Pub Date : 2005-10-24DOI: 10.1109/ICT.2005.1519899
K. Park, W. Seo, K. U. Jang, K. Ko
Cu-substituted Na(Co1-yCuy)2O4 (0≤y≤0.2) samples have been prepared using a solid-state reaction method and their thermoelectric properties studied. The electrical conductivity of Na(Co1-yCuy)2O4 decreased with increasing temperature, indicating metallic behavior. The electrical conductivity of the Cu-substituted Na(Co1-yCuy)2O4 was much higher than that of the Cu-free NaCo2O4. This is because (1) the substitution of divalent Cu 2+ for trivalent Co 3+ could increase the hole concentration of the system and (2) the Cu substitution decreased the porosity and significantly increased the grain size. In addition, the Seebeck coefficient of Na(Co1-yCuy)2O4 increased with increasing temperature and the Cu substitution led to an increase in the Seebeck coefficient. We demonstrate that extremely high power factor (3.08×10 -3 Wm -1 K -2 ) was
采用固相反应法制备了cu取代的Na(Co1-yCuy)2O4(0≤y≤0.2)样品，并对其热电性能进行了研究。随着温度的升高，Na(Co1-yCuy)2O4的电导率降低，表现出金属性质。cu取代的Na(Co1-yCuy)2O4的电导率远高于无cu的NaCo2O4。这是因为:(1)二价cu2 +取代三价co3 +可以增加体系的空穴浓度;(2)Cu取代降低了孔隙率，显著增大了晶粒尺寸。此外，Na(Co1-yCuy)2O4的Seebeck系数随温度升高而增大，Cu取代导致Seebeck系数增大。我们证明了极高的功率因数(3.08×10 -3 Wm -1 K -2)是
{"title":"Microstructure and high-temperature thermoelectric properties of Cu-doped NaCo/sub 2/O/sub 4/","authors":"K. Park, W. Seo, K. U. Jang, K. Ko","doi":"10.1109/ICT.2005.1519899","DOIUrl":"https://doi.org/10.1109/ICT.2005.1519899","url":null,"abstract":"Cu-substituted Na(Co1-yCuy)2O4 (0≤y≤0.2) samples have been prepared using a solid-state reaction method and their thermoelectric properties studied. The electrical conductivity of Na(Co1-yCuy)2O4 decreased with increasing temperature, indicating metallic behavior. The electrical conductivity of the Cu-substituted Na(Co1-yCuy)2O4 was much higher than that of the Cu-free NaCo2O4. This is because (1) the substitution of divalent Cu 2+ for trivalent Co 3+ could increase the hole concentration of the system and (2) the Cu substitution decreased the porosity and significantly increased the grain size. In addition, the Seebeck coefficient of Na(Co1-yCuy)2O4 increased with increasing temperature and the Cu substitution led to an increase in the Seebeck coefficient. We demonstrate that extremely high power factor (3.08×10 -3 Wm -1 K -2 ) was","PeriodicalId":422400,"journal":{"name":"ICT 2005. 24th International Conference on Thermoelectrics, 2005.","volume":"49 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-10-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133534899","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-06-19DOI: 10.1109/ICT.2005.1519902
Il-ho Kim, K. Park, K. Jang, S. Ur, Jung-il Lee, S. Kweon, T. Hong
Skutterudite CoSb3 doped with nickel was prepared by the vacuum induction melting in an encapsulated quartz ampoule, and its doping effects on the thermoelectric properties were investigated. Single phase δ-CoSb3 was successfully obtained by vacuum induction melting and subsequent annealing. Nickel atoms acted as donors by substituting cobalt atoms. Thermoelectric properties were improved by the appropriate annealing and doping, and they were closely related to phase transitions and dopant activation.
