电荷与自旋协同调控BiCuSeO热电性能的实验研究

Thermoelectric materials can be utilized to convert thermal energy and electrical energy directly in a single thermoelectric generation system. The widely use of these materials have great importance in the relief of environment pollution and energy crisis. Recent experiment showed BiCuSeO has good thermoelectric performance, which originated from its ultra-low lattice thermal conductivity. The main restricting element is its low electric conductivity, but single increasing its electric conductivity would decrease its thermoelectric force sharply, which would not be an ideal way to optimize the thermoelectric performance. In this project, we will optimize the thermoelectric performance of BiCuSeO through the combining tunning of charge and spin degree of freedom, and systematically study the influence of structure, magnetic, electric and thermal transport properties of BiCuSeO through double doping. The magnetic ions doping in Cu site would enhance the spin entropy and then increase the thermoelectric force; and on this basis, the double doping in both Cu site and Bi site would increase the carrier concentration and so the electric conductivity. Meanwhile, the double doping would introduced more disorder, which would further decrease the thermal conductivity. Combining with theoretical calculation, we will explore the theoretical foundation of the influence of the thermoelectric performance through double doping.The project will help us further understand the BiCuSeO-based thermoelectric material and provide some guide to optimize thermoelectric performance for the similar system materials.

热电材料可以实现热能和电能的直接相互转化，该材料的应用为缓解环境污染及能源危机具有重要的意义。近期研究发现BiCuSeO由于其极低的晶格热导率而表现出较好的热电性能。制约其热电性能的主要因素是电导率较低，但单一地提高电导率往往会降低材料的热电势，使得优化效果并不理想。本项目拟通过自旋与电荷协同调控BiCuSeO的热电性能，系统研究双掺杂对材料的结构、磁、电以及热输运等性质的影响。通过对Cu位进行磁性离子掺杂，增加自旋熵以提高材料的热电势；并在此基础上进行Cu位、Bi位元素双掺杂的研究工作，提高体系载流子浓度从而提高电导率；同时由于双掺杂引入更多无序从而降低材料的热导率。结合理论计算，探索双掺杂影响BiCuSeO热电性能的理论依据，为理解双掺杂对材料热电性能影响的微观机制提供帮助。本项目的顺利实现将加深我们对BiCuSeO热电材料的认识，并为相似体系热电材料的优化积累实验数据和提供理论指导。

热电材料作为一种可以实现热能与电能之间直接相互转换的功能材料，受到了人们的广泛关注。BiCuSeO作为一种新型的层状结构热电材料表现出潜在的应用价值。本项目通过电荷与自旋协同调控的手段来优化BiCuSeO的热电性能，获得了一种在室温附近ZT值较高的BiCuSeO热电材料，并总结了磁性元素掺杂对该材料热电性能影响的实验规律，为相似体系热电材料的性能优化提供了参考。本项目具体开展以下研究内容：（1）探究了磁性元素掺杂对BiCuSeO热电性能的影响，获得了Co掺杂及Ru掺杂对BiCuSeO热电性能影响的实验规律。（2）探究了电荷与自旋协同作用，通过CoCa双掺杂获得了一个具有较高室温热电优值的BiCuSeO材料。（3）我们探究了其它CuSe基层状结构热电材料。合成了一系列具有潜在热电性能的Bi2LnO4Cu2Se2材料。