论文总字数：26882字

摘 要

近年的研究发现I-V-VI₂型半导体热电材料具有优异的热电性能，其中以AgSbTe₂最为突出（ZT=1.3@720K，AgSbTe₂/PbTe合金：ZT =2.2 @800K），但是Te在地壳中的含量极少且较为昂贵。作为同系物，AgBiSe₂的组成元素储量更多更廉价，是一种可以考虑的替代材料。AgBiSe₂随温度变化有两次结构相变，同时具有很低的晶格热导率，但AgBiSe₂本征载流子浓度很低。所以可以经过掺杂或固溶其他元素，在保持低热导率的情况下提高其载流子浓度，从而获得理想的热电性能。本文通过固相法合成n型AgBiSe₂，并在Bi位掺杂混合价态的Sn来研究其对AgBiSe₂的热电性能的影响。实验发现Sn实际以 2价替代Bi，并将n型AgBiSe₂逐步调谐成p型半导体。作为对比实验，固溶AgSnSe₂引入Sn与直接掺杂相比并无太大差异。

关键词：I-V-VI₂型半导体 AgBi_1-xSn_xSe₂ 掺杂和固溶 热电性能

Analysis of AgBi_1-xSn_xSe₂ crystal structure and thermoelectric properties

Abstract

In recent years, studies found that the I-V-VI₂ semiconductor thermoelectric material has excellent thermoelectric properties, of which the most outstanding is AgSbTe₂ (ZT=1.3@720K, AgSbTe₂/PbTe alloy: ZT =2.2 @800K). However, Te is expensive and extremely rare. AgBiSe₂，as a homologue, has attracted attention for its earth-abundant constituent elements, which is relatively cheaper. So AgBiSe₂ can act as an alternative material. With temperature changes, AgBiSe₂ goes through two kings of phase transitions. Although AgBiSe₂ owns fairly low lattice thermal conductivity, its intrinsic carrier concentration is low. In order to obtain the ideal thermoelectric properties, we can increase its carrier concentration by doping or solid solution in the case of maintaining low thermal conductivity. In this paper, n-type AgBiSe₂ was synthesized by solid-phase method, then we investigated the effect of mixed valence state Sn doping on thermoelectric performance. we found that Sn actually replaced Bi with 2 valence and n-type AgBiSe₂ was gradually tuned into p-type semiconductors with the doping content increas. As a comparative experiment, introducing Sn by the solid state diffusion of AgSnSe₂ is not much different from that of direct doping.

Key Words: I-V-VI₂ Semiconductors; AgBi_1-xSn_xSnSe₂; Doping and Solid solution；Thermoelectric properties

目 录

摘 要 I

Abstract Ⅱ

第一章 绪论 1

1.1 热电材料 1

1.1.1 热电材料研究背景 1

1.1.2 热电转换原理 1

1.2 课题研究背景 4

1.2.1 立方I-V-VI₂型半导体 4

1.2.2 不同AgBiSe₂掺杂体系 5

1.3 选题思路和研究方法 16

第二章 实验部分 18

2.1 实验目的 18

2.2 实验原料及设备 18

2.3 实验流程 19

2.3.1 AgBiSe₂掺杂Sn 19

2.3.2 AgBiSe₂固溶AgSnSe₂ 21

第三章 数据分析 23

3.1 X射线衍射分析 23

3.1.1 AgBi_1-xSn_xSe₂样品X射线衍射数据分析 23

3.1.2 AgBiSe₂固溶AgSnSe₂样品X射线衍射数据分析 26

3.2 热电性能测试 28

3.2.1 设备和测试原理 28

3.2.2 AgBi_1-xSn_xSe₂样品热电性能数据 28

3.2.3 AgBiSe₂固溶AgSnSe₂样品热电性能数据 30

第四章 结论与展望 31

参考文献 32

致谢 35

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