H. Shibata, Y. Makita, H. Kakemoto, Y. Tsai, S. Sakuragi, H. Katsumata, A. Obara, N. Kobayashi, S. Uekusa, T. Tsukamoto, T. Tsunoda, Y. Imai
The growth of bulk iron silicide by Horizontal Gradient Freeze (HGF) method was achieved using different growth and annealing conditions. Two types of annealing process, in-situ annealing and ex-situ annealing, were examined. Three types of samples were prepared and examined; (i) samples which were not applied any annealing processes, (ii) samples which were applied in-situ annealing, and (iii) samples which were applied both in-situ and ex-situ annealing. The influence of annealing and growth conditions upon the material qualities was examined and discussed, putting special emphasis on the structural properties and electrical properties. Results of the X-ray diffraction revealed that only the in-situ annealing was not sufficient for the peritectic reaction from /spl alpha/+/spl epsi/ eutectic to peritectic /spl beta/-phase. However, it was revealed that, if the ex-situ annealing is applied after the in-situ annealing, the condition of 900/spl deg/C for 200 hours is enough for the ex-situ annealing to obtain almost single /spl beta/-phase. It was also confirmed in the aspect of electrical properties that ex-situ annealing at 900/spl deg/C for 300 hours is enough to realize electrically semiconducting /spl beta/-FeSi/sub 2/. The sample prepared under such a condition exhibited p-type conductivity with hole concentration and hole mobility about 5.68/spl times/10/sup 17/ cm/sup -3/ and 1.36 cm/sup 2/Ns, respectively.
{"title":"Electrical properties of /spl beta/-FeSi2 bulk crystal grown by horizontal gradient freeze method","authors":"H. Shibata, Y. Makita, H. Kakemoto, Y. Tsai, S. Sakuragi, H. Katsumata, A. Obara, N. Kobayashi, S. Uekusa, T. Tsukamoto, T. Tsunoda, Y. Imai","doi":"10.1109/ICT.1996.553257","DOIUrl":"https://doi.org/10.1109/ICT.1996.553257","url":null,"abstract":"The growth of bulk iron silicide by Horizontal Gradient Freeze (HGF) method was achieved using different growth and annealing conditions. Two types of annealing process, in-situ annealing and ex-situ annealing, were examined. Three types of samples were prepared and examined; (i) samples which were not applied any annealing processes, (ii) samples which were applied in-situ annealing, and (iii) samples which were applied both in-situ and ex-situ annealing. The influence of annealing and growth conditions upon the material qualities was examined and discussed, putting special emphasis on the structural properties and electrical properties. Results of the X-ray diffraction revealed that only the in-situ annealing was not sufficient for the peritectic reaction from /spl alpha/+/spl epsi/ eutectic to peritectic /spl beta/-phase. However, it was revealed that, if the ex-situ annealing is applied after the in-situ annealing, the condition of 900/spl deg/C for 200 hours is enough for the ex-situ annealing to obtain almost single /spl beta/-phase. It was also confirmed in the aspect of electrical properties that ex-situ annealing at 900/spl deg/C for 300 hours is enough to realize electrically semiconducting /spl beta/-FeSi/sub 2/. The sample prepared under such a condition exhibited p-type conductivity with hole concentration and hole mobility about 5.68/spl times/10/sup 17/ cm/sup -3/ and 1.36 cm/sup 2/Ns, respectively.","PeriodicalId":447328,"journal":{"name":"Fifteenth International Conference on Thermoelectrics. Proceedings ICT '96","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1996-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124809420","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}
K. Fukuda, H. Imaizumi, T. Ishii, F. Toyoda, M. Yamanashi, Y. Kibayashi
Single crystals of Bi/sub 2/Te/sub 3/ and its solid solutions with Bi/sub 2/Se/sub 3/ for n type material show anisotropy of thermoelectric property. Hot-pressed materials also show the anisotropy, but it is weaker than the single crystals and the one directional polycrystals. In a hot pressed material, crystal grains orient with an orientational distribution. In this work, we compared the orientational distributions of hot-pressed materials which were made by different process conditions and attempted to lead the best procedure parameters of a hot-pressed material that give a high Z-value.
