硅酸盐学报

热挤压工艺对Bi₂Te_2.7Se_0.3材料热电性能和力学性能的影响

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李泉 ¹^,² , 邢通 ² , 李小亚 ² , 仇鹏飞 ² , 史迅 ²

硅酸盐学报 | 研究论文 2024,52(10): 3243-3251

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硅酸盐学报 |研究论文 2024 , 52 (10) : 3243 -3251

热挤压工艺对Bi₂Te_2.7Se_0.3材料热电性能和力学性能的影响

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李泉¹^,², 邢通², 李小亚², 仇鹏飞², 史迅²

作者信息

^1．上海理工大学材料与化学学院，上海 200093

^2．中国科学院上海硅酸盐研究所，高性能陶瓷和超微结构国家重点实验室，上海 200050

通讯作者:

邢通（1993—），女，博士，副研究员；

史迅（1976—），男，博士，研究员。

作者简介:

李泉（2000—），男，硕士研究生。

Effect of Hot Extrusion Processes on the Thermoelectric and Mechanical Properties of Bi₂Te_2.7Se_0.3 Materials

Quan LI¹^,², Tong XING², Xiaoya LI², Pengfei QIU², Xun SHI²

Affiliations

^1.School of Materials and Chemistry, University of Shanghai for Science and Technology, Shanghai 200093, China

^2.State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences, Shanghai 200050, China

Corresponding Author:

XING Tong (1993-), female, Ph.D., Associate Professor; E-mail: xingtong@mail.sic.ac.cn;

SHI Xun (1976-), male, Ph.D., Professor. xshi@mail.sic.ac.cn

LI Quan (2000-), male, Masteral candidate. E-mail: Lismarck@163.com

出版时间: 2024-10-20 doi: 10.14062/j.issn.0454-5648.20240245

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摘要

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碲化铋（Bi₂Te₃）基化合物作为室温附近性能最优异的热电材料，在热电制冷及发电技术中已获得广泛商业化应用。目前商业化生产的Bi₂Te₃基热电材料主要采用区熔法制备，虽然具有优异的热电性能，但材料容易解理，力学性能较差，无法满足微型热电器件的加工需求。本工作探索最佳热挤压工艺参数，采用热挤压技术在不同工艺条件下制备了n型Bi₂Te_2.7Se_0.3热电材料样品，并对样品进行物相分析、热电性能以及力学性能表征。结果表明，在确定的挤压比以及挤压速率下，提高挤压温度有利于减少样品裂纹，而过快的挤压速率则会导致样品断裂，最佳工艺参数为挤压温度400 ℃以及挤压速率0.05 mm/s。采用最佳工艺参数在不同工艺条件下制备的n型Bi₂Te_2.7Se_0.3样品中，通过放电等离子烧结结合热挤压所制备的样品热电性能最高，在400 K时zT值可达到0.83，并且其力学性能显著提升，维氏硬度可达602.5 N/mm²，为区熔Bi₂Te_2.7Se_0.3材料的2倍。Bi₂Te_2.7Se_0.3材料的机械加工性能也随之提升，采用封装切割工艺可以加工出最小尺寸达到147 μm的微型热电粒子，为后续Bi₂Te₃基微型热电器件的加工制备提供了材料基础。

关键词

热电材料 / 碲化铋 / 热挤压 / 热电性能 / 力学性能

Abstract

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Introduction

Bi₂Te₃-based alloys are the most well-known thermoelectric materials for room-temperature applications. The existing Bi₂Te₃-based thermoelectric materials produced commercially are prepared by a zone melting method, resulting in highly oriented materials with high thermoelectric properties. However, the ingots produced by the zone melting method are prone to disintegration due to the weak van der Waals forces between the layers of Te atoms, leading to the poor mechanical properties and the proclivity for fracture during processing and practical applications. It is thus important to improve the mechanical properties and machinability of Bi₂Te₃-based materials with the excellent thermoelectric properties. This work was to prepare a n-type Bi₂Te_2.7Se_0.3 thermoelectric material via spark plasma sintering combined with hot extrusion (SPS+HE). The parameters affacting hot extrusion process and preparation of n-type Bi₂Te_2.7Se_0.3 materials under different process conditions were optimized, and the thermoelectric performance and mechanical properties were investigated. In addition, the machinability of the extruded Bi₂Te_2.7Se_0.3 material was also analyzed.

Methods

The commercial zone-melting crystal rods were pulverized and sintered via spark plasma sintering (SPS) at 350 ℃ and 20 MPa for 5 min. The ingot was then put into a hot extrusion mold, and treated at 390-550 ℃, extrusion speed of 0.05-0.50 mm/s, extrusion ratio of 9∶1, and extrusion angle of 30°. Under the determined hot extrusion parameters, n-type Bi₂Te_2.7Se_0.3 materials were prepared by different processes, i.e., the raw materials were ground for 1 h and then sintered by SPS and subsequent hot extrusion (HE); the raw materials were melted at 700 ℃ for 5 h and then cold-pressed (MT), and sintered by subsequent hot extrusion (HE); the raw materials were melted and cold-pressed, followed by annealing and hot extrusion (MT+AN+HE); and the raw materials were ground for 1.5 h and cold-pressed, followed by hot extrusion (BM+HE). The phase structure was analyzed by X-ray diffraction (XRD, D8 Advance, Bruker Co. Ltd., USA) at room temperature. The microstructure and fracture morphology were determined by scanning electron microscopy (SEM, Supra 55, ZEISS Co., Germany). The electrical conductivity and the Seebeck coefficient were measured by ZEM-3 (ULVAC Co. Ltd., Japan). The thermal diffusivity (λ) was measured by a laser flash method (LFA457, Netzsch Co., Germany). The thermal conductivity was calculated according to κ=λρC_p, where C_p was the heat capacity according to the Neumann-Kopp rule, and the density ρ was measured based on the Archimedes prinicple.

