阅读说明：本技术 一种碲化铋基热电材料及其制备方法 (Bismuth telluride-based thermoelectric material and preparation method thereof ) 是由 王泓翔 熊成龙 罗国强 胡皓阳 雅克·纪尧姆·努丹 蒋俊 于 2019-01-14 设计创作，主要内容包括：本申请公开了一种碲化铋基热电材料及其制备方法。碲化铋基热电材料选自具有如式Ⅰ所示化学式的化合物中的至少一种。制备方法包括a)将含有Bi单质、Te单质、Sb单质或Se单质的混合物料加入储料管中、封管,然后依次进行熔炼、区域熔炼,得到区域铸锭；b)将所述区域铸锭进行热压织构化,即可得到所述碲化铋基热电材料。本申请提供的制备方法,可以有效提升多晶材料的取向性,调控其热电输运特性,优化其热电性能。(The application discloses a bismuth telluride-based thermoelectric material and a preparation method thereof. The bismuth telluride-based thermoelectric material is selected from at least one compound with a chemical formula shown as a formula I. The preparation method comprises a) adding a mixed material containing a Bi simple substance, a Te simple substance, a Sb simple substance or a Se simple substance into a storage pipe, sealing the pipe, and then sequentially carrying out smelting and zone smelting to obtain a zone ingot; b) and carrying out hot-pressing texturing on the region cast ingot to obtain the bismuth telluride-based thermoelectric material. The preparation method provided by the application can effectively improve the orientation of the polycrystalline material, regulate and control the thermoelectric transport property of the polycrystalline material, and optimize the thermoelectric property of the polycrystalline material.)

1. The bismuth telluride-based thermoelectric material is characterized in that the bismuth telluride contains doping elements, and the doping elements are selected from any one of antimony and selenium.

2. The bismuth telluride-based thermoelectric material according to claim 1, further comprising a metal modification element;

wherein the metal modification element is at least one selected from L i, Na, K, Cu, Ag, Fe, Zn, Mn and Mg.

3. The bismuth telluride-based thermoelectric material according to claim 2, wherein the bismuth telluride-based thermoelectric material is at least one selected from the group consisting of a compound having a chemical formula shown in formula I and a compound having a chemical formula shown in formula II;

Bi_2-x1Sb_x1Te₃M_y1

formula I

Bi₂Te_3-x2Se_x2M_y2

Formula II

M is selected from at least one of L i, Na, K, Cu, Ag, Fe, Zn, Mn and Mg;

wherein x1 is more than 0 and less than 1, x2 is more than 0 and less than 1, y1 is more than or equal to 0 and less than or equal to 1, and y2 is more than or equal to 0 and less than or equal to 1;

x1, x2, y1, and y2 are independently selected.

4. The method for producing a bismuth telluride-based thermoelectric material as set forth in claim 1, characterized by comprising:

a) adding a mixed material containing a Bi simple substance, a Te simple substance, a Sb simple substance or a Se simple substance into a storage pipe, sealing the pipe, and then sequentially carrying out smelting and zone smelting to obtain a zone ingot;

b) and carrying out hot-pressing texturing on the region cast ingot to obtain the bismuth telluride-based thermoelectric material.

5. The preparation method according to claim 4, wherein the melting temperature in the step a) is 650-900 ℃, and the melting swing time is 15-600 min;

the zone melting temperature is 600-900 ℃, the length of a melting temperature zone is 3-7 cm, and the moving speed of the melting temperature zone is 0.5-50 mm/h.

6. The method of claim 4, wherein the hot press texturing in step b) comprises sintering I and sintering II;

the sintering conditions of the sintering I are as follows: sintering temperature is 360-560 ℃, and sintering time is 3-60 min;

the sintering conditions of the sintering II are as follows: the sintering temperature is 360-560 ℃, the sintering time is 3-60 min, and the sintering pressure is 30-100 MPa.

7. The method of claim 6, further comprising pre-treating the zone ingot prior to hot press texturing,

the pretreatment comprises the following steps: removing an oxide layer on the surface of the regional cast ingot, and then crushing, axially cold-pressing and forming, and cold isostatic pressing;

preferably, the removing the oxide layer on the surface of the regional cast ingot comprises scraping the oxide layer on the surface of the regional cast ingot in a glove box; alternatively, the first and second electrodes may be,

soaking in hydrofluoric acid solution to remove the oxide layer on the surface of the regional cast ingot;

preferably, the pulverizing comprises: grinding and crushing under the condition of inert gas for 0.5-60 min for 1-5 times;

preferably, the conditions of the axial cold press forming are: the molding pressure is 5-60 MPa, and the molding time is 0.5-30 min;

the cold isostatic pressing conditions are as follows: the molding pressure is 5-200 MPa, and the molding time is 1-30 min.

