1、 毕 业 论 文论 文 题 目 两类过渡金属化合物热电材料的生长及 输运性质研究 学 科 、 专 业 名 称 凝 聚 态 物 理 研 究 方 向 热电材料的生长与输运性质研究 摘要I摘要自 19 世纪工业革命以来，在全世界范围内，人类对能源的需求快速增长。为了满足工业生产和日常生活的能源需求，不可再生能源（如煤炭、石油、天然气等化石燃料）被大量开采及使用，这些能源的使用造成了严重的环境污染问题，比如空气污染、温室效应、酸雨等。而我国的能源形势更不容乐观，其最主要的原因在于能源需求量巨大和能源利用效率低下。具体而言，从 2007 年起我国是全世界第二大能源生产国和消费国，二氧化碳的排放量位居全球
2、第二位。而且我国的能源结构十分不合理，能源利用效率低下，造成了严重的能源浪费现象，从而对环境产生了严重的污染与破坏。在我国的工业用能中，大约 60%的能源转化为工业废热资源，且工业废热利用率低下（仅为 30%） 。所以为了减少能源消耗和降低环境污染，我国亟需提高工业废热的利用率。在这种背景下，热电材料走进了人们的视野，引起了人们的广泛关注，因为热电效应使热能和电能可以直接转换，可以对工业废热加以利用。热电材料是一种环境友好型的热能- 电能转换材料，具有体积小、可靠性高、无污染、温度适用范围广等优点。由于目前热电设备的效率不够高，所以需要对热电材料的电输运和热输运性质进行系统研究，以提高热电材料
3、的热电性能。推动热电材料在工业生产和日常生活中的实际应用，达到提高废热利用率、节约能源和保护环境的终极目的。本文通过不同的生长方法制备了一系列热电材料单晶和多晶陶瓷样品，利用物理性质综合测量系统研究了二类热电材料单晶和多晶陶瓷样品的电输运和热输运性质。主要结论如下：1. 通过化学气相输运法和高温固相合成法，分别生长制备获得 Te 缺的 ZrTe5-单晶及富 Te 的 ZrTe5+多晶陶瓷，通过综合物性测量系统分别对 Te 缺的 ZrTe5-单晶及富 Te 的 ZrTe5+陶瓷的电输运性质和热电性质进行了研究与比较。发现通过对Te 元素化学计量的控制，改变了 ZrTe5 化合物的电输运性质，从而
4、达到调控 ZrTe5化合物热电参数和提高 ZrTe5 化合物热电性能的目的。具体而言富 Te 的 ZrTe5+陶瓷在室温 300K 时电阻率、Seebeck 系数、热导率和热电优值 ZT 分别为 6.0 mcm、123 VK-1 、1.86 W/(mK)和 0.037。ZT 值在过去文献中报道的ZrTe5/HfTe5 中最高。这一工作为进一步提升热电材料性能提供了思路。摘要II2. 通过化学气相输运法和高温固相合成法，分别生长制备获得 BiCuSO 单晶、BiCuSeO 单晶和 BiCuTeO 多晶陶瓷，通过综合物性测量系统分别对这些样品的电输运性质进行了研究与比较；对 BiCuXO (X=S
5、,Se,Te)材料的电子散射机制有了较深入的研究，发现元素替换(从 S 到 Te)显著减小了 BiCuXO 材料体系电阻率。并且从BiCuSeO 到 BiCuTeO，电声子耦合作用对载流子的散射逐渐减小。总结ZrTe 5和BiCuXO (X=S,Se,Te)材料这两个体系的实验结果与理论分析我们发现：对元素化学计量的控制和元素的替换可以实现对材料电输运性质的有效调控。因此，我们可以基于以上方法，调控热电材料的电输运性质从而提升热电材料的热电性能。电子散射机制的研究有可能提供改善热电材料系统电导率的新思路。关键词：ZrTe 5；BiCuXO；晶体生长；化学气相输运法；电输运；热电性质Abstra
6、ctIIIAbstractSince the Industrial Revolution of the 19th century, the demand for energy has grown rapidly all over the world. In order to meet the energy demand of industrial production and daily life, non-renewable energy(such as coal, oil, natural gas and other fossil fuels) has been extensively e
7、xploited and used, resulting in serious environmental pollution problems, such as air pollution, greenhouse effect, acid rain and so on. Compared with other countries, energy situation of China is not optimistic, because of the large demand for energy and the the inefficient use of energy. China has
8、 been the second largest energy producer and consumer in the world since 2007. Carbon dioxide emissions are the second largest in the world. Due to the non-optimized energy usage structure and the energy use inefficiency, China has caused serious energy waste, which has caused serious pollution and
9、environmental problems. In China, about 60% of industrial energy is converted into industrial waste heat, and the utilization rate of industrial waste heat is as low as 30%. Therefore, in order to reduce energy waste and environmental pollution, it is urgent for China to increase the utilization rat
10、e of industrial waste heat.In this background, thermoelectric materials have come into peoples vision and attracted intensive attention, because the thermoelectric effect enables the direct conversion of heat to electrical energy, and can be used to take advantage of industrial waste heat. Thermoele
11、ctric material is an environment-friendly heat-electrical-energy conversion material, which has the advantages of small size, high reliability, pollution-free, wide temperature application range and so on. At present, the efficiency of thermoelectric devices are still not high enough, so it is neces
12、sary to study the electrical and thermal transport properties of thermoelectric materials to improve their thermoelectric performance, promote the practical utilization of thermoelectric materials in industrial production and daily life to achieve the ultimate goal of improving the utilization rate
