K. Stokes, T. Tritt, W. Fuller-Mora, A. Ehrlich, R. Jacobsen
We have measured the electrical resistivity and thermoelectric power of commercial vapor-grown carbon fibers and fiber composites from 4 K to 300 K. Post-growth heat treatment decreased the resistivity and moderately increased the magnitude of the thermopower. Thermoelectric measurements on fiber composites showed that the host material altered the resistivity but had little effect on the thermopower. Thermopower data suggest that the fibers in the composite material have a smaller degree of graphitization than isolated fibers.
{"title":"Electronic transport properties of highly conducting vapor-grown carbon fiber composites","authors":"K. Stokes, T. Tritt, W. Fuller-Mora, A. Ehrlich, R. Jacobsen","doi":"10.1109/ICT.1996.553284","DOIUrl":"https://doi.org/10.1109/ICT.1996.553284","url":null,"abstract":"We have measured the electrical resistivity and thermoelectric power of commercial vapor-grown carbon fibers and fiber composites from 4 K to 300 K. Post-growth heat treatment decreased the resistivity and moderately increased the magnitude of the thermopower. Thermoelectric measurements on fiber composites showed that the host material altered the resistivity but had little effect on the thermopower. Thermopower data suggest that the fibers in the composite material have a smaller degree of graphitization than isolated fibers.","PeriodicalId":447328,"journal":{"name":"Fifteenth International Conference on Thermoelectrics. Proceedings ICT '96","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1996-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"129046903","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}
Various properties which influence zT can be improved by using modern technology for creation special submicron structures inside homogeneous thermoelectrics. Barriers for electrons with /spl epsiv/100 is electron gas in vacuum due to full absence of lattice thermal conductivity. Even after taking into account the losses due to radiation and electrical lead to emitter the thermionic converter can have zT/spl ges/20. In 1992 V. Nemchinsky and I presented to XI Int. Conf. on Thermoelectrics (Arlington, Texas) a paper [1] based on our calculations published in 70-ths in the Russian Confidential Journal on Energy Conversion. We discussed possibility to increase the figure of merit (zT) by introducing into a TE material special barriers for low energy electrons to increase Heltier coefficient (II=/spl alpha/T) that is entropy current accompanying the charge current. But, neither V Nemchinsky nor I could attend ICT92. This year I am in a position to come back to the discussion of the problem: how to increase zT by using new microelectronics technology for goal-directed improvements of homogeneous TE materials?.
{"title":"Possible ways for efficiency improvement of thermoelectric materials","authors":"B. Moyzhes","doi":"10.1109/ICT.1996.553289","DOIUrl":"https://doi.org/10.1109/ICT.1996.553289","url":null,"abstract":"Various properties which influence zT can be improved by using modern technology for creation special submicron structures inside homogeneous thermoelectrics. Barriers for electrons with /spl epsiv/</spl mu/ can be used to increase thermopower. Modulation doping can be used to increase mobility. Due to diffusion these structures can be used only in materials for TE refrigeration especially Be/sub 1-x/Sb/sub x/ alloys. At high T the best thermoelectrics with zT>100 is electron gas in vacuum due to full absence of lattice thermal conductivity. Even after taking into account the losses due to radiation and electrical lead to emitter the thermionic converter can have zT/spl ges/20. In 1992 V. Nemchinsky and I presented to XI Int. Conf. on Thermoelectrics (Arlington, Texas) a paper [1] based on our calculations published in 70-ths in the Russian Confidential Journal on Energy Conversion. We discussed possibility to increase the figure of merit (zT) by introducing into a TE material special barriers for low energy electrons to increase Heltier coefficient (II=/spl alpha/T) that is entropy current accompanying the charge current. But, neither V Nemchinsky nor I could attend ICT92. This year I am in a position to come back to the discussion of the problem: how to increase zT by using new microelectronics technology for goal-directed improvements of homogeneous TE materials?.","PeriodicalId":447328,"journal":{"name":"Fifteenth International Conference on Thermoelectrics. Proceedings ICT '96","volume":"101 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1996-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"116361823","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}
For at least thirty years most of the generic features desirable in a material to have potential for a high thermoelectric figure of merit have been known and generally not disputed. Most of these involve some aspect of the electronic structure. The latter can be measured or at least qualitatively evaluated using traditional transport and fermiology experiments. These include temperature dependent electrical resistivity, low and high field Hall effect and magnetoresistance, and the Shubnikov-de Haas (or equivalently de Haas-van Alphen) effect. In this paper the theoretical basis for this kind of an evaluation will be given, with emphasis on the semimetallic class of materials where most thermoelectrics are found but which present their own problems. The four experimental techniques mentioned above will be described and some of the subtleties of the data reduction and analysis illustrated.