8. The preparation method of claim 6, further comprising polishing the surfaces of the plurality of bismuth telluride-based thermoelectric materials, sequentially placing the polished surfaces into a mold, and repeating the step b), thereby obtaining the bismuth telluride-based thermoelectric material meeting the thickness requirement.

9. The method according to claim 4, wherein the mixture further comprises M.

10. The method of manufacturing according to claim 4, wherein the method comprises:

step 1: placing a mixed material containing elementary substances of elements in the bismuth telluride-based thermoelectric material in a container, and sealing under vacuum of less than 10 MPa;

step 2: smelting, melting at 650-900 ℃ and swinging for 15-600 min;

and step 3: zone melting is carried out, wherein the temperature is 600-900 ℃, the length of a melting temperature zone is 3-7 cm, and the moving speed of the melting temperature zone is 0.5-50 mm/h;

and 4, step 4: crushing the ingot, namely scraping an oxide layer on the surface of the zone-melting ingot obtained in the step 3, or soaking the ingot in hydrofluoric acid for 1-30 minutes to remove the oxide layer; crushing, wherein the grinding time is 0.5-60 minutes, the grinding times are 1-5 times, and the inert gas is used for protection;

and 5: cold-pressing the powder for molding, and keeping the pressure at 5-60 MPa for 0.5-30 min;

step 6: cold isostatic pressing, namely keeping the biscuit in the step 5 under the pressure of 5-200 MPa for 1-30 min to obtain a biscuit;

and 7: hot-pressing texturing, namely heating the sample obtained in the step 6 to 360-560 ℃ and preserving heat for 3-60 minutes; uniformly raising the temperature and the pressure to 30-100 MPa, and preserving the heat at 360-560 ℃ for 3-60 minutes; obtaining the bismuth telluride-based thermoelectric material;

preferably, the method further comprises:

and 8: and 7, polishing the bismuth telluride-based thermoelectric material obtained in the step 7, and then superposing the polished bismuth telluride-based thermoelectric material into a large sample to repeat the step 7.

Technical Field

The application relates to a bismuth telluride-based thermoelectric material, belonging to the technical field of thermoelectric materials.

Background

Fossil fuel depletion is almost eliminated and the demand for green energy is increasing. In recent years, attention has been paid to the field of thermoelectric technology, and thermoelectric materials have been widely studied. The thermoelectric material is a functional material capable of realizing direct interconversion of heat energy and electric energy, comprises two physical effects of Seebeck and Peltier, and derives two applications of thermoelectric power generation and thermoelectric refrigeration. The thermoelectric power generation can utilize low-quality heat sources such as body heat and waste heat to generate power. Thermoelectric refrigeration can realize the functions of quick lifting and temperature control and accurate temperature control. Therefore, it becomes important how to improve the peak performance of the material and the thermal stability of the performance.

The performance of thermoelectric materials is measured by a dimensionless figure of merit ZT,

ZT＝σS²T/(κlat+κele)，

where σ, S, T, κ lat, and κ ele are the electrical conductivity, seebeck coefficient, absolute temperature, lattice thermal conductivity, and electronic thermal conductivity, respectively. The mutual coupling between these thermoelectric transport parameters affects each other, which makes the improvement of thermoelectric performance challenging.

The variety of thermoelectric materials is wide, and the bismuth telluride-based thermoelectric material attracts wide attention due to excellent performance and practical application value. Bismuth telluride is a trigonal system, and internal crystal lattices are arranged in a layered mode along the c axis, so that the bismuth telluride has strong anisotropy, and the optimal thermoelectric property is obtained along the direction in the layer. However, the material is easily dissociated in the direction of the sheet due to the layered structure, so that the material has poor mechanical properties and is not easy to process. The polycrystalline bismuth telluride material prepared by the hot-pressing sintering process can effectively improve the mechanical property thereof, so that how to optimize the hot-pressing sintering process to improve the property of the polycrystalline bismuth telluride material becomes more important.

Disclosure of Invention

According to an aspect of the present application, there is provided a bismuth telluride-based thermoelectric material having excellent thermoelectric properties.

The bismuth telluride-based thermoelectric material is characterized in that the bismuth telluride contains doping elements, and the doping elements are selected from any one of antimony and selenium.