13、of waste heat, conserving energy and protecting the environment.In this paper, a series of single crystal and polycrystalline ceramics samples of AbstractIVthermoelectric materials have been prepared by different methods. The electrical and thermal transport properties of these materials have been m
14、easured by Physical Property Measurement System. The main conclusions are:1. Te-deficient ZrTe5- single crystal and Te-rich ZrTe5+ polycrystalline ceramics were grown by chemical vapor transport method and high temperature solid-state reaction method respectively. The electrical and thermal properti
15、es of Te-deficient ZrTe5- single crystal and Te-rich ZrTe5+ polycrystalline ceramics were studied and compared by Physical Property Measurement System characterizations. It is found that the electrical transport properties of ZrTe5 compounds are changed by controlling the stoichiometry of Te element
16、s so that the thermoelectric parameters of ZrTe5 compounds can be adjusted and the thermoelectric properties of ZrTe5 compounds can be improved. In details, the electrical resistivity, Seebeck coefficient, thermo-conductivity and ZT value of ZrTe5+ ceramics are 6.0 m cm、123 VK-1 、1.86 W/(mK) and 0.0
17、37 measured at 300 K, respectively. ZT value of our sample is higher than those of ZrTe5/HfTe5 at previous reports. Our work provides an idea for further improving the thermoelectric properties.2. BiCuSO single crystal, BiCuSeO single crystal and BiCuTeO polycrystalline ceramics were prepared by che
18、mical vapor transport method and high temperature solid-state reaction method respectively. The electrical transport properties of BiCuSO single crystal, BiCuSeO single crystal and BiCuTeO polycrystalline ceramics were studied and compared by Physical Property Measurement System characterizations. T
19、he electronic scattering mechanism of BiCuXO (X=S, Se, Te) materials was systematically studied. We found that element replacement from S to Te dramatically decreases the electrical resistivity of BiCuXO compounds. Moreover, the carrier scattering by electron-phonon interaction is decreased when the
20、 compound changes from BiCuSO to BiCuTeO.Summarizing the experimental results and theoretical analysis of ZrTe5 and BiCuXO (X=S, Se, Te) compounds, we find that the control of element stoichiometry and element substitution can effectively control the electrical transport properties of materials. The
21、refore, based on the methods above, we can modify the electrical conductivity of thermoelectric AbstractVmaterials, improve their thermoelectric properties. The study of electrical scattering mechanism may provide new ideal on how to improve electrical property of thermoelectric materials.Keywords:
22、ZrTe5; BiCuXO; Crystal growth; Chemical vapor transport; Electric transport; Thermoelectric propertiesAbstractVI目录VII目录摘要 .IAbstract.III目录 .VII第一章 综述 .11.1 引言 .11.2 热电效应的基本原理及其应用 .11.2.1 热电效应的基本原理 .11.2.2 热电材料和热电器件的主要应用 .51.2.3 热电效应的基本参数与相互关系 .91.3 几种热电材料的研究进展 .101.3.1 ZrTe5 体系热电材料的研究进展 .121.3.2 BiC
23、uXO 体系热电材料的研究进展 .191.4 本文的主要内容和研究意义 .28第二章 晶体生长及测试方法 .312.1 引言 .312.2 晶体生长方法 .312.2.1 多晶样品的制备 .312.2.2 气相输运法单晶生长 .322.3 材料表征方法 .322.3.1 X 射线衍射（XRD） .322.3.2 扫描电子显微镜（SEM） .332.3.3 差热分析法（DTA） .342.3.4 综合物性测量系统（PPMS） .342.4 本章小结 .35第三章 ZrTe5-晶体及 ZrTe5+陶瓷的制备与输运研究 .373.1 引言 .373.2 ZrTe5-晶体的制备与输运研究 .37目录V
24、III3.2.1 XRD 和 EDS 结果与分析 .373.2.2 ZrTe5-晶体的电输运结果与分析 .393.3 ZrTe5+陶瓷的制备与输运研究 .403.3.1 EDS 和 DTA 结果与分析 .403.3.2 ZrTe5+陶瓷的电输运结果与分析 .413.3.3 ZrTe5+陶瓷的热电性能 .433.4 本章小结 .45第四章 BiCuXO(X=S,Se,Te)材料的制备与电输运、电磁输运性质研究 .474.1 引言 .474.2 BiCuSO 晶体制备与输运研究 .474.2.1 EDS 和 XRD 结果与分析 .474.2.2 电输运结果与分析 .484.3 BiCuSeO 晶体制备与输运研究 .504.3.1 EDS 和 XRD 结果与分析 .504.3.2 电输运结果与分析 .514.4 BiCuTeO 多晶陶瓷制备与输运研究 .534.4.1 EDS 和 XRD 结果与分析 .534.4.2 电输运结果与分析 .544.5 BiCuXO (X=S,Se,Te)材料的对比与讨论 .564.6 本章小结 .59第五章 总结与展望 .615.1 总结 .615.2 展望 .62参考文献 .63攻读硕士期间学术成果 .73致谢 .75
