纳米结构和能带工程提高Bi-Sb-Te合金的热电性能  

Nanostructuring and band engineering boosting thermoelectric performance of Bi-Sb-Te alloys via CsBr doping

作　　者：王宇 杨星 冯晶 葛振华 Yu Wang;Xing Yang;Jing Feng;Zhen-Hua Ge(Faculty of Materials Science and Engineering,Kunming University of Science and Technology,Kunming 650093,China)

机构地区：[1]Faculty of Materials Science and Engineering,Kunming University of Science and Technology,Kunming 650093,China

出　　处：《Science China Materials》2023年第10期3991-4000,共10页中国科学（材料科学（英文版）

基　　金：supported by the National Natural Science Foundation of China(52162029);Yunnan Provincial Natural Science Key Fund(202101AS070015);the National Key R&D Program of China(2022YFF0503804);the Outstanding Youth Fund of Yunnan Province(202201AV070005)。

摘　　要：碲化铋由于其优异的性能,已成为商业上广泛使用的热电材料.然而,通过熔化方法获得的p型Bi-Sb-Te热电材料的性能仍有进一步改进的空间.在这项工作中,CsBr化合物被用来提高Bi_(0.42)Sb_(1.58)Te_(3)(BST)材料的热电性能.采用熔化法和放电等离子体烧结相结合的方法制备了BST+x wt%CsBr(x=0,0.10,0.20,0.30)的块状材料.Cs和Br共掺杂可以显著提高BST合金的电导率,同时降低其热导率,使其在323 K下的最大ZT值为1.2.对于x=0.20的样品,在400 K以下具有1.1的平均ZT.密度泛函理论和透射电子显微镜分析表明,Cs掺杂有效地减小了带隙,增加了费米能级附近的态密度,并使能带变平缓,从而使电输运特性得到了明显增强(最大功率因子接近3500μW mK^(-2)).此外,Cs掺杂可以使得Sb从晶格中脱离出来并与晶格中的游离氧结合形成纳米级Sb_(2)O_(3),使其能够有效地散射中频声子并降低热导率,同时保持相对较高的塞贝克系数.这项研究提出了一种新的方法,可以仅单独通过CsBr掺杂来解决热电材料中电导率和热导率之间的矛盾.Bismuth telluride has become a widely commercially utilized thermoelectric material due to its exceptional properties.However,there remains space for further improvement in the properties of p-type Bi-Sb-Te thermoelectric materials obtained through the melting method.In this work,CsBr was employed to enhance the thermoelectric properties of Bi_(0.42)Sb_(1.58)Te_(3)(BST)materials.The bulk materials of BST+x wt%CsBr(x=0,0.10,0.20,0.30)were fabricated using a combination of melting method and spark plasma sintering.Cs and Br co-doping could significantly increase the electrical conductivity of BST alloy,while reducing thermal conductivity,resulting in a maximum figure of merit(ZT)value of 1.2 at 323 K and an average ZT value of 1.1 below 400 K for x=0.20 sample.Density functional theory and transmission electron microscopy analyses reveal that Cs doping effectively reduces the band gap,increases the density of states near the Fermi level,and flattens the energy band,resulting in the great enhancement of electrical transport properties(with a maximum power factor of approximately 3500μW m^(-1) K^(-2)).Furthermore,Cs doping causes Sb to dissociate from the lattice and combine with free oxygen to form nanoscale Sb_(2)O_(3),which efficiently scatters mid-frequency phonons and reduces thermal conductivity while maintaining a high Seebeck coefficient.This study presents a novel approach to resolving the trade-off between electrical and thermal conductivity in thermoelectric materials by solely utilizing CsBr doping.

关 键 词：p-type bismuth telluride electronic structure modification thermoelectric performance energy filtering effect 

分 类 号：TB34[一般工业技术—材料科学与工程]