摘要：Bi2Te3基热电材料具有较大的塞贝克系数和较低的热导率，是当今室温附近性能最为优异的热电制冷半导体材料，已经实现工业化生产和商业化使用。在室温附近，Bi2Te3基热电材料的最高ZT值在0.8左右，但是只有其无量纲热电优值ZT达到3，热电偶的能量转换效率才能够与传统的压缩机制冷系统相媲美。制备低维度的Bi2Te3基纳米材料，并通过掺杂调控其电和热输运特性，可有助于提高其无量纲热电优值ZT。

本文分别采用低温湿化学法和机械合金法制备Bi2Te3基纳米晶粉末材料，并分别引入杂质元素Se和Ag，运用XRD、FE-SEM等表征手段对制备的Bi2Te3和掺杂Se、Ag的样品的结构、微观形貌表征并分析，最后采用真空热压技术，对部分制备的Bi2Te3基合金粉末进行压片，测试了其热电性能，并研究了掺杂Se对Bi2Te3纳米晶热电性能的影响。

主要研究内容和结果如下：

实验结果显示，在掺入杂质Se后，在室温下样品与Bi2Te3相比其电阻率增加，增幅82%左右，在500K时样品与Bi2Te3相比其塞贝克系数的绝对值增加，增加了7μV/K，在室温下样品与Bi2Te3相比其功率因子降低，下降了43%左右，在室温下样品与Bi2Te3相比热导率降低，降低45.6%左右，在500K时，样品与Bi2Te3相比其ZT值增加，增幅54%。实验结果表明，通过在Te位掺杂Se可以显著提高Bi2Te3纳米晶的热电性能。

通过对两组样品的XRD和SEM结果的分析，发现Ag已经取代Bi掺入到Te的晶格中。但是由于Ag的共价半径小于Bi，所以导致晶格产生畸变，导致晶面间距变小。

关键词：热电材料；掺杂；Bi2Te3；纳米晶

Effect of Doping on the Properties of Bi2Te3 Nanocrystalline Thermoelectric Materials

Abstract：Bi2Te3 -based thermoelectric material has a large Seebeck coefficient and low thermal conductivity, and is the most excellent thermoelectric refrigeration semiconductor material near room temperature. It has achieved industrial production and commercial use. Near room temperature, the highest ZT value of Bi2Te3 based thermoelectric material is about 0.8, but only if its dimensionless thermoelectric figure of merit ZT reaches 3, the energy conversion efficiency of thermocouple can be compared with the traditional compressor refrigeration system. Preparation of low-dimensional Bi2Te3 based nanomaterials and their electrical and thermal transport properties by doping can help to improve their dimensionless thermoelectric figure of merit ZT.

In this paper, Bi2Te3-based nanocrystalline powders were prepared by low-temperature wet chemical method and mechanical alloying method, respectively, and impurity elements Se and

Ag were introduced respectively. The prepared Bi2Te3 and samples doped with Se and Ag were characterized by XRD and FE-SEM. The structure and microscopic morphology were characterized and analyzed. Finally, the partially prepared Bi2Te3 based alloy powders were pressed by vacuum hot-pressing technique to test their thermoelectric properties.

The main research contents and results are as follows:

1. The experimental results show that after the impurity Se is incorporated, the resistivity of the sample at room temperature increases by 82% compared with that of Bi2Te3, and the absolute value of the Seebeck coefficient increases at 500 K compared to Bi2Te3, increasing the At 7μV/K, the power factor of the sample at room temperature is reduced by about 43% compared to Bi2Te3, and the thermal conductivity of the sample at room temperature is reduced by about 45.6% compared to Bi2Te3. At 500K, the sample is compared with Bi2Te3. Its ZT value increased by 54%. The experimental results show that the thermoelectric properties of Bi2Te3 nanocrystals can be significantly improved by doping Se with Te.

2. By analyzing the XRD and SEM results of the two sets of samples, it was found that Ag has replaced Bi incorporation into the Te lattice. However, since the covalent radius of Ag is smaller than that of Bi, the crystal lattice is distorted, resulting in a small crystal plane spacing.