification of silicon-germanium alloys by means of small extraneous material additions in order to improve their figures-of-merit. A review of the properties that constitute the figure-of-merit indicates that it is the relatively high thermal conductivity of silicon-germanium alloys that is responsible for their low values of figure-of-merit. The intent of the effort discussed in this paper is therefore the reduction of the thermal conductivity of silicon-germanium alloys by minor alloy additions and/or changes in the basic structure of the material. Because Group III and V elements are compatible with silicon and germanium, the present effort in modifying silicon-germanium alloys has concentrated on additions of gallium phosphide. A significant reduction in thermal conductivity, approximately 40 to 50 percent, has been demonstrated while the electrical properties are only slightly affected as a result. The figure-of-merit of the resultant material is enhanced over that of silicon-germanium alloys and when fully optimized is potentially better than that of any other presently available thermoelectric material.

  8. High-performance thermoelectric nanocomposites from nanocrystal building blocks

    NASA Astrophysics Data System (ADS)

    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

    2016-03-01

    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.

  9. 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.

  10. Enhanced thermoelectric figure of merit in strained Tl-doped Bi{sub 2}Se{sub 3}

    SciTech Connect

    Saeed, Y.; Singh, N.; Schwingenschlögl, U.

    2014-07-21

    We explain recent experimental findings on Tl-doped Bi{sub 2}Se{sub 3} by determining the electronic and transport properties by first-principles calculations and semi-classical Boltzmann theory. Though Tl-doping introduces a momentum-dependent spin-orbit splitting, the effective mass of the carriers is essentially not modified, while the band gap is reduced. Tl is found to be exceptional in this respect as other dopants modify the dispersion, which compromises thermoelectricity. Moreover, we demonstrate that only after Tl-doping strain becomes an efficient tool for enhancing the thermoelectric performance. A high figure of merit of 0.86 is obtained for strong p-doping (7 × 10{sup 20} cm{sup −3}, maximal power factor) at 500 K under 2% tensile strain.

  11. 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.

  12. 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

    2015-01-01

    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

  13. 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

    2015-01-01

    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.

  14. 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

  15. Enhancement of thermoelectric performance in n-type PbTe1-ySey by doping Cr and tuning Te:Se ratio

    SciTech Connect

    Chere, Eyob K.; Zhang, Qian; McEnaney, Kenneth; Yao, Mengliang; Cao, Feng; Sun, Jingying; Chen, Shuo; Opeil, Cyril; Chen, Gang; Ren, Zhifeng

    2015-04-01

    Lead telluride and its alloys have been extensively studied for medium temperature thermoelectric applications due to decent figure-of-merit (ZT) at temperature close to 900 K. However, little emphasis has been given to improve the ZT near room temperature. In this investigation, we report a systematic study of Cr doping in PbTe1-ySey with y=0, 0.25, 0.5, 0.75, 0.85, and 1. We found the peak ZT temperature increased with increasing concentration of Se. The highest ZT of ~0.6 at room temperature in Te-rich Cr0.015Pb0.985Te0.75Se0.25 was obtained due to a lowered thermal conductivity and enhanced power factor resulted from high Seebeck coefficient of about -220 µV K-1 and high Hall mobility ~1120 cm2 V-1 s-1 at room temperature. A room temperature ZT of ~0.5 and peak ZT of ~1 at about 573–673 K is shown by Se-rich sample Cr0.01Pb0.99Te0.25Se0.75. This improvement of the room temperature ZTimproved the average ZT over a wide temperature range and could potentially lead to a single leg efficiency of thermoelectric conversion for Te-rich Cr0.015Pb0.985Te0.75Se0.25 up to ~11% and Se-rich Cr0.01Pb0.99Te0.25Se0.75 up to ~13% with cold side and hot side temperature at 300 K and 873 K, respectively, if matched with appropriate p-type legs.

  16. 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.

  17. Nanograin-enhanced in-plane thermoelectric figure of merit in n-type SiGe thin films

    NASA Astrophysics Data System (ADS)

    Lu, Jianbiao; Guo, Ruiqiang; Huang, Baoling

    2016-04-01

    SiGe thin films are desirable candidates for many thermoelectric applications because of their low cost, low toxicity, and high compatibility with microelectronics fabrications. Currently, their applications are limited by their very poor thermoelectric performance. In this study, phosphorus-doped SiGe thin films with improved thermoelectric properties were grown using low pressure chemical vapor deposition, and the effects of different annealing treatments, doping concentration, composition, and temperature on their thermoelectric properties were explored. It is found that the segregation of phosphorus dopants plays an important role in grain growth and thermoelectric transport properties. The improved thermoelectric performance is mainly attributed to the significantly reduced in-plane thermal conductivity by the naturally formed nanograins. By adjusting the growth conditions, doping and post treatments, an in-plane ZT ˜ 0.16 at 300 K was obtained for the optimized n-type samples, which is even ˜50% higher than the record of bulk SiGe.

  18. Semimetal/Semiconductor Nanocomposites for Thermoelectrics

    SciTech Connect

    Lu, Hong; Burke, Peter G.; Gossard, Arthur C.; Zeng, Gehong; Ramu, Ashok T.; Bahk, Je-Hyeong; Bowers, John E.

    2011-04-15

    In this work, we present research on semimetal-semiconductor nanocomposites grown by molecular beam epitaxy (MBE) for thermoelectric applications. We study several different III-V semiconductors embedded with semimetallic rare earth-group V (RE-V) compounds, but focus is given here to ErSb:InxGa1-xSb as a promising p-type thermoelectric material. Nano­structures of RE-V compounds are formed and embedded within the III-V semiconductor matrix. By codoping the nanocomposites with the appropriate dopants, both n-type and p-type materials have been made for thermoelectric applications. The thermoelectric properties have been engineered for enhanced thermoelectric device performance. Segmented thermoelectric power generator modules using 50 μm thick Er-containing nanocomposites have been fabricated and measured. Research on different rare earth elements for thermoelectrics is discussed.

  19. Thermoelectric power factor performance of Bi85Sb15/graphene composite

    NASA Astrophysics Data System (ADS)

    El-Asfoury, Mohamed S.; Nasr, Mohamed N. A.; Nakamura, Koichi; Abdel-Moneim, Ahmed

    2016-04-01

    Composite materials based on Bi85Sb15 with commercial graphene (Gr) nanoparticles have been synthesized by mechanical alloying and hot isostatic pressing. The effect of different amount of Gr nanoparticles (x = 0.02, 0.04, 0.06, and 0.08 wt %) on the thermoelectric properties of (Bi85Sb15)1- x Gr x composite was investigated. X-ray diffraction and scanning electron microscopy were carried out for the structure characterization of the composites. Transport properties, including electrical resistivity, Seebeck coefficient, and calculated power factor, were investigated and their variations were discussed with regard to microstructures in the temperature range of 173-373 K. Resistivity significantly declines in the sample with x = 0.04 wt % Gr, and the enhancement was 7% at 230 K and reached about 7.6% at room temperature. With 0.08 wt % Gr, a high absolute value of the Seebeck coefficient was observed. The power factor reaches its maximum of 3.7 × 10-3 W·m-1·K-2 with x = 0.08 wt % at 173 K. The results reflect that this synthesis process can be a powerful method of obtaining homogeneous Bi-Sb thermoelectric composite materials rapidly and at low cost. In addition, the demand for uniform coherent composites was significant because of their high-performance transport properties.

  20. Investigation of the Performance of Thermoelectric Energy Harvesters Under Real Flight Conditions

    NASA Astrophysics Data System (ADS)

    Elefsiniotis, A.; Samson, D.; Becker, Th.; Schmid, U.

    2013-07-01

    Energy-autonomous wireless sensor nodes (WSNs) in aircraft, acting as health monitoring systems (HMS), have the potential to reduce aircraft maintenance costs. Thermoelectric energy harvesting is a solution for self-powered systems, since it captures enough energy to power up a WSN. The energy harvesting device used in this work consists of a thermoelectric generator (TEG) attached to the inner part of the fuselage and to a thermal storage device, in order to artificially enhance the temperature difference between the bottom and the top surface of the TEG during take-off and landing. In this study, the results of 28 flight tests during a 6-month flight campaign of two identical energy harvesting devices are presented. The results are clustered into two different classes, each having its own characteristics. The two classes comprise typical, similar to standard European short/mid-range flights, as well as atypical flight profiles, where specific flight tests have been performed. In addition, for each class, different parameters such as flight altitudes, flight duration, and temperature profiles are investigated. Moreover, a detailed comparison between a typical and an atypical flight profile is given. In general, for a typical flight profile, the experimental results are in good agreement with simulations predicting the energy output. The average energy output is sufficient to power up a wireless sensor.

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

    SciTech Connect

    Lin, Jianping; Ma, Lingzhi; Yang, Baifeng; Fei, Youjian; Lei, Lei; Qiao, Guanjun; Ren, Yang

    2013-04-22

    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 excess Zn atoms, and then reduce thermoelectric performance.

  2. 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.

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

    PubMed

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

    2011-05-01

    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.

  4. Cooling performance of solar cell-driven, thermoelectric cooling prototype headgear

    SciTech Connect

    Hara, T.; Obora, H.; Sato, S.

    1998-07-01

    Cooling performance of solar cell driven, thermoelectric cooling prototype headgear was examined experimentally. Three types of prototype headgear were made and examined. They were cooled by thermoelectric elements and driven by solar cells. The authors are always able to be cooled anytime and anywhere inside the house in hot season. However, they were not able to be cooled when they worked outside the house. Especially, a personal air-conditioning system is required for the people working outside. Some cooling caps with an electric fan driven by solar cells can be often seen now. However, the fan only blows hot air to the face. They cannot cool down the face below the ambient temperature. The authors tried to cool down the face to the lower temperature below the ambient by a refrigeration system. A thermoelectric element was set at the front of a headgear such as baseball cap or straw hat to cool a forehead. Some pieces of solar cells were mounted on the top and the brim of the headgear to work the thermoelectric element. Hot side of thermoelectric element was cooled by a plate fin an electric fan. The electric fan was also driven by a solar cell. Two types of baseball caps with solar cells and a thermoelectric element and a type of straw hat with them were made and tested. Solar cells were connected to optimize the electric power for the thermoelectric element. An electric fan and its power input were selected to cool maximum the thermoelectric element. Cooling performance and thermal comfort of the headgear were examined by testers in case of sitting, walking and bicycling. The temperature difference between ambient and cooling temperature was required only about 4 degree Celsius. Required power by solar cells was up to about 1.5 watt for a personal cooling.

  5. High thermoelectric performance of p-type SnTe via a synergistic band engineering and nanostructuring approach.

    PubMed

    Tan, Gangjian; Zhao, Li-Dong; Shi, Fengyuan; Doak, Jeff W; Lo, Shih-Han; Sun, Hui; Wolverton, Chris; Dravid, Vinayak P; Uher, Ctirad; Kanatzidis, Mercouri G

    2014-05-14

    SnTe is a potentially attractive thermoelectric because it is the lead-free rock-salt analogue of PbTe. However, SnTe is a poor thermoelectric material because of its high hole concentration arising from inherent Sn vacancies in the lattice and its very high electrical and thermal conductivity. In this study, we demonstrate that SnTe-based materials can be controlled to become excellent thermoelectrics for power generation via the successful application of several key concepts that obviate the well-known disadvantages of SnTe. First, we show that Sn self-compensation can effectively reduce the Sn vacancies and decrease the hole carrier density. For example, a 3 mol % self-compensation of Sn results in a 50% improvement in the figure of merit ZT. In addition, we reveal that Cd, nominally isoelectronic with Sn, favorably impacts the electronic band structure by (a) diminishing the energy separation between the light-hole and heavy-hole valence bands in the material, leading to an enhanced Seebeck coefficient, and (b) enlarging the energy band gap. Thus, alloying with Cd atoms enables a form of valence band engineering that improves the high-temperature thermoelectric performance, where p-type samples of SnCd(0.03)Te exhibit ZT values of ~0.96 at 823 K, a 60% improvement over the Cd-free sample. Finally, we introduce endotaxial CdS or ZnS nanoscale precipitates that reduce the lattice thermal conductivity of SnCd(0.03)Te with no effect on the power factor. We report that SnCd(0.03)Te that are endotaxially nanostructured with CdS and ZnS have a maximum ZTs of ~1.3 and ~1.1 at 873 K, respectively. Therefore, SnTe-based materials could be ideal alternatives for p-type lead chalcogenides for high temperature thermoelectric power generation.

  6. High thermoelectric performance of p-type SnTe via a synergistic band engineering and nanostructuring approach.

    PubMed

    Tan, Gangjian; Zhao, Li-Dong; Shi, Fengyuan; Doak, Jeff W; Lo, Shih-Han; Sun, Hui; Wolverton, Chris; Dravid, Vinayak P; Uher, Ctirad; Kanatzidis, Mercouri G

    2014-05-14

    SnTe is a potentially attractive thermoelectric because it is the lead-free rock-salt analogue of PbTe. However, SnTe is a poor thermoelectric material because of its high hole concentration arising from inherent Sn vacancies in the lattice and its very high electrical and thermal conductivity. In this study, we demonstrate that SnTe-based materials can be controlled to become excellent thermoelectrics for power generation via the successful application of several key concepts that obviate the well-known disadvantages of SnTe. First, we show that Sn self-compensation can effectively reduce the Sn vacancies and decrease the hole carrier density. For example, a 3 mol % self-compensation of Sn results in a 50% improvement in the figure of merit ZT. In addition, we reveal that Cd, nominally isoelectronic with Sn, favorably impacts the electronic band structure by (a) diminishing the energy separation between the light-hole and heavy-hole valence bands in the material, leading to an enhanced Seebeck coefficient, and (b) enlarging the energy band gap. Thus, alloying with Cd atoms enables a form of valence band engineering that improves the high-temperature thermoelectric performance, where p-type samples of SnCd(0.03)Te exhibit ZT values of ~0.96 at 823 K, a 60% improvement over the Cd-free sample. Finally, we introduce endotaxial CdS or ZnS nanoscale precipitates that reduce the lattice thermal conductivity of SnCd(0.03)Te with no effect on the power factor. We report that SnCd(0.03)Te that are endotaxially nanostructured with CdS and ZnS have a maximum ZTs of ~1.3 and ~1.1 at 873 K, respectively. Therefore, SnTe-based materials could be ideal alternatives for p-type lead chalcogenides for high temperature thermoelectric power generation. PMID:24785377

  7. 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

  8. Improved Thermoelectric Performances of SrTiO3 Ceramic Doped with Nb by Surface Modification of Nanosized Titania.

    PubMed

    Li, Enzhu; Wang, Ning; He, Hongcai; Chen, Haijun

    2016-12-01

    Nb-doped SrTiO3 ceramics doped with the surface modification of nanosized titania was prepared via liquid phase deposition approach and subsequent sintered in an Ar atmosphere. The surface modification of nanosized titania significantly improved the ratio of the electrical conductivity to thermal conductivity of SrTiO3 ceramic doped with Nb, and has little impact on the Seebeck coefficient, thus obviously improving the dimensionless thermoelectric figure of merit (ZT value). The surface modification of nanosized titania is a much better method to lower the thermal conductivity and to enhance the electrical conductivity than the mechanical mixing process of nanosized titania. The highest ZT value of 0.33 at 900 K was obtained. The reason for the improved thermoelectric performances by the surface modification of nano-sized titania was preliminary investigated.

  9. Tuning the carrier concentration to improve the thermoelectric performance of CuInTe{sub 2} compound

    SciTech Connect

    Wei, J.; Liu, H. J. Cheng, L.; Zhang, J.; Liang, J. H.; Jiang, P. H.; Fan, D. D.; Shi, J.

    2015-10-15

    The electronic and transport properties of CuInTe{sub 2} chalcopyrite are investigated using density functional calculations combined with Boltzmann theory. The band gap predicted from hybrid functional is 0.92 eV, which agrees well with experimental data and leads to relatively larger Seebeck coefficient compared with those of narrow-gap thermoelectric materials. By fine tuning the carrier concentration, the electrical conductivity and power factor of the system can be significantly optimized. Together with the inherent low thermal conductivity, the ZT values of CuInTe{sub 2} compound can be enhanced to as high as 1.72 at 850 K, which is obviously larger than those measured experimentally and suggests there is still room to improve the thermoelectric performance of this chalcopyrite compound.

  10. Performance Tests of Skutterudites and Segmented Thermoelectric Converters

    NASA Astrophysics Data System (ADS)

    El-Genk, Mohamed S.; Saber, Hamed H.; Caillat, Thierry

    2004-02-01

    This paper presents results of three performance tests of Skutterudites and Segmented Thermoelectric (STE) unicouples performed at average hot and cold shoe temperatures of ~ 973 K and 300 K, respectively, to verify theoretical predictions. The first two tests (MAR-03 and JUN-03) involved non-segmented Skutterudites unicouples of slightly different dimension but same materials for the n- (CoSb3) and p- (CeFe3.5Co0.5Sb12) legs. The test duration is 450 hours for MAR-03 and 1200 hours for JUN-03. The third test (JUL-03) is for a Skutterudites/Segmented (STE) unicouple, in which the p-leg has two segments of CeFe3.5Co0.5Sb12 and Bi0.4Sb1.6Te3 and the n-leg has two segments of CoSb3 and Bi2Te2.95Se0.05. The segments in the n- and p-legs have different lengths and cross-sectional areas. The JUL-03 test duration is 645 hours. All tested unicouples are fabricated at JPL and assembled and tested in the vacuum facility at the University of New Mexico in argon at ~ 0.051 to 0.068 MPa to suppress the sublimation of antimony from the legs near the hot shoe. Detailed measurements of the open circuit voltage, voltage across the n- and p-legs, the voltage-current (V-I) characteristics, and the hot and cold shoe temperatures are performed in all tests. In JUL-03, additional measurements of the interfacial temperatures and the voltage across the segments in the n- and p-legs are obtained as functions of test duration. Estimates of beginning-of-life (BOL) conversion efficiencies of 10.7% for Shutterudites and 13.5% for STE unicouples are within 10% of theoretical predictions assuming zero side heat losses and zero contact resistances. Estimates of these losses in the tests are 2.3 W in MAR-03 to 9.3 W in JUL-03, thus actual efficiencies in the tests are ~ 40-50% lower. Because cross sectional areas of the legs of JUL-03 are much larger than of both MAR-03 and JUN-03, the measured BOL peak electrical power per unicouple is 1.295 We versus 0.671 We for the latter.

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

    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.

  12. 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

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

    SciTech Connect

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

    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 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.

  14. Convergence of valence bands for high thermoelectric performance for p-type InN

    NASA Astrophysics Data System (ADS)

    Li, Hai-Zhu; Li, Ruo-Ping; Liu, Jun-Hui; Huang, Ming-Ju

    2015-12-01

    Band engineering to converge the bands to achieve high valley degeneracy is one of effective approaches for designing ideal thermoelectric materials. Convergence of many valleys in the valence band may lead to a high Seebeck coefficient, and induce promising thermoelectric performance of p-type InN. In the current work, we have systematically investigated the electronic structure and thermoelectric performance of wurtzite InN by using the density functional theory combined with semiclassical Boltzmann transport theory. Form the results, it can be found that intrinsic InN has a large Seebeck coefficient (254 μV/K) and the largest value of ZeT is 0.77. The transport properties of p-type InN are better than that of n-type one at the optimum carrier concentration, which mainly due to the large Seebeck coefficient for p-type InN, although the electrical conductivity of n-type InN is larger than that of p-type one. We found that the larger Seebeck coefficient for p-type InN may originate from the large valley degeneracy in the valence band. Moreover, the low minimum lattice thermal conductivity for InN is one key factor to become a good thermoelectric material. Therefore, p-type InN could be a potential material for further applications in the thermoelectric area.

  15. Thermoelectric performance of restacked MoS2 nanosheets thin-film.

    PubMed

    Wang, Tongzhou; Liu, Congcong; Xu, Jingkun; Zhu, Zhengyou; Liu, Endou; Hu, Yongjing; Li, Changcun; Jiang, Fengxing

    2016-07-15

    MoS2 has been predicted to be an excellent thermoelectric material due to its large intrinsic band gap and high carrier mobility. In this work, we exfoliated bulk MoS2 by the assistance of lithium intercalation and fabricated the restacked MoS2 thin-film using a simple filtration technique. These MoS2 thin-films with different thickness showed different thermoelectric performance. It was found that with the increase of thickness, carrier concentration, electrical conductivity and Seebeck coefficient all showed an increasing trend. In particular, the maximum Seebeck coefficient was able to reach 93.5 μV K(-1). This high thermopower indicates that MoS2 will have ideal thermoelectric performance in the future through optimizing its structure. The highest figure of merit (ZT = 0.01) is calculated in this experiment.

  16. Thermoelectric performance of restacked MoS2 nanosheets thin-film

    NASA Astrophysics Data System (ADS)

    Wang, Tongzhou; Liu, Congcong; Xu, Jingkun; Zhu, Zhengyou; Liu, Endou; Hu, Yongjing; Li, Changcun; Jiang, Fengxing

    2016-07-01

    MoS2 has been predicted to be an excellent thermoelectric material due to its large intrinsic band gap and high carrier mobility. In this work, we exfoliated bulk MoS2 by the assistance of lithium intercalation and fabricated the restacked MoS2 thin-film using a simple filtration technique. These MoS2 thin-films with different thickness showed different thermoelectric performance. It was found that with the increase of thickness, carrier concentration, electrical conductivity and Seebeck coefficient all showed an increasing trend. In particular, the maximum Seebeck coefficient was able to reach 93.5 μV K‑1. This high thermopower indicates that MoS2 will have ideal thermoelectric performance in the future through optimizing its structure. The highest figure of merit (ZT = 0.01) is calculated in this experiment.

  17. Optimization of Filler Elements in CoSb3-Based Skutterudites for High-Performance n-Type Thermoelectric Materials

    NASA Astrophysics Data System (ADS)

    Matsubara, M.; Asahi, R.

    2016-03-01

    To develop high-performance n-type thermoelectric materials, the optimum synthesis process and effective filler elements for partially filled skutterudites were investigated. For the composition R0.4B0.3Co4- y Fe y Sb12 (basic elemental group R0.4 = Ba0.1Yb0.2Al0.1) with filling factor x = 0.7, the ratio and combination of filler elements in B0.3 and Fe content y were optimized. First, from the viewpoint of ionic valence and ionic radius, we examined the combination of various filler elements and selected a combination of Al and Gd as filler elements in B0.3; these filler elements effectively reduced the thermal conductivity and enhanced the power factor of the skutterudites, respectively. However, these elements easily precipitated because of their low solubility, and the improved thermoelectric properties of skutterudites induced by Al and Gd were insufficient. The results revealed that the thermoelectric properties of the partially filled skutterudites were improved when such elemental precipitation was suppressed by substitution of the Al and Gd atoms with other elements with greater solubility limits. Furthermore, to compensate for the excess number of carriers introduced by filler addition, a portion of the Co sites were substituted with Fe, which resulted in an improved figure of merit ( ZT) value.

  18. 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.

  19. Fabrication of Advanced Thermoelectric Materials by Hierarchical Nanovoid Generation

    NASA Technical Reports Server (NTRS)

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

  20. Peierls distortion as a route to high thermoelectric performance in In(4)Se(3-delta) crystals.

    PubMed

    Rhyee, Jong-Soo; Lee, Kyu Hyoung; Lee, Sang Mock; Cho, Eunseog; Kim, Sang Il; Lee, Eunsung; Kwon, Yong Seung; Shim, Ji Hoon; Kotliar, Gabriel

    2009-06-18

    Thermoelectric energy harvesting-the transformation of waste heat into useful electricity-is of great interest for energy sustainability. The main obstacle is the low thermoelectric efficiency of materials for converting heat to electricity, quantified by the thermoelectric figure of merit, ZT. The best available n-type materials for use in mid-temperature (500-900 K) thermoelectric generators have a relatively low ZT of 1 or less, and so there is much interest in finding avenues for increasing this figure of merit. Here we report a binary crystalline n-type material, In(4)Se(3-delta), which achieves the ZT value of 1.48 at 705 K-very high for a bulk material. Using high-resolution transmission electron microscopy, electron diffraction, and first-principles calculations, we demonstrate that this material supports a charge density wave instability which is responsible for the large anisotropy observed in the electric and thermal transport. The high ZT value is the result of the high Seebeck coefficient and the low thermal conductivity in the plane of the charge density wave. Our results suggest a new direction in the search for high-performance thermoelectric materials, exploiting intrinsic nanostructural bulk properties induced by charge density waves.

  1. Narrow band gap and enhanced thermoelectricity in FeSb2.

    PubMed

    Sun, Peijie; Oeschler, Niels; Johnsen, Simon; Iversen, Bo B; Steglich, Frank

    2010-01-28

    FeSb(2) was recently identified as a narrow-gap semiconductor with indications of strong electron-electron correlations. In this manuscript, we report on systematic thermoelectric investigation of a number of FeSb(2) single crystals with varying carrier concentrations, together with two isoelectronically substituted FeSb(2-x)As(x) samples (x = 0.01 and 0.03) and two reference compounds FeAs(2) and RuSb(2). Typical behaviour associated with narrow bands and narrow gaps is only confirmed for the FeSb(2) and the FeSb(2-x)As(x) samples. The maximum absolute thermopower of FeSb(2) spans from 10 to 45 mV/K at around 10 K, greatly exceeding that of both FeAs(2) and RuSb(2). The relation between the carrier concentration and the maximum thermopower value is in approximate agreement with theoretical predictions of the electron-diffusion contribution which, however, requires an enhancement factor larger than 30. The isoelectronic substitution leads to a reduction of the thermal conductivity, but the charge-carrier mobility is also largely reduced due to doping-induced crystallographic defects or impurities. In combination with the high charge-carrier mobility and the enhanced thermoelectricity, FeSb(2) represents a promising candidate for thermoelectric cooling applications at cryogenic temperatures. PMID:20066185

  2. Thermoelectric performance of functionalized Sc2C MXenes

    NASA Astrophysics Data System (ADS)

    Kumar, S.; Schwingenschlögl, U.

    2016-07-01

    Functionalization of the MXene Sc2C , which has the rare property to realize semiconducting states for various functionalizations including O, F, and OH, is studied with respect to the electronic and thermal behavior. The lowest lattice thermal conductivity is obtained for OH functionalization and an additional 30% decrease can be achieved by confining the phonon mean free path to 100 nm. Despite a relatively low Seebeck coefficient, Sc2C (OH) 2 is a candidate for intermediate-temperature thermoelectric applications due to compensation by a high electrical conductivity and very low lattice thermal conductivity.

  3. Thermoelectric performance of various benzo-difuran wires

    SciTech Connect

    Péterfalvi, Csaba G.; Grace, Iain; Manrique, Dávid Zs.; Lambert, Colin J.

    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.

  4. 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.

  5. Thermoelectric efficiency of molecular junctions

    NASA Astrophysics Data System (ADS)

    Perroni, C. A.; Ninno, D.; Cataudella, V.

    2016-09-01

    Focus of the review is on experimental set-ups and theoretical proposals aimed to enhance thermoelectric performances of molecular junctions. In addition to charge conductance, the thermoelectric parameter commonly measured in these systems is the thermopower, which is typically rather low. We review recent experimental outcomes relative to several junction configurations used to optimize the thermopower. On the other hand, theoretical calculations provide estimations of all the thermoelectric parameters in the linear and non-linear regime, in particular of the thermoelectric figure of merit and efficiency, completing our knowledge of molecular thermoelectricity. For this reason, the review will mainly focus on theoretical studies analyzing the role of not only electronic, but also of the vibrational degrees of freedom. Theoretical results about thermoelectric phenomena in the coherent regime are reviewed focusing on interference effects which play a significant role in enhancing the figure of merit. Moreover, we review theoretical studies including the effects of molecular many-body interactions, such as electron–vibration couplings, which typically tend to reduce the efficiency. Since a fine tuning of many parameters and coupling strengths is required to optimize the thermoelectric conversion in molecular junctions, new theoretically proposed set-ups are discussed in the conclusions.

  6. Thermoelectric efficiency of molecular junctions.

    PubMed

    Perroni, C A; Ninno, D; Cataudella, V

    2016-09-21

    Focus of the review is on experimental set-ups and theoretical proposals aimed to enhance thermoelectric performances of molecular junctions. In addition to charge conductance, the thermoelectric parameter commonly measured in these systems is the thermopower, which is typically rather low. We review recent experimental outcomes relative to several junction configurations used to optimize the thermopower. On the other hand, theoretical calculations provide estimations of all the thermoelectric parameters in the linear and non-linear regime, in particular of the thermoelectric figure of merit and efficiency, completing our knowledge of molecular thermoelectricity. For this reason, the review will mainly focus on theoretical studies analyzing the role of not only electronic, but also of the vibrational degrees of freedom. Theoretical results about thermoelectric phenomena in the coherent regime are reviewed focusing on interference effects which play a significant role in enhancing the figure of merit. Moreover, we review theoretical studies including the effects of molecular many-body interactions, such as electron-vibration couplings, which typically tend to reduce the efficiency. Since a fine tuning of many parameters and coupling strengths is required to optimize the thermoelectric conversion in molecular junctions, new theoretically proposed set-ups are discussed in the conclusions. PMID:27420149

  7. Thermoelectric efficiency of molecular junctions

    NASA Astrophysics Data System (ADS)

    Perroni, C. A.; Ninno, D.; Cataudella, V.

    2016-09-01

    Focus of the review is on experimental set-ups and theoretical proposals aimed to enhance thermoelectric performances of molecular junctions. In addition to charge conductance, the thermoelectric parameter commonly measured in these systems is the thermopower, which is typically rather low. We review recent experimental outcomes relative to several junction configurations used to optimize the thermopower. On the other hand, theoretical calculations provide estimations of all the thermoelectric parameters in the linear and non-linear regime, in particular of the thermoelectric figure of merit and efficiency, completing our knowledge of molecular thermoelectricity. For this reason, the review will mainly focus on theoretical studies analyzing the role of not only electronic, but also of the vibrational degrees of freedom. Theoretical results about thermoelectric phenomena in the coherent regime are reviewed focusing on interference effects which play a significant role in enhancing the figure of merit. Moreover, we review theoretical studies including the effects of molecular many-body interactions, such as electron-vibration couplings, which typically tend to reduce the efficiency. Since a fine tuning of many parameters and coupling strengths is required to optimize the thermoelectric conversion in molecular junctions, new theoretically proposed set-ups are discussed in the conclusions.

  8. Thermoelectric efficiency of molecular junctions.

    PubMed

    Perroni, C A; Ninno, D; Cataudella, V

    2016-09-21

    Focus of the review is on experimental set-ups and theoretical proposals aimed to enhance thermoelectric performances of molecular junctions. In addition to charge conductance, the thermoelectric parameter commonly measured in these systems is the thermopower, which is typically rather low. We review recent experimental outcomes relative to several junction configurations used to optimize the thermopower. On the other hand, theoretical calculations provide estimations of all the thermoelectric parameters in the linear and non-linear regime, in particular of the thermoelectric figure of merit and efficiency, completing our knowledge of molecular thermoelectricity. For this reason, the review will mainly focus on theoretical studies analyzing the role of not only electronic, but also of the vibrational degrees of freedom. Theoretical results about thermoelectric phenomena in the coherent regime are reviewed focusing on interference effects which play a significant role in enhancing the figure of merit. Moreover, we review theoretical studies including the effects of molecular many-body interactions, such as electron-vibration couplings, which typically tend to reduce the efficiency. Since a fine tuning of many parameters and coupling strengths is required to optimize the thermoelectric conversion in molecular junctions, new theoretically proposed set-ups are discussed in the conclusions.

  9. Thermoelectric Performance for SnSe Hot-Pressed at Different Temperature

    NASA Astrophysics Data System (ADS)

    Li, D.; Li, J. C.; Qin, X. Y.; Zhang, J.; Song, C. J.; Wang, L.; Xin, H. X.

    2016-09-01

    Herein, nanoparticles SnSe are prepared by fusion method together with ball-milling technique and the effect of hot-pressing temperatures on the thermoelectric properties of the dense materials is explored. Due to the optimization of carrier concentration, the peak figure of merit (ZT) value of the compacted material reaches 0.73 for SnSe sample hot-pressed at 400°C and 450°C. The present investigation indicates that the thermoelectric performance of the SnSe compound can be significantly improved by sintering with suitable temperature.

  10. Flexible nanocrystal-coated glass fibers for high-performance thermoelectric energy harvesting.

    PubMed

    Liang, Daxin; Yang, Haoran; Finefrock, Scott W; Wu, Yue

    2012-04-11

    Recent efforts on the development of nanostructured thermoelectric materials from nanowires (Boukai, A. I.; et al. Nature 2008, 451, (7175), 168-171; Hochbaum, A. I.; et al. Nature 2008, 451, (7175), 163-167) and nanocrystals (Kim, W.; et al. Phys. Rev. Lett. 2006, 96, (4), 045901; Poudel, B.; et al. Science 2008, 320, (5876), 634-638; Scheele, M.; et al. Adv. Funct. Mater. 2009, 19, (21), 3476-3483; Wang, R. Y.; et al. Nano Lett. 2008, 8, (8), 2283-2288) show the comparable or superior performance to the bulk crystals possessing the same chemical compositions because of the dramatically reduced thermal conductivity due to phonon scattering at nanoscale surface and interface. Up to date, the majority of the thermoelectric devices made from these inorganic nanostructures are fabricated into rigid configuration. The explorations of truly flexible composite-based flexible thermoelectric devices (See, K. C.; et al. Nano Lett. 2010, 10, (11), 4664-4667) have thus far achieved much less progress, which in principle could significantly benefit the conversion of waste heat into electricity or the solid-state cooling by applying the devices to any kind of objects with any kind of shapes. Here we report an example using a scalable solution-phase deposition method to coat thermoelectric nanocrystals onto the surface of flexible glass fibers. Our investigation of the thermoelectric properties yields high performance comparable to the state of the art from the bulk crystals and proof-of-concept demonstration also suggests the potential of wrapping the thermoelectric fibers on the industrial pipes to improve the energy efficiency.

  11. 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.

  12. Spin caloritronics with superconductors: Enhanced thermoelectric effects, generalized Onsager response-matrix, and thermal spin currents

    NASA Astrophysics Data System (ADS)

    Linder, Jacob; Bathen, Marianne Etzelmüller

    2016-06-01

    It has recently been proposed and experimentally demonstrated that it is possible to generate large thermoelectric effects in ferromagnet/superconductor structures due to a spin-dependent particle-hole asymmetry. Here, we show theoretically that quasiparticle tunneling between two spin-split superconductors enhances the thermoelectric response manyfold compared to when only one such superconductor is used, generating Seebeck coefficients (S >1 mV/K) and figures of merit (Z T ≃40 ) far exceeding the best bulk thermoelectric materials, and it also becomes more resilient toward inelastic-scattering processes. We present a generalized Onsager response-matrix that takes into account spin-dependent voltage and temperature gradients. Moreover, we show that thermally induced spin currents created in such junctions, even in the absence of a polarized tunneling barrier, also become largest in the case in which spin-dependent particle-hole asymmetry exists on both sides of the barrier. We determine how these thermal spin-currents can be tuned both in magnitude and sign by several parameters, including the external field, the temperature, and the superconducting phase difference.

