Se掺杂量对n型Bi2Te3-<italic>x</italic>Se<italic>x</italic>微结构及热电性能的影响

引用本文

张骐昊, 徐磊磊, 王连军, 江莞. Se掺杂量对n型Bi₂Te_3-_xSe_x微结构及热电性能的影响 . 无机材料学报, 2014, 29(11): 1139-1144
ZHANG Qi-Hao, XU Lei-Lei, WANG Lian-Jun, JIANG Wan. Effects of Different Amount of Se-doping on Microstructures and Thermoelectric Properties of n-type Bi₂Te_3-_xSe_x . Journal of Inorganic Materials, 2014, 29(11): 1139-1144 复制到剪切板

Permissions

This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

Se掺杂量对n型Bi₂Te_3-_xSe_x微结构及热电性能的影响

张骐昊, 徐磊磊, 王连军, 江莞

东华大学纤维材料改性国家重点实验室, 上海201620

通讯作者: 王连军, 教授. E-mail:wanglj@dhu.edu.cn

作者简介: 张骐昊 (1988-), 男, 硕士研究生. E-mail:zqh378@163.com

基金:国家自然科学基金(51374078); 上海市科学技术委员会(13JC1400100, 12QH1400100);

摘要

通过水热法合成不同Se掺杂量的Bi₂Te_3-_xSe_x (0 ≤x ≤0.45)纳米粉体, 采用放电等离子烧结技术, 制备出致密度较高的块体材料。通过X射线衍射、扫描电镜、透射电镜等测试手段对材料的微结构进行了表征, 并重点研究了含有不同Se掺杂量块体材料的显微结构和热电性能。结果表明: Se元素的掺杂使得粉体XRD特征衍射峰向高角度偏移, 并且衍射峰出现宽化, 晶粒尺寸变小。随着Se掺杂量的增加, 块体材料的电导率先增大后减小; Se元素的掺杂有效地降低了材料的热导率, 并提高了材料的Seebeck系数。研究结果表明: 在整个测试温度区间, 所有经过Se掺杂的样品ZT值都高于未掺杂样品。当Se掺杂量为0.3时, 样品具有最大的ZT值, 平均约为0.51, 并在475 K时达到最大值0.57, 相比未经Se掺杂的Bi₂Te₃提高了159%。

关键词: 碲化铋; 硒掺杂; 水热合成; 放电等离子体烧结; 热电性能

中图分类号:TN304 文献标志码:A 文章编号:1000-324X(2014)11-1139-06

Effects of Different Amount of Se-doping on Microstructures and Thermoelectric Properties of n-type Bi₂Te_3-_xSe_x

ZHANG Qi-Hao, XU Lei-Lei, WANG Lian-Jun, JIANG Wan

State Key Laboratory for Modification of Chemical Fibers and Polymer Materials, Donghua University, Shanghai 201620, China

Fund:National Natural Science Foundation of China (51374078); Shanghai Committee of Science and Technology (13JC1400100, 12QH1400100);

Abstract

A hydrothermal method combined with a subsequent spark plasma sintering technique was successfully utilized to synthesize selenium (Se) doped bismuth telluride (Bi₂Te_3-_xSe_x) (0≤x≤0.45). The influence of Se-doping on the composition and morphology of n-type Bi₂Te_3-_xSe_x was studied by X-ray diffraction, scanning electron microscope and transmission electron microscope. Thermoelectric properties of the as-prepared bulk Bi₂Te_3-_xSe_x nanocomposites were investigated in detail. Results showed that the grain became finer by the Se-doping. With increasing Se doping content, the electrical conductivity of bulk Bi₂Te_3-_xSe_x increased firstly and then decreased. Se-doping effectively reduced the thermal conductivity and improved the Seebeck coefficient to some extent. Consequently, a maximumZTvalue of 0.57 was obtained from bulk Bi₂Te_2.7Se_0.3 at 475 K, which was increased by 159% as compared with pure bulk Bi₂Te₃.

