Pnma型IV-VI族化合物单晶的热电性能及其各向异性的理论研究

项目名称： Pnma型IV-VI族化合物单晶的热电性能及其各向异性的理论研究

项目编号： No.11504239

项目类型： 青年科学基金项目

立项/批准年度： 2016

项目学科： 数理科学和化学

项目作者： 李煜

作者单位： 深圳大学

项目金额： 20万元

中文摘要： 2014年赵立东等人发现SnSe单晶（Pnma）b轴方向ZT值可达2.6±0.3，是迄今效率最高的热电材料。与SnSe具有相同层状结构的化学近亲GeSe, GeTe,PbTe等IV-VI族化合物是性能良好的中温热电材料，其Pnma相具有潜在的非简谐性和热电各向异性，具有重要的研究价值。本项目拟针对此类Pnma单晶，基于第一性原理和玻耳兹曼输运理论对本征晶格热导率、功率因子及其潜在的各向异性特点进行深入精细研究，从物理本质上探索具有层状结构单晶材料的电、声输运各向异性的起源及其调控机理，进一步提高热电ZT值。为此，充分研究声子之间的非简谐作用对于晶格热导的作用机理，揭示低本征晶格热导率的本质；全面分析晶体结构、成键方式、能带结构和声子色散谱与电、声输运参数各向异性的密切联系，建立具有各向异性热电性能的单晶材料的理论模型。本项目成果将理论指导实验制备具有优异热电性能和优势取向的单晶和多晶体系。

中文关键词： 热电材料；热导率；玻尔兹曼输运；各向异性；功率因子

英文摘要： In 2014, Lidong Zhao, etc. reported an unprecedented ZT of 2.6±0.3 realized in SnSe single crystals measured along the b axis of the Pnma structure, which represents the highest ZT value reported so far for any thermoelectric system. Sharing similar layered crystal structure, the chemical relatives of SnSe: GeSe, GeTe, PbSe, and PbTe, etc. IV-VI compounds, which are good thermoelectric materials at middle temperatures, should be highlighted for potential strong anharmonicity and anisotropy in thermoelectric properties.This proposal will employ First-pinciples calculations and Boltzmann transport theory to study elaborately the intrinsic lattice thermal conductivity, power factor and potential anisotropic thermoelectric properties, to obtain the physical nature of anisotropic electron/phonon transport on its origin and modulation mechanism for such layered single crystals. To achieve this, the anharmonic nature of crystals and its contribution to the phonon scattering rates should be fully considered to uncover the origin of low intrinsic thermal conductivity. Besides this, the anisotropy in geometry, bonding, band structure and phononic spectrum are supposed to bear an intimate relation with the anisotropy of thermoelectric properties. Based on these studies, this proposal may comprehensively build a theoretical model for the anisotropic, anharmonic thermoelectric properties of single crystals . Also, the findings and predictions are supposed to be reliable to shed light on the experimental synthesis of single crystals and polycrystals with thermoelectricity favored crystallographic directions.

英文关键词： thermoelectric materials;thermal conductivity;Boltzmann transport;anisotropy;power factor