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Thermoelectric material and method for producing same

a technology of thermoelectric materials and thermoelectric elements, which is applied in the direction of thermoelectric device junction materials, thermoelectric device manufacture/treatment, electrical apparatus, etc., can solve the problems of reducing the energy conversion efficiency of thermoelectric elements, increasing impurities, and decreasing relative density, so as to reduce the thermal conductivity of thermoelectric materials. , the effect of reducing the electrical resistivity

Inactive Publication Date: 2006-03-16
SUMITOMO ELECTRIC IND LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0013] An object of the present invention is to provide a thermoelectric material of high performance by solving the above-described problems of the conventional art and lowering the thermal conductivity of the thermoelectric material with a minimum increase in electrical resistivity.

Problems solved by technology

Actually, however, the energy conversion efficiency of a thermoelectric element is lower than that of the conventional system using a compressor.
Although no reason for the performance deterioration is mentioned, it is considered that the smaller particle size causes an increase of impurities and a decrease of the relative density.
This thermoelectric conversion material, however, has a problem of a low relative density resulting in a deterioration in performance due to the deposition or dispersion of the crystals that are components of the thermoelectric conversion material.
Actually, however, the improvement in performance is limited within a certain range, since there are limits to the technique of producing ultrafine powders and the sintering technique and thus it has been impossible to produce a sintered body having a fine crystal structure.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

example 1

[0039] As a thermoelectric material, FeSi2 whose material is cheap and easy to be obtained was selected to verify effects of the present invention. A commercially available FeSi2 powder (particle size: 10 to 20 μm) was enclosed in an iron pot together with iron balls, and the atmosphere therein was an inactive gas atmosphere generated by Ar substitution. Then, by planetary ball milling, the powder was ground for 10 hours. After the grinding, it was confirmed through an SEM observation that the particle size of secondary particles of the FeSi2 powder was 0.5 to 2 μm. The size of crystallite was determined based on the integral breadth obtained from XRD measurement of the FeSi2 powder (Hall method), and it was found that the crystal size was 5 to 10 nm (average crystal particle size: 8 nm). In an Ar globe box, the FeSi2 powder was enclosed in a capsule made of Ni to fill the capsule and sintered under a pressure of 3 GPa at 700° C. for 30 minutes. From XRD measurement after the sinter...

example 2

[0042] A sintered body was produced through the same process as that of Example 1 except that the time for grinding by ball milling was five hours, and the average particle size of crystals constituting the sintered body and thermal conductivity were measured. The results are shown in Table 1 below. In Table 1, No. 4 shows the results of Example 2 and No. 5 shows the results of Example 1. The average crystal particle size after ball milling was 35 nm. From the results shown in Table 1, it is found that the thermal conductivity considerably lowers when the particle size of crystals of the sintered body structure is 0.05 μm or less.

example 3

[0044] From the sintered body of Example 1 (No. 5 in Table 1), a sample of 1 mm×1 mm×15 mm in size was cut, and the electrical resistivity was measured by the four-terminal method. Further, through an EDS analysis of a grain boundary portion of the sintered body, constituent elements were identified. In addition, under the same conditions as those of No. 5, two types of sintered bodies were produced by ball milling in air with no Ar substitution (No. 6) and by enclosing in atmosphere the powder in the Ni capsule before sintering (No. 7). For these sintered bodies, the electrical resistivity was measured and the EDS analysis was conducted in the manner as described above. The results are shown in Table 2.

[0045] From the results, it was found that impurities (oxide in this case) of grain boundaries have a great influence on the electrical resistivity, and the reduction of the impurities could make the electrical resistivity lower even the crystal structure was a fine crystal structur...

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Abstract

A thermoelectric material has an average crystal particle size of at most 50 nm and has a relative density of at least 85%. A method of manufacturing a thermoelectric material includes the steps of preparing a fine powder and sintering or compacting the fine powder under a pressure of at least 1.0 GPa and at most 10 GPa.

Description

TECHNICAL FIELD [0001] The present invention relates to a thermoelectric material that is a constituent of a thermoelectric element used for thermoelectric power generation utilizing the Seebeck effect and for direct cooling / heating utilizing the Peltier effect. The thermoelectric material used for the thermoelectric element includes such known materials as Bi2Te3-based material, CoSb3-based intermetallic compound with the Skutterudite structure, ZrNiSn for example with the half-Heusler structure (MgAgAs), FeSi2, and MnSi1.73. BACKGROUND ART [0002] The thermoelectric technology including the thermoelectric power generation utilizing the Seebeck effect and the direct cooling / heating utilizing the Peltier effect has the following characteristics as compared with the conventional compressor-based technology: [0003] 1. system structure is simple and can be reduced in size; [0004] 2. such refrigerants as chlorofluorocarbons are not used; and [0005] 3. no moving part, which provides excel...

Claims

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Application Information

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Patent Type & Authority Applications(United States)
IPC IPC(8): C22C1/04B22F3/14H01L35/14H01L35/34H02N11/00
CPCH01L35/34H01L35/14H10N10/851H10N10/01B22F3/14H02N11/00
Inventor HARADA, TAKASHITODA, NAOHIROSUMIYA, HITOSHI
Owner SUMITOMO ELECTRIC IND LTD
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