{"title":"Thermoelectric properties of doped CoSb/sub 3/ prepared by vacuum induction melting","authors":"Il-ho Kim, K. Park, K. Jang, S. Ur, Jung-il Lee, S. Kweon, T. Hong","doi":"10.1109/ICT.2005.1519902","DOIUrl":"https://doi.org/10.1109/ICT.2005.1519902","url":null,"abstract":"Skutterudite CoSb3 doped with nickel was prepared by the vacuum induction melting in an encapsulated quartz ampoule, and its doping effects on the thermoelectric properties were investigated. Single phase δ-CoSb3 was successfully obtained by vacuum induction melting and subsequent annealing. Nickel atoms acted as donors by substituting cobalt atoms. Thermoelectric properties were improved by the appropriate annealing and doping, and they were closely related to phase transitions and dopant activation.","PeriodicalId":422400,"journal":{"name":"ICT 2005. 24th International Conference on Thermoelectrics, 2005.","volume":"80 0","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121013025","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-06-19DOI: 10.1109/ICT.2005.1519940
Hohyun Lee, Dezhi Wang, Wenzhong Wang, Z. Ren, B. Klotz, M. Tang, Ronggui Yang, P. Gogna, Jean-Pierre Fleuiral, M. Dresselhaus, Gang Chen
In this study, we developed a nano-composite approach to make bulk materials with nanostructures that have lower thermal conductivity than their bulk alloy counterparts. Room temperature measurement results of Si/Ge composites with nano-particle shows lower thermal conductivity than that of Si/Ge composites made with micro-sized particles. For high density sample, we also observed thermal conductivity reduction without deterioration of electrical conductivity so that higher ZT than bulk alloy is achieved.
{"title":"Thermoelectric properties of Si/Ge nano-composite","authors":"Hohyun Lee, Dezhi Wang, Wenzhong Wang, Z. Ren, B. Klotz, M. Tang, Ronggui Yang, P. Gogna, Jean-Pierre Fleuiral, M. Dresselhaus, Gang Chen","doi":"10.1109/ICT.2005.1519940","DOIUrl":"https://doi.org/10.1109/ICT.2005.1519940","url":null,"abstract":"In this study, we developed a nano-composite approach to make bulk materials with nanostructures that have lower thermal conductivity than their bulk alloy counterparts. Room temperature measurement results of Si/Ge composites with nano-particle shows lower thermal conductivity than that of Si/Ge composites made with micro-sized particles. For high density sample, we also observed thermal conductivity reduction without deterioration of electrical conductivity so that higher ZT than bulk alloy is achieved.","PeriodicalId":422400,"journal":{"name":"ICT 2005. 24th International Conference on Thermoelectrics, 2005.","volume":"103 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126011319","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-06-19DOI: 10.1109/ICT.2005.1519929
H. Kaibe, I. Aoyama, M. Mukoujima, Toshio Kanda, S. Fujimoto, Toshitaka Kurosawa, H. Ishimabushi, K. Ishida, L. Rauscher, Yasuhiko Hata, S. Sano
Under NEDO project "The development for advanced thermoelectric conversion system", Komatsu Ltd. is involved in R&D for suicide, Bi-Te and their cascading modules. Aiming to 15% of conversion efficiency /spl eta/ under the hot side T/sub h/=580/spl deg/C and the cold side T/sub c/=30/spl deg/C until March, 2007, 12% as midterm target was already well attained. In the next 2 years, module designing as well as materials tuning are surely the major topics in terms of superior durability. Bi-Te module, which is established as Peltier cooler, was adjusted to be suitable for generation purpose. So far, better than 7.8% of conversion efficiency with T/sub h/=280/spl deg/C and T/sub c/=30/spl deg/C was obtained and reproducibility was also well confirmed. Komatsu started investigation for suicide materials as well as module fabrication together with this NEDO project. The performance of suicide module using n-type Mg-Si and p-type MnSi are being steadily improved due to not only the elevation of Z-values of the materials but also maturity of module fabrication technique. Then, better than 8% of efficiency has been maintained at T/sub h/=550/spl deg/C and T/sub c/=30/spl deg/C. Besides each single module, the cascading one was successfully stacked and the performance was achieved almost as expected. /spl eta/=12.1% with T/sub h/=550/spl deg/C and T/sub c/=30/spl deg/C was actually accomplished up to now.
