BiSbTe纳米晶膜可控生长及热电性质研究

Thermoelectric materials are a class of advanced energy materials which have drawn great attention due to their ability to realize the direct convertion between thermal and electrical energy. Low-dimensional nanostructures have present great potential in the fields of energy harvest and storage. It is of importance for both fields of science and technology to exploit novel thermoelectric materials and devices with high performance utilizing the unique electric transport and thermal properties of nanostructures. BiSbTe alloys possess good room-temperature thermoelectric property which can be greatly improved in their low-dimensional nanostructures. The project aims at the experimental study on the controlled growth and thermoelectric property of BiSbTe nanocrystal films. The closed-space-sublimation technique is proposed to achieve the controlled growth of BiSbTe nanocrystal films and the related mechanisms will be studied so that the microstructural parameters, including morphologies, sizes, compositions and orientations, can be tuned. The dependence of the thermoelectric property of BiSbTe nanocrystal films on their microstructure will be systematically examined to reveal the control mechanism of thermoelectric property using structural, compositional, electrical, thermal and optical charactrizations. The controlled growth technique for BiSbTe nanocrystal films with high thermoelectric performance will be developed, which would lay the research foundation of their future applications.

热电材料能够将热能与电能直接相互转化，是一类受到广泛关注的先进能源材料。低维纳米结构在能源获取和存储领域已经显示出巨大的应用潜力，利用纳米结构独特的电输运和热学性质，发展新型高效热电材料和器件，具有重要的科学和技术价值。BiSbTe合金具有良好的室温热电性能，通过低维纳米结构化，其热电性能可以得到很大的提高。本项目拟开展BiSbTe纳米晶膜的可控生长与热电性质实验研究，采用近距离升华方法生长BiSbTe纳米晶膜，研究其生长机制，对膜的晶粒形貌、尺寸、组份、取向等微结构参数进行调控，利用结构、组份、电学、热学、光学等多种表征手段，系统研究纳米晶膜的 微结构对其热电性质的影响，分析热电性质调控机制，掌握高性能BiSbTe纳米晶膜的可控生长技术， 为其应用打下研究基础。

Bi2Te3基化合物是目前室温附近最主流的热电材料，其纳米薄膜有望获得更好的热电性能，在小型高性能热电器件领域有重要应用潜力。本项目针对(BiSb)-(TeSe)系列化合物纳米晶膜的可控生长与热电性质开展了系统深入研究，进行了大量实验探索，包括：实现了组分和微结构可控的Bi2-xSbxTe3纳米柱阵列薄膜生长，研究了薄膜形貌结构和电输运性能,在 Bi0.5Sb1.5Te3纳米柱阵列薄膜中获得了最优的电学性能，475 K下最大功率因子PF为3.83 μWcm-1·K-2; 首次制备了高度取向的Bi4Te3纳米柱阵列薄膜，对薄膜形貌取向有效调控，研究了微结构对薄膜的电学性质影响，发现高结晶度和有序取向有利于薄膜的电输运;制备出了形貌可控的Bi2Se3纳米晶薄膜，结构和电输运性质分析发现纳米柱薄膜的电学性能明显优于片状形貌薄膜；首次制备出Bi2Te3/Sb2Te3新型纳米柱阵列异质结膜，实现了结构的有效调控；采用气相升华输运沉积，在无催化剂辅助条件下，实现了Bi2Se3单晶纳米带的生长，分析了材料的生长机制；制备了Bi2(Te1-xSex)3三元系单晶纳米片,通过掺杂显著降低了材料的热导，最小的热导值约0.42 Wm-1 K-1 （413K），从而有效提升了材料的热电性能；调控Bi2Se3纳米材料的生长行为并进行Sb掺杂，制备出纳米片自组装的n型(BiSb)2Se3纳米花。材料的电输运性能得到了优化，同时热导大幅度降低，总体热电性能得到显著提高,在温度为523 K获得最优ZT～0.55,文献结果提升了近2倍，与块体相比提升了近13倍.以上研究成果发展了(BiSb)-(SeTe)体系的低维材料可控制备技术，获得了新型材料，了解了材料的生长机制、热电物性调控机理和提升途径，深化了对Ⅴ-Ⅵ化合物材料的构效关系认识；所获得的专利技术，在新型薄膜热电器件领域具有潜在应用价值。