2000 Fiscal Year Final Research Report Summary
Preparation of Thermoelectric Material by Reactive Diffusion Method
| Project/Area Number |
11695053
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| Research Category |
Grant-in-Aid for Scientific Research (B).
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Physical properties of metals
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| Research Institution | Kyushu Institute of Technology |
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Principal Investigator |
SHIMOZAKI Toshitada Kyushu Institute of Technology, Center for Instrumental Analysis, Assistant Professor., 機器分析センター, 助教授 (00093964)
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| Project Period (FY) |
1999 – 2000
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| Keywords | THERMOELECTRIC MATERIAL / CoSb3 / FeSi2 / POROUS MATERIAL / THERMAL CONDUCTIVITY / KIRKENDALL VOIDS |
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| Research Abstract |
As important characters of intermetallic compounds formed by reaction diffusion, we can pick up the followings, i.e., they do not include any needless phases, they can be prepared without contamination from crucible or air, they have clean phase boundary interface and they can have orientated grains. When we can apply this method practically, there are possibilities to prepare more excellent thermoelectric materials than that so far.
It has been well known that the thermoelectric properties of FeSi2 are not affected by the purity of iron and Si. However, iron plates used up to the present were less than 99.99% and they might have been contaminated during the preparing process. Further there is no study in which high purity iron and silicon were used. A purpose of this work is to make thermoelectric material by using ultra high purity starting materials taking the contamination due to melting into account and to study the thermoelectric properties. For the purpose we use reaction diffusion method using high purity Fe, Co, Si and Sb materials.
Fe-Si, Co-Si and Co-Sb binary systems have been studied. It has been clarified by this work that main diffusion layer formed in the Fe-Si diffusion couples is Fe3Si. The growth rate of Fe3Si depends significantly on the purity of iron. Oxygen in iron slows down the growth rate of Fe3Si.
In the Co-Si binary systems we have clarified the growth kinetics of CoSi and CoSi2. Both FeSi2 and CoSi or CoSi2 are difficult to make them by the reactive diffusion method. We have tried to make CoSb3 in Co-Sb binary system by using various kinds of diffusion couples such as S-Co/S-Sb diffusion couples, S-Co/L-Sb diffusion couples and S-Co/V-Sb diffusion couples. By this technique we could make CoSb3 including many small voids. The existence of voids is expected to decrease thermal conductivity of CoSb3 so the thermoelectric properties will also be expected to be improved.
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