阅读说明：本技术 一种快速制备高取向高功率因子的Bi2Te3基热电材料的方法 (Bi for rapidly preparing high-orientation high-power factor2Te3Method for producing thermoelectric material ) 是由 唐新峰 张政楷 苏贤礼 曹宇 于 2020-07-30 设计创作，主要内容包括：一种快速制备高取向高功率因子的p型或n型Bi<Sub>2</Sub>Te<Sub>3</Sub>基热电材料方法,属于能源材料技术领域。该方法分为化合物制备、成型、热锻三个部分,首先将高纯Bi,Sb,Te,Se,S按照化学计量比称量,通过自蔓延合成或热爆合成的方式超快速制备得到p型或n型Bi<Sub>2</Sub>Te<Sub>3</Sub>基热电材料；然后将p型或n型Bi<Sub>2</Sub>Te<Sub>3</Sub>基热电材料研磨筛分,选取合适粒径材料进行放电等离子烧结,获得致密块体材料；将致密块体材料通过放电等离子烧结技术进行热锻,得到高取向性、高功率因子的p型或n型的Bi<Sub>2</Sub>Te<Sub>3</Sub>基热电材料。本发明通过热爆及自蔓延燃烧合成技术可以大大减少原料制备所需时间,以及研磨达到所需粒径时间,结合放电等离子烧结技术进行热锻,可以有效控制晶粒长大,时间短,材料具有高取向性、高功率因子。(P-type or n-type Bi for rapidly preparing high-orientation high-power factor 2 Te 3 A method for preparing a base thermoelectric material belongs to the technical field of energy materials. The method comprises three parts of compound preparation, forming and hot forging, firstly, high-purity Bi, Sb, Te, Se and S are weighed according to stoichiometric ratio, and p-type or n-type Bi is prepared by a self-propagating synthesis or thermal explosion synthesis manner in an ultra-fast way 2 Te 3 A base thermoelectric material; then adding p-type or n-type Bi 2 Te 3 Grinding and screening the base thermoelectric material, selecting the material with proper grain diameter and placingPerforming electric plasma sintering to obtain a compact block material; hot forging the compact block material by spark plasma sintering technology to obtain p-type or n-type Bi with high orientation and high power factor 2 Te 3 A base thermoelectric material. The invention can greatly reduce the time required by raw material preparation and the time required by grinding to reach the required grain diameter by the thermal explosion and self-propagating combustion synthesis technology, and can effectively control the grain growth by combining the discharge plasma sintering technology for hot forging, the time is short, and the material has high orientation and high power factor.)

1. Bi for rapidly preparing high-orientation high-power factor₂Te₃The method for preparing the base thermoelectric material is characterized in that a simple substance is used as an initial raw material, and the required Bi is prepared by thermal explosion synthesis and self-propagating combustion₂Te₃A base thermoelectric material; then grinding to obtain powder, and sintering by utilizing discharge plasma to obtain a block material; then the block material is hot forged according to a certain extrusion ratio to obtain Bi with high orientation and high power factor₂Te₃A base thermoelectric material.

2. The method of claim 1 for rapidly preparing Bi with high orientation and high power factor₂Te₃Method for producing a thermoelectric material, characterized in that said Bi₂Te₃The base thermoelectric material is p-type or n-type; p-type Bi₂Te₃The chemical composition of the base thermoelectric material is Bi_xSb_{2- x}Te₃x is 0.45 to 0.55, and n-type Bi₂Te₃The chemical composition of the base thermoelectric material is Bi₂Te_ySe_3-y-zS_z，y＝2.6～2.8，z＝0～0.1。

3. The method of claim 1 for rapidly preparing Bi with high orientation and high power factor₂Te₃A method for producing a thermoelectric material, characterized in that the elementary substance has a purity of more than 99%; according to Bi₂Te₃The element contained in the base thermoelectric material is selected as a simple substance as a starting material.

4. The method of claim 1 for rapidly preparing Bi with high orientation and high power factor₂Te₃The method for preparing the base thermoelectric material is characterized in that the temperature of the thermal explosion synthesis is 400-600 ℃, and the time is 30 s-5 min.

5. The method of claim 1 for rapidly preparing Bi with high orientation and high power factor₂Te₃A method for producing a thermoelectric material, characterized in that the particle size of the powder obtained by grinding is 200 to 400 mesh.

