基于亚晶格工程的热电化合物设计和性能调控研究

The exploration of thermoelectric materials goes gradually from simple elementary substances and binary compounds into complex compounds with multi-components, multiple chemical bonds, and coexistence of long-range order and local structure. It is essential to break through traditional doping and modulating methods and develop new methods based on sub-lattice engineering, which can satisfy the demand for novel thermoelectric compounds design and performance prediction, precise description and quantitative characterization of the sub-lattice structure feature, as well as mechanism understanding of the structure-property relationship. This project is focused on the investigation of part-crystalline compounds and layered structure compounds with typical sub-lattice structure. The structure feature of sub-lattice and its effect on electrical and thermal transport properties will be systematically studied. The band engineering based on sub-lattice and the method to describe thermal conductivity of the sub-lattice with obvious structural fluctuation will be developed. Focused on several typical thermoelectric compounds, we will determine the element distribution, chemical bond strength, electronic fine structure, and understand their correlation with the electrical and thermal transport properties. The substantial connection between the structure and property of the sub-lattice will be revealed. By using the difference in structure and physical property of different sub-lattices, the relatively independent modulation on the electrical and thermal transport properties will be realized. This project aims to construct general and instructive sub-lattice engineering concept and design model, which can be used to design novel thermoelectric compounds and optimize their thermoelectric performance. Based on this research work, we also aim to find several new thermoelectric compounds and significantly improve their thermoelectric properties.

热电材料探索逐渐由一元/二元简单化合物发展到多元组分、多元化学键、以及长程-局域特征结构共存的复杂化合物，亟需发展突破传统的掺杂调控而进入具有“亚晶格工程”特征的结构性能调控手段，在化合物设计与性能预测、亚晶格结构精确描述与定量表征、结构-性能关系的微观机制理解等方面提出新要求。本项目拟以具有典型亚晶格特征的半晶态化合物和层状结构化合物为重点，系统研究亚晶格结构特征及其对电热输运性能的影响机制，发展导电亚晶格中的能带工程，以及描述亚晶格具有结构涨落的热导方法；围绕几种典型热电化合物，表征并理解亚晶格中的元素分布、化学键强弱、精细电子结构及其与电热输运性能关系，揭示亚晶格结构-性能间的内在联系；利用不同亚晶格在结构和物性上的差异性，实现电热输运的相对独立调控。本项目将建立具有普适性和指导意义的新型热电化合物结构与性能调控的亚晶格工程思想及设计模型，发现几种新型热电化合物，显著提升其热电性能。

本项目围绕具有典型亚晶格特征的半晶态化合物和层状结构化合物展开研究，通过第一性原理计算、微结构精细表征和电热输运性能测量等手段，系统研究典型半晶态化合物和层状结构化合物的亚晶格结构特征及其对电热输运性能的影响机制。对具有亚晶格特征的热电材料体系进行第一性原理高通量计算和性能设计，理论预测并实验验证了一类新型高性能类金刚石热电材料。通过亚晶格系统中间隙原子的系统掺杂效应，在PbX-Cu2X系统中通过间隙Cu原子的动态掺杂效应，既提升了整个温度范围内的功率因子实现宽温域热电性能优化。通过在half-Heusler的4d空位填充间隙原子，实现half-Heusler与full-Heusler之间的成分间隔，并获得具有新奇物理性能的类half-Heusler结构材料。通过微结构精细表征技术，对具有层状亚晶格结构的SnSe进行分析，发现层状亚晶格间存在大量间隙原子和空位，获得具有极低热导率的热电材料。综上，通过高通量计算及表征手段，理解了亚晶格中的元素分布、化学键强弱、精细电子结构与其电热输运性能的关系，揭示了晶格结构-性能间的关系，并获得了几类新型具有亚晶格特征的高性能热电材料。项目执行以来，共发表相关论文近100篇，包括Science，Nature. Commun，Adv. Mater，J. Am. Chem. Soc，Adv. Funct. Mater，Energy. Environ. Sci.等。相关专利5项，培养研究生29名。