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结构功能一体化热电材料英文回答：Structural-functional integrated thermoelectricmaterials are a type of material that can convert wasteheat into electricity. These materials have gainedsignificant attention in recent years due to theirpotential applications in various fields such as energy harvesting, waste heat recovery, and solid-state cooling. The integration of structural and functional properties in these materials allows for enhanced thermoelectric performance.One example of a structural-functional integrated thermoelectric material is a composite material consistingof a semiconductor matrix embedded with nanostructured inclusions. The semiconductor matrix provides theelectrical conductivity necessary for the flow of electrons, while the nanostructured inclusions scatter phonons, which are responsible for heat transfer. This scattering effectreduces the thermal conductivity of the material, leadingto an increased thermoelectric efficiency.Another example is the use of layered materials with a high thermoelectric figure of merit (ZT). These materials have a unique crystal structure that allows for efficient charge transport while maintaining low thermal conductivity. The layered structure provides a pathway for electrons to move through the material, while the weak interlayerbonding hinders phonon transport. This combination of properties results in a high ZT value, indicating a high thermoelectric performance.Structural-functional integrated thermoelectricmaterials can also be designed by controlling the composition and microstructure of the material. For instance, by introducing dopants or defects into the material, the electrical conductivity can be enhanced,while the thermal conductivity can be reduced. This control over the material's properties allows for the optimizationof thermoelectric performance.In addition to their thermoelectric properties,structural-functional integrated thermoelectric materials can also possess other desirable characteristics. For example, some materials exhibit mechanical flexibility, making them suitable for applications in wearable devicesor flexible electronics. Others may have good chemical stability, enabling their use in harsh environments. The integration of these additional functionalities further expands the potential applications of these materials.In conclusion, structural-functional integrated thermoelectric materials are a promising class of materials that can efficiently convert waste heat into electricity.By integrating structural and functional properties, these materials exhibit enhanced thermoelectric performance. The design and control of composition, microstructure, and additional functionalities contribute to their potential applications in various fields.中文回答：结构功能一体化热电材料是一种能够将废热转化为电能的材料。
fundamentals of thermoelectricityoxford 2015The fundamentals of thermoelectricity, as discussed in the Oxford 2015 book, are crucial for understanding the conversion of heat into electrical energy. This field combines principles from thermodynamics, solid-state physics, and materials science to explore the behavior and performance of thermoelectric devices. Thermoelectricity has gained significance in recent years due to its potential application in waste heat recovery, portable power generation, and energy-efficient cooling systems. Let's dive into some key concepts covered in this book.Thermoelectric phenomena arise from a temperature gradient across a material or device. The underlying principle is the Seebeck effect, which describes the generation of an electric voltage when there is a temperature difference between two points in a conductor or semiconductor. This voltage is proportional to the gradient in temperature and depends on the material properties.热电现象是在材料或器件中存在温度梯度时产生的。
硒化锡合成反应方程式1. 引言硒化锡（SnSe）是一种重要的半导体材料，具有优异的热电性能和光学性能。
它在太阳能电池、热电材料、光电器件等领域具有广泛的应用前景。
硒化锡的合成方法有多种，其中最常用的是化学气相沉积（CVD）和溶剂热法。
本文将重点介绍硒化锡的溶剂热法合成反应方程式。
2. 实验原理溶剂热法合成硒化锡主要是利用一种含有硒源和金属锡源的溶剂，在高温下进行反应生成硒化锡。
常用的硒源有硒粉、硒酸等，金属锡源可以是金属锡粉、氧化锡等。
在反应过程中，首先将硒源和金属锡源加入适当的溶剂中，并进行搅拌混合，形成均匀的混合物。
然后将混合物转移到高温容器中，在一定温度下进行反应一段时间。
最后，通过冷却和过滤等步骤，得到硒化锡产物。
3. 实验步骤1.准备硒源、金属锡源和溶剂。
硒源可以选择硒粉，金属锡源可以选择金属锡粉，溶剂可以选择有机溶剂如乙二醇。
2.将硒粉和金属锡粉按一定比例加入乙二醇中，并进行搅拌混合，使其均匀分散。
3.将混合物转移到高温容器中，并加热至一定温度（通常为200-300摄氏度）。
4.在一定时间内保持恒定温度下反应，搅拌反应体系以促进反应进行。
5.反应结束后，将反应体系冷却至室温。
6.用滤纸或其他适当的方法过滤产物，将硒化锡分离出来。
7.对得到的硒化锡进行干燥处理，得到最终产物。
4. 反应方程式根据实验原理和步骤，可以写出硒化锡的合成反应方程式：Sn + Se → SnSe其中，Sn表示金属锡，Se表示硒。
5. 实验条件合成硒化锡的实验条件包括温度、时间和溶剂选择等。
通常情况下，温度在200-300摄氏度之间，反应时间可以根据需要进行调整。
乙二醇是常用的溶剂选择，也可以根据实际情况选择其他有机溶剂。
6. 结果与讨论通过溶剂热法合成的硒化锡具有良好的结晶性和纯度，可以用于进一步的物理性质测试和材料应用研究。
此外，通过调节反应条件和原料比例等因素，还可以得到不同形貌和尺寸的硒化锡纳米材料。
7. 结论本文介绍了硒化锡的溶剂热法合成反应方程式及实验步骤。
热电经济指标释义与计算随着能源需求的不断增长，利用传统能源的可行性正在逐渐减少。
因此，人们开始关注一些新的可再生能源技术，如风能、水力、太阳能和地热能等。
在这些可再生能源体系中，热电（Thermoelectric）技术越来越受到关注。
这项技术可以将废热转换为电能，平衡能源需求与环境保护之间的关系。
热电技术的发展也带来了一些独特的热电经济指标。
本文首先会给出热电经济指标的基本定义和计算公式，随后讨论这些指标在热电技术中的应用。
热电经济指标定义1.热电转换效率（Thermoelectric conversion efficiency）热电转换效率是指系统输出电力和热量的比例，通常用变量“η”表示。
计算公式如下：η = (P_out / Q_in) × 100%其中，P_out为系统输出的电功率，Q_in则为系统输入的热能。
由于系统输入和输出单位的不同，计算时需要将它们转换为相同的单位。
2.热电元件制冷功率（Thermoelectric module cooling power）热电元件制冷功率是指热电元件在制冷时所能够产生的制冷量，通常用变量“Q_c”表示。
计算公式如下：Q_c = W × ΔT其中，W为热电元件电功率，ΔT则为热电元件的温度差。
该指标的单位通常为瓦特（W）。
3.热电元件制热功率（Thermoelectric module heating power）热电元件制热功率是指热电元件在制热时所能够产生的热量，通常用变量“Q_h”表示。
计算公式如下：Q_h = W × ΔT其中，W为热电元件电功率，ΔT则为热电元件的温度差。
该指标的单位同样为瓦特（W）。
热电经济指标应用热电转换效率是热电技术中最为重要的经济指标之一。
它衡量了系统在将废热转化为电能时的效率水平。
在一些实际应用中，热电元件通常会放置于汽车发动机或煤炭电力站等需要大量能源的系统中。
通过将废热转化为电能，电力系统的效率可以得到显著的提升。
第49卷第7期 2021年7月硅 酸 盐 学 报Vol. 49，No. 7 July ，2021JOURNAL OF THE CHINESE CERAMIC SOCIETY DOI ：10.14062/j.issn.0454-5648.20200925热电材料的研究现状与未来展望徐 庆1，赵琨鹏2，魏天然2，仇鹏飞1，史 迅1(1. 中国科学院上海硅酸盐研究所, 高性能陶瓷和超微结构国家重点实验室, 上海 200050；2. 上海交通大学材料科学与工程学院，上海 200240)摘 要：热电材料可以实现热能和电能的直接相互转换，在温差发电和固态制冷等领域具有重要应用，受到了学术界和工业界的广泛关注。
本工作首先简述了热电材料研究的相关背景，然后根据材料工作的温度，对室温附近、中温区以及高温区一些典型热电材料的最新研究进展进行了概述，重点介绍了材料的晶体结构特点和性能优化策略。
在此基础上阐述了热电能量转换技术在材料、器件和研发模式等方面所面临的困难和挑战。
最后，对热电材料未来的发展方向提出了展望。