{"title":"Electronic structure of semimetals from transport and fermiology experiments","authors":"A. Ehrlich, D. J. Gillespie","doi":"10.1109/ICT.1996.553513","DOIUrl":"https://doi.org/10.1109/ICT.1996.553513","url":null,"abstract":"For at least thirty years most of the generic features desirable in a material to have potential for a high thermoelectric figure of merit have been known and generally not disputed. Most of these involve some aspect of the electronic structure. The latter can be measured or at least qualitatively evaluated using traditional transport and fermiology experiments. These include temperature dependent electrical resistivity, low and high field Hall effect and magnetoresistance, and the Shubnikov-de Haas (or equivalently de Haas-van Alphen) effect. In this paper the theoretical basis for this kind of an evaluation will be given, with emphasis on the semimetallic class of materials where most thermoelectrics are found but which present their own problems. The four experimental techniques mentioned above will be described and some of the subtleties of the data reduction and analysis illustrated.","PeriodicalId":447328,"journal":{"name":"Fifteenth International Conference on Thermoelectrics. Proceedings ICT '96","volume":"130 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1996-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127100590","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}
Advances in theoretical understanding, numerical algorithms and computing technology have made practical the determination of electronic, vibrational and other properties from first principles, even for complex materials like advanced thermoelectrics. These approaches require a minimum of experimental input, typically only composition and crystal structure. As such they may be viewed as a new window on the materials, which in combination with experiment may lead to new insights and better understanding of the variation of properties with variables like composition. This may then lead to more efficient optimization of thermoelectric materials and help in searches for new materials. This paper illustrates how theory is being applied in the search for high ZT thermoelectrics, mostly through examples.
{"title":"Electronic and vibrational properties of skutterudites","authors":"D. J. Singh, L. Nordstrom, W. Pickett, J. Feldman","doi":"10.1109/ICT.1996.553262","DOIUrl":"https://doi.org/10.1109/ICT.1996.553262","url":null,"abstract":"Advances in theoretical understanding, numerical algorithms and computing technology have made practical the determination of electronic, vibrational and other properties from first principles, even for complex materials like advanced thermoelectrics. These approaches require a minimum of experimental input, typically only composition and crystal structure. As such they may be viewed as a new window on the materials, which in combination with experiment may lead to new insights and better understanding of the variation of properties with variables like composition. This may then lead to more efficient optimization of thermoelectric materials and help in searches for new materials. This paper illustrates how theory is being applied in the search for high ZT thermoelectrics, mostly through examples.","PeriodicalId":447328,"journal":{"name":"Fifteenth International Conference on Thermoelectrics. Proceedings ICT '96","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1996-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127205643","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}
The dependence of thermoelectric properties on the texture layer thickness was investigated. The electric and thermal conductivities decrease is caused by decrease of texture layer thickness. Seebeck coefficient and figure of merit remain constant.
