Synthesis of Zintl Phases for Thermoelectric Applications

技术摘要：该项目由固态和材料化学计划支持，专注于合成新的锌相，加入过渡金属，以便在费米水平(通过部分填充的d轨道)获得高的态密度(DOS)，从而获得高的塞贝克系数(功率因数)，从而获得高的zT。纳米结构将被用来进一步降低导热系数。相的合成将通过助熔剂和冶金路线。利用单晶和粉末X射线衍射、扫描电子显微镜和透射电子显微镜、元素波色散微探针和电感耦合等离子体质谱分析等一系列物理表征技术，以及平行的电磁测量，可以将结构和相组成与电子和热输运性质关联起来。该项目的最终目标是发现具有高zT的新材料，用于将废热直接转化为电能。基于在锌相中表现出的高ZT的最新结果，该建议将合成策略与物理和化学性质的表征紧密地联系在一起，从而提供有效的反馈来指导这些热电系统的改进。非技术摘要：用于发电的热电设备直接将热能转换为电能，需要最少的维护，并且可以在很大的温度范围(室温到1000摄氏度)下运行。热电材料用优值系数zT来描述，它与材料将热流转化为电能的能力有关--该值越高，效率就越高。最近发现的ZT为1.0或更高的Zintl相突出了继续探索新材料的重要性。锌相是一种化合物，它包含碱、碱土和稀土元素等阳离子，它们向由主族元素组成的聚阴离子单元提供电子，如元素周期表的第13、14和15族元素。这些类型的化合物自然提供低导热系数，这是热电设备的要求。随着zT的提高，废热回收固态发电的潜力为研究在高温(300摄氏度)下具有稳定性和最佳性能的新型Zintl相材料提供了一个框架。该项目支持处于初始阶段的少数群体和妇女(从高中到大学，从大学到研究生)，同时培训研究生从事科学工作。学生通过实践培训、探索和向更广泛的科学界传播研究来发展科学、社会和专业技能。正在研究的课题包括材料合成和性能测量、材料合成和结构-性能相关性的基础培训，为发展热能到电能的转换和推进与技术相适应的多学科研究提供了重要基础。这项研究将在国家和国际会议上公布，研究结果将发表在同行审查期刊上。此外，PI还通过ACS SEED计划(高中)、MURPPS(本科生)和AGEP(研究生)计划支持学生，这些计划的重点是增加校园内科学方面代表性不足的群体。ChemWiki将用于通过写作和批判性评估来加强学生的学习。

TECHNICAL SUMMARY: This project, supported by the Solid State and Materials Chemistry program focuses on the synthesis of new Zintl phases, incorporating transition metals in order to target a high density of states (DOS) at the Fermi level (through partially filled d orbitals) to obtain high Seebeck coefficient (Power factor) and therefore high zT. Nanostructuring will be employed to further reduce the thermal conductivity. Phases will be synthesized via flux and metallurgical routes. Utilizing a suite of physical characterization techniques including single crystal and powder X-ray diffraction, SEM and TEM, elemental wave dispersive microprobe and ICP-MS analysis, parallel electrical and magnetic measurements, the structure and phase composition will be correlated with electronic and thermal transport properties. The ultimate goal of the project is to discover new materials with high zT for the direct conversion of waste heat into electricity. Building upon recent results of demonstrated high zT in Zintl phases, this proposal closely links synthetic strategies with characterization of physical and chemical properties, thus providing efficient feedback to guide improvement of these thermoelectric systems.NON-TECHNICAL SUMMARY: Thermoelectric devices for power generation convert thermal energy directly into electrical energy, require minimal maintenance, and can be operated over a large temperature range (room temperature to 1000 degrees C). Thermoelectric materials are described by a figure of merit, zT, which relates to how well a material converts heat flow to electricity - the higher the value, the greater the efficiency. Recent discoveries of Zintl phases with zT of 1.0 or greater highlight the importance of continued exploration of new materials. A Zintl phase is a compound which contains both cations such as alkali, alkaline earth, and rare earth elements which donate electrons to polyanionic units composed of main group elements such as those from groups 13, 14, and 15 of the periodic table. These types of compounds naturally provide low thermal conductivity which is a requirement for thermoelectric devices. With higher zT, the potential for solid-state power generation from waste heat recovery provides a framework for investigating new Zintl phase materials with stability and optimal properties at high temperatures (300 degrees C). This project supports minorities and women at the initial stages (high school to college and college to graduate school), along with training graduate student for scientific careers. Students develop scientific, social, and professional skills through hands-on training, exploration, and dissemination of research to the broader scientific community. The topics under study include materials synthesis and property measurements, fundamental training in materials synthesis and structure-property correlations, providing an important foundation for the development of thermal to electrical energy conversion and the advancement of multidisciplinary research aligned with technology. The research will be presented at national and international meetings and the findings published in peer-review journals. Additionally, the PI supports students through the ACS SEED program (high school), MURPPS (undergraduate), and AGEP (graduate) programs focused on increasing underrepresented groups in science on campus. The ChemWiki will be employed to enhance student learning through writing and critical evaluation.