高性能N型BiCuSeO热电材料研究

Thermoelectric materials have attracted ever-increasing attention in the new energy and technology field. The trend of exploring high-performance thermoelectric materials will be focused on the issues of earth-abundant, environmental-friendly and thermal stability, etc. BiCuSeO oxyselenides have been extensively studied since it was reported as very promising thermoelectric material in 2010. The maximum ZT value of BiCuSeO system was significantly improved from 0.76 to 1.5 in the past several years, which can be comparable to some typically conventional thermoelectric materials. However, to date, all the BiCuSeO studies have reported are p-type materials. To construct a high performance thermoelectric device, both performance-matched n-type and p-type materials are required, this project aims to develop high-performance n-type BiCuSeO that could well match its p-type counterpart. The designing strategy for developing high performance n-type BiCuSeO can be described below as several rational successive steps. Firstly, filling p-type Cu and Bi vacancies and then electron-doping will be carried out to optimize electrical transport of n-type BiCuSeO matrix. Secondly, the approaches of modulation doping and microstructures texturing are proposed to further enhance the carrier mobility and electrical conductivity. Thirdly, Seebeck coefficients at room temperature and high temperature are proposed to be improved through applying distortion of the electronic density of states and valence bands convergence, respectively. At last, the high-performance n-type BiCuSeO would be expected to achieve.

热电材料在新能源技术领域具有广泛和重要的应用。综合元素的储量、环境友好和温度稳定性等因素考虑，寻找低成本、环境友好、高性能的新型热电材料将成为热点研究方向之一。自2010年首次报道BiCuSeO具有热电性能以来，该材料受到热电领域广泛关注，目前可以达到1.5的ZT值可与传统热电材料相媲美。然而目前报道的所有的BiCuSeO材料均为p型，为要实现高的热电转化效率需要性能匹配的n型材料，但目前对于n型BiCuSeO体系的研究工作尚属空白。本项目的研究目标是制备与p型BiCuSeO性能相匹配的n型BiCuSeO热电材料。项目的研究思路是首先补偿p型Cu和Bi空位再进行电子掺杂，获得性能最佳的n型BiCuSeO基体材料；进一步采取调制掺杂、择优取向织构制备、元素固溶和态密度共振等手段提高材料的性能优值ZT，最终获得性能优异的n型BiCuSeO块体热电材料。

热电材料在新能源技术领域具有广泛和重要的应用。综合元素的储量、环境友好和温度稳定性等因素考虑，寻找低成本、环境友好、高性能的新型热电材料将成为热点研究方向之一。自2010年首次报道BiCuSeO具有热电性能以来，该材料受到热电领域广泛关注，目前可以达到1.5的ZT值可与传统热电材料相媲美。然而目前报道的所有的BiCuSeO材料均为p型，为要实现高的热电转化效率需要性能匹配的n型材料，但目前对于n型BiCuSeO体系的研究工作尚属空白。本项目的研究目标是制备与p型BiCuSeO性能相匹配的n型BiCuSeO热电材料。本项目主要取得如下进展：1）通过空位补偿成功合成了具有n型半导体特性的BiCuSeO样品；2）通过复合高电导率的Ag单质，极大的提高了n型BiCuSeO体系的电导率；3） 通过卤族元素的掺杂，可在BiCuSeO材料中实现了稳定的n型BiCuSeO化合物；4）通过两种化合物BiCuSeO和Bi2O2Se复合，制备了一种n型Bi6Cu2Se4O6氧化物热电材料；5）通过引入过渡金属元素（Ti，Zr，Ce），显著提高了n型Bi6Cu2Se4O6的电子载流子浓度并改善了电传输性能，最终873 K时在Bi5.9Zr0.1Cu2Se3.6Cl0.4O6中最高ZT值达到~0.16。该项目研究表明，以n型BiCuSeO体系为研究对象，可以获得性能较佳的n型氧化物热电材料。本项目共发表了22篇研究成果，包括4篇Science。