{"title":"Texture influence on the forming of thermoelectric properties of pressed semiconductors","authors":"L. Anatychuk, S. V. Kosyachenko, S. V. Melnichuk","doi":"10.1109/ICT.1996.553292","DOIUrl":"https://doi.org/10.1109/ICT.1996.553292","url":null,"abstract":"The dependence of thermoelectric properties on the texture layer thickness was investigated. The electric and thermal conductivities decrease is caused by decrease of texture layer thickness. Seebeck coefficient and figure of merit remain constant.","PeriodicalId":447328,"journal":{"name":"Fifteenth International Conference on Thermoelectrics. Proceedings ICT '96","volume":"35 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1996-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122703303","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}
Mg/sub 2/Si/sub 1-x/Sn/sub x/ solid solutions with (0/spl les/x/spl les/0.4) were prepared by mechanical alloying and subsequent hot-pressing. It was found that the alloying process during milling develops in one of two different directions. The first one leads to the nominal composition with only a small amount of iron impurities resulting from wear of the milling media. In the second route-which only occurs in the presence of Sn-an abrasive phase is formed and the Fe content may increase up to 50 at%. The Fe is bound in FeSi and consequently, the solid solution has a lack of Si. The hot-pressing was performed at a temperature smaller than the peritectic temperature of the quasibinary Mg/sub 2/Si-Mg/sub 2/Sn system. A decomposition of the solid solutions occurs, which suggest changes on the miscibility gap in published phase diagrams. However, some transport measurements on the multiphase materials were performed, which revealed lower mobility values and lattice thermal conductivities compared to values published in the literature for single crystalline materials. The mobility of our materials was found to be independent from composition whereas the thermal conductivity decreases with increasing Sn content.
{"title":"Mechanically alloyed Mg2Si/sub 1-x/Snx solid solutions as thermoelectric materials","authors":"M. Riffel, J. Schilz","doi":"10.1109/ICT.1996.553275","DOIUrl":"https://doi.org/10.1109/ICT.1996.553275","url":null,"abstract":"Mg/sub 2/Si/sub 1-x/Sn/sub x/ solid solutions with (0/spl les/x/spl les/0.4) were prepared by mechanical alloying and subsequent hot-pressing. It was found that the alloying process during milling develops in one of two different directions. The first one leads to the nominal composition with only a small amount of iron impurities resulting from wear of the milling media. In the second route-which only occurs in the presence of Sn-an abrasive phase is formed and the Fe content may increase up to 50 at%. The Fe is bound in FeSi and consequently, the solid solution has a lack of Si. The hot-pressing was performed at a temperature smaller than the peritectic temperature of the quasibinary Mg/sub 2/Si-Mg/sub 2/Sn system. A decomposition of the solid solutions occurs, which suggest changes on the miscibility gap in published phase diagrams. However, some transport measurements on the multiphase materials were performed, which revealed lower mobility values and lattice thermal conductivities compared to values published in the literature for single crystalline materials. The mobility of our materials was found to be independent from composition whereas the thermal conductivity decreases with increasing Sn content.","PeriodicalId":447328,"journal":{"name":"Fifteenth International Conference on Thermoelectrics. Proceedings ICT '96","volume":"61 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1996-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131090270","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}
Factors, which promote microminiaturization of cooling modules have been considered. Results of thermoelectric cooler investigations are presented taking into account all classical factors: electrical and heat resistance of a commutation, contact resistance, heat resistance of heat transfers, all kinds of thermoelectric effects, temperature dependencies of material properties, etc. The influence of all factors on cooling efficiency is analyzed. New factors, which can have influence on a module work, namely strong electric field, large temperature gradient, size effects, and diffusion processes are considered. The influence on microminiaturization and conditions for these factors actions are analyzed. A common analysis for microminiaturization limits and a prognosis of thermoelectric modules development is presented.
{"title":"Physical principles of microminiaturization in thermoelectricity","authors":"L. Anatychuk, O. Luste","doi":"10.1109/ICT.1996.553318","DOIUrl":"https://doi.org/10.1109/ICT.1996.553318","url":null,"abstract":"Factors, which promote microminiaturization of cooling modules have been considered. Results of thermoelectric cooler investigations are presented taking into account all classical factors: electrical and heat resistance of a commutation, contact resistance, heat resistance of heat transfers, all kinds of thermoelectric effects, temperature dependencies of material properties, etc. The influence of all factors on cooling efficiency is analyzed. New factors, which can have influence on a module work, namely strong electric field, large temperature gradient, size effects, and diffusion processes are considered. The influence on microminiaturization and conditions for these factors actions are analyzed. A common analysis for microminiaturization limits and a prognosis of thermoelectric modules development is presented.","PeriodicalId":447328,"journal":{"name":"Fifteenth International Conference on Thermoelectrics. Proceedings ICT '96","volume":"361 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1996-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131406374","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}
The investigation results of rational fields of single- and two-stage thermoelectric cooling module use, in the context of their energetic efficiency and economical utility in refrigeration applications, are presented by the authors.
