阅读说明：本技术 一种n型碲化铋基室温热电材料及其制备方法 (N-type bismuth telluride-based room temperature thermoelectric material and preparation method thereof ) 是由 胡利鹏 周延杰 李均钦 刘福生 张朝华 敖伟琴 于 2021-06-22 设计创作，主要内容包括：本发明公开一种n型碲化铋基室温热电材料及其制备方法,所述n型碲化铋基室温热电材料的化学式为Bi-(2-x)Sb-xTe-3,其中,x＝0-1.3。所述n型Bi-(2-x)Sb-xTe-3热电材料在室温附近具有较佳的热电优值,由于n型Bi-(2-x)Sb-xTe-3与p型Bi-(2-x)Sb-xTe-3的组成元素相同,所以两者不仅应用温区匹配,机械力学上更加匹配,进而能够大幅度提升热电器件的使用寿命与成品率。本发明提供的制备方法简单、成本低、可重复性好。(The invention discloses an n-type bismuth telluride-based room temperature thermoelectric material and a preparation method thereof, wherein the chemical formula of the n-type bismuth telluride-based room temperature thermoelectric material is Bi 2‑x Sb x Te 3 Wherein x is 0 to 1.3. The n-type Bi 2‑x Sb x Te 3 The thermoelectric material has better thermoelectric figure of merit near room temperature due to the n-type Bi 2‑x Sb x Te 3 And p-type Bi 2‑x Sb x Te 3 The components are the same, so that the temperature zone matching and the mechanical matching are not only applied to temperature zone matching, but also better matched in mechanical mechanics, and the service life and the yield of the thermoelectric device can be greatly prolonged. The preparation method provided by the invention is simple, low in cost and good in repeatability.)

1. The n-type bismuth telluride-based room temperature thermoelectric material is characterized in that the chemical formula of the n-type bismuth telluride-based room temperature thermoelectric material is Bi_2-xSb_xTe₃Wherein x is 0 to 1.3.

2. The n-type bismuth telluride-based room temperature thermoelectric material as claimed in claim 1, wherein the chemical formula of the n-type bismuth telluride-based room temperature thermoelectric material is Bi_1.5Sb_0.5Te₃Or Bi_1.4Sb_0.6Te₃。

3. A method for producing an n-type bismuth telluride-based room-temperature thermoelectric material as described in any one of claims 1 to 2, comprising the steps of:

according to the chemical formula Bi_2-xSb_xTe₃Weighing a Bi metal block, an Sb metal block and a Te metal block according to the stoichiometric ratio of the elements, smelting the Bi metal block, the Sb metal block and the Te metal block, and cooling to obtain an alloy ingot;

ball-milling the alloy ingot to obtain alloy powder;

and sintering the alloy powder to obtain the n-type bismuth telluride-based room temperature thermoelectric material.

4. The preparation method according to claim 3, wherein the specific steps of melting the Bi metal block, the Sb metal block and the Te metal block comprise:

the Bi metal block, the Sb metal block and the Te metal block are put into a smelting furnace, the temperature is raised to 600-fold sand 700 ℃ at the temperature raising speed of 2-4 ℃/min, and the temperature is kept for 2-4 h;

then raising the temperature to 900-.

5. The method according to claim 4, wherein the Bi metal blocks, the Sb metal blocks and the Te metal blocks are put into a smelting furnace in order of melting point from top to bottom.

6. A method as claimed in claim 3, wherein said step of ball milling said alloy ingot comprises:

and putting the alloy ingot into a ball milling tank, adding a steel ball with the diameter of 5-15mm, and carrying out ball milling for 15-25min at the rotating speed of 1000-1500 r/min.

7. The method according to claim 6, wherein steel balls having diameters of 15mm, 12mm, 7mm, and 5mm are added.

8. The method according to claim 7, wherein the number ratio of the steel balls with the diameters of 15mm, 12mm, 7mm and 5mm is 1:3:10: 22.

