BiTe系低维纳米热电材料的去耦合性能调控

热电（TE）材料是实现热能和电能直接相互转化的一种清洁能源材料，应用于工业余热发电和温差制冷。它具有性能可靠、移动灵活、无噪音和污染等优点而备受关注。然而其热电转换效率低，且电子和声子的耦合关系制约着热电优值的提高。目前商业化热电材料是BiTe基固溶体，然而成本高，ZT接近1，转化效率不到10%，如何采用经济的方法合成性能更加优良的材料是进一步研究的方向。本项目拟通过湿化学方法合成10~20纳米的二元BiTe基纳米六角片状材料，同时掺杂得到N型和P型三元化合物。由于其具有相似的晶格对称性及键合环境，可以构架一种通用的反应环境来合成多元体系的纳米片状化合物使得多元材料的合成成为可能。掺杂的成分和比例可以优化载流子的浓度和迁移率，调控电性能；纳米片状的晶粒形貌对声子具有很强的散射作用，显著降低热导率。通过解除电声的耦合关系调控热电性能可以得到低成本、高ZT的室温BiTe基热电材料。

Thermoelectric (TE) materials, which can realize the conversion between electricity and heat for global green energy resources, has been applied in powering generation from industrial waste heat and thermoelectric cooling. Due to the advantages of reliable performance、flexible mobility、none-noise and pollution-free, it has attracted widespread attention. Nevertheless, the low thermoelectric efficiency and conflicting couple relationship between the electrical and thermal property restricted the development of TE materials. At present BiTe-based solid solution is the state-of-the-art commercial thermoelectric material, nevertheless, it exists the problem of high cost、ZT approaching unity and the low conversion efficiency (less than 10%). Developing low cost methods to fabricate high performance thermoelectric materials are required to further study. The objective of the research project is to synthesize two dimensional BiTe based nanoplatelets with thickness of 10 ~ 20 nm and fabricate N type or P type ternary compounds via doping antimony or selenium to gain N type or P type nanocomposites. Owing to the similar lattice symmetry and bonding condition between atoms, poly-compounds with nano-sheet structures can be obtained through a universal thermodynamic environment. The doping composition and ratio modify electrical property via optimizing the carrier concentration and mobility, meanwhile, the nanoplatelet structures significantly reduce thermal conductivity by strongly scattering phonons. Therefore, room temperature BiTe based thermoelectric materials with low cost and high ZT value can be developed through breaking trade-off between electrical and thermal property.