Optionally, the material also comprises a metal modification element, wherein the metal modification element is selected from at least one of L i, Na, K, Cu, Ag, Fe, Zn, Mn and Mg.

Optionally, at least one compound selected from the group consisting of a compound having a formula shown in formula I and a compound having a formula shown in formula II;

Bi_2-x1Sb_x1Te₃M_y1

formula I

Bi₂Te_3-x2Se_x2M_y2

Formula II

M is selected from at least one of L i, Na, K, Cu, Ag, Fe, Zn, Mn and Mg;

wherein x1 is more than 0 and less than 1, x2 is more than 0 and less than 1, y1 is more than or equal to 0 and less than or equal to 1, and y2 is more than or equal to 0 and less than or equal to 1;

x1, x2, y1 and y2 independently take values

According to another aspect of the application, the preparation method of the bismuth telluride-based thermoelectric material can effectively improve the orientation of the polycrystalline material, regulate and control the thermoelectric transport property of the polycrystalline material, and optimize the thermoelectric performance of the polycrystalline material.

The preparation method of the bismuth telluride-based thermoelectric material comprises the following steps:

a) adding a mixed material containing a Bi simple substance, a Te simple substance, a Sb simple substance or a Se simple substance into a storage pipe, sealing the pipe, and then sequentially carrying out smelting and zone smelting to obtain a zone ingot;

b) and carrying out hot-pressing texturing on the region cast ingot to obtain the bismuth telluride-based thermoelectric material.

Optionally, the smelting temperature in the step a) is 650-900 ℃, and the smelting swinging time is 15-600 min;

the zone melting temperature is 600-900 ℃, the length of a melting temperature zone is 3-7 cm, and the moving speed of the melting temperature zone is 0.5-50 mm/h.

Specifically, the smelting is carried out for 15-600 minutes at the smelting temperature of 650-900 ℃, and then zone smelting is carried out at the speed of 0.5-50 mm/h at the temperature of 600-900 ℃.

Optionally, the hot-pressing texturing in step b) comprises sintering I and sintering II;

the sintering conditions of the sintering I are as follows: sintering temperature is 360-560 ℃, and sintering time is 3-60 min;

the sintering conditions of the sintering II are as follows: the sintering temperature is 360-560 ℃, the sintering time is 3-60 min, and the sintering pressure is 30-100 MPa.

Specifically, the obtained zone ingot is put into a metal or graphite mold under vacuum or inert atmosphere, and hot-pressing texturing is carried out.

Heating the mold with the regional cast ingot to 360-560 ℃, preserving heat for 3-60 minutes, uniformly raising the temperature and boosting the pressure to 30-100 MPa and 360-560 ℃, preserving heat for 3-60 minutes, and finally quickly releasing pressure and cooling.

The heating rate in the sintering I is 40-60 ℃/h, and the heating rate in the sintering II is 40-60 ℃/h.

In the sintering I, the upper limit of the sintering temperature is selected from 430 ℃ and 560 ℃; the lower limit of the sintering temperature is selected from 360 ℃ and 430 ℃.

In the sintering II, the upper limit of the sintering temperature is selected from 500 ℃ and 560 ℃; the lower limit of the sintering temperature is selected from 360 ℃ and 500 ℃;

the upper limit of the sintering pressure is selected from 60MPa and 100MPa, and the lower limit of the sintering pressure is selected from 30MPa and 60 MPa;

the upper limit of the sintering time is selected from 20min and 60min, and the lower limit of the sintering time is selected from 3min and 20 min.

Optionally, the sintering ii in the hot-press texturing in step b) includes any one of hot-press sintering and plasma sintering.

In the present application, sintering ii in hot press texturing includes, but is not limited to, hot press sintering and spark plasma sintering.

Optionally, the area ingot is pretreated before hot-pressing texturing,

the pretreatment comprises the following steps: and removing an oxide layer on the surface of the regional cast ingot, and then crushing, axially cold-pressing and forming, and cold isostatic pressing and forming.

Preferably, the removing the oxide layer on the surface of the regional ingot comprises: scraping an oxide layer on the surface of the area cast ingot in a glove box; or soaking in hydrofluoric acid solution to remove the oxide layer on the surface of the ingot in the region.

Specifically, the oxide layer on the surface of the obtained zone-melting cast ingot is scraped in a glove box, or the oxide layer is removed by soaking the zone-melting cast ingot in hydrofluoric acid for 1-30 minutes.

Optionally, the comminuting comprises: and grinding and crushing under the condition of inert gas for 0.5-60 min for 1-5 times.

