籽晶-区熔定向凝固Bi-Te-In-Se(...)合金多尺度结构调控与热电性能

A new method of seeding & zone-melting directional solidification is used to prepare the Bi-Te-In-Se(…) bulk materials with high thermoelectric performance by the enhancements of chemical homogeneity, preferentially orientated growth, inherently nano-phase precipitation and highly doping crystal lattice. In micron scale, the elemental distributions, microstructural evolution and competition, selection and inheritance of growth orientations are investigated during the liquid-solid transformation. The chemical composition and growth orientations of Bi2Te3 bulk crystals could be precisely controlled based on the above information. In nano scale, the nucleation and growth dynamics of In2Te3 precipitation from saturated Bi2Te3 crystals during solid-state transformation are investigated. The morphology, characteristic scale, volume fraction and distribution of In2Te3 thus could be controlled appropriately. In atomic scale, the filling of Se in Bi2Te3 crystals and its induced point defects are investigated after the liquid-solid and solid-state transformations. This is further directed to adjust the carrier density and the structural defects. Based on the structural control in all relevant length scales, a quantitative relation between compositions, crystal orientations, crystal defects and thermoelectric performance will be built. This work provides a new route to prepare Bi-Te based materials with high performance by directional solidification, which is also important to develop high efficiency thermoelectric devices at room temperature.

本项目拟采用籽晶-区熔定向凝固技术制备成分均匀、晶体取向择优、自生纳米相及晶格杂化的高热电性能块体Bi-Te-In-Se(…)材料。在微米尺度，通过揭示液固相变过程组元分凝、相和组织形成与演化以及晶体取向竞争、选择与遗传规律，实现块体Bi2Te3晶体成分与晶体取向的调控。在纳米尺度，通过揭示固固相变过程第二相形核与生长动力学，实现过饱和Bi2Te3晶体沉淀析出In2Te3相形态、尺寸、含量及分布的调控。在原子尺度，通过揭示液固和固固相变后掺杂元素Se等在Bi2Te3晶体内的填充及所引起点缺陷的结构特性，实现对载流子浓度及缺陷结构调控。最终，基于多尺度结构调控，建立成分、晶体取向、晶体缺陷与合金电热输运性能的定量关系。本项目研究既针对室温域热电制冷及温差发电应用的迫切需求，亦可为先进定向凝固技术制备高性能Bi-Te系热电材料提供新思路和理论基础。

本项目拟采用籽晶-区熔定向凝固技术制备成分均匀、晶体取向择优、自生纳米相和晶格杂化的高热电性能块体Bi-Te-In-(Se…)材料。在微米尺度，通过揭示液固相变过程组元分凝、相和组织形成与演化以及晶体取向竞争、选择与遗传规律，实现块体Bi2Te3晶体成分与晶体取向的调控。在纳米尺度，通过揭示固固相变过程第二相形核与生长动力学，实现过饱和Bi2Te3晶体沉淀析出In2Te3相形态、尺寸、含量及分布的调控。在原子尺度，通过揭示液固和固固相变后掺杂元素Se等在Bi2Te3晶体内的填充及所引起点缺陷的结构特性，实现对载流子浓度及点缺陷结构调控。基于多尺度结构调控，最终确立成分、取向、晶体缺陷与合金电热输运性能的定量关系。本项目研究既针对室温域热电制冷及温差发电应用的迫切需求，亦可为先进定向凝固技术制备高性能Bi-Te系热电材料提供新思路和理论基础。