{"title":"Development of thermoelectric generating stacked modules aiming for 15% of conversion efficiency","authors":"H. Kaibe, I. Aoyama, M. Mukoujima, Toshio Kanda, S. Fujimoto, Toshitaka Kurosawa, H. Ishimabushi, K. Ishida, L. Rauscher, Yasuhiko Hata, S. Sano","doi":"10.1109/ICT.2005.1519929","DOIUrl":"https://doi.org/10.1109/ICT.2005.1519929","url":null,"abstract":"Under NEDO project \"The development for advanced thermoelectric conversion system\", Komatsu Ltd. is involved in R&D for suicide, Bi-Te and their cascading modules. Aiming to 15% of conversion efficiency /spl eta/ under the hot side T/sub h/=580/spl deg/C and the cold side T/sub c/=30/spl deg/C until March, 2007, 12% as midterm target was already well attained. In the next 2 years, module designing as well as materials tuning are surely the major topics in terms of superior durability. Bi-Te module, which is established as Peltier cooler, was adjusted to be suitable for generation purpose. So far, better than 7.8% of conversion efficiency with T/sub h/=280/spl deg/C and T/sub c/=30/spl deg/C was obtained and reproducibility was also well confirmed. Komatsu started investigation for suicide materials as well as module fabrication together with this NEDO project. The performance of suicide module using n-type Mg-Si and p-type MnSi are being steadily improved due to not only the elevation of Z-values of the materials but also maturity of module fabrication technique. Then, better than 8% of efficiency has been maintained at T/sub h/=550/spl deg/C and T/sub c/=30/spl deg/C. Besides each single module, the cascading one was successfully stacked and the performance was achieved almost as expected. /spl eta/=12.1% with T/sub h/=550/spl deg/C and T/sub c/=30/spl deg/C was actually accomplished up to now.","PeriodicalId":422400,"journal":{"name":"ICT 2005. 24th International Conference on Thermoelectrics, 2005.","volume":"89 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114954968","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-06-19DOI: 10.1109/ICT.2005.1519891
Z. Bian, Yan Zhang, Holger Schmidt, Ali Shakouri
Thin-film thermoelectric materials offer great potential for improving the thermoelectric figure of merit ZT due to the freedom of tailoring the electron and heat transport. The characterization of these thin films is difficult because of the coexistence of the substrate, non-ideal contact, and asymmetric three-dimensional device structure. We have investigated theoretically and experimentally the transient Harman method for measuring the ZT of a thin film Si/SiGe superlattices on a silicon substrate. 3D electrothermal simulations allow us to identify the contribution of the thin film and the substrate to the transient response. On the measurement side, ringing at short times and noise can be significantly improved by using high-speed packages and electrical impedance matching. The Joule heating contribution to the thermoelectric EMF is separated from the Peltier one by the bipolar measurement. The parasitic non-ideal effects of contacts and substrate can be removed by variable thickness superlattice method.
{"title":"Thin film ZT characterization using transient Harman technique","authors":"Z. Bian, Yan Zhang, Holger Schmidt, Ali Shakouri","doi":"10.1109/ICT.2005.1519891","DOIUrl":"https://doi.org/10.1109/ICT.2005.1519891","url":null,"abstract":"Thin-film thermoelectric materials offer great potential for improving the thermoelectric figure of merit ZT due to the freedom of tailoring the electron and heat transport. The characterization of these thin films is difficult because of the coexistence of the substrate, non-ideal contact, and asymmetric three-dimensional device structure. We have investigated theoretically and experimentally the transient Harman method for measuring the ZT of a thin film Si/SiGe superlattices on a silicon substrate. 3D electrothermal simulations allow us to identify the contribution of the thin film and the substrate to the transient response. On the measurement side, ringing at short times and noise can be significantly improved by using high-speed packages and electrical impedance matching. The Joule heating contribution to the thermoelectric EMF is separated from the Peltier one by the bipolar measurement. The parasitic non-ideal effects of contacts and substrate can be removed by variable thickness superlattice method.","PeriodicalId":422400,"journal":{"name":"ICT 2005. 24th International Conference on Thermoelectrics, 2005.","volume":"99 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122559515","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-06-19DOI: 10.1109/ICT.2005.1520003
T. Kamilov, D. K. Kabilov, I. S. Samiev, A. Husanov, S. Dadamuhamedov
In this work it was informed about development of the thermoelectric radiation detector based on the multielement structures made of the polycrystalline higher manganese silicide films. The films were grown on a p-type silicon substrate with n-type silicon epitaxial layer with a thickness of about 30 /spl mu/m. For the purpose of decreasing short-circulating effects and thermal scattering of the substrate, the elements of the structures were separated by making grooves using mechanical cutting. Depth of the grooves is no more than 50 /spl mu/m. Electrical contacts to elements of the structure were made by ultrasonic bonding. Thermoelectric properties (conductivity, thermoelectric power, sensitivity and response time) of the multielement structures were investigated.
