论文总字数：19983字

摘 要

热电材料能将热能与电能直接转换, 在温差发电和半导体制冷领域具有广阔的应用前景。Cu₂SnS₃是常见的P型半导体热电材料。前期研究表明, Sn位Zn掺杂后, Cu₂SnS₃可获高达0.9mW/(m·K²)的功率因子, 和接近于理论最低值的高温晶格热导, 证明Cu₂SnS₃是一种类似于电子晶体声子玻璃的环境友好型热电材料的潜力候选体系。为进一步提高Cu₂SnS₃基材料的热电性能, 本论文简单地采用机械混合与分散剥离微米级MoS₂粉末添加剂所得的纳米晶体和放电等离子烧结的方法, 制备了一系列以Zn掺杂Cu₂SnS₃为基体的纳米复合材料, 用以检验引入能量过滤、提高功率因子的同时降低热导率的效果, 并探讨其作用机理。结果表明, 在本研究的特定行星磨运行条件下, 纳米级MoS₂晶粒可简单获得并分散于Cu₂SnS₃中；相比于未复合样品, 复合材料样品在少许降低电导率情况下, 功率因子获得有效提升的同时热导率进一步降低；在2mol%的最佳复合比例下, 热电优值ZT达到0.89 (723 K), 较未复合样品(ZT = 0.46)提升近1倍, 是迄今为止同温条件下硫化物的最高值。这些发现验证了MoS₂纳米复合工艺路线对该体系热电性能的显著提升作用。

关键词：Cu₂SnS₃ 热电材料 MoS₂ 纳米复合 热电性能

ABSTRACT

Thermoelectric materials can directly convert thermal energy and electric energy, and have broad application prospects in the field of thermoelectric power generation and semiconductor refrigeration. Cu₂SnS₃ is a common P-type semiconductor thermoelectric material. Through Sn-site-Zn-doping, a high power factor of ~0.9 mW/(m·K²) and a low lattice thermal conductivity close to theoretical minimum (0.3 W/(m K)) have been previously obtained in Zn-doped Cu₂SnS₃ which evidenced itself as a promising electron-crystal-phonon-glass-like environmentally-friendly thermoelectric candidate. In the present thesis, in order to further improve the thermoelectric performance of Cu₂SnS₃-based materials, a series of dense bulk ceramics of nanocomposite with heavily Zn-doped Cu₂SnS₃ as the matrix were prepared by spark plasma sintering, where nanoscale layer-structured MoS₂ particles were incorporated simply by mechanically dispersing and at the same time exfoliating micro-sale MoS₂ powder as an additive with the doped Cu₂SnS₃ powder, in an attempt to examine and clarify the mechanism of the combined effects of introducing the energy filtering effect to enhance the power factor and simultaneously suppressing the thermal conductivity. Results show, under a specified condition of planetary mechanical ball milling, nano-scale MoS₂ can be dispersed in the matrix, and as a result, an effective enhancement of power factor at a small sacrifice of electrical conductivity was achieved, accompanied with a further decreased thermal conductivity compared to that of the purely Zn-doped counterpart, and finally, with an optimal addition of 2 mol% MoS₂, a high ZT of ~0.89 at 723 K was realized, which is increased by ~100 % relative to the Zn-doped sample and stands the top so far among the sulfide thermoelectrics at the same temperature. These findings evidenced the significant effectiveness of the nanocomposite approach using MoS₂ layered nanostructures.

Key Words: Cu₂SnS₃; Thermoelectric materials; MoS₂; Nanocomposite; Thermoelectric properties

目录

摘 要 Ⅰ

ABSTRACT Ⅱ

第一章 绪论 1

1.1 热电材料发展史 1

1.2 热电效应的基本原理 1

1.2.1 赛贝克效应 1

1.2.2 帕尔帖效应 2

1.2.3 汤姆逊效应 2

1.3 热电优值 2

1.4提高热电性能的方法 3

1.4.1 晶格掺杂 3

1.4.2 纳米化和低维化 3

1.5热电材料的应用 4

1.5.1热电发电的应用 4

1.5.2热电制冷的应用 4

1.6 硫族化合物热电材料 4

1.6.1 Cu₂SnS₃ 4

1.6.2 Zn掺杂Cu₂SnS₃ 5

第二章 MoS₂ 7

2.1 MoS₂的简介 7

2.2 MoS₂的结构 7

2.3 MoS₂的性质与应用 7

2.3 .1 MoS₂的性质 7

2.3 .2 MoS₂的应用 7

2.3 .3 MoS₂的电输运特性 8

2.4 MoS₂的制备 8

2.5 本课题的研究内容 9

第三章 实验部分 11

3.1纳米粉体样品合成 10

3.1.1 Cu₂SnS₃的固相合成 11

3.1.2 MoS₂与Cu₂SnS₃的复合 12

3.2 块体制备 13

3.3 物相分析 15

3.3.1 XRD分析 15

3.3.2 SEM观察形貌特征 17

3.4 热电性能测试 18

3.4.1电导率 18

3.4.2 赛贝克系数 20

3.4.3 功率因子 22

3.5热电优值的计算 24

第四章 结论与展望 25

4.1结论 25

4.2展望 25

参考文献 26

致谢 28

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