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

    SciTech Connect

    Gaultois, Michael W.; Sparks, Taylor D.

    2014-03-17

    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 from 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.

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

    DOEpatents

    Venkatasubramanian, Rama; Cook, Bruce Allen; Levin, Evgenii M.; Harringa, Joel Lee

    2016-09-06

    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 of the p-type thermoelectric material or the n-type thermoelectric material.

  15. 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

  16. Methods of thermoelectric enhancement in silicon-germanium alloy type I clathrates and in nanostructured lead chalcogenides

    NASA Astrophysics Data System (ADS)

    Martin, Joshua

    The rapid increase in thermoelectric (TE) materials R&D is a consequence of the growing need to increase energy efficiency and independence through waste heat recovery. TE materials enable the direct solid-state conversion of heat into electricity, with little maintenance, noise, or cost. In addition, these compact devices can be incorporated into existing technologies to increase the overall operating efficiency. High efficiency TE materials would enable the practical solid-state conversion of thermal to electrical energy. Optimizing the interdependent physical parameters to achieve acceptable efficiencies requires materials exhibiting a unique combination of properties. This research reports two methods of thermoelectric enhancement: lattice strain effects in silicon-germanium alloy type I clathrates and the nanostructured enhancement of lead chalcogenides. The synthesis and chemical, structural, and transport properties characterization of Ba8Ga16SixGe30-x type I clathrates with similar Ga-to-group IV element ratios but with increasing Si substitution (4 < x < 14) is reported. Substitution of Si within the Ga-Ge lattice framework of the type I clathrate Ba8Ga16Ge30 results in thermoelectric performance enhancement. The unique dependences of carrier concentration, electrical resistivity, Seebeck coefficient, and carrier effective mass on Si substitution level, may imply a modified band structure with Si substitution. These materials were then further optimized by adjusting the Ga-to-group IV element ratios. Recent progress in a number of higher efficiency TE materials can be attributed to nanoscale enhancement. Many of these materials demonstrate increased Seebeck coefficient and decreased thermal conductivity due to the phenomenological properties of nanometer length scales. To satisfy the demands of bulk industrial applications requires additional synthesis techniques to incorporate nanostructure directly within a bulk matrix. This research investigates, for

  17. Enhanced Thermoelectric Properties of La-Doped ZrNiSn Half-Heusler Compound

    NASA Astrophysics Data System (ADS)

    Akram, Rizwan; Zhang, Qiang; Yang, Dongwang; Zheng, Yun; Yan, Yonggao; Su, Xianli; Tang, Xinfeng

    2015-10-01

    The effect of La doping on ZrNiSn half-Heusler (HH) compound has been studied to explore the composition variation and structural modifications for improvement of its thermoelectric performance. A series of La x Zr1- x NiSn ( x = 0, 0.005, 0.01, 0.015, 0.02, 0.03) alloys were prepared by induction melting combined with plasma-activated sintering. Structural analysis using x-ray diffraction (XRD), scanning electron microscopy (SEM), and transmission electron microscopy (TEM) confirmed the resulting material to be a composite of HH, NiZr, and La3Sn4-type phases. The volume fraction for the phases other than HH ranged from 1.5% to 25% with increasing La content, as estimated by Rietveld analysis. The solubility of La in ZrNiSn is estimated to be 1.5%. Point defects may play a significant role in carrier and phonon transport. Interestingly, the thermoelectric transport properties exhibited a considerable increase in electrical conductivity σ with La doping and a significant drop in thermal conductivity κ, leading to a thermoelectric figure of merit ( ZT) of 0.53 at 923 K, representing an improvement of about 37% compared with the undoped sample.

  18. Enhanced Thermoelectric Power in Graphene: Violation of the Mott Relation by Inelastic Scattering.

    PubMed

    Ghahari, Fereshte; Xie, Hong-Yi; Taniguchi, Takashi; Watanabe, Kenji; Foster, Matthew S; Kim, Philip

    2016-04-01

    We report the enhancement of the thermoelectric power (TEP) in graphene with extremely low disorder. At high temperature we observe that the TEP is substantially larger than the prediction of the Mott relation, approaching to the hydrodynamic limit due to strong inelastic scattering among the charge carriers. However, closer to room temperature the inelastic carrier-optical-phonon scattering becomes more significant and limits the TEP below the hydrodynamic prediction. We support our observation by employing a Boltzmann theory incorporating disorder, electron interactions, and optical phonons. PMID:27081996

  19. Enhanced Thermoelectric Power in Graphene: Violation of the Mott Relation by Inelastic Scattering

    NASA Astrophysics Data System (ADS)

    Ghahari, Fereshte; Xie, Hong-Yi; Taniguchi, Takashi; Watanabe, Kenji; Foster, Matthew S.; Kim, Philip

    2016-04-01

    We report the enhancement of the thermoelectric power (TEP) in graphene with extremely low disorder. At high temperature we observe that the TEP is substantially larger than the prediction of the Mott relation, approaching to the hydrodynamic limit due to strong inelastic scattering among the charge carriers. However, closer to room temperature the inelastic carrier-optical-phonon scattering becomes more significant and limits the TEP below the hydrodynamic prediction. We support our observation by employing a Boltzmann theory incorporating disorder, electron interactions, and optical phonons.

  20. RAPID COMMUNICATION: Novel high performance small-scale thermoelectric power generation employing regenerative combustion systems

    NASA Astrophysics Data System (ADS)

    Weinberg, F. J.; Rowe, D. M.; Min, G.

    2002-07-01

    Hydrocarbon fuels have specific energy contents some two orders of magnitude greater than any electrical storage device. They therefore proffer an ideal source in the universal quest for compact, lightweight, long-lasting alternatives for batteries to power the ever-proliferating electronic devices. The motivation lies in the need to power, for example, equipment for infantry troops, for weather stations and buoys in polar regions which need to signal their readings intermittently to passing satellites, unattended over long periods, and many others. Fuel cells, converters based on miniaturized gas turbines, and other systems under intensive study, give rise to diverse practical difficulties. Thermoelectric devices are robust, durable and have no moving parts, but tend to be exceedingly inefficient. We propose regenerative combustion systems which mitigate this impediment and are likely to make high performance small-scale thermoelectric power generation applicable in practice. The efficiency of a thermoelectric generating system using preheat when operated between ambient and 1200 K is calculated to exceed the efficiency of the best present day thermoelectric conversion system by more than 20%.

  1. Enhancing Workgroup Performance.

    ERIC Educational Resources Information Center

    1998

    This document contains four papers from a symposium on enhancing workgroup performance in human resource development (HRD). "Formation of Cross-Cultural Global Teams: Making Informed Choices on Team Composition" (Robert L. Dilworth) describes how a mixed class of U.S. and international students identified their cultural and learning styles and…

  2. 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.

  3. Enhanced thermoelectric figure of merit in nanostructured n-type silicon germanium bulk alloy

    NASA Astrophysics Data System (ADS)

    Wang, X. W.; Lee, H.; Lan, Y. C.; Zhu, G. H.; Joshi, G.; Wang, D. Z.; Yang, J.; Muto, A. J.; Tang, M. Y.; Klatsky, J.; Song, S.; Dresselhaus, M. S.; Chen, G.; Ren, Z. F.

    2008-11-01

    The dimensionless thermoelectric figure of merit (ZT) of the n-type silicon germanium (SiGe) bulk alloy at high temperature has remained at about one for a few decades. Here we report that by using a nanostructure approach, a peak ZT of about 1.3 at 900 °C in an n-type nanostructured SiGe bulk alloy has been achieved. The enhancement of ZT comes mainly from a significant reduction in the thermal conductivity caused by the enhanced phonon scattering off the increased density of nanograin boundaries. The enhanced ZT will make such materials attractive in many applications such as solar, thermal, and waste heat conversion into electricity.

  4. 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.

  5. Surfactant-free synthesis of Bi2Te3-Te micro-nano heterostructure with enhanced thermoelectric figure of merit.

    PubMed

    Zhang, Yichi; Wang, Heng; Kräemer, Stephan; Shi, Yifeng; Zhang, Fan; Snedaker, Matt; Ding, Kunlun; Moskovits, Martin; Snyder, G Jeffrey; Stucky, Galen D

    2011-04-26

    An ideal thermoelectric material would be a semiconductor with high electrical conductivity and relatively low thermal conductivity: an "electron crystal, phonon glass". Introducing nanoscale heterostructures into the bulk TE matrix is one way of achieving this intuitively anomalous electron/phonon transport behavior. The heterostructured interfaces are expected to play a significant role in phonon scattering to reduce thermal conductivity and in the energy-dependent scattering of electrical carriers to improve the Seebeck coefficient. A nanoparticle building block assembly approach is plausible to fabricate three-dimensional heterostructured materials on a bulk commercial scale. However, a key problem in applying this strategy is the possible negative impact on TE performance of organic residue from the nanoparticle capping ligands. Herein, we report a wet chemical, surfactant-free, low-temperature, and easily up-scalable strategy for the synthesis of nanoscale heterophase Bi(2)Te(3)-Te via a galvanic replacement reaction. The micro-nano heterostructured material is fabricated bottom-up, by mixing the heterophase with commercial Bi(2)Te(3). This unique structure shows an enhanced zT value of ∼0.4 at room temperature. This heterostructure has one of the highest figures of merit among bismuth telluride systems yet achieved by a wet chemical bottom-up assembly. In addition, it shows a 40% enhancement of the figure of merit over our lab-made material without nanoscale heterostructures. This enhancement is mainly due to the decrease in the thermal conductivity while maintaining the power factor. Overall, this cost-efficient and room-temperature synthesis methodology provides the potential for further improvement and large-scale thermoelectric applications.

  6. Analysis of Thermoelectric Generator Performance by Use of Simulations and Experiments

    NASA Astrophysics Data System (ADS)

    Högblom, Olle; Andersson, Ronnie

    2014-06-01

    A method that enables accurate determination of contact resistances in thermoelectric generators and which gives detailed insight into how these reduce module performance is presented in this paper. To understand the importance taking thermal and electrical contact resistances into account in analysis of thermoelectric generators, full-scale modules were studied. Contact resistances were determined by means of non-linear regression analysis on the basis of results from 3D finite element simulations and experiments in a setup in which heat flow, voltage, and current were measured. Statistical evaluation showed that the model and the identified contact resistances enabled excellent prediction of performance over the entire range of operating conditions. It was shown that if contact resistances were not included in the analysis the simulations significantly over-predicted both heat flow and electric power output, and it was concluded that contact resistance should always be included in module simulations. The method presented in this paper gives detailed insight into how thermoelectric modules perform in general, and also enables prediction of potential improvement in module performance by reduction of contact resistances.

  7. Benefits of Carrier-Pocket Anisotropy to Thermoelectric Performance: The Case of p -Type AgBiSe2

    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 AgBiSe2. 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 AgBiSe2, while the conduction bands are more isotropic, and in our experiments do not attain high performance. AgBiSe2 has already exhibited a ZT value of 1.5 in a high-temperature disordered fccmore » 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 Bi2Te3 and PbTe. From our first principles and Boltzmann transport calculations we find that p-type AgBiSe2 has substantial promise as a room temperature thermoelectric, and estimate its performance.« less

  8. Enhancing the thermoelectric figure of merit through the reduction of bipolar thermal conductivity with heterostructure barriers

    SciTech Connect

    Bahk, Je-Hyeong Shakouri, Ali

    2014-08-04

    In this paper, we present theoretically that the thermoelectric figure of merit for a semiconductor material with a small band gap can be significantly enhanced near the intrinsic doping regime at high temperatures via the suppression of bipolar thermal conductivity when the minority carriers are selectively blocked by heterostructure barriers. This scheme is particularly effective in nanostructured materials where the lattice thermal conductivity is lowered by increased phonon scatterings at the boundaries, so that the electronic thermal conductivity including the bipolar term is limiting the figure of merit zT. We show that zT can be enhanced to above 3 for p-type PbTe, and above 2 for n-type PbTe at 900 K with minority carrier blocking, when the lattice thermal conductivity is as low as 0.3 W/m K.

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

    NASA Astrophysics Data System (ADS)

    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

    2015-04-01

    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 Bi0.5Sb1.5Te3 (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.

  10. Integrative characterization of the thermoelectric performance of an individual multiwalled carbon nanotube

    NASA Astrophysics Data System (ADS)

    Miao, Tingting; Shi, Shaoyi; Yan, Shen; Ma, Weigang; Zhang, Xing; Takahashi, Koji; Ikuta, Tatsuya

    2016-09-01

    Carbon nanotube-based organic composites and carbon nanotube networks are important flexible and lightweight thermoelectric materials. Characterization of the thermoelectric performance of individual carbon nanotubes is of vital importance for exploring the coupling mechanism between carbon nanotubes and organic composites, and proposing further improvement measures. The thermoelectric performance of an individual multiwalled carbon nanotube with a diameter of 66 nm has been comprehensively studied by applying our T-type method from 260 K to 420 K, using the same measurement configuration. The figure of merit increases from 4.84 × 10-8 to 1.32 × 10-6 on increasing the temperature, which is smaller than previous experimental results on carbon nanotube samples. The thermal conductivity increases from 706 W m-1 K-1 at 260 K to 769.3 W m-1 K-1 at 320 K, and then stays nearly constant until 420 K. The phonons dominate the thermal transport. The electrical conductivity exhibits thermally activated carrier generation and transport with an energy barrier of 194.5 meV. The Seebeck coefficient is in the range of 29.4-41.0 μV K-1 and tends to decrease with temperature.

  11. Performance of four-stage thermoelectric cooler for extended wavelength InGaAs detectors

    NASA Astrophysics Data System (ADS)

    Mo, De-feng; Yang, Li-yi; Liu, Da-fu; Xu, Qin-fei; Li, Tao; Li, Xue

    2015-04-01

    Experimental setup for evaluating four-stage thermoelectric cooler's performance was designed. Effects of input power, heat dissipation condition and heat load on the temperature difference (ΔT) of four-stage thermoelectric coolers' hot and cold faces were obtained experimentally. The result shows that, the ΔT increases as the input power increases. A linear relationship exists between input current and feedback voltage. In different cooling conditions, the ΔT of thermoelectric cooler (TEC) increases with the temperature of hot face. As the temperature increasing on hot face is 1K, the ΔT increasing of TEC can be about 0.5K. Meanwhile, the power consumption of TEC also increases slightly. Water condensation can be prevented in either dry nitrogen environment or vacuum environment, but the vacuum level has great influence to the ΔT, especially in low operation temperature. The better the vacuum level is, the smaller the convection heat loss has. When the operation temperature of focal plane array (FPA) is lower than 220K, it is prior to use vacuum packaging. Considering the Joule-heat of readout circuit and the heat loss of wire conduction, the minimum working temperature of FPA can reach below 200 K when the temperature of the hot face is 285K. And the coefficient of performance (COP) of TEC can increase sharply from 0.8% to 4% when the controlled operation temperature is 220K rather than 200K.

  12. Enhanced thermoelectric properties of phase-separating bismuth selenium telluride thin films via a two-step method

    SciTech Connect

    Takashiri, Masayuki Kurita, Kensuke; Hagino, Harutoshi; Miyazaki, Koji; Tanaka, Saburo

    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 propose 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.

  13. Plant performance enhancement program

    SciTech Connect

    Munchausen, J.H.

    1995-09-01

    The Plant Performance Enhancement Program (P{sup 2}EP), an initiative of the Electric Power Research Institute (EPRI), responds to strong industry incentives to improve nuclear plant thermal efficiency and electrical output. Launched by EPRI`s Nuclear Power Division, P{sup 2}EP operates within the purview of the Plant Support Engineering (PSE) Program, with day-to-day activities conducted out of the P{sup 2}EP office headquartered at EPRI`s facility in Charlotte, North Carolina. This alignment is consistent with EPFU`s strategic targets in support of industry goals, keeping P{sup 2}EP`s mission in clear focus: Helping utility thermal performance engineers improve the heat rate of nuclear power plants, thereby increasing unit average capacity and reducing plant operations and maintenance costs per kilowatt-hour.

  14. First-Principles Study on Thermoelectric Performance of Phosphorene and Phosphorene Oxide

    NASA Astrophysics Data System (ADS)

    Lee, Seungjun; Park, Jejune; Kang, Seoung-Hun; Kwon, Young-Kyun

    Using first-principles density functional theory, we studied thermoelectric properties of phosphorene and its oxidized structure called phosphorene oxide (PO). Using the identified stable configurations and electronic structrues of phosphorene and PO, we solved the Boltzmann transport equation to evaluate their electrical conductivity, Seebeck coefficient, and thermal conductivity contributed from both electrons and phonons. In order to correctly estimate the thermoelectric figure of merit or ZT values, it is indispensable to determine the relaxation time, which can be estimated by applying the deformation potential theory. We observe that the electrical conductivity of phosphorene is higher along the armchair direction than along the zigzag direction, while the thermal conductivity shows an opposite behavior. Because of such an orthogonal relation between the electrical and thermal conductivities, phosphorene exhibits quite a large ZT value along the armchair direction. It is, on the other hand, calculated that PO has electrical conductivity similar to phosphorene, however its thermal conductivity is significantly smaller than phosphorene, resulting in larger ZT values. we expect that PO can be utilized for a high performance thermoelectric application.

  15. 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%.

  16. Thermoelectric Performance of Donor-Acceptor-Donor Conjugated Polymers Based on Benzothiadiazole Derivatives

    NASA Astrophysics Data System (ADS)

    Ming, Shouli; Zhen, Shijie; Lin, Kaiwen; Zhao, Li; Xu, Jingkun; Lu, Baoyang; Wang, Liangying; Xiong, Jinhua; Zhu, Zhengzhou

    2015-06-01

    Donor-acceptor-donor conjugated polymers are superior to other thermoelectric organic materials because it is much easier to modify their structure to reduce the bandgap between the conduction and valence bands, which is desirable for thermoelectric materials with high Seebeck coefficients. Despite this, studies of the thermoelectric performance of donor-acceptor-donor conjugated polymers are rare. In this study, four low-bandgap donor-acceptor-donor conjugated polymers, poly(4,7-bis(2,3-dihydrothieno[3,4- b][1,4] dioxin-5-yl)benzo[ c][1,2,5]thiadiazole) (PEBTE), poly(4,7-bis(2,3-dihydrothieno[3,4- b][1,4]dioxin-5-yl)benzo[ c][1,2,5]selenadiazole) (PEBSeE), poly (4,7-bis(2,3-dihydrothieno[3,4- b][1,4]dioxin-5-yl)-[1,2,5]thiadiazolo [3,4- c] pyridine) (PEPTE), and poly(4,7-bis(2,3-dihydrothieno[3,4- b][1,4]dioxin-5-yl)-[1,2,5]selenadiazolo[3,4- c]pyridine) (PEPSeE), were deposited by electrochemical polymerization of 4,7-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)benzo[c][1,2,5]thiadiazole (EBTE), 4,7-bis(2,3-dihydro-thieno[3,4-b][1,4] dioxin-5-yl)benzo[c][1,2,5]selenadiazole (EBSeE), 4,7-bis(2,3-dihydrothieno [3,4-b][1,4]dioxin-5-yl)-[1,2,5]thiadiazolo[3,4-c] pyridine (EPTE) and 4,7-bis (2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-[1,2,5] selenadiazolo[3,4-c]pyridine (EPSeE), respectively and their thermoelectric performance was investi- gated. Compared with polyselenophenes, PEBTE and PEBSeE in pressed pellets had higher electrical conductivity (10-1-101 S cm-1) but lower Seebeck coefficient (14.0 μV K-1) at room temperature. Future work may focus on treatment of these donor-acceptor-donor polymers to improve their electrical conductivity and Seebeck coefficient, and further investigation of their thermoelectric performance.

  17. Enhanced thermoelectric power and electronic correlations in RuSe{sub 2}

    SciTech Connect

    Wang, Kefeng Wang, Aifeng; Tomic, A.; Wang, Limin; Petrovic, C.; Abeykoon, A. M. Milinda; Dooryhee, E.; Billinge, S. J. L.

    2015-04-01

    We report the electronic structure, electric and thermal transport properties of Ru{sub 1−x}Ir{sub x}Se{sub 2} (x ≤ 0.2). RuSe{sub 2} is a semiconductor that crystallizes in a cubic pyrite unit cell. The Seebeck coefficient of RuSe{sub 2} 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{sub 0.8}Ir{sub 0.2}Se{sub 2} 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 RuSb{sub 2}.

  18. Enhanced thermoelectric power and electronic correlations in RuSe2

    NASA Astrophysics Data System (ADS)

    Wang, Kefeng; Wang, Aifeng; Tomic, A.; Wang, Limin; Abeykoon, A. M. Milinda; Dooryhee, E.; Billinge, S. J. L.; Petrovic, C.

    2015-04-01

    We report the electronic structure, electric and thermal transport properties of Ru1-xIrxSe2 (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. Ru0.8Ir0.2Se2 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.

  19. 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

  20. Enhanced Thermoelectric Properties in the Counter-Doped SnTe System with Strained Endotaxial SrTe.

    PubMed

    Zhao, Li-Dong; Zhang, Xiao; Wu, Haijun; Tan, Gangjian; Pei, Yanling; Xiao, Yu; Chang, Cheng; Wu, Di; Chi, Hang; Zheng, Lei; Gong, Shengkai; Uher, Ctirad; He, Jiaqing; Kanatzidis, Mercouri G

    2016-02-24

    We report enhanced thermoelectric performance in SnTe, where significantly improved electrical transport properties and reduced thermal conductivity were achieved simultaneously. The former was obtained from a larger hole Seebeck coefficient through Fermi level tuning by optimizing the carrier concentration with Ga, In, Bi, and Sb dopants, resulting in a power factor of 21 μW cm(-1) K(-2) and ZT of 0.9 at 823 K in Sn(0.97)Bi(0.03)Te. To reduce the lattice thermal conductivity without deteriorating the hole carrier mobility in Sn(0.97)Bi(0.03)Te, SrTe was chosen as the second phase to create strained endotaxial nanostructures as phonon scattering centers. As a result, the lattice thermal conductivity decreases strongly from ∼2.0 Wm(-1) K(-1) for Sn(0.97)Bi(0.03)Te to ∼1.2 Wm(-1) K(-1) as the SrTe content is increased from 0 to 5.0% at room temperature and from ∼1.1 to ∼0.70 Wm(-1) K(-1) at 823 K. For the Sn(0.97)Bi(0.03)Te-3% SrTe sample, this leads to a ZT of 1.2 at 823 K and a high average ZT (for SnTe) of 0.7 in the temperature range of 300-823 K, suggesting that SnTe is a robust candidate for medium-temperature thermoelectric applications. PMID:26871965

  1. 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.

  2. Potential improvements in SiGe radioisotope thermoelectric generator performance

    SciTech Connect

    Mowery, A.L.

    1999-01-01

    In accordance with NASA{close_quote}s slogan: {open_quotes}Better, Cheaper, Faster,{close_quotes} this paper will address potential improvements to SiGe RTG technology to make them Better. RTGs are doubtless cheaper than {open_quotes}paper designs{close_quotes} which are better and cheaper until development, performance and safety test costs are considered. RTGs have the advantage of being fully developed and tested in the rigors of space for over twenty years. Further, unless a new system can be accelerated tested, as were the RTGs, they cannot be deployed reliably unless a number of systems have succeeded for test periods exceeding the mission lifetime. Two potential developments are discussed that can improve the basic RTG performance by 10 to 40{sup +}{percent} depending on the mission profile. These improvements could be demonstrated in years. Accelerated testing could also be performed in this period to preserve existing RTG reliability. Data from a qualification tested RTG will be displayed, while not definitive, to support the conclusions. Finally, it is anticipated that other investigators will be encouraged to suggest further modifications to the basic RTG design to improve its performance. {copyright} {ital 1999 American Institute of Physics.}

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

    NASA Astrophysics Data System (ADS)

    Zhou, Min; Gibbs, Zachary M.; Wang, Heng; Han, Yemao; Li, Laifeng; Snyder, G. Jeffrey

    2016-07-01

    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 (nH) and extrinsic dopant concentration (NI, NAg) in the stabilization region, where a linear increase of dopant concentration does not lead to linear response in the measured nH. Upon substituting extrinsic dopants beyond a certain amount, the nH 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.

  4. Right sizes of nano- and microstructures for high-performance and rigid bulk thermoelectrics

    PubMed Central

    Wang, Hongchao; Bahk, Je-Hyeong; Kang, Chanyoung; Hwang, Junphil; Kim, Kangmin; Kim, Jungwon; Burke, Peter; Bowers, John E.; Gossard, Arthur C.; Shakouri, Ali; Kim, Woochul

    2014-01-01

    In this paper, we systematically investigate three different routes of synthesizing 2% Na-doped PbTe after melting the elements: (i) quenching followed by hot-pressing (QH), (ii) annealing followed by hot-pressing, and (iii) quenching and annealing followed by hot-pressing. We found that the thermoelectric figure of merit, zT, strongly depends on the synthesis condition and that its value can be enhanced to ∼2.0 at 773 K by optimizing the size distribution of the nanostructures in the material. Based on our theoretical analysis on both electron and thermal transport, this zT enhancement is attributed to the reduction of both the lattice and electronic thermal conductivities; the smallest sizes (2∼6 nm) of nanostructures in the QH sample are responsible for effectively scattering the wide range of phonon wavelengths to minimize the lattice thermal conductivity to ∼0.5 W/m K. The reduced electronic thermal conductivity associated with the suppressed electrical conductivity by nanostructures also helped reduce the total thermal conductivity. In addition to the high zT of the QH sample, the mechanical hardness is higher than the other samples by a factor of around 2 due to the smaller grain sizes. Overall, this paper suggests a guideline on how to achieve high zT and mechanical strength of a thermoelectric material by controlling nano- and microstructures of the material. PMID:25028497

  5. Right sizes of nano- and microstructures for high-performance and rigid bulk thermoelectrics.

    PubMed

    Wang, Hongchao; Bahk, Je-Hyeong; Kang, Chanyoung; Hwang, Junphil; Kim, Kangmin; Kim, Jungwon; Burke, Peter; Bowers, John E; Gossard, Arthur C; Shakouri, Ali; Kim, Woochul

    2014-07-29

    In this paper, we systematically investigate three different routes of synthesizing 2% Na-doped PbTe after melting the elements: (i) quenching followed by hot-pressing (QH), (ii) annealing followed by hot-pressing, and (iii) quenching and annealing followed by hot-pressing. We found that the thermoelectric figure of merit, zT, strongly depends on the synthesis condition and that its value can be enhanced to ∼ 2.0 at 773 K by optimizing the size distribution of the nanostructures in the material. Based on our theoretical analysis on both electron and thermal transport, this zT enhancement is attributed to the reduction of both the lattice and electronic thermal conductivities; the smallest sizes (2 ∼ 6 nm) of nanostructures in the QH sample are responsible for effectively scattering the wide range of phonon wavelengths to minimize the lattice thermal conductivity to ∼ 0.5 W/m K. The reduced electronic thermal conductivity associated with the suppressed electrical conductivity by nanostructures also helped reduce the total thermal conductivity. In addition to the high zT of the QH sample, the mechanical hardness is higher than the other samples by a factor of around 2 due to the smaller grain sizes. Overall, this paper suggests a guideline on how to achieve high zT and mechanical strength of a thermoelectric material by controlling nano- and microstructures of the material.

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

    NASA Astrophysics Data System (ADS)

    Banik, Ananya; Biswas, Kanishka

    2016-10-01

    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 the 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 Sn1-xAgxTe1-xIx samples. A maximum thermoelectric figure of merit, zT, of ~1.05 was achieved at 860 K in high quality crystalline ingot of p-type Sn0.95Ag0.05Te0.95I0.05.

  7. Thermoelectric performance of half-Heusler compounds TiNiSn and TiCoSb

    NASA Astrophysics Data System (ADS)

    Wang, L. L.; Miao, L.; Wang, Z. Y.; Wei, W.; Xiong, R.; Liu, H. J.; Shi, J.; Tang, X. F.

    2009-01-01

    The electronic structures of half-Heusler compounds TiNiSn and TiCoSb are investigated by using the full-potential linearized augmented plane-wave method. When the spin-orbital coupling is included in the calculations, there is only a slight change in the energy band structures. The transport coefficients (Seebeck coefficient, electrical conductivity, and power factor) are then calculated within the Boltzmann theory, and further evaluated as a function of chemical potential assuming a rigid band picture. Our calculations offer a valuable insight on how to improve the thermoelectric performance of these two compounds.

  8. LaPtSb: a half-Heusler compound with high thermoelectric performance.

    PubMed

    Xue, Q Y; Liu, H J; Fan, D D; Cheng, L; Zhao, B Y; Shi, J

    2016-07-21

    The electronic and transport properties of the half-Heusler compound LaPtSb are investigated by performing first-principles calculations combined with semi-classical Boltzmann theory and deformation potential theory. Compared with many typical half-Heusler compounds, LaPtSb exhibits an obviously larger power factor at room temperature, especially for the n-type system. Together with the very low lattice thermal conductivity, the thermoelectric figure of merit (ZT) of LaPtSb can be optimized to a record high value of 2.2 by fine tuning the carrier concentration.

  9. LaPtSb: a half-Heusler compound with high thermoelectric performance.

    PubMed

    Xue, Q Y; Liu, H J; Fan, D D; Cheng, L; Zhao, B Y; Shi, J

    2016-07-21

    The electronic and transport properties of the half-Heusler compound LaPtSb are investigated by performing first-principles calculations combined with semi-classical Boltzmann theory and deformation potential theory. Compared with many typical half-Heusler compounds, LaPtSb exhibits an obviously larger power factor at room temperature, especially for the n-type system. Together with the very low lattice thermal conductivity, the thermoelectric figure of merit (ZT) of LaPtSb can be optimized to a record high value of 2.2 by fine tuning the carrier concentration. PMID:27321233

  10. Superior intrinsic thermoelectric performance with zT of 1.8 in single-crystal and melt-quenched highly dense Cu(2-x)Se bulks.

    PubMed

    Zhao, Lan-ling; Wang, Xiao-lin; Wang, Ji-yang; Cheng, Zhen-xiang; Dou, Shi-xue; Wang, Jun; Liu, Li-qiang

    2015-01-08

    Practical applications of the high temperature thermoelectric materials developed so far are partially obstructed by the costly and complicated fabrication process. In this work, we put forward two additional important properties for thermoelectric materials, high crystal symmetry and congruent melting. We propose that the recently discovered thermoelectric material Cu2-xSe, with figure of merit, zT, over 1.5 at T of ~ 1000 K, should meet these requirements, based on our analysis of its crystal structure and the Cu-Se binary phase diagram. We found that its excellent thermoelectric performance is intrinsic, and less dependent on grain size, while highly dense samples can be easily fabricated by a melt-quenching approach. Our results reveal that the melt-quenched samples and single crystals exhibit almost the same superior thermoelectric performance, with zT as high as 1.7-1.8 at T of ~973 K. Our findings not only provide a cheap and fast fabrication method for highly dense Cu(2-x)Se bulks with superior thermoelectric performance, paving the way for possible commercialization of Cu2-xSe as an outstanding component in practical thermoelectric modules, but also provide guidance in searching for new classes of thermoelectric systems with high crystal symmetry or further improving the cost performance of other existing congruent-melting thermoelectric materials.

  11. A quick and efficient measurement technique for performance evaluation of thermoelectric materials

    NASA Astrophysics Data System (ADS)

    Rao, Ashwin; Banjade, Pawan; Bosak, Gregg; Joshi, Binay; Keane, Jennifer; Nally, Luke; Peng, Adam; Perera, Susanthri; Waring, Alfred; Joshi, Giri; Poudel, Bed

    2016-10-01

    Evaluating the performance of thermoelectric (TE) materials is critical for developing an efficient long lasting thermoelectric generator. Various parameters like resistance, TE power, TE efficiency as a function of temperature and time play an important role in developing and optimizing TE materials and legs. If one needs to evaluate the TE legs for performance or contact metallization optimization, study of a brazed or packaged device everytime could prove to be an expensive, time consuming process especially as a quick intermediate qualification. In this work, a simple approach that uses eutectic Gallium Indium (Ga-In) paste as a metallizing substitute with good electrical/thermal contact is employed which also avoids the need for brazing/welding (or any permanent joining) and provides a reliable platform for a quick leg qualification. Using open circuit voltage (V oc) and device voltage (V d), one can evaluate important TE quantities like peak power, material resistance changes, peak current and power versus current characteristics to understand the leg performance. The proposed approach is successfully demonstrated with three different TE material systems namely Bismuth Telluride, Skutterudite and Half Heusler systems.

  12. High thermoelectric performance by resonant dopant indium in nanostructured SnTe

    PubMed Central

    Zhang, Qian; Liao, Bolin; Lan, Yucheng; Lukas, Kevin; Liu, Weishu; Esfarjani, Keivan; Opeil, Cyril; Broido, David; Chen, Gang; Ren, Zhifeng

    2013-01-01

    From an environmental perspective, lead-free SnTe would be preferable for solid-state waste heat recovery if its thermoelectric figure-of-merit could be brought close to that of the lead-containing chalcogenides. In this work, we studied the thermoelectric properties of nanostructured SnTe with different dopants, and found indium-doped SnTe showed extraordinarily large Seebeck coefficients that cannot be explained properly by the conventional two-valence band model. We attributed this enhancement of Seebeck coefficients to resonant levels created by the indium impurities inside the valence band, supported by the first-principles simulations. This, together with the lower thermal conductivity resulting from the decreased grain size by ball milling and hot pressing, improved both the peak and average nondimensional figure-of-merit (ZT) significantly. A peak ZT of ∼1.1 was obtained in 0.25 atom % In-doped SnTe at about 873 K. PMID:23901106

  13. High thermoelectric performance by resonant dopant indium in nanostructured SnTe.

    PubMed

    Zhang, Qian; Liao, Bolin; Lan, Yucheng; Lukas, Kevin; Liu, Weishu; Esfarjani, Keivan; Opeil, Cyril; Broido, David; Chen, Gang; Ren, Zhifeng

    2013-08-13

    From an environmental perspective, lead-free SnTe would be preferable for solid-state waste heat recovery if its thermoelectric figure-of-merit could be brought close to that of the lead-containing chalcogenides. In this work, we studied the thermoelectric properties of nanostructured SnTe with different dopants, and found indium-doped SnTe showed extraordinarily large Seebeck coefficients that cannot be explained properly by the conventional two-valence band model. We attributed this enhancement of Seebeck coefficients to resonant levels created by the indium impurities inside the valence band, supported by the first-principles simulations. This, together with the lower thermal conductivity resulting from the decreased grain size by ball milling and hot pressing, improved both the peak and average nondimensional figure-of-merit (ZT) significantly. A peak ZT of ∼1.1 was obtained in 0.25 atom % In-doped SnTe at about 873 K.