{"title":"Orientational distribution and procedure parameters in hot pressed (Bi2Te3)/sub 0.90/(Bi2Se3)/sub 0.10/","authors":"K. Fukuda, H. Imaizumi, T. Ishii, F. Toyoda, M. Yamanashi, Y. Kibayashi","doi":"10.1109/ICT.1996.553252","DOIUrl":"https://doi.org/10.1109/ICT.1996.553252","url":null,"abstract":"Single crystals of Bi/sub 2/Te/sub 3/ and its solid solutions with Bi/sub 2/Se/sub 3/ for n type material show anisotropy of thermoelectric property. Hot-pressed materials also show the anisotropy, but it is weaker than the single crystals and the one directional polycrystals. In a hot pressed material, crystal grains orient with an orientational distribution. In this work, we compared the orientational distributions of hot-pressed materials which were made by different process conditions and attempted to lead the best procedure parameters of a hot-pressed material that give a high Z-value.","PeriodicalId":447328,"journal":{"name":"Fifteenth International Conference on Thermoelectrics. Proceedings ICT '96","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1996-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125372358","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}
Thin film thermoelectric generator cells (TFTEGCs) of the Bi-Sb-Te-Se system were fabricated and their performances were investigated. The generator cells were composed of several layers of plate-modules, and each plate-module contained 15 p/n couples and was connected electrically in series or in parallel. Variations of the open circuit voltage, short circuit current and maximum output power as a function of temperature difference showed a linear relationship for the first two values, but there was a second-order relationship for the latter. The output power produced per couple and per unit temperature difference was a 3.5 nW/K couple.
{"title":"Thin film thermoelectric generator cell of Bi-Sb-Te-Se system","authors":"Ii Kim, Dong-Hi Lee","doi":"10.1109/ICT.1996.553520","DOIUrl":"https://doi.org/10.1109/ICT.1996.553520","url":null,"abstract":"Thin film thermoelectric generator cells (TFTEGCs) of the Bi-Sb-Te-Se system were fabricated and their performances were investigated. The generator cells were composed of several layers of plate-modules, and each plate-module contained 15 p/n couples and was connected electrically in series or in parallel. Variations of the open circuit voltage, short circuit current and maximum output power as a function of temperature difference showed a linear relationship for the first two values, but there was a second-order relationship for the latter. The output power produced per couple and per unit temperature difference was a 3.5 nW/K couple.","PeriodicalId":447328,"journal":{"name":"Fifteenth International Conference on Thermoelectrics. Proceedings ICT '96","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1996-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125437519","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}
Large quadrupole splittings (Q.S.) are observed in Co doped specimen, compared with other transition metal doped specimens while isomer shifts (I.S.) do not show large value. Since Q.S. is associated with the electric field gradient at nucleus of iron atom; we calculate the potential at nucleus site, assuming the interaction between LA-phonon-conduction electron. Through the calculations, it is found that electric field gradient increase with the number of phonons attached to a conduction electron (=). Accordingly large Q.S. for Co doped specimen are considered to be due to large in comparison with those for other transition metal doped specimen.
{"title":"Analysis of quadrupole splitting of transition metal doped /spl beta/-FeSi2","authors":"S. Kondo, M. Hasaka, T. Morimura","doi":"10.1109/ICT.1996.553261","DOIUrl":"https://doi.org/10.1109/ICT.1996.553261","url":null,"abstract":"Large quadrupole splittings (Q.S.) are observed in Co doped specimen, compared with other transition metal doped specimens while isomer shifts (I.S.) do not show large value. Since Q.S. is associated with the electric field gradient at nucleus of iron atom; we calculate the potential at nucleus site, assuming the interaction between LA-phonon-conduction electron. Through the calculations, it is found that electric field gradient increase with the number of phonons attached to a conduction electron (=). Accordingly large Q.S. for Co doped specimen are considered to be due to large in comparison with those for other transition metal doped specimen.","PeriodicalId":447328,"journal":{"name":"Fifteenth International Conference on Thermoelectrics. Proceedings ICT '96","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1996-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125598288","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}
This paper describes the application of the transient analysis test method to evaluate the integrity of thermal junctions in a thermoelectric (TE) assembly. The quality of thermal junctions in assemblies was measured by creating a thermal gradient in the TE modules comprising an assembly and analyzing the decay of the residual Seebeck voltage. A study was made of various junction conditions that exist between the TE module and its heatsinks which are common to most assembly techniques. Poor thermal contacts were deliberately introduced such as insufficient thermal grease, inadequate compression and improper surface finishes in test assemblies in order to simulate typical assembly defects. A direct correlation between good and inadequate thermal junctions was established and illustrated through graphic test data evaluation.