Keyword: bismuth telluride; Se-doping; hydrothermal synthesis; spark plasma sintering; thermoelectric properties

Show Figures

近年来, 随着能源危机和环境污染的日益严重, 开发绿色清洁新能源、探索余热废热回收利用技术引起了各国的高度重视。热电材料作为一种有效地实现热能和电能直接转化的新型功能材料, 在热电制冷和温差发电领域具有广泛的应用前景^{[ 1]}。材料的热电性能取决于热电优值 ZT值, ( ZT = α²σT/ κ, 其中 α是Seebeck系数, σ是电导率, T是绝对温度, κ是热导率), ZT值越大, 则材料的热电转换效率越高^{[ 2]}。Bi₂Te₃及其固溶体合金是研究最早的也是最成熟的热电材料之一, 是目前室温下热电性能最好的材料, 已广泛应用于半导体制冷元件^{[ 3]}。但是由于Bi₂Te₃的 ZT值不够高, 因而没有得到大规模应用。如何进一步提高Bi₂Te₃的热电性能, 实现其商业化, 是当前急需解决的问题。

从材料的组成来讲, 形成固溶体合金是提高材料热电性能的有效途径^{[ 4, 5, 6]}。该方法是在材料的晶体结构中引入适当的短程无序而不改变晶格的长程有序。这种点缺陷不会对波长相对较长的载流子产生较强的散射, 可以在保持迁移率不发生明显变化的条件下降低材料的热导率, 从而优化材料的热电优值。另外, 材料的热电性能强烈依赖于费米能级, 而费米能级的高低主要由载流子浓度决定。掺杂适当元素, 可以有效调节载流子浓度, 进而优化材料的热电性能。

硫族(Te、Se)^{[ 7, 8, 9, 10]}和氮族(Bi、Sb)^{[ 11, 12, 13]}等元素是掺杂的首选, 大多数报道采用球磨和热压相结合的传统方法进行掺杂, 但是其制备时间长, 成本高。本工作采用水热法合成了不同Se掺杂量的Bi₂Te_3- _xSe _x纳米粉体, 然后利用放电等离子体烧结(SPS)技术, 制备出结构致密的合金块体。利用合金化和纳米化的协同作用进一步降低材料热导率, 提高热电性能。主要研究了不同Se掺杂量对Bi₂Te_3- _xSe _x粉体、块体相结构、微观形貌和热电性能的影响, 确定了最佳的Se元素掺杂量。

1 实验方法

1.1 样品制备

以Te粉(99.9999%)、Se粉(99%)、BiCl₃(分析纯)为原料, 按照Bi₂Te_3- _xSe _x( x=0.1、0.15、0.3、0.45)的化学计量比精确称取原料。将原料在烧杯中混合均匀, 以去离子水为溶剂, NaOH为pH调节剂, NaBH₄为还原剂, EDTA为包覆剂, 超声振荡1 h后转移至WDF型高压反应釜中, 在200℃下保温8 h, 冷却至室温后, 对所得到的混合溶液进行抽滤, 并反复用去离子水和无水乙醇清洗, 最后在60℃下真空干燥6 h, 得到黑色合金粉末。用Dr Sinter-SPS 725放电等离子烧结炉对粉体进行烧结: 石墨模具内径为10 mm; 采用两步加压, 即初始加压30 MPa, 升温速率为50~100 ℃/min; 最终保温压力为80 MPa, 保温温度为350℃, 保温时间为6 min。

1.2 样品表征

通过日本Rigaku D/Max-2550 PC型X射线衍射 (X-ray diffraction, XRD)仪对样品进行物相分析。用日本S-4800型场发射扫描电子显微镜 (Field emission scanning electron microscope, FESEM) 、2100F型透射电子显微镜(Transmission electron microscope, TEM)观察粉体和块体样品的微观形态。用日本ULVAC-RIKO, ZEM-3型热电测试装置同时测量块体样品的电导率和Seebeck系数。利用 Archimedes 排水法原理测得块体材料的密度( ρ); 采用德国Netzsch LFA427型热导仪, 应用激光脉冲技术在Ar气氛中测定样品热扩散系数( λ); 利用耐驰差示扫描量热仪(204F1)测量材料的热容( C_p), 由公式 κ = λC_p ρ计算得到材料的热导率。