Specifically, crushing is carried out by using a stainless steel or agate grinding tank, wherein the grinding time is 0.5-60 minutes, the grinding times are 1-5 times, and the inert gas is used for protection.

The inert gas may be helium, argon, or the like.

Optionally, the conditions of the axial cold press forming are: the molding pressure is 5-60 MPa, and the molding time is 0.5-30 min; the cold isostatic pressing conditions are as follows: the molding pressure is 5-200 MPa, and the molding time is 1-30 min.

Specifically, the ingot casting powder obtained after crushing is placed into a stainless steel or graphite mold for cold pressing and cold isostatic pressing forming respectively, wherein the cold pressing pressure is 5-60 MPa, the time is 0.5-30 minutes, and the cold isostatic pressure is 5-200 MPa, and the time is 0.5-30 minutes.

In cold press forming, the upper limit of the forming pressure is selected from 20MPa and 60MPa, and the upper limit of the forming pressure is selected from 5MPa and 20 MPa.

In cold isostatic pressing, the upper limit of the molding pressure is selected from 100MPa and 200MPa, and the upper limit of the molding pressure is selected from 5MPa and 100 MPa.

Optionally, the method further comprises polishing the surfaces of the plurality of bismuth telluride-based thermoelectric materials, sequentially placing the plurality of bismuth telluride-based thermoelectric materials into a mold, and repeating the step b), so that the bismuth telluride-based thermoelectric material meeting the thickness requirement can be obtained.

Optionally, the mixed material further includes a simple substance M.

Specifically, the surfaces of the plurality of bismuth telluride-based thermoelectric materials obtained by the method can be polished and stacked to repeat the hot-pressing texturing process, so that a sample with a larger volume can be obtained.

In the application, a block sintering material with the components of BiSbTeM/BiTeSeM is prepared by utilizing a zone melting process, an ingot casting crushing process, a powder cold pressing process, a hot pressing texturing process and the like.

A specific preparation process is introduced below, and the process flow is as follows:

step 1: weighing materials, weighing according to the chemical composition in the formula I, and putting the materials into a clean quartz glass tube; the tube was sealed under vacuum <10 MPa.

Step 2: smelting, melting at 650-900 ℃, swinging for 0.5-6 h, and naturally cooling or placing in an ice water bath for quenching.

And step 3: zone melting is carried out at the temperature of 600-900 ℃, the length of a melting temperature zone is 3-7 cm, and the moving speed of the melting temperature zone is 0.5-50 mm/h.

Step 4, crushing the cast ingot, scraping the oxide layer on the surface of the zone-melting cast ingot obtained in the step 3 in a glove box, or soaking the cast ingot in hydrofluoric acid for 1-30 minutes to remove the oxide layer; and (3) crushing by using a stainless steel or agate grinding tank, wherein the grinding time is 0.5-60 minutes, the grinding times are 1-5 times, and the inert gas is used for protection.

And 5: and (3) performing cold press molding on the powder, and pressing for 0.5-30 min under the pressure of 5-60 MPa by using a metal/graphite mold.

Step 6: and (5) carrying out cold isostatic pressing, namely pressing the biscuit in the step (5) for 1-30 min under the pressure of 5-200 MPa to obtain the biscuit.

And 7: hot-pressing texturing, namely putting the sample obtained in the step 6 into a metal/graphite mold, heating to 360-560 ℃ and preserving heat for 3-60 minutes; and then uniformly raising the temperature and the pressure to 30-100 MPa, preserving the heat for 3-60 minutes at 360-560 ℃, and finally quickly releasing the pressure and cooling to obtain a sample.

Preferably, the method further comprises the step 8: and 7, grinding the small sample obtained in the step 7, and then overlapping the small sample into a large sample to repeat the step 7.

And step 9: samples were cut into 3mm by 10mm strips and 2mm by 10mm sheets for electrothermal transport performance testing.

The beneficial effects that this application can produce include:

the performance of the BiSbTeM/BiTeSeM polycrystalline material is optimized by utilizing the processes of zone melting, ingot casting crushing, powder cold pressing, powder cooling and the like and the hot-pressing texturing process, and the bismuth telluride-based thermoelectric material prepared by the process has the characteristics of high density, good crystal grain orientation and excellent performance.

Drawings

Fig. 1 is a flowchart of a method for preparing a bismuth telluride-based thermoelectric material provided by the present application;

FIG. 2 is a plot of ZT peaks of samples to be tested.

Detailed Description

The present application will be described in detail with reference to examples, but the present application is not limited to these examples.

The raw materials in the examples of the present application were all purchased commercially, unless otherwise specified.