{"title":"The thermoelectric radiation detector based on the multielement structures of the higher manganese silicide films","authors":"T. Kamilov, D. K. Kabilov, I. S. Samiev, A. Husanov, S. Dadamuhamedov","doi":"10.1109/ICT.2005.1520003","DOIUrl":"https://doi.org/10.1109/ICT.2005.1520003","url":null,"abstract":"In this work it was informed about development of the thermoelectric radiation detector based on the multielement structures made of the polycrystalline higher manganese silicide films. The films were grown on a p-type silicon substrate with n-type silicon epitaxial layer with a thickness of about 30 /spl mu/m. For the purpose of decreasing short-circulating effects and thermal scattering of the substrate, the elements of the structures were separated by making grooves using mechanical cutting. Depth of the grooves is no more than 50 /spl mu/m. Electrical contacts to elements of the structure were made by ultrasonic bonding. Thermoelectric properties (conductivity, thermoelectric power, sensitivity and response time) of the multielement structures were investigated.","PeriodicalId":422400,"journal":{"name":"ICT 2005. 24th International Conference on Thermoelectrics, 2005.","volume":"24 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123024026","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-06-19DOI: 10.1109/ICT.2005.1519998
C. Stiewe, G. Karpinski, D. Platzek, H. Kaibe, E. Muller
A facility for investigating the thermal and electrical properties of a thermoelectric generator in an environment close to reality and the thermal resistance of multi-layer specimen has been constructed at DLR. Quantities such as output power and efficiency, output voltage and current, inner resistance, and overall thermal conductance can be determined under vacuum or inert gas, but also in oxidising atmosphere. The heat flow through the generator is measured via the temperature gradient in a reference block at the hot side. The cold side heat flux is measured by a commercial heat flux meter, a second reference block or a combination of both. This redundant measurement provides a sensitive indicator for systematic errors caused by incomplete thermal shielding which would lead to thermal bypasses. Comparison of our generator tests a comparison with by a similar apparatus at another institution gives evidence for good measuring accuracy. The relative error of the resulting parameters is in the range of 5%. The method of heat flow detection in the GTF can also be used for thermal resistance investigations, especially on multi-layer systems of too low thermal conductivities for appropriate measurements by laser flash.
