高效p型BiCuSeO基氧化物热电陶瓷的制备及其传输机理研究

R&D of thermoelectric conversion materials utilizing solar energy or waste heat, is an important component of national strategic development oriented to energy resources. The conversion efficiency is determined by the thermoelectric property of thermoelectric materials. In comparison with conventional thermoelectric alloies, novel thermoelectric oxides ceramics possess higher physical/chemical stability, exhibiting unique applicability due to its relatively higher thermoelectric property in middle/high temperature range. The atomic and electronic structure of oxides influences the thermoelectric property significantly. Henceforward, systematic and intricate studies on thermoelectric property and tuning mechanism of oxides is fundamentally important. Recent studies revealed that multielement chalcogenide copper-based oxides BiCuSeO, with a unique two dimensional layered structure, exhibited relative good thermoelectric property at high temperature after being doped optimally. However, there is lack of systmatic investigation of thermoelectric property of the compound either in and out of China, because of the complexity in structure and unique electronic transport channel. This project aims to systematically investigate and optimize the thermoelectric properties of BiSeCuO, by using solid-state reaction method, mechanically alloying, Spark Plasma Sintering(SPS) nanocrystallization techniques, and defect-tuning of charge-carrier-concentration, etc. The results achieved from this project will provide essential experimental evidence and theoretical guidelines for preparation techniques of the materials and understanding of its thermoelectric transport mechanism.

利用太阳能或废热的热电转换材料研发是面向国家能源战略发展的重要组成部分。热电转换效率取决于所用热电材料的热电性能。与传统合金热电材料相比，新型氧化物热电陶瓷具有更高的物理化学稳定性，以其较高的热电性能在中高温热电应用领域，呈现出独特的应用价值。氧化物的原子结构和电子结构对热电性能影响甚巨，因而，系统且细致地研究氧化物热电性能及其调控机理显得尤为重要。最近研究发现，多元硫系铜基氧化物BiCuSeO，具有独特的二维层状结构，掺杂优化后呈现出良好高温热电性能。然而，由于其结构复杂、奇特的电子输运通道，国内外尚无此类化合物热电性能的系统性研究。本课题拟采用固态烧结法、机械合金化、放电等离子烧结(SPS)纳米晶化结合热锻等工艺、及缺陷调控掺杂优化载流子浓度等方法,系统研究并优化BiSeCuO的热电性能。研究成果将为该材料的制备工艺和热电传输机制提供重要的实验证据和理论依据。

BiCuSeO基热电材料在近几年的研究发展中，已逐渐成熟的成为热电材料家族中的一员新生代，层状结构决定其较低的热传输特性（~0.4Wm-1K-1），缔造了它作为热电材料的优势。本课题通过传统固相结合放电等离子烧结工艺制备BiCuSeO基热电材料，研究表明在Bi位置低价态元素掺杂（Mg2+、Ca2+、Pb2+）和Cu缺陷在增加载流子浓度优化电学性能，在提高BiCuSeO基功率因子基础上提高材料热电性能；在Se位通过引入Te带隙调控调节载流子的迁移率来调控电性能，从而优化其热电性能；以及Bi位引入双元素（Ca2+、Pb2+）掺杂调控，大幅度提高其热电传输特性，相应ZT在~1.5；并在系列研究中进行相关理论研究。印证了BiCuSeO基材料是一种优异的热电半导体材料.