Thermoelectric Properties of Iron-Silicide with various baoudaries

不同鲍德瑞硅化铁的热电性能

基本信息

批准号：
14350372
负责人：
HASAKA Masayuki
金额：
$ 4.86万
依托单位：
Nagasaki University
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2002
资助国家：
日本
起止时间：
2002 至 2004
项目状态：
已结题

来源：
https://kaken.nii.ac.jp/en/grant/KAKENHI-PROJECT-14350372/
关键词：
Thermoelectric Material Iron Disilicide Figure of Merit Power Factor Electron Microscopy β-FeSi2 βFeSi_2

项目摘要

There are problems such as the global warming and fossil fuel depletion crisis. Alternative energy to current energy is desired to solve these problems. One of prospective energies is generated from thermoelectric conversion. The conversion efficiency and generating power become higher with higher figure of merit ZT and higher power factor P. The ZT and P are given byZT=σα^2/κ=σα^2/(κ_<el>+κ_<ph>),P=σα^2,where T is temperature, σ electrical conductivity, α Seebeck coefficient, κ_<el> and κ_<ph> being thermal conductivity due to electron and phonon transportations.The β-FeSi_2 attracts attention for the thermoelectric conversion, because it is abundant and free of toxicity, being high heat-resistant and oxidation-resistant. The polarity of β-FeSi_2 is convertible between p- and n-type with selecting the dopant of third element. The figure of merit and power factor of β-FeSi_2 are enhanced by mixing substances such as Ag, or SiC ceramics etc. It is interesting how the thermoelectric prop … More erties depend on microstructures, or fabrication processes of β-FeSi_2 which is mixed with such elements or compounds.The objective of the present research is to clarify the relation between the thermoelectric properties and microstructures or fabrication processes in the Co doped β-FeSi_2 which is mixed with Ag,Cu or Sb ete. In order to enhance the thermoelectric performance, crystal grain boundaries and phase interfaces were controlled on the basis of phase transformation, mechanical alloying, spin-casting and diffusion. The microstructures were investigated by using a transmission electron microscope with an energy dispersion X-ray microanalysis equipment. The Seebeck coefficient, and electrical conductivity were measured and related to the microstructures. The drawn conclusions are given as follows.The Ag,Cu,or Sb-rich phase is observed at the grain boundaries and in the matrix of the β phase.The Seebeck coefficient decreases nonlinearly with increasing the element content. The Seebeck coefficient is large in the ribbon mixed with Ag. The Seebeck coefficient is independent of timing of mixing with Ag. The electrical conductivity decreases nonlinearly with increasing Ag content. The electrical conductivity is large in the discs which are formed by pressing powder. The power factor reaches to maximum near 2-3 at% Ag for the discs.Carrier mobility, effective electron mass, or scattering factor of the discs differs from that of ingot, or ribbon, because of different microstructures.The powder becomes fine and round with ball milling. Sintering reduces the amount of the α phase and increases the amount of ε phase, resulting in decreasing of the β phase and increasing in the ε phase after annealing. The electrical conductivity and the power factor are enhanced by ball-milling, sintering and annaling. Less

存在一些问题，例如全球变暖和化石燃料部署危机。需要为电流能量提供替代能量来解决这些问题。前瞻性能量是由热电转换产生的。随着较高的ZT和更高功率因子的较高数字，ZT和P的转化效率和产生功率变得更高β-FESI_2景点引起了热电转换的关注，因为它丰富且无毒性，具有高耐热和抗氧化。 β-FESI_2的极性通过选择第三个元素的掺杂剂在p-和n型之间可转换。 β-FESI_2的优异和功率因数的图可以通过混合物质（例如AG或SIC陶瓷等）来增强。有趣的是，热电支柱如何……更多的兴趣依赖于微观结构或β-FESI_2的制造过程，或与此类元素或化合物之间的关系混合的β-FESI_2的制造过程。与Ag，Cu或Sb Ete混合的掺杂的β-FESI_2。为了增强热电性能，基于相变，机械合金，自旋铸造和扩散控制晶体晶界和相位界面。通过使用能量分散X射线微分析设备的透射电子显微镜研究了微观结构。测量了Seebeck芯和电导率，并与微结构有关。得出的结论如下。在晶界和β相的基质中观察到Ag，Cu或富含SB的相。Seebeck核心随着元素含量的增加而非线性降低。 Seebeck核心在带有Ag的色带中很大。 Seebeck核心与与Ag混合的时间无关。电导率随着AG含量的增加而非线性降低。通过按压粉末形成的圆盘中的电导率很大。圆盘的功率因数可达到最大接近2-3的AT％ag。由于不同的微观结构，载体迁移率，有效的电子质量或盘的散射因子不同于Ingot或Ribbon。烧结减少了α相的量并增加ε相的量，从而减少了β相并在退火后增加ε相。通过磨球，烧结和安排来增强电导率和功率因数。较少的