  14. Performance-enhancing supplements.

    PubMed

    Pecci, M A; Lombardo, J A

    2000-11-01

    Supplements that are marketed as ergogenic aids have achieved widespread use in the United States. In image-conscious society, these agents are not only being consumed by athletes, but also by those looking for a quick fix to enhance their appearance. Many assume that the performance claims made by the manufacturers are based on actual data, and that these agents must be safe because they are sold to the general public. Unfortunately, in most cases these assumptions are false. Creatine has become very popular, particularly among college and high school athletes. Studies within the last 5 years have shown that creatine does seem to have certain ergogenic benefits in a laboratory setting. It is not currently known whether these benefits actually can be transferred to the playing field. Although creatine has not consistently been shown to cause any major side effects, there is some question regarding creatine's effect on the kidneys, particularly with long-term use. Also, the safety of supplementation in children and adolescents has not been examined at all; its use in this population should be discouraged until there are more data. Androstenedione is an agent that has received a large amount of popular press in the last year, and this has led to an surge in its usage. It is believed to exert its ergogenic effects through conversion to testosterone. But what limited data are available suggest that at the recommended dosage, it does not cause any measurable change in testosterone levels, or provide any ergogenic benefit in inexperienced weight lifters. Also, it has yet to be determined whether androstenedione causes any of the side effects often attributed to use of the illegal anabolic steroids. Its mechanism of action suggests it has the potential to cause many of these negative effects. Studies are just beginning to appear in the literature, and certainly more data need to be gathered before androstenedione supplementation can be recommended for use as an ergogenic

  15. Formation of nanodots and enhancement of thermoelectric power induced by ion irradiation in PbTe:Ag composite thin films

    NASA Astrophysics Data System (ADS)

    Bala, Manju; Meena, Ramcharan; Gupta, Srashti; Pannu, Compesh; Tripathi, Tripurari S.; Varma, Shikha; Tripathi, Surya K.; Asokan, K.; Avasthi, Devesh K.

    2016-07-01

    Present study demonstrates an enhancement in thermoelectric power of 10% Ag doped PbTe (PbTe:Ag) thin films when irradiated with 200 keV Ar ion. X-ray diffraction showed an increase in crystallinity for both PbTe and PbTe:10Ag nano-composite films after Ar ion irradiation due to annealing of defects in the grain boundaries. The preferential sputtering of Pb and Te ions in comparison to Ag ions resulted in the formation of nano-dots. This was further confirmed by X-ray photoelectron spectroscopy (XPS). Such an enhancement in thermoelectric power of irradiated PbTe:10Ag films in comparison to pristine PbTe:10Ag film is attributed to the decrease in charge carrier concentration that takes part in the transport process via restricting the tunneling of carriers through the wider potential barrier formed at the interface of nano-dots.

  16. Numerical Modeling of Year-Round Performance of a Solar Parabolic Dish Thermoelectric Generator

    NASA Astrophysics Data System (ADS)

    Muthu, G.; Shanmugam, S.; Veerappan, AR.

    2015-08-01

    This paper presents the year-round performance of a solar parabolic dish thermoelectric generator under different values of operating parameters such as ambient temperature, wind velocity, direct normal irradiation, and water inlet temperature to the heat sink. The solar thermoelectric generator (TEG) is examined for an Indian location of Tiruchirappalli. The electrical power output and TEG efficiency are maximum during the months of April and August, while they are minimum during the month of December. It is found that the monthly average hot-side temperature of the TEG varies from 556.53 K to 592.68 K and the cold-side temperature of the TEG varies from 413.21 K to 438.91 K. When the hot-side temperature reaches the optimum value, the conversion efficiency is reduced, although the power increases. A TEG model is useful to find the temperature of the junctions for different operating parameter values and predict the performance of the TEG at any time. A small standalone power-generating system using this technology is a promising option.

  17. 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).

  18. 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.

  19. 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. PMID:27385824

  20. 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.

  1. Higher thermoelectric performance of Zintl phases (Eu0.5Yb0.5)1-xCaxMg2Bi2 by band engineering and strain fluctuation

    NASA Astrophysics Data System (ADS)

    Shuai, Jing; Geng, Huiyuan; Lan, Yucheng; Zhu, Zhuan; Wang, Chao; Liu, Zihang; Bao, Jiming; Chu, Ching-Wu; Sui, Jiehe; Ren, Zhifeng

    2016-07-01

    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.

  2. Performance Simulation of a Flat-Plate Thermoelectric Module Consisting of Square Truncated Pyramid Elements

    NASA Astrophysics Data System (ADS)

    Oki, Sae; Suzuki, Ryosuke O.

    2016-09-01

    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.

  3. 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.

  4. Bismuth Interfacial Doping of Organic Small Molecules for High Performance n-type Thermoelectric Materials.

    PubMed

    Huang, Dazhen; Wang, Chao; Zou, Ye; Shen, Xingxing; Zang, Yaping; Shen, Hongguang; Gao, Xike; Yi, Yuanping; Xu, Wei; Di, Chong-An; Zhu, Daoben

    2016-08-26

    Development of chemically doped high performance n-type organic thermoelectric (TE) materials is of vital importance for flexible power generating applications. For the first time, bismuth (Bi) n-type chemical doping of organic semiconductors is described, enabling high performance TE materials. The Bi interfacial doping of thiophene-diketopyrrolopyrrole-based quinoidal (TDPPQ) molecules endows the film with a balanced electrical conductivity of 3.3 S cm(-1) and a Seebeck coefficient of 585 μV K(-1) . The newly developed TE material possesses a maximum power factor of 113 μW m(-1)  K(-2) , which is at the forefront for organic small molecule-based n-type TE materials. These studies reveal that fine-tuning of the heavy metal doping of organic semiconductors opens up a new strategy for exploring high performance organic TE materials. PMID:27496293

  5. 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.

  6. 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.

  7. What are the Historical and Future Impacts of Temperature Variability on Thermoelectric Power Plant Performance?

    NASA Astrophysics Data System (ADS)

    Henry, C.; Pratson, L.

    2015-12-01

    Current literature hypothesize that climate change-driven temperature increases will negatively affect the power production capacity of thermoelectric power plants, which currently produce ~88% of electricity used in the United States. This impact can occur through 1) warm cooling water that reduces the quantity of heat removed from the once-through (open-loop) steam system, 2) increased air temperature and/or humidity that decrease the amount of heat absorption in cooling towers/ponds of wet-recirculating (closed-loop) plants, and 3) environmental protection regulations that impose restrictions on both cooling water withdrawal volume and temperature of discharge. However, despite the widespread consensus that temperature and power generation are negatively related, different models yield a range of results and the magnitude of effects is uncertain. In this study, we test current literature's model predictions using historical data by assembling and analyzing a database of relevant parameters from distinct sources. We examine how daily and seasonal changes in cooling water, ambient air, and wet bulb temperatures have historically impacted coal and natural gas power plants in the U.S., focusing on 39 plants over a period up to 14 years. This allows us to assess how future changes in temperatures may affect generation. Our results suggest that water and ambient air temperatures have a lower impact on thermoelectric plant performance than previously predicted. Moreover, we find that recirculating power plants are more resilient to temperature variability than are once-through plants.

  8. 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

    2011-07-01

    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. PMID:21532584

  9. 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

  10. Convergence of multi-valley bands as the electronic origin of high thermoelectric performance in CoSb3 skutterudites

    NASA Astrophysics Data System (ADS)

    Tang, Yinglu; Gibbs, Zachary M.; Agapito, Luis A.; Li, Guodong; Kim, Hyun-Sik; Nardelli, Marco Buongiorno; Curtarolo, Stefano; Snyder, G. Jeffrey

    2015-12-01

    Filled skutterudites RxCo4Sb12 are excellent n-type thermoelectric materials owing to their high electronic mobility and high effective mass, combined with low thermal conductivity associated with the addition of filler atoms into the void site. The favourable electronic band structure in n-type CoSb3 is typically attributed to threefold degeneracy at the conduction band minimum accompanied by linear band behaviour at higher carrier concentrations, which is thought to be related to the increase in effective mass as the doping level increases. Using combined experimental and computational studies, we show instead that a secondary conduction band with 12 conducting carrier pockets (which converges with the primary band at high temperatures) is responsible for the extraordinary thermoelectric performance of n-type CoSb3 skutterudites. A theoretical explanation is also provided as to why the linear (or Kane-type) band feature is not beneficial for thermoelectrics.

  11. 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

    2016-07-01

    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. PMID:27237453

  12. Enhanced Thermoelectric Properties of Cu2ZnSnSe4 with Ga-doping

    DOE PAGES

    Wei, Kaya; Beauchemin, Laura; Wang, Hsin; Porter, Wallace D.; Martin, Joshua; Nolas, George S.

    2015-08-10

    Gallium doped Cu2ZnSnSe4 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 (S2/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 part of the continuingmore » effort to explore different quaternary chalcogenide compositions and structure types, as this class of materials continues to be of interest for thermoelectrics applications.« less

  13. Great enhancements in the thermoelectric power factor of BiSbTe nanostructured films with well-ordered interfaces.

    PubMed

    Chang, Hsiu-Cheng; Chen, Chun-Hua; Kuo, Yung-Kang

    2013-08-01

    An innovative concept of twin-enhanced thermoelectricity was proposed to fundamentally resolve the high electrical resistance while not degrading the phonon scattering of the thermoelectric nanoassemblies. Under this frame, a variety of highly oriented and twinned bismuth antimony telluride (BixSb2-xTe3) nanocrystals were successfully fabricated by a large-area pulsed-laser deposition (PLD) technique on insulated silicon substrates at various deposition temperatures. The significant presence of the nonbasal- and basal-plane twins across the hexagonal BiSbTe nanocrystals, which were experimentally and systematically observed for the first time, evidently contributes to the unusually high electrical conductivity of ~2700 S cm(-1) and the power factor of ~25 μW cm(-1) K(-2) as well as the relatively low thermal conductivity of ~1.1 W m(-1) K(-1) found in these nanostructured films. PMID:23803956

  14. YbCu2Si2-LaCu2Si2 Solid Solutions with Enhanced Thermoelectric Power Factors

    NASA Astrophysics Data System (ADS)

    Lehr, Gloria J.; Morelli, Donald T.; Jin, Hyungyu; Heremans, Joseph P.

    2015-06-01

    Cryogenic Peltier coolers are ideal for cooling infrared sensors on satellites. To make these thermoelectric devices a realistic option for this application, the efficiency of thermoelectric materials at cryogenic temperatures must be substantially enhanced. Intermediate valence Yb-based compounds have large peaks in the Seebeck coefficient at low temperatures; to optimize these materials this must be understood. We created solid solutions between the intermediate valence compound YbCu2Si2 and an isostructural compound LaCu2Si2 to manipulate the temperature at which the Seebeck coefficient peaks and to maximize zT by reduction of lattice thermal conductivity. An enormous power factor of 110 μW/cm K2 at 100 K and a maximum zT of 0.14 at 125 K were achieved for one of these solid solutions.

  15. Coupled quantum-scattering modeling of thermoelectric performance of nanostructured materials using the non-equilibrium Green's function method

    NASA Astrophysics Data System (ADS)

    Bulusu, Anuradha

    Semi-classical transport models based on Boltzmann and Fermi-Dirac statistics have been very effective identifying the pertinent physical parameters responsible for thermoelectric performance in bulk materials. Reliance on Boltzmann-based models has produced a culture of "smaller is better" research, where the reduction in size is expected to produce limitless increase in performance. Experimental observations especially in the case of thermoelectric performance of nanoscale devices have not exhibited this behavior. The semi-classical Boltzmann models are based on the relaxation-time approximation and cannot model strong non-equilibrium transport. In addition, wave effects in these models are included through correction terms that cannot suitably capture their influence on transport. A coupled quantum-scattering model to study thermoelectric performance of nanoscale structures is proposed through the nonequilibrium Green's function method. The model includes all the pertinent physics of the wave nature of electrons while coupling election-phonon scattering effects. The NEGF method is used to study the performance of silicon nano-films and nanowires as well as strained quantum well Si/Ge/Si superlattices as a function of doping, effective mass and in the case of superlattices, substrate strain and superlattice geometry. Results suggest that the power factor of nanostructured materials is dominated by the electrical conductivity which in turn is strongly influenced by quantum confinement effects and electron-phonon scattering effects. No significant improvement in the Seebeck coefficient is observed due to the decrease in dimensionality of the structure. The NEGF method can be used as a tool to design structure with optimized values of doping, effective mass, substrate strain and superlattice geometry taking into consideration the effects of electron confinement and scattering. The method developed in this research can be used as a framework to guide further studies

  16. CsBi4Te6: a new facile synthetic method and mid-temperature thermoelectric performance.

    PubMed

    Lin, Hua; Chen, Hong; Yu, Ju-Song; Zheng, Yu-Jun; Liu, Peng-Fei; Ali Khan, Muhammad; Wu, Li-Ming

    2016-07-26

    CsBi4Te6 is one of the best performing low-temperature thermoelectric (TE) materials. However, it has not received worldwide intensive investigation due to the limitation of synthetic methods. Here we report a new facile approach by not using the reactive Cs metal and the mid-temperature TE properties have been studied for the first time. PMID:27383416

  17. A theoretical study on the performances of thermoelectric heat engine and refrigerator with two-dimensional electron reservoirs

    SciTech Connect

    Luo, Xiaoguang Long, Kailin; Wang, Jun; Qiu, Teng; He, Jizhou; Liu, Nian

    2014-06-28

    Theoretical thermoelectric nanophysics models of low-dimensional electronic heat engine and refrigerator devices, comprising two-dimensional hot and cold reservoirs and an interconnecting filtered electron transport mechanism have been established. The models were used to numerically simulate and evaluate the thermoelectric performance and energy conversion efficiencies of these low-dimensional devices, based on three different types of electron transport momentum-dependent filters, referred to herein as k{sub x}, k{sub y}, and k{sub r} filters. Assuming the Fermi-Dirac distribution of electrons, expressions for key thermoelectric performance parameters were derived for the resonant transport processes, in which the transmission of electrons has been approximated as a Lorentzian resonance function. Optimizations were carried out and the corresponding optimized design parameters have been determined, including but not limited to the universal theoretical upper bound of the efficiency at maximum power for heat engines, and the maximum coefficient of performance for refrigerators. From the results, it was determined that k{sub r} filter delivers the best thermoelectric performance, followed by the k{sub x} filter, and then the k{sub y} filter. For refrigerators with any one of three filters, an optimum range for the full width at half maximum of the transport resonance was found to be <2k{sub B}T.

  18. Performance-enhancing drug use.

    PubMed

    Green, Gary A

    2009-09-01

    According to Gary Green, MD, everyone who deals with athletes is a "stakeholder" in the issue of performance-enhancing drugs and can influence athletes in a positive or negative role. In this issue of ORTHOPEDICS, Dr Green shares his thoughts on testing, prevention, and education of performance-enhancing drug use.

  19. Raising the Thermoelectric Performance of Fe3CoSb12 Skutterudites via Nd Filling and In-Situ Nanostructuring.

    PubMed

    Guo, Lijie; Cai, Zhengwei; Xu, Xiaolong; Peng, Kunling; Wang, Guiwen; Wang, Guoyu; Zhou, Xiaoyuan

    2016-04-01

    p-type skutterudites NdxFe3CoSb12 with x equaling 0.8, 0.85, 0.9, 0.95, 1.0 have been synthesized by solid state reaction followed by spark plasma sintering. The influence of Nd filling on electrical and thermal transport properties has been investigated in the Nd-filled skutterudite compounds in the temperature range from room temperature to 800 K. It was found that the Seebeck coefficient is drastically enhanced via filling Nd in p-Type skutterudites as well as the corresponding power factor although electrical conductivity is reduced. In addition, a large reduction in thermal conductivity is achieved by Nd fillers through rattling effect along with the in-situ nanostructured precipitate through scattering phonons with much wider frequency. These concomitant effects result in an enhanced thermoelectric performance with the dimensionless figure of merit ZT. These observations demonstrate an exciting scientific opportunity to raise the figure-of-merit of p-type skutterudites. PMID:27451721

  20. 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

  1. Experimental Performance of a Thermoelectric Heat-Pump Drying System for Drying Herbs

    NASA Astrophysics Data System (ADS)

    Wongsim, K.; Jamradloedluk, J.; Lertsatitthanakorn, C.; Siriamornpun, S.; Rungsiyopas, M.; Soponronnarit, S.

    2015-06-01

    In this study we investigated thermoelectric (TE) heat-pump drying of laurel clock vine leaves, and the effect of drying-air temperature on the characteristics of the leaves. The TE drying system comprised four TE modules each with its own rectangular fin heat sink. The hot side of each TE module was fixed to its own heat sink; the cold sides were fixed to heat-pipe heat sinks and a drying chamber. The drying time depended on drying-air temperature. The heating capacity and coefficient of performance (COP) increased as the current supplied to the TE modules was increased. Calculated COP for the entire TE heat-pump drying system were 1.28 and 0.81 for drying-air temperatures of 50 and 40°C, respectively.

  2. Hybrid thermoelectric piezoelectric generator

    NASA Astrophysics Data System (ADS)

    Montgomery, D. S.; Hewitt, C. A.; Carroll, D. L.

    2016-06-01

    This work presents an integration of flexible thermoelectric and piezoelectric materials into a single device structure. This device architecture overcomes several prohibitive issues facing the combination of traditional thermoelectric and piezoelectric generators, while optimizing performance of the combined power output. The structure design uses a carbon nanotube/polymer thin film as a flexible thermoelectric generator that doubles as an electrode on a piezoelectric generator made of poly(vinylidene fluoride). An example 2 × 2 array of devices is shown to generate 89% of the maximum thermoelectric power, and provide 5.3 times more piezoelectric voltage when compared with a traditional device.

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

    DOE PAGES

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

    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

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

    SciTech Connect

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

    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 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. As a result, selective doping in bandgap engineered core/shell nanowires is proposed for enhancing the thermoelectric power.

  5. 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

    2016-01-01

    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.

  6. 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

    2016-01-01

    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. PMID:26606258

  7. Half-Heusler thermoelectrics: a complex class of materials.

    PubMed

    Bos, Jan-Willem G; Downie, Ruth A

    2014-10-29

    Half-Heusler thermoelectrics first attracted interest in the late-1990s and are currently undergoing a renaissance. This has been driven by improved synthesis, processing and characterisation methods, leading to increases in the thermoelectric figure of merit and the observation of novel phenomena such as carrier filtering in nanocomposite samples. The difficulty in extracting good thermoelectric performance is at first glance surprising given the relative simplicity of the ideal crystal structure with only site occupancies and lattice parameter as crystallographic variables. However, the observed thermoelectric properties are found to depend sensitively on sample processing. Recent work has shown that prepared ingots can contain a range of inhomogeneities, including interstitials, nano- and micron sized Heusler inclusions and multiple half-Heusler phases. For this reason, the prepared materials are far more complex than initially appreciated and this may offer opportunities to enhance the thermoelectric figure of merit.

  8. Modelling of segmented high-performance thermoelectric generators with effects of thermal radiation, electrical and thermal contact resistances

    NASA Astrophysics Data System (ADS)

    Ouyang, Zhongliang; Li, Dawen

    2016-04-01

    In this study, segmented thermoelectric generators (TEGs) have been simulated with various state-of-the-art TE materials spanning a wide temperature range, from 300 K up to 1000 K. The results reveal that by combining the current best p-type TE materials, BiSbTe, MgAgSb, K-doped PbTeS and SnSe with the strongest n-type TE materials, Cu-Doped BiTeSe, AgPbSbTe and SiGe to build segmented legs, TE modules could achieve efficiencies of up to 17.0% and 20.9% at ΔT = 500 K and ΔT = 700 K, respectively, and a high output power densities of over 2.1 Watt cm-2 at the temperature difference of 700 K. Moreover, we demonstrate that successful segmentation requires a smooth change of compatibility factor s from one end of the TEG leg to the other, even if s values of two ends differ by more than a factor of 2. The influence of the thermal radiation, electrical and thermal contact effects have also been studied. Although considered potentially detrimental to the TEG performance, these effects, if well-regulated, do not prevent segmentation of the current best TE materials from being a prospective way to construct high performance TEGs with greatly enhanced efficiency and output power density.

  9. Modelling of segmented high-performance thermoelectric generators with effects of thermal radiation, electrical and thermal contact resistances

    PubMed Central

    Ouyang, Zhongliang; Li, Dawen

    2016-01-01

    In this study, segmented thermoelectric generators (TEGs) have been simulated with various state-of-the-art TE materials spanning a wide temperature range, from 300 K up to 1000 K. The results reveal that by combining the current best p-type TE materials, BiSbTe, MgAgSb, K-doped PbTeS and SnSe with the strongest n-type TE materials, Cu-Doped BiTeSe, AgPbSbTe and SiGe to build segmented legs, TE modules could achieve efficiencies of up to 17.0% and 20.9% at ΔT = 500 K and ΔT = 700 K, respectively, and a high output power densities of over 2.1 Watt cm−2 at the temperature difference of 700 K. Moreover, we demonstrate that successful segmentation requires a smooth change of compatibility factor s from one end of the TEG leg to the other, even if s values of two ends differ by more than a factor of 2. The influence of the thermal radiation, electrical and thermal contact effects have also been studied. Although considered potentially detrimental to the TEG performance, these effects, if well-regulated, do not prevent segmentation of the current best TE materials from being a prospective way to construct high performance TEGs with greatly enhanced efficiency and output power density. PMID:27052592

  10. Great enhancements in the thermoelectric power factor of BiSbTe nanostructured films with well-ordered interfaces

    NASA Astrophysics Data System (ADS)

    Chang, Hsiu-Cheng; Chen, Chun-Hua; Kuo, Yung-Kang

    2013-07-01

    An innovative concept of twin-enhanced thermoelectricity was proposed to fundamentally resolve the high electrical resistance while not degrading the phonon scattering of the thermoelectric nanoassemblies. Under this frame, a variety of highly oriented and twinned bismuth antimony telluride (BixSb2-xTe3) nanocrystals were successfully fabricated by a large-area pulsed-laser deposition (PLD) technique on insulated silicon substrates at various deposition temperatures. The significant presence of the nonbasal- and basal-plane twins across the hexagonal BiSbTe nanocrystals, which were experimentally and systematically observed for the first time, evidently contributes to the unusually high electrical conductivity of ~2700 S cm-1 and the power factor of ~25 μW cm-1 K-2 as well as the relatively low thermal conductivity of ~1.1 W m-1 K-1 found in these nanostructured films.An innovative concept of twin-enhanced thermoelectricity was proposed to fundamentally resolve the high electrical resistance while not degrading the phonon scattering of the thermoelectric nanoassemblies. Under this frame, a variety of highly oriented and twinned bismuth antimony telluride (BixSb2-xTe3) nanocrystals were successfully fabricated by a large-area pulsed-laser deposition (PLD) technique on insulated silicon substrates at various deposition temperatures. The significant presence of the nonbasal- and basal-plane twins across the hexagonal BiSbTe nanocrystals, which were experimentally and systematically observed for the first time, evidently contributes to the unusually high electrical conductivity of ~2700 S cm-1 and the power factor of ~25 μW cm-1 K-2 as well as the relatively low thermal conductivity of ~1.1 W m-1 K-1 found in these nanostructured films. Electronic supplementary information (ESI) available: Morphologies, XRD patterns, SEM compositions and room-temperature thermoelectric properties of the series of (015) oriented Bi0.4Sb1.6Te3 nanocolumns (Fig. S1-S3), (00l) oriented

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

    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.

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

    PubMed

    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. 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

  14. The influence of Thomson effect in the performance optimization of a two stage thermoelectric cooler

    NASA Astrophysics Data System (ADS)

    Kaushik, S. C.; Manikandan, S.

    2015-12-01

    The exoreversible and irreversible thermodynamic models of a two stage thermoelectric cooler (TTEC) considering Thomson effect in conjunction with Peltier, Joule and Fourier heat conduction effects have been investigated using exergy analysis. New expressions for the interstage temperature, optimum current for the maximum cooling power, energy and exergy efficiency conditions, energy efficiency and exergy efficiency of a TTEC are derived as well. The number of thermocouples in the first and second stages of a TTEC for the maximum cooling power, energy and exergy efficiency conditions are optimized. The results show that the exergy efficiency is lower than the energy efficiency e.g., in an irreversible TTEC with total 30 thermocouples, heat sink temperature (TH) of 300 K and heat source temperature (TC) of 280 K, the obtained maximum cooling power, maximum energy and exergy efficiency are 20.37 W, 0.7147 and 5.10% respectively. It has been found that the Thomson effect increases the cooling power and energy efficiency of the TTEC system e.g., in the exoreversible TTEC the cooling power and energy efficiency increased from 14.87 W to 16.36 W and from 0.4079 to 0.4998 respectively for ΔTC of 40 K when Thomson effect is considered. It has also been found that the heat transfer area at the hot side of an irreversible TTEC should be higher than the cold side for maximum performance operation. This study will help in the designing of the actual multistage thermoelectric cooling systems.

  15. Low thermal conductivity and improved thermoelectric performance of nanocrystalline silicon germanium films by sputtering.

    PubMed

    Taborda, J A Perez; Romero, J J; Abad, B; Muñoz-Rojo, M; Mello, A; Briones, F; Gonzalez, M S Martin

    2016-04-29

    Si x Ge1-x alloys are well-known thermoelectric materials with a high figure of merit at high temperatures. In this work, metal-induced crystallization (MIC) has been used to grow Si0.8Ge0.2 films that present improved thermoelectric performance (zT = 5.6 × 10(-4) at room temperature)--according to previously reported values on films--with a relatively large power factor (σ · S (2) = 16 μW · m(-1) · K(-2)). More importantly, a reduction in the thermal conductivity at room temperature (κ = 1.13 ± 0.12 W · m(-1) · K(-1)) compared to other Si-Ge films (∼3 W · m(-1) · K(-1)) has been found. Whereas the usual crystallization of amorphous SiGe (a-SiGe) is achieved at high temperatures and for long times, which triggers dopant loss, MIC reduces the crystallization temperature and the heating time. The associated dopant loss is thus avoided, resulting in a nanostructuration of the film. Using this method, we obtained Si0.8Ge0.2 films (grown by DC plasma sputtering) with appropriate compositional and structural properties. Different thermal treatments were tested in situ (by heating the sample inside the deposition chamber) and ex situ (annealed in an external furnace with controlled conditions). From the studies of the films by: x-ray diffraction (XRD), synchrotron radiation grazing incidence x-ray diffraction (SR-GIXRD), micro Raman, scanning electron microscopy (SEM), x-ray photoemission spectroscopy (XPS), Hall effect, Seebeck coefficient, electrical and thermal conductivity measurements, we observed that the in situ films at 500 °C presented the best zT values with no gold contamination.

  16. Low thermal conductivity and improved thermoelectric performance of nanocrystalline silicon germanium films by sputtering

    NASA Astrophysics Data System (ADS)

    Perez Taborda, J. A.; Romero, J. J.; Abad, B.; Muñoz-Rojo, M.; Mello, A.; Briones, F.; Gonzalez, M. S. Martin

    2016-04-01

    Si x Ge1-x alloys are well-known thermoelectric materials with a high figure of merit at high temperatures. In this work, metal-induced crystallization (MIC) has been used to grow Si0.8Ge0.2 films that present improved thermoelectric performance (zT = 5.6 × 10-4 at room temperature)—according to previously reported values on films—with a relatively large power factor (σ · S 2 = 16 μW · m-1 · K-2). More importantly, a reduction in the thermal conductivity at room temperature (κ = 1.13 ± 0.12 W · m-1 · K-1) compared to other Si-Ge films (˜3 W · m-1 · K-1) has been found. Whereas the usual crystallization of amorphous SiGe (a-SiGe) is achieved at high temperatures and for long times, which triggers dopant loss, MIC reduces the crystallization temperature and the heating time. The associated dopant loss is thus avoided, resulting in a nanostructuration of the film. Using this method, we obtained Si0.8Ge0.2 films (grown by DC plasma sputtering) with appropriate compositional and structural properties. Different thermal treatments were tested in situ (by heating the sample inside the deposition chamber) and ex situ (annealed in an external furnace with controlled conditions). From the studies of the films by: x-ray diffraction (XRD), synchrotron radiation grazing incidence x-ray diffraction (SR-GIXRD), micro Raman, scanning electron microscopy (SEM), x-ray photoemission spectroscopy (XPS), Hall effect, Seebeck coefficient, electrical and thermal conductivity measurements, we observed that the in situ films at 500 °C presented the best zT values with no gold contamination.

  17. A performance comparison of SiGe and skutterudite based segmented thermoelectric devices

    NASA Astrophysics Data System (ADS)

    El-Genk, Mohamed S.; Saber, Hamed H.; Caillat, Thierry

    2002-01-01

    For the past 25 years, unicouples made of Silicon Germanium alloys (Si0.8Ge0.2 and Si0.63Ge0.38) have been used in the majority of the spacecraft powered by Radioisotope Thermoelectric Generators (RTGs) to explore various planets of the solar system as well as the sun. These unicouples operate typically at hot and cold side temperatures of 1175-1273 K and 573 K, respectively, converting the heat produced in the General Purpose Heat Source (GPHS) modules to electricity at efficiencies <7%. Recently, Segmented Thermoelectric Unicouples (STUs) made of n-type Bi2Te3 and CoSb3-based alloys and p-type Bi2Te3 and CeFe4Sb12-based alloys have been developed and tested successfully with a demonstrated efficiency to date of ~10% and the potential for achieving 14-15% when operated at hot and cold side temperatures of 973 K and 300 K, respectively. This paper compares the performance of SiGe unicouples and skutterudite STUs, at same hot side temperature of 973 K and cold side temperatures of 300, 573, and 673 K, and the same total length and cross sectional dimensions of the p-leg. The area of the n-leg and the lengths of the segments of various materials in the STUs are determined based on maximizing either the electrical power density or the conversion efficiency. Results showed that replacing SiGe with skutterudite STUs in future radioisotope power systems (or even in conjunction with a space nuclear reactor and space probes), could increase the thermal to electric conversion efficiency at a heat source temperature of 973 K by ~40% to 198% for Tc=673 K and 300 K, respectively. This would reduce by more than half the mass of the 238PuO2 fuel needed and the radiator's surface area for rejecting the waste heat. .

  18. Low thermal conductivity and improved thermoelectric performance of nanocrystalline silicon germanium films by sputtering.

    PubMed

    Taborda, J A Perez; Romero, J J; Abad, B; Muñoz-Rojo, M; Mello, A; Briones, F; Gonzalez, M S Martin

    2016-04-29

    Si x Ge1-x alloys are well-known thermoelectric materials with a high figure of merit at high temperatures. In this work, metal-induced crystallization (MIC) has been used to grow Si0.8Ge0.2 films that present improved thermoelectric performance (zT = 5.6 × 10(-4) at room temperature)--according to previously reported values on films--with a relatively large power factor (σ · S (2) = 16 μW · m(-1) · K(-2)). More importantly, a reduction in the thermal conductivity at room temperature (κ = 1.13 ± 0.12 W · m(-1) · K(-1)) compared to other Si-Ge films (∼3 W · m(-1) · K(-1)) has been found. Whereas the usual crystallization of amorphous SiGe (a-SiGe) is achieved at high temperatures and for long times, which triggers dopant loss, MIC reduces the crystallization temperature and the heating time. The associated dopant loss is thus avoided, resulting in a nanostructuration of the film. Using this method, we obtained Si0.8Ge0.2 films (grown by DC plasma sputtering) with appropriate compositional and structural properties. Different thermal treatments were tested in situ (by heating the sample inside the deposition chamber) and ex situ (annealed in an external furnace with controlled conditions). From the studies of the films by: x-ray diffraction (XRD), synchrotron radiation grazing incidence x-ray diffraction (SR-GIXRD), micro Raman, scanning electron microscopy (SEM), x-ray photoemission spectroscopy (XPS), Hall effect, Seebeck coefficient, electrical and thermal conductivity measurements, we observed that the in situ films at 500 °C presented the best zT values with no gold contamination. PMID:26967792

  19. 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

  20. 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)

  1. Dopant's chemical coordination: a path for engineering high performance thermoelectric sodium cobaltate

    NASA Astrophysics Data System (ADS)

    Assadi, M. Hussein N.; Katayama-Yoshida, Hiroshi

    2014-03-01

    Engineered Na0.75CoO2 is considered a prime candidate to achieve high efficiency thermoelectric systems to generate electricity from waste heat. Our recent experiments on Mg doped Na0.75CoO2 demonstrated 50% enhancement in power factor at ambient. This motivated us to theoretically analyze the mechanisms behind simultaneous improvement of interdependent Seebeck coefficient and electrical conductivity. For this, we comprehensively studied the electronic and crystallographic structure of Na0.75CoO2 doped with 5 elements Mg, Sb, Zn, Ni and Eu. These elements represent wide variety of electronic configurations such as open d and f shells, closed d and s shells, combined with great variation in atomic mass. Systematic density functional calculations showed that the Ni and Zn were more stable when substituting Co with formation energy 2.35 eV, 2.08 eV. While Eu and Mg and Sb are more stable when it substitutes Na. In the case of Mg these results are consistent with Raman scattering measurement. This suggests that the doped Mg ions immobilize Na ions, reducing the resistivity by improving the mobility of carriers and thus enhancing the thermo-power. This work was supported by JSPS and Intersect.

  2. Advanced Thermoelectric Materials for Radioisotope Thermoelectric Generators

    NASA Technical Reports Server (NTRS)

    Caillat, Thierry; Hunag, C.-K.; Cheng, S.; Chi, S. C.; Gogna, P.; Paik, J.; Ravi, V.; Firdosy, S.; Ewell, R.

    2008-01-01

    This slide presentation reviews the progress and processes involved in creating new and advanced thermoelectric materials to be used in the design of new radioiootope thermoelectric generators (RTGs). In a program with Department of Energy, NASA is working to develop the next generation of RTGs, that will provide significant benefits for deep space missions that NASA will perform. These RTG's are planned to be capable of delivering up to 17% system efficiency and over 12 W/kg specific power. The thermoelectric materials being developed are an important step in this process.

  3. Optimization of the Mechanical and Electrical Performance of a Thermoelectric Module

    NASA Astrophysics Data System (ADS)

    Sarhadi, Ali; Bjørk, Rasmus; Pryds, Nini

    2015-11-01

    Finite-element simulation of a thermoelectric (TE) module was conducted to optimize its geometrical dimensions in terms of mechanical reliability and performance. The TE module consisted of bismuth telluride n- and p-type legs. The geometrical dimensions of the module, i.e., leg length and leg cross-sectional area, were varied, and the corresponding maximum thermal stress, output power, and efficiency of the module obtained. An optimal design for the module was then suggested based on minimizing the thermal stresses and maximizing the performance, i.e., power and efficiency. The optimal dimensions at maximum von Mises stress of 75 MPa were leg length of 2 mm to 2.5 mm and leg width of 1.5 mm to 2 mm, resulting in efficiency of 7.2%. Finally, the influence of solders, i.e., solder material between the leg, the interconnector, and the top ceramic layer, on the induced thermal stresses and module performance was investigated. The results revealed that the transition from elastic to plastic deformation in the solder decreased the induced thermal stresses significantly. Moreover, beyond the elastic limit, the stress magnitude was highly dependent on the magnitude and mechanism of plastic deformation in the module. The present study provides a basis for a unique and new optimization scheme for TE modules in terms of endurance and performance.

  4. 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.