关键词：热电材料；热电优值；热导率；电导率中图分类号：TG132.2+4, TN304.2 文献标志码：A 文章编号：0454–5648(2021)07–1296–10 网络出版时间：2021–06–29Development and Prospects of Thermoelectric MaterialsXU Qing 1, ZHAO Kunpeng 2, WEI Tianran 2, QIU Pengfei 1, SHI Xun 1(1. State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics,Chinese Academy of Sciences, Shanghai 200050, China; 2. School of Materials Science and Engineering,Shanghai Jiao Tong University, Shanghai 200240, China)Abstract: Thermoelectric materials (TE), which enable the direct energy conversion between heat and electricity, have attracted global attention in both academic and industrial sections, due to their significant applications in power generation and refrigeration. In this review, the research background of thermoelectrics will be introduced first, while the recent progress on several widely studied thermoelectric materials will be overviewed according to their working temperatures. In particular, their crystal structure characteristics and performance optimization strategies will be highlighted. The difficulties and challenges faced in thermoelectric technology, in terms of materials development, device fabrication and R &D modes, will be discussed. Finally, the prospect and expectation for the further development of thermoelectrics will be put forward.Keywords: thermoelectric materials; thermoelectric figure of merit; thermal conductivity; electrical conductivity热电材料又称为温差电材料，是一种依靠材料内载流子的运动来实现热能和电能直接相互转换的新型半导体功能材料。
氧化物热电材料研究进展徐飞;李安敏;程晓鹏;孔德明【摘要】由于能源危机正在到来,废热回收已经成为解决能源短缺问题的有效途径之一,热电材料在废热收集环节中占有举足轻重的地位.其中,氧化物热电材料拥有抗氧化能力强、热稳定性好、原料相对低廉、制备工艺相对简单、无毒、无污染、使用寿命长等传统合金材料不具备的优点,但由于低的电导率因而限制了其在热电性能方面的表现.已经有大量研究发现,可以通过元素掺杂,改善氧化物热电材料的热电性能,氧化物热电材料再次受到广大研究者的关注.综述了氧化物热电材料的研究进展与今后的发展方向,着重阐述了以BiCuSeO为代表的氧化物热电材料的基本结构、性能特征与研究进展;评述了BiCuSeO材料Bi位、Cu位和O位掺杂研究以及BiCuSeO的结构优化;并简单介绍了NaCo2 O 4、Ca3 Co4 O 9、SrTiO 3、ZnO、In2 O 3热电材料的研究情况.【期刊名称】《功能材料》【年(卷),期】2019(050)004【总页数】11页(P4038-4048)【关键词】废热回收;热电材料;氧化物热电材料;BiCuSeO;元素掺杂【作者】徐飞;李安敏;程晓鹏;孔德明【作者单位】广西大学资源环境与材料学院,广西有色金属及特色材料加工重点实验室,南宁 530004;广西大学资源环境与材料学院,广西有色金属及特色材料加工重点实验室,南宁 530004;广西大学资源环境与材料学院,广西有色金属及特色材料加工重点实验室,南宁 530004;广西大学资源环境与材料学院,广西有色金属及特色材料加工重点实验室,南宁 530004【正文语种】中文【中图分类】TB340 引言对于热电材料研究，早在1822年,塞贝克(Seebeck)就在《普鲁士科学院报》中描述了一个这样的现象，在相互连接的不同导体中, 由于温度差就会出现自由磁子。
将两种不同金属材料连接，将连线一端处于较高温度下，温度为T1(热端)，而另一端处于开路且较低温度下，温度为T2(冷端)，这时冷端存在一个开路电压ΔV，这个现象被称为Seebeck效应，ΔV被称为Seebeck电压，ΔV与热冷两端的温差ΔT成正比，即ΔV=SΔT=S(T1-T2)(1)其中，S为Seebeck系数，只与材料自身的电子能带结构相关。
专利名称：Method for production of high figure ofmerit thermoelectric materials发明人：Daryush Ila申请号：US14493297申请日：20140922公开号：US09537077B2公开日：20170103专利内容由知识产权出版社提供专利附图：摘要：A thermoelectric device and method based on creating a structure ofnanoclusters in a composite metal and insulator material by co-depositing the metal and insulator material and irradiating the composite material to create nanoclusters of metalwithin the composite material. In one variation, the composite material may be continuously deposited and concurrently irradiated. A further variation based on a multilayer structure having alternate layers of metal/material mixture. The alternate layers have differing metal content. The layer structure is irradiated with ionizing radiation to produce nanoclusters in the layers. The differing metal content serves to quench the nanoclusters to isolate nanoclusters along the radiation track. The result is a thermoelectric device with a high figure of merit. In one embodiment, the multilayer structure is fabricated and then irradiated with high energy radiation penetrating the entire layer structure. In another embodiment, layers are irradiated sequentially during fabrication using low energy radiation.申请人：Fayetteville State University地址：Fayetteville NC US国籍：US代理人：James Richards更多信息请下载全文后查看。
温差发电器1 概述1821年德国科学家塞贝克（T.J. Seebeck）发现了塞贝克效应，迄今已经快200年了。
第二次世界大战末发现半导体材料后，掀起了探索温差电材料和器件的热潮，促进了温差电理论和技术的发展。
二十世纪五十年代末六十年代初，空间技术飞速发展，急需一种长寿命、抗辐照的电源。
由于温差发电器是一种静态的固体器件，没有转动部件，体积小、寿命长，工作时无噪声，而且无须维护，成为空间电源研发的热点，大大刺激了温差电技术的发展。
1960年代初就有一批放射性同位素温差发电器（Radioisotope Thermoelectric Generator，英文缩写为RTG）成功地应用于空间、地面和海洋。
1963年美国将一个输出电功率2.7W的同位素温差发电器Snap3用在军用导航卫星上。
1969年到1972年美国人将5个Snap27同位素温差发电器成功地放在月面上作为月面科学仪器供电电源。
目前，常规的温差发电器的热电转换效率还不到10%。
与其它化学和物理电源电源相比，温差发电器的效率确实还较低。
但是，温差发电器具有其它电源尚不具备的优点，如寿命很长，应用环境和使用热源不受限制，特别是它可以利用所谓低级热发电－如工业废热、垃圾燃烧热、汽车排气管的余热以及太阳热、地热、海洋热能等，一直吸引着人们的青睐。
1990年起，出于环境保护和经济可持续发展的需要，许多国家的政府和公司投入资金用于开发温差电技术，在全球范围内又一次掀起了研发这种绿色电源的热浪。
目前，RTG是月球表面和深太空航天器的首选电源。
RTG也可以用作海上浮标、声纳的电源，或极地、边界的军用隐蔽电源、预警系统电源。
天然气燃料温差发电器已经在世界许多国家的输油、输气管线、通讯网络上获得了应用。
2 分类按使用的热源分类，温差发电器可分为放射性同位素温差发电器、核反应堆温差发电器、烃燃料温差发电器、低级热温差发电器等。
放射性同位素温差发电器(RTG)是将放射性同位素（如Pu-238, Sr-90,Po-210等）的衰变热能直接转换成电能的温差发电器。
KBr掺杂多晶SnSe化合物热电性能的研究杨实丹;斯剑霄;陈子洁;陈明【摘要】采用感应熔炼结合快速感应热压方法制备了KxSn1-xSeBrx(x=0,0.01,0.02,0.03,0.04,0.05,0.06)系列样品,研究了KBr掺杂对多晶SnSe热电性能的影响.当温度为373 K时,x=0.05的样品电导率达到39.12 S/cm,是纯SnSe的24倍;同时在T=810 K时获得一个较低的晶格热导率0.26 W/(m·K),峰值ZT达到了0.85,提高了70%.结果表明:KBr掺杂能有效提高SnSe材料在中低段(300~700 K)的热电性能.%The samples of KxSn1-xSeBrx(x=0,0.01,0.02,0.03,0.04,0.05 and 0.06) were prepared by induction melting and rapid induction hot pressing . It was investigated the effect on the thermoelectric properties of polycrystalline SnSe doped with KBr .An electrical conductivity of 39.12 S/cm was obtained at 373 K when x=0.05, which was 24 times higher than that of the pristine SnSe .Meanwhile the lattice thermal conductivity was reduced to 0.26 W/(m· K) at 810 K, and a peak of ZT 0.85 was achieved, which was 70%higher than that of pristine SnSe .It was found that KBr doping could effectively increase the thermoelec-tric performance of SnSe materials in a relatively wide mid and low temperature range (300~700 K).【期刊名称】《浙江师范大学学报（自然科学版）》【年(卷),期】2017(040)004【总页数】6页(P392-397)【关键词】SnSe;KBr;Seebeck系数;热电性能【作者】杨实丹;斯剑霄;陈子洁;陈明【作者单位】浙江师范大学数理与信息工程学院,浙江金华 321004;浙江师范大学数理与信息工程学院,浙江金华 321004;浙江师范大学数理与信息工程学院,浙江金华 321004;浙江师范大学数理与信息工程学院,浙江金华 321004【正文语种】中文【中图分类】TB34随着社会的发展，能源短缺和环境污染问题日益突出，已对当前人类形成巨大的挑战.热电材料因其自身具有实现热能与电能之间相互转换的功能而成为当前研究的热点[1-4].用无量纲的热电优值ZT来表征热电材料的能量转换效率，ZT=S2σT/κ，其中:S,σ,κ,T分别为材料的Seebeck系数、电导率、热导率和绝对温度.ZT值越高，材料的热电性能越优异.硒化锡(SnSe)是一种潜在的极具应用前景的热电材料.2014年，Zhao等[5]采用布里奇曼法制备了单晶SnSe，其沿b轴方向的ZT值高达2.6，超高的ZT值得益于SnSe较大的Seebeck系数及较低的晶格热导率0.23 W/(m\5K).然而单晶的制备条件苛刻，生产成本较高,且单晶易沿bc面解理，不适合于大规模商业化的开发应用.因此，对多晶SnSe块体材料的研究更具有意义.室温下，多晶SnSe材料含有较低的缺陷浓度(数量级为1017 cm-3)，使得其在低温段的电导率很低，提高多晶SnSe块体材料低温段的电导率是整体改善其热电性能的关键.元素掺杂常被用来调控材料的载流子浓度，提高材料的电导率.2015年，Chere等[6]用Na掺杂优化了多晶SnSe材料的载流子浓度，电导率被显著改善，ZT值提高至0.80.Leng等[7]通过用Ag作受主掺杂，在Ag0.01Sn0.99Se样品中载流子浓度接近1.9×1019 cm-3，在823 K时ZT值达到0.74.随后也报道了用Tl掺杂SnSe 材料，获得ZT值0.60[8].2016年，Cheng等[9]又用Br做施主掺杂，结合用Pb 合金化制备了多晶SnSe材料，发现Br和Pb共掺杂能同步优化材料的电性能和热性能，在773 K时ZT值达到1.20.