2 结果与讨论

2.1 不同Se掺杂量的Bi₂Te_3- _xSe _x纳米粉体的分析

图1为不同Se掺杂量的Bi₂Te_3- _xSe _x纳米粉体的XRD图谱。从图1(a)中可以看出, 与单相Bi₂Te₃的衍射峰相对比, 所有化合物均具有斜方六面体晶体结构(空间群R3m), 没有杂峰出现。一些衍射峰为接近的两个峰的交叠, 特别是三强峰尤为明显, 这与文献[14]报道一致。由此判断, 合成粉体由结构相似且成份相近的两相组成, 其中一相接近Bi₂Te₃, 另一相接近于Bi₂Se₃。随着Se含量的增加, Bi₂Te_3- _xSe _x的特征峰强度减弱。合成粉体的(015)特征峰(图1(b))随 x值的增大向高角度偏移, 由Bi₂Te₃的27.66°转变为Bi₂Te_2.55Se_0.45的27.90°, 并且衍射峰也更宽化, 表明晶粒尺寸变小。

	Figure Option View Download New Window
	图1 不同Se掺杂量的Bi₂Te_3- _xSe _x纳米粉体的XRD图谱Fig. 1 XRD patterns of Bi₂Te_3- _xSe _x nanopowders being doped with different Se-doping contents

图2为不同Se掺杂量的Bi₂Te_3- _xSe _x纳米粉体的电镜照片, 从图中可以看出, 粉体分散性较好, 没有明显的团聚现象。合成粉体为细小的、具有不规则形状的纳米颗粒。从图2(a~c)可以看出, 不规则状粉体颗粒尺寸从80 nm减小到50 nm, 这表明随着掺入半径较小的Se元素, 合金粉体尺寸变小, 这与XRD分析结果相一致。图2(d)为Bi₂Te_2.55Se_0.45粉体高倍透射电镜照片, 图中晶粒的晶面间距为0.319、0.217 nm分别对应于Bi₂Te_2.55Se_0.45化合物斜方六面体结构的(015)和(110)点阵面, 相比Bi₂Te₃单相, 其晶面间距有所减小。

	Figure Option View Download New Window
	图2 不同Se掺杂量的Bi₂Te_3- _xSe _x纳米粉体的场发射扫描电镜和透射电镜照片Fig. 2 FE-SEM and HRTEM images of Bi₂Te_3- _xSe _xnano-powder being doped with different Se contentsSEM images of (a) Bi₂Te_2.9Se_0.1, (b) Bi₂Te_2.7Se_0.3 and (c) Bi₂Te_2.55Se_0.45, HRTEM image of (d) Bi₂Te_2.55Se_0.45 nanopowder

2.2 不同Se掺杂量的Bi₂Te_3- _xSe _x块体的断面形貌

图3是采用SPS烧结制备的块体Bi₂Te_3- _xSe _x样品的断口形貌。从图3中可以看出, 经过SPS烧结, Bi₂Te_3- _xSe _x主要呈片状结构, 并也含有少量不规则状晶粒, 没有明显的择优取向, 并且可以看到所有样品微观结构都呈大晶粒中间穿插着一些小晶粒形貌, 属于典型的微纳多尺度结构。由于一些微小的晶粒填充到大晶粒的空隙之间, 提高了块体样品的致密度, 所有样品的相对密度均在98.9%以上(表1)。由于Te⁽¹⁾-Te⁽¹⁾原子之间以较弱的范德华力相结合, 断口呈现出“台阶式”的解理, 表现为脆性的穿晶断裂^{[ 15]}。另外, Bi₂Te_3- _xSe _x纳米粉体在SPS烧结过程中晶粒长大, 由50~100 nm大小的晶粒长大为平均尺寸约0.5~1 μm晶粒。随着Se元素掺杂量的增加, 晶粒内的解理程度下降。从图3(a~e)可以看出, SPS烧结后样品颗粒尺寸先增大后减小, 选取Bi₂Te_2.55Se_0.45某一区域放大(图3f), 可见样品晶粒尺寸较小, 平均约为400 nm, 呈现晶粒交叉排列的层状结构。

	Figure Option View Download New Window
	图3 不同Se掺杂量的Bi₂Te_3- _xSe _x块体的断面形貌Fig. 3 Fractured surfaces′ morphologies of bulk Bi₂Te_3- _xSe _x being doped with different Se contents(a) Bi₂Te_3; (b) Bi₂Te_2.9Se_0.1; (c) Bi₂Te_2.85Se_0.15; (d) Bi₂Te_2.7Se_0.3; (e) and (f) Bi₂Te_2.55Se_0.45

