p型Mg2Si1-xSnx材料的熔体旋甩制备及共振能级对热电性能优化的研究

Due to the fact that ZT value of the P-type Mg2Si based thermoelectric materials is far below n-type materials, and for real thermoelectric devices application, both n-type and p-type material have to be provided，in this project, we rapidly fabricate nanostructured p-type Mg2Si1-xSnx via melt spinning technique followed by high energy ball milling and spark plasma sintering (SPS), where the amount of Mg is accurately controlled. By carefully manipulating dopants and the doping concentration, the resonant state and the distortion of density of state in p-type Mg2Si1-xSnx will be achieved. Furthermore, we will explore the dependence of the morphology of P-type Mg2Si1-xSnx including phase, size and distribution on fabrication parameters. The formation mechanism of this resonant state in p-type Mg2Si1-xSnx will be clarified and the relationship between resonant state and the thermoelectric transport properties(especially the Seebeck coefficient) will be demonstrated. This project is expected to achieve the controlled formation of resonate state and synergistic enhancement mechanisms of the thermoelectric performance in p-type Mg2Si1-xSnx materials, thus largely raise ZT value to 1.2. This work is a good example of how to obtain the Mg2Si1-xSnx material with proper amount of Mg, nanostructure and resonant state. The successful accomplishment of this project will boost the development of full Mg2Si based thermoelectric devices.

Mg2Si基化合物对中温热电材料的发展具有重要意义。针对目前p型Mg2Si基材料热电性能明显劣于n型材料的问题，本项目以p型Mg2Si1-xSnx体系为研究对象，采用有保护气氛的熔体旋甩技术，结合球磨和放电等离子烧结（SPS)技术，快速制备结构纳米化、Mg含量精确控制及单相p型Mg2Si1-xSnx化合物，系统研究工艺参数对产物微结构的影响规律。通过合理掺杂在p型Mg2Si1-xSnx材料中形成共振能级，探索掺杂元素种类与数量对载流子浓度、费米面位置的调控机制，阐明共振能级的形成机理，揭示共振能级对材料电声输运特性（特别是对Seebeck系数）的影响规律。项目预期将在p型Mg2Si1-xSnx化合物中实现现有调制电热输运特性方法的“一体化”协同控制，使该体系 ZT值高达1.2，为研制全Mg2Si1-xSnx基热电器件提供理论基础和实验依据。

本项目以p型Mg2Si1-xSnx基热电材料为研究对象，采用自制熔体旋甩设备结合放电等离子烧结技术，快速制备了结构纳米化、成分均匀、Mg含量精确控制的单相p型Mg2Si1-xSnx基化合物；系统研究了掺杂元素种类与含量对p型Mg2Si1-xSnx基体系热电材料能带结构及载流子浓度调控的影响；探索了材料Seebeck系数、电导率与掺杂元素种类、含量和取代位置的关联规律；利用现代测试技术探究了最终产物的物相、形貌等参数，揭示了熔体旋甩和SPS工艺参数与热电参数之间的相互影响规律及机制。最终实现了材料的Seebeck系数、电导率、热导率三个参数的解耦，大幅度提高了p型Mg2Si1-xSnx基材料体系热电性能。为研制全Mg2Si1-xSnx基热电器件提出了有效的理论基础和实验依据。同时，为其它材料体系的热电性能优化提供了新的思路和途径。