实验表明，元素掺杂可以优化多晶SnSe块体材料的热电性能.因此，找到合适的掺杂元素并调整其成分配比，是获得高ZT值热电材料的重要途径.考虑到K和Na属同族、化学性质相似及Br-(0.196 nm)与Se2-(0.198 nm)离子之间半径相接近，笔者选取K和Br作为掺杂元素，采用快速感应熔炼结合快速感应热压(rapid induction melting followed by rapid hot pressing，RMP)法制备了KxSn1-xSeBrx (x=0,0.01,0.02,0.03,0.04,0.05,0.06)系列样品，在300～810 K温区内测试样品的热电性能，研究KBr掺杂对多晶SnSe 材料热电性能的影响.依次称取Sn(9.999 9%)粉、Se(9.999 9%)粉及KBr(9.99%)按KxSn1-xSeBrx(x=0,0.01,0.02,0.03,0.04,0.05,0.06)比例混合，然后将混合后的反应原料加载到石英玻璃管(直径15 mm)内，用高纯氩气多次洗气后再充入0.075 MPa氩气并封装，随后将封装好的石英玻璃管放入高频感应炉内进行感应熔炼.经高频感应炉缓慢加热3～4 min，待混合原料完全融化后，逐步增大功率，使温度保持在1 223 K，在该温度下饱和熔炼10 min.最后，减小功率，关闭电源，让其自然冷却至室温，得到样品铸锭.随后将熔炼好的铸锭取出，研磨成粒度为250～350目的粉末，装入高纯石墨模具(内径10 mm,外径50 mm,高度40 mm)中，采用感应热压快速烧结，烧结温度为823～833 K,升温速率为160～170 K/s,压力为50 MPa，热压时间为5 min.最后将热压好的样品取出用砂纸打磨、抛光等，得到目标待测样品.用Y2000型X射线粉末衍射仪(XRD)分析块体材料的物相组成，样品的Seebeck 系数及电导率由自行设计的热电性能测试系统进行测量，该系统与商业的ZEM-3测试仪器相比，误差为5%.用Ecopia HMS-3000型霍尔效应测试仪测量样品的室温霍尔系数.热扩散系数用LFA-457型激光导热分析仪测得，样品比热Cp引用文献[10-11] 中的数值，密度采用Archimede方法测试得到，样品相对密度大于97%.根据公式κ=DCpd 计算得到样品的热导率.其中：D为热扩散系数；d为密度.图1是KxSn1-xSeBrx(x=0,0.01,0.02,0.03,0.04,0.05,0.06)系列样品的XRD衍射图谱.由图1可看出，所有衍射峰均为SnSe的Pnma晶体结构(PDF#48-1224)，计算得到的晶格参数(a=1.151 3 nm,b=0.415 5 nm,c=0.445 2 nm)与文献报道的一致[6-7;12].与标准衍射峰相比，样品的(400)晶面衍射峰强度相对于(111)晶面明显增大，说明RMP法制备的样品晶粒具有一定的取向.由于KBr的含量较低，在XRD谱中没有观察到KBr的衍射峰，也没有观察到其他杂峰的出现.为了进一步确定掺杂元素在样品中的存在，笔者对x=0.04的样品进行了XPS(X-ray photoelectron spectroscopy)测试.从图2中可清晰地看到存在K的2p1/2峰和Br的3d5/2 ,3d3/2峰，对应的结合能分别为295.7,68.44和69.42 eV，计算样品中的化学成分符合设计配比的数值.XPS结果表明,KBr成功掺入了SnSe中.2.1 电输运性能图3是KxSn1-xSeBrx(x=0,0.01,0.02,0.03,0.04,0.05,0.06)系列样品电导率随温度变化的关系曲线.Tlt;575 K时，未掺杂样品的电导率小于1.60 S/cm，随着温度的升高逐渐增大，在810 K时电导率达到23.46 S/cm，呈现出明显的半导体输运特性，这与文献报道相一致[5-8].掺入KBr后，电导率在中低温段内被极大地改善.室温下，样品的电导率随着KBr掺入量的增加逐渐增大;当x=0.05时在全温段内达到最优;当xgt;0.05后呈现减小趋势，这可能与KBr在SnSe中溶解度有关.一方面，过多的Br占据Se位提供了更多的电子，使得样品中的空穴浓度降低；另一方面，部分KBr在SnSe中可能扮演了杂质的角色.对于x≤ 0.02的样品，电导率随温度变化的趋势与未掺杂的SnSe相似;当x≥ 0.03时，电导率在测量温区范围内都显著高于未掺杂的SnSe样品.最显著的是在较低温度373 K时的K0.05Sn0.95SeBr0.05样品，电导率达到39.12 S/cm，是未掺杂的SnSe样品(1.60 S/cm)的24倍.掺杂样品电导率的显著提高，受益于样品载流子浓度数量级的提升.如表1所示，掺杂少量的KBr到SnSe中后，样品载流子浓度被迅速提高到1018 cm-3.图4是KxSn1-xSeBrx(x=0,0.01,0.02,0.03,0.04,0.05,0.06)系列样品Seebeck系数随温度变化的曲线.掺杂样品的Seebeck系数为正，说明KBr掺杂的SnSe材料是P型导电，这与霍尔测量结果相一致.随着KBr掺杂量的增加，Seebeck系数受载流子浓度的影响逐渐减小，根据Mahan-Sofo理论[13]，式(1)中：m* 为态密度有效质量；S为Seebeck系数；n是载流子浓度;e是电子常数；h是普朗克常数；kB是波尔兹曼常数.由式(1)可知，样品的载流子浓度增大会导致Seebeck系数的减小.由图4知，Tlt;723 K时，所有掺杂样品的Seebeck系数随着温度的增加逐渐增加；而Tgt;723 K后，受少数载流子热激发的影响，Seebeck系数随温度的增加逐渐减小，最后趋于一致，这与电导率随温度变化趋势相对应.图5(a)给出的是KxSn1-xSeBrx(x=0,0.01,0.02,0.03,0.04,0.05,0.06)系列样品功率因子(PF)随温度的变化关系.PF=S2σ，PF能综合描述KBr掺杂对SnSe电输运性能的影响.未掺杂的SnSe材料在Tlt;523 K时，PF值小于0.30 μW\5cm-1\5K-2;T=810 K时，PF值随温度的增加逐渐增大至2.33 μW \5cm-1 \5K-2.掺杂KBr 后，样品的PF随温度变化是先增加后减小再增加，这与掺杂样品的电导率随温度的变化趋势相似.T=423 K时，x=0.05的样品PF值达到3.03 μW\5 cm-1 \5K-2，是未掺杂的SnSe样品(0.40 μW\5cm-1\5K-2)的7倍.在T=300～700 K时，x≥0.03样品的PF值显著地比未掺杂样品高，这主要得益于掺杂样品在该温度区间内电导率显著增加.表明在SnSe中掺杂KBr能有效地提高材料在中低温段的电性能.2.2 热输运性能图5(b)给出的是KxSn1-xSeBrx(x=0,0.01,0.02,0.03,0.04,0.05,0.06)系列样品总热导率(κtol)随温度的变化关系.室温下，SnSe样品的κtol为0.984 W/(m\5K)，随着温度升高逐渐减小至0.382 W/(m\5K)，然掺入KBr后，所有样品的κtol稍微比SnSe样品小.就x=0.05的样品来说,在室温下κtol是0.913 W/(m\5K)，当温度增加至810 K时减小到0.312 W/(m\5K)，该值显著低于未掺杂的样品在该温度下的值.图5(c)是样品晶格热导率(κlat)随温度变化关系.κlat=κtol-κele，κele为电子热导率，其满足Wiedemann-Franz定律，表达式为κele=LTσ，其中洛伦兹常数L取1.49×10-8 V2\5K-2 [14].T=810 K时，样品K0.05Sn0.95SeBr0.05的晶格热导率仅为0.260 W/(m\5K)，比基体材料在此温度下的值降低了32%.究其掺杂后样品晶格热导率降低的原因:一方面,K,Br替代Sn,Se位导致晶格缺陷，晶格缺陷对声子产生散射作用;另一方面,K与Sn原子质量差异大，引起了应力场的波动，这也增加了对声子的散射.此外,文献[15]报道，SnSe中引入K能抑制样品中Sn的氧化，能贡献给材料极低的热导率.这些因素都使掺杂的样品的晶格热导率降低.2.3 热电优值(ZT)图5(d)给出的是KxSn1-xSeBrx(x=0,0.01,0.02,0.03,0.04,0.05,0.06)系列样品的热电优值(ZT)随温度的变化关系.由图5(d)可知，纯二元SnSe样品在Tlt; 523 K内ZT值非常小(lt;0.027);Tgt;523 K，ZT值随着温度的升高而逐渐增加.然而,对于xgt;0.02的所有KBr掺杂的样品，其ZT值在中低温度区间(300～700 K)被显著提高.掺杂的样品在中低温段明显提高的ZT值源于显著增强的功率因子及较低的晶格热导率.810 K时，在样品K0.05Sn0.95SeBr0.05中获得最大ZT值0.85，该值是未掺杂的SnSe样品(0.50)的1.7倍，性能显著提高了70%.实验结果表明，SnSe 中掺杂适量的KBr对其热电优值的提高是非常有效的.采用感应熔炼结合快速感应热压(RMP)方法制备了KBr掺杂的SnSe样品.实验结果显示，KBr的引入能有效地提高多晶SnSe材料的载流子浓度，x=0.05的样品在373 K时电导率达到39.12 S/cm，是基体材料的24倍；掺杂样品的PF值在中低温段内被极大地提高.同时，KBr的掺入也贡献了一个显著低的晶格热导率0.26 W/(m\5K)；在810 K，样品K0.05Sn0.95SeBr0.05的最大ZT值为0.85，是纯SnSe样品(0.50)的1.7倍，性能提高了70%.【相关文献】[1]Li J F,Liu W S,Zhao L D,et al.High-performance nanostructured thermoelectric materials[J].NPG Asia Materials,2010,2(4):152-158.[2]Zebarjadi M,Esfarjani K,Dresselhaus M S,et al.Perspectives on thermoelectrics:from fundamentals to device applications[J].Energy amp; EnvironmentalScience,2012,5(1):5147-5162.[3]Biswas K,He J,Blum I D,et al.High-performance bulk thermoelectrics with all-scale hierarchical architectures[J].Nature,2012,489(7416):414-418.[4]Heremans J P,Jovovic V,Toberer E S,et al.Enhancement of thermoelectric efficiency in PbTe by distortion of the electronic density of states[J].Science,2008,321(5888):554-557.[5]Zhao L D,Lo S H,Zhang Y,et al.Ultralow thermal conductivity and high thermoelectric figure of merit in SnSe crystals[J].Nature,2014,508(7496):373-377.[6]Chere E K,Zhang Q,Dahal K,et al.Studies on thermoelectric figure 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碲及其化合物的合成、表征和热电性能研究了其生长机理。
关键词：热电材料，Te，形貌控制，生长机制，热电性能IIABSTRACTABSTRACTThermoelectric material is a new kind of functional material, which can realize direct conversion between heat and electricity by means of the movement of solid internal carrier. Its extensive application prospect in the field of energy and environment makes it a highly competitive alternative energy. But the low figure of merit (ZT value) of commercial thermoelectric material becomes a key factor constraining its application. Consequently, the most pressing problem is how to increase the figure of merit. As is known to us all, once thermoelectric material nanocrystallized, its thermal conductivity is decreased more markedly than conductivity, leading to a significant Seebeck coefficient, moreover, its morphological changes may highly improve its thermoelectric properties. Furthermore, among all the thermoelectric materials, Te as well as its compounds were studied earlier and developed more mature. Hence, Te and its compounds were chosen in our study. Many kinds of samples with different morphologies were synthesized by controlled growth, their growth mechanism as well as thermoelectric properties were systematically studied at the same time. The main findings are described as follows:1. We developed a convenient Lewis acid/base-assisted