表1 不同Se掺杂量的Bi₂Te_3- _xSe _x块体密度及相对密度 Tables 1 Densities and relative densities of Bi₂Te_3- _xSe _xbulk samples being doped with different Se contents

2.3 不同Se掺杂量的Bi₂Te_3- _xSe _x块体的热电性能

图4是不同Se掺杂量的Bi₂Te_3- _xSe _x块体的电导率随温度的变化关系, 从图中可以看出, 所有Bi₂Te_3- _xSe _x样品的电导率都随温度的升高而降低, 呈现出金属导电特性(d σ/d T<0)。随着Se含量的增加, 电导率波动较大, Bi₂Te_2.9Se_0.1样品的电导率最大。室温下, 最大电导率为1.17×10⁵S/m, 该值相比Bi₂Te₃块体室温下的0.433×10⁵S/m提升了1.7倍。而Bi₂Te_2.55Se_0.45样品的电导率最低, 其电导率在室温下低至0.35×10⁵S/m, 这与文献报道的Bi₂Te₃基体电导率随Se掺杂量增加而降低的趋势相似^{[ 16]}。这是由于样品电导率的变化主要取决于载流子浓度和载流子迁移率的改变。一方面, Se的掺杂会增加载流子浓度, 导致电导率增大; 但另一方面, 随着Se的掺杂量增加, 块体样品晶粒逐渐变小, 这会在材料内部引入更多的晶界, 而增加载流子的散射, 减弱载流子迁移率, 导致样品的电导率降低^{[ 7]}。

	Figure Option View Download New Window
	图4 不同Se掺杂量的Bi₂Te_3- _xSe _x块体的电导率随温度的变化关系Fig. 4 Temperature dependence of electrical conductivity for Bi₂Te_3- _xSe _x bulk samples being doped with different Se contents

图5是不同Se掺杂量的Bi₂Te_3- _xSe _x块体的Seebeck系数随温度的变化关系, 由图可知: 所有样品的Seebeck系数都为负值, 表明样品均为n型半导体, 载流子为电子。当 x=0.45时, 块体样品的Seebeck系数明显增加, 在350 K时取得最大值 (-175 μV/K)。同时这一数值也高于之前文献报道的Bi₂Te_2.55Se_0.45在该温度下的Seebeck系数^{[ 16]}。然而Bi₂Te_2.9Se_0.1的Seebeck系数平均值却比纯Bi₂Te₃的低, 与其高电导率关系恰好相反, 这也符合Seebeck系数 α与电导率 σ成反比的关系。另外, 所有样品Seebeck系数均随测试温度的升高先增加后减小, 与文献[14, 16]报道相符。这是由于随着温度升高, 没有电离完全的掺杂离子逐渐电离, 离化杂质浓度提高, 离化杂质散射因子变大, 导致Seebeck系数也相应增大; 但Se掺杂为浅能级掺杂, 当测量温度升高到一定程度时, 杂质能级即可电离为导带电子和价带空穴, 成为本征半导体^{[ 17]}。随着测量温度升高而进入本征导电区以后, 样品中同时存在电子和空穴两种载流子, 如果继续升高测量温度便会出现Seebeck系数随温度升高而减小的结果。图5中Seebeck系数的转折即表明本征载流子的数量激增, 在高温端由本征导电引起Seebck系数减小的现象在400 K以上表现得尤为明显。

	Figure Option View Download New Window
	图5 不同Se掺杂量的Bi₂Te_3- _xSe _x块体的Seebeck系数随温度的变化关系Fig. 5 Temperature dependence of Seebeck coefficient for Bi₂Te_3- _xSe _x bulk samples being doped with different Se contents