  5. Research Update: Oxide thermoelectrics: Beyond the conventional design rules

    NASA Astrophysics Data System (ADS)

    Terasaki, Ichiro

    2016-10-01

    Materials' design for high-performance thermoelectric oxides is discussed. Since chemical stability at high temperature in air is a considerable advantage in oxides, we evaluate thermoelectric power factor in the high temperature limit. We show that highly disordered materials can be good thermoelectric materials at high temperatures, and the effects of strong correlation can further enhance the figure of merit by adding thermopower arising from the spin and orbital degrees of freedom. We also discuss the Kelvin formula as a promising expression for strongly correlated materials and show that the calculation based on the Kelvin formula can be directly compared with the cross-layer thermopower of layered materials.

  6. BiSb and spin-related thermoelectric phenomena

    NASA Astrophysics Data System (ADS)

    Heremans, Joseph P.; Jin, Hyungyu; Zheng, Yuanhua; Watzman, Sarah J.; Prakash, Arati

    2016-05-01

    This article reviews the factors limiting the figure of merit zT of conventional thermoelectrics especially at cryogenic temperatures and then highlights modern approaches used to increase zT below 200 K. Two type of materials are discussed. The first are BiSb alloys, relatively conventional thermoelectrics in which the zT is enhanced by using resonant levels. The second is the spin- Seebeck effect (SSE), a new solid-state energy conversion technology. Classical thermoelectric and SSE physics are combined to provide new concepts, like magnon-drag, in which we hope to increase the performance of solid-state coolers by exploiting the spin degree of freedom.

  7. Surfactant-Free Synthesis of Bi2Te3-Te Micro-Nano Heterostructure with Enhanced Thermoelectric Figure of Merit

    SciTech Connect

    Zhang, Yichi; Wang, Heng; Kraemer, Stephan; Shi, Yifeng; Zhang, Fan; Snedaker, Matt; Ding, Kunlun; Moskovits, Martin; Snyder, G. Jeffrey; Stucky, Galen D.

    2011-03-21

    An ideal thermoelectric material would be a semiconductor with high electrical conductivity and relatively low thermal conductivity: an “electron crystal, phonon glass”. Introducing nanoscale heterostructures into the bulk TE matrix is one way of achieving this intuitively anomalous electron/phonon transport behavior. The heterostructured interfaces are expected to play a significant role in phonon scattering to reduce thermal conductivity and in the energy-dependent scattering of electrical carriers to improve the Seebeck coefficient. A nanoparticle building block assembly approach is plausible to fabricate three-dimensional heterostructured materials on a bulk commercial scale. However, a key problem in applying this strategy is the possible negative impact on TE performance of organic residue from the nanoparticle capping ligands. Herein, we report a wet chemical, surfactant-free, low-temperature, and easily up-scalable strategy for the synthesis of nanoscale heterophase Bi₂Te₃-Te via a galvanic replacement reaction. The micro-nano heterostructured material is fabricated bottom-up, by mixing the heterophase with commercial Bi₂Te₃. This unique structure shows an enhanced zT value of ~0.4 at room temperature. This heterostructure has one of the highest figures of merit among bismuth telluride systems yet achieved by a wet chemical bottom-up assembly. In addition, it shows a 40% enhancement of the figure of merit over our lab-made material without nanoscale heterostructures. This enhancement is mainly due to the decrease in the thermal conductivity while maintaining the power factor. Overall, this cost-efficient and room-temperature synthesis methodology provides the potential for further improvement and large-scale thermoelectric applications.

  8. Enhanced thermoelectric power near the quantum phase transition in the itinerant-electron ferromagnet MnSi

    NASA Astrophysics Data System (ADS)

    Cheng, J.-G.; Zhou, F.; Zhou, J.-S.; Goodenough, J. B.; Sui, Y.

    2010-12-01

    The itinerant-electron ferromagnet MnSi is a well-known example that shows a transition from Fermi-liquid Δρ∝T2 to non-Fermi-liquid (NFL) Δρ∝T3/2 behavior when the spiral ferromagnetic transition Tc≈29K at ambient pressure is suppressed to zero by the application of hydrostatic pressures above Pc≈14.6kbar . Several experimental probes have been employed to reveal the intriguing properties near Pc . In this paper, we report the temperature dependence of thermoelectric power S(T) under hydrostatic pressures up to 20 kbar on a single crystal of MnSi. At pressures close to Pc , we observed at low temperatures an unusual enhancement of S(T) , which can be described well with the relationship S/T∝ln(1/T) , a formula that has been proposed to describe a system as a quantum critical point (QCP) is approached. The relationship has previously been observed in systems close to a magnetic QCP, for example, La1.6-xNd0.4SrxCuO4 (x=0.24) . The enhancement of thermoelectric power in MnSi occurs at a temperature above the NFL phase and over a broad pressure range around Pc .

  9. High-Performance Three-Stage Cascade Thermoelectric Devices with 20% Efficiency

    NASA Astrophysics Data System (ADS)

    Cook, B. A.; Chan, T. E.; Dezsi, G.; Thomas, P.; Koch, C. C.; Poon, J.; Tritt, T.; Venkatasubramanian, R.

    2015-06-01

    The use of advanced materials has resulted in a significant improvement in thermoelectric device conversion efficiency. Three-stage cascade devices were assembled, consisting of nano-bulk Bi2Te3-based materials on the cold side, PbTe and enhanced TAGS-85 [(AgSbTe2)15(GeTe)85] for the mid-stage, and half-Heusler alloys for the high-temperature top stage. In addition, an area aspect ratio optimization process was applied in order to account for asymmetric thermal transport down the individual n- and p-legs. The n- and p-type chalcogenide alloy materials were prepared by high-energy mechanical ball-milling and/or cryogenic ball-milling of elementary powders, with subsequent consolidation by high-pressure uniaxial hot-pressing. The low-temperature stage materials, nano-bulk Bi2Te3- x Sb x and Bi2Te3- x Se x , exhibit a unique mixture of nanoscale features that leads to an enhanced Seebeck coefficient and reduced lattice thermal conductivity, thereby achieving an average ZT of ~1.26 and ~1.7 in the 27°C to 100°C range for the n-type and p-type materials, respectively. Also, the addition of small amounts of selected rare earth elements has been shown to improve the ZT of TAGS-85 by 25%, compared with conventional or neat TAGS-85, resulting in a ZT = 1.5 at 400°C. The incorporation of these improved materials resulted in a peak device conversion efficiency of ~20% at a temperature difference of 750°C when corrected for radiation heat losses and thermal conduction losses through the lead wires. These high-efficiency results were shown to be reproducible across multiple cascade devices.

  10. Thermoelectric properties of armchair and zigzag silicene nanoribbons.

    PubMed

    Pan, L; Liu, H J; Tan, X J; Lv, H Y; Shi, J; Tang, X F; Zheng, G

    2012-10-21

    Using the nonequilibrium Green's function method and nonequilibrium molecular dynamics simulations, we discuss the possibility of using silicene nanoribbons (SiNRs) as high performance thermoelectric materials. It is found that SiNRs are structurally stable if the edge atoms are passivated by hydrogen, and those with armchair edges usually exhibit much better thermoelectric performance than their zigzag counterparts. The room temperature ZT value of armchair SiNRs shows a width-dependent oscillating decay, while it decreases slowly with increasing ribbon width for the zigzag SiNRs. In addition, there is a strong temperature dependence of the thermoelectric performance of these SiNRs. Our theoretical calculations indicate that by optimizing the doping level and applied temperature, the ZT value of SiNRs could be enhanced to as high as 4.9 which suggests their very appealing thermoelectric applications.

  11. A synthetic approach for enhanced thermoelectric properties of PEDOT:PSS bulk composites

    NASA Astrophysics Data System (ADS)

    Wei, Kaya; Stedman, Troy; Ge, Zhen-Hua; Woods, Lilia M.; Nolas, George S.

    2015-10-01

    The thermoelectric properties of PEDOT:PSS/Bi0.5Sb1.5Te3 polymer/inorganic bulk composites with different Bi0.5Sb1.5Te3 content were investigated. The composites were prepared at various concentrations of Bi0.5Sb1.5Te3 by a solution-phase process before grinding to fine powders in liquid N2 for hot pressing into bulk polymer composite materials. The measured transport properties are well described within a theoretical model for effective media involving a tunneling mechanism induced by thermal voltage fluctuations. Our results present a strategy for the preparation of bulk polymer composites and demonstrate an avenue for optimization of the thermoelectric properties of PEDOT:PSS/Bi0.5Sb1.5Te3 bulk composites.

  12. 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.; Li, W.; Wu, L.; Tan, Q.; Pei, Y.; Huang, L.; Li, J. -F.; Zhu, Y.; et al

    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) observationsmore » 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

  13. Superior thermoelectric performance in PbTe-PbS pseudo-binary. Extremely low thermal conductivity and modulated carrier concentration

    SciTech Connect

    Wu, D.; Zhao, L. -D.; Tong, X.; Li, W.; Wu, L.; Tan, Q.; Pei, Y.; Huang, L.; Li, J. -F.; Zhu, Y.; Kanatzidis, M. G.; He, J.

    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) 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.

  14. High thermoelectric performance from optimization of hole-doped CuInTe2.

    PubMed

    Zhou, Gang; Wang, Dong

    2016-02-17

    We investigated the electronic structure, lattice dynamics and thermoelectric transport properties of CuInTe2 based on first-principles calculations. From the analysis of density of states and partial charge density, it can be expected that p-doping at the In-site or n-doping at the Cu-site will barely modify the electronic states near the valence or conduction band edge but increase the carrier concentration to achieve the highest thermoelectric efficiency. Lattice dynamics calculations suggest that the thermal conductivity of CuInTe2 can be effectively reduced by introducing structural defects at Cu, In and Te sites. p-type CuInTe2 possesses better thermoelectric properties as compared to the n-type one, which mainly originates from the steeper density of states resulting from nearly degenerate valence bands near the band edge. The temperature dependence of the thermoelectric transport properties of p-type CuInTe2 at different carrier concentrations was studied in detail, which is found to be in good agreement with the experimental data. Our results of calculation showed that p-type CuInTe2 can achieve an upper-limit figure of merit value of 1.72 at 850 K and are promising thermoelectric materials for waste heat recovery at medium temperatures.

  15. High thermoelectric performance from optimization of hole-doped CuInTe2.

    PubMed

    Zhou, Gang; Wang, Dong

    2016-02-17

    We investigated the electronic structure, lattice dynamics and thermoelectric transport properties of CuInTe2 based on first-principles calculations. From the analysis of density of states and partial charge density, it can be expected that p-doping at the In-site or n-doping at the Cu-site will barely modify the electronic states near the valence or conduction band edge but increase the carrier concentration to achieve the highest thermoelectric efficiency. Lattice dynamics calculations suggest that the thermal conductivity of CuInTe2 can be effectively reduced by introducing structural defects at Cu, In and Te sites. p-type CuInTe2 possesses better thermoelectric properties as compared to the n-type one, which mainly originates from the steeper density of states resulting from nearly degenerate valence bands near the band edge. The temperature dependence of the thermoelectric transport properties of p-type CuInTe2 at different carrier concentrations was studied in detail, which is found to be in good agreement with the experimental data. Our results of calculation showed that p-type CuInTe2 can achieve an upper-limit figure of merit value of 1.72 at 850 K and are promising thermoelectric materials for waste heat recovery at medium temperatures. PMID:26593866

  16. Improved thermoelectric performance of n-type Ca and Ca-Ce filled skutterudites

    NASA Astrophysics Data System (ADS)

    Thompson, Daniel R.; Liu, Chang; Ellison, Nicole D.; Salvador, James R.; Meyer, Martin S.; Haddad, Daad B.; Wang, Hsin; Cai, W.

    2014-12-01

    Thermoelectric (TE) technology for use in automotive waste heat recovery is being advanced by General Motors with support from the US Department of Energy. Skutterudites are a very promising material for this application of TE technology due to their superior mechanical properties and good TE performance. Double-filled YbxBayCo4Sb12 with ZT values around 1.1 at 750 K are the best performing n-type skutterudites produced on a large scale using an economically viable approach of melt spinning (MS) in conjunction with spark plasma sintering (SPS). Another economical production method on the tons scale, the melt quench annealing (MQA) technique, has been recently claimed by Treibacher Industrie AG, further information is available [G. Rogl et al., Acta Mater. 76, 434-448 (2014)]. A possible hurdle to commercial implementation of these materials is the use of rare earths as the fillers to reduce thermal conductivity and improve the electrical transport properties. It will be shown herein that skutterudites double-filled with Ca and Ce, both of which are lower-cost fillers, display markedly different TE properties depending on whether they are produced by MQA or MS + SPS synthesis techniques. Ca and Ce double-filled skutterudites prepared by MS + SPS have TE properties that are superior to the same compositions prepared by MQA and that are comparable to the best performing Yb and Ba filled materials. Furthermore, the results of this study suggest that the unusually poor transport properties of MQA Ca-filled skutterudites can be ascribed to deleterious secondary phases, which is contrary to reports in the literature attempting to explain these irregularities via band structure features.

  17. Improved thermoelectric performance of n-type Ca and Ca-Ce filled skutterudites

    SciTech Connect

    Thompson, Daniel R.; Liu, Chang; Ellison, Nicole D.; Salvador, James R.; Meyer, Martin S.; Haddad, Daad B.; Wang, Hsin; Cai, W.

    2014-12-28

    Thermoelectric (TE) technology for use in automotive waste heat recovery is being advanced by General Motors with support from the US Department of Energy. Skutterudites are a very promising material for this application of TE technology due to their superior mechanical properties and good TE performance. Double-filled YbxBayCo4Sb12 with ZT values around 1.1 at 750K are the best performing n-type skutterudites produced on a large scale using an economically viable approach of melt spinning (MS) in conjunction with spark plasma sintering (SPS). Another economical production method on the tons scale, the melt quench annealing (MQA) technique, has been recently claimed by Treibacher Industrie AG, further information is available [G. Rogl et al., Acta Mater. 76, 434-448 (2014)]. A possible hurdle to commercial implementation of these materials is the use of rare earths as the fillers to reduce thermal conductivity and improve the electrical transport properties. It will be shown herein that skutterudites double-filled with Ca and Ce, both of which are lower-cost fillers, display markedly different TE properties depending on whether they are produced by MQA or MS + SPS synthesis techniques. Finally, Ca and Ce double-filled skutterudites prepared by MS + SPS have TE properties that are superior to the same compositions prepared by MQA and that are comparable to the best performing Yb and Ba filled materials. Furthermore, the results of this study suggest that the unusually poor transport properties of MQA Ca-filled skutterudites can be ascribed to deleterious secondary phases, which is contrary to reports in the literature attempting to explain these irregularities via band structure features.

  18. Improved thermoelectric performance of n-type Ca and Ca-Ce filled skutterudites

    DOE PAGES

    Thompson, Daniel R.; Liu, Chang; Ellison, Nicole D.; Salvador, James R.; Meyer, Martin S.; Haddad, Daad B.; Wang, Hsin; Cai, W.

    2014-12-28

    Thermoelectric (TE) technology for use in automotive waste heat recovery is being advanced by General Motors with support from the US Department of Energy. Skutterudites are a very promising material for this application of TE technology due to their superior mechanical properties and good TE performance. Double-filled YbxBayCo4Sb12 with ZT values around 1.1 at 750K are the best performing n-type skutterudites produced on a large scale using an economically viable approach of melt spinning (MS) in conjunction with spark plasma sintering (SPS). Another economical production method on the tons scale, the melt quench annealing (MQA) technique, has been recently claimedmore » by Treibacher Industrie AG, further information is available [G. Rogl et al., Acta Mater. 76, 434-448 (2014)]. A possible hurdle to commercial implementation of these materials is the use of rare earths as the fillers to reduce thermal conductivity and improve the electrical transport properties. It will be shown herein that skutterudites double-filled with Ca and Ce, both of which are lower-cost fillers, display markedly different TE properties depending on whether they are produced by MQA or MS + SPS synthesis techniques. Finally, Ca and Ce double-filled skutterudites prepared by MS + SPS have TE properties that are superior to the same compositions prepared by MQA and that are comparable to the best performing Yb and Ba filled materials. Furthermore, the results of this study suggest that the unusually poor transport properties of MQA Ca-filled skutterudites can be ascribed to deleterious secondary phases, which is contrary to reports in the literature attempting to explain these irregularities via band structure features.« less

  19. Improved thermoelectric performance of n-type Ca and Ca-Ce filled skutterudites

    SciTech Connect

    Thompson, Daniel R.; Liu, Chang; Ellison, Nicole D.; Salvador, James R.; Meyer, Martin S.; Haddad, Daad B.; Wang, Hsin; Cai, W.

    2014-12-28

    Thermoelectric (TE) technology for use in automotive waste heat recovery is being advanced by General Motors with support from the US Department of Energy. Skutterudites are a very promising material for this application of TE technology due to their superior mechanical properties and good TE performance. Double-filled Yb{sub x}Ba{sub y}Co{sub 4}Sb{sub 12} with ZT values around 1.1 at 750 K are the best performing n-type skutterudites produced on a large scale using an economically viable approach of melt spinning (MS) in conjunction with spark plasma sintering (SPS). Another economical production method on the tons scale, the melt quench annealing (MQA) technique, has been recently claimed by Treibacher Industrie AG, further information is available [G. Rogl et al., Acta Mater. 76, 434–448 (2014)]. A possible hurdle to commercial implementation of these materials is the use of rare earths as the fillers to reduce thermal conductivity and improve the electrical transport properties. It will be shown herein that skutterudites double-filled with Ca and Ce, both of which are lower-cost fillers, display markedly different TE properties depending on whether they are produced by MQA or MS + SPS synthesis techniques. Ca and Ce double-filled skutterudites prepared by MS + SPS have TE properties that are superior to the same compositions prepared by MQA and that are comparable to the best performing Yb and Ba filled materials. Furthermore, the results of this study suggest that the unusually poor transport properties of MQA Ca-filled skutterudites can be ascribed to deleterious secondary phases, which is contrary to reports in the literature attempting to explain these irregularities via band structure features.

  20. Foldable Thermoelectric Materials: Improvement of the Thermoelectric Performance of Directly Spun CNT Webs by Individual Control of Electrical and Thermal Conductivity.

    PubMed

    An, Cheng Jin; Kang, Young Hun; Lee, A-Young; Jang, Kwang-Suk; Jeong, Youngjin; Cho, Song Yun

    2016-08-31

    We suggest the fabrication of foldable thermoelectric (TE) materials by embedding conducting polymers into Au-doped CNT webs. The CNT bundles, which are interconnected by a direct spinning method to form 3D networks without interfacial contact resistance, provide both high electrical conductivity and high carrier mobility. The ZT value of the spun CNT web is significantly enhanced through two simple processes. Decorating the porous CNT webs with Au nanoparticles increases the electrical conductivity, resulting in an optimal ZT of 0.163, which represents a more than 2-fold improvement compared to the ZT of pristine CNT webs (0.079). After decoration, polyaniline (PANI) is integrated into the Au-doped CNT webs both to improve the Seebeck coefficient by an energy-filtering effect and to decrease the thermal conductivity by the phonon-scattering effect. This leads to a ZT of 0.203, which is one of the highest ZT values reported for organic TE materials. Moreover, Au-doped CNT/PANI web is ultralightweight, free-standing, thermally stable, and mechanically robust, which makes it a viable candidate for a hybrid TE conversion device for wearable electronics. When a 20 K temperature gradient is applied to the TE module consisting of seven p-n couples, 1.74 μW of power is generated. PMID:27501827

  1. Foldable Thermoelectric Materials: Improvement of the Thermoelectric Performance of Directly Spun CNT Webs by Individual Control of Electrical and Thermal Conductivity.

    PubMed

    An, Cheng Jin; Kang, Young Hun; Lee, A-Young; Jang, Kwang-Suk; Jeong, Youngjin; Cho, Song Yun

    2016-08-31

    We suggest the fabrication of foldable thermoelectric (TE) materials by embedding conducting polymers into Au-doped CNT webs. The CNT bundles, which are interconnected by a direct spinning method to form 3D networks without interfacial contact resistance, provide both high electrical conductivity and high carrier mobility. The ZT value of the spun CNT web is significantly enhanced through two simple processes. Decorating the porous CNT webs with Au nanoparticles increases the electrical conductivity, resulting in an optimal ZT of 0.163, which represents a more than 2-fold improvement compared to the ZT of pristine CNT webs (0.079). After decoration, polyaniline (PANI) is integrated into the Au-doped CNT webs both to improve the Seebeck coefficient by an energy-filtering effect and to decrease the thermal conductivity by the phonon-scattering effect. This leads to a ZT of 0.203, which is one of the highest ZT values reported for organic TE materials. Moreover, Au-doped CNT/PANI web is ultralightweight, free-standing, thermally stable, and mechanically robust, which makes it a viable candidate for a hybrid TE conversion device for wearable electronics. When a 20 K temperature gradient is applied to the TE module consisting of seven p-n couples, 1.74 μW of power is generated.

  2. Weak electron–phonon coupling contributing to high thermoelectric performance in n-type PbSe

    PubMed Central

    Wang, Heng; Pei, Yanzhong; LaLonde, Aaron D.; Snyder, G. Jeffrey

    2012-01-01

    PbSe is a surprisingly good thermoelectric material due, in part, to its low thermal conductivity that had been overestimated in earlier measurements. The thermoelectric figure of merit, zT, can exceed 1 at high temperatures in both p-type and n-type PbSe, similar to that found in PbTe. While the p-type lead chalcogenides (PbSe and PbTe) benefit from the high valley degeneracy (12 or more at high temperature) of the valence band, the n-type versions are limited to a valley degeneracy of 4 in the conduction band. Yet the n-type lead chalcogenides achieve a zT nearly as high as the p-type lead chalcogenides. This effect can be attributed to the weaker electron–phonon coupling (lower deformation potential coefficient) in the conduction band as compared with that in the valence band, which leads to higher mobility of electrons compared to that of holes. This study of PbSe illustrates the importance of the deformation potential coefficient of the charge-carrying band as one of several key parameters to consider for band structure engineering and the search for high performance thermoelectric materials. PMID:22615358

  3. 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.

  4. Enhancement of the thermoelectric power by electronic correlations in bad metals: A study of the Kelvin formula

    NASA Astrophysics Data System (ADS)

    Kokalj, J.; McKenzie, Ross H.

    2015-03-01

    In many strongly correlated electron metals the thermoelectric power has a nonmonotonic temperature dependence and values that are orders of magnitude larger than for elemental metals. Inspired by Kelvin, Peterson and Shastry derived a particularly simple expression for the thermopower in terms of the temperature dependence of the chemical potential, now known as the Kelvin formula. We consider a Hubbard model on an anisotropic triangular lattice at half filling, a minimal effective Hamiltonian for several classes of organic charge transfer salts. The finite temperature Lanczos method is used to calculate the temperature dependence of the thermopower using the Kelvin formula. We find that electronic correlations significantly enhance the magnitude of the thermopower and lead to a nonmonotonic temperature dependence. The latter reflects a crossover with increasing temperature from a Fermi liquid to a bad metal. Although, the Kelvin formula gives a semiquantitative description of some experimental results it cannot describe the directional dependence of the sign of the thermopower in some materials.

  5. Enhanced thermoelectric properties of n-type NbCoSn half-Heusler by improving phase purity

    NASA Astrophysics Data System (ADS)

    He, Ran; Huang, Lihong; Wang, Yumei; Samsonidze, Georgy; Kozinsky, Boris; Zhang, Qinyong; Ren, Zhifeng

    2016-10-01

    Here 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 NbCoSn0.9Sb0.1. 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.

  6. Photo-induced enhancement of the power factor of Cu2S thermoelectric films

    NASA Astrophysics Data System (ADS)

    Lv, Yanhong; Chen, Jikun; Zheng, Ren-Kui; Song, Junqiang; Zhang, Tiansong; Li, Xiaomin; Shi, Xun; Chen, Lidong

    2015-11-01

    Element doping is commonly used to adjust the carrier concentrations in semiconductors such as thermoelectric materials. However, the doping process unavoidably brings in defects or distortions in crystal lattices, which further strongly affects the physical properties of the materials. In this work, high energy photons have been used to activate the carriers in Cu2S thermoelectric films. As a result, the carrier concentrations, and the respective electrical conductivity as well as Seebeck coefficient are further changed. The photon-induced electrical transport properties are further analyzed utilizing a Parallel circuit model. Due to the realization of optimized carrier concentrations by photon activation, the power factor of Cu2S film is improved more than 900 times as compared with the dark data. As compared to the traditional doping process, the approach using photon activation can realize the tuning of carrier concentrations without affecting crystal lattice. This method provides an opportunity to investigate the intrinsic physical properties of semiconductor materials without involving traditional element doping process that usually brings in additional lattice defects or distortions.

  7. Enhanced thermoelectric figure of merit of p-type half-Heuslers.

    PubMed

    Yan, Xiao; Joshi, Giri; Liu, Weishu; Lan, Yucheng; Wang, Hui; Lee, Sangyeop; Simonson, J W; Poon, S J; Tritt, T M; Chen, Gang; Ren, Z F

    2011-02-01

    Half-Heuslers would be important thermoelectric materials due to their high temperature stability and abundance if their dimensionless thermoelectric figure of merit (ZT) could be made high enough. The highest peak ZT of a p-type half-Heusler has been so far reported about 0.5 due to the high thermal conductivity. Through a nanocomposite approach using ball milling and hot pressing, we have achieved a peak ZT of 0.8 at 700 °C, which is about 60% higher than the best reported 0.5 and might be good enough for consideration for waste heat recovery in car exhaust systems. The improvement comes from a simultaneous increase in Seebeck coefficient and a significant decrease in thermal conductivity due to nanostructures. The samples were made by first forming alloyed ingots using arc melting and then creating nanopowders by ball milling the ingots and finally obtaining dense bulk by hot pressing. Further improvement in ZT is expected when average grain sizes are made smaller than 100 nm.

  8. Photo-induced enhancement of the power factor of Cu2S thermoelectric films

    PubMed Central

    Lv, Yanhong; Chen, Jikun; Zheng, Ren-Kui; Song, Junqiang; Zhang, Tiansong; Li, Xiaomin; Shi, Xun; Chen, Lidong

    2015-01-01

    Element doping is commonly used to adjust the carrier concentrations in semiconductors such as thermoelectric materials. However, the doping process unavoidably brings in defects or distortions in crystal lattices, which further strongly affects the physical properties of the materials. In this work, high energy photons have been used to activate the carriers in Cu2S thermoelectric films. As a result, the carrier concentrations, and the respective electrical conductivity as well as Seebeck coefficient are further changed. The photon-induced electrical transport properties are further analyzed utilizing a Parallel circuit model. Due to the realization of optimized carrier concentrations by photon activation, the power factor of Cu2S film is improved more than 900 times as compared with the dark data. As compared to the traditional doping process, the approach using photon activation can realize the tuning of carrier concentrations without affecting crystal lattice. This method provides an opportunity to investigate the intrinsic physical properties of semiconductor materials without involving traditional element doping process that usually brings in additional lattice defects or distortions. PMID:26573407

  9. Photo-induced enhancement of the power factor of Cu2S thermoelectric films.

    PubMed

    Lv, Yanhong; Chen, Jikun; Zheng, Ren-Kui; Song, Junqiang; Zhang, Tiansong; Li, Xiaomin; Shi, Xun; Chen, Lidong

    2015-01-01

    Element doping is commonly used to adjust the carrier concentrations in semiconductors such as thermoelectric materials. However, the doping process unavoidably brings in defects or distortions in crystal lattices, which further strongly affects the physical properties of the materials. In this work, high energy photons have been used to activate the carriers in Cu2S thermoelectric films. As a result, the carrier concentrations, and the respective electrical conductivity as well as Seebeck coefficient are further changed. The photon-induced electrical transport properties are further analyzed utilizing a Parallel circuit model. Due to the realization of optimized carrier concentrations by photon activation, the power factor of Cu2S film is improved more than 900 times as compared with the dark data. As compared to the traditional doping process, the approach using photon activation can realize the tuning of carrier concentrations without affecting crystal lattice. This method provides an opportunity to investigate the intrinsic physical properties of semiconductor materials without involving traditional element doping process that usually brings in additional lattice defects or distortions. PMID:26573407

  10. Analysis of Phase Separation in High Performance PbTe–PbS Thermoelectric Materials

    SciTech Connect

    Girard, Steven N.; Schmidt-Rohr, Klaus; Chasapis, Thomas C.; Hatzikraniotis, Euripides; Njegic, B.; Levin, E. M.; Rawal, A.; Paraskevopoulos, Konstantios M.; Kanatzidis, Mercouri G.

    2013-02-11

    Phase immiscibility in PbTe–based thermoelectric materials is an effective means of top-down synthesis of nanostructured composites exhibiting low lattice thermal conductivities. PbTe1-x Sx thermoelectric materials can be synthesized as metastable solid solution alloys through rapid quenching. Subsequent post-annealing induces phase separation at the nanometer scale, producing nanostructures that increase phonon scattering and reduce lattice thermal conductivity. However, there has yet to be any study investigating in detail the local chemical structure of both the solid solution and nanostructured variants of this material system. Herein, quenched and annealed (i.e., solid solution and phase-separated) samples of PbTe–PbS are analyzed by in situ high-resolution synchrotron powder X-ray diffraction, solid-state 125Te nuclear magnetic resonance (NMR), and infrared (IR) spectroscopy analysis. For high concentrations of PbS in PbTe, e.g., x >16%, NMR and IR analyses reveal that rapidly quenched samples exhibit incipient phase separation that is not detected by state-of-the-art synchrotron X-ray diffraction, providing an example of a PbTe thermoelectric “alloy” that is in fact phase inhomogeneous. Thermally-induced PbS phase separation in PbTe–PbS occurs close to 200 °C for all compositions studied, and the solubility of the PbS phase in PbTe at elevated temperatures >500 °C is reported. The findings of this study suggest that there may be a large number of thermoelectric alloy systems that are phase inhomogeneous or nanostructured despite adherence to Vegard's Law of alloys, highlighting the importance of careful chemical characterization to differentiate between thermoelectric alloys and composites.

  11. 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.

  12. 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. PMID:26332260

  13. Thermal Performance of a Multi-Evaporator Loop Heat Pipe with Thermal Masses and Thermoelectric Coolers

    NASA Technical Reports Server (NTRS)

    Ku, Jen-Tung; Ottenstein, Laura; Birur, Gajanana

    2004-01-01

    This paper describes thermal performance of a loop heat pipe (LHP) with two evaporators and two condensers in ambient testing. Each evaporator has an outer diameter of 15mm and a length of 76mm, and has an integral compensation chamber (CC). An aluminum mass of 500 grams is attached to each evaporator to simulate the instrument mass. A thermoelectric cooler (TEC) is installed on each CC to provide heating as well as cooling for CC temperature control. A flow regulator is installed in the condenser section to prevent vapor from going back to the evaporators in the event that one of the condensers is fully utilized. Ammonia was used as the working fluid. Tests conducted included start-up, power cycle, heat load sharing, sink temperature cycle, operating temperature control with TECs, and capillary limit tests. Experimental data showed that the loop could start with a heat load of less than 10W even with added thermal masses. The loop operated stably with even and uneven evaporator heat loads, and even and uneven condenser sink temperatures. The operating temperature could be controlled within +/- 0.5K of the set point temperature using either or both TECs, and the required TEC control heater power was less than 2W under most test conditions. Heat load sharing between the two evaporators was also successfully demonstrated. The loop had a heat transport capability of 120W to 140W, and could recover from a dry-out when the heat load was reduced. The 500-gram aluminum mass on each evaporator had a negligible effect on the loop operation. Existing LHPs servicing orbiting spacecraft have a single evaporator with an outer diameter of about 25mm. Important performance characteristics demonstrated by this LHP included: 1) Operation of an LHP with 15mm diameter evaporators; 2) Robustness and reliability of an LHP with multiple evaporators and multiple condensers under various test conditions; 3) Heat load sharing among LHP evaporators; 4) Effectiveness of TECs in controlling

  14. Thermoelectric-enhanced, liquid-based cooling of a multi-component electronic system

    SciTech Connect

    Chainer, Timothy J; Graybill, David P; Iyengar, Madhusudan K; Kamath, Vinod; Kochuparambil, Bejoy J; Schmidt, Roger R; Steinke, Mark E

    2015-05-12

    Apparatus and method are provided for facilitating cooling of an electronic component. The apparatus includes a liquid-cooled structure, a thermal conduction path coupling the electronic component and the liquid-cooled structure, a coolant loop in fluid communication with a coolant-carrying channel of the liquid-cooled structure, and an outdoor-air-cooled heat exchange unit coupled to facilitate heat transfer from the liquid-cooled structure via, at least in part, the coolant loop. The thermoelectric array facilitates transfer of heat from the electronic component to the liquid-cooled structure, and the heat exchange unit cools coolant passing through the coolant loop by dissipating heat from the coolant to outdoor ambient air. In one implementation, temperature of coolant entering the liquid-cooled structure is greater than temperature of the outdoor ambient air to which heat is dissipated.

  15. Thermoelectric-enhanced, liquid-based cooling of a multi-component electronic system

    SciTech Connect

    Chainer, Timothy J; Graybill, David P; Iyengar, Madhusudan K; Kamath, Vinod; Kochuparambil, Bejoy J; Schmidt, Roger R; Steinke, Mark E

    2015-11-10

    Methods are provided for facilitating cooling of an electronic component. The methods include providing: a liquid-cooled structure, a thermal conduction path coupling the electronic component and the liquid-cooled structure, a coolant loop in fluid communication with a coolant-carrying channel of the liquid-cooled structure, and an outdoor-air-cooled heat exchange unit coupled to facilitate heat transfer from the liquid-cooled structure via, at least in part, the coolant loop. The thermoelectric array facilitates transfer of heat from the electronic component to the liquid-cooled structure, and the heat exchange unit cools coolant passing through the coolant loop by dissipating heat from the coolant to outdoor ambient air. In one implementation, temperature of coolant entering the liquid-cooled structure is greater than temperature of the outdoor ambient air to which heat is dissipated.

  16. Enhancement of the thermoelectric figure of merit in a quantum dot due to external ac field

    NASA Astrophysics Data System (ADS)

    Chen, Qiao; Wang, Zhi-yong; Xie, Zhong-Xiang

    2013-08-01

    We investigate the figure of merit of a quantum dot (QD) system irradiated with an external microwave filed by nonequilibrium Green's function (NGF) technique. Results show that the frequency of microwave field influence the figure of merit ZT significantly. At low temperature, a sharp peak can be observed in the figure of merit ZT as the frequency of ac field increases. As the frequency varies, several zero points and resonant peaks emerge in the figure of merit ZT. By adjusting the frequency of the microwave field, we can obtain high ZT. The figure of merit ZT increases with the decreasing of linewidth function Γ. In addition, Wiedemann-Franz law does not hold, particularly in the low frequency region due to multi-photon emission and absorption. Some novel thermoelectric properties are also found in two-level QD system.

  17. Enhanced Thermoelectric Properties of W- and Fe-Substituted MnSi γ

    NASA Astrophysics Data System (ADS)

    Ghodke, Swapnil; Hiroishi, Naoya; Yamamoto, Akio; Ikuta, Hiroshi; Matsunami, Masaharu; Takeuchi, Tsunehiro

    2016-06-01

    We have investigated the effect of heavy-element (W) substitution on the thermoelectric properties of higher manganese silicide (HMS). Samples were prepared by arc melting followed by liquid quenching, where the latter assisted in achieving higher solubility for tungsten. We observed that Mn34.6W1.8Si63.6 was a p-type material, whereas simultaneous substitution of 12 at.% Fe made the higher manganese silicide an n-type material. The optimal carrier concentration was obtained by simultaneous substitution of Fe and W for Mn atoms. Although the samples were metastable, we successfully obtained bulk samples by a low-temperature (970 K), high-pressure (>100 MPa), long-duration sintering process. The lattice thermal conductivity was effectively reduced by W substitution, and the ZT value was improved to above 0.5 for both n- and p-type samples.

