BiSe单晶及其Sb掺杂单晶的制备和热电输运性质

Preparation and thermoelectric transport properties of BiSe and Sb-doped BiSe single crystals

在具有低晶格热导的单晶材料中探索高热电性能成为热电材料一个重要的新研究方向.Bi Se作为(BiSe)(Bi)系列超晶格化合物中的一员,其晶体结构中Bi双层的存在使其具有极低的本征热导率,同时得益于其化学组分无毒、环境友好的特点,成为一种新出现的很有潜力的热电材料.Bi Se特殊的层状结构使其热电输运特性具有显著的各向异性.本文采用布里奇曼法制备了大尺寸Bi Se单晶,对样品各向异性的热电输运性能进行了对比研究,结果显示样品在面内方向具有更高的电导率和热导率,而较低的塞贝克系数使得该方向最终的ZT值低于层间方向,两方向ZT最大值分别为0.11(573 K)和0.16(623 K).与Bi Se多晶样品相比,单晶样品表现出较低的电输运性能,可归因于两者散射系数的差异.通过Sb掺杂对Bi Se单晶样品的载流子浓度进行调控,有效提升了样品的塞贝克系数,优化电输运性能.同时Sb掺杂能够引起晶格畸变,降低样品的晶格热导率.最终样品的热电优值提升了约1倍,在层间方向BiSbSe样品中ZT值达到0.34(573 K),面内方向则提升至0.20(573 K).

Exploring high thermoelectric performance in single crystal materials with intrinsic low lattice thermal conductivity has become an important field for thermoelectric research. Bi Se, as a member of(BiSe)(Bi)series superlattice compounds, has a very low intrinsic thermal conductivity due to the existence of Bibilayer in its layered crystal structure. Moreover, it is a new and promising thermoelectric material due to the non-toxic and environmentally friendly chemical compositions. The special layered structure of Bi Se makes its thermoelectric transport properties significantly anisotropic. In this paper, Bi Se single crystal was prepared by Bridgman method, and its anisotropic thermoelectric transport properties were investigated. The results show that the sample has higher conductivity and thermal conductivity in the in-plane direction, while the lower Seebeck coefficient makes the thermoelectric figure of merit ZT value in this direction lower than that in the interlamellar direction. The maximum values of ZT in the two directions are 0.11(573 K)and 0.16(623 K), respectively. Compared with polycrystalline Bi Se, the single crystal sample exhibits lower electric transport performance, which can be attributed to the difference of scattering coefficient. The carrier concentration of Bi Se single crystal is regulated by Sb doping, which effectively improves the Seebeck coefficient of the samples and optimizes the electrical transport performance. In the meanwhile, Sb doping can produce lattice distortion and reduce the lattice thermal conductivity. The final ZT value of BiSbSe single crystal increases by about 1 fold, reaching 0.34(573 K) in the interlamellar direction and 0.20(573 K) in the in-plane direction.