Preparation and Properties of Thermoelectric Materials by PM Process.

本文研究了β-FeSi_2和γ-LaS_x的制备工艺和热电性能。主要研究结果如下：1.β-FeSi_2.1.1.的制备及性能研究机械研磨（MG）和热压的效果显著地改善了致密化和从α + β相到β相的转变。MG使ε相在β-FeSi_2中弥散分布，降低了材料的介电常数，提高了材料的热电性能. Co、Ni、B的加入对FeSi_2的烧结有明显的促进作用，而B的加入对烧结有明显的阻碍作用。Co的加入提高了热电势，而Ni和B的加入降低了热电势. LaS_x（4/3*X*3/2）中存在α、β、γ三相，γ-LaS_x相有望成为良好的热电材料。但制备γ-LaS_x相的条件尚未明确。本文研究了γ-LaS_x的制备工艺及其热电性能。在1273 K下，金属La与Si在石英壳中发生固相反应，在低S组分中得到γ相。

In this study, the preparation process and the thermoelectric properties of beta-FeSi_2 and gamma-LaS_x were investigated. The results are summarized as follows:1. Preparation and properties of beta-FeSi_2.1.1. Effect of Mechanical Grinding(MG)MG and Hot-pressing significantly improved the densification and transition from alpha+epsilon phase to beta-phase. Finely dispersed epsilon-phase in beta-FeSi_2 by MG increased the thermoelectric properties by decreasing the resistivity.1.2. Effect of Co, Ni, B Addition.Co, Ni addition markedly accelerated the sintering of FeSi_2, while B addition hindered the sintering. Co addition increased the thermoelectric power, while Ni and B addition decreased the thermoelectric power.2. Preparation and properties of gamma-LaS_x.Thre are three phases(alpha、beta、gamma) in LaS_x(4/3*X*3/2) and gamma-LaS_x phase is expected to be good thermoelectric material. However, the conditions to prepare gamma-LaS_x phase have not been clarified. In this study, the preparation process of gamma-LaS_x and their thermoelectric properties were investigated. Through solid phase reaction between metallic La and S ina quartz capsule at 1273 K, it became clear that gamma-phase was obtained in the low S compositions.