solvothermal method successfully completed the controlled synthesis of multi-morphology Te crystals. The morphological transformation from one-dimension (1D) nanorods and nanowires to 2D hierarchical flowerlike microarchitecture has been observed. Lewis acids/bases were found to be crucial for the formation of the products by not only acting as the pH regulator but also as the shape controller, owing to their hydrolysis in the solvent to in situ form H+/OH- and hydrates. The thermoelectric (TE) papameters of the bulk discs fabricated by dc hot press with the as-prepared Te NWs were investigated in a temperature range of 275-675K. Findings reveal that the as-prepared Te NWs possess a huge Seebeck coefficient (S), which arrives up to 80 mVK-1, more than 2 orders of magnitude higher than Bi2Te3, one of the best TE materials. Here we attribute the exceptionally high S of the as-prepared Te NWs to the following factors: (1) quantum confinement effects in Te NWs caused by their structure ballistic TeO2 quantum point contacts (QPCs); (2) increased local density of states near the Fermi energy level in Te NWs.2. On the basis of the above research results, we accomplished that the controlled growth of Te particles with distinctive morphologies, including flower-like, ball-flowers, nest-like, and sheet-likeIII碲及其化合物的合成、表征和热电性能研究structures. These structures, self-assembled from nanorods and nanosheets, are systematically studied by adjusting the reaction parameters, such as the amount of NaOH, the volume ratio of EG/EN, the amount of PVP, and reaction time. Results reveal that the morphology of Te microstructures can be easily controlled by simply altering the reaction conditions and that NaOH plays a crucial role in the final morphology of Te products. The growth mechanisms and morphology control of hierarchical Te microstructures are proposed and discussed.3. We successfully prepared monodispersed ZnTe microspheres via a facile, effective and reproducible one-pot solvothermal process devoid of any solid templates. In the meantime, the reaction conditions influencing the synthesis of these ZnTe microspheres are investigated, such as the zinc source and reaction time, in which the mechanism of formation of the microspheres was discussed.Keywords: Thermoelectric material, Tellurium, Morphology control, Growth mechanism, Thermoelectric performanceIV目录目录中文摘要 (I)ABSTRACT (III)第一章绪论 (1)1.1热电材料基本理论 (1)1.1.1热电材料研究历史 (1)1.1.2热电效应及热电参数 (2)1.2提高材料热电性能的途径 (6)1.2.1 重掺杂、带隙窄以及分子量较大的半导体材料 (6)1.2.2 超细晶或纳米化材料 (6)1.2.3 低维热电材料 (6)1.3热电材料研究进展 (8)1.3.1 Bi-Sb系列 (9)1.3.2 Bi-Te系列 (9)1.3.3 Pb-Te系列 (10)1.3.4 Si-Ge系列 (11)1.4纳米技术与纳米材料的简介 (12)1.4.1 纳米技术 (12)1.4.2 纳米材料 (12)1.5研究意义、思路及主要内容 (12)1.5.1 研究意义和思路 (12)1.5.2 主要内容 (13)参考文献 (14)第二章低维碲纳米材料的控制生长与热电性能研究 (19)2.1引言 (19)2.2实验部分 (20)2.2.1 实验试剂与仪器 (20)2.2.2 样品的制备 (21)2.3结果与讨论 (21)2.3.1 样品的合成原理分析 (21)2.3.2 样品的物相及形貌表征 (21)V碲及其化合物的合成、表征和热电性能研究VI2.3.3 Te纳米线的稳定性研究 (27)2.3.4 Te纳米线的热电性质研究 (28)2.4本章小结 (30)参考文献 (31)第三章溶剂热法合成形貌可控的碲微纳结构及机理研究 (35)3.1引言 (35)3.2实验部分 (36)3.2.1 实验试剂与仪器 (36)3.2.2 样品的制备 (36)3.3结果与讨论 (37)3.3.1 花状样品物相及形貌表征 (37)3.3.2 影响样品形貌的因素 (38)3.3.3 样品形成机理研究 (45)3.4本章小结 (46)参考文献 (47)第四章Z N T E微球的控制合成与机理研究 (49)4.1引言 (49)4.2实验部分 (49)4.2.1 实验试剂与仪器 (49)4.2.2 样品的制备 (50)4.3结果与讨论 (50)4.3.1 ZnTe微球的物相及形貌表征 (50)4.3.2 影响ZnTe微球形成的因素 (52)4.3.3 ZnTe微球的生长机制 (54)4.4本章小结 (55)参考文献 (56)第五章总结与展望 (59)5.1主要内容 (59)5.2问题与展望 (60)攻读硕士学位期间发表的学术论文及专利 (61)致谢 (62)第一章绪论第一章绪论随着社会的不断进步，能源和环境问题将成为21世纪主要的社会问题。
专利名称：HIGH FIGURE OF MERIT P-TYPE FeNbHfSbTHERMOELECTRIC MATERIALS AND THEPREPARATION METHOD THEREOF发明人：TIEJUN ZHU,CHENGUANG FU,XINBINGZHAO申请号：US15539316申请日：20150716公开号：US20180331268A1公开日：20181115专利内容由知识产权出版社提供专利附图：摘要：The present invention discloses a type of high figure of merit p-type FeNbHfSbthermoelectric material, whose composition is FeNbHfSb, wherein x=0.06˜0.2. The present invention also discloses the method to prepare these p-type FeNbHfSb thermoelectric materials. The ingots with nominal composition FeNbHfSb are prepared by levitation melting of stoichiometric amounts of Fe, Nb, Hf and Sb under an argon atmosphere. The obtained ingots are mechanically milled to get submicron-scale powders. The obtained powders are compacted by spark plasma sintering to obtain the final bulk p-type FeNbHfSb thermoelectric materials. The compositional elements of these p-type FeNbHfSb thermoelectric materials are abundant in the earth crust. The p-type thermoelectric materials also shows good high temperature stability and the preparation method are simple and high-yield. Therefore, the industrial production cost would be relatively cheap. The maximum zT value of the p-type thermoelectric materials is ˜1.45 at 1200K, which is the highest value among the p-type half-Heusler system.申请人：ZHEJIANG UNIVERSITY地址：HANGZHOU, Zhejiang Province CN国籍：CN更多信息请下载全文后查看。
2019年宁波市科学技术进步奖申报项目公示内容格式1、报奖项目名称：高品质硫族化合物热电半导体开发与发电技术应用基础研究2、项目类别：基础研究类3、推荐奖励等级：一等奖4、项目简介：项目所属科学技术领域：本项目属金属材料及无机非金属材料等多学科交叉领域。
项目介绍了主要两类宽带隙热电半导体材料。
解决了许多关键的科学问题。
多种材料性能已经达到了目前国内外中高温热电材料中较高的性能，部分已开展应用研究。
主要科技内容及技术指标：一．揭示了两类宽带隙半导体化合物的能带结构调控机制以大幅度改善了电学性能。
二．发现了进一步降低热导率的微（或超）结构优势。
可以在不需要加大冷速的前提下方便地突破这两类半导体晶格热导率的下限。
三．发现了三元黄铜矿结构中四方晶体结构的非中心对称特质, 并利用该特质有效地协调了声电输运性能。
材料的最高热电优值ZT=1.23 (n-型)和1.2-1.51(p-型)，已处于国际领先水平。
四．成功研制出两种光伏/热电复合发电原型器件。
其中一器件总发电量可以达到24.5 W，发电效率达23%。
促进行业科技进步作用及应用推广情况：在近9年内，已在高级别杂志上发表了27篇文章，授权国家发明专利9件。
使得宽带隙热电材料行为研究形成了自己的特色。
被国内外同行专家引用达362次，其中他引253次。
多篇论文被国际顶尖杂志Adv Mater.、JACS、AEM、AFM、Adv Sci.、Nano Energy、Chem. Mater.、Nano Lett.、ACS Nano、JMC(A,C)引用。
宽禁带半导体的热电研究得到了同行的广泛关注和认可。
例，关于In2Se3基及Cu-Ga(In)-Te三元黄铜矿半导体材料的热电行为多篇论文被西班牙的Rosario Vilaplana教授、澳大利亚昆士兰大学的J.Zhou教授以及荷兰代夫特技术大学资深教授A. Castellanos-Gomez等分别在AEM、Inorg.Chem.、Small和Nano Lett.等“review”article 中反复正面报道。
