论文总字数：22726字

摘 要

自Imai研究化学计量比TiS₂单晶以来，1T型CdI₂类层状结构二硫化钛(TiS₂)作为一种有前途的环境友好型热电材料而备受关注，而提高其综合性能的关键在于降低其较高的晶格热导率。插层被认为是实现抑制TiS₂晶格热导率、保持良好电输运特性进而提高综合热电性能的有效方案。

(SnS)_1.2(TiS₂)₂是TiS₂的插层化合物，晶格热导率大大低于TiS₂，同时具有明显的各向异性，因此，提高显微织构度被认为是进一步改善a-b面方向热电性能的重要途径，但目前为止此方面的研究尚属空白。本课题采用液相辅助剪切粉碎工艺，先对TiS₂粉体进行液相辅助剪切粉碎处理，该方法大幅降低了晶粒尺寸，同时高结晶度得以保持，然后通过压力辅助放电等离子烧结制备了具有高度织构度的多晶陶瓷；在获得TiS₂材料输运性能基础上, 结合(SnS)_1.2(TiS₂)₂与TiS₂在能带结构、输运特性相关性，并在忽略剪切对载流子浓度和塞贝克系数的影响的前提下，对相同工艺条件下所获得的(SnS)_1.2(TiS₂)₂的织构结构及其性能进行了预测和计算。结果显示，相比于常规方法制备的(SnS)_1.2(TiS₂)₂的多晶块体样品，本方法制备样品将具有更高的电导率，300K～700K时功率因子普遍提高近60%，总热导率有所提升（约24%）；最终本方法制备样品的ZT值最大值达到0.53，超过常规方法制备的样品22%，这些结果预示织构对于提升该材料热电性能的重要作用。

关键词：热电材料; (SnS)_1.2(TiS₂)₂; 液相辅助剪切粉碎; 织构; 输运性能.

Liquid-based shear pulverization Treatment on (SnS)_1.2(TiS₂)₂ Thermoelectric Performance

ABSTRACT

1T-CdI₂-type layer structured titanium disulfide (TiS₂) has attracted much attention as a promising environment-friendly thermoelectric (TE) material, since the study on stoichiometric TiS₂ single crystal by Imai et al. Reduction of its rather high thermal conductivity is a key solution to further enhance its performance. Intercalation has thus been regarded as a feasible way to realize the suppression of thermal conductivity and consequently the TE figure of merit.

(SnS)_1.2(TiS₂)₂ is an intercalated compound of TiS₂, which shows a remarkably lowered lattice thermal conductivity and noticeable anisotropy, therefore, crystallographic texturing is considered as a critical factor to further enhance the TE performance.

In this work, a novel approach combining a liquid-based shear pulverization and spark plasma sintering (SPS) has been utilized for TiS₂ in advance, by which the grain size was reduced greatly while the high crystallinity was maintained, and a high texture degree in the bulk material was achieved as a result. Based on the relevance of the band structure and the transport properties between TiS₂ and (SnS)_1.2(TiS₂)₂, the microstructure and thermoelectric properties for bulk material of (SnS)_1.2(TiS₂)₂ obtained via a same process were predicted and calculated, without the influence of carrier concentration due to the pulverization treatment.

Results show that, as compared with the conventional ones, the (SnS)_1.2(TiS₂)₂ samples fabricated using the new approach would have a much enhanced electrical conductivity and consequently a largely improved power factor due to texturing (by 60% at 300 K to 700 K, respectively),accompanied by a relatively small increase of thermal conductivity of ~24%. Finally, the ZT value of (SnS)_1.2(TiS₂)₂ would exceed 0.53 at 700 K, which is about 22% larger than that of conventional one, suggesting a significant effect of texturing on its TE performance.

Keywords: Thermoelectric; (SnS)_1.2(TiS₂)₂; liquid-based pulverization; texturing; transport properties

目 录

摘 要 I

ABSTRACT II

第一章 绪论 1

1.1 热电材料研究背景 1

1.2 热电材料及其研究进展 1

1.2.1 热电材料及其应用 1

1.2.2 热电材料的工作原理 2

1.2.3 三大热电效应 2

1.2.4 评价热电性能的依据（ZT）值与转换效率的关系及其优化方法 3

1.2.5 热电材料的分类及其研究进展 3

1.2.6 高性能热电材料的瓶颈以及开发环保型热电材料的意义 4

1.3 TiS₂热电材料及其插层化合物(SnS)_1.2(TiS₂)₂ 4

1.3.1 TiS₂及其插层化合物研究现状 4

1.3.2 TiS₂与(SnS)_1.2(TiS₂)₂的晶体结构 7

1.3.3 TiS₂的能带结构 8

1.4 (SnS)_1.2(TiS₂)₂热电传输性能研究现状 9

1.5 本研究课题的创新点和前景 9

第二章 实验部分 11

2.1 实验原理 11

2.2 研究内容 11

2.3 实验原料及仪器 12

2.4 实验流程 13

2.4.1 具体流程 13

第三章 结果讨论与分析 14

3.1 XRD分析 14

3.2 扫描电镜分析 16

3.4 热电性能分析和预测 17

第四章 结论与展望 23

参考文献 24

1. 绪论

1.1 热电材料研究背景

考虑到全球能源作为废热损失的巨大比例，优化和开发直接将热能转化为电能的高效热电材料是非常可取的。它能把地热、太阳能、和工业废热转化成电，反之也能作为热泵实现制冷。热电器件具有全固态、轻质量、结构紧凑、响应迅速、无复杂机械运转设备以及不产生化学污染物等优点。但是目前仍存在热电转化效率和可靠性不高等问题，而热电转化系统效率的提高有赖于热电材料热电优值系数的提高、热电单元结构设计和优化及系统热阻的降低。所以本课题旨在研究一种新型的热电材料，并通过改变其制作方法来探究其性能的变化以实现当今热电材料新的突破^[1-3]。

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