图6是不同Se掺杂量的Bi₂Te_3- _xSe _x块体的热导率、晶格热导率随温度的变化关系。材料热导率( K)主要由载流子热导率( K_C)和晶格热导率( K_L)两部分组成, 即 K = K_C+ K_L。根据Wiedemann-Frantz定律, 载流子热导率与温度和载流子浓度成正比, 即 K_C= LTσ。而对于强简并半导体, L通常取2.45×10^-8W/(m·K)^{[ 14]}。从图6(a)中可以看出: 随着Se元素掺杂量的增大, 样品的热导率逐渐减小, 从单相Bi₂Te₃的热导率平均值1.4 W/(m·K)逐步降到Bi₂Te_2.55Se_0.45的1.0 W/(m·K)。当 x=0.45时, 总热导率在325 K时达到最小值0.9 W/(m·K)。热导率的显著降低是因为Se掺杂引起的合金散射不仅降低了样品的载流子迁移率, 并且增大了对声子的散射作用, 进而显著地降低了样品的晶格热导率, 如图6(b)所示。另外, 对于固溶体合金材料, 由于点缺陷的引入大大增加了对高频短波声子的散射, 高频声子对热导率的贡献明显减小。此时, 材料的晶格热导率主要来自低频声子的贡献, 晶界散射作用相对增加而变得重要, 从而减小了声子平均自由程和导热系数^{[ 2]}。

	Figure Option View Download New Window
	图 6 不同Se掺杂量的Bi₂Te_3- _xSe _x块体(a)热导率和(b)晶格热导率随温度的变化关系Fig. 6 Temperature dependence of (a) thermal conductivity and (b) lattice thermal conductivity for Bi₂Te_3- _xSe _xbulk samples being doped with different Se contents

根据实验测得的电导率、Seebeck系数以及热导率, 由公式 ZT = α²σT/ κ计算样品在测试温度范围内热电优值。从图7中可以看到, 样品的 ZT值总体上随温度升高先增大后减小。在整个温度区间,掺Se后块体的 ZT值明显高于单相Bi₂Te₃样品, 随着Se掺杂量的增加, 样品的 ZT值表现为先增大后减小。当掺杂量 x=0.3时, 样品具有最大的 ZT值, 平均约为0.51, 并在475 K时达到最大值0.57。

	Figure Option View Download New Window
	图7 不同Se掺杂量的Bi₂Te_3- _xSe _x块体的 ZT值随温度的变化关系Fig. 7 Temperature dependence of ZT for Bi₂Te_3- _xSe _x bulk samples being doped with different Se contents

3 结论

采用水热法合成不同Se掺杂量的Bi₂Te_3- _xSe _x纳米粉体, 采用放电等离子烧结技术, 制备出较高致密度的块体材料。通过研究不同Se掺杂量对Bi₂Te_3- _xSe _x微结构及热电性能的影响, 得出以下结论:

1) 随着Se掺杂量的增大, 粉体XRD特征峰向高角度偏移, 并且衍射峰出现宽化, 结合SEM和TEM表明晶粒尺寸逐渐变小; 块体样品具有较高的致密度, 所有样品的相对密度均在98.9%以上; 断口呈现出“台阶式”的解理, 表现为脆性的穿晶断裂;

2) 随着Se掺杂量的增大, 样品的电导率先增大后减小; Se元素的掺杂有效地降低了块体Bi₂Te₃基体的热导率, 并在一定程度上提高了材料的Seebeck系数; 在整个测试温度区间, 所有经过Se掺杂的样品 ZT值都高于未掺杂样品; 当Se掺杂量 x为0.3时, 样品具有最大的 ZT值, 平均约为0.51, 并在475 K时具有最大值0.57, 相比未经Se掺杂的Bi₂Te₃提高了159%。

