论文总字数：23060字

摘 要

近期许多研究表明I-V-VI₂型化合物由于其固有的低热导性成为了理想的热电候选材料。AgBiSe₂作为I-V-VI₂型的一个典型例子，是一个依赖于温度变化而产生相变行为的多晶半导体。而AgBiSe₂的高温相（Fm3m，γ相）相对于其室温相（Pm31，α相）和中温相（R3m，β相）具有更好的电学性能。本论文试图在Bi位引入In和Ga来抑制高温相向其他相的转变，并优化材料的电导率，使得材料的热电性能得到提高。然而我们通过实验发现，In和Ga并不能成功替代Bi位，导致基体存在多相体系。可能由于Bi空位的形成，导致空穴增多，使得N型AgBiSe₂发生向P型的转变。但由于电导率的下降，整体热电性能没有得到提升。

关键词：热电材料 AgBiSe₂基 载流子浓度 相变

The Analysis of AgBiSe₂ Crystal Structure and Thermoelectric Properties by Indium and Gallium Doping

Abstract

Thermoelectric materials can directly achieve the conversion of electrical energy and thermal energy, which has become a promising functional materials for its unique performance. Recently, many studies have shown that I-V-VI₂ compounds have become the ideal thermoelectric candidate materials due to their inherent low thermal conductivity. AgBiSe₂, one example of I-V-VI₂ compounds, is a polymorphous semiconductor that shows temperature dependent phase transition behavior. The high temperature phase (Fm3m,γ phase) of AgBiSe₂ has better electrical properties than its room temperature phase (Pm31,α phase) and medium temperature phase (R3m,β phase).In this paper, we introduce In and Ga in the Bi site to suppress the transition from high temperature to other phases, and optimize the electrical conductivity of the material, which improves the thermoelectric properties of the material. However, we found that In and Ga cannot successfully replace the Bi site, what results in the existence of multi-phase matrix system. It may be the formation of Bi vacancy that causes the increase of hole, which makes N-type AgBiSe2 transform to the P-type. However, the overall thermoelectric properties have not been improved because of the decrease in conductivity.

Key Words: thermoelectric materials; AgBiSe₂-based; Carrier concentration; phase transition

目 录

摘 要 I

Abstract II

第一章 绪论 1

1.1热电材料 1

1.1.1热电材料的历史 1

1.1.2热电材料的应用 2

1.2热电效应 2

1.2.1塞贝克效应 3

1.2.2珀尔帖效应 3

1.2.3 ZT值 4

1.3研究现状 5

1.3.1 PbTe体系 5

1.3.2 Bi-Te体系 6

1.3.3 Si-Ge合金 6

1.4选题依据 7

1.4.1 AgBiSe₂体系研究现状 7

1.4.2 AgGaSe₂和AgInSe₂ 9

第二章 实验部分 10

2.1实验目的 10

2.2研究内容 10

2.3实验仪器及原料 11

2.4纯相AgGaSe₂，AgInSe₂和AgBiSe₂的制备 12

2.4.1实验流程 12

2.4.2物相分析 13

2.5 AgBi_1-xIn_xSe₂热电材料的制备与表征 15

2.5.1 实验流程 15

2.5.2 测试和表征 16

2.6 AgBi_1-xGa_xSe₂热电材料的制备与表征 17

第三章 数据分析 19

3.1 X射线衍射分析 19

3.1.1 AgBiSe₂ x%AgInSe₂ 19

3.1.2 AgBiSe₂ x%AgGaSe₂ 20

3.2 扫描电镜 21

3.3 电导率 26

3.4 塞贝克系数 27

3.5 功率因子 28

第四章 结论 30

参考文献 31

致 谢 33

第一章 绪论

1.1热电材料

随着人类文明快速发展带来的化石能源的日益枯竭，能源问题成为世界各国关注的焦点。2016年，中国消耗的能源总量大约有43.6亿吨标准煤，同比增长了1.4%^[1]。

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