{"title":"Evaluation of thermal junction quality in thermoelectric assemblies using transient analysis technology","authors":"T. Ritzer, M.J. Nagy, R. Buist","doi":"10.1109/ICT.1996.553320","DOIUrl":"https://doi.org/10.1109/ICT.1996.553320","url":null,"abstract":"This paper describes the application of the transient analysis test method to evaluate the integrity of thermal junctions in a thermoelectric (TE) assembly. The quality of thermal junctions in assemblies was measured by creating a thermal gradient in the TE modules comprising an assembly and analyzing the decay of the residual Seebeck voltage. A study was made of various junction conditions that exist between the TE module and its heatsinks which are common to most assembly techniques. Poor thermal contacts were deliberately introduced such as insufficient thermal grease, inadequate compression and improper surface finishes in test assemblies in order to simulate typical assembly defects. A direct correlation between good and inadequate thermal junctions was established and illustrated through graphic test data evaluation.","PeriodicalId":447328,"journal":{"name":"Fifteenth International Conference on Thermoelectrics. Proceedings ICT '96","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1996-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"132055665","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}
Radiation defects in PbTe single crystals and epitaxial films induced by ion implantation of various impurities amounting to as much as 2/spl middot/10/sup 4/ /spl mu/C/cm/sup 2/ have been investigated. It has been found that the formation of point defects (for the most part, Te vacancies) running as deep as 3 /spl mu/m and more determine transport properties due to the stabilization of electron concentration at a level of 2+4/spl middot/10/sup 18/ cm/sup -3/. The data are interpreted based on the model of the quasi-local (doublet) energy level of Te vacancies in the PbTe conduction band. The formation of solid solutions accompanied by the increase of band gap was detected in PbTe thin layers implanted with Zn.
{"title":"Radiation defects induced by ion implantation as a promising method of doping semiconductor type AIVBIV films","authors":"Z. Dashevsky","doi":"10.1109/ICT.1996.553523","DOIUrl":"https://doi.org/10.1109/ICT.1996.553523","url":null,"abstract":"Radiation defects in PbTe single crystals and epitaxial films induced by ion implantation of various impurities amounting to as much as 2/spl middot/10/sup 4/ /spl mu/C/cm/sup 2/ have been investigated. It has been found that the formation of point defects (for the most part, Te vacancies) running as deep as 3 /spl mu/m and more determine transport properties due to the stabilization of electron concentration at a level of 2+4/spl middot/10/sup 18/ cm/sup -3/. The data are interpreted based on the model of the quasi-local (doublet) energy level of Te vacancies in the PbTe conduction band. The formation of solid solutions accompanied by the increase of band gap was detected in PbTe thin layers implanted with Zn.","PeriodicalId":447328,"journal":{"name":"Fifteenth International Conference on Thermoelectrics. Proceedings ICT '96","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1996-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133840301","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":null,"pages":null},"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}
Several proposed applications of thermoelectric devices in the automobile industry are reviewed. These are: exhaust gas thermoelectric generator; air conditioning (thermoelectric cooling); and microelectronics cooling using thin-film thermoelectrics. The key to the realization of these technologies is the continued development of new materials with increased thermoelectric efficiency.
{"title":"Potential applications of advanced thermoelectrics in the automobile industry","authors":"D. Morelli","doi":"10.1109/ICT.1996.553509","DOIUrl":"https://doi.org/10.1109/ICT.1996.553509","url":null,"abstract":"Several proposed applications of thermoelectric devices in the automobile industry are reviewed. These are: exhaust gas thermoelectric generator; air conditioning (thermoelectric cooling); and microelectronics cooling using thin-film thermoelectrics. The key to the realization of these technologies is the continued development of new materials with increased thermoelectric efficiency.","PeriodicalId":447328,"journal":{"name":"Fifteenth International Conference on Thermoelectrics. Proceedings ICT '96","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1996-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123827157","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}
Maximizing the rate of heat removal from the hot side of thermoelectric cooling modules is necessary to obtain optimum performance for any thermoelectric cooling device. The thickness, shape, height of fins and number of fins per inch are all important variables in a finned heat sink design. The area and thickness of the heat sink base plate relative to the area of the thermoelectric module is also important. This paper provides a means to calculate the effectiveness of these variables as they affect heat dissipation from the hot side of a thermoelectric module operated in the cooling mode. Although the focus is on cooling devices, the results of this model should be equally useful in evaluating power-generating devices.
{"title":"Influence of air heat sink geometry on the performance of thermoelectric cooling modules","authors":"W. Zheng, G. Xu","doi":"10.1109/ICT.1996.553498","DOIUrl":"https://doi.org/10.1109/ICT.1996.553498","url":null,"abstract":"Maximizing the rate of heat removal from the hot side of thermoelectric cooling modules is necessary to obtain optimum performance for any thermoelectric cooling device. The thickness, shape, height of fins and number of fins per inch are all important variables in a finned heat sink design. The area and thickness of the heat sink base plate relative to the area of the thermoelectric module is also important. This paper provides a means to calculate the effectiveness of these variables as they affect heat dissipation from the hot side of a thermoelectric module operated in the cooling mode. Although the focus is on cooling devices, the results of this model should be equally useful in evaluating power-generating devices.","PeriodicalId":447328,"journal":{"name":"Fifteenth International Conference on Thermoelectrics. Proceedings ICT '96","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"1996-03-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"117100976","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":null,"pages":null},"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}
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