  18. Enhanced Thermoelectric Properties of W- and Fe-Substituted MnSi γ

    NASA Astrophysics Data System (ADS)

    Ghodke, Swapnil; Hiroishi, Naoya; Yamamoto, Akio; Ikuta, Hiroshi; Matsunami, Masaharu; Takeuchi, Tsunehiro

    2016-10-01

    We have investigated the effect of heavy-element (W) substitution on the thermoelectric properties of higher manganese silicide (HMS). Samples were prepared by arc melting followed by liquid quenching, where the latter assisted in achieving higher solubility for tungsten. We observed that Mn34.6W1.8Si63.6 was a p-type material, whereas simultaneous substitution of 12 at.% Fe made the higher manganese silicide an n-type material. The optimal carrier concentration was obtained by simultaneous substitution of Fe and W for Mn atoms. Although the samples were metastable, we successfully obtained bulk samples by a low-temperature (970 K), high-pressure (>100 MPa), long-duration sintering process. The lattice thermal conductivity was effectively reduced by W substitution, and the ZT value was improved to above 0.5 for both n- and p-type samples.

  19. 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.

  20. Performance of the 1 kW thermoelectric generator for diesel engines

    SciTech Connect

    Bass, J.C.; Elsner, N.B.; Leavitt, F.A.

    1994-08-10

    Hi-Z Technology, Inc. (Hi-Z) has been developing a 1 kW thermoelectric generator for class eight Diesel truck engines under U.S. Department of Energy and California Energy Commission funding since 1992. The purpose of this generator is to replace the currently used shaft-driven alternator by converting part of the waste heat in the engine`s exhaust directly to electricity. The preliminary design of this generator was reported at the 1992 meeting of the XI-ICT in Arlington, Texas. This paper will report on the final mechanical, thermal and thermoelectric design of this generator. The generator uses seventy-two of Hi-Z`s 13 Watt bismuth-telluride thermoelectric modules for energy conversion. The number of modules and their arrangement has remained constant through the program. The 1 kW generator was tested on several engines during the development process. Many of the design features were changed during this development as more information was obtained. We have only recently reached our design goal of 1 kW output. The output parameters of the generator are reported. {copyright} {ital 1995} {ital American} {ital Institute} {ital of} {ital Physics}.

  1. Nonequilibrium Thermoelectrics: Low-Cost, High-Performance Materials for Cooling and Power Generation

    SciTech Connect

    Li, Q.

    2011-05-18

    Thermoelectric materials can be made into coolers (TECs) that use electricity to develop a temperature difference, cooling something, or generators (TEGs) that convert heat directly to electricity. One application of TEGs is to place them in a waste heat stream to recuperate some of the power being lost and putting it to use more profitably. To be effective thermoelectrics, however, materials must have both high electrical conductivity and low thermal conductivity, a combination rarely found in nature. Materials selection and processing has led to the development of several systems with a figure of merit, ZT, of nearly unity. By using non-equilibrium techniques, we have fabricated higher efficiency thermoelectric materials. The process involves creating an amorphous material through melt spinning and then sintering it with either spark plasma or a hot press for as little as two minutes. This results in a 100% dense material with an extremely fine grain structure. The grain boundaries appear to retard phonons resulting in a reduced thermal conductivity while the electrons move through the material relatively unchecked. The techniques used are low-cost and scaleable to support industrial manufacturing.

  2. Improved Thermoelectric Behavior of Nanotube-Filled Polymer Composites

    NASA Astrophysics Data System (ADS)

    Grunlan, Jaime; Yu, Choongho; Kim, Yeon Seok; Choi, Kyungwho; Kim, Dasarayong

    2010-03-01

    The thermoelectric properties of single-walled carbon nanotube (SWNT)-filled polymer composites can be enhanced by modifying junctions between SWNTs using poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) The resulting composites exhibit electrical conductivities up to ˜40,000 S/m without significantly altering thermopower (or Seebeck coefficient). On the other hand, thermal transport remains comparable to typical polymeric materials due to the dissimilar bonding and vibrational spectra between CNT and PEDOT:PSS. This behavior is very different from that of typical semiconductors whose thermoelectric properties are strongly correlated. SWNT-filled composites, made with an aqueous poly(vinyl acetate) emulsion (dried at room temperature followed by 80^oC) exhibited the best thermoelectric performance in this study. The highest thermoelectric figure of merit (ZT) in this study is ˜0.02 at room temperature, which is at least one order magnitude higher than most polymers and higher than that of bulk Si. Further studies with various polymers and nanoparticles with high thermoelectric performance could result in economical, light-weight, and efficient polymer-based thermoelectrics.

  3. Enhancement of thermoelectric properties in the Nb-Co-Sn half-Heusler/Heusler system through spontaneous inclusion of a coherent second phase

    NASA Astrophysics Data System (ADS)

    Buffon, Malinda L. C.; Laurita, Geneva; Verma, Nisha; Lamontagne, Leo; Ghadbeigi, Leila; Lloyd, Demetrious L.; Sparks, Taylor D.; Pollock, Tresa M.; Seshadri, Ram

    2016-08-01

    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 NbCo2Sn Heusler phase. A series of NbCo1+xSn materials are characterized here using X-ray and neutron diffraction 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 TiNi1+xSn 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.

  4. Thermoelectric Enhancement in PbTe with K or Na codoping from tuning the interaction of the light- and heavy-hole valence bands

    SciTech Connect

    Androulakis, John; Todorov, Iliya; Chung, Duck Young; Ballikaya, Sedat; Wang, Guoyu Y; Uher, Ctirad; Kanatzidis, Mercouri G.

    2010-09-16

    The effect of K and K-Na substitution for Pb atoms in the rocksalt lattice of PbTe was investigated to test a hypothesis for development of resonant states in the valence band that may enhance the thermoelectric power. We combined high-temperature Hall-effect, electrical conductivity, and thermal conductivity measurements to show that K-Na codoping do not form resonance states but can control the energy difference of the maxima of the two primary valence subbands in PbTe. This leads to an enhanced interband interaction with rising temperature and a significant rise in the thermoelectric figure of merit of p -type PbTe. The experimental data can be explained by a combination of a single- and two-band models for the valence band of PbTe depending on hole density that varies in the range of 1–15x1019 cm-3 .

  5. Thermoelectric enhancement in PbTe with K or Na codoping from tuning the interaction of the light- and heavy-hole valence bands.

    SciTech Connect

    Androulakis, J.; Todorov, I.; Chung, D.-Y.; Ballikaya, S.; Wang, G.; Uher, C.; Kanatzidis, M.; Materials Science Division; Northwestern Univ.; Univ. of Michigan at Ann Arbor; Univ. of Istanbul

    2010-09-15

    The effect of K and K-Na substitution for Pb atoms in the rocksalt lattice of PbTe was investigated to test a hypothesis for development of resonant states in the valence band that may enhance the thermoelectric power. We combined high-temperature Hall-effect, electrical conductivity, and thermal conductivity measurements to show that K-Na codoping do not form resonance states but can control the energy difference of the maxima of the two primary valence subbands in PbTe. This leads to an enhanced interband interaction with rising temperature and a significant rise in the thermoelectric figure of merit of p-type PbTe. The experimental data can be explained by a combination of a single- and two-band models for the valence band of PbTe depending on hole density that varies in the range of 1-15 x 10{sup 19} cm{sup -3}.

  6. Enhanced Thermoelectric Properties of Melt-Spun p-Type Yb0.9Fe3CoSb12

    NASA Astrophysics Data System (ADS)

    Son, Geonsik; Lee, Kyu Hyoung; Choi, Soon-Mok

    2016-10-01

    We herein report an enhancement of the thermoelectric properties of p-type Yb0.9Fe3CoSb12 skutterudite by melt spinning combined with spark plasma sintering (SPS). By thermal aging (873 K for 120 h) of the starting Yb0.9Fe3 CoSb12 compound for melt spinning, fabricated by conventional melting and quenching, highly dense single phase bulks with reduced grain sizes of ~300 nm are successfully fabricated after SPS. The power factor value of the sample (~3.6 mW m-1 K-2 at 723 K) is increased, benefiting from an enhancement of the electrical conductivity due to the elimination of the secondary phase CoSb2 during the thermal aging process. In addition, lattice thermal conductivity is significantly decreased due to the reduced grain size, thus intensifying the grain boundary phonon scattering. Through these synergetic effects, the maximum dimensionless figure of merit ZT increases by 25% (0.70 at 723 K) compared to a pristine sample with microscale grains.

  7. 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.

  8. 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. PMID:25942894

  9. Electrical performance analysis and economic evaluation of combined biomass cook stove thermoelectric (BITE) generator.

    PubMed

    Lertsatitthanakorn, C

    2007-05-01

    The use of biomass cook stoves is widespread in the domestic sector of developing countries, but the stoves are not efficient. To advance the versatility of the cook stove, we investigated the feasibility of adding a commercial thermoelectric (TE) module made of bismuth-telluride based materials to the stove's side wall, thereby creating a thermoelectric generator system that utilizes a proportion of the stove's waste heat. The system, a biomass cook stove thermoelectric generator (BITE), consists of a commercial TE module (Taihuaxing model TEP1-1264-3.4), a metal sheet wall which acts as one side of the stove's structure and serves as the hot side of the TE module, and a rectangular fin heat sink at the cold side of the TE module. An experimental set-up was built to evaluate the conversion efficiency at various temperature ranges. The experimental set-up revealed that the electrical power output and the conversion efficiency depended on the temperature difference between the cold and hot sides of the TE module. At a temperature difference of approximately 150 degrees C, the unit achieved a power output of 2.4W. The conversion efficiency of 3.2% was enough to drive a low power incandescent light bulb or a small portable radio. A theoretical model approximated the power output at low temperature ranges. An economic analysis indicated that the payback period tends to be very short when compared with the cost of the same power supplied by batteries. Therefore, the generator design formulated here could be used in the domestic sector. The system is not intended to compete with primary power sources but serves adequately as an emergency or backup source of power.

  10. Nanoscale thermal and thermoelectric transport in silicon

    NASA Astrophysics Data System (ADS)

    Ryu, Hyuk Ju

    Hotspots on microchips are a major challenge for the semiconductor industry. To understand heat conduction from hotspots on silicon, measurements of the thermal resistance and transfer function have been performed using patterned nanoheater/sensor pairs with width from 100 nm up to 5000 nm at temperature range of 30 ˜ 300 K. Calculations of the thermal resistance based on a simple thermal model, considering resistances by spreading, interface, and localized heating match with the measurements. The results reveal several important trends indicating the prevalence of localized heating or sub-continuum transport phenomena in the vicinity of a nanoscale hotspot. Thermoelectric cooling is a possible solution to cope with the hotspot issue. Silicon, in a nanostructured form, is an interesting thermoelectric material, because of significantly reduced thermal conductivity. However, further improvement in thermoelectric efficiency is highly desirable. Thermopower measurements of silicon nanoribbons with an integrated gate have been performed. The gate in the device is used to provide strong carrier confinement and enable tunability of the carrier density over a wide range, which is fully compatible with conventional silicon processing and microelectronics. It therefore offers a promising alternative to doping when considering the thermoelectric engineering of nanostructures. An enhancement of thermoelectric power factor has been observed in silicon nanoribbons. This enhancement can be understood by considering its behavior as a function of carrier density. We identify the underlying mechanisms for the power factor in the nanoribbon, which include quantum confinement, low scattering due to the absence of dopants, and, at low temperatures, a significant phonon drag contribution.

  11. Enhancement of thermoelectric properties by energy filtering: Theoretical potential and experimental reality in nanostructured ZnSb

    NASA Astrophysics Data System (ADS)

    Berland, Kristian; Song, Xin; Carvalho, Patricia A.; Persson, Clas; Finstad, Terje G.; Løvvik, Ole Martin

    2016-03-01

    Energy filtering has been suggested by many authors as a means to improve thermoelectric properties. The idea is to filter away low-energy charge carriers in order to increase Seebeck coefficient without compromising electronic conductivity. This concept was investigated in the present paper for a specific material (ZnSb) by a combination of first-principles atomic-scale calculations, Boltzmann transport theory, and experimental studies of the same system. The potential of filtering in this material was first quantified, and it was as an example found that the power factor could be enhanced by an order of magnitude when the filter barrier height was 0.5 eV. Measured values of the Hall carrier concentration in bulk ZnSb were then used to calibrate the transport calculations, and nanostructured ZnSb with average grain size around 70 nm was processed to achieve filtering as suggested previously in the literature. Various scattering mechanisms were employed in the transport calculations and compared with the measured transport properties in nanostructured ZnSb as a function of temperature. Reasonable correspondence between theory and experiment could be achieved when a combination of constant lifetime scattering and energy filtering with a 0.25 eV barrier was employed. However, the difference between bulk and nanostructured samples was not sufficient to justify the introduction of an energy filtering mechanism. The reasons for this and possibilities to achieve filtering were discussed in the paper.

  12. Enhancement of thermoelectric properties of CoSb3-based skutterudites by double filling of Tl and In

    NASA Astrophysics Data System (ADS)

    Harnwunggmoung, Adul; Kurosaki, Ken; Kosuga, Atsuko; Ishimaru, Manabu; Plirdpring, Theerayuth; Yimnirun, Rattikorn; Jutimoosik, Jaru; Rujirawat, Saroj; Ohishi, Yuji; Muta, Hiroaki; Yamanaka, Shinsuke

    2012-08-01

    Thermoelectric (TE) generators can directly generate electrical power from waste heat, and thus could be an important part of the solution to future power supply and sustainable energy management. The main obstacle to the widespread use of TE materials in diverse industries, e.g., for exhaust heat recovery in automobiles, is their low efficiency in converting heat to electricity. The conversion efficiency of TE materials is quantified by the dimensionless figure of merit, ZT, and the way to enhance ZT is to decrease the lattice thermal conductivity (κlat) of the material, while maintaining a high electrical conductivity, i.e., to create a situation in which phonons are scattered but electrons are unaffected. Here, we report skutterudites filled by Tl and In, Tl0.1InxCo4Sb12, which allow a dramatic reduction of κlat, yielding a ZT of 1.2 at 700 K. We demonstrate that the reduction of κlat is due to the effective phonon scattering induced both by the rattling of Tl and In and by the naturally formed In2O3 nanoparticles (<50 nm). The combined approach of double filling and self-formed nanostructures might be applicable to various clathrate compounds. Thus, our results point to a new strategy in the improvement of bulk TE materials.

  13. Exceeding the filling fraction limit: An approach to enhancement of thermoelectric properties of filled - Co4Sb12 skutterudite

    NASA Astrophysics Data System (ADS)

    Graff, Jennifer Whitney

    Currently the world energy usage has nearly tripled since 1950 and is projected to grow at a rate of 1.5% per year and predicted to at least double from the beginning of the millennium to 2050. The United States alone is currently consuming more energy than it can produce (≈ 97 Quadrillion BTU's consumed in 2011).(1) Presently, fossil fuels make up over 85% of our energy landscape, including both the stationary grid (like coal and nuclear power plants) and the mobile grid (automobiles using gas and oil). This presents a major demand for developing methods of saving, storing, and renewing energy. Answers to these existing energy demands must come from a variety of renewable sources including: solar, wind, biomass, geothermal and others. But currently, most renewable sources are only a small part of the big energy picture. One approach to this exponentially growing problem, lies within high efficiency (15%-20%) thermoelectric (TE) materials which address small, yet very important and specific, parts of a bigger problem. Specifically, Co4Sb12-based skutterudites, an increasingly favorable thermoelectric material for mid to high temperature applications (currently used in General Motors TE Generator devices). These materials have the ability to be 'tuned' or controlled thermally and electrically through doping and filling mechanisms, as you will see in this dissertation. However, one of the major drawbacks of TE materials is the difficulty in optimizing both electrical and thermal properties simultaneously. Typically, different control parameters are used in order to enhance the electrical and thermal properties individually. It is very rare to observe optimization of both in a TE material via one control parameter. However, the work presented herein successfully augments all TE properties, with one control variable, by using an approach that can be applied to all doped skutterudites and clathrate materials. Skutterudites are novel materials in that they are a binary

  14. Enhanced Thermoelectric Properties of Cu2ZnSnSe4 with Ga-doping

    SciTech Connect

    Wei, Kaya; Beauchemin, Laura; Wang, Hsin; Porter, Wallace D.; Martin, Joshua; Nolas, George S.

    2015-08-10

    Gallium doped Cu2ZnSnSe4 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 (S2/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 part 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.

  15. Origins of enhanced thermoelectric power factor in topologically insulating Bi0.64Sb1.36Te3 thin films

    NASA Astrophysics Data System (ADS)

    Liu, Wei; Chi, Hang; Walrath, J. C.; Chang, A. S.; Stoica, Vladimir A.; Endicott, Lynn; Tang, Xinfeng; Goldman, R. S.; Uher, Ctirad

    2016-01-01

    In this research, we report the enhanced thermoelectric power factor in topologically insulating thin films of Bi0.64Sb1.36Te3 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 materials 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-1 K-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 Bi0.64Sb1.36Te3 thin films.

  16. p × n-type transverse thermoelectrics: an alternative Peltier refrigerator with cryogenic promise

    NASA Astrophysics Data System (ADS)

    Zhou, Chuanle; Tang, Y.; Grayson, M.

    2014-02-01

    This work describes a band-engineered transverse thermoelectric with p-type Seebeck in one direction and ntype orthogonal, with off-diagonal terms that drive heat flow transverse to electrical current. Such materials are named p × n type transverse thermoelectrics. Whereas thermoelectric performance is normally limited by the figure of merit ZT, p × n type materials can be more easily geometrically shaped and integrated for devices, leading to more compact, longer lifetime, enhanced efficiency coolers for infrared detectors or photovoltaic generators.

  17. 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.

  18. ATAMM enhancement and multiprocessor performance evaluation

    NASA Technical Reports Server (NTRS)

    Stoughton, John W.; Mielke, Roland R.; Som, Sukhamoy; Obando, Rodrigo; Malekpour, Mahyar R.; Jones, Robert L., III; Mandala, Brij Mohan V.

    1991-01-01

    ATAMM (Algorithm To Architecture Mapping Model) enhancement and multiprocessor performance evaluation is discussed. The following topics are included: the ATAMM model; ATAMM enhancement; ADM (Advanced Development Model) implementation of ATAMM; and ATAMM support tools.

  19. Thermoelectric performance of electron and hole doped PtSb2

    SciTech Connect

    Saeed, Yasir; Singh, Nirprenda; Schwingenschlogl, Udo; Parker, David S

    2013-01-01

    We investigate the thermoelectric properties of electron and hole doped PtSb2. Our results show that for doping of 0.04 holes per unit cell (1:5 1020 cm 3) PtSb2 shows a high Seebeck coefficient at room temperature, which can also be achieved at other temperatures by controlling the carrier concentration (both electron and hole). The electrical conductivity becomes temperature independent when the doping exceeds some 0.2 electrons/holes per unit cell. The figure of merit at 800 K in electron and hole doped PtSb2 is comparatively low at 0.13 and 0.21, respectively, but may increase significantly with As alloying due to the likely opening of a band gap and reduction of the lattice thermal conductivity

  20. Thermoelectric Generator

    NASA Technical Reports Server (NTRS)

    Cole, T.

    1985-01-01

    Small modular alkali metal thermoelectric generator with no moving parts directly converts heat to electrical energy with efficiency of 20 to 40 percent. Unit uses closed regenerative electrochemical concentration cell based on sodium-ion conductor beta alumina.

  1. Effects of Se substitution on the thermoelectric performance of n-type Co{sub 4}Sb{sub 11.3}Te{sub 0.7−x}Se{sub x} skutterudites

    SciTech Connect

    Duan, Bo; Zhai, Pengcheng; Liu, Lisheng; Zhang, Qingjie

    2012-07-15

    Highlights: ► The simple solid state reaction technique was employed to prepare Co{sub 4}Sb{sub 11.3}Te{sub 0.7−x}Se{sub x} skutterudites. ► The thermal conductivity decreases gradually with the increasing Se content. ► Doping with moderate Se is an effective way to enhance the thermoelectric performance of Co{sub 4}Sb{sub 11.3}Te{sub 0.7−x}Se{sub x}. ► The highest ZT of 1.11 at 800 K is obtained for the Co{sub 4}Sb{sub 11.3}Te{sub 0.58}Se{sub 0.12} sample. -- Abstract: A series of double-substituted Co{sub 4}Sb{sub 11.3}Te{sub 0.7−x}Se{sub x} skutterudites have been fabricated by combining the solid state reaction and the spark plasma sintering method, and the effects of Se substitution on the thermoelectric properties are characterized by measurements of the electrical conductivity, the Seebeck coefficient and the thermal conductivity in the temperature range of 300–800 K. Doping Se into the Co{sub 4}Sb{sub 11.3}Te{sub 0.7−x}Se{sub x} matrix suppresses the carrier concentration, and the electrical conductivity actually decreases with the Se content. However, moderate Se doping is effective in enhancing the thermoelectric performance of the n-type Co{sub 4}Sb{sub 11.3}Te{sub 0.7−x}Se{sub x}, because of the resulted dramatically decreased thermal conductivity. Analyses indicate that the heightened point-defect scattering induced by Se doping together with the electron–phonon scattering induced by Te doping is responsible for the reduction of lattice thermal conductivity of these compounds.

  2. 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.

  3. Thermal System Interactions in Optimizing Advanced Thermoelectric Energy Recovery Systems

    SciTech Connect

    Hendricks, Terry J.

    2007-09-01

    Energy recovery is gaining importance in various transportation and industrial process applications because of rising energy costs and geopolitical uncertainties impacting basic energy supplies. Various advanced thermoelectric (TE) materials have properties that are inherently advantageous for particular TE energy recovery applications. Skutterudites, 0- and 1-dimensional quantum-well materials, and thin-film superlattice materials are providing enhanced opportunities for advanced TE energy recovery in transportation and industrial processes. This work demonstrates: 1) the potential for advanced thermoelectric systems in vehicle energy recovery, and 2) the inherently complex interaction between thermal system performance and thermoelectric device optimization in energy recovery. Potential power generation at specific exhaust temperature levels and for various heat exchanger performance levels is presented showing the current design sensitivities using different TE material sets. Mathematical relationships inherently linking optimum TE design variables and the thermal systems design (i.e., heat exchangers and required mass flow rates) are also investigated and characterized.

  4. Thermal System Interactions in Optimizing Advanced Thermoelectric Energy Recovery Systems

    SciTech Connect

    Hendricks, Terry J.

    2007-12-01

    Energy recovery is gaining importance in various transportation and industrial process applications because of rising energy costs and geopolitical uncertainties impacting basic energy supplies. Various advanced thermoelectric (TE) materials have properties that are inherently advantageous for particular TE energy recovery applications. Skutterudites, 0- and 1-dimensional quantum-well materials, and thin-film superlattice materials are providing enhanced opportunities for advanced TE energy recovery in transportation and industrial processes. This work demonstrates: 1) the potential for advanced thermoelectric systems in vehicle energy recovery, and 2) the inherently complex interaction between thermal system performance and thermoelectric device optimization in energy recovery. Potential power generation at specific exhaust temperature levels and for various heat exchanger performance levels are presented showing the current design sensitivities using different TE material sets. Mathematical relationships inherently linking optimum TE design variables and the thermal systems design (i.e., heat exchangers and required mass flow rates) are also investigated and characterized.

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

    SciTech Connect

    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 as 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.

  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. Enhanced Thermoelectric Properties of Sn0.8Pb0.2Te Alloy by Mn Substitution

    NASA Astrophysics Data System (ADS)

    Li, J. Q.; Lu, Z. W.; Wang, C. Y.; Li, Y.; Liu, F. S.; Ao, W. Q.

    2016-06-01

    A series of (Sn0.8Pb0.2)1- x Mn x Te alloys with x = 0, 0.03, 0.06, 0.09, 0.12 and 0.15 were prepared by melting, quenching and spark plasma sintering (SPS) techniques to investigate their phases and thermoelectric properties. Mn was used as doped element in Sn0.8Pb0.2Te solid solution to reduce the carrier concentration, enhance the Seebeck coefficient and reduce the thermal conductivity of the material. Experimental results show that the SnTe-based solid solution single phase was formed in the alloys with x = 0 and 0.03. The minor irregular-shaped MnTe2 phase presents in the alloys with x ≥ 0.06, while the minor needle-like MnTe phase appears in the alloys with x ≥ 0.12, together with the SnTe-based solid solution matrix. The lattice parameter a of SnTe-based solid solution decreases nearly linearly as Mn content x increases up to 0.12, but keeps constant as x further increases. All the samples show p-type conduction. Mn doping in Sn0.8Pb0.2Te decreases its carrier concentration and thus increases its Seebeck coefficient. The solute Mn and Pb atoms in the SnTe-based solid solution, and the minor phases MnTe2 and MnTe, enhance the phonon scattering and thus reduce the thermal conductivity. As a result, the figure-of-merit ZT of the (Sn0.8Pb0.2)1- x Mn x Te composites can be enhanced with proper Mn substitution. The maximum ZT of 0.65 was obtained in the sample (Sn0.8Pb0.2)0.88Mn0.12Te at 723 K, which is higher than the 0.29 of its parent alloy Sn0.8Pb0.2Te.

  8. Thermoelectric properties of Zintl compound Ca1-xNaxMg2Bi1.98

    NASA Astrophysics Data System (ADS)

    Shuai, Jing; Kim, Hee Seok; Liu, Zihang; He, Ran; Sui, Jiehe; Ren, Zhifeng

    2016-05-01

    Motivated by good thermoelectric performance of Bi-based Zintl compounds Ca1-xYbxMg2Biy, we further studied the thermoelectric properties of Zintl compound CaMg2Bi1.98 by doping Na into Ca as Ca1-xNaxMg2Bi1.98 via mechanical alloying and hot pressing. We found that the electrical conductivity, Seebeck coefficient, power factor, and carrier concentration can be effectively adjusted by tuning the Na concentration. Transport measurement and calculations revealed that an optimal doping of 0.5 at. % Na achieved better average ZT and efficiency. The enhancement in thermoelectric performance is attributed to the increased carrier concentration and power factor. The low cost and nontoxicity of Ca1-xNaxMg2Bi1.98 makes it a potentially promising thermoelectric material for power generation in the mid-temperature range.

  9. Evaluating Thermoelectric Power Generation Device Performance Using a Rectangular Microchannel Heat Sink

    NASA Astrophysics Data System (ADS)

    Rezania, A.; Rosendahl, L. A.

    2011-05-01

    In this work, a microchannel heat sink is applied to a thermoelectric power generation (TEG) device and compared with a traditional heat sink. The advantages and disadvantages of using each heat sink in a TEG device are evaluated. The microchannel hydraulic diameter is 5.33 × 10-4 m and that of the macrochannel is 2.13 × 10-3 m. Pressure drops and heat removed in the micro heat sink configuration are obtained for six different mass flow rates for the laminar and turbulent fluid flow regimes. By computationally applying a constant temperature difference between the hot and cold sides of the TEG, the fluid and thermal parameters are considered for both laminar and turbulent regimes in the channels. Furthermore, using the temperature difference through each TEG, the system efficiency is calculated. The results show that the microchannel heat sink gives a higher pressure drop, but the heat flow across the TEG device and the mass flow rate needed to provide the same generated power are less than for the macrochannel heat sink.

  10. Heterovalent Substitution to Enrich Electrical Conductivity in Cu2CdSn1-xGaxSe4 Series for High Thermoelectric Performances

    PubMed Central

    Wang, Bo; Li, Yu; Zheng, Jiaxin; Xu, Ming; Liu, Fusheng; Ao, Weiqing; Li, Junqing; Pan, Feng

    2015-01-01

    Serials of Ga doping on Sn sites as heterovalent substitution in Cu2CdSnSe4 are prepared by the melting method and the spark plasma sintering (SPS) technique to form Cu2CdSn1-xGaxSe4 (x = 0, 0.025, 0.05, 0.075, 0.01, and 0.125). Massive atomic vacancies are found at x = 0.10 by the heterovalent substitution, which contributes significantly to the increase of electrical conductivity and the decrease of lattice thermal conductivity. The electrical conductivity is increased by about ten times at 300 K after Ga doping. Moreover, the seebeck coefficient only decreases slightly from 310 to 226 μV/K at 723 K, and a significant increase of the power factor is obtained. As a result, a maxium value of 0.27 for the figure of merit (ZT) is obtained at x = 0.10 and at 723 K. Through an ab initio study of the Ga doping effect, we find that the Fermi level of Cu2CdSnSe4 is shifted downward to the valence band, thus improving the hole concentration and enhancing the electrical conductivity at low doping levels. Our experimental and theoretical studies show that a moderate Ga doping on Sn sites is an effective method to improve the thermoelectric performance of Cu2CdSnSe4. PMID:25791823

  11. Perform or Else: The Performative Enhancement of Teacher Professionalism

    ERIC Educational Resources Information Center

    Liew, Warren Mark

    2012-01-01

    The Singapore Ministry of Education's Enhanced Performance Management System (EPMS) was instituted in 2005 as a system of professional accountability to enhance the standards and stakes of teacher professionalism in schools. This essay explores how the EPMS, with its underlying paradigm of performance management, functions as a "technology of…

  12. A Novel Optimization Method for the Electric Topology of Thermoelectric Modules Used in an Automobile Exhaust Thermoelectric Generator

    NASA Astrophysics Data System (ADS)

    Quan, Rui; Tang, Xinfeng; Quan, Shuhai; Huang, Liang

    2013-07-01

    Based on Bi2Te3 thermoelectric modules, a kind of automobile exhaust thermoelectric generator (AETEG) with a single-column cold-source structure was designed. To enhance its net power and efficiency, the output performance of all the thermoelectric modules was tested with a temperature monitoring unit and voltage monitoring unit, and modeled using a back-propagation (BP) neural network based on various hot-source temperatures, cold-source temperatures, load currents, and contact pressures according to the temperature distribution of the designed heat exchanger and cooling system. Then, their electric topology (series or parallel hybrid) was optimized using a genetic algorithm to achieve the maximum peak power of the AETEG. From the experimental results, compared with when all the thermoelectric modules were connected only in series or parallel at random, it is concluded that the AETEG performance is evidently affected by the electric topology of all the single thermoelectric modules. The optimized AETEG output power is greatly superior to the other two investigated designs, validating the proposed optimized electric topology as both feasible and practical.

  13. Engineered Molecular Chain Ordering in Single-Walled Carbon Nanotubes/Polyaniline Composite Films for High-Performance Organic Thermoelectric Materials.

    PubMed

    Wang, Liming; Yao, Qin; Xiao, Juanxiu; Zeng, Kaiyang; Qu, Sanyin; Shi, Wei; Wang, Qun; Chen, Lidong

    2016-06-21

    Single-walled carbon nanotubes (SWNTs)/polyaniline (PANI) composite films with enhanced thermoelectric properties were prepared by combining in situ polymerization and solution processing. Conductive atomic force microscopy and X-ray diffraction measurements confirmed that solution processing and strong π-π interactions between the PANI and SWNTs induced the PANI molecules to form a highly ordered structure. The improved degree of order of the PANI molecular arrangement increased the carrier mobility and thereby enhanced the electrical transport properties of PANI. The maximum in-plane electrical conductivity and power factor of the SWNTs/PANI composite films reached 1.44×10(3)  S cm(-1) and 217 μW m(-1)  K(-2) , respectively, at room temperature. Furthermore, a thermoelectric generator fabricated with the SWNTs/PANI composite films showed good electric generation ability and stability. A high power density of 10.4 μW cm(-2)  K(-1) was obtained, which is superior to most reported results obtained in organic thermoelectric modules. PMID:27123885

  14. Engineered Molecular Chain Ordering in Single-Walled Carbon Nanotubes/Polyaniline Composite Films for High-Performance Organic Thermoelectric Materials.

    PubMed

    Wang, Liming; Yao, Qin; Xiao, Juanxiu; Zeng, Kaiyang; Qu, Sanyin; Shi, Wei; Wang, Qun; Chen, Lidong

    2016-06-21

    Single-walled carbon nanotubes (SWNTs)/polyaniline (PANI) composite films with enhanced thermoelectric properties were prepared by combining in situ polymerization and solution processing. Conductive atomic force microscopy and X-ray diffraction measurements confirmed that solution processing and strong π-π interactions between the PANI and SWNTs induced the PANI molecules to form a highly ordered structure. The improved degree of order of the PANI molecular arrangement increased the carrier mobility and thereby enhanced the electrical transport properties of PANI. The maximum in-plane electrical conductivity and power factor of the SWNTs/PANI composite films reached 1.44×10(3)  S cm(-1) and 217 μW m(-1)  K(-2) , respectively, at room temperature. Furthermore, a thermoelectric generator fabricated with the SWNTs/PANI composite films showed good electric generation ability and stability. A high power density of 10.4 μW cm(-2)  K(-1) was obtained, which is superior to most reported results obtained in organic thermoelectric modules.

  15. Study of thermal stability of Cu2Se thermoelectric material

    NASA Astrophysics Data System (ADS)

    Bohra, Anil; Bhatt, Ranu; Bhattacharya, Shovit; Basu, Ranita; Ahmad, Sajid; Singh, Ajay; Aswal, D. K.; Gupta, S. K.

    2016-05-01

    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 Cu2Se 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 Cu2Se phase in bare pellet which transforms to pure α-Cu2Se phase with repeating thermal cycle. Significant enhancement in Seebeck coefficient and electrical resistivity is observed which may be attributed to (i) Se loss observed in EDS and (ii) the phase transformation from mixed cubic-monoclinic structure to pure monoclinic α-Cu2Se phase.

  16. Thermodynamics of Thermoelectric Materials

    NASA Astrophysics Data System (ADS)

    Doak, Jeff W.

    driving force(s) for nanostructure formation, 2) investigate the thermodynamics of PbTe--PbS alloys in more detail, including the effects of thermal motion, which are important and difficult to investigate due to the inherently anharmonic nature of PbTe, 3) investigate the thermodynamics of doping Na into PbTe and PbS, 4) investigate the thermodynamics of Na at the interface between PbTe and PbS, to understand how a nominal dopant can also cause changes in the morphology of nanostructures, and 5) apply the lessons learned in the above investigations, combined with measures of good electronic properties to screen for new thermoelectric alloys of II--VI, IIb--VI, and IV--VI compounds which will have improved thermoelectric performance. With this work we can move the field of thermoelectric materials forward, providing insight and predictions for further experimental refinement, leading to more efficient materials, and a more energy efficient future.

  17. Simple method for modeling thermoelectric cooler (TEC) performance of single-emitter semiconductor-laser packages with concentrated heat sources

    NASA Astrophysics Data System (ADS)

    Du, J.; Au, M.; Zavala, L.; Yalamanchili, P.; Skidmore, J.; Zucker, E.