参考文献

View Option

[1]	NOLAS G S, SHARP J, GOLDSMID H J. Thermoelectrics: Basic Principles and New Materials Developments. Springer: New York, 2001: 17-29. [本文引用:1]
[2]	POUDEL B, HAO Q, MA Y, et al. High-thermoelectric performance of nanostructured bismuth antimony telluride bulk alloys. Science, 2008, 320: 634-638. [本文引用:2]
[3]	HOU XIAN-HUA, HU SHE-JUN, RU QIANG, et al. Current status and development of Bi₂Te₃-based thermoelectric materials. Materials Review, 2007, 21(7): 111-118. [本文引用:1] [CJCR: 0.603]
[4]	CHEN G, DRESSELHAUS M S, FLEURIAL J P, et al. Recent developments in thermoelectric materials. International Material Reviews, 2003, 48(1): 45-66. [本文引用:1] [JCR: 7.48]
[5]	MINNICH A J, DRESSELHAUS M S, REN Z F, et al. Bulk nanostructured thermoelectric materials: current research and future prospects. Energy Environ Sci, 2009, 2: 466-479. [本文引用:1] [JCR: 11.653]
[6]	SOOTSMAN J R, CHUNG D Y, KANATZIDIS M G. New and old concepts in thermoelectric materials. Angew. Chem. Int. Ed, 2009, 48: 8616-8639. [本文引用:1]
[7]	XIAO Y, POUDEL B, MA Y, et al. Experimental studies on anisotropic thermoelectric properties and structures of n-type Bi₂Te_{2. 7}Se_{0. 3}. Nano Letters, 2010, 10(9): 3373-3378. [本文引用:2] [JCR: 13.025]
[8]	ZHANG Y C, WANG H, KRAEMER S, et al. Surfactant-free synthesis of Bi₂Te₃-Te micro-nano heterostructure with enhanced thermoelectric figure of merit. ACS Nano, 2011, 4: 3158-3165. [本文引用:1] [JCR: 12.062]
[9]	樊希安. (Bi, Sb)₂(Te, Se)₃系热电材料的制备及性能优化研究. 武汉: 华中科技大学博士学位论文, 2007. [本文引用:1]
[10]	LI D, QIN X Y, LIU Y F, et al. Improved thermoelectric properties for solution grown Bi₂Te_3-xSe_x nanoplatelet composites. RSC Adv. , 2013, 3: 2632-2638. [本文引用:1]
[11]	MA Y, CHEN G, REN Z F, et al. Enhanced thermoelectric figure-of-merit in p-Type nanostructured bismuth antimony tellurium alloys made from elemental chunks. Nano Lett. , 2008, 8: 2580-2584. [本文引用:1] [JCR: 13.025]
[12]	CAO Y Q, ZHAO X B, ZHANG X B, et al. Syntheses and thermoelectric properties of Bi₂Te₃/Sb₂Te₃ bulk nanocomposites with laminated nanostructure. Appl. Phys. Lett. , 2008, 92: 143106-1-3. [本文引用:1] [JCR: 3.794]
[13]	XIE W, TANG X, TRITT T M, et al. High thermoelectric performance BiSbTe alloy with unique low-dimensional structure. J. Appl. Phys. , 2009, 105: 113713-113718. [本文引用:1] [JCR: 0.71]
[14]	NI HUA-LIANG, ZHU TIE-JUN, ZHAO XIN-BING. Thermoelectric properties of hydrothermal synthesized Bi-Te-Se alloys. Journal of Functional Materials, 2006, 10(37): 1561-1563. [本文引用:1] [CJCR: 0.588]
[15]	LV QIANG, CHENG YING, WANG JING-JU, et al. Preparation of Bi₂Te₃-based p-type pseudoternary thermoelectric materials by the hot-press method and their properties. Journal of the Chinese Ceramic Society, 2008, 36(5): 683-688. [本文引用:1] [CJCR: 0.969]
[16]	LI D, QIN X Y, DOU Y C, et al. Thermoelectric properties of hydrothermally synthesized Bi₂Te_3-xSe_x nanocrystals. Scripta Materialia, 2012, 67: 161-164. [本文引用:2] [JCR: 2.821]
[17]	JIANG J, CHEN L D, BAI S Q, et al. Fabrication and thermoelectric performance of textured n-type Bi₂(Te, Se)₃ by spark plasma sintering. Material Science Engineering B, 2005, 117(3): 334-338. [本文引用:1] [JCR: 1.846]

2001

0.0

... 热电材料作为一种有效地实现热能和电能直接转化的新型功能材料, 在热电制冷和温差发电领域具有广泛的应用前景^[1] ...

2008

0.0

Science. 2008, 320(5876):634-638

High-Thermoelectric Performance of Nanostructured Bismuth Antimony Telluride Bulk Alloys

Bed Poudel 1 , 2 , * , Qing Hao 3 , * , Yi Ma 1 , 2 , Yucheng Lan 1 , Austin Minnich 3 , Bo Yu 1 , Xiao Yan 1 , Dezhi Wang 1 , Andrew Muto 3 , Daryoosh Vashaee 3 , Xiaoyuan Chen 3 , Junming Liu 4 , Mildred S. Dresselhaus 5 , Gang Chen 3 , † , Zhifeng Ren 1 , †

1 Department of Physics, Boston College, Chestnut Hill, MA 02467, USA. 2 GMZ Energy, Incorporated, 12A Hawthorn Street, Newton, MA 02458, USA. 3 Department of Mechanical Engineering, Massachusetts Institute of Technology (MIT), Cambridge, MA 02139, USA. 4 Laboratory of Solid State Microstructures and Department of Physics, Nanjing University, China. 5 Department of Physics and Department of Electrical Engineering and Computer Science, MIT, Cambridge, MA 02139, USA. ↵ † To whom correspondence should be addressed. E-mail: gchen2@mit.edu (G.C.); renzh@bc.edu (Z.R.)