新能源材料与器件英语New Energy Materials and Devices.New energy materials and devices are key components of the emerging clean energy economy, enabling the development of sustainable energy sources and efficient energy storage and conversion technologies. These materials and devices encompass a wide range of electrochemical, photovoltaic, and thermal energy applications, offering promising solutions for addressing global energy challenges.Electrochemical Energy Storage.Electrochemical energy storage systems, such as batteries and supercapacitors, play a crucial role in storing electricity from renewable energy sources and providing backup power. The development of new energy materials and devices for electrochemical energy storage is critical for improving energy density, power density, cycle life, and safety.Batteries: Batteries are electrochemical devices that store chemical energy and convert it into electrical energy through electrochemical reactions. Advancements in battery materials, including cathode materials (e.g., lithium-ion, lithium-sulfur), anode materials (e.g., graphite, silicon), and electrolytes, aim to enhance energy density, reduce charging time, and improve stability.Supercapacitors: Supercapacitors are electrochemical devices that store energy electrostatically at theinterface between two conductive materials separated by an electrolyte. New materials and device architectures are being explored to increase capacitance, power density, and energy density, making supercapacitors suitable for applications requiring high-rate energy delivery.Photovoltaic Energy Conversion.Photovoltaic devices, such as solar cells and solar panels, convert sunlight into electricity through the photovoltaic effect. The efficiency of photovoltaic energyconversion is determined by the optical and electrical properties of the semiconductor materials used.Solar Cells: Solar cells are the fundamental building blocks of photovoltaic systems, generating electricity when exposed to sunlight. New materials and device structuresare being developed to improve light absorption, reduce carrier recombination, and enhance energy conversion efficiency.Solar Panels: Solar panels consist of multiple solar cells connected together to increase the total power output. Advancements in module design, packaging, andinterconnection technologies focus on improving durability, reducing costs, and maximizing energy yield.Thermal Energy Conversion.Thermal energy conversion technologies involve the conversion of heat into electricity. New energy materials and devices for thermal energy conversion include thermoelectric materials and thermophotovoltaic devices.Thermoelectric Materials: Thermoelectric materials generate electricity from a temperature gradient, enabling waste heat recovery and power generation from low-gradeheat sources. Research efforts are directed towards developing materials with high thermoelectric figure of merit, which quantifies the efficiency of thermal energy conversion.Thermophotovoltaic Devices: Thermophotovoltaic devices convert thermal radiation directly into electricity through the photovoltaic effect. New materials and device designs aim to improve absorption efficiency, reduce thermal losses, and enhance overall performance.Materials for New Energy Applications.The development of new energy materials and devices requires advanced materials with specific properties and functionalities. These materials include:Electrodes: Electrodes are essential components ofelectrochemical energy storage and conversion devices, responsible for charge transfer and electrochemical reactions. New materials with high electrical conductivity, electrochemical stability, and specific surface area are being explored.Semiconductors: Semiconductors are the active materials in photovoltaic devices, responsible for light absorption and charge separation. New semiconductors with optimized bandgaps, carrier mobilities, and light absorption properties are being developed.Dielectrics: Dielectrics are insulating materials used in capacitors and transistors, enabling charge storage and electronic switching. New dielectric materials with high permittivity and electrical stability are being explored.Superconductors: Superconductors are materials that exhibit zero electrical resistance below a critical temperature. Superconducting materials are being investigated for use in high-efficiency energy transmission and storage.Summary.New energy materials and devices are essential for the transition towards a sustainable energy future. The development of these materials and devices requires a multidisciplinary approach, combining materials science, electrochemistry, photovoltaic physics, and thermal engineering. By pushing the boundaries of materials science and engineering, new energy materials and devices will enable efficient and reliable energy storage, conversion, and utilization, paving the way for a cleaner and more sustainable energy landscape.。
温差发电片若两面温差能达到摄氏60度，则发电电压可达到3.5V，电流可达到3-5A温差发电实验一【实验目的】演示西伯克（Seebeck）效应和帕尔帖（Peltier）效应。
【实验器材】热电转换仪，两个玻璃烧杯，温度计（两个），直流稳压电源。
如图77-1所示【实验原理】1. 西伯克(seebeck)效应有两种不同导体组成的开路中，如果导体的两个结点存在温度差，这开路中将产生电动势E，这就是西伯克效应。
由于西伯克效应而产生的电动势称作温差电动势。
材料的西伯克效应的大小，用温差电动势率a表示。
材料相对于某参考材料的温差电动势率为由两种不同材料P、N所组成的电偶，它们的温差电动势率等于与之差，即热电制冷中用P型半导体和N型半导体组成电偶。
两材料对应的和，一个为负，一个为正。
取其绝对值相加，并将直接简化记作a，有(77-3)2. 帕尔帖(peltire)效应电流流过两种不同导体的界面时，将从外界吸收热量，或向外界放出热量。
这就是帕尔帖效应。
由帕尔帖效应产生的热流量称作帕尔帖热，用符号表示。
对帕尔帖效应的物理解释是：电荷载体在导体中运动形成电流。
由于电荷载体在不同的材料中处于不同的能级，当它从高能级向低能级运动时，便释放出多余的能量；相反，从低能级向高能级运动时，从外界吸收能量。
能量在两材料的交界面处以热的形式吸收或放出。
材料的帕尔贴效应强弱用它相对于某参考材料的帕尔贴系数表示(77-4)式中----- 流经导体的电流，单位A。
类似的，对于P型半导体和N型半导体组成的电偶，其帕尔贴系数（或简单记作）有(77-5)帕尔贴效应与西伯克效应都是温差电效应，二者有密切联系。
事实上，它们互为反效应，一个是说电偶中有温差存在时会产生电动势；一个是说电偶中有电流通过时会产生温差。
温差电动势率a与帕尔贴系数之间存在下述关系(77-6)式中-- 结点处的温度，单位。
3. 汤姆逊效应电流通过具有温度梯度的均匀导体时，导体将吸收或放出热量。
1054Chem.Mater.2010,22,1054–1058DOI:10.1021/cm902009tHigh Thermoelectric Figure of Merit and Nanostructuring in Bulk p-type Ge x(Sn y Pb1-y)1-x Te Alloys Following a SpinodalDecomposition Reaction†Yaniv Gelbstein,*Boaz Dado,Ohad Ben-Yehuda,Yatir Sadia,Zinovy Dashevsky,andMoshe P.DarielDepartment of Materials Engineering,Ben-Gurion University of the Negev,Beer-Sheva84105,IsraelReceived July6,2009.Revised Manuscript Received August6,2009The use of thermoelectricity for direct energy conversion from thermal to electrical energy has a long-standing history.We report that the complex p-type Ge(Sn,Pb,Te)Te alloys upon suitable alloying with SnTe can be designed to obtain very high ZT values of up to1.2because of both optimal electronic transport properties and minimal lattice thermal conductivity.Such alloys follow a spinodal decomposition reaction,leading to an ordered periodic nano-structure that is effective in the scattering of phonons and reduction of the lattice thermal conductivity.IntroductionThermoelectricity is concerned with the interactionbetween thermal and electrical phenomena.The mostcommon applications are concerned with the conver-sion of thermal energy(or heat)into electrical powerand with the use of electrical current for cooling.Thedimensionless thermoelectric figure of merit(ZT),ex-pressed in eq1,is widely used as a measure of thethermoelectric efficiency with respect to the material’sproperties.ZT¼R2σK Tð1Þwhere Z is the thermoelectric figure of merit,R theSeebeck coefficient,σthe electrical conductivity,κthethermal conductivity,and T the absolute temperature.Materials with high ZT values are known as thermo-electric materials.Today’s commercial materials have aZT=1,leading to conversion efficiency on the order ofseveral percent(∼6%).Increasing ZT can be achievedby either increasing the numerator of ZT,P=R2σ, known as the power factor,or decreasing the thermalconductivity,κ(the denominator of ZT in eq1).