6. The method of claim 1 for rapidly preparing Bi with high orientation and high power factor₂Te₃The method for preparing the base thermoelectric material is characterized in that the discharge plasma sintering pressure is 10-60 MPa, the sintering temperature is 300-550 ℃, the temperature rising speed is 50-150 ℃/min, and the heat preservation time is 4-10 min.

7. The method of claim 1 for rapidly preparing Bi with high orientation and high power factor₂Te₃The method for preparing the base thermoelectric material is characterized in that hot forging is realized by adopting a spark plasma sintering technology, and the hot forging extrusion ratio is 1: 2-1: 16; during hot forging, the initial pressure of spark plasma sintering is 10-30 MPa, the sintering temperature is 300-550 ℃, the temperature rising speed is 50-150 ℃/min, the pressure is increased to 30-120 MPa within 1-5 min, and the temperature is kept for 4-10 min.

8. According to claimThe method for rapidly preparing Bi with high orientation and high power factor as described in claim 1₂Te₃The method for producing the thermoelectric material is characterized in that the number of hot forging is 1-4.

9. The method of claim 1 for rapidly preparing Bi with high orientation and high power factor₂Te₃A method of forming a thermoelectric material, comprising the steps of:

(1) according to p-type Bi_xSb_2-xTe₃(x is 0.45 to 0.55) and n-type Bi₂Te_ySe_3-y-zS_z(y is 2.6-2.8, z is 0-0.1) respectively, weighing simple substances as initial raw materials according to the stoichiometric ratio of the elements, mixing, tabletting, vacuum sealing in a glass tube, and performing thermal explosion synthesis or self-propagating combustion synthesis to obtain p-type or n-type Bi₂Te₃A base thermoelectric material;

(2) mixing P-type or n-type Bi₂Te₃The base thermoelectric material is subjected to hand milling or ball milling to obtain powder with a smaller particle size, and the powder with a particle size of 200-400 meshes is screened in a screening mode for use;

(3) filling the powder sieved in the step (2) with 200-400 meshes into a mold for spark plasma sintering, wherein the pressure is 10-60 MPa, the temperature is 300-550 ℃, the temperature rise speed is 50-150 ℃/min, and the temperature is kept for 4-10 min to obtain a sintered block material;

(4) putting the block material obtained in the step (3) into a die with a larger diameter, wherein the extrusion ratio is 1: 2-1: 16, carrying out spark plasma sintering at the initial pressure of 10-30 MPa, the sintering temperature of 300-550 ℃, the heating rate of 50-150 ℃/min, increasing the pressure to 30-120 MPa in 1-5 min, and carrying out heat preservation for 4-10 min to obtain the p-type or n-type Bi with high orientation and high power factor₂Te₃A base thermoelectric material.

10. The method of claim 1 for rapidly preparing Bi with high orientation and high power factor₂Te₃A method for manufacturing a thermoelectric material, characterized in that the step (4) is repeated several times.

Technical Field

The invention belongs to the technical field of energy materials, and provides a method for rapidly preparing p-type or n-type Bi with high-orientation high power factors₂Te₃Methods of base thermoelectric materials.

Technical Field

The thermoelectric material is used as a novel clean renewable energy material, can realize direct conversion of heat energy and electric energy, has the excellent characteristics of no pollution, no loss, high reliability and the like, and is expected to greatly improve the energy utilization rate and relieve the environmental pollution. Among them, the bismuth telluride-based compound is a thermoelectric material which is currently commercially used and has the best performance in the vicinity of room temperature. The bismuth telluride-based compound is a trigonal system, belongs to a space group R-3m, and is formed by stacking hexagonal layered structures. Bi₂Te₃The compound having a crystallographic c-axis orientation of-Te⁽¹⁾—Bi—Te⁽²⁾—Bi—Te⁽¹⁾The five atomic layers are alternately arranged repeatedly, and Te has two different occupation positions, wherein Te⁽¹⁾-Bi is bonded by ionic and covalent bonds, Te⁽²⁾-Bi is covalently bonded, and Te⁽¹⁾-Te⁽¹⁾The layers are bonded by van der Waals force, and the weaker bonding causes Bi₂Te₃Crystal of the compound in Te⁽¹⁾-Te⁽¹⁾Easy slippage or cleavage between atomic planes along basal planes, resulting in Bi₂Te₃The mechanical properties of compound single crystals are poor.