从单级和双级热电制冷模块在制冷应用中的能量效率和经济效用的角度出发，对其合理应用领域进行了调查。
{"title":"Rational conditions and prospects for two-stage cooling modules use","authors":"L. Anatychuk, L. Vikhor, K. Misawa, N. Suzuki","doi":"10.1109/ICT.1996.553321","DOIUrl":"https://doi.org/10.1109/ICT.1996.553321","url":null,"abstract":"The investigation results of rational fields of single- and two-stage thermoelectric cooling module use, in the context of their energetic efficiency and economical utility in refrigeration applications, are presented by the authors.","PeriodicalId":447328,"journal":{"name":"Fifteenth International Conference on Thermoelectrics. Proceedings ICT '96","volume":"48 8","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1996-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132984266","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}
The main advantage of thermoelectricity compared to conventional techniques of refrigeration and electricity generation lies in the absence of mechanical parts such as motors and compressors. Free convection based exchangers yield maximal safety due to the absence of fan or pump. We describe an electricity generating thermoelectric unit of the above type; it is designed for a small nuclear-powered submarine suitable for deep sea oil prospection. The purpose of the unit is to power an alarm system in case of reactor failure.
{"title":"Free convection and electrical generation with thermoelectrics","authors":"J. Buffet","doi":"10.1109/ICT.1996.553512","DOIUrl":"https://doi.org/10.1109/ICT.1996.553512","url":null,"abstract":"The main advantage of thermoelectricity compared to conventional techniques of refrigeration and electricity generation lies in the absence of mechanical parts such as motors and compressors. Free convection based exchangers yield maximal safety due to the absence of fan or pump. We describe an electricity generating thermoelectric unit of the above type; it is designed for a small nuclear-powered submarine suitable for deep sea oil prospection. The purpose of the unit is to power an alarm system in case of reactor failure.","PeriodicalId":447328,"journal":{"name":"Fifteenth International Conference on Thermoelectrics. Proceedings ICT '96","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1996-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133468647","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}
D. Compton, A. Leitch, J. Neethling, V. V. Kozyrkov
This paper reports on a structural investigation of the ternary compound TiNiSn, prepared as a thin film by electron beam deposition of a sandwich structure comprising individual layers of Ti, Ni and Sn. The effect of annealing the compound at 800/spl deg/C for times up to 72 hours was investigated. X-ray diffraction revealed the formation of TiNi/sub 2/Sn after 6 hours of annealing. The excess of Ni in the deposited structure (confirmed by EDS) resulted in the first phase of TiNiSn not being present and a shift in the lattice parameter of second phase TiNi/sub 2/Sn.
{"title":"A microstructural analysis of thin film TiNiSn","authors":"D. Compton, A. Leitch, J. Neethling, V. V. Kozyrkov","doi":"10.1109/ICT.1996.553533","DOIUrl":"https://doi.org/10.1109/ICT.1996.553533","url":null,"abstract":"This paper reports on a structural investigation of the ternary compound TiNiSn, prepared as a thin film by electron beam deposition of a sandwich structure comprising individual layers of Ti, Ni and Sn. The effect of annealing the compound at 800/spl deg/C for times up to 72 hours was investigated. X-ray diffraction revealed the formation of TiNi/sub 2/Sn after 6 hours of annealing. The excess of Ni in the deposited structure (confirmed by EDS) resulted in the first phase of TiNiSn not being present and a shift in the lattice parameter of second phase TiNi/sub 2/Sn.","PeriodicalId":447328,"journal":{"name":"Fifteenth International Conference on Thermoelectrics. Proceedings ICT '96","volume":"1 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1996-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"130644193","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}
京公网安备 11010802042870号
京ICP备2023020795号-1
扫码关注我们
求助内容：
应助结果提醒方式：