{"title":"Evaluation of monolithic and segmented thermoelectric materials using a potentiometer-type high accuracy generator test facility","authors":"C. Stiewe, G. Karpinski, D. Platzek, H. Kaibe, E. Muller","doi":"10.1109/ICT.2005.1519998","DOIUrl":"https://doi.org/10.1109/ICT.2005.1519998","url":null,"abstract":"A facility for investigating the thermal and electrical properties of a thermoelectric generator in an environment close to reality and the thermal resistance of multi-layer specimen has been constructed at DLR. Quantities such as output power and efficiency, output voltage and current, inner resistance, and overall thermal conductance can be determined under vacuum or inert gas, but also in oxidising atmosphere. The heat flow through the generator is measured via the temperature gradient in a reference block at the hot side. The cold side heat flux is measured by a commercial heat flux meter, a second reference block or a combination of both. This redundant measurement provides a sensitive indicator for systematic errors caused by incomplete thermal shielding which would lead to thermal bypasses. Comparison of our generator tests a comparison with by a similar apparatus at another institution gives evidence for good measuring accuracy. The relative error of the resulting parameters is in the range of 5%. The method of heat flow detection in the GTF can also be used for thermal resistance investigations, especially on multi-layer systems of too low thermal conductivities for appropriate measurements by laser flash.","PeriodicalId":422400,"journal":{"name":"ICT 2005. 24th International Conference on Thermoelectrics, 2005.","volume":"61 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114190262","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-06-19DOI: 10.1109/ICT.2005.1519977
N. Takhashi, M. Terui, N. Ueda, M. Takeda
Mixed crystals of divalent hexaboride (CaB/sub 6/ and SrB/sub 6/) were prepared and their thermoelectric properties were measured. Seebeck coefficient and electrical conductivity of the mixed crystals were intermediate between those of CaB/sub 6/ and SrB/sub 6/ single phase. Thermal conductivities of the mixed crystals were lower than the both single phases. As a consequence, highest figure-of-merit was obtained at the vicinity of Ca/sub 0.5/Sr/sub 0.5/B/sub 6/, indicating that such a mixed crystallization using two or more hexaborides is effective to improve thermoelectric performance of these materials. For further improvement in their thermoelectric performance, the origin of charge carrier should be elucidated to control the electric properties. Rietveld analysis performed on X-ray diffraction data for CaB/sub 6/ revealed that there is a deficiency of boron in the sintered specimen. The boron deficiency appears to be one of possible origins of charge carrier.
{"title":"Reduction of thermal conductivity and origin of carrier in alkaline-earth hexaborides","authors":"N. Takhashi, M. Terui, N. Ueda, M. Takeda","doi":"10.1109/ICT.2005.1519977","DOIUrl":"https://doi.org/10.1109/ICT.2005.1519977","url":null,"abstract":"Mixed crystals of divalent hexaboride (CaB/sub 6/ and SrB/sub 6/) were prepared and their thermoelectric properties were measured. Seebeck coefficient and electrical conductivity of the mixed crystals were intermediate between those of CaB/sub 6/ and SrB/sub 6/ single phase. Thermal conductivities of the mixed crystals were lower than the both single phases. As a consequence, highest figure-of-merit was obtained at the vicinity of Ca/sub 0.5/Sr/sub 0.5/B/sub 6/, indicating that such a mixed crystallization using two or more hexaborides is effective to improve thermoelectric performance of these materials. For further improvement in their thermoelectric performance, the origin of charge carrier should be elucidated to control the electric properties. Rietveld analysis performed on X-ray diffraction data for CaB/sub 6/ revealed that there is a deficiency of boron in the sintered specimen. The boron deficiency appears to be one of possible origins of charge carrier.","PeriodicalId":422400,"journal":{"name":"ICT 2005. 24th International Conference on Thermoelectrics, 2005.","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130411940","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-06-19DOI: 10.1109/ICT.2005.1519994
Ali Shakouri
Key characteristics of thermoelectric, ballistic thermionic and quasi diffusive thermionic energy converters are compared. First, the main assumptions used to derive the linear Boltzmann transport equations for electrons are examined and the possibility that a higher order transport coefficient may become relevant is discussed. In the linear transport regime, there is a fundamental trade off between high Seebeck coefficient and high electrical conductivity for bulk materials and for many multilayer structures due to the interplay between electronic density-of-states (DOS) and electron group velocity and also due to the shape of DOS versus energy curve deep inside a band. While low dimensional structures alter the density-of-states, a similar trade off still exists. If large barrier heights and high doping concentrations could be achieved solid-state thermionic energy converters would be able to alleviate this trade off, thereby achieving a very high thermoelectric power factor. For this to occur, the electron transverse momentum perpendicular to heterostructure barriers must not be conserved. This can be achieved with non-planar structures or with embedded nanostructures. Finally, a comparison between thermoelectric/thermionic devices and thermophotovoltaic energy converters shows a difference in the average energy of the emitted hot carriers due to the difference between electronic and photonic density-of-states in the reservoirs. The use of both electrons and photons from a hot reservoir or the engineering of the reservoir density-of-states may provide additional means to achieve higher efficiency in energy conversion devices and to approach the limit given by the entropy generation more easily.