κis asum of two major contributions,the lattice thermalconductivityκL(due to phonons flow)and the electronicthermal conductivityκe(due to electronic flow),as de-scribed in eq2.K¼K LþK eð2ÞCurrently,PbTe-based thermocouples,with an n-type leg (doped with PbI2for achieving maximal ZT values of about 1.1in the temperature range of400-600°C for carrier concentrations of2-6Â1019cm-3,respectively)and a p-type leg(alloyed with SnTe)have been employed in real applications.1,2The latter,in the form of Pb1-x Sn x-Te,unfortunately display much lower ZT values(e0.5) than those for the n-type PbTe component.Higher ZT values(∼0.8at450°C)for p-type legs were found in Na-doped PbTe;3however,because of the brittle nature of this material and the correspondent poor mechanical pro-perties,its usage in practical applications was eliminated.3,4 Therefore,further improvement of the ZT values of the p-type legs is a significant challenge that carries substantial benefit.Recently,optimally doped pseudobinary Pb1-x Ge x Te compounds were proposed as potential candidates to im-prove the thermoelectric performance of p-type legs.5,6 However,the ZT values of these pseudobinary alloys can be further increased by decreasing the lattice thermal con-ductivity due to the presence of additional structural defects. Recently,very low thermal conductivity values were ob-served in several nanostructured PbTe-based materials.7-12 One mechanism for nanopattern generation is based on the†Accepted as part of the2010“Materials Chemistry of Energy Conversion Special Issue”.*Corresponding author.E-mail:yanivge@bgu.ac.il.(1)Gelbstein,Y.;Dashevsky,Z.;Dariel,M.P.Physica B2005,363,196–205.(2)Gelbstein,Y.;Dashevsky,Z.;Dariel,M.P.Physica B2007,391,256–265.(3)Gelbstein,Y.;Gotesman,G.;Lishzinker,Y.;Dashevsky,Z.;Dariel,M.P.Scr.Mater.2008,58,251–254.(4)Gelbstein,Y.;Dashevsky,Z.;Dariel,M.P.J.Appl.Phys.2008,104,033702.(5)Gelbstein,Yaniv;Dashevsky,Zinovi;Dariel,Moshe P.Phys.Status Solidi2007,1(No.6),232–234.(6)Gelbstein,Y.;Ben-Yehuda,O.;Pinhas,E.;Edrei,T.;Sadia,Y.;Dashevsky,Z.;Dariel,M.P.J.Electron.Mater.2009,38(7),1478.(7)Poudeu,P.F.P.;D’Angelo,J.;Downey,A.D.;Short,J.L.;Hogan,T.P.;Kanatzidis,M.G.Angew.Chem.,Int.Ed.2006,45,1–5. (8)Sootsman,J.R.;Pcionek,R.J.;Kong,H.;Uher,C.;Kanatzidis,M.G.Chem.Mater.2006,18,4993–4995./cm Published on Web08/21/2009r2009American Chemical SocietyArticle Chem.Mater.,Vol.22,No.3,20101055spinodal decomposition.Spinodal decomposition is a me-chanism for phase separation that leads to a characteristicmodulated structure that can be exploited to control themicrostructure at the nanometer scale.13Nanostructures for spinodal decomposed systems werereported for TiO2-SnO2,13Mn-Cu,14and Cu-Ni-Sn15 alloys.Recently,a reduction of the lattice thermal con-ductivity and a corresponding ZT enhancement inPb1-x Sn x Te-PbS system was attributed to nano structuresresulting from the spinodal decomposition.12Alloying of(GeTe)x(PbTe)1-x compounds with SnTecan result in a spinodal decomposition with changedperiodicity that depends on the heat treatment.16To thebest of our knowledge,the nanostructure and the transportproperties of these alloys have not yet been investigated.The present communication is concerned with develop-ment of highly efficient nanostructured p-type Ge x-(Sn y Pb1-y)1-x Te alloys for thermoelectric applications,using spark plasma sintering(SPS).The thermoelectricfigure of merit was optimized by means of both alloyingand doping methods.Two alloys in this family,Ge0.5Sn0.25Pb0.25Te(undoped,Ag-doped and Bi2Te3-doped)and Ge0.6Sn0.1Pb0.3Te,were prepared and inves-tigated.The results were compared to a GeTe referencesample.Experimental DetailsSynthesis.GeTe,Ge0.5Sn0.25Pb0.25Te(undoped,3mol%Ag-doped,and3mol%Bi2Te3-doped),and Ge0.6Sn0.1Pb0.3Te alloyswere prepared according to the following procedure:(a)sealingthe source materials(purity of5N)at appropriate concentrationsin a quartz ampule under a vacuum of1Â10-5Torr,(b)meltingthe alloys in a rocking furnace at800°C for1h followed by waterquenching,(c)milling the compound to a maximal particle size of60mesh powder,and(d)Spark Plasma Sintering(SPS)(type HPD5/1FCT Systeme GmbH)at450°C for30min under amechanical pressure of32MPa for GeTe and at550°C for60min under a mechanical pressure of25MPa for the Ge x(Sn y-Pb1-y)1-x Te alloys.The different SPS parameters were optimizedin order to obtain dense samples(>96%)without any lateralcracks for the various investigated alloys.Electrical Properties.Seebeck coefficient and the electricalconductivity measurements were performed in a self-con-structed apparatus under an argon atmosphere up to∼450°Cat a heating rate of3°C/min.For Seebeck coefficient measure-ments,an auxiliary heater was used to maintain a temperature difference of10°C between the extremities of the samples. Electrical conductivity was measured by the“four-probe”method using an alternating power source of1V/50Hz.Thermal Conductivity.The thermal conductivity(κ)was determined as a function of temperature from room tempera-ture to500°C using the flash diffusivity method(LFA457, Netzsch).The front face of a disk-shaped sample(L=12mm, thickness≈1-2mm)is irradiated by a short laser burst and the resulting rear face temperature is recorded and analyzed.Ther-mal conductivity values were calculated using the equation κ=R3C P3F,where R is the thermal