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Volume 116, Issue 3
Displaying 1-18 of 18 articles from this issue
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Kenji Matsuura1996 Volume 116 Issue 3 Pages 195
Published: February 20, 1996
Released on J-STAGE: July 15, 2008
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I. Principles of Thermoelectric ConversionsTokio Ohta1996 Volume 116 Issue 3 Pages 196-201
Published: February 20, 1996
Released on J-STAGE: July 15, 2008
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II. Materials and Processing Technologies for Improving Thermo- electric Figure of Merit ValuesKakuei Matsubara1996 Volume 116 Issue 3 Pages 202-206
Published: February 20, 1996
Released on J-STAGE: July 15, 2008
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III. Thremoelectric Energy Conversion SystemsTakenobu Kajikawa1996 Volume 116 Issue 3 Pages 207-211
Published: February 20, 1996
Released on J-STAGE: July 15, 2008
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Yukihiro Isoda, Yoshikazu Shinohara, Yoshio Imai, Isao Albert Nishida1996 Volume 116 Issue 3 Pages 212-217
Published: February 20, 1996
Released on J-STAGE: July 15, 2008
JOURNAL FREE ACCESSThe phase analysis was carried out for the system of(2-y)FeSi2+yFeAl2 in the range 0≤y≤0.20 by an X-ray technique. The solid solution FeSi2-yAly was identified in the composition range 0≤y≤0.12. Electrical resistivity ρ and Hall coefficient were measured as a function of temperature over the range from 80 to 1100K. The measurement of thermal conductivity was also carried out by a comparative method at 300K. The pure FeSi2 was p-type semiconductor with the hole concentration np of 1.70×1023/m3 at 300K. ρ was independent of y in the range 0≤y≤0.02 and rapidly decreased above y=0.03. Below y=0.03, the hole mobility μH indicated the relationship of exp[-Eh/(kT)] in the temperature range from 200 to 300K, where Eh and k are the hopping energy and Boltzman constant, respectively. Eh was determined to be 0.110eV from the hopping mobility μpol=μ0 exp[-Eh/(kT)]. In the range 0.04≤y≤0.12, it was shown that the changes in μpol have relationships of T-3/2 and T3/2 above and below 250K, respectively, and the band conduction was predominant. The maximum figure of merit was found to be 9.6×10-5K-1 for y=0.08.View full abstractDownload PDF (995K) -
Kazuo Okano, Yoshimitsu Takagi1996 Volume 116 Issue 3 Pages 218-223
Published: February 20, 1996
Released on J-STAGE: July 15, 2008
JOURNAL FREE ACCESSSiC ceramics are promising candidate materials for high temperature operating devices application such as thermoelectric energy converters, because of the high chemical stability. However, the electrical conductivity of the SiC ceramics is too low to apply to the thermoelectric energy converter at low temperature. Therefore, we propose a SiC-Si functionally gradient material (FGM) in order to improve the electrical conductivity of the SiC ceramics at low temperature.
SiC rod was fired in the temperature gradient furnace. One edge of SiC rod was kept at 2473K and another edge was kept at 1973K for 0.5h. After firing, the porous SiC edge which was fired at 1973K was dipped into molten Si in order to impregnate porous SiC with Si. The microstructure of the FGM is classified into three region, that is densified SiC ceramics, porous SiC ceramics and SiC-Si composite materials. The electrical conductivity, thermal conductivity and Seebeck coefficient for each part of SiC-Si FGM were measured and the figure of merit was calculated. The figure of merit of cooling edge of the SiC-Si FGM, at room temperature, was 108 times higher than that of SiC ceramics.View full abstractDownload PDF (2497K) -
Akira Tsuyoshi, Kenji Matsuura1996 Volume 116 Issue 3 Pages 224-230
Published: February 20, 1996
Released on J-STAGE: July 15, 2008
JOURNAL FREE ACCESSAs a conceptual design of a large scale thermoelectric generator, OTEC generating system using waste heat of a fuel cell plant and generating system utilizing heat of combustible solid waste were investigated in Japan. But a thermoelectric generating module which is the most costly item in a thermoelectric generator are produced for a use of a special application, like a generator in a space probe or a generator used in an isolated district. Thus the price of a thermoelectric generating system is guessed to be very high. In the case using waste heat there is a possibility that a thermoelectric generation is applied for commercial electricity generation. This paper analyzes dependency of dimensions of a thermoelectric generator on performance and economics of electricity generation by use of waste heat.View full abstractDownload PDF (1216K) -
Akio Suzuki, Shigeo Kobayashi1996 Volume 116 Issue 3 Pages 231-235
Published: February 20, 1996
Released on J-STAGE: July 15, 2008
