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Preparation of Thermoelectric Material by Reactive Diffusion Method

反应扩散法制备热电材料

基本信息

批准号：
11695053
负责人：
SHIMOZAKI Toshitada
金额：
$ 1.6万
依托单位：
Kyushu Institute of Technology
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B).
财政年份：
1999
资助国家：
日本
起止时间：
1999 至 2000
项目状态：
已结题

项目摘要

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.

作为反应扩散形成的金属间化合物的重要特征，我们可以看出，它们不包含任何不必要的相，它们可以在不受坩埚或空气污染的情况下制备，它们具有干净的相界，它们可以有取向的晶粒。当我们能够将这种方法应用到实际中时，就有可能制备出比目前更好的热电材料。众所周知，FeSi2的热电性能不受铁和硅纯度的影响。然而，到目前为止使用的铁板不到99.99%，它们可能在准备过程中受到了污染。此外，还没有使用高纯铁和硅的研究。本工作的目的是利用超高纯度原料制备热电材料，并研究其热电性能。为此，我们利用高纯Fe、Co、Si和Sb材料，采用反应扩散法，研究了Fe-Si、Co-Si和Co-Sb三元系。结果表明，Fe-Si扩散偶中形成的主要扩散层为Fe3Si。Fe_3Si的生长速度在很大程度上取决于铁的纯度。铁中的氧减缓了Fe_3Si的生长速度。在Co-Si二元系统中，我们阐明了CoSi和CoSi2的生长动力学。FeSi2和CoSi或CoSi2都很难用反应扩散法制备。我们尝试用S-Co/S-Sb扩散偶、S-Co/L-Sb扩散偶和S-Co/V-Sb扩散偶等各种扩散偶在Co-Sb二元系中制备CoSb_3。通过这种技术，我们可以得到包含许多小空洞的CoSb3。空洞的存在有望降低CoSb3的导热系数，因此其热电性能也有望得到改善。