电负性客体填充的新型方钴矿材料合成和输运机制研究

The skutterudite-based inclusion compounds are one of the most promising thermoelectric materials in the intermediate temperature range. How to improve their thermoelectric performance and develop the large-scale preparation technology still remain challengeable so far. Based on our recently findings on electronegative guests (S, Cl etc.) filled CoSb3 skutterudites and previously achievements on electropositive metal atoms filled skutterudites, this project will study and clarify the influence of different filling guests and/or substitutional atoms on various properties of skutterudites, such as the crystal structure, electronic structure and phonon scattering mechanism, thus to reveal the combination law between electronegative guests and substitutional atoms, as well as the electrical and thermal transport characteristics. This project will explore and develop the controllable technology for the large-scale preparation of multiple-guests filled new skutterudites materials with low energy consumption, design and fabricate a series of new stable skutterudites based on the filling of electronegative guests, and realize the synergistic optimization of the electrical and thermal transport characteristics. This research provides a new strategy for developing high-performance bulk p-type and n-type skutterudite materials and their large-scale preparation.

方钴矿基包合物材料是最具应用前景的中温热电材料之一，其热电优值的提高和规模化可控制备是国际热电材料领域的挑战性难题。本项目基于申请者最新发现的以S、Cl等电负性原子为填充客体的方钴矿材料，结合传统电正性金属原子填充成果，系统研究并揭示不同客体组合填充及置换对方钴矿基材料显微结构、电子结构、客体-主体成键特性和热振动模式等的影响规律，阐明多元填充客体及置换原子的组合规律及其对电热输运行为的影响规律，探索并发展新型多元客体填充方钴矿材料的低能耗规模化可控制备方法和工艺，设计并制备基于电负性客体填充且稳定存在的系列新型方钴矿材料，实现基于多元客体填充方钴矿材料中电、热输运行为的协同调控，为大幅提高p型和n型方钴矿材料的热电优值和材料的规模化制备提供新的途径。

电负性客体填充方钴矿材料具有低能耗、规模化生产的优势和潜力。研究基于电负性客体填充的新型方钴矿基材料，探索电负性客体原子的填充条件和实验工艺，揭示电负性填充客体对方钴矿材料晶体结构、电子结构、电热输运的影响规律和作用机制，都是极具挑战而又十分重要的新课题，是实现方钴矿材料性能优化和规模化可控制备的重要基础。本项目结合理论计算和实验，设计并制备了多种电负性客体填充的方钴矿化合物，通过高温高压结合放电等离子烧结，获得了硫双位掺杂的p型方钴矿，掺杂和填充引入的晶格应变使Co4Sb12的能带平坦化，减小了价带顶和次价带间的能量差，增加了参与电输运的能谷数量，强化了材料的功率因子。硫双位掺杂样品的低温比热和拉曼谱图表明晶格应变引起了非谐和低频振动，导致材料的晶格热导率显著降低；本项目发展了阶段压力一步快速制备电负性客体填充方钴矿的方法，获得的材料富含晶内孔隙，研究并揭示了压力、温度、组分的改变对填充方钴矿电热输运性能和力学性能的影响，该方法制备的硫填充碲取代样品的性能明显增加，高温ZT值超过1.6，300-825K温度区间的平均ZT值达到0.96。本项目发展的阶段压力制备含低熔点材料的方法对研究多孔热电材料及其他功能材料具有重要借鉴意义。