JOURNAL FREE ACCESSThe second-law analysis or the exergy analysis on a thermoelectric generator (TEG) was made to explore actual power producing ability of the device. The TEG is a device that converts heat directly to electricity. This property is fascinating in recent worldwide circumstance of energy saving and is widely applicable to many situations existing temperature difference in our surroundings. However, its energy efficiency or electricity conversion efficiency is usually less than one percent presently: energy efficiency has been thought to be too low to use power production even though the cost problem would not be considered. In this study, exergy balance analysis disclosed that the TEG has almost equivalent exergy efficiency to the solar photovoltaic cell and the value increases with increase of lower working temperature despite the energy efficiency keeps almost constant. From this analysis, it could be concluded that the TEG is useful for heat sources that have small temperature difference with a large amount of capacities such as ocean thermal energy, waste heat in a city, etc., and is also available to the topping power generators for high temperature heat sources.View full abstractDownload PDF (1235K) -
Takenobu Kajikawa, Izumi Katsube, Sunao Sugihara1996 Volume 116 Issue 3 Pages 236-241
Published: February 20, 1996
Released on J-STAGE: July 15, 2008
JOURNAL FREE ACCESSThermoelectric properties of n-type sintered magnesium silicides are investigated aiming the development of a thermoelectric power generation system using waste heat such as combustion heat of municlpal solid waste. The samples are sintered with a shrinking rate control sintering method to keep each grain size small. Temperature dependencies of thermoelectric properties such as Seebeck coefficient, electrical resistivity and power factor are measured for the temperature range from 300K to 770K. The samples are also analyzed with SEM and powder X-ray diffraction method (XRD). It is clarified that the sintered magnesium silicides can be promisingly used as thermoelectric element for the middle temperature range around 700K. On the basis of the thermal conductivity measurement by laser flash method at room temperature and power factor measurement the non-dimensional figure of merit ZT can be estimated about 0.4 at 600K.View full abstractDownload PDF (1559K) -
Y. Noda, M. Orihashi, I. A. Nishida1996 Volume 116 Issue 3 Pages 242-247
Published: February 20, 1996
Released on J-STAGE: July 15, 2008
JOURNAL FREE ACCESSTwo types of n-type single crystals of PbTe were prepared. One is the undoped crystals by sublimation method under controlled Pb pressure where the electron concentration was covered from 1018 to 1019cm-3. The maximum figure of merit at 300K was 2.2×10-3K-1. The other is the iodine-doped crystals by Bridgman method using PbI2 as the source material of iodine. The electrical conductivity and Hall mobility were measured from 77 to 300K. The electron concentration was successfully controlled in the range from 5.0×1017 to 5.0×1019cm-3 by doping 700 to 6000 molppm PbI2. The temperature dependence of electron mobility indicated that the scattering mechanism of the electron changed from phonon scattering to impurity scattering with an increased amount of PbI2. From the results of electrical conductivity and thermoelectric powei measurements, the figure of merit estimated by using the literature data of thermal conductivity was 1.3×10-3K-1 at 2000 molppm PhI2.View full abstractDownload PDF (888K) -
Lidong Chen, Takashi Goto, Jianhui Li, Masayuki Niino, Toshio Hirai1996 Volume 116 Issue 3 Pages 248-252
Published: February 20, 1996
Released on J-STAGE: July 15, 2008
JOURNAL FREE ACCESSPhase relations of silicon-boron system in boron-rich region were studied by solid state reaction, and the boron-rich silicon boride specimens were prepared by arc-melting and spark plasma sintering. Rhombohedral SiBn(n=15-49) single phase and mixtures of SiB6 and SiBn were observed in the region B=93.7-98at% and B=86-93.7at%, respectively. The arc-melted specimens consisted of SiBn and free Si, while no free silicon was observed in the plasma sintered specimen. The thermoelectric properties of the plasma sintered and arc-melted specimens were studied. The effects of the phase composition and microstructure on the thermoelectric properties were discussed. The thermoelectric figure of merit values (ZT) of the silicon borides increased with increasing temperature. The plasma sintered silicon boride containing 90at%B showed the largest ZT value, which reached 0.2 at 1100K.View full abstractDownload PDF (2302K) -
Hiromasa T. Kaibe, Tsugunori Okumura, Isao A. Nishida1996 Volume 116 Issue 3 Pages 253-257
Published: February 20, 1996
Released on J-STAGE: July 15, 2008
JOURNAL FREE ACCESSBi2Te2.85Se0.15 single crystals involving a p-n inversion layer were successfully grown by using Czachralski technique. The n-type single crystal with a low electron concentration of 1.6×1017cm-3, which is two orders in magnitude lower than that of the starting material, was cut down across the p-n inversion layer. The Hall mobility of this specimen attained to an extremely high value of 35000cm2/V sec at 10K, even then the electron concentration was in degenerate state.