9. The method according to claim 3, wherein the step of sintering the alloy powder comprises:

placing the alloy powder in a first graphite die, and sintering at 500 ℃ and 40-50MPa to obtain a block;

placing the block in a second graphite mold, and sintering at 500 ℃ and 40-50 MPa; the diameter of the first graphite mold is smaller than the diameter of the second graphite mold.

10. The method of claim 9, wherein the first graphite mold has a diameter of 10 to 20mm, and the second graphite mold has a diameter of 12.7 to 25 mm.

Technical Field

The invention relates to the field of thermoelectric materials, in particular to an n-type bismuth telluride-based room-temperature thermoelectric material and a preparation method thereof.

Background

The global energy consumption is huge, the utilization efficiency of the existing energy is low, most energy is wasted in the form of waste heat, and the thermoelectric material is widely concerned as a new energy material capable of directly converting heat energy into electric energy.

The thermoelectric material is a material which realizes the mutual conversion of electric energy and heat energy by utilizing three thermoelectric effects. The thermoelectric device is formed by thermally connecting p-type and n-type thermocouple pairs in parallel and electrically connecting the p-type and n-type thermocouple pairs in series. Bismuth telluride is the first thermoelectric material found in the thermoelectric field and has been the only commercial application at present for the longest time. P-type Bi_2-xSb_xTe₃And n-type Bi₂Te_3-xSe_xIs the basis of the application of thermoelectric devices, the working efficiency of the thermoelectric devices mainly depends on the thermoelectric figure of merit of the thermoelectric material, zT ═ (S)²σ/κ) T, where S, σ and κ are Seebeck coefficient, electrical conductivity and thermal conductivity (including carrier thermal conductivity κ), respectively_eAnd lattice thermal conductivity κ_l) And T is the service temperature of the device.

In commercial application, the thermoelectric material can be used for thermoelectric power generation and room temperature solid state refrigeration, but the thermoelectric power generation efficiency is low, and the room temperature solid state refrigeration has wide application prospect. At present, p-type Bi_2-xSb_xTe₃Has a zT value of between 1.4 and 1.8, and n-type Bi₂Te_3-xSe_xThe zT of the p-type thermoelectric material is 0.8-1.4, the performance of the p-type thermoelectric material and the performance of the n-type thermoelectric material are different, the thermoelectric peak value of the p-type thermoelectric material can be obtained at medium and low temperature, the thermoelectric peak value of the n-type thermoelectric material can be almost obtained only at medium and high temperature, the application temperature zones of the p-type thermoelectric material and the n-type thermoelectric material are not matched, and the service life and the yield of devices are low when the p-type thermoelectric material and the n-type thermoelectric material are used for room-temperature solid-state refrigeration.

Therefore, it is of great significance to develop an n-type bismuth telluride-based thermoelectric material with a better thermoelectric figure of merit near room temperature.

Disclosure of Invention

In view of the defects of the prior art, the invention aims to provide an n-type bismuth telluride-based room temperature thermoelectric material and a preparation method thereof, aiming at solving the problems that the application temperature regions of the existing p-type thermoelectric material and the existing n-type thermoelectric material are not matched, and the service life and the yield of devices are low when the n-type bismuth telluride-based room temperature thermoelectric material is used for room temperature solid state refrigeration.

The technical scheme of the invention is as follows:

in a first aspect of the present invention, an n-type bismuth telluride-based room-temperature thermoelectric material is provided, wherein the chemical formula of the n-type bismuth telluride-based room-temperature thermoelectric material is Bi_2-xSb_xTe₃Wherein x is 0 to 1.3.

