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

存在诸如全球变暖和化石燃料枯竭危机等问题，需要通过热电转换产生更高的转换效率和发电量来解决这些问题。和更高的功率因数 P。ZT 和 P 由下式给出：ZT=σα^2/κ=σα^2/(κ_<el>+κ_<ph>),P=σα^2，其中 T 为温度，σ 电导率, α塞贝克系数，κ_<el>和κ_<ph>是由于电子和声子传输而产生的热导率。β-FeSi_2因其含量丰富、无毒、高耐热性和氧化性而在热电转换方面引起了人们的关注通过选择第三种元素的掺杂剂，β-FeSi_2的极性可在p型和n型之间转换，通过混合提高β-FeSi_2的品质因数和功率因数。有趣的是，热电特性如何取决于与这些元素或化合物混合的 β-FeSi_2 的微观结构或制造工艺。本研究的目的是阐明掺Ag、Cu或Sb ete的Co掺杂β-FeSi_2的热电性能与微观结构或制备工艺之间的关系为了提高热电性能，对晶界和相界面进行了控制。使用带有能量色散X射线微分析设备的透射电子显微镜研究了相变、机械合金化、旋转铸造和扩散的基础，并测量了塞贝克系数和电导率。得出的结论如下：在β相晶界和基体中观察到富Ag、Cu或Sb相。随着元素含量的增加，塞贝克系数非线性减小。这混入Ag的带材的塞贝克系数与混入Ag的时间无关。通过压制粉末形成的圆片的电导率随Ag含量的增加呈非线性下降。功率因数达到最大值。圆盘的载流子迁移率、有效电子质量或散射系数为-3 at% Ag，由于微观结构不同，圆盘的载流子迁移率、有效电子质量或散射系数与锭或带不同。通过球磨，粉末变得细小和圆润，降低了粉末的粒径。球磨、烧结和退火后，α相含量增加，ε相含量增加，导致β相减少，ε相增加。