Currently, ingot materials prepared by zone melting method are mainly used for commercial devices of bismuth telluride-based compounds [ D. -B.Hyun, TS Oh, JS Hwang, et al, script Mater.40(1998)49]、Bridgman[O,Yamashita,S,Tomiyoshi'K.Makita,J.Appl.Phys.93(2003)368]Preparation of highly oriented, large-grained p, n-type Bi₂Te₃Based on thermoelectric materials, however, due to their Te⁽¹⁾-Te⁽¹⁾Bi of the type bonded between layers by van der Waals forces₂Te₃The base material has high conductivity and thermoelectric property, but has poor mechanical property, extremely high rejection rate when producing small and micro thermoelectric particles, and even can not be obtained by processing.

In order to improve the mechanical property and the thermoelectric property of the material, the structural nanocrystallization, the defect regulation, the thermal deformation method and the like are generally adopted to reduce the thermal conductivity and improve the power factor of the material, and Bi with higher ZT value is prepared at the laboratory level at present₂Te₃The base material is basically mature, and the material with ZT value higher than 1.4 can be prepared by a chemical method, a mechanical alloy method and a melt spinning method. However, the material prepared by the structural nanocrystallization has low thermal conductivity and greatly reduced electrical conductivity, so that the internal resistance of the thermoelectric device is remarkably increased, and the performance of the thermoelectric device is influenced finally. Therefore, a fast and efficient method for preparing a thermoelectric material with high mechanical properties and high electrical conductivity is urgently needed.

Disclosure of Invention

The technical problem to be solved by the invention is to provide a method for rapidly preparing Bi aiming at the defects of the prior art₂Te₃Method for preparing p-type or n-type Bi suitable for preparing device with high orientation, high conductivity and high power factor based on thermoelectric material₂Te₃A base thermoelectric material.

The technical scheme adopted by the invention for solving the problems is as follows:

p-type or n-type Bi for rapidly preparing high-orientation high-power factor₂Te₃The method for preparing p-type or n-type Bi required by using high-purity simple substance as initial raw material through thermal explosion synthesis and self-propagating combustion₂Te₃A base thermoelectric material; the p-type or n-type Bi₂Te₃The base thermoelectric material is ground by a ball grinding method or a manual grinding method to obtain powder with required grain diameter, and the powder is sintered by discharge plasma to obtain a compact block material; then selecting different extrusion ratios for the compact block material to be subjected to hot forging to obtain p-type or n-type Bi with high orientation and high power factor₂Te₃A base thermoelectric material.

According to the scheme, the p-type Bi₂Te₃The chemical composition of the base thermoelectric material is Bi_xSb_2-xTe₃(x is 0.45 to 0.55) and n-type Bi₂Te₃The chemical composition of the base thermoelectric material is Bi₂Te_ySe_3-y-zS_z(y＝2.6～2.8，z＝0～0.1)。

According to the scheme, the purity of the high-purity simple substance is more than 99 percent; according to p-type or n-type Bi₂Te₃The elements contained in the base thermoelectric material are selected from high-purity simple substances as initial raw materials, and are mainly selected from Bi, Sb, Te, Se, S and the like.

According to the scheme, the temperature of the thermal explosion synthesis is 400-600 ℃, and the time is 30 s-5 min.

According to the scheme, the powder with the required particle size is preferably 200-400 meshes.

According to the scheme, when the compact block material is prepared by spark plasma sintering, the spark plasma sintering pressure is 10-60 MPa, the sintering temperature is 300-550 ℃, the temperature rising speed is 50-150 ℃/min, and the temperature is kept for 4-10 min.

According to the scheme, hot forging is carried out by adopting a spark plasma sintering technology, and the hot forging extrusion ratio is 1: 2-1: 16; the number of hot forging is generally 1 to 4. During hot forging, the initial pressure of spark plasma sintering is 10-30 MPa, the sintering temperature is 300-550 ℃, the temperature rising speed is 50-150 ℃/min, the pressure is increased to 30-120 MPa within 1-5 min, and the temperature is kept for 4-10 min.

Specifically, the rapid preparation method of the high-orientation high-power-factor p-type or n-type Bi₂Te₃A method of fabricating a thermoelectric material, comprising the steps of:

(1) high-purity simple substances Bi, Sb, Te, Se and S are used as initial raw materials according to p type Bi_xSb_2-xTe₃(x is 0.45 to 0.55) and n-type Bi₂Te_ySe_3-y-zS_z(y is 2.6-2.8, z is 0-0.1) weighing simple substances according to the stoichiometric ratio of the elements, tabletting, sealing in a glass tube in vacuum, and performing thermal explosion synthesis or self-propagating combustion synthesis to obtain p-type or n-type Bi₂Te₃A base thermoelectric material;