{"title":"Thermoelectric, thermionic and thermophotovoltaic energy conversion","authors":"Ali Shakouri","doi":"10.1109/ICT.2005.1519994","DOIUrl":"https://doi.org/10.1109/ICT.2005.1519994","url":null,"abstract":"Key characteristics of thermoelectric, ballistic thermionic and quasi diffusive thermionic energy converters are compared. First, the main assumptions used to derive the linear Boltzmann transport equations for electrons are examined and the possibility that a higher order transport coefficient may become relevant is discussed. In the linear transport regime, there is a fundamental trade off between high Seebeck coefficient and high electrical conductivity for bulk materials and for many multilayer structures due to the interplay between electronic density-of-states (DOS) and electron group velocity and also due to the shape of DOS versus energy curve deep inside a band. While low dimensional structures alter the density-of-states, a similar trade off still exists. If large barrier heights and high doping concentrations could be achieved solid-state thermionic energy converters would be able to alleviate this trade off, thereby achieving a very high thermoelectric power factor. For this to occur, the electron transverse momentum perpendicular to heterostructure barriers must not be conserved. This can be achieved with non-planar structures or with embedded nanostructures. Finally, a comparison between thermoelectric/thermionic devices and thermophotovoltaic energy converters shows a difference in the average energy of the emitted hot carriers due to the difference between electronic and photonic density-of-states in the reservoirs. The use of both electrons and photons from a hot reservoir or the engineering of the reservoir density-of-states may provide additional means to achieve higher efficiency in energy conversion devices and to approach the limit given by the entropy generation more easily.","PeriodicalId":422400,"journal":{"name":"ICT 2005. 24th International Conference on Thermoelectrics, 2005.","volume":"11 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129279784","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2005-06-19DOI: 10.1109/ICT.2005.1519893
J. Sharp, A. Thompson, L. Trahey, A. Stacy
Numerous groups are studying nanowires of Bi/Sb and [Bi/Sb]2[Te/Se]3 as possible high ZT materials. Relative to the corresponding bulk compositions, it is feasible that nanowires will yield both improved electrical properties and reduced thermal conductivity. The measurement of nanowire properties is difficult and various approaches should be considered. We are attempting to infer the thermoelectric transport properties of nanowire arrays by making and testing miniature couples. The couples contain a nanowire array leg and a bulk material leg, and we measure AC resistance, DC voltage, ∆T and Seebeck coefficient. Motivation A growing body of theoretical and experimental work suggests that greater thermoelectric performance might be found in nanostructured, low-dimensional materials. [1] Many of these studies have focused on superlattices, which offer the opportunity for precise experimental control and relatively straightforward modeling. From the viewpoint of
{"title":"Measurement of thermoelectric nanowire array properties","authors":"J. Sharp, A. Thompson, L. Trahey, A. Stacy","doi":"10.1109/ICT.2005.1519893","DOIUrl":"https://doi.org/10.1109/ICT.2005.1519893","url":null,"abstract":"Numerous groups are studying nanowires of Bi/Sb and [Bi/Sb]2[Te/Se]3 as possible high ZT materials. Relative to the corresponding bulk compositions, it is feasible that nanowires will yield both improved electrical properties and reduced thermal conductivity. The measurement of nanowire properties is difficult and various approaches should be considered. We are attempting to infer the thermoelectric transport properties of nanowire arrays by making and testing miniature couples. The couples contain a nanowire array leg and a bulk material leg, and we measure AC resistance, DC voltage, ∆T and Seebeck coefficient. Motivation A growing body of theoretical and experimental work suggests that greater thermoelectric performance might be found in nanostructured, low-dimensional materials. [1] Many of these studies have focused on superlattices, which offer the opportunity for precise experimental control and relatively straightforward modeling. From the viewpoint of","PeriodicalId":422400,"journal":{"name":"ICT 2005. 24th International Conference on Thermoelectrics, 2005.","volume":"87 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-06-19","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123951288","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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