硫化铋基热电材料的晶界调控与输运性质研究

Bi2S3 with abundant, cheap and low-toxic elements as a potential thermoelectric material still has some problems to be figured out，such as low electrical conductivity and low ZT value. Nowadays, the thermoelectric property of Bi2S3 could be improved by process parameter controlling and elements doping, but it is still too low to be applied in business. It becomes very important to improve the electrical conductivity in Bi2S3 system. In this project, we focused on the Bi2S3 based materials. The Bi2S3 based core-shell structure powders and heterogeneous structure will be prepared by ball milling and hydrothermal synthesis. The bulk Bi2S3 based materials will be fabricated by spark plasma sintering technique. The core-shell structure and heterogeneous structure were maintained in matrix and become grain boundary phase. The mechanism of effect of the species, quantities and distributions on the thermoelectric properties of polycrystal Bi2S3 will be revealed. The mechanism of effect of the grain boundaries inclusions on electrical transport properties of Bi2S3 will be illustrated. The physical essence of grain boundary blocking modulation doping was discussed. All of above offer references for application of grain boundary engineering in other thermoelectric system.

原料来源丰富、廉价、低毒的多晶硫化铋作为一热电材料目前还存在电导率低和热电性能差等问题。目前，工艺优化与元素掺杂能使硫化铋的热电性能得到提升，但距离商业化应用仍有差距。因此，深入研究硫化铋体系的电子输运机制，提高硫化铋多晶材料的电导率显得至关重要。本项目以硫化铋为研究对象，以多种制备方法制备硫化铋纳米粉体，然后再通过水热工艺处理，制备硫化铋核壳结构和异质结结构的纳米粉体，通过放电等离子烧结技术制备块体硫化铋材料，使得核壳结构或者异质结结构在块体材料中得到保留，形成晶界相。探索晶界相种类、数量和分布形态对硫化铋多晶块体材料电传输性能的影响机制；结合第一性原理计算阐明晶界夹杂物对硫化铋电、热输运性质的影响机制；揭示晶界阻隔增强调制掺杂效果的物理本质；为晶界工程在其它热电体系中运用提供借鉴依据。

硫化铋基热电材料原料来源丰富、廉价、低毒是一种有前景的热电材料，但是其作为热电材料最突出的问题是电导率低，热电性能不佳。本项目在前期工艺调整的基础上，提出了晶界调控策略，采用多种方法，包括球磨法，固相熔融法和水热法合成了硫化铋粉体，并通过晶界净化，引入晶界阻隔层，引入晶界高导电第二相以及多纳米析出物等方法，实现了硫化铋热电性能的大幅提升。水热法合成的Cl掺杂的硫化铋纳米棒与高导电第二相FeCoNi复合材料的ZT值在573K达到1，是硫化铋体系第一个超过1的ZT值，标志着硫化铋成为一种具有商业应用前景的高性能热电材料。并通过第一性原理计算、透射电镜精细微观结构表征等手段，揭示了硫化铋热电材料性能提升的物理机制和微观机制。提出了，晶界还原净化，电镀法引入晶界高导电层，晶界高导电夹杂相，具有阻隔层的调制掺杂，溶液法卤族酸掺杂等热电材料的优化策略，为其他热电材料体系性能的提升提供借鉴。本项目执行期间2018年1月至2021年12月，共计发表SCI 论文25篇，其中包括Advanced Functional Materials，Nano energy，Chemical Engineering Journal，Materials Today Physics等高水平期刊6篇，申请发明专利6项，获授权2项，超额完成了项目任务。