典型单相块体热电材料性能优化设计的实验检验

CoSb3、Bi2Te3，and half-Hueseler system are three typical alloy compounds of single phase. Recently, the multiple-localization effects by means of materials composite and atoms filling induce their thermal conductivity to decrease into a theoretical limit, and the thermoelectric efficiency to increase greatly. The further increase of the efficiency depends on integrated enhance of electronic conductivity and Seebeck coefficient, much studies have performed on it. Within the framework of energy band and Boltzmann theory, our theoretical calculations have given the power factors and ZT values as the functions of chemical potential of three kinds of the compounds. Meanwhile, the several possible doping or substitution elements and concentrations corresponding to the optimum power factors and ZT values are predicted both as n and p types materials, respectively. Within this project, we wish to perform some experimental investigations according on above theoretical design, in order to get several instinct single phase compounds with fine thermoelectric properties. Moreover, based on these mother compounds, we wish to introduce some composite phase to decrease thermal conductivity, in finally, to acquire several composites with higher ZT values.

CoSb3、Bi2Te3以及half-Hueseler体系是三类典型的单相块体热电化合物，近些年来，人们在声子玻璃-电子晶体理念指导下，通过复合、填充等手段引入多重局域效应使其声子的热导降低到接近于理论的极限,复合材料的效率大幅提高。效率的进一步提高依赖于电导率和Seebeck协调提高，人们在此问题上做了有益的尝试，取得了一定的成果。我们在前期工作中，从体系能带结构出发，给出了三个单相化合物的热电功率因子、或热电优值随温度变化的规律，并给出了最佳功率因子或热电优值对应的多种可能的n型及p型掺杂替代元素和相应浓度。本项目就是希望对前述材料的理论设计进行实验检验，以期找到几个本征热电性能优异的母相材料，并进一步的对其复合改性，降低热导，探索制备出几个热电综合性能协调，热电优值高的复合材料。

本项目主要基于三类典型的单相块体热电化合物体系：CoSb3、Bi2Te3以及half-Hueseler，对这些材料进行理论设计与实验检验，以找到几个本征热电性能优异的母相材料，并进一步的对其复合改性，降低热导，探索制备出几个热电综合性能协调，热电优值高的复合材料。主要结果可以分为一下三个部分。（1）我们首先研究本征环境友好型CoSb3热电材料的性能，通过改良合成手段，我们以Ni原子替代Co原子形成Co0.91Ni0.09Sb3的单相化合物，最终在773K实现0.6的ZT值，相较于纯样品提升了一倍。（2）我们通过控制烧结条件，金属、非金属元素掺杂，来研究孔隙率对Bi2Te3基热电材料输运影响，结果表明点缺陷随着Se元素的含量的增加而单调递减，从而解释了热电性能的变化规律。（3）通过在密度泛函理论和玻尔兹曼输运理论的框架内研究典型的拓扑半赫斯勒化合物LuPtSb，我们发现ZT值在900 K时通过静水压力从0.3急剧增加到1.5。我们的结果为研究单相热电材料提供了理论与实验指导。