Optionally, the chemical formula of the n-type bismuth telluride-based room temperature thermoelectric material is Bi_1.5Sb_0.5Te₃Or Bi_1.4Sb_0.6Te₃。

In a second aspect of the present invention, there is provided a method for preparing an n-type bismuth telluride-based room temperature thermoelectric material, comprising the steps of:

according to the chemical formula Bi_2-xSb_xTe₃Weighing a Bi metal block, an Sb metal block and a Te metal block according to the stoichiometric ratio of the elements, smelting the Bi metal block, the Sb metal block and the Te metal block, and cooling to obtain an alloy ingot;

ball-milling the alloy ingot to obtain alloy powder;

and sintering the alloy powder to obtain the n-type bismuth telluride-based room temperature thermoelectric material.

Optionally, the specific steps of smelting the Bi metal block, the Sb metal block, and the Te metal block include:

the Bi metal block, the Sb metal block and the Te metal block are put into a smelting furnace, the temperature is raised to 600-fold sand 700 ℃ at the temperature raising speed of 2-4 ℃/min, and the temperature is kept for 2-4 h;

then raising the temperature to 900-.

Optionally, the Bi metal blocks, the Sb metal blocks and the Te metal blocks are put into a smelting furnace in the order of melting point from top to bottom.

Optionally, the specific step of ball milling the alloy ingot comprises:

and putting the alloy ingot into a ball milling tank, adding a steel ball with the diameter of 5-15mm, and carrying out ball milling for 15-25min at the rotating speed of 1000-1500 r/min.

Optionally, steel balls with diameters of 15mm, 12mm, 7mm and 5mm are added.

Optionally, the number ratio of the steel balls with the diameters of 15mm, 12mm, 7mm and 5mm is 1:3:10: 22.

Optionally, the specific step of sintering the alloy powder includes:

placing the alloy powder in a first graphite die, and sintering at 500 ℃ and 40-50MPa to obtain a block;

placing the block in a second graphite mold, and sintering at 500 ℃ and 40-50 MPa; the diameter of the first graphite mold is smaller than the diameter of the second graphite mold.

Optionally, the diameter of the first graphite mold is 10-20mm, and the diameter of the second graphite mold is 12.7-25 mm.

Has the advantages that: the invention provides an n-type bismuth telluride-based room-temperature thermoelectric material and a preparation method thereof, wherein the chemical formula of the n-type bismuth telluride-based room-temperature thermoelectric material is Bi_2-xSb_xTe₃It has a better thermoelectric figure of merit at around room temperature due to n-type Bi_2-xSb_xTe₃And p-type Bi_2-xSb_xTe₃The components are the same, so that the temperature zone matching and the mechanical matching are not only applied to temperature zone matching, but also better matched in mechanical mechanics, and the service life and the yield of the thermoelectric device can be greatly prolonged.

Drawings

FIG. 1 shows n-type Bi in example 1 of the present invention_2-xSb_xTe₃The Seebeck coefficient test result chart.

FIG. 2 shows n-type Bi in example 2 of the present invention_1.5Sb_0.5Te₃The zT values of (a) are shown in the test results.

FIG. 3 shows n-type Bi in example 2 of the present invention_1.5Sb_0.5Te₃Graph of zT values test results when performing repeatable tests.

FIG. 4 shows n-type Bi in example 2 of the present invention_1.5Sb_0.5Te₃The expansion coefficient of (2) test result chart.

FIG. 5 shows n-type Bi in example 2 of the present invention_1.5Sb_0.5Te₃The results of the compression and bending tests are shown.

Detailed Description

The invention provides an n-type bismuth telluride-based room temperature thermoelectric material and a preparation method thereof, and the invention is further described in detail below in order to make the purpose, technical scheme and effect of the invention clearer and clearer. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The embodiment of the invention provides an n-type bismuth telluride-based room temperature thermoelectric material, wherein the chemical formula of the n-type bismuth telluride-based room temperature thermoelectric material is Bi_2-xSb_xTe₃Wherein x is 0 to 1.3.