    2010-02-01

    High-power single-emitter semiconductor lasers may dissipate up to several Watts heat load during operation. The heat may be generated from a narrow stripe, as low as a few microns in width by several millimeters in length. Thermoelectric Coolers (TEC) are widely deployed to control the laser junction temperature in single-emitter semiconductor-laser packages. TEC manufacturers supply performance curves under the assumption of uniform heat load applied to the cold plate. In reality, the heat will spread laterally across the cold plate creating a temperature gradient across the couples. Consequently, the actual performance of the TEC may be significantly degraded as compared to that predicted from the manufacturer's guidelines. A quantitative analysis that includes these deviations is necessary to properly size the TEC and optimize the package design. This paper provides a simple method for modeling the TEC performance parameters on concentrated heat loads using commercially-available FEA software. Experimental data of TEC cooled single-emitter laser packages will also be presented that corroborate the results of our model.

  18. Thermoelectric materials -- New directions and approaches. Materials Research Society symposium proceedings, Volume 478

    SciTech Connect

    Tritt, T.M.; Kanatzidis, M.G.; Lyon, H.B. Jr.; Mahan, G.D.

    1997-07-01

    Thermoelectric materials are utilized in a wide variety of applications related to solid-state refrigeration or small-scale power generation. Thermoelectric cooling is an environmentally friendly method of small-scale cooling in specific applications such as cooling computer chips and laser diodes. Thermoelectric materials are used in a wide range of applications from beverage coolers to power generation for deep-space probes such as the Voyager missions. Over the past thirty years, alloys based on the Bi-Te systems {l{underscore}brace}(Bi{sub 1{minus}x}Sb{sub x}){sub 2} (Te{sub 1{minus}x}Se{sub x}){sub 3}{r{underscore}brace} and Si{sub 1{minus}x}Ge{sub x} systems have been extensively studied and optimized for their use as thermoelectric materials to perform a variety of solid-state thermoelectric refrigeration and power generation tasks. Despite this extensive investigation of the traditional thermoelectric materials, there is still a substantial need and room for improvement, and thus, entirely new classes of compounds will have to be investigated. Over the past two-to-three years, research in the field of thermoelectric materials has been undergoing a rapid rebirth. The enhanced interest in better thermoelectric materials has been driven by the need for much higher performance and new temperature regimes for thermoelectric devices in many applications. The essence of a good thermoelectric is given by the determination of the material's dimensionless figure of merit, ZT = ({alpha}{sup 2}{sigma}/{lambda})T, where {alpha} is the Seebeck coefficient, {sigma} the electrical conductivity and {lambda} the total thermal conductivity. The best thermoelectric materials have a value of ZT = 1. This ZT = 1 has been an upper limit for more than 30 years, yet no theoretical or thermodynamic reason exits for why it can not be larger. The focus of the symposium is embodied in the title, Thermoelectric Materials: New Directions and Approaches. Many of the researchers in the

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

    SciTech Connect

    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.

  20. Thermoelectric effects in silicene nanoribbons

    NASA Astrophysics Data System (ADS)

    Zberecki, K.; Wierzbicki, M.; Barnaś, J.; Swirkowicz, R.

    2013-09-01

    Transport and thermoelectric coefficients (including also spin thermopower) of silicene nanoribbons with zigzag edges are investigated by ab initio numerical methods. Local spin density of such nanoribbons reveals edge magnetism. As in graphene, one finds antiferromagnetic and ferromagnetic ordering, with spin polarization at one edge antiparallel or parallel to that at the other edge, respectively. Thermoelectric properties, especially the Seebeck coefficient, significantly depend on the electronic band structure and are enhanced when the Fermi level is in the energy gap. However, the thermoelectric efficiency is significantly reduced when the phonon contribution to the heat conductance is included. This phonon contribution has been calculated numerically by two different methods. Transition from antiferromagnetic to ferromagnetic states leads to a large magnetoresistance as well as to a considerable magnetothermopower. Thermoelectric parameters in the antiparallel configuration, when spin polarization in the left part of the nanoribbon is opposite to that in the right part, are also analyzed.

  1. Band engineering of thermoelectric materials.

    PubMed

    Pei, Yanzhong; Wang, Heng; Snyder, G J

    2012-12-01

    Lead chalcogenides have long been used for space-based and thermoelectric remote power generation applications, but recent discoveries have revealed a much greater potential for these materials. This renaissance of interest combined with the need for increased energy efficiency has led to active consideration of thermoelectrics for practical waste heat recovery systems-such as the conversion of car exhaust heat into electricity. The simple high symmetry NaCl-type cubic structure, leads to several properties desirable for thermoelectricity, such as high valley degeneracy for high electrical conductivity and phonon anharmonicity for low thermal conductivity. The rich capabilities for both band structure and microstructure engineering enable a variety of approaches for achieving high thermoelectric performance in lead chalcogenides. This Review focuses on manipulation of the electronic and atomic structural features which makes up the thermoelectric quality factor. While these strategies are well demonstrated in lead chalcogenides, the principles used are equally applicable to most good thermoelectric materials that could enable improvement of thermoelectric devices from niche applications into the mainstream of energy technologies. PMID:23074043

  2. Band engineering of thermoelectric materials.

    PubMed

    Pei, Yanzhong; Wang, Heng; Snyder, G J

    2012-12-01

    Lead chalcogenides have long been used for space-based and thermoelectric remote power generation applications, but recent discoveries have revealed a much greater potential for these materials. This renaissance of interest combined with the need for increased energy efficiency has led to active consideration of thermoelectrics for practical waste heat recovery systems-such as the conversion of car exhaust heat into electricity. The simple high symmetry NaCl-type cubic structure, leads to several properties desirable for thermoelectricity, such as high valley degeneracy for high electrical conductivity and phonon anharmonicity for low thermal conductivity. The rich capabilities for both band structure and microstructure engineering enable a variety of approaches for achieving high thermoelectric performance in lead chalcogenides. This Review focuses on manipulation of the electronic and atomic structural features which makes up the thermoelectric quality factor. While these strategies are well demonstrated in lead chalcogenides, the principles used are equally applicable to most good thermoelectric materials that could enable improvement of thermoelectric devices from niche applications into the mainstream of energy technologies.

  3. A theoretical prediction of super high-performance thermoelectric materials based on MoS2/WS2 hybrid nanoribbons

    NASA Astrophysics Data System (ADS)

    Zhang, Zhongwei; Xie, Yuee; Peng, Qing; Chen, Yuanping

    2016-02-01

    Modern society is hungry for electrical power. To improve the efficiency of energy harvesting from heat, extensive efforts seek high-performance thermoelectric materials that possess large differences between electronic and thermal conductance. Here we report a super high-performance material of consisting of MoS2/WS2 hybrid nanoribbons discovered from a theoretical investigation using nonequilibrium Green’s function methods combined with first-principles calculations and molecular dynamics simulations. The hybrid nanoribbons show higher efficiency of energy conversion than the MoS2 and WS2 nanoribbons due to the fact that the MoS2/WS2 interface reduces lattice thermal conductivity more than the electron transport. By tuning the number of the MoS2/WS2 interfaces, a figure of merit ZT as high as 5.5 is achieved at a temperature of 600 K. Our results imply that the MoS2/WS2 hybrid nanoribbons have promising applications in thermal energy harvesting.

  4. A theoretical prediction of super high-performance thermoelectric materials based on MoS2/WS2 hybrid nanoribbons

    PubMed Central

    Zhang, Zhongwei; Xie, Yuee; Peng, Qing; Chen, Yuanping

    2016-01-01

    Modern society is hungry for electrical power. To improve the efficiency of energy harvesting from heat, extensive efforts seek high-performance thermoelectric materials that possess large differences between electronic and thermal conductance. Here we report a super high-performance material of consisting of MoS2/WS2 hybrid nanoribbons discovered from a theoretical investigation using nonequilibrium Green’s function methods combined with first-principles calculations and molecular dynamics simulations. The hybrid nanoribbons show higher efficiency of energy conversion than the MoS2 and WS2 nanoribbons due to the fact that the MoS2/WS2 interface reduces lattice thermal conductivity more than the electron transport. By tuning the number of the MoS2/WS2 interfaces, a figure of merit ZT as high as 5.5 is achieved at a temperature of 600 K. Our results imply that the MoS2/WS2 hybrid nanoribbons have promising applications in thermal energy harvesting. PMID:26884123

  5. A theoretical prediction of super high-performance thermoelectric materials based on MoS2/WS2 hybrid nanoribbons.

    PubMed

    Zhang, Zhongwei; Xie, Yuee; Peng, Qing; Chen, Yuanping

    2016-02-17

    Modern society is hungry for electrical power. To improve the efficiency of energy harvesting from heat, extensive efforts seek high-performance thermoelectric materials that possess large differences between electronic and thermal conductance. Here we report a super high-performance material of consisting of MoS2/WS2 hybrid nanoribbons discovered from a theoretical investigation using nonequilibrium Green's function methods combined with first-principles calculations and molecular dynamics simulations. The hybrid nanoribbons show higher efficiency of energy conversion than the MoS2 and WS2 nanoribbons due to the fact that the MoS2/WS2 interface reduces lattice thermal conductivity more than the electron transport. By tuning the number of the MoS2/WS2 interfaces, a figure of merit ZT as high as 5.5 is achieved at a temperature of 600 K. Our results imply that the MoS2/WS2 hybrid nanoribbons have promising applications in thermal energy harvesting.

  6. Sensor fusion method for machine performance enhancement

    SciTech Connect

    Mou, J.I.; King, C.; Hillaire, R.; Jones, S.; Furness, R.

    1998-03-01

    A sensor fusion methodology was developed to uniquely integrate pre-process, process-intermittent, and post-process measurement and analysis technology to cost-effectively enhance the accuracy and capability of computer-controlled manufacturing equipment. Empirical models and computational algorithms were also developed to model, assess, and then enhance the machine performance.

  7. Development of High-efficiency Thermoelectric Materials for Vehicle Waste Heat Utililization

    SciTech Connect

    Li, Qiang

    2009-04-30

    The goals of this . CRADA are: 1) Investigation of atomistic structure and nucleation of nanoprecipitates in (PbTe){sub I-x}(AgSbTe2){sub x} (LAST) system; and 2) Development of non-equilibrium synthesis of thermoelectric materials for waste heat recovery. We have made significant accomplishment in both areas. We studied the structure of LAST materials using high resolution imaging, nanoelectron diffraction, energy dispersive spectrum, arid electron energy loss spectrum, and observed a range of nanoparticles The results, published in J. of Applied Physics, provide quantitative structure information about nanoparticles, that is essential for the understanding of the origin of the high thermoelectric performance in this class of materials. We coordinated non-equilibrium synthesis and characterization of thermoelectric materials for waste heat recovery application. Our results, published in J. of Electronic Materials, show enhanced thermoelectric figure of merit and robust mechanical properties in bulk . filled skutterudites.

  8. 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.

  9. 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.

  10. Performance and impedance studies of thin, porous molybdenum and tungsten electrodes for the alkali metal thermoelectric converter

    NASA Technical Reports Server (NTRS)

    Wheeler, B. L.; Williams, R. M.; Jeffries-Nakamura, B.; Lamb, J. L.; Loveland, M. E.; Bankston, C. P.; Cole, T.

    1988-01-01

    Columnar, porous, magnetron-sputtered molybdenum and tungsten films show optimum performance as alkali metal thermoelectric converter electrodes at thicknesses less than 1.0 micron when used with molybdenum or nickel current collector grids. Power densities of 0.40 W/sq cm for 0.5-micron molybdenum films at 1200 K and 0.35 W/sq cm for 0.5-micron tungsten films at 1180 K were obtained at electrode maturity after 40-90 h. Sheet resistances of magnetron sputter deposited films on sodium beta-double-prime-alumina solid electrolyte (BASE) substrates were found to increase very steeply as thickness is decreased below about 0.3-double-prime 0.4-micron. The ac impedance data for these electrodes have been interpreted in terms of contributions from the bulk BASE and the porous electrode/BASE interface. Voltage profiles of operating electrodes show that the total electrode area, of electrodes with thickness less than 2.0 microns, is not utilized efficiently unless a fairly fine (about 1 x 1 mm) current collector grid is employed.

  11. High temperature thermoelectrics

    SciTech Connect

    Moczygemba, Joshua E.; Biershcenk, James L.; Sharp, Jeffrey W.

    2014-09-23

    In accordance with one embodiment of the present disclosure, a thermoelectric device includes a plurality of thermoelectric elements that each include a diffusion barrier. The diffusion barrier includes a refractory metal. The thermoelectric device also includes a plurality of conductors coupled to the plurality of thermoelectric elements. The plurality of conductors include aluminum. In addition, the thermoelectric device includes at least one plate coupled to the plurality of thermoelectric elements using a braze. The braze includes aluminum.

  12. Enhanced Thermoelectric Properties of Antimony Telluride Thin Films with Preferred Orientation Prepared by Sputtering a Fan-Shaped Binary Composite Target

    NASA Astrophysics Data System (ADS)

    Zheng, Zhuang-hao; Fan, Ping; Luo, Jing-ting; Liang, Guang-xing; Zhang, Dong-ping

    2013-12-01

    p-Type antimony telluride (Sb2Te3) thermoelectric thin films were deposited on BK7 glass substrates by ion beam sputter deposition using a fan-shaped binary composite target. The deposition temperature was varied from 100°C to 300°C in increments of 50°C. The influence of the deposition temperature on the microstructure, surface morphology, and thermoelectric properties of the thin films was systematically investigated. x-Ray diffraction results show that various alloy composition phases of the Sb2Te3 materials are grown when the deposition temperature is lower than 200°C. Preferred c-axis orientation of the Sb2Te3 thin film became obvious when the deposition temperature was above 200°C, and thin film with single-phase Sb2Te3 was obtained when the deposition temperature was 250°C. Scanning electron microscopy reveals that the average grain size of the films increases with increasing deposition temperature and that the thin film deposited at 250°C shows rhombohedral shape corresponding to the original Sb2Te3 structure. The room-temperature Seebeck coefficient and electrical conductivity range from 101 μV K-1 to 161 μV K-1 and 0.81 × 103 S cm-1 to 3.91 × 103 S cm-1, respectively, as the deposition temperature is increased from 100°C to 300°C. An optimal power factor of 6.12 × 10-3 W m-1 K-2 is obtained for deposition temperature of 250°C. The thermoelectric properties of Sb2Te3 thin films have been found to be strongly enhanced when prepared using the fan-shaped binary composite target method with an appropriate substrate temperature.

  13. Sensorimotor Rhythm Neurofeedback Enhances Golf Putting Performance.

    PubMed

    Cheng, Ming-Yang; Huang, Chung-Ju; Chang, Yu-Kai; Koester, Dirk; Schack, Thomas; Hung, Tsung-Min

    2015-12-01

    Sensorimotor rhythm (SMR) activity has been related to automaticity during skilled action execution. However, few studies have bridged the causal link between SMR activity and sports performance. This study investigated the effect of SMR neurofeedback training (SMR NFT) on golf putting performance. We hypothesized that preelite golfers would exhibit enhanced putting performance after SMR NFT. Sixteen preelite golfers were recruited and randomly assigned into either an SMR or a control group. Participants were asked to perform putting while electroencephalogram (EEG) was recorded, both before and after intervention. Our results showed that the SMR group performed more accurately when putting and exhibited greater SMR power than the control group after 8 intervention sessions. This study concludes that SMR NFT is effective for increasing SMR during action preparation and for enhancing golf putting performance. Moreover, greater SMR activity might be an EEG signature of improved attention processing, which induces superior putting performance. PMID:26866770

  14. Polarization field engineering of GaN/AlN/AlGaN superlattices for enhanced thermoelectric properties

    SciTech Connect

    Sztein, Alexander; Bowers, John E.; DenBaars, Steven P.; Nakamura, Shuji

    2014-01-27

    A novel polarization field engineering based strategy to simultaneously achieve high electrical conductivity and low thermal conductivity in thermoelectric materials is demonstrated. Polarization based electric fields are used to confine electrons into two-dimensional electron gases in GaN/AlN/Al{sub 0.2}Ga{sub 0.8}N superlattices, resulting in improved electron mobilities as high as 1176 cm{sup 2}/Vs and in-plane thermal conductivity as low as 8.9 W/mK. The resulting room temperature ZT values reach 0.08, a factor of four higher than InGaN and twelve higher than GaN, demonstrating the potential benefits of this polarization based engineering strategy for improving the ZT and efficiencies of thermoelectric materials.

  15. Harnessing Topological Band Effects in Bismuth Telluride Selenide for Large Enhancements in Thermoelectric Properties through Isovalent Doping.

    PubMed

    Devender; Gehring, Pascal; Gaul, Andrew; Hoyer, Alexander; Vaklinova, Kristina; Mehta, Rutvik J; Burghard, Marko; Borca-Tasciuc, Theodorian; Singh, David J; Kern, Klaus; Ramanath, Ganpati

    2016-08-01

    Dilute isovalent sulfur doping simultaneously increases electrical conductivity and Seebeck coefficient in Bi2 Te2 Se nanoplates, and bulk pellets made from them. This unusual trend at high electron concentrations is underpinned by multifold increases in electron effective mass attributable to sulfur-induced band topology effects, providing a new way for accessing a high thermoelectric figure-of-merit in topological-insulator-based nanomaterials through doping.

  16. Harnessing Topological Band Effects in Bismuth Telluride Selenide for Large Enhancements in Thermoelectric Properties through Isovalent Doping.

    PubMed

    Devender; Gehring, Pascal; Gaul, Andrew; Hoyer, Alexander; Vaklinova, Kristina; Mehta, Rutvik J; Burghard, Marko; Borca-Tasciuc, Theodorian; Singh, David J; Kern, Klaus; Ramanath, Ganpati

    2016-08-01

    Dilute isovalent sulfur doping simultaneously increases electrical conductivity and Seebeck coefficient in Bi2 Te2 Se nanoplates, and bulk pellets made from them. This unusual trend at high electron concentrations is underpinned by multifold increases in electron effective mass attributable to sulfur-induced band topology effects, providing a new way for accessing a high thermoelectric figure-of-merit in topological-insulator-based nanomaterials through doping. PMID:27167512

  17. Learning, Remembering, Believing. Enhancing Human Performance.

    ERIC Educational Resources Information Center

    Druckman, Daniel, Ed.; Bjork, Robert A., Ed.

    This book is the third report of the Committee on Techniques for the Enhancement of Human Performance. Based on hundreds of research studies of learning and human performance as reported in the literature, the book consists of 11 chapters organized in five parts. The two chapters of the first part provide the background and summary of the…

  18. 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.

  19. Significant enhancement of thermoelectric properties and metallization of Al-doped Mg{sub 2}Si under pressure

    SciTech Connect

    Morozova, Natalia V.; Korobeinikov, Igor V.; Karkin, Alexander E.; Shchennikov, Vladimir V.; Ovsyannikov, Sergey V. E-mail: sergey2503@gmail.com; Takarabe, Ken-ichi; Mori, Yoshihisa; Nakamura, Shigeyuki

    2014-06-07

    We report results of investigations of electronic transport properties and lattice dynamics of Al-doped magnesium silicide (Mg{sub 2}Si) thermoelectrics at ambient and high pressures to and beyond 15 GPa. High-quality samples of Mg{sub 2}Si doped with 1 at. % of Al were prepared by spark plasma sintering technique. The samples were extensively examined at ambient pressure conditions by X-ray diffraction studies, Raman spectroscopy, electrical resistivity, magnetoresistance, Hall effect, thermoelectric power (Seebeck effect), and thermal conductivity. A Kondo-like feature in the electrical resistivity curves at low temperatures indicates a possible magnetism in the samples. The absolute values of the thermopower and electrical resistivity, and Raman spectra intensity of Mg{sub 2}Si:Al dramatically diminished upon room-temperature compression. The calculated thermoelectric power factor of Mg{sub 2}Si:Al raised with pressure to 2–3 GPa peaking in the maximum the values as high as about 8 × 10{sup −3} W/(K{sup 2}m) and then gradually decreased with further compression. Raman spectroscopy studies indicated the crossovers near ∼5–7 and ∼11–12 GPa that are likely related to phase transitions. The data gathered suggest that Mg{sub 2}Si:Al is metallized under moderate pressures between ∼5 and 12 GPa.

  20. Promising thermoelectric properties of phosphorenes.

    PubMed

    Sevik, Cem; Sevinçli, Hâldun

    2016-09-01

    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.

  1. Promising thermoelectric properties of phosphorenes

    NASA Astrophysics Data System (ADS)

    Sevik, Cem; Sevinçli, Hâldun

    2016-09-01

    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.

  2. Promising thermoelectric properties of phosphorenes.

    PubMed

    Sevik, Cem; Sevinçli, Hâldun

    2016-09-01

    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. PMID:27455173

  3. Valence Band Modification and High Thermoelectric Performance in SnTe Heavily Alloyed with MnTe.

    PubMed

    Tan, Gangjian; Shi, Fengyuan; Hao, Shiqiang; Chi, Hang; Bailey, Trevor P; Zhao, Li-Dong; Uher, Ctirad; Wolverton, Chris; Dravid, Vinayak P; Kanatzidis, Mercouri G

    2015-09-01

    We demonstrate a high solubility limit of >9 mol% for MnTe alloying in SnTe. The electrical conductivity of SnTe decreases gradually while the Seebeck coefficient increases remarkably with increasing MnTe content, leading to enhanced power factors. The room-temperature Seebeck coefficients of Mn-doped SnTe are significantly higher than those predicted by theoretical Pisarenko plots for pure SnTe, indicating a modified band structure. The high-temperature Hall data of Sn1-xMnxTe show strong temperature dependence, suggestive of a two-valence-band conduction behavior. Moreover, the peak temperature of the Hall plot of Sn1-xMnxTe shifts toward lower temperature as MnTe content is increased, which is clear evidence of decreased energy separation (band convergence) between the two valence bands. The first-principles electronic structure calculations based on density functional theory also support this point. The higher doping fraction (>9%) of Mn in comparison with ∼3% for Cd and Hg in SnTe gives rise to a much better valence band convergence that is responsible for the observed highest Seebeck coefficient of ∼230 μV/K at 900 K. The high doping fraction of Mn in SnTe also creates stronger point defect scattering, which when combined with ubiquitous endotaxial MnTe nanostructures when the solubility of Mn is exceeded scatters a wide spectrum of phonons for a low lattice thermal conductivity of 0.9 W m(-1) K(-1) at 800 K. The synergistic role that Mn plays in regulating the electron and phonon transport of SnTe yields a high thermoelectric figure of merit of 1.3 at 900 K. PMID:26308902

  4. Valence Band Modification and High Thermoelectric Performance in SnTe Heavily Alloyed with MnTe.

    PubMed

    Tan, Gangjian; Shi, Fengyuan; Hao, Shiqiang; Chi, Hang; Bailey, Trevor P; Zhao, Li-Dong; Uher, Ctirad; Wolverton, Chris; Dravid, Vinayak P; Kanatzidis, Mercouri G

    2015-09-01

    We demonstrate a high solubility limit of >9 mol% for MnTe alloying in SnTe. The electrical conductivity of SnTe decreases gradually while the Seebeck coefficient increases remarkably with increasing MnTe content, leading to enhanced power factors. The room-temperature Seebeck coefficients of Mn-doped SnTe are significantly higher than those predicted by theoretical Pisarenko plots for pure SnTe, indicating a modified band structure. The high-temperature Hall data of Sn1-xMnxTe show strong temperature dependence, suggestive of a two-valence-band conduction behavior. Moreover, the peak temperature of the Hall plot of Sn1-xMnxTe shifts toward lower temperature as MnTe content is increased, which is clear evidence of decreased energy separation (band convergence) between the two valence bands. The first-principles electronic structure calculations based on density functional theory also support this point. The higher doping fraction (>9%) of Mn in comparison with ∼3% for Cd and Hg in SnTe gives rise to a much better valence band convergence that is responsible for the observed highest Seebeck coefficient of ∼230 μV/K at 900 K. The high doping fraction of Mn in SnTe also creates stronger point defect scattering, which when combined with ubiquitous endotaxial MnTe nanostructures when the solubility of Mn is exceeded scatters a wide spectrum of phonons for a low lattice thermal conductivity of 0.9 W m(-1) K(-1) at 800 K. The synergistic role that Mn plays in regulating the electron and phonon transport of SnTe yields a high thermoelectric figure of merit of 1.3 at 900 K.

  5. 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

  6. Enhanced vision: flight test and performance measurement

    NASA Astrophysics Data System (ADS)

    Balon, Kevin G.; Connor, Sidney A.

    1997-06-01

    This paper presents a flight test methodology and performance measurement system for evaluation of enhanced vision systems (EVS). The architecture for the performance measurements system used on a low operating cost Cessna 402 EVS flight test aircraft and on the DARPA Autonomous Landing Guidance Boeing 727 flight test aircraft is described. The data collection and analysis system is presented in the context of civil aviation requirements. A summary of the flight test accomplishments with the performance measurements system to data is also presented.

  7. Diagnostic performance with enhanced digital mammographic films

    NASA Astrophysics Data System (ADS)

    Flynn, Michael J.; Chen, Ji; Rebner, Murray; Windham, Joe P.

    1993-06-01

    Digital storage and display of mammograms could significantly improve operations in breast cancer screening programs. If mammographic films are scanned with high performance instruments, enhanced display and/or computer-aided diagnosis may improve diagnostic performance. We are studying observer performance with digital mammograms printed with 1.9X magnification, skin line equalization, and background masking. The purpose of the study is to establish that mammograms can be digitized with no loss in quality and displayed so as to improve observer performance. Performance measures of interest include diagnostic accuracy and interpretation time.

  8. 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.

  9. A strategy to optimize the thermoelectric performance in a spark plasma sintering process

    PubMed Central

    Chiu, Wan-Ting; Chen, Cheng-Lung; Chen, Yang-Yuan

    2016-01-01

    Spark plasma sintering (SPS) is currently widely applied to existing alloys as a means of further enhancing the alloys’ figure of merit. However, the determination of the optimal sintering condition is challenging in the SPS process. This report demonstrates a systematic way to independently optimize the Seebeck coefficient S and the ratio of electrical to thermal conductivity (σ/κ) and thus achieve the maximum figure of merit zT = S2(σ/κ)T. Sb2−xInxTe3 (x = 0–0.2) were chosen as examples to validate the method. Although high sintering temperature and pressure are helpful in enhancing the compactness and electrical conductivity of pressed samples, the resultant deteriorated Seebeck coefficient and increasing thermal conductivity eventually offset the benefit. We found that the optimal sintering temperature coincides with temperatures at which the maximum Seebeck coefficient begins to degrade, whereas the optimal sintering pressure coincided with the pressure at which the σ/κ ratio reaches a maximum. Based on this principle, the optimized sintering conditions were determined, and the zT of Sb1.9In0.1Te3 is raised to 0.92 at 600 K, showing an approximately 84% enhancement. This work develops a facile strategy for selecting the optimal SPS sintering condition to further enhance the zT of bulk specimens. PMID:26975209

  10. Thermoelectric generator

    DOEpatents

    Pryslak, N.E.

    1974-02-26

    A thermoelectric generator having a rigid coupling or stack'' between the heat source and the hot strap joining the thermoelements is described. The stack includes a member of an insulating material, such as ceramic, for electrically isolating the thermoelements from the heat source, and a pair of members of a ductile material, such as gold, one each on each side of the insulating member, to absorb thermal differential expansion stresses in the stack. (Official Gazette)

  11. Performance characteristics and optimal analysis of an interacting quantum dot thermoelectric refrigerator

    NASA Astrophysics Data System (ADS)

    Zhang, Yanchao; He, Jizhou; He, Xian; Xiao, Yuling

    2013-09-01

    We investigate the thermodynamic performance of a quantum-dot refrigerator consisting of a single orbital interacting quantum dot embedded between two electron reservoirs at different temperatures and chemical potentials. Based on the quantum master equation the expressions for the cooling power and the coefficient of performance are derived. The characteristic curves between the cooling power and the coefficient of performance are plotted, and the optimal regions of the performance parameters are determined. Moreover, the optimal performance parameters are calculated numerically. Finally, the influence of the Coulomb interaction and the temperature ratio on optimal performance parameters are discussed in detail. The results obtained here can provide some theoretical guidelines for the design and operation of the practical quantum-dot refrigerator. Our work is not restricted to the linear-response regime.

  12. Combustion synthesis of thermoelectric oxides

    NASA Astrophysics Data System (ADS)

    Selig, Jiri

    Thermoelectric materials can be used to convert temperature difference applied across them to a electrical energy. They can be used to recover waste heat and reuse it. Two thermoelectric materials, calcium cobaltate (Ca 1.24Co1.62O3.86) and yttrium cuprate (YCuO 2) were synthesized by two different types of combustion synthesis, Self-propagating High-temperature Synthesis (SHS) and thermal explosion. Combustion synthesis is more time and energy efficient than conventional methods of preparation of thermoelectric oxides. This work shows that combustion synthesis is a viable alternative for synthesis of thermoelectric oxides with comparable characteristics and thermoelectric performance to compounds prepared by traditional syntheses. Thermoelectric properties of calcium cobaltate were evaluated and compared to data published in recent literature. A finite element model of SHS is also developed. It can be used to study the reaction process of the synthesis in detail and can predict results of experiments. The model was validated by comparison with experimental observations.

  13. Augmentation of thermoelectric performance of VO2 thin films irradiated by 200 MeV Ag9+-ions

    NASA Astrophysics Data System (ADS)

    Khan, G. R.; Kandasami, A.; Bhat, B. A.

    2016-06-01

    Swift Heavy Ion (SHI) irradiation with 200 MeV Ag9+-ion beam at ion fluences of 1E11, 5E11, 1E12, and 5E12 for tuning of electrical transport properties of VO2 thin films fabricated by so-gel technique on alumina substrates has been demonstrated in the present paper. The point defects created by SHI irradiation modulate metal to insulator phase transition temperature, carrier concentration, carrier mobility, electrical conductivity, and Seebeck coefficient of VO2 thin films. The structural properties of the films were characterized by XRD and Raman spectroscopy and crystallite size was found to decrease upon irradiation. The atomic force microscopy revealed that the surface roughness of specimens first decreased and then increased with increasing fluence. Both resistance as well as Seebeck coefficient measurements demonstrated that all the samples exhibit metal-insulator phase transition and the transition temperatures decreases with increasing fluence. Hall effect measurements exhibited that carrier concentration increased continuously with increasing fluence which resulted in an increase of electrical conductivity by several orders of magnitude in the insulating phase. Seebeck coefficient in insulating phase remained almost constant in spite of an increase in the electrical conductivity by several orders of magnitude making SHI irradiation an alternative stratagem for augmentation of thermoelectric performance of the materials. The carrier mobility at room temperature decreased up to the beam fluence of 5E11 and then started increasing whereas Seebeck coefficient in metallic state first increased with increasing ion beam fluence up to 5E11 and thereafter decreased. Variation of these electrical transport parameters has been explained in detail.

  14. Performance management system enhancement and maintenance

    NASA Technical Reports Server (NTRS)

    Cleaver, T. G.; Ahour, R.; Johnson, B. R.

    1984-01-01

    The research described in this report concludes a two-year effort to develop a Performance Management System (PMS) for the NCC computers. PMS provides semi-automated monthly reports to NASA and contractor management on the status and performance of the NCC computers in the TDRSS program. Throughout 1984, PMS was tested, debugged, extended, and enhanced. Regular PMS monthly reports were produced and distributed. PMS continues to operate at the NCC under control of Bendix Corp. personnel.

  15. Enhancement of redox- and phase-stability of thermoelectric CaMnO{sub 3−δ} by substitution

    SciTech Connect

    Thiel, Philipp; Populoh, Sascha; Yoon, Songhak; Weidenkaff, Anke

    2015-09-15

    Redox Reactivity and structural phase transitions have a major impact on transport and me-chemical properties of thermoelectric CaMnO{sub 3−δ}. In this study series of Ca{sub 1−x}A{sub x}Mn{sub 1−y}B{sub y}O{sub 3−δ} (0≤x,y≤0.8) compounds, each with A-site (Dy{sup 3+}, Yb{sup 3+}) or B-site (Nb{sup 5+}, Ta{sup 5+} and Mo{sup 6+}, W{sup 6+}) substitution, were synthesized and crystallographically analyzed. It was found that the high-temperature oxygen content is widely independent from the substituent. Subsequently, with increasing temperature the differences in the Seebeck coefficient vanish above 1200 K. With increasing substitution the orthorhombic distortion of the perovskite-like phase increases. The orthorhombic distortion and the upper temperature limit of the stability of the orthorhombic crystal structure show an almost linear dependency. Accordingly, the mechanical stability of all-oxides thermoelectric converters at temperatures exceeding 1000 K will be increased employing materials with high substitution level and substituents inducing a high orthorhombic distortion. - Graphical abstract: Thermoelectric n-type CaMn{sub 0.98}W{sub 0.02}O{sub 3−δ}—Transport properties and expansion coefficient of: Oxygen loss (green region) and upper stability limit of the orthorhombic phase (yellow region) strongly affect the transport properties. Both features also cause lattice expansion, which leads to cracking of thermoelectric all-oxide converters. We report how the upper limit for application can be shifted to even higher temperatures. - Highlights: • Level of Mn{sup 3+} at RT determines reduction behavior of Ca{sub 1−x}A{sub x}Mn{sub 1−y}B{sub y}O{sub 3−δ} at HT. • Differences in Seebeck coefficient vanish at T>1200 K independent from substitution. • Substitution increases orthorhombicity of Ca{sub 1−x}A{sub x}Mn{sub 1−y}B{sub y}O{sub 3−δ}. • Linear dependence of orthorhombicity and phase stability. • Design guidelines for

  16. Flexible n-Type High-Performance Thermoelectric Thin Films of Poly(nickel-ethylenetetrathiolate) Prepared by an Electrochemical Method.

    PubMed

    Sun, Yuanhui; Qiu, Lin; Tang, Liangpo; Geng, Hua; Wang, Hanfu; Zhang, Fengjiao; Huang, Dazhen; Xu, Wei; Yue, Peng; Guan, Ying-Shi; Jiao, Fei; Sun, Yimeng; Tang, Dawei; Di, Chong-An; Yi, Yuanping; Zhu, Daoben

    2016-05-01

    Flexible thin films of poly(nickel-ethylenetetrathiolate) prepared by an electrochemical method display promising n-type thermoelectric properties with the highest ZT value up to 0.3 at room temperature. Coexistence of high electrical conductivity and high Seebeck coefficient in this coordination polymer is attributed to its degenerate narrow-bandgap semiconductor behavior. PMID:26928813

  17. Peripheral visual performance enhancement by neurofeedback training.

    PubMed

    Nan, Wenya; Wan, Feng; Lou, Chin Ian; Vai, Mang I; Rosa, Agostinho

    2013-12-01

    Peripheral visual performance is an important ability for everyone, and a positive inter-individual correlation is found between the peripheral visual performance and the alpha amplitude during the performance test. This study investigated the effect of alpha neurofeedback training on the peripheral visual performance. A neurofeedback group of 13 subjects finished 20 sessions of alpha enhancement feedback within 20 days. The peripheral visual performance was assessed by a new dynamic peripheral visual test on the first and last training day. The results revealed that the neurofeedback group showed significant enhancement of the peripheral visual performance as well as the relative alpha amplitude during the peripheral visual test. It was not the case in the non-neurofeedback control group, which performed the tests within the same time frame as the neurofeedback group but without any training sessions. These findings suggest that alpha neurofeedback training was effective in improving peripheral visual performance. To the best of our knowledge, this is the first study to show evidence for performance improvement in peripheral vision via alpha neurofeedback training.