diffusivity,C P is the specific heat(measured using differential scanning calorimetry,STA 449,Netzsch),and F is the bulk density of the sample(calculated from the sample’s geometry and mass).Microscopy.The microstructure of Ge0.5Sn0.25Pb0.25Te (undoped and3mol%Bi2Te3-doped)was investigated by optical microscopy(Zeiss Axiovert25.Etching prior to optical microscopy by immersion for few seconds in a60mL solution composed of10mL of alcohol,10g of potassium hydroxide, 17.5mL of glycerol,and22.5mL of distilled water),high-resolution scanning electron microscopy(Jeol-7400F HRSEM), transmission electron microscopy(TEM,FEI TECNAI,G2), and high-resolution transmission electron microscopy(Jeol-2010HRTEM).Specimens used for the TEM and HRTEM were prepared as follows.Small square shape pieces with approximate sizes of 5mmÂ5mmÂ2mm were first cut from the spark plasma sintered disk using a low speed diamond wheel saw.The samples were then mounted inside a copper tube(L=3mm)and hand-polished with subsequently increasing grit(1000-1500)sand paper to about200-300μm in thickness.Samples were then thinned using a Gatan precision dimple grinder and ion milled to electron transparency using a Gatan precision ion polishing system(PIPS).Results and DiscussionAll the investigated Ge x(Sn y Pb1-y)1-x Te alloys dis-played a microscale quasi-ordered periodic fishbone structure,the orientation of which depended on the original high temperature cubic phase grain in which the demixing process took place.A typical structure of these alloys as observed in Ge0.5Sn0.25Pb0.25Te is shown in Figure1.From the optical microscope(a)and HRSEM (b)micrographs of this figure,the wavelength of the dissociation as determined from the side branches of the fishbone was about10μm.High-magnification TEM micrograph(c)revealed a finer periodic nanostructure with a wavelength of about100nm.In addition,electron-dispersive spectroscopy(EDS)analysis showed that the fishbone structure is Pb-rich,whereas the matrix is Ge-rich.The bright aspect of the Pb-rich regions(Pb is heavier than Ge)is obtained in the backscattered electron (BSE)examination mode of the HRSEM(b).Line scan EDS analysis crossing the fishbone patterns and the surrounding matrix revealed continuous and complemen-tary compositional modulations of Pb and Ge when scanning across the side-branches of the fishbone pattern (Figure1).It is noteworthy that the Sn composition remained constant while crossing the Pb-rich fishbone lamellas through the surrounding Ge-rich matrix.Higher magnification of HRTEM revealed that the Pb-rich(9)Poudeu,P.F.P.;D’Angelo,J.;Kong,H.;Downey,A.D.;Short,J.L.;Pcionek,R.;Hogan,T.P.;Uher,C.;Kanatzidis,M.G.J.Am.Chem.Soc.2006,126,14347–14355.(10)Androulakis,J.;Hsu,K.F.;Pcionek,R.J.;Kong,H.;Uher,C.;D’Angelo,J.;Downey,A.D.;Hogan,T.P.;Kanatzidis,M.G.Adv.Mater.2006,18,1170–1173.(11)Hsu,K.F.;Loo,S.;Guo,F.;Chen,W.;Dyck,J.S.;Uher,C.;Hogan,Tim;Polychroniadis,E.K.;Kanatzidis,M.G.Science 2004,303,818–820.(12)Androulakis,J.;Lin,C.-H.;Kong,H.;Uher,C.;Wu,C.-I.;Hogan,T.;Cook,B.A.;Caillat,T.;Paraskevopoulos,K.M.;Kanatzidis, M.G.J.Am.Chem.Soc.2007,129,9780–9788.(13)Chaisan,W.;Yimnirun,R.;Ananta,S.;Cann,D.P.J.Solid StateChem.2005,178,613–620.(14)Yin,F.;Ohsawa,Y.;Sato,A.;Kawahara,K.Acta Mater.2000,48,1273–1282.(15)Zhao,J.-C.;Notis,M.R.Acta Mater.1998,46,4203–4218.(16)Yashina,L.V.;Leute,V.;Shtanov,V.I.;Schmidtke,H.M.;Neudachina,V.S.J.Alloys Compd.2006,413,133–143.1056Chem.Mater.,Vol.22,No.3,2010Gelbstein et al. fishbone structure by itself composed from smaller scalemodulations in the10nm range(Figure2).These con-tinuous modulations without any sharp borders,as inprecipitates,are possibly consistent with the continuousnature of the spinodal decomposition generated struc-ture.The electrons diffraction patterns in this figureshow a doublet pattern(two nonconcentric periodicreflections),indicating the presence of two similar struc-tures with closely related lattice parameters providingadditional evidence to the decomposition of Ge x(Sn y-Pb1-y)1-x Te into Ge and Pb rich phases.In addition to the micro and nanoperiodic Pb-richmodulations,the3mol%Bi2Te3doped Ge0.5Sn0.25-Pb0.25Te sample showed Birich nano precipitates with atypical size of50nm(Figure3),which were not observedat any of the other investigated compositions.The effectof these precipitates will be discussed later.The temperature dependence of the Seebeck coeffi-cient,electrical conductivity and thermal conductivity of Ge0.5Sn0.25Pb0.25Te(undoped,3mol%Ag-doped, and3mol%Bi2Te3-doped)and Ge0.6Sn0.1Pb0.3Te alloys compared to GeTe are presented in Figures4-6.We discuss first the doping influence of Ge0.5Sn0.25-Pb0.25Te by Ag and Bi2Te3on the thermoelectric proper-ties.By comparing curves2,3,and5for Ag doping, undoped,and Bi2Te3doping,respectively,in Figures4-6,a consistent trend of decreasing Seebeck coefficient and increasing electrical and thermal conductivity values forFigure1.(a)Optical microscopy,(b)backscattered electrons HRSEM, and(c)TEM micrographs of Ge0.5Sn0.25Pb0.25Te.Figure2.HRTEM micrograph and typical electron diffraction patterns of Ge0.5Sn0.25Pb0.25Te.Figure3.HRSEM of scattered Bi-rich nanoprecipitates in3mol% Bi2Te3-doped Ge0.5Sn0.25Pb0.25Te.Figure4.Temperature dependence of the Seebeck coefficient for(1) GeTe,(2)Ge0.5Sn0.25Pb0.25Teþ3mol%Ag,(3)Ge0.5Sn0.25Pb0.25Te, (4)Ge0.6Sn0.1Pb0.3Te,and(5)Ge0.5Sn0.25Pb0.25Teþ3mol%Bi2Te3. Figure5.Temperature dependence of the electrical conductivity for the various prepared alloys.Notations are according to Figure4.Figure6.Temperature dependence of the thermal conductivity for the various prepared alloys.Notations are according to Figure4.Article Chem.Mater.,Vol.22,No.3,20101057Ag doping,as compared to the undoped condition,is apparent.This evidence indicates an Ag-acceptor behavior in the investigated alloys,leading to an increased carrier concentration.For Bi 2Te 3doping (curve 5in Figures 4-6),the opposite trend is observed,showing a donor behavior in the investigated alloys and leading to a decreased carrier concentration as compared to the undoped sample (curve 3).These trends show the potential of Bi and Ag to serve as active impurities (donors and acceptors,respectively)in Ge 0.5Sn 0.25Pb 0.25Te for tuning the optimal carrier concen-tration for thermoelectric