In the field of bismuth telluride, p-type Bi_2-xSb_xTe₃N-type Bi₂Te_3-xSe_xThe method is almost a custom cognition, the thermoelectric peak value of the p-type bismuth telluride-based thermoelectric material can be obtained at a medium-low temperature, the thermoelectric peak value of the n-type bismuth telluride-based thermoelectric material can be obtained at a medium-high temperature, and when the bismuth telluride device is used for room-temperature solid-state refrigeration, the application temperature regions of the p-type bismuth telluride-based thermoelectric material and the n-type bismuth telluride-based thermoelectric material are not matched, so that the efficiency of the device is low. Therefore, the method is particularly important for developing the high-performance n-type bismuth telluride-based thermoelectric material near room temperature, and no researchers are available to prepare the high-performance n-type Bi near room temperature_2-xSb_xTe₃The invention relates to a thermoelectric material, in particular to an n-type bismuth telluride-based room-temperature thermoelectric material, namely n-type Bi, prepared by a simple preparation method_2-xSb_xTe₃Wherein x is 0-1.3, from p-type Bi_2-xSb_xTe₃Thermoelectric material to n-type Bi_{2- x}Sb_xTe₃Transformation of thermoelectric material, and the n-type Bi_2-xSb_xTe₃Has good thermoelectric performance near room temperatureThermoelectric material having a value of zT around room temperature greater than that of most of n-type, n-type Bi_2-xSb_xTe₃With the prior art p-type Bi_2-xSb_xTe₃The two elements are composed of the same elements, so that the two elements are more matched in mechanical thermodynamics, and the service life and the yield of the thermoelectric device can be greatly prolonged.

In one embodiment, the chemical formula of the n-type bismuth telluride-based room temperature thermoelectric material is Bi_1.5Sb_0.5Te₃Or Bi_1.4Sb_0.6Te₃。

The embodiment of the invention also provides a preparation method of the n-type bismuth telluride-based room-temperature thermoelectric material, which comprises the following steps:

s1, according to the chemical formula Bi_2-xSb_xTe₃Weighing a Bi metal block, an Sb metal block and a Te metal block according to the stoichiometric ratio of the elements, smelting the Bi metal block, the Sb metal block and the Te metal block, and cooling to obtain an alloy ingot;

s2, performing ball milling on the alloy ingot to obtain alloy powder;

s3, sintering the alloy powder to obtain the n-type bismuth telluride-based room temperature thermoelectric material.

In this embodiment, the Bi metal block to be weighed is composed of a plurality of small metal blocks, and similarly, the Sb metal block and the Te metal block to be weighed are also composed of a plurality of small metal blocks. Of course, if the mass of the prepared n-type bismuth telluride-based room temperature thermoelectric material is small, there is a case where there is only one Bi metal block or Sb metal block or Te metal block, that is, the present embodiment does not limit the block size of the Bi metal block, Sb metal block or Te metal block.

In the prior art, an n-type bismuth telluride-based thermoelectric material Bi₂Te_3-xSe_xThe boiling point and the evaporation energy of the element Se are far lower than those of the element Te, the Se is extremely easy to volatilize in the smelting process, so that the V-group element is excessive and deviates from the normal atomic ratio, and the Se content is changed by adopting different equipment or different experimenters, so that the repeatability is extremely low (the repeatability is poor, n-type Bi is adopted₂Te_3-xSe_xThe pain point which is difficult to solve in the preparation process) does not meet the requirement of industrial production. And if it is desired to obtain high-performance n-type Bi₂Te_3-xSe_xThe preparation method is complex and the cost is high. Compared with the prior art, the n-type Bi in the embodiment_{2- x}Sb_xTe₃The method does not contain Se, does not have the problem of Se volatilization in the prior art, has good repeatability, adopts a technical route of smelting, ball milling and sintering in the embodiment, and has simple preparation method and low cost.