... 是热导率), ZT值越大, 则材料的热电转换效率越高^[2] ...

... 此时, 材料的晶格热导率主要来自低频声子的贡献, 晶界散射作用相对增加而变得重要, 从而减小了声子平均自由程和导热系数^[2] ...

2007

0.0

0.603

... Bi₂Te₃及其固溶体合金是研究最早的也是最成熟的热电材料之一, 是目前室温下热电性能最好的材料, 已广泛应用于半导体制冷元件^[3] ...

2003

7.48

0.0

... 从材料的组成来讲, 形成固溶体合金是提高材料热电性能的有效途径^[4,5,6] ...

2009

11.653

0.0

... 从材料的组成来讲, 形成固溶体合金是提高材料热电性能的有效途径^[4,5,6] ...

2009

0.0

Angewandte Chemie International Edition. 2009, 48(46):8616-8639

New and Old Concepts in Thermoelectric Materials

Joseph R. Sootsman 1 ,Duck Young Chung Dr. 2 andMercouri G. Kanatzidis Prof. 1,2

1 Department of Chemistry, Northwestern University, 2145 Sheridan Rd., Evanston, IL 60208 (USA) 2 Materials Science Division, Argonne National Lab, Argonne, IL 60439 (USA)

> Herein we cover the key concepts in the field of thermoelectric materials research, present the current understanding, and show the latest developments. Current research is aimed at increasing the thermoelectric figure of merit (ZT) by maximizing the power factor and/or minimizing the thermal conductivity. Attempts at maximizing the power factor include the development of new materials, optimization of existing materials by doping, and the exploration of nanoscale materials. The minimization of the thermal conductivity can come through solid-solution alloying, use of materials with intrinsically low thermal conductivity, and nanostructuring. Herein we describe the most promising bulk materials with emphasis on results from the last decade. Single-phase bulk materials are discussed in terms of chemistry, crystal structure, physical properties, and optimization of thermoelectric performance. The new opportunities for enhanced performance bulk nanostructured composite materials are examined and a look into the not so distant future is attempted.

... 从材料的组成来讲, 形成固溶体合金是提高材料热电性能的有效途径^[4,5,6] ...

2010

13.025

0.0

Nano Letters. 2010, 10(9):3373–3378-null

Experimental Studies on Anisotropic Thermoelectric Properties and Structures of n-Type Bi₂Te_2.7Se_0.3

Xiao Yan † , Bed Poudel ‡ , Yi Ma ‡ , W. S. Liu † , G. Joshi † , Hui Wang † , Yucheng Lan † , Dezhi Wang † , Gang Chen * § and Z. F. Ren * †

† Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467 ‡ GMZ Energy, Inc., 11 Wall Street, Waltham, Massachusetts 02453 § Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139 * To whom correspondence should be addressed, gchen2@mit.edu and renzh@bc.edu .

The peak dimensionless thermoelectric figure-of-merit (ZT) of Bi 2 Te 3 -based n-type single crystals is about 0.85 in the ab plane at room temperature, which has not been improved over the last 50 years due to the high thermal conductivity of 1.65 W m −1 K −1 even though the power factor is 47 × 10 −4 W m −1 K −2 . In samples with random grain orientations, we found that the thermal conductivity can be decreased by making grain size smaller through ball milling and hot pressing, but the power factor decreased with a similar percentage, resulting in no gain in ZT. Reorienting the ab planes of the small crystals by repressing the as-pressed samples enhanced the peak ZT from 0.85 to 1.04 at about 125 °C, a 22% improvement, mainly due to the more increase on power factor than on thermal conductivity. Further improvement is expected when the ab plane of most of the small crystals is reoriented to the direction perpendicular to the press direction and grains are made even smaller.

