方钴矿热电输运行为的填充与位错阵列协同调控机理研究

Skutterudites thermoelectric materials with intrinsic lattice voids have high carrier mobility, relatively high electrical conductivity and Seebeck coefficient, but its high lattice thermal conductivity results in low ZT. Filling guest atoms into the voids has been demonstrated to be an effective approach to suppress lattice thermal conductivity, optimize carrier concentration and enhance thermoelectric performance. However, the lattice thermal conductivity is still relatively high. This project puts forward a new strategy that adopting liquid phase compaction method to fabricate dense dislocation arrays in filled skutterudites could simultaneously optimize the electrical and thermal transport behavior and finally realize enhancing thermoelectric performance. The influence of liquid phase compaction technique, excess Sb content as well as filler type, concentration and their combination on phase components, composition, grain size, microstructure and thermoelectric properties of CoSb3 materials is investigated to achieve the control of filling content and dislocation arrays density. The physical mechanism between filling behavior and dislocation arrays to simultaneously control the electrical and thermal transport behavior of skutterudites is clarified. The inherent relationship of liquid phase compaction technique, excess Sb content, filling behavior, dislocation arrays and thermoelectric performance is finally established. The liquid phase compaction technique and the principle on composition design for high thermoelectric performance skutterudites will be developed. This study could lay the foundation of design, fabrication as well as application for skutterudites thermoelectric materials.

本征孔洞方钴矿热电材料具有高迁移率、较高的电导率和塞贝克系数，但高晶格热导率导致ZT值低。孔洞处填充杂质原子被证实是一种降低晶格热导率且优化载流子浓度提高热电性能的有效方式，但晶格热导率仍较高。本项目提出在方钴矿CoSb3填充的基础上采用液相压实构建位错阵列，协同调控热电输运行为，实现提高热电性能的新思路。重点研究液相压实工艺、额外Sb含量和填充元素种类、含量及组合对方钴矿CoSb3相组成、成分、晶粒尺寸、微观组织结构和热电性能的影响规律，实现填充量和位错阵列浓度可控，查明填充与位错阵列协同调控方钴矿热电输运行为的物理本质，建立液相压实工艺-额外Sb含量-填充-位错阵列-热电性能之间的内在联系，优化出高性能方钴矿的液相压实工艺和成分设计准则，为方钴矿热电材料的设计、制备及应用奠定基础。

采用额外加入Sb结合熔体旋甩和热压烧结的方法实现n型Yb填充Co4Sb12合金和p型Ce填充Co4Sb12合金的液相压实制备，通过电子显微学分析明确了液相压实产生的高密度位错阵列构成小角晶界，从实验上证实了液相压实构建的位错阵列过滤低能载流子，提高Seebeck系数和功率因子，增强声子散射，降低晶格热导率，提高ZT值的结论，采用液相压实工艺通过调整Yb含量获得了ZT值为1.49，比热压烧结合金提高约28%，同时当Ce填充量为0.78时，p型填充方钴矿合金的ZT达1.1@723 K，为利用中温余热发电提供了坚实的研究基础。发表标注基金号SCI 收录论文37篇，其中第一标注19篇；培养了博士生14名，其中已毕业5名；硕士生14名，其中已毕业10名。