The π-shaped thermocouple was constructed with two legs cut down from the as-grown boules and with the cupper electrodes. The figure of merit of the thermocouple was 2.3×10-3 K-1 at 245K. It is superior to that of materials prepared by Bridgman method. Accordingly, it was found that the Czochralski technique is a promising method for fabricating the p-n thermocouple with a graded carrier concentration.View full abstractDownload PDF (2709K) -
Tsuyoshi Koyanagi, Koji Adachi, Kengo Kishimoto, Kakuei Matsubara1996 Volume 116 Issue 3 Pages 258-267
Published: February 20, 1996
Released on J-STAGE: July 15, 2008
JOURNAL FREE ACCESSThe ZnSb ceramics, of which preparation has been difficult due to the peritectic reaction, have been successfully prepared by the pulverized and intermixed elements sintering (PIES) method. The ZnSb ceramics with a single phase and a high thermoelectric figure of merit were easily obtained by sintering at lower temperatures than the peritectic temperature of ZnSb. In order to improve the thermoelectric properties of ZnSb ceramics, Ag and Sn were doped in the ZnSb ceramics. The electrical conductivity of Ag- and Sn-doped ZnSb ceramics largely increased with an increase in the amount of Ag and Sn, resulting in improvement of the thermoelectric figure of merit. The hot-pressing process was also employed in the sintering process. The density of hot-pressed ZnSb ceramics exceeded 90% of the theoretical ZnSb density, and their thermoelectric figure of merit was expected to be -0.8×10-3K-1.View full abstractDownload PDF (2397K) -
Kakuei Matsubara, Daiji Iyanaga, Takahiro Tsubouchi, Kengo Kishimoto, ...1996 Volume 116 Issue 3 Pages 268-272
Published: February 20, 1996
Released on J-STAGE: July 15, 2008
JOURNAL FREE ACCESSAn average figure of merit value of Z-10-3K-1 was achieved for CoSb3 substituted by Pd (3%) over the wide temperature range 300-800K. Samples of (PdxCo1-x) Sb3 compounds, 0≤x≤0.05, were prepared by static iso-thermal pressing (SIP) the milled powders and by subsequent annealing in inert gas. Measurements of the electrical and thermal transport properties were made on the samples at temperatures ranging from 300K to 800K. It was found that the conduction type was n-type and the electron mobility as high as-100cm2/(Vs) was obtained for a (Pd0.03Co0.97) Sb3 sample. The high value of the mobility can be attributed to the valence band that is only formed by p-p bonds between adjacent Sb-atoms. The doping of Pd into CoSb3 lattice causes the type conversion from p-type to n-type, and results in a high Seebeck coefficient of S--0.3mV/K, electrical conductivity σ-3×102 S/cm, and low thermal conductivity k-2.5W/(mK) at room temperature.View full abstractDownload PDF (1407K) -
Yong-Hoon Lee, Ryuichi Isobe, Tsuyoshi Koyanagi, Kakuei Matsubara1996 Volume 116 Issue 3 Pages 273-278
Published: February 20, 1996
Released on J-STAGE: July 15, 2008
JOURNAL FREE ACCESSUltra fine powder of Bi91Sb9 was sintered under unidirectional high pressure. The powder was prepared by the hydrogen plasma-metal reaction method. The sintered alloys have a layered structure of grains oriented perpendicular to the press axis, resulting in the anisotropic thermoelectric properties. The Seebeck coefficient of the sintered alloys increases by applying a magnetic field. The magnetic field variation of the Seebeck coefficient depends on the direction of a magnetic field. This dependence could be explained by the shape effect of grains in the sintered alloys on the thermoelectric transverse-transverse effect. The power factor of the sintered alloys is improved by applying a magnetic field, and its value reachs to 2.8× 10-5W/cmK2 at H=5kOe and T=172K.View full abstractDownload PDF (2116K) -
Katsuyoshi Shinyama, Takenori Suzuki, Shigetaka Fujita1996 Volume 116 Issue 3 Pages 279-280
Published: February 20, 1996
Released on J-STAGE: July 15, 2008
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Masafumi Suzuki, Fumiaki Kagaya, Toshiyuki Taniguchi, Noboru Yoshimura ...1996 Volume 116 Issue 3 Pages 281-282
Published: February 20, 1996
Released on J-STAGE: July 15, 2008
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Yoshio Saitoh, Yasutaka Inanaga, Yukio Sato1996 Volume 116 Issue 3 Pages 283-284
Published: February 20, 1996
Released on J-STAGE: July 15, 2008
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