In the ball milling process, according to the formation rule of the inversion defects, after Sb is added, the number of the inversion defects can be increased, and donor-like effect can occur, so that Bi_2-xSb_xTe₃The conductive material has n-type conductivity, but the Sb content is increased continuously, the number of the inversion defects is more than required, and the generated vacancies can be compounded with electrons, so that the carrier concentration is reduced to be within an optimal range. And Bi_2-xSb_xTe₃Has an energy band degeneracy higher than Bi₂Te_3-xSe_xThe degeneracy of the energy band is improved, and the effects of the two aspects are favorable for the n-type Bi_2-xSb_xTe₃Good electrical properties are obtained. An increase in Sb content only slightly reduces the forbidden bandwidth, which is beneficial to keep the zT peak at room temperature. In addition, the sintering process involves thermal deformation, and phonons with different frequencies are scattered by alloy scattering and different defects generated by the thermal deformation, so that the lattice thermal conductivity is reduced, and a higher zT value is obtained. The point defect model of the donor-like effect is shown in the following formula (1), wherein,andis Bi and Te vacancies produced during thermal deformation, Bi'_TeThe crystal growth process generates inversion defects, the interaction of vacancies generated in the thermal deformation process and the inversion defects generated in the crystal growth process generates additional electrons e', the generated additional electrons continuously exist in the thermal deformation process, and the electron concentration is increased.Thus, the donor-like effect during ball milling and hot deformation increases n-type Bi_2-xSb_xTe₃Electrical properties of (2).

In step S1, Bi is expressed by the chemical formula_2-xSb_xTe₃The Bi metal block, the Sb metal block, and the Te metal block are weighed according to the stoichiometric ratio of the respective elements, and when x is 1, the Bi metal block, the Sb metal block, and the Te metal block are weighed according to the molar ratio of 1:1:3, for example.

In one embodiment, the specific steps of melting the Bi metal block, the Sb metal block, and the Te metal block include:

the Bi metal block, the Sb metal block and the Te metal block are put into a smelting furnace, the temperature is raised to 600-fold sand 700 ℃ at the temperature raising speed of 2-4 ℃/min, and the temperature is kept for 2-4 h;

then raising the temperature to 900-.

Keeping the temperature for 2-4h at the temperature of 600-700 ℃, wherein the three metal blocks are melted, then raising the temperature to 1000 ℃ at the temperature of 900-4 ℃/min, and keeping the temperature for 10-20h, namely keeping the temperature for a long time at high temperature so as to ensure that the melted metal blocks are uniformly mixed to become solid solution and no second phase is generated.

In one embodiment, the Bi metal block, the Sb metal block, and the Te metal block are put into a smelting furnace in order from the melting point up to the bottom. Since the melting point of Sb is higher than that of Te and higher than that of Bi, in this embodiment, the Sb metal block is first put into a melting furnace, the Te metal block is then put into the melting furnace, and finally the Bi metal block is put into the melting furnace.

In one embodiment, the Sb metal block is put into a quartz tube, the Te metal block is put into the quartz tube, the Bi metal block is put into the quartz tube, the quartz tube is vacuumized and sealed by hydrogen flame, and then the vertical (the Sb metal block, the Te metal and the Bi metal block are arranged in sequence from bottom to top of the quartz tube) is put into a resistance furnace for smelting.

In step S2, in one embodiment, the step of ball milling the alloy ingot comprises:

and putting the alloy ingot into a ball milling tank, adding a steel ball with the diameter of 5-15mm, and carrying out ball milling for 15-25min at the rotating speed of 1000-1500 r/min.

In one embodiment, steel balls with diameters of 15mm, 12mm, 7mm, 5mm are added.

In this step, steel balls with diameters of 15mm, 12mm, 7mm and 5mm are required to be added simultaneously, the steel balls with diameters of 15mm and 12mm are helpful for crushing alloy ingots, and the steel balls with diameters of 7mm and 5mm are helpful for grinding fine powder