烧结对N型赝三元碳纤维掺杂复合热电材料性能的影响

发布时间：2018-03-19 00:12

  本文选题：n型Bi2Te3基热电材料　切入点：烧结　出处：《哈尔滨师范大学》2015年硕士论文　论文类型：学位论文

【摘要】：热电材料是一种可以实现电能和热能相互转化的功能材料,有关塞贝克效应与帕尔贴效应的研究为热电材料的广泛应用提供了坚实的理论基础。热电器件普遍具有体积小,质量轻,无污染,可回收和易控制等优点。然而,由热电材料制造的装置(如冰箱等)工作效率却低于传统工作方式(如压缩机制冷)。通常使用热电优值Z值来评价材料的热电效率,Z值越高,说明材料热电效率越高。因此,如何提升Z值,成为热电材料研究领域的一个核心问题。Bi2Te3基热电材料是当前热电材料研究领域中最为热门的材料之一,由于其热电性能好,因而在半导体元器件制作中得到了广泛应用。本文以n型Bi2Te3基赝三元热电材料为研究对象,采用单质熔炼化合法制得n型Bi2Te3固溶体合金。并通过碳纤维掺杂,得到n型赝三元碳纤维掺杂Bi2Te3复合材料粉体。通过热压烧结法获得n型赝三元碳纤维掺杂Bi2Te3复合块体材料。在惰性气体环境下烧结,针对不同烧结温度的n型碳纤维掺杂Bi2Te3复合材料块体进行热电性能及微观结构分析。经过微观结构分析结果表明,通过对样品进行SEM和XRD处理,发现碳纤维在n型Bi2Te3基赝三元热电材料中分布均匀,并且起到了较为明显的连接作用,高温烧结使n型Bi2Te3基赝三元热电材料的结构更加紧凑,使原来分散的晶粒结构能够融合在一起,成为较大的晶粒;整体结构也由原来较为松散的无规则形状,经烧结成为了明显的梯田状结构,增强了材料的热电性能,对于材料Z值的提升是有积极意义的;载流子疏运分析结果表明,在一定温度范围内,载流子的迁移率和浓度都随着烧结温度的升高而升高;热电性能分析结果表明,热压温度恒定的情况下,随着烧结温度的升高,n型碳纤维掺杂Bi2Te3复合材料的热导率κ呈现出先减小后增大的趋势,并且在烧结温度达到约300℃的时候达到最大值;电导率σ呈现出先减小后升高的趋势,并且在烧结温度达到250℃的时候达到最小值;n型碳纤维掺杂Bi2Te3复合材料的塞贝克系数α呈现先增大后减小的趋势,在烧结温度达到300℃的时候达到最大值。最后经过计算得到热电优值表明,在低温区,n型Bi2Te3基赝三元碳纤维掺杂复合热电材料随着烧结温度的升高,热电优值呈现出递增趋势,并且在300℃达到最大值,这也证明了300℃为低温区本实验原料的最佳烧结温度。综上所述,本文通过微观结构分析、载流子输运结果分析和热电性能分析等手段,采用了SEM、XRD、高温烧结等手段,预测了烧结温度与n型Bi2Te3基赝三元碳纤维掺杂复合热电材料性能的关系。通过研究获得了赝三元材料的最佳烧结温度和热电性能随着烧结温度变化的基本规律,揭示了烧结温度对材料热电性能影响的机理。研究结果对于进一步研究赝三元热电材料性能具有重要意义。
[Abstract]:Thermoelectric material is a kind of functional material which can realize the mutual conversion of electric energy and heat energy. The research on Seebeck effect and Partil effect provides a solid theoretical basis for the wide application of thermoelectric materials. Thermoelectric devices are generally small in size. Light weight, pollution-free, recyclable and easy to control. However, The working efficiency of devices made of thermoelectric materials (such as refrigerators, etc.) is lower than that of conventional working methods (such as compressor refrigeration). The higher the thermoelectric efficiency (Z value) is usually used to evaluate the thermoelectric efficiency (Z value) of materials, the higher the thermoelectric efficiency of materials is. How to raise Z value has become a core problem in the field of thermoelectric material research. Bi2Te3-based thermoelectric material is one of the most popular materials in the field of thermoelectric material research at present, because of its good thermoelectric properties, In this paper, n-type Bi2Te3 based pseudo-ternary thermoelectric material was used as the object of study. N type Bi2Te3 solid solution alloy was prepared by simple melting and combining method, and doped with carbon fiber. N type pseudo ternary carbon fiber doped Bi2Te3 composite powder was obtained. N type pseudo ternary carbon fiber doped Bi2Te3 bulk material was obtained by hot pressing sintering. The thermoelectric properties and microstructure of n-type carbon fiber doped Bi2Te3 composites with different sintering temperatures were analyzed. The results of microstructure analysis showed that the samples were treated with SEM and XRD. It is found that carbon fiber distributes uniformly in n-type Bi2Te3 based pseudo-ternary thermoelectric materials and plays a more obvious connection role. The structure of n-type Bi2Te3 based pseudo-ternary thermoelectric materials is more compact by high temperature sintering. The original dispersed grain structure can be fused together to become larger grain. The whole structure is also changed from the original loose irregular shape to a clear terraced structure after sintering, which enhances the thermoelectric properties of the material. The results of carrier transport analysis show that the mobility and concentration of carriers increase with the increase of sintering temperature, and the results of thermoelectric properties analysis show that the carrier transport rate and concentration increase with the increase of sintering temperature. When the hot pressing temperature is constant, the thermal conductivity 魏 of n-type carbon fiber doped Bi2Te3 composites decreases first and then increases with the increase of sintering temperature, and reaches the maximum value when sintering temperature reaches about 300 鈩，

本文编号：1631956