叠层结构热电薄膜的电热输运规律和性能优化研究

It is very difficult to regulate coordinately all the performance parameters of a thermoelectric material. This is now a bottleneck in the field of thermoelectric materials. The fundamental reason of producing the bottleneck is that the directions of electrical transport and thermal one are the same according to the physical mechanism of the lognitudinal Seebeck effect. The research program of this project is suggested based on a problem of lacking the channels for electrical transport and thermal one along different directions in bulk thermoelectric materials experimentally discovered by us. A series of heterogeneous thermoelectric films with tilted layered structure, which are composited of thermoelectric compounds (Bi2-xSbxTe3-ySey, filled CoSb3, etc.) and metals (Bi, Cu, Ag, Fe, Ni, etc.) or semiconductor compounds (ZnO, TiO2, etc.) with obvious different properties of electricity, calorifics and/or magnetics, have been fabricated in alternating assembly pattern. The research works of this project are included: (1) to investigate systemically the fine structures on nanometer scale and atomic-molecule scale, thermal stress states, band structures, and electron structures of the heterogeneous interfaces and their influence law on the electrical and thermal transport properties; (2) to determine the selective principle of composition materials and design scenario of the heterogeneous interfaces with optimal thermal matching, optimal resistance matching, and optimal lattice matching; (3) to investigate the method of realizing the electrical transport and thermal one along different directions in the heterogeneous tilted layered structures on the condition of adscititious electric field or magnetic field along oblique orientation; (4) to clarify the influence law of adscititious electric field or magnetic field on thermoelectric performances and the physical mechanism of electrical and thermal transport in the heterogeneous tilted layered structures; (5) to investigate the relationship among thermoelectric performances and geometrical parameters (thickness, layer number, and arranged pattern) of the heterogeneous tilted layered structures. The target of this project is to establish a new method fo regulating coordinately the electrical and thermal transport properties of thermoelectric materials based on the electrical transport and thermal one along different directions.

热电材料目前面临热电性能极难协同调控的瓶颈，根本原因是电输运和热输运沿同一方向传输。针对实验发现的块体热电材料内缺乏电输运和热输运沿不同方向传输的通道问题，提出通过电学、热学和（或）磁学性能显著不同的金属或半导体与Bi2-xSbxTe3-ySey、填充CoSb3等交递组装制备异质叠层结构热电薄膜，系统研究异质界面的纳米尺度和原子分子尺度精细结构、热应力状态、能带结构和电子结构及其对电热输运性能的影响规律，确定异质界面实现最佳热阻匹配、电阻匹配和晶格匹配的组成材料选择方案和设计原则，研究倾斜取向外加电场或磁场下异质叠层结构中电输运和热输运沿不同方向传输的实现方法，阐明外加电场或磁场对电热输运性能的影响规律和异质叠层结构中电热输运的物理机制。在此基础上，研究异质叠层结构的几何参数（厚度、层数、排列方式）与电热输运性能之间的关系，建立基于电输运和热输运沿不同方向传输的电热输运性能协同调控新方法。

构建有利于电子和声子输运输的特殊通道和特定取向是实现热电性能同时优化的有效途径。本项目围绕叠层结构热电材料的制备与性能优化和内建微磁场对热电性能的影响规律开展了系统研究，取得了如下主要成果：（1）发展了层层组装原位生长方法制备高性能择优取向热电薄膜技术，制备出热电性能超过同成分块体材料、{0001}择优取向度达到99%的高性能Bi2Te3基热电薄膜，在理论和实验上证实{0001}择优取向为薄膜电输运提供了快速通道；（2）设计并制备出面向Bi2Te3基热电薄膜器件应用的Al/Cu/Ni多层薄膜电极，发现在Bi2Te3基薄膜与Cu电极之间设计Ni过渡层可以大幅度降低晶格失配引起的界面电阻，在Cu电极表面设计Al保护层可以显著提高Cu薄膜电极的热稳定性和抗氧化能力；（3）基于材料基因工程的高通量计算和筛选结果，设计出YbAl3/Bi2Te3基和Bi/Bi2Te3基2种人造倾斜叠层结构热电材料，发展了两步放电等离子体烧结与线切割加工相结合方法制造YbAl3/Bi2Te3基倾斜叠层结构块体材料方法，发展了层层堆垛模板错位遮挡方法制造Bi/Bi2Te3基倾斜叠层结构薄膜材料方法，发现两种倾斜叠层结构材料都具有高于报导最好值的横向热电发电和制冷性能；（4）首次提出在热电材料中掺入磁性纳米粒子、建立纳米尺度微磁场、协同调控电子输运和声子输运的原创思想，发现磁性纳米粒子铁磁-顺磁转变可以诱发电子库效应，磁铁-超顺磁转变可以诱发电子多重散射效应，系统研究了BaFe12O19、Fe3O4、Fe、Co和Ni等5种磁性纳米粒子复合形成的BaFe12O19/n型CoSb3基、Fe(Co,Ni)/ n型CoSb3基、Fe3O4/p型Bi2Te3基、Ni/n型Bi2Te3基等6种磁性纳米复合材料的电热协同输运规律，发现它们的热电性能大幅度提升均源于电子磁性散射和声子增强界面散射。