多元层状热电材料中基于亚层结构的缺陷结构设计与性能优化研究

Multiple layered-compounds, like BiCuSeO, usually have alternating stacked sublayer structures. Among different sublayer channels, the electrical and thermal transport behaviors are usually different from each other, and have their own characteristics, which endow them with potential “phonon glass—electron crystal” or even “phonon liquid—electron crystal” character, and make them ideal materials for thermoelectric application. This project will carry out a comprehensive study of the thermoelectric properties of these special multiple layered thermoelectric compounds. First, specific crystal defects such as vacancy, substitution atom will be introduced into the corresponding sublayers through non-stoichiometry, elemental doping and other strategies, which can help to modulate the electronic band structure and phonon transport behavior, leading to optimized electrical/thermal transport properties and the final thermoelectric performance. On the other hand, by advantages of fine characterization of the defect structure, the associated local atomic structure, as well as the electronic band and phonon structures in these thermoelectric systems, this project will present a deep study of the basic rules in defect modulation of electrical and thermal transport performance, summarize different optimization strategies, and try to explore the “multiple doping—multiple strategies” synergistic optimization concept. Through the implementation of this project, new theories regarding to defect modulation are hoped to be established, which will help to discover a batch of high-performance layered thermoelectric materials, and provide theoretical guidance and material support for the development and commercial application of thermoelectric technology.

在BiCuSeO等具有亚层结构组成特征的多元层状热电化合物中，其不同亚层结构通道中的电热输运行为具有一定的差异性，使其潜在满足“声子玻璃（或液体）—电子晶体”的输运特性，是一类较为理想的热电材料。本项目拟选取这类特殊层状热电材料为研究对象，通过非化学计量比、元素掺杂等方式向目标体系的不同亚层中针对性地引入空位、置换原子等缺陷，调节其微观的电子能带结构和声子传输特性进而实现其宏观电热输运性能的调控和最终热电性能的优化。另一方面，通过对缺陷结构及伴生的局域晶格结构、能带结构、声子结构的精细表征与模拟，本项目将深入研究热电转换过程中陷调控电、热输运性能的基本规律，总结基于缺陷调控的不同优化策略，并尝试探索“多缺陷掺杂—多策略协同作用”的实验策略。通过本项目的实施，期望发展热电材料缺陷调控的相关理论，发掘一批基于缺陷调控的高效层状热电转换材料，为热电科技的发展和产业化应用提供理论指导和材料支持！

在BiCuSeO等具有亚层结构组成特征的多元层状热电化合物中，其不同亚层结构通道中的电、热输运行为具有一定的差异性，使其潜在满足“电子晶体—声子玻璃（或液体）”的输运特性，是一类较为理想的热电材料。本项目以该类材料为研究对象，基于亚层结构的缺陷态构筑调控和优化相关体系的电、热输运性能。采用正电子湮没技术和角分辨光电子能谱技术对部分样品的缺陷形态和电子能带进行深入表征与分析，探讨了缺陷调控的微观机制；同时，结合不同缺陷的调控规律，发展了“多缺陷掺杂—多策略协同作用”的实验思想和 “多维度缺陷工程”协同调控的实验策略，并通过多种缺陷共掺杂实现了BiCuSeO等多元层状体系电、热输运性能的协同优化与热电性能的显著提升。例如，通过La-Ag异层双掺杂触发BiCuSeO潜在的能带收敛，提高载流子浓度并保持较高的载流子迁移率和Seebeck系数，使最终ZT值提升约70%。提出层间电荷充分释放策略，在BiCuSeO中通过结合Bi-Cu双空位和Pb/Bi施主掺杂同时提供层间电荷转移通道和充足的载流子，从而显著提高体系电导率，激活多重简并价带，实现1.4的高ZT值。实际执行过程中，我们还将这种多缺陷调控的思路拓展到其他非层状体系，基于“donor–acceptor”共掺杂的电荷补偿效应实现了AgSbTe2体系热电性能的优化，基于阳离子空位缺陷调控在Cu2ZnSnSe4体系形成空位缺陷簇并引发局域晶格无序，实现了该体系热电ZT值的2倍的提升。这些研究丰富了“多缺陷掺杂—多策略协同作用”概念的应用空间，并为缺陷调控功能固体中电、热输运行为的研究提供了更深层次的理解。项目执行期间，研究团队成员参加国内热电领域学术会议2次，作口头报告1次。基于项目资助培养博士后1名，博士生3名，硕士生1名，发表学术论文10篇。