Results and discussion

The results show that n-type Bi₂Te_2.7Se_0.3 thermoelectric materials can be prepared under optimum process conditions (i.e., extrusion temperature of 400 ℃ and extrusion speed of 0.05 mm/s). The XRD patterns of all the hot-extruded samples agree well with a rhombohedral structure (JCPDS 50-0954) of Bi₂Te_2.7Se_0.3. No impurity peaks appear. The SEM images reveal that Bi, Te, and Se are homogeneously distributed in the materials without any impurity phases. The electrical conductivity σ of all the samples decreases with increasing temperature, having a metallic conduction behavior. The σ of the MT+AN+HE sample is the maximum value of 1.4×10⁵ S/m. All the samples have negative Seebeck coefficients S, indicating that electrons are the major charge carriers. The S of the SPS+HE sample is the maximum value of 191.0 μV/K. At 300 K, the SPS+HE sample has the maximum power factor PF of 37.0 μW/(cm·K²). However, the PF of the material gradually decreases with the increase of temperature, which is consistent with the change of electrical conductivity and Seebeck coefficient due to the intrinsic excitation. The lattice thermal conductivity of MT+HE sample is the minimum value (i.e., 0.9 W·m^-1·K^-1). The maximum zT value reaches 0.83 at 400 K for SPS+HE sample and its Vickers hardness is 602.5 N/mm², which is twice greater than that of the zone-melting sample. This is mainly due to the dynamic recrystallization process of grain refinement during the hot extrusion process. The machinability of the extruded Bi₂Te_2.7Se_0.3 material are improved. The thermoelectric micron-sized particles with a minimum size of 147 μm can be achieved, providing a promising material for the development of Bi₂Te₃-based thermoelectric micro-devices.

Conclusions

The optimal hot extrusion process parameters for n-type Bi₂Te_2.7Se_0.3 thermoelectric materials were obtained (i.e., extrusion ratio 9∶1, extrusion angle 30°, extrusion temperature 400 K and extrusion speed 0.05 mm/s). A series of n-type Bi₂Te_2.7Se_0.3 thermoelectric material samples were prepared via hot extrusion under the optimum process conditions. The Bi₂Te_2.7Se_0.3 sample prepared by SPS and sebsequent hot extrusion (SPS+HE) had the maximum zT value 0.83 at 400 K, and its mechanical properties were improved. The Vickers hardness of the SPS+HE sample could reach 602.5 N/mm², which was twice greater than that of the zone-melting Bi₂Te_2.7Se_0.3 material. In addition, the machining performance was also improved, and the thermoelectric micron-sized particles with the minimum size of 147 μm could be machined for the extruded Bi₂Te_2.7Se_0.3 sample, providing a promising material for the Bi₂Te₃-based thermoelectric micro-devices.

Key words

thermoelectric materials / bismuth telluride / hot extrusion / thermoelectric performance / mechanical property

引用本文

李泉, 邢通, 李小亚, 仇鹏飞, 史迅. 热挤压工艺对Bi₂Te_2.7Se_0.3材料热电性能和力学性能的影响. 硅酸盐学报, 2024 , 52 (10) : 3243 -3251 . DOI: 10.14062/j.issn.0454-5648.20240245

Quan LI, Tong XING, Xiaoya LI, Pengfei QIU, Xun SHI. Effect of Hot Extrusion Processes on the Thermoelectric and Mechanical Properties of Bi₂Te_2.7Se_0.3 Materials[J]. Journal of the Chinese Ceramic Society, 2024 , 52 (10) : 3243 -3251 . DOI: 10.14062/j.issn.0454-5648.20240245

基金

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国家重点研发计划(2023YFB3809400)
国家自然科学基金(52202330)

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2024年第52卷第10期

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文章信息

doi: 10.14062/j.issn.0454-5648.20240245

接收时间：2024-03-28
首发时间：2026-10-22
出版时间：2024-10-20

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收稿日期：2024-03-28
修回日期：2024-04-15

基金

国家重点研发计划(2023YFB3809400)

国家自然科学基金(52202330)

作者信息

^1．上海理工大学材料与化学学院，上海 200093

^2．中国科学院上海硅酸盐研究所，高性能陶瓷和超微结构国家重点实验室，上海 200050

通讯作者:

邢通（1993—），女，博士，副研究员；

史迅（1976—），男，博士，研究员。

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https://castjournals.cast.org.cn/joweb/gsyxb/CN/10.14062/j.issn.0454-5648.20240245

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2种不同金属材料的力学参数

科 Family	属数 Number of genus	种数 Number of species	占总种数比例 Percentage of total species (%)	属 Genus	种数 Number of species	占总种数比例 Percentage of total species (%)
鹅膏菌科Amanitaceae	2	11	5.26	鹅膏菌属 Amanita	10	4.78
小菇科 Mycenaceae	2	12	5.74	丝盖伞属 Inocybe	5	2.39
多孔菌科 Polyporaceae	8	14	6.70	蜡蘑属 Laccaria	5	2.39
红菇科 Russulaceae	3	23	11.00	小皮伞属 Marasmius	6	2.87
				小菇属 Mycena	11	5.26
				光柄菇属 Pluteus	5	2.39
				红菇属 Russula	17	8.13
				栓菌属 Trametes	5	2.39

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