(2) mixing P-type or n-type Bi₂Te₃The base thermoelectric material is ground by hand or ball milling to obtain powder with smaller particle size for 10-30 min, and the powder with 200-400 meshes is screened by a screening method for use;

(3) filling the powder obtained in the step (2) into a graphite or stainless steel mold with the diameter of 12-20 mm, wherein the discharge plasma sintering pressure is 10-60 MPa, the sintering temperature is 300-550 ℃, the heating rate is 50-150 ℃/min, and the temperature is kept for 4-10 min to obtain a sintered block material;

(4) putting the block material obtained in the step (3) into a graphite or stainless steel mold with a larger diameter, wherein the extrusion ratio is 1: 2-1: 16, the initial pressure of the spark plasma sintering is 10-30 MPa, the sintering temperature is 300-550 ℃, the temperature rising speed is 50-150 ℃/min, the pressure is increased to 30-120 MPa in 1-5 min, and the temperature is kept for 4-10 min to obtain the high-orientation high-power factor p-type or n-type Bi₂Te₃A base thermoelectric material.

According to the scheme, the step (4) is repeated to obtain the block material with larger extrusion ratio and stronger orientation, and the step is repeated for 1-3 times generally.

Compared with the prior art, the invention has the beneficial effects that:

the invention firstly synthesizes p-type or n-type Bi through thermal explosion or self-propagating combustion₂Te₃The thermoelectric material precursor can store a nano phase, inhibit the growth of crystal grains and obviously improve the mechanical property compared with a commercially used zone-melting bismuth telluride material; meanwhile, the material is easier to be ground due to the micro-nano structure in the material, and the raw material with fine grains can be obtained in a very short time for sintering through the subsequent manual grinding or ball milling process; then sintering is carried out through the SPS technology, a block material with excellent mechanical property can be prepared, and hot forging is carried out again through the SPS technology for multiple times, so that the hot forging time is greatly shortened compared with that of a common hot pressing device. The grain rearrangement and the slippage in the hot forging process enhance the orientation of the material, so that the conductivity of the material is increased, and the extrusion ratio with large change can better achieve the aim, so that the proper extrusion ratio is selected for hot forging to obtain the extremely high Power Factor (PF) and meet the requirements of thermoelectric devices. The invention can obtain p-type or n-type Bi which has excellent mechanical property, high orientation, high conductivity and high power factor and is suitable for preparing devices₂Te₃A base thermoelectric material. Compared with the traditional zone-melting single crystal bismuth telluride material,the invention introduces a multi-scale structure through a rapid non-equilibrium preparation method, and obviously improves p-type or n-type Bi₂Te₃Based on the mechanical properties of the thermoelectric material. Compared with the preparation process of the polycrystalline bismuth telluride material which is researched more at present, the preparation method disclosed by the invention has the advantages that the preparation time is greatly shortened, the electrical property is improved through the hot forging process, and the method is more suitable for the requirements of actual thermoelectric devices.

Drawings

FIG. 1 is an X-ray diffraction pattern of the example 1-SPS sample, the example 1-hot forged sample, and the example 3-hot forged sample.

FIG. 2 shows the temperature dependence of the electrical conductance of the example 1-SPS sample, the example 1-Hot forged sample, and the example 3-Hot forged sample.

FIG. 3 is a graph showing the Seebeck coefficient as a function of temperature for the example 1-SPS samples, the example 1-hot forged samples, and the example 3-hot forged samples.

FIG. 4 shows the Power Factor (PF) as a function of temperature for the samples of example 1-SPS, example 1-Hot forged, and example 3-Hot forged samples.

Detailed Description

In order to better understand the present invention, the following examples are further provided to illustrate the content of the present invention, but the present invention is not limited to the following examples.

In the present invention, the extrusion ratio refers to the ratio of the surface area of the sample before and after hot forging, for example, the extrusion ratio of 1: 2 means that the area of the upper surface of the sample after hot forging was 2 times as large as that before hot forging and the height was 1/2 before hot forging.

In the following examples, samples before and after hot forging were subjected to surface polishing with sandpaper, and then to a thermoelectric performance test, which mainly included: conductivity σ, seebeck coefficient α. Then passing the power factor PF ═ alpha²Sigma is used for representing the electrical property of the material, and due to the existence of internal resistance in the thermoelectric device, the higher conductivity can improve the conversion efficiency of the device.

In the following examples, the purity of elementary Bi, Sb, Te, Se, S is more than 99%.