applications.By comparing of these curves to the GeTe curve (curve 1in Figures 4-6),we observe that all the Ge 0.5Sn 0.25Pb 0.25Te curves (2,3,and 5)yield higher R and lower σand κvalues,as compared to the GeTe (curve 1),indicating a reduced carrier concentration at all the doping levels in Ge 0.5Sn 0.25Pb 0.25Te,as compared to pure GeTe.Pure GeTe shows a very high holes concen-tration of p ≈6Â1026m -3.It is well-known that for thermoelectric applications,much lower carrier concentra-tions are needed for optimal performance.This stands behind Bi doping of GeTe (p ≈2Â1026m -3),for increasing the thermoelectric performance.6Therefore,the reduced carrier concentrations obtained by using Ge 0.5Sn 0.25-Pb 0.25Te (in all of the investigated doping levels,curves 2,3,and 5)as compared to GeTe (curve 1),is desirable.Variation of the alloying of Ge x (Sn y Pb 1-y )1-x Te from undoped Ge 0.5Sn 0.25Pb 0.25Te (curve 3)to undoped Ge 0.6Sn 0.1Pb 0.3Te (curve 4)does not result in any dramatic changes of the investigated transport properties.This beha-vior can be attributed to the carrier compensation obtained by increasing the GeTe amount (from 50to 60at %)and decreasing the SnTe amount (from 25to 10at %),both p -type compounds with very high hole concentrations.The temperature dependence of the lattice thermal con-ductivity,κL ,for GeTe,Ge 0.5Sn 0.25Pb 0.25Te (undoped and 3%Bi 2Te 3doped),and Ge 0.6Sn 0.1Pb 0.3Te is presented in Figure 7.κL values were calculated as followed:1.Fermi Energy Calculation.Fermi energy (η)was calculated at low temperatures (<250°C),for assuring an extrinsic region,using eq 3and the measured Seebeck coefficient values (Figure 4)R ¼k e 52þr ÀÁF 3=2þr 32þr F1=2þr -η264375ð3ÞWhere,e ,k ,F r ,η,and r are the electron charge,Boltz-mann constant,Fermi integral,reduced Fermi energy(equal to [E F -E V ]/kT for p -type materials),and the scattering mechanism parameter (equal to -0.5for the case of scattering by acoustic phonons as the dominant scattering mechanism,as is the case of GeTe).Equation 3is valid for a quadratic dependence of the carrier energy on the crystal momentum and a power dependence of the mean free time between electron colli-sions,τon the kinetic energy ξ(τ=τo ξr ,where τo is the constant),as for the case of GeTe-based alloys.The heavy hole valence band,present in GeTe,was not taken into account,on account of its minor influence at low temperatures up to very high carrier concentrations of ∼7Â1026m -3.62.Electronic Thermal Conductivity Calculation.The electronic contribution to the thermal conductivity,κe ,was calculated using the Wiedemann -Franz relation (eq 4)and the measured electrical conductivity values (Figure 4).K e ¼L σTð4ÞWhere,L and T are Lorenz number and absolute tem-perature,respectively.Lorenz number,given by eq 5,was calculated using the Fermi energy (η)values obtained in section 1.L ¼k e2r þ72ÀÁr þ32F r þ5=2ðηÞF r þ1=2ðηÞ-r þ52ÀÁ2F 2r þ3=2ðηÞr þ32 F 2r þ1=2ðηÞ264375ð5Þttice Thermal Conductivity Calculation.Finally,the lattice contribution to thermal conductivity,κL ,was calculated by subtraction of k e from the meas-ured total thermal conductivity,κ,(Figure 6),accord-ing to eq 2.It is clear from the calculated lattice thermal conduc-tivity values of Figure 7that alloying of GeTe with both PbTe and SnTe to obtain nanostructured Ge 0.5Sn 0.25-Pb 0.25Te or Ge 0.6Sn 0.1Pb 0.3Te,which follow a spinodal decomposition reaction,results in a major reduction (∼50%)of the lattice thermal conductivity.The room temperature κL values for Ge 0.5Sn 0.25Pb 0.25Te or Ge 0.6Sn 0.1Pb 0.3Te are about 0.8W/mK,as compared to a value of ∼1.6W/mK that was found for pure GeTe.This reduction can be attributed to phonon scattering by the nano-size ordered modulations of the spinodal de-composition in Ge x (Sn y Pb 1-y )1-x Te.It can be also seen from Figure 6that Bi 2Te 3doping of Ge 0.5Sn 0.25Pb 0.25Te results in a further reduction of the lattice thermal con-ductivity (to a room temperature value of ∼0.55W/mK),which may be attributed to additional nano Bi precipita-tion in this alloy.The temperature dependence of the dimensionless thermoelectric figure of merit,ZT ,for the investigated alloys is presented in Figure 8.All the investigated alloysFigure 7.Temperature dependence of the lattice thermal conductivity for GeTe,Ge 0.5Sn 0.25Pb 0.25Te (undoped and 3%Bi 2Te 3-doped),and Ge 0.6-Sn 0.1Pb 0.3Te.1058Chem.Mater.,Vol.22,No.3,2010Gelbstein et al.display higher ZT values over most of the investigated temperatures as compared to pure GeTe.The highest ZT values were obtained for undoped Ge 0.5Sn 0.25Pb 0.25Te with a maximal value of ∼1.2at 450°C,underlining the high potential of this composition as a p -type leg in practical thermoelectric applications.ConclusionsGe 0.5Sn 0.25Pb 0.25Te (undoped,3mol %Ag-doped,and 3mol %Bi 2Te 3-doped)and Ge 0.6Sn 0.1Pb 0.3Te alloys,following a spinodal decomposition reaction,were pre-pared using spark plasma sintering,characterized by electronic microscopy and transport properties measure-ments,and compared to a reference GeTe sample.The spinodal decomposition of the matrix to both GeTe-and PbTe-rich phases was observed as periodic compositional modulations both in the micro-and nano-(down to 10nm)scales.The lattice thermal conductivity was calculated by reduction of the electronic thermal conductivity (calculated by Fermi -Dirac statistics,taking into account variations of Lorenz number with Fermi energy)from the measured total thermal conductivity.Major reduction (∼50%)of the lattice thermal conductivity was observed in undoped Ge 0.5Sn 0.25Pb 0.25Te and Ge 0.6Sn 0.1Pb 0.3Te alloys.Doping optimizations of Ge 0.5Sn 0.25Pb 0.25Te by Bi 2Te 3revealed a further reduction of the lattice thermal conductivity due to nanosized scattered Bi precipitates.Bi was found to serve as a donor,whereas Ag was found to serve as an acceptor in these alloys.Very high ZT values were obtained for un-doped Ge 0.5Sn 0.25Pb 0.25Te with a maximal value of ∼1.2at 450°C,indicating the high potential of this composition to serve as a p -type legs in practical thermoelectric applica-tions.Figure 8.Temperature dependence of the dimensionless thermoelectric figure of merit for the various prepared alloys.Notations are according to Figure4.。