... 硫族(Te、Se)^[7,8,9,10]和氮族(Bi、Sb)^[11,12,13]等元素是掺杂的首选, 大多数报道采用球磨和热压相结合的传统方法进行掺杂, 但是其制备时间长, 成本高 ...

... 但另一方面, 随着Se的掺杂量增加, 块体样品晶粒逐渐变小, 这会在材料内部引入更多的晶界, 而增加载流子的散射, 减弱载流子迁移率, 导致样品的电导率降低^[7] ...

2011

12.062

0.0

2007

0.0

2013

0.0

2008

13.025

0.0

Nano Lett.. 2008, 8(8):2580–2584-null

Enhanced Thermoelectric Figure-of-Merit in p-Type Nanostructured Bismuth Antimony Tellurium Alloys Made from Elemental Chunks

Yi Ma † ‡ , Qing Hao § , Bed Poudel † ‡ , Yucheng Lan † , Bo Yu † , Dezhi Wang † , Gang Chen * § and Zhifeng Ren * †

Department of Physics, Boston College, Chestnut Hill, Massachusetts 02467, GMZ Energy, Inc., 12A Hawthorn Street, Newton, Massachusetts 02458, and Department of Mechanical Engineering, MIT, Cambridge, Massachusetts 02139 * To whom correspondence should be addressed. E-mail: gchen2@mit.edu (G.C.) and renzh@bc.edu (Z.R.).,† Boston College. ,‡ GMZ Energy, Inc. ,§ MIT.

By ball milling alloyed bulk crystalline ingots into nanopowders and hot pressing them, we had demonstrated high figure-of-merit in nanostructured bulk bismuth antimony telluride. In this study, we use the same ball milling and hot press technique, but start with elemental chunks of bismuth, antimony, and tellurium to avoid the ingot formation step. We show that a peak ZT of about 1.3 in the temperature range of 75 and 100 °C has been achieved. This process is more economical and environmentally friendly than starting from alloyed bulk crystalline ingots. The ZT improvement is caused mostly by the lower thermal conductivity, similar as the case using ingot. Transmission electron microscopy observations of the microstructures suggest that the lower thermal conductivity is mainly due to the increased phonon scattering from the increased grain boundaries of the nanograins, precipitates, nanodots, and defects. Our material also exhibits a ZT of 0.7 at 250 °C, similar to the value obtained when ingot was used. This study demonstrates that high ZT values can be achieved in nanostructured bulk materials with ball milling elemental chunks, suggesting that the approach can be applied to other materials that are hard to be made into ingot, in addition to its advantage of lower manufacturing cost.

2008

3.794

0.0

2009

0.71

0.0

2006

0.0

0.588

Journal of Functional Materials. 2006, 10(37):1561-1563

Thermoelectric properties of hydrothermal synthesized Bi-Te-Se alloys

用水热法在473K下反应24h,制备了Bi-Te-Se三元合金.其粉末产物由结构相同成份接近的两相Bi-Te-Se合金组成.粉末在523K,50MPa压力下热压成的块材也是两相结构.粉末和块体材料的微观形貌均由层片状颗粒组成,层片厚度为100nm左右.通过改变Te的相对含量,可以调节施主掺杂浓度.材料具有很低的热导率,在349K时试样Bi2Te2.85Se0.45具有晶格热导率最低值为0.33W/m·K.此时,它也具有最高的ZT值为0.60.

... K)^[14] ...

2008

0.0

0.969

... 由于Te⁽¹⁾-Te⁽¹⁾原子之间以较弱的范德华力相结合, 断口呈现出“台阶式”的解理, 表现为脆性的穿晶断裂^[15] ...

2012

2.821

0.0

Scripta Materialia. 2012, 67:null-null

Thermoelectric properties of hydrothermally synthesized Bi₂Te_3-xSe_x nanocrystals

... 10⁵S/m, 这与文献报道的Bi₂Te₃基体电导率随Se掺杂量增加而降低的趋势相似^[16] ...

... 45在该温度下的Seebeck系数^[16] ...

2005

1.846

0.0

Materials Science and Engineering: B. 2005, 117(3):null-null

Fabrication and thermoelectric performance of textured n-type Bi₂(Te, Se)₃ by spark plasma sintering

... 但Se掺杂为浅能级掺杂, 当测量温度升高到一定程度时, 杂质能级即可电离为导带电子和价带空穴, 成为本征半导体^[17] ...