  18. Practice Enhancement: Optimising Teaching Performance in Schools

    ERIC Educational Resources Information Center

    Perillo, Suzanne

    2006-01-01

    Purpose: The purpose of this paper is to show that in comparison to performance appraisal, "practice enhancement" is offered as a conceptual tool that can be used to develop strategies for reflecting on, communicating changes in and planning for excellence in teaching practice. Design/methodology/approach: The conceptual notion of practice…

  19. Female Athletes and Performance-Enhancer Usage

    ERIC Educational Resources Information Center

    Fralinger, Barbara K.; Pinto-Zipp, Genevieve; Olson, Valerie; Simpkins, Susan

    2007-01-01

    The purpose of this study was to develop a knowledge base on factors associated with performance-enhancer usage among female athletes at the high school level in order to identify markers for a future prevention-education program. The study used a pretest-only, between-subjects Likert Scale survey to rank the importance of internal and external…

  20. Enhancing Academic Performance: Issues in Target Selection.

    ERIC Educational Resources Information Center

    Hoge, Robert D.; Andrews, D. A.

    1987-01-01

    Learning of subject matter and acquisition of academically relevant skills are important goals in enhancing academic achievement in the classroom. The results of 22 experiments reviewed in this article support the validity of the academic performance targets but not classroom behavior targets. Some limitations on these conclusions are discussed.…

  1. A Revisit to High Thermoelectric Performance of Single-layer MoS2

    PubMed Central

    Jin, Zelin; Liao, Quanwen; Fang, Haisheng; Liu, Zhichun; Liu, Wei; Ding, Zhidong; Luo, Tengfei; Yang, Nuo

    2015-01-01

    Both electron and phonon transport properties of single layer MoS2 (SLMoS2) are studied. Based on first-principles calculations, the electrical conductivity of SLMoS2 is calculated by Boltzmann equations. The thermal conductivity of SLMoS2 is calculated to be as high as 116.8 Wm−1K−1 by equilibrium molecular dynamics simulations. The predicted value of ZT is as high as 0.11 at 500 K. As the thermal conductivity could be reduced largely by phonon engineering, there should be a high possibility to enhance ZT in the SLMoS2-based materials. PMID:26677953

  2. Modular Isotopic Thermoelectric Generator

    SciTech Connect

    Schock, Alfred

    1981-04-03

    Advanced RTG concepts utilizing improved thermoelectric materials and converter concepts are under study at Fairchild for DOE. The design described here is based on DOE's newly developed radioisotope heat source, and on an improved silicon-germanium material and a multicouple converter module under development at Syncal. Fairchild's assignment was to combine the above into an attractive power system for use in space, and to assess the specific power and other attributes of that design. The resultant design is highly modular, consisting of standard RTG slices, each producing ~24 watts at the desired output voltage of 28 volt. Thus, the design could be adapted to various space missions over a wide range of power levels, with little or no redesign. Each RTG slice consists of a 250-watt heat source module, eight multicouple thermoelectric modules, and standard sections of insulator, housing, radiator fins, and electrical circuit. The design makes it possible to check each thermoelectric module for electrical performance, thermal contact, leaktightness, and performance stability, after the generator is fully assembled; and to replace any deficient modules without disassembling the generator or perturbing the others. The RTG end sections provide the spring-loaded supports required to hold the free-standing heat source stack together during launch vibration. Details analysis indicates that the design offers a substantial improvement in specific power over the present generator of RTGs, using the same heat source modules. There are three copies in the file.

  3. Enhancement of thermoelectric figure of merit in β-Zn{sub 4}Sb{sub 3} by indium doping control

    SciTech Connect

    Wei, Pai-Chun E-mail: cheny2@phys.sinica.edu.tw; Hsu, Chia-Hao; Chang, Chung-Chieh; Chen, Cheng-Lung; Wu, Maw-Kuen; Chen, Yang-Yuan E-mail: cheny2@phys.sinica.edu.tw; Yang, Chun-Chuen; Chen, Jeng-Lung; Sankar, Raman; Chou, Fang-Cheng; Chen, Chi-Liang; Dong, Chung-Li; Chen, Kuei-Hsien

    2015-09-21

    We demonstrate the control of phase composition in Bridgman-grown β-Zn{sub 4}Sb{sub 3} crystals by indium doping, an effective way to overcome the difficulty of growing very pure β-Zn{sub 4}Sb{sub 3} thermoelectric material. The crystal structures are characterized by Rietveld refinement with synchrotron X-ray diffraction data. The results show an anisotropic lattice expansion in In-doped β-Zn{sub 4}Sb{sub 3} wherein the zinc atoms are partially substituted by indium ones at 36f site of R-3c symmetry. Through the elimination of ZnSb phase, all the three individual thermoelectric properties are simultaneously improved, i.e., increasing electrical conductivity and Seebeck coefficient while reducing thermal conductivity. Under an optimal In concentration (x = 0.05), pure phase β-Zn{sub 4}Sb{sub 3} crystal can be obtained, which possesses a high figure of merit (ZT) of 1.4 at 700 K.

  4. Oxide Thermoelectrics

    SciTech Connect

    Singh, David J

    2008-01-01

    Thermoelectricity in oxides, especially NaxCoO2 and related materials, is discussed from the point of view of first principles calculations and Boltzmann transport theory. The electronic structure of this material is exceptional in that it has a combination of very narrow bands and strong hybridization between metal d states and ligand p states. As shown within the framework of conventional Boltzmann transport theory, this leads to high Seebeck coefficients even at metallic carrier densities. This suggests a strategy of searching for other narrow band oxides that can be doped metallic with mobile carriers. Some possible avenues for finding such materials are suggested.

  5. Connecting thermoelectric performance and topological-insulator behavior: Bi2Te3 and Bi2Te2Se from first principles

    DOE PAGES

    Shi, Hongliang; Parker, David S.; Du, Mao-Hua; Singh, David J.

    2015-01-20

    Thermoelectric performance is of interest for numerous applications such as waste-heat recovery and solid-state energy conversion and will be seen to be closely connected to topological-insulator behavior. In this paper, we here report first-principles transport and defect calculations for Bi2Te2Se in relation to Bi2Te3. The two compounds are found to contain remarkably different electronic structures in spite of being isostructural and isoelectronic. We also discuss these results in terms of the topological-insulator characteristics of these compounds.

  6. Connecting Thermoelectric Performance and Topological-Insulator Behavior: Bi2Te3 and Bi2Te2Se from First Principles

    NASA Astrophysics Data System (ADS)

    Shi, Hongliang; Parker, David; Du, Mao-Hua; Singh, David J.

    2015-01-01

    Thermoelectric performance is of interest for numerous applications such as waste-heat recovery and solid-state energy conversion and will be seen to be closely connected to topological-insulator behavior. In this context, we here report first-principles transport and defect calculations for Bi2Te2Se in relation to Bi2Te3 . The two compounds are found to contain remarkably different electronic structures in spite of being isostructural and isoelectronic. We discuss these results in terms of the topological-insulator characteristics of these compounds.

  7. Enhanced thermoelectric performance in spark plasma textured bulk n-type BiTe{sub 2.7}Se{sub 0.3} and p-type Bi{sub 0.5}Sb{sub 1.5}Te{sub 3}

    SciTech Connect

    Bhame, Shekhar D.; Noudem, Jacques G.; Pravarthana, Dhanapal; Prellier, Wilfrid

    2013-05-27

    Bulk p and n-type bismuth tellurides were prepared using spark plasma texturization method. The texture development along the uniaxial load in the 001 direction is confirmed from both x-ray diffraction analysis and electron backscattering diffraction measurements. Interestingly, those textured samples outperform the samples prepared by conventional spark plasma sintering (SPS) leading to a reduced thermal conductivity in the ab-plane. The textured samples of n-type BiTe{sub 2.7}Se{sub 0.3} and p-type Bi{sub 0.5}Sb{sub 1.5}Te{sub 3} showed a 42% and 33% enhancement in figure of merit at room temperature, respectively, as compared to their SPS counterparts, opening the route for applications.

  8. Classification of Valleytronics in Thermoelectricity.

    PubMed

    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, Al(x)Ga(1-x)As 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

  9. 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

  10. Classification of Valleytronics in Thermoelectricity

    NASA Astrophysics Data System (ADS)

    Norouzzadeh, Payam; Vashaee, Daryoosh

    2016-03-01

    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.

  11. Transient thermoelectric supercooling: Isosceles current pulses from a response surface perspective and the performance effects of pulse cooling a heat generating mass

    NASA Astrophysics Data System (ADS)

    Piggott, Alfred J., III

    With increased public interest in protecting the environment, scientists and engineers aim to improve energy conversion efficiency. Thermoelectrics offer many advantages as thermal management technology. When compared to vapor compression refrigeration, above approximately 200 to 600 watts, cost in dollars per watt as well as COP are not advantageous for thermoelectrics. The goal of this work was to determine if optimized pulse supercooling operation could improve cooling capacity or efficiency of a thermoelectric device. The basis of this research is a thermal-electrical analogy based modeling study using SPICE. Two models were developed. The first model, a standalone thermocouple with no attached mass to be cooled. The second, a system that includes a module attached to a heat generating mass. With the thermocouple study, a new approach of generating response surfaces with characteristic parameters was applied. The current pulse height and pulse on-time was identified for maximizing Net Transient Advantage, a newly defined metric. The corresponding pulse height and pulse on-time was utilized for the system model. Along with the traditional steady state starting current of Imax, Iopt was employed. The pulse shape was an isosceles triangle. For the system model, metrics new to pulse cooling were Qc, power consumption and COP. The effects of optimized current pulses were studied by changing system variables. Further studies explored time spacing between pulses and temperature distribution in the thermoelement. It was found net Q c over an entire pulse event can be improved over Imax steady operation but not over steady I opt operation. Qc can be improved over Iopt operation but only during the early part of the pulse event. COP is reduced in transient pulse operation due to the different time constants of Qc and Pin. In some cases lower performance interface materials allow more Qc and better COP during transient operation than higher performance interface materials

  12. Mg{sub 2}Si nanocomposite converted from diatomaceous earth as a potential thermoelectric nanomaterial

    SciTech Connect

    Szczech, Jeannine R.; Jin Song

    2008-07-15

    With recent literature demonstrating enhancement of the thermoelectric performance of nanoscale materials relative to their corresponding bulk materials, methods to synthesize low-dimensional nanomaterials in large scale at low cost are needed. We demonstrate a method for preparing nanostructured dimagnesium silicide (Mg{sub 2}Si) thermoelectric materials that are nanocomposites with MgO by the reduction of diatomaceous earth (diatoms) using a gas-displacement solid state reaction with magnesium vapor. The resulting semiconducting Mg{sub 2}Si preserves the general morphology of the original diatoms and their nanosized grains at least down to the size of 30 nm. This reaction represents a possible method for the production of large quantities of low-cost nanoscale thermoelectric materials with potential for enhanced thermoelectric performance. - Graphical abstract: A nanostructured Mg{sub 2}Si and MgO nanocomposite thermoelectric material is synthesized in the Mg gas-displacement solid state reduction of SiO{sub 2} from diatomaceous earth. The resulting semiconducting Mg{sub 2}Si nanostructures preserve the original diatom morphology, with nanosized grains at least down to the size of 30 nm.

  13. Performance assessment to enhance training effectiveness.

    SciTech Connect

    Stevens-Adams, Susan Marie; Gieseler, Charles J.; Basilico, Justin Derrick; Abbott, Robert G.; Forsythe, James Chris

    2010-09-01

    Training simulators have become increasingly popular tools for instructing humans on performance in complex environments. However, the question of how to provide individualized and scenario-specific assessment and feedback to students remains largely an open question. To maximize training efficiency, new technologies are required that assist instructors in providing individually relevant instruction. Sandia National Laboratories has shown the feasibility of automated performance assessment tools, such as the Sandia-developed Automated Expert Modeling and Student Evaluation (AEMASE) software, through proof-of-concept demonstrations, a pilot study, and an experiment. In the pilot study, the AEMASE system, which automatically assesses student performance based on observed examples of good and bad performance in a given domain, achieved a high degree of agreement with a human grader (89%) in assessing tactical air engagement scenarios. In more recent work, we found that AEMASE achieved a high degree of agreement with human graders (83-99%) for three Navy E-2 domain-relevant performance metrics. The current study provides a rigorous empirical evaluation of the enhanced training effectiveness achievable with this technology. In particular, we assessed whether giving students feedback based on automated metrics would enhance training effectiveness and improve student performance. We trained two groups of employees (differentiated by type of feedback) on a Navy E-2 simulator and assessed their performance on three domain-specific performance metrics. We found that students given feedback via the AEMASE-based debrief tool performed significantly better than students given only instructor feedback on two out of three metrics. Future work will focus on extending these developments for automated assessment of teamwork.

  14. Superlattices in thermoelectric applications

    SciTech Connect

    Sofo, J.O.; Mahan, G.D. |

    1994-08-01

    The electrical conductivity, thermopower and the electronic contribution to the thermal conductivity of a superlattice, are calculated with the electric field and the thermal gradient applied parallel to the interfaces. Tunneling between quantum wells is included. The broadening of the lowest subband when the period of the superlattice is decreased produces a reduction of the thermoelectric figure of merit. However, we found that a moderate increase of the figure of merit may be expected for intermediate values of the period, due to the enhancement of the density of states produced by the superlattice structure.

  15. Maximizing the thermoelectric performance of topological insulator Bi2Te3 films in the few-quintuple layer regime

    NASA Astrophysics Data System (ADS)

    Liu, Huijun; Liang, Jinghua; Cheng, Long; Zhang, Jie; Zhang, Zhenyu

    Using first-principles calculations and Boltzmann theory, we explore the feasibility to maximize the thermoelectric figure of merit (ZT) of topological insulator Bi2Te3 films in the few-quintuple layer regime. We discover that the delicate competitions between the surface and bulk contributions, coupled with the overall quantum size effects, lead to a novel and generic non-monotonous dependence of ZT on the film thickness. In particular, when the system crosses into the topologically non-trivial regime upon increasing the film thickness, the much longer surface relaxation time associated with the robust nature of the topological surface states results in a maximal ZT value, which can be further optimized to ~2.0 under physically realistic conditions. We also reveal the appealing potential of bridging the long-standing ZT asymmetry of p- and n-type Bi2Te3 systems. These findings help to establish intricate connections between the thermoelectric materials and topological insulators.

  16. Electronic structure and thermoelectric performance of Zintl compound Sr3GaSb3: A first-principles study

    NASA Astrophysics Data System (ADS)

    Feng Shi, Qing; Li Yan, Yu; Xu Wang, Yuan

    2014-01-01

    By using first-principles method and Boltzmann theory, we simulated the thermoelectric transport properties of p-type and n-type Sr3GaSb3. It is found that the thermoelectric figure-of merit (ZT) of n-type Sr3GaSb3 is probably better than that of p-type, mainly due to its large band degeneracy. Moreover, a high ZT value of 1.74 at 850 K can be achieved for n-type Sr3GaSb3 along the yy direction, corresponding to the carrier concentration 3.5 × 1020 e cm-3. We propose that the high ZT value of experimentally synthesized p-type Sr3GaSb3 is originated from appearing of the larger number of band valley on the top of valence bands.

  17. Performance of a flight qualified, thermoelectrically temperature controlled QCM sensor with power supply, thermal controller and signal processor

    NASA Technical Reports Server (NTRS)

    Wallace, D. A.

    1980-01-01

    A thermoelectrically temperature controlled quartz crystal microbalance (QCM) system was developed for the measurement of ion thrustor generated mercury contamination on spacecraft. Meaningful flux rate measurements dictated an accurately held sensing crystal temperature despite spacecraft surface temperature variations from -35 C to +60 C over the flight temperature range. An electronic control unit was developed with magentic amplifier transformer secondary power supply, thermal control electronics, crystal temperature analog conditioning and a multiplexed 16 bit frequency encoder.

  18. Concerted Rattling in CsAg5 Te3 Leading to Ultralow Thermal Conductivity and High Thermoelectric Performance.

    PubMed

    Lin, Hua; Tan, Gangjian; Shen, Jin-Ni; Hao, Shiqiang; Wu, Li-Ming; Calta, Nicholas; Malliakas, Christos; Wang, Si; Uher, Ctirad; Wolverton, Christopher; Kanatzidis, Mercouri G

    2016-09-12

    Thermoelectric (TE) materials convert heat energy directly into electricity, and introducing new materials with high conversion efficiency is a great challenge because of the rare combination of interdependent electrical and thermal transport properties required to be present in a single material. The TE efficiency is defined by the figure of merit ZT=(S(2) σ) T/κ, where S is the Seebeck coefficient, σ is the electrical conductivity, κ is the total thermal conductivity, and T is the absolute temperature. A new p-type thermoelectric material, CsAg5 Te3 , is presented that exhibits ultralow lattice thermal conductivity (ca. 0.18 Wm(-1)  K(-1) ) and a high figure of merit of about 1.5 at 727 K. The lattice thermal conductivity is the lowest among state-of-the-art thermoelectrics; it is attributed to a previously unrecognized phonon scattering mechanism that involves the concerted rattling of a group of Ag ions that strongly raises the Grüneisen parameters of the material. PMID:27513458

  19. Concerted Rattling in CsAg5 Te3 Leading to Ultralow Thermal Conductivity and High Thermoelectric Performance.

    PubMed

    Lin, Hua; Tan, Gangjian; Shen, Jin-Ni; Hao, Shiqiang; Wu, Li-Ming; Calta, Nicholas; Malliakas, Christos; Wang, Si; Uher, Ctirad; Wolverton, Christopher; Kanatzidis, Mercouri G

    2016-09-12

    Thermoelectric (TE) materials convert heat energy directly into electricity, and introducing new materials with high conversion efficiency is a great challenge because of the rare combination of interdependent electrical and thermal transport properties required to be present in a single material. The TE efficiency is defined by the figure of merit ZT=(S(2) σ) T/κ, where S is the Seebeck coefficient, σ is the electrical conductivity, κ is the total thermal conductivity, and T is the absolute temperature. A new p-type thermoelectric material, CsAg5 Te3 , is presented that exhibits ultralow lattice thermal conductivity (ca. 0.18 Wm(-1)  K(-1) ) and a high figure of merit of about 1.5 at 727 K. The lattice thermal conductivity is the lowest among state-of-the-art thermoelectrics; it is attributed to a previously unrecognized phonon scattering mechanism that involves the concerted rattling of a group of Ag ions that strongly raises the Grüneisen parameters of the material.

  20. Enhancement of Thermoelectric Figure of Merit for Bi0.5Sb1.5Te3 by Metal Nanoparticle Decoration

    NASA Astrophysics Data System (ADS)

    Lee, Kyu-Hyoung; Kim, Hyun-Sik; Kim, Sang-Il; Lee, Eun-Sung; Lee, Sang-Mock; Rhyee, Jong-Soo; Jung, Jae-Yong; Kim, Il-Ho; Wang, Yifeng; Koumoto, Kunihito

    2012-06-01

    Introducing nanoinclusions in thermoelectric (TE) materials is expected to lower the lattice thermal conductivity by intensifying the phonon scattering effect, thus enhancing their TE figure of merit ZT. We report a novel method of fabricating Bi0.5Sb1.5Te3 nanocomposite with nanoscale metal particles by using metal acetate precursor, which is low cost and facile to scale up for mass production. Ag and Cu particles of ˜40 nm were successfully near-monodispersed at grain boundaries of Bi0.5Sb1.5Te3 matrix. The well-dispersed metal nanoparticles reduce the lattice thermal conductivity extensively, while enhancing the power factor. Consequently, ZT was enhanced by more than 25% near room temperature and by more than 300% at 520 K compared with a Bi0.5Sb1.5Te3 reference sample. The peak ZT of 1.35 was achieved at 400 K for 0.1 wt.% Cu-decorated Bi0.5Sb1.5Te3.

  1. A Monolithic Oxide-Based Transversal Thermoelectric Energy Harvester

    NASA Astrophysics Data System (ADS)

    Teichert, S.; Bochmann, A.; Reimann, T.; Schulz, T.; Dreßler, C.; Udich, S.; Töpfer, J.

    2016-03-01

    We report the fabrication and properties of a monolithic transversal thermoelectric energy harvester based on the combination of a thermoelectric oxide and a metal. The fabrication of the device is done with a ceramic multilayer technology using printing and co-firing processes. Five transversal devices were combined to a meander-like thermoelectric generator. Electrical measurements and finite element calculations were performed to characterize the resulting thermoelectric generator. A maximum experimental electrical power output of 30.2 mW at a temperature difference of {Δ }T = 208 K was found. The prepared monolithic thermoelectric generator provides at {Δ }T = 35 K sufficient energy to drive a simple electronic sensor application.

  2. Novel polymer platform for enhanced biochip performance

    NASA Astrophysics Data System (ADS)

    McEvoy, Helen M.; Blue, Robert; Kent, Nigel; Polerecky, Lubos; McDonagh, Colette; MacCraith, Brian D.

    2005-06-01

    We report the development of enhanced optical platforms for fluorescence-based biosensors. A previous analysis by us has shown that the emission of fluorescence in such a system is highly anisotropic and is preferentially emitted into the substrate over a well-defined angular range, with the result that the light is guided along the substrate via total internal reflection. However, conventional optical biosensors based on fluorescence detection typically employ a detector that is positioned either directly above or directly below the biochip. As a consequence, only a small fraction of the total emitted fluorescence is detected, which impacts adversely on sensor performance. The enhanced biosensor presented here is based on a novel, generic platform specifically designed to overcome the inherent limitations of planar substrates. The platform incorporates custom-designed optical elements, the purpose of which is to redirect the emitted fluorescence onto a detector positioned beneath the biochip. Platforms were fabricated using the polymer processing technique of microinjection moulding. In this paper we demonstrate the ability of this optical system to achieve a 80-fold luminescence capture enhancement. We also demonstrate its effectiveness as an enhanced biosensor platform by carrying out a proof of principle BSA/antiBSA competitive assay. This work has significant implications for the development of mass-producible, highly efficient optical biosensors.

  3. Use of Performance-Enhancing Substances.

    PubMed

    LaBotz, Michele; Griesemer, Bernard A

    2016-07-01

    Performance-enhancing substances (PESs) are used commonly by children and adolescents in attempts to improve athletic performance. More recent data reveal that these same substances often are used for appearance-related reasons as well. PESs include both legal over-the-counter dietary supplements and illicit pharmacologic agents. This report reviews the current epidemiology of PES use in the pediatric population, as well as information on those PESs in most common use. Concerns regarding use of legal PESs include high rates of product contamination, correlation with future use of anabolic androgenic steroids, and adverse effects on the focus and experience of youth sports participation. The physical maturation and endogenous hormone production that occur in adolescence are associated with large improvements in strength and athletic performance. For most young athletes, PES use does not produce significant gains over those seen with the onset of puberty and adherence to an appropriate nutrition and training program. PMID:27354458

  4. Improved Thermoelectric Devices: Advanced Semiconductor Materials for Thermoelectric Devices

    SciTech Connect

    2009-12-11

    Broad Funding Opportunity Announcement Project: Phononic Devices is working to recapture waste heat and convert it into usable electric power. To do this, the company is using thermoelectric devices, which are made from advanced semiconductor materials that convert heat into electricity or actively remove heat for refrigeration and cooling purposes. Thermoelectric devices resemble computer chips, and they manage heat by manipulating the direction of electrons at the nanoscale. These devices aren’t new, but they are currently too inefficient and expensive for widespread use. Phononic Devices is using a high-performance, cost-effective thermoelectric design that will improve the device’s efficiency and enable electronics manufacturers to more easily integrate them into their products.

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

    NASA Astrophysics Data System (ADS)

    Roychowdhury, Subhajit; Sandhya Shenoy, U.; Waghmare, Umesh V.; Biswas, Kanishka

    2016-05-01

    Topological crystalline insulator (TCI), Pb0.6Sn0.4Te, 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, Pb0.6Sn0.4Te, breaks the crystal mirror symmetry locally and widens electronic band gap, which is confirmed by direct electronic absorption spectroscopy and electronic structure calculations. K doping in Pb0.6Sn0.4Te 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.

  6. Thermoelectric effects in graphene nanostructures

    NASA Astrophysics Data System (ADS)

    Dollfus, Philippe; Nguyen, Viet Hung; Saint-Martin, Jérôme

    2015-04-01

    The thermoelectric properties of graphene and graphene nanostructures have recently attracted significant attention from the physics and engineering communities. In fundamental physics, the analysis of Seebeck and Nernst effects is very useful in elucidating some details of the electronic band structure of graphene that cannot be probed by conductance measurements alone, due in particular to the ambipolar nature of this gapless material. For applications in thermoelectric energy conversion, graphene has two major disadvantages. It is gapless, which leads to a small Seebeck coefficient due to the opposite contributions of electrons and holes, and it is an excellent thermal conductor. The thermoelectric figure of merit ZT of a two-dimensional (2D) graphene sheet is thus very limited. However, many works have demonstrated recently that appropriate nanostructuring and bandgap engineering of graphene can concomitantly strongly reduce the lattice thermal conductance and enhance the Seebeck coefficient without dramatically degrading the electronic conductance. Hence, in various graphene nanostructures, ZT has been predicted to be high enough to make them attractive for energy conversion. In this article, we review the main results obtained experimentally and theoretically on the thermoelectric properties of graphene and its nanostructures, emphasizing the physical effects that govern these properties. Beyond pure graphene structures, we discuss also the thermoelectric properties of some hybrid graphene structures, as graphane, layered carbon allotropes such as graphynes and graphdiynes, and graphene/hexagonal boron nitride heterostructures which offer new opportunities. Finally, we briefly review the recent activities on other atomically thin 2D semiconductors with finite bandgap, i.e. dichalcogenides and phosphorene, which have attracted great attention for various kinds of applications, including thermoelectrics.

  7. Thermoelectric effects in graphene nanostructures.

    PubMed

    Dollfus, Philippe; Hung Nguyen, Viet; Saint-Martin, Jérôme

    2015-04-10

    The thermoelectric properties of graphene and graphene nanostructures have recently attracted significant attention from the physics and engineering communities. In fundamental physics, the analysis of Seebeck and Nernst effects is very useful in elucidating some details of the electronic band structure of graphene that cannot be probed by conductance measurements alone, due in particular to the ambipolar nature of this gapless material. For applications in thermoelectric energy conversion, graphene has two major disadvantages. It is gapless, which leads to a small Seebeck coefficient due to the opposite contributions of electrons and holes, and it is an excellent thermal conductor. The thermoelectric figure of merit ZT of a two-dimensional (2D) graphene sheet is thus very limited. However, many works have demonstrated recently that appropriate nanostructuring and bandgap engineering of graphene can concomitantly strongly reduce the lattice thermal conductance and enhance the Seebeck coefficient without dramatically degrading the electronic conductance. Hence, in various graphene nanostructures, ZT has been predicted to be high enough to make them attractive for energy conversion. In this article, we review the main results obtained experimentally and theoretically on the thermoelectric properties of graphene and its nanostructures, emphasizing the physical effects that govern these properties. Beyond pure graphene structures, we discuss also the thermoelectric properties of some hybrid graphene structures, as graphane, layered carbon allotropes such as graphynes and graphdiynes, and graphene/hexagonal boron nitride heterostructures which offer new opportunities. Finally, we briefly review the recent activities on other atomically thin 2D semiconductors with finite bandgap, i.e. dichalcogenides and phosphorene, which have attracted great attention for various kinds of applications, including thermoelectrics.

  8. Enhancing neural-network performance via assortativity

    SciTech Connect

    Franciscis, Sebastiano de; Johnson, Samuel; Torres, Joaquin J.

    2011-03-15

    The performance of attractor neural networks has been shown to depend crucially on the heterogeneity of the underlying topology. We take this analysis a step further by examining the effect of degree-degree correlations - assortativity - on neural-network behavior. We make use of a method recently put forward for studying correlated networks and dynamics thereon, both analytically and computationally, which is independent of how the topology may have evolved. We show how the robustness to noise is greatly enhanced in assortative (positively correlated) neural networks, especially if it is the hub neurons that store the information.

  9. Enhancing neural-network performance via assortativity.

    PubMed

    de Franciscis, Sebastiano; Johnson, Samuel; Torres, Joaquín J

    2011-03-01

    The performance of attractor neural networks has been shown to depend crucially on the heterogeneity of the underlying topology. We take this analysis a step further by examining the effect of degree-degree correlations--assortativity--on neural-network behavior. We make use of a method recently put forward for studying correlated networks and dynamics thereon, both analytically and computationally, which is independent of how the topology may have evolved. We show how the robustness to noise is greatly enhanced in assortative (positively correlated) neural networks, especially if it is the hub neurons that store the information.

  10. Surface-dominated transport and enhanced thermoelectric figure of merit in topological insulator Bi(1.5)Sb(0.5)Te(1.7)Se(1.3).

    PubMed

    Hsiung, Te-Chih; Mou, Chung-Yu; Lee, Ting-Kuo; Chen, Yang-Yuan

    2015-01-14

    We report the observation of an order of magnitude enhancement of the thermoelectric figure of merit (ZT = 0.36) in topological insulator Bi1.5Sb0.5Te1.7Se1.3 nanowires at 300 K as compared with the bulk specimen (ZT = 0.028). The enhancement was primarily due to an order of magnitude increase in the electrical conductivity of the surface-dominated transport and thermally activated charge carriers in the nanowires. Magnetoresistance analysis revealed the presence of Dirac electrons and determined that the Fermi level was near the conduction band edge. This may be the first thermoelectric measurement of samples with a chemical potential in the gap of a topological insulator without gate tuning, and provides an opportunity to study the contribution of surface states to the Seebeck coefficient and resistivity without concern for the complex effect of band bending.

  11. 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.

  12. Enhanced thermoelectric properties of the hole-doped Bi2-xKxSr2Co2Oy ceramics

    NASA Astrophysics Data System (ADS)

    Gao, Feng; He, Qinglin; Cao, Ruijuan; Wu, Fang; Hu, Xing; Song, Hongzhang

    2015-09-01

    In this paper, the influence of K element doping on the thermoelectric properties of the Bi2-xKxSr2Co2Oy (x = 0.00, 0.05, 0.10, 0.15, and 0.20) samples prepared by the solid-state reaction method were investigated from 333 K to 973 K. It was shown that due to the p-type K doping the electrical resistivity of the doped sample can be reduced remarkably as compared with the undoped sample, especially for the optimum doped sample Bi1.9K0.1Sr2Co2Oy. The Seebeck coefficients of the K doped samples have only a slight decrease as compared with the undoped sample. As a result of the remarkable reduction of the electrical resistivity the power factor of the doped sample have a significant improvement. The thermal conductivity of the samples is depressed due to the defects caused by K doping. As an overall result, the dimensionless figure of merit (ZT) of the Bi1.9K0.1Sr2Co2Oy sample reaches a maximum value of 0.3 at 973 K, being 93% higher than that of the undoped sample.

  13. Density variations in thermoelectrics

    SciTech Connect

    Mahan, G. D.

    2000-05-15

    Equations are solved to give the variations in temperature, density, and potential, when a solid has electrical currents, heat currents, and particle diffusion. Solutions are presented in one dimension for currents down a bar. These solutions are used to calculate the efficiency of a thermoelectric refrigerator, which is optimized to give the coefficient of performance (COP). The COP depends upon the temperature difference {delta}T, but does not depend upon the density difference {delta}n between the two ends of the bar. (c) 2000 American Institute of Physics.

  14. Thermoelectric Properties of Higher Manganese Silicide Nanowires

    NASA Astrophysics Data System (ADS)

    Moore, Arden; Higgins, Jeremy; Zhou, Feng; Jin, Song; Shi, Li

    2009-03-01

    Higher manganese silicides (HMS) have a relatively high thermoelectric figure of merit (ZT) of about 0.7. HMS nanowires have been synthesized using a chemical vapor deposition method. In this work, the thermoelectric properties of individual HMS nanowires are measured and analyzed to determine the role of size effects on electron and phonon transport as well as potential ZT enhancement. Measurements of Seebeck coefficient, electrical conductivity, and thermal conductivity were performed using both suspended and substrate-based microdevices. Results show that the Seebeck coefficient of two as-synthesized 60 nm diameter nanowires between 300-400K is about 25-50% lower than that of single crystal bulk parallel to the c-axis, while the electrical conductivity values are about 25% lower than bulk single crystal in the same direction. The thermal conductivity of one 60 nm diameter nanowire at room temperature was found to be four times smaller than the bulk value along the c-axis. The large reduction in thermal conductivity and small to moderate impact on electrical transport may lead to HMS nanowires with enhanced ZT.

  15. Reach preparation enhances visual performance and appearance.

    PubMed

    Rolfs, Martin; Lawrence, Bonnie M; Carrasco, Marisa

    2013-10-19

    We investigated the impact of the preparation of reach movements on visual perception by simultaneously quantifying both an objective measure of visual sensitivity and the subjective experience of apparent contrast. Using a two-by-two alternative forced choice task, observers compared the orientation (clockwise or counterclockwise) and the contrast (higher or lower) of a Standard Gabor and a Test Gabor, the latter of which was presented during reach preparation, at the reach target location or the opposite location. Discrimination performance was better overall at the reach target than at the opposite location. Perceived contrast increased continuously at the target relative to the opposite location during reach preparation, that is, after the onset of the cue indicating the reach target. The finding that performance and appearance do not evolve in parallel during reach preparation points to a distinction with saccade preparation, for which we have shown previously there is a parallel temporal evolution of performance and appearance. Yet akin to saccade preparation, this study reveals that overall reach preparation enhances both visual performance and appearance.

  16. Benchmarking: A tool to enhance performance

    SciTech Connect

    Munro, J.F.; Kristal, J.; Thompson, G.; Johnson, T.

    1996-12-31

    The Office of Environmental Management is bringing Headquarters and the Field together to implement process improvements throughout the Complex through a systematic process of organizational learning called benchmarking. Simply stated, benchmarking is a process of continuously comparing and measuring practices, processes, or methodologies with those of other private and public organizations. The EM benchmarking program, which began as the result of a recommendation from Xerox Corporation, is building trust and removing barriers to performance enhancement across the DOE organization. The EM benchmarking program is designed to be field-centered with Headquarters providing facilitatory and integrative functions on an ``as needed`` basis. One of the main goals of the program is to assist Field Offices and their associated M&O/M&I contractors develop the capabilities to do benchmarking for themselves. In this regard, a central precept is that in order to realize tangible performance benefits, program managers and staff -- the ones closest to the work - must take ownership of the studies. This avoids the ``check the box`` mentality associated with some third party studies. This workshop will provide participants with a basic level of understanding why the EM benchmarking team was developed and the nature and scope of its mission. Participants will also begin to understand the types of study levels and the particular methodology the EM benchmarking team is using to conduct studies. The EM benchmarking team will also encourage discussion on ways that DOE (both Headquarters and the Field) can team with its M&O/M&I contractors to conduct additional benchmarking studies. This ``introduction to benchmarking`` is intended to create a desire to know more and a greater appreciation of how benchmarking processes could be creatively employed to enhance performance.

  17. Silicon-based semimetals and semiconductors for thermoelectric applications

    NASA Astrophysics Data System (ADS)

    Sun, Hui

    The direct conversion between heat and electricity can be achieved by thermoelectric devices. Thus, thermoelectricity is considered as not only an environmentally friendly substitute for compressor-based refrigerators but also a promising energy solution to harvest waste heat. State-of-the-art thermoelectric materials are often comprised of expensive tellurium or germanium elements and hence are hardly suitable for mass production. The silicon-based thermoelectrics, e.g. semimetallic CoSi and semiconducting beta -FeSi2 materials we study here, are composed of abundant elements in nature. They are also chemically stable, non-toxic, and mechanically robust. Despite the above benefits, they exhibit relatively lower efficiencies compared to state-of-the-art materials. In this dissertation, we have intended to understand the thermal and electrical transport in these materials and enhance their thermoelectric performance. CoSi possesses one of the highest power factors among thermoelectrics due to the sharp features around the Fermi level in its electronic density of states. In order to improve the performance, the effects of p-type dopants, isoelectronic substitutions, n-type dopants, and double doping were systematically studied for arc-melted CoSi samples. The results show that p-type dopants like iron and gallium and n-type dopants like nickel and palladium deteriorate the electrical properties due to the introduction of excess holes and electrons, respectively. Boron and platinum have very limited solubility in CoSi and the segregated impurity phases at grain boundaries are helpful to improve the electrical properties. The isoelectronic substitutions influence the power factor slightly; however, they result in a drastic decrease in the lattice thermal conductivity and hence an enhancement in the figure of merit. In addition, CoSi samples prepared by powder processing were investigated to further reduce the lattice thermal conductivity. Unfortunately, all the

  18. Enhancement of Perfluoropolyether Boundary Lubrication Performance

    NASA Technical Reports Server (NTRS)

    Jones, W. R., Jr.; Ajayi, O. O.; Wedeven, L. D.

    1996-01-01

    A ball bearing simulator operating under starved conditions was used to perform screening tests to evaluate the boundary lubrication performance of a branched perfluoropolyether (PFPE), K-143 AB. Several approaches to enhance boundary lubrication were studied. These included: (1) soluble boundary additives, (2) bearing surface modifications, (3) 'run-in' surface films, and (4) ceramic bearing components. In addition, results were compared with two non-perfluorinated liquid lubricant formulations. Based on these tests, the following tentative conclusions can be made: (1) Substantial improvements in boundary lubrication performance were observed with a beta-diketone boundary additive and a tricresyl phosphate (TCP) liquid surface pretreatment, (2) the use of rough Si3N4 balls (R(sub a) = 40 micro-inch) also provided increases in test duration, but with concomitant abrasive wear, (3) moderate improvements were seen with two boundary additives (a phosphine and a phosphatriazine) and a neat (100%) fluid (a carboxylic acid terminated PFPE); and small improvements with surface pretreatments with synthetic hydrocarbons, a polytetrafluoroethylene (PTFE) coating, and TiC coated 440 C and smooth Si3N4 balls (R(sub a) = 1 micro-inch), and (4) two non-PFPE lubricant formulations (a polyalphaolefin (PAO) and synthetic hydrocarbon) yielded substantial improvements.

  19. Symmetry-enhanced performance of dynamical decoupling

    SciTech Connect

    Pasini, S.; Uhrig, G. S.

    2011-10-15

    We consider a system with general decoherence and a quadratic dynamical decoupling sequence (QDD) for the coherence control of a qubit coupled to a bath of spins. We investigate the influence of the geometry and of the initial conditions of the bath on the performance of the sequence. The overall performance is quantified by a distance norm d. It is expected that d scales with {tau}, the total duration of the sequence, as {tau}{sup min{l_brace}N{sub x},N{sub z}{r_brace}+1}, where N{sub x} and N{sub z} are the number of pulses of the outer and of the inner sequence, respectively. We show both numerically and analytically that the state of the bath can boost the performance of QDD under certain conditions: The scaling of QDD for a given number of pulses can be enhanced by a factor of 2 if the bath is prepared in a highly symmetric state and if the system Hamiltonian is SU(2) invariant.

  20. Reactive barriers: hydraulic performance and design enhancements.

    PubMed

    Painter, B D M

    2004-01-01

    The remediation of contaminated ground water is a multibillion-dollar global industry. Permeable reactive barriers (PRBs) are one of the leading technologies being developed in the search for alternatives to the pump-and-treat method. Improving the hydraulic performance of these PRBs is an important part of maximizing their potential to the industry. Optimization of the hydraulic performance of a PRB can be defined in terms of finding the balance between capture, residence time, and PRB longevity that produces a minimum-cost acceptable design. Three-dimensional particle tracking was used to estimate capture zone and residence time distributions. Volumetric flow analysis was used for estimation of flow distribution across a PRB and in the identification of flow regimes that may affect the permeability or reactivity of portions of the PRB over time. Capture zone measurements extended below the base of partially penetrating PRBs and were measured upgradient from the portion of aquifer influenced by PRB emplacement. Hydraulic performance analysis of standard PRB designs confirmed previously presented research that identified the potential for significant variation in residence time and capture zone. These variations can result in the need to oversize the PRB to ensure that downgradient contaminant concentrations do not exceed imposed standards. The most useful PRB design enhancements for controlling residence time and capture variation were found to be customized downgradient gate faces, velocity equalization walls, deeper emplacement of the funnel than the gate, and careful manipulation of the hydraulic conductivity ratio between the gate and the aquifer.

  1. Improved Thermoelectric Performance of p-type Skutterudite YbxFe4-yPtySb12 (0.8 x 1, y = 1 and 0.5)

    SciTech Connect

    Cho, Jung Y; Ye, Zuxin; Tessema, Misle; Salvador, James R.; Waldo, Richard; Yang, Jiong; Zhang, Weiqing; Yang, Jihui; Cai, Wei; Wang, Hsin

    2013-01-01

    Thermoelectric performance of p-type skutterudites currently lags that of the corresponding n-type materials and improvement of this important class of materials have become the focus of considerable research effort world-wide. Recent calculations find promising band structural features in p-type skutterudite materials of the type AeFe3NiSb12 ( Ae = Ca, Sr, or Ba) which could potentially lead to excellent thermoelectric properties. Recent work on the Yb- filled analog of the these formulations (YbFe3NiSb12) however finds that the onset of intrinsic conduction at lower than expected temperatures deteriorates the performance above 500 K leading to poor performance in the temperature range of interest for automotive waste heat recovery applications. We therefore seek a way to increase the band gap in order to find a way to minimize the deleterious effects of intrinsic conduction. Here we present ab initio band structure calculations and the synthesis and thermoelectric properties of YbxFe4-yPtySb12 (0.8 x 1, y = 1 and 0.5). Ab initio calculations find that the band gap increases for YbFe3PtSb12 as compared to the Ni-containing analog, though no such increase in the band gap energy was found for as compared to YbFe3.5Ni0.5Sb12. The y = 1 samples shows a characteristic transition to intrinsic conduction with a decrease in the Seebeck coefficient at temperatures above 700 K. The increased carrier concentration in y = 0.5 virtually eliminates any evidence of intrinsic conduction and the Seebeck coefficients for these samples increase monotonically up to 750 K, resulting in power factors approaching 27 W/cm K2 at 750 K. These power factors combined with low thermal conductivity result in a ZT = 0.9 at 750 K for Yb0.95Fe3.5Pt0.5Sb12.

  2. High Temperature Thermoelectric Oxides Engineered At Multiple Length Scales For Energy Harvesting

    SciTech Connect

    Ohuchi, Fumio; Bordia, Rajendra

    2014-12-20

    Thermoelectric aspects of the processing parameters the n-type relaxors, including SrxBa1-xNb2O6 (SBN100x), Sr2Nb2O7 (SN) and SrBi2Nb2O9 (SBiN), were investigated. A solution combustion synthesis (SCS) route was devised to fabricate SBN, SN and SBiN nanoparticles with excellent phase purity. X-ray photoelectron spectroscopy (XPS) was used to deduce the local cation site occupancy, and detailed thermoelectric transport processes were investigated. Based on the identified behavior, effectiveness of pore formers on the thermoelectric performance was investigated with the goal of decreasing κ through enhanced phonon scattering while preserving the electron transport characteristics.

  3. Atomic-level cotrol of the thermoelectric properties in polytypoid nanowires

    SciTech Connect

    Andrews, Sean C.; Fardy, Melissa A.; Moore, Michael C.; Aloni, Shaoul; Zhang, Minjuan; Radmilovic, Velimir; Yang, Peidong

    2010-10-23

    Thermoelectric materials have generated interest as a means of increasing the efficiency of power generation through the scavenging of waste heat. Materials containing nanometer-sized structural and compositional features can exhibit enhanced thermoelectric performance due to the decoupling of certain electrical and thermal properties, but the extent to which these features can be controlled is often limited. Here we report a simple synthesis of M{sub 2}O{sub 3}(ZnO){sub n} (M = In, Ga, Fe) nanowires with controllable polytypoid structures, where the nanostructured features are tuned by adjusting the amount of metal precursor. After the introduction of nanometer-scale features (individual atomic layers and alloying), thermal and electrical measurements on single In{sub 2-x}Ga{sub x}O3(ZnO){sub n} nanowires reveal a simultaneous improvement in all contributing factors to the thermoelectric figure of merit, indicating successful modification of the nanowire transport properties.

  4. Understanding performance-enhancing drug use.

    PubMed

    Wang, David

    2012-09-01

    Performance-enhancing drug use is a prevalent problem in sports. It is a problem that has captured the world's attention as the media highlights story after story of athletes who have transformed their bodies over a short period of time, those who have simply defied the aging process in an attempt to prolong a career and those whose careers have been tarnished because of drug use. The baseball investigations and the Mitchell Report of 2007 opened our eyes and gave us a glimpse of a secretive underground world. This "world" is much more intelligent and sophisticated than it is given credit for. It is the goal of this article to increase the awareness of the medical provider about the types of steroids and other medications used, the influence these substances have on the athletes, and how and why they use them. PMID:23061215

  5. Understanding performance-enhancing drug use.

    PubMed

    Wang, David

    2012-09-01

    Performance-enhancing drug use is a prevalent problem in sports. It is a problem that has captured the world's attention as the media highlights story after story of athletes who have transformed their bodies over a short period of time, those who have simply defied the aging process in an attempt to prolong a career and those whose careers have been tarnished because of drug use. The baseball investigations and the Mitchell Report of 2007 opened our eyes and gave us a glimpse of a secretive underground world. This "world" is much more intelligent and sophisticated than it is given credit for. It is the goal of this article to increase the awareness of the medical provider about the types of steroids and other medications used, the influence these substances have on the athletes, and how and why they use them.

  6. Thermoelectric conversion for space nuclear power

    SciTech Connect

    Ewell, R.; Stapfer, G.

    1982-08-01

    A lightweight, high performance nuclear reactor power system can offer significant advantages for many space missions. Conceptual design has been completed for the SP-100, a system which utilizes many thermoelectric converters and is capable of delivering 100 kilowatts of electrical power. A reference design, using thermoelectric materials with an average figure of merit of 1.0 X 10/sup -3/K/sup -1/ and a reactor heat pipe temperature of 1500 K, is presented which has a mass of 2280 kg not including contingency. The sensitivity of system mass to changes in the configuration and thermoelectric material properties are presented.

  7. Thermoelectric conversion for space nuclear power

    NASA Technical Reports Server (NTRS)

    Ewell, R.; Stapfer, G.

    1982-01-01

    A lightweight, high performance nuclear reactor power system can offer significant advantages for many space missions. Conceptual design has been completed for the SP-100, a system which utilizes many thermoelectric converters and is capable of delivering 100 kilowatts of electrical power. A reference design, using thermoelectric materials with an average figure of merit of 0.001/K and a reactor heat pipe temperature of 1500 K, is presented which has a mass of 2280 kg not including contingency. The sensitivity of system mass to changes in the configuration and thermoelectric material properties are presented

  8. Monte Carlo Simulations on the Thermoelectric Transport Properties of Width-Modulated Nanowires

    NASA Astrophysics Data System (ADS)

    Zianni, X.

    2016-03-01

    We performed Monte Carlo simulations on the electron and phonon transport properties of Si nanowires with constant widths and of nanowires modulated by a constriction. We discuss and compare the transport properties and the thermoelectric efficiency in the nanowires. An overall figure of merit ( ZT) enhancement is predicted compared to the corresponding non-modulated nanowires. The ZT enhancement in thick, modulated nanowires has been found comparable to that in thin, non-modulated nanowires.

  9. 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. PMID:21882860

  10. Anomalous enhancement of the thermoelectric power in gallium-doped p-(Bi{sub 1-x}Sb{sub x}){sub 2}Te{sub 3} single crystals

    SciTech Connect

    Kulbachinskii, V. A. Kytin, V. G.; Tarasov, P. M.

    2010-04-15

    The effect of gallium on the temperature dependences (5 K {<=} T {<=} 300 K) of Seebeck coefficient {alpha}, electrical conductivity {sigma}, thermal conductivity k, and thermoelectric efficiency Z of mixed p-(Bi{sub 0.5}Sb{sub 0.5}){sub 2}Te{sub 3} semiconductor single crystals is studied. The hole concentration decreases upon gallium doping; that is, gallium causes a donor effect. The Seebeck coefficient increases anomalously, i.e., much higher than it should be at the detected decrease in the hole concentration. This leads to an enhancement of the thermoelectric power. The observed changes in the Seebeck coefficient indicate a noticeable gallium-induced change in the density of states in the valence band.

  11. Direct evidence of strong local ferroelectric ordering in a thermoelectric semiconductor

    SciTech Connect

    Aggarwal, Leena; Sekhon, Jagmeet S.; Arora, Ashima; Sheet, Goutam; Guin, Satya N.; Negi, Devendra S.; Datta, Ranjan; Biswas, Kanishka

    2014-09-15

    It is thought that the proposed new family of multi-functional materials, namely, the ferroelectric thermoelectrics may exhibit enhanced functionalities due to the coupling of the thermoelectric parameters with ferroelectric polarization in solids. Therefore, the ferroelectric thermoelectrics are expected to be of immense technological and fundamental significance. As a first step towards this direction, it is most important to identify the existing high performance thermoelectric materials exhibiting ferroelectricity. Herein, through the direct measurement of local polarization switching, we show that the recently discovered thermoelectric semiconductor AgSbSe{sub 2} has local ferroelectric ordering. Using piezo-response force microscopy, we demonstrate the existence of nanometer scale ferroelectric domains that can be switched by external electric field. These observations are intriguing as AgSbSe{sub 2} crystalizes in cubic rock-salt structure with centro-symmetric space group (Fm–3m), and therefore, no ferroelectricity is expected. However, from high resolution transmission electron microscopy measurement, we found the evidence of local superstructure formation which, we believe, leads to local distortion of the centro-symmetric arrangement in AgSbSe{sub 2} and gives rise to the observed ferroelectricity. Stereochemically active 5S{sup 2} lone-pair of Sb may also give rise to local structural distortion thereby creating ferroelectricity in AgSbSe{sub 2}.

  12. The influence of the nanostructure geometry on the thermoelectric properties

    NASA Astrophysics Data System (ADS)

    AL-Badry, Lafy F.

    2016-09-01

    We discuss the influence of nanostructure geometry on the thermoelectric properties in quantum ring consists of one QD in each arm, each QD connects with side QD. The calculations are based on the time-dependent Hamiltonian model, the steady state is considered to obtain an analytical expression for the transmission probability as a function of system energies. We employed the transmission probability to calculate the thermoelectric properties. We investigate thermoelectric properties through three configurations of this nanostructure. Figure of merit enhanced in configuration (II) when side QD connected to upper arm of quantum ring. The magnetic flux threads quantum ring. The effect of magnetic flux on the thermoelectric properties is examined.

  13. 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

    2016-03-01

    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.

  14. 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

    2016-03-01

    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. PMID:26856774

  15. Thermoelectricity in atom-sized junctions at room temperatures.

    PubMed

    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 2e(2)/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

  16. Does chemometrics enhance the performance of electroanalysis?

    PubMed

    Ni, Yongnian; Kokot, Serge

    2008-09-26

    This review explores the question whether chemometrics methods enhance the performance of electroanalytical methods. Electroanalysis has long benefited from the well-established techniques such as potentiometric titrations, polarography and voltammetry, and the more novel ones such as electronic tongues and noses, which have enlarged the scope of applications. The electroanalytical methods have been improved with the application of chemometrics for simultaneous quantitative prediction of analytes or qualitative resolution of complex overlapping responses. Typical methods include partial least squares (PLS), artificial neural networks (ANNs), and multiple curve resolution methods (MCR-ALS, N-PLS and PARAFAC). This review aims to provide the practising analyst with a broad guide to electroanalytical applications supported by chemometrics. In this context, after a general consideration of the use of a number of electroanalytical techniques with the aid of chemometrics methods, several overviews follow with each one focusing on an important field of application such as food, pharmaceuticals, pesticides and the environment. The growth of chemometrics in conjunction with electronic tongue and nose sensors is highlighted, and this is followed by an overview of the use of chemometrics for the resolution of complicated profiles for qualitative identification of analytes, especially with the use of the MCR-ALS methodology. Finally, the performance of electroanalytical methods is compared with that of some spectrophotometric procedures on the basis of figures-of-merit. This showed that electroanalytical methods can perform as well as the spectrophotometric ones. PLS-1 appears to be the method of practical choice if the %relative prediction error of approximately +/-10% is acceptable.

  17. Thermoelectric characterization of individual bismuth selenide topological insulator nanoribbons

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    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.

  18. Maximizing the thermoelectric performance of topological insulator Bi2Te3 films in the few-quintuple layer regime.

    PubMed

    Liang, Jinghua; Cheng, Long; Zhang, Jie; Liu, Huijun; Zhang, Zhenyu

    2016-04-28

    Using first-principles calculations and the Boltzmann theory, we explore the feasibility to maximize the thermoelectric figure of merit (ZT) of topological insulator Bi2Te3 films in the few-quintuple layer regime. We discover that the delicate competitions between the surface and bulk contributions, coupled with the overall quantum size effects, lead to a novel and generic non-monotonous dependence of ZT on the film thickness. In particular, when the system crosses into the topologically non-trivial regime upon increasing the film thickness, the much longer surface relaxation time associated with the robust nature of the topological surface states results in a maximal ZT value, which can be further optimized to ∼2.0 under physically realistic conditions. We also reveal the appealing potential of bridging the long-standing ZT asymmetry of p- and n-type Bi2Te3 systems. PMID:27071548

  19. Preparation of Ring-Shaped Thermoelectric Legs from PbTe Powders for Tubular Thermoelectric Modules

    NASA Astrophysics Data System (ADS)

    Schmitz, Andreas; Stiewe, Christian; Müller, Eckhard

    2013-07-01

    Waste heat recovery—for example, in automotive applications—is a major field for thermoelectric research and future application. Commercially available thermoelectric modules are based on planar structures, whereas tubular modules may have advantages for integration and performance in the field of automotive waste heat recovery. One major drawback of tubular generator designs is the necessity for ring-shaped legs made from thermoelectric material. Cutting these geometries from sintered tablets leads to considerable loss of thermoelectric material and therefore high cost. Direct sintering of ring-shaped legs or tubes of thermoelectric material is a solution to this problem. However, sintering such rings with high homogeneity and density faces some difficulties related to the mechanical properties of typical thermoelectric materials such as lead telluride (PbTe)—particularly brittleness and high coefficient of thermal expansion. This work shows a process for production of thermoelectric rings made of p- and n-doped PbTe. Long tubes of PbTe have been sintered in a current-assisted sintering process with specially designed sintering molds, coated with a diffusion barrier, and finally cut into ring-shaped slices. To demonstrate the technology, a tubular thermoelectric module has been assembled using these PbTe rings.

  20. Maximizing the thermoelectric performance of topological insulator Bi2Te3 films in the few-quintuple layer regime

    NASA Astrophysics Data System (ADS)

    Liang, Jinghua; Cheng, Long; Zhang, Jie; Liu, Huijun; Zhang, Zhenyu

    2016-04-01

    Using first-principles calculations and the Boltzmann theory, we explore the feasibility to maximize the thermoelectric figure of merit (ZT) of topological insulator Bi2Te3 films in the few-quintuple layer regime. We discover that the delicate competitions between the surface and bulk contributions, coupled with the overall quantum size effects, lead to a novel and generic non-monotonous dependence of ZT on the film thickness. In particular, when the system crosses into the topologically non-trivial regime upon increasing the film thickness, the much longer surface relaxation time associated with the robust nature of the topological surface states results in a maximal ZT value, which can be further optimized to ~2.0 under physically realistic conditions. We also reveal the appealing potential of bridging the long-standing ZT asymmetry of p- and n-type Bi2Te3 systems.Using first-principles calculations and the Boltzmann theory, we explore the feasibility to maximize the thermoelectric figure of merit (ZT) of topological insulator Bi2Te3 films in the few-quintuple layer regime. We discover that the delicate competitions between the surface and bulk contributions, coupled with the overall quantum size effects, lead to a novel and generic non-monotonous dependence of ZT on the film thickness. In particular, when the system crosses into the topologically non-trivial regime upon increasing the film thickness, the much longer surface relaxation time associated with the robust nature of the topological surface states results in a maximal ZT value, which can be further optimized to ~2.0 under physically realistic conditions. We also reveal the appealing potential of bridging the long-standing ZT asymmetry of p- and n-type Bi2Te3 systems. Electronic supplementary information (ESI) available. See DOI: 10.1039/c6nr00724d

  1. Heat Management in Thermoelectric Power Generators.

    PubMed

    Zebarjadi, M

    2016-04-01

    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.

  2. Heat Management in Thermoelectric Power Generators

    NASA Astrophysics Data System (ADS)

    Zebarjadi, M.

    2016-04-01

    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.

  3. 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

  4. Heat Management in Thermoelectric Power Generators.

    PubMed

    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

  5. Thermoelectric properties of PEDOT nanowire/PEDOT hybrids

    NASA Astrophysics Data System (ADS)

    Zhang, Kun; Qiu, Jingjing; Wang, Shiren

    2016-04-01

    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 PEDOT: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.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 PEDOT:PSS mixed with 5 vol% dimethyl sulfoxide while the low

  6. Dynamic thermoelectricity in uniform bipolar semiconductor

    NASA Astrophysics Data System (ADS)

    Volovichev, I. N.

    2016-07-01

    The theory of the dynamic thermoelectric effect has been developed. The effect lies in an electric current flowing in a closed circuit that consists of a uniform bipolar semiconductor, in which a non-uniform temperature distribution in the form of the traveling wave is created. The calculations are performed for the one-dimensional model in the quasi-neutrality approximation. It was shown that the direct thermoelectric current prevails, despite the periodicity of the thermal excitation, the circuit homogeneity and the lack of rectifier properties of the semiconductor system. Several physical reasons underlining the dynamic thermoelectric effect are found. One of them is similar to the Dember photoelectric effect, its contribution to the current flowing is determined by the difference in the electron and hole mobilities, and is completely independent of the carrier Seebeck coefficients. The dependence of the thermoelectric short circuit current magnitude on the semiconductor parameters, as well as on the temperature wave amplitude, length and velocity is studied. It is shown that the magnitude of the thermoelectric current is proportional to the square of the temperature wave amplitude. The dependence of the thermoelectric short circuit current on the temperature wave length and velocity is the nonmonotonic function. The optimum values for the temperature wave length and velocity, at which the dynamic thermoelectric effect is the greatest, have been deduced. It is found that the thermoelectric short circuit current changes its direction with decreasing the temperature wave length under certain conditions. The prospects for the possible applications of the dynamic thermoelectric effect are also discussed.

  7. Thermoelectric materials having porosity

    SciTech Connect

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

    2014-08-05

    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, the method includes providing a powder comprising a thermoelectric composition, pressing the powder, and sintering the powder to form the thermoelectric material.

  8. 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.

  9. Thermoelectric Power Conversion System Combined with LNG Vaporizer

    NASA Astrophysics Data System (ADS)

    Kambe, Mitsuru; Morita, Ryo; Omoto, Kazuyuki; Koji, Yasuhiro; Yoshida, Tatsuo; Noishiki, Koji

    A conceptual design of the thermoelectric power conversion system combined with open rack type LNG (liquefied natural gas) vaporizer to make use of cold heat of LNG is presented. The system performance analysis has been made based on the thermoelectric module performance data obtained at the cryogenic thermoelectric (CTE) test rig which could realize temperature and fluid dynamic condition of the open rack type LNG vaporizer. Conventional bismuth-telluride thermoelectric modules were tested, however, each module is encapsulated in the stainless steel container to achieve water proof. Electricity production cost evaluation of the system is also discussed.

  10. Production Well Performance Enhancement using Sonication Technology

    SciTech Connect

    Adewumi, Michael A; Ityokumbul, M Thaddeus; Watson, Robert W; Eltohami, Eltohami; Farias, Mario; Heckman, Glenn; Houlihan, Brendan; Karoor, Samata Prakash; Miller, Bruce G; Mohammed, Nazia; Olanrewaju, Johnson; Ozdemir, Mine; Rejepov, Dautmamed; Sadegh, Abdallah A; Quammie, Kevin E; Zaghloul, Jose; Hughes, W Jack; Montgomery, Thomas C

    2005-12-31

    The objective of this project was to develop a sonic well performance enhancement technology that focused on near wellbore formation damage. In order to successfully achieve this objective, a three-year project was defined. The entire project was broken into four tasks. The overall objective of all this was to foster a better understanding of the mechanisms involved in sonic energy interactions with fluid flow in porous media and adapt such knowledge for field applications. The fours tasks are: • Laboratory studies • Mathematical modeling • Sonic tool design and development • Field demonstration The project was designed to be completed in three years; however, due to budget cuts, support was only provided for the first year, and hence the full objective of the project could not be accomplished. This report summarizes what was accomplished with the support provided by the US Department of Energy. Experiments performed focused on determining the inception of cavitation, studying thermal dissipation under cavitation conditions, investigating sonic energy interactions with glass beads and oil, and studying the effects of sonication on crude oil properties. Our findings show that the voltage threshold for onset of cavitation is independent of transducer-hydrophone separation distance. In addition, thermal dissipation under cavitation conditions contributed to the mobilization of deposited paraffins and waxes. Our preliminary laboratory experiments suggest that waxes are mobilized when the fluid temperature approaches 40°C. Experiments were conducted that provided insights into the interactions between sonic wave and the fluid contained in the porous media. Most of these studies were carried out in a slim-tube apparatus. A numerical model was developed for simulating the effect of sonication in the nearwellbore region. The numerical model developed was validated using a number of standard testbed problems. However, actual application of the model for scale

  11. 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

  12. Electrostatic control of thermoelectricity in molecular junctions.

    PubMed

    Kim, Youngsang; Jeong, Wonho; Kim, Kyeongtae; Lee, Woochul; Reddy, Pramod

    2014-11-01

    Molecular junctions hold significant promise for efficient and high-power-output thermoelectric energy conversion. Recent experiments have probed the thermoelectric properties of molecular junctions. However, electrostatic control of thermoelectric properties via a gate electrode has not been possible due to technical challenges in creating temperature differentials in three-terminal devices. Here, we show that extremely large temperature gradients (exceeding 1 × 10(9) K m(-1)) can be established in nanoscale gaps bridged by molecules, while simultaneously controlling their electronic structure via a gate electrode. Using this platform, we study prototypical Au-biphenyl-4,4'-dithiol-Au and Au-fullerene-Au junctions to demonstrate that the Seebeck coefficient and the electrical conductance of molecular junctions can be simultaneously increased by electrostatic control. Moreover, from our studies of fullerene junctions, we show that thermoelectric properties can be significantly enhanced when the dominant transport orbital is located close to the chemical potential (Fermi level) of the electrodes. These results illustrate the intimate relationship between the thermoelectric properties and charge transmission characteristics of molecular junctions and should enable systematic exploration of the recent computational predictions that promise extremely efficient thermoelectric energy conversion in molecular junctions. PMID:25282046

  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. 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.

  15. Improved Performance of an Air Cooled Condenser (ACC) Using SPX Wind Guide Technology at Coal-Based Thermoelectric Power Plants

    SciTech Connect

    Ken Mortensen

    2010-12-31

    This project added a new airflow enhancement technology to an existing ACC cooling process at a selected coal power plant. Airflow parameters and efficiency improvement for the main plant cooling process using the applied technology were determined and compared with the capabilities of existing systems. The project required significant planning and pre-test execution in order to reach the required Air Cooled Condenser system configuration for evaluation. A host Power Plant ACC system had to be identified, agreement finalized, and addition of the SPX ACC Wind Guide Technology completed on that site. Design of the modification, along with procurement, fabrication, instrumentation, and installation of the new airflow enhancement technology were executed. Baseline and post-modification cooling system data was collected and evaluated. The improvement of ACC thermal performance after SPX wind guide installation was clear. Testing of the improvement indicates there is a 5% improvement in heat transfer coefficient in high wind conditions and 1% improvement at low wind speed. The benefit increased with increasing wind speed. This project was completed on schedule and within budget.

  16. Multi-scale defect engineering and interface modification for enhancement of thermoelectric properties in nanostructured bulk materials

    NASA Astrophysics Data System (ADS)

    Puneet, Pooja

    greater than six-fold improvement in the PF, and hence ZT, was achieved in polycrystalline bulk Bi samples. Our detailed studies of the effect of SPS conditions on the transport properties of polycrystalline Bi strongly suggests that surface states play a prominent role in enhancing the TE performance of Bi. Lastly, planar or two-dimensional defects were introduced by chemical exfoliation of layered chalcogenide n-type Bi2Te 3. Particularly, chemical exfoliation allows for the introduction of micro-structured scattering centers at multiple length scales while preserving the basal plane properties needed for high ZT values. Mechanical process such as, grinding, sintering and exfoliation are known to generate donor- like defects. In this method, the possible introduction of positively charged defects (TeBi antisites/Te vacancies) on the grain boundaries resulted in: i) the injection of electrons into the bulk increasing carrier concentration, and ii) a potential barrier that selectively filtered low-energy minority carriers (holes in case of n-type Bi 2Te3 samples) and thereby, shifting the bipolar (two carrier contribution) effects to higher temperatures. This effect is clearly reflected in the thermopower and thermal conductivity data. Thus, the shift in the bipolar effects results in the shift of ZT maxima to higher temperature, where peak ZT is broadened over a wide temperature range of ˜ 150 K. In addition to this, the compatibility factor of our samples exhibits smaller changes over the broad operating temperature regime, making it a good candidate for potential device design. (Abstract shortened by UMI.)

  17. Thermoelectric and Structural Properties of High-Performance In-based Skutterudites for High-Temperature Energy Recovery

    SciTech Connect

    Biswas, Krishnendu; Good, Morris S.; Roberts, Kamandi C.; Subramanian, Mas; Hendricks, Terry J.

    2011-08-14

    The temperature-dependent thermoelectric and structural properties of n-type filled skutterudites were measured from 300 K to about 650 K. In0.2Co4Sb12, and In0.2Ce0.05Yb0.1Co4Sb12 exhibited ZT values as high as 1.2 at 620 K and In0.2Ce0.15Co4Sb12 showed ZT values of ~1.4 at 675 K. The room temperature Young’s modulus, Poisson’s ratio and coefficient of thermal expansion (CTE at 473 K) of In0.2Ce0.15Co4Sb12, In0.2Co4Sb12, and In0.2Ce0.05Yb0.1Co4Sb12 compositions were found to be lower than that for the unfilled Co4Sb12 skutterudite material. It was discovered that thermal cycling of n-type In0.15Ce0.1Co4Sb12 and In0.2Ce0.17Co4Sb12 materials from 323 K to 673 K (200 cycles) actually increased their power factors by 14-36% at 510 K to 525 K without appreciably changing the Young’s modulus or the Poisson’s ratio. The transport and structural properties characterized in this work are critical to transitioning these materials into operating TE devices and systems.

  18. Printable Graphene-based Thermoelectric Device with High Temperature Capability

    NASA Astrophysics Data System (ADS)

    Li, Tian; Chen, Yanan; Drew, Dennis; Hu, Liangbing; NanomaterialsEmerging Devices Collaboration

    Thermoelectric devices are of particular interest due to their capability to convert heat into electrical power. We demonstrate the use of a Graphene-based thermoelectric device that can generate output voltages of hundreds of millivolts with an illuminating Graphene strip as the blackbody source. Our proposed device is superior for thermoelectric conversion mainly due to its high temperature capability that yields a maximum Carnot efficiency limit of 90% (referenced to room temperature) and a high Seebeck coefficient. Our device is also macroscopic with good mechanical strength and stabilized performance, making it attractive for large scale and reliable thermoelectric devices.

  19. High-temperature stability of thermoelectric Ca{sub 3}Co{sub 4}O{sub 9} thin films

    SciTech Connect

    Brinks, P.; Rijnders, G.; Huijben, M.; Van Nong, N.; Pryds, N.

    2015-04-06

    An enhanced thermal stability in thermoelectric Ca{sub 3}Co{sub 4}O{sub 9} thin films up to 550 °C in an oxygen rich environment was demonstrated by high-temperature electrical and X-ray diffraction measurements. In contrast to generally performed heating in helium gas, it is shown that an oxygen/helium mixture provides sufficient thermal contact, while preventing the previously disregarded formation of oxygen vacancies. Combining thermal cycling with electrical measurements proves to be a powerful tool to study the real intrinsic thermoelectric behaviour of oxide thin films at elevated temperatures.

  20. Silicon Germanium Quantum Well Thermoelectrics

    NASA Astrophysics Data System (ADS)

    Davidson, Anthony Lee, III

    Today's growing energy demands require new technologies to provide high efficiency clean energy. Thermoelectrics that convert heat to electrical energy directly can provide a method for the automobile industry to recover waste heat to power vehicle electronics, hence improving fuel economy. If large enough efficiencies can be obtained then the internal combustion engine could even be replaced. Exhaust temperature for automotive application range from 400 to 800 K. In this temperature range the current state of the art materials are bulk Si1-xGex alloys. By alternating layers of Si and Si1-xGex alloy device performance may be enhanced through quantum well effects and variations in material thermal properties. In this study, superlattices designed for in-plane operation with varying period and crystallinity are examined to determine the effect on electrical and thermal properties. In-plane electrical resistivity of these materials was found to be below the bulk material at a similar doping at room temperature, confirming the role of quantum wells in electron transport. As period is reduced in the structures boundary scattering limits electron propagation leading to increased resistivity. The Seebeck coefficient measured at room temperature is higher than the bulk material, additionally lending proof to the effects of quantum wells. When examining cross-plane operation the low doping in the Si layers of the device produce high resistivity resulting from boundary scattering. Thermal conductivity was measured from 77 K up to 674 K and shows little variation due to periodicity and temperature, however an order of magnitude reduction over bulk Si1-xGex is shown in all samples. A model is developed that suggests a combination of phonon dispersion effects and strong boundary scattering. Further study of the phonon dispersion effects was achieved through the examination of the heat capacity by combining thermal diffusivity with thermal conductivity. All superlattices show a