碲化铋基（三维/一维）复合热电材料的结构调控与性能研究

In recent years, nanocomposite materials have received more and more interests in the field of thermoelectric(TE). However, how to choose the second phase and uniformly disperse the second phase into the matrix is most important and difficult as well. Based on our previous studies, we proposed a concept of nanostructured multi-oxide to be embedded into BiSbTe matrix, thus to optimize the thermal and electrical performance simutanously. It is defined as one kind of oxide containing at least two cations: one is relatively active to react with the matrix and tune the carrier concentration; the other is inert, which exists in the form of oxide with nanostructure to scatter phonons. In this project, three-dimension/ one-dimension heterogeneous TE nanocomposites will be prepared through simple processes, based on the composites of Bi2Te3/Attapulgite. We are going to uniformly disperse ATP nanorods into Bi2Te3 matrix by pressureless infiltration combined with rocking-melting and quenching. Through investigating the effect of process parameters on the microstructure and revealing the influence of the nanorods content, distribution and interfaces with the matrix on the TE properties, feasible schemes will be provided for the constituent optimization and the multi-dimension composition model for the TE materials. Based on the above studies, a significant improvement in TE performance will be achieved. Since the Bi2Te3-based alloys are the most excellent TE material around room temperature, this project will be of great significance to promote the practical applications, exploit other new TE materials and further improve the establishment of TE transport theory.

采用纳米复合改善热电性能是本领域的研究热点，其中第二相选取以及如何实现在基体中的有效分散是相关重点与难点。基于本课题组前期研究，我们归纳提炼出多元氧化物/碲化铋复合热电材料制备理念，以同时优化电热输运性能。本项目以碲化铋/凹凸棒为切入点，拟通过简单工艺路线制备三维/一维异质纳米复合热电材料，即通过无压渗透浸润结合摇摆熔炼和淬火急冷，巧妙实现一维凹凸棒（ATP）在三维碲化铋基体中的均匀分散。通过阐明制备工艺参数对材料显微结构的影响，揭示ATP纳米棒含量、分布、碲化铋/ATP相界面对载流子和声子输运的作用规律与机制，从而为热电材料组分优化设计以及多维度复合模型构建提供方案。碲化铋基合金是目前室温附近性能最佳的热电材料，本项目实施无论是对促进其实际应用，还是对开发其它体系热电材料均具有重要意义。

碲化铋材料是唯一实现了商业化应用的热电材料，广泛应用于室温附近的便携制冷和热电发电领域。然而，商用区熔碲化铋材料力学性能较差和热电转换效率偏低的问题日益凸显，限制了热电技术的进一步发展。本项目通过制备p型Bi0.48Sb1.52Te3复合材料并发展碲化铋烧结材料制备工艺，探究微观结构与力学和热电性能间的关联，从而凝练优化碲化铋综合性能的可行思路。研究发现复合材料中异质界面不仅能过滤低能载流子优化功率因子，还能降低热导率，有效提高热电性能。热变形、织构化热压等工艺能够促进碲化铋精细再生长，获得较高织构度保持良好电学性能，同时生成缺陷增强声子散射降低热导率，可以获得高达1.44的ZT值。本项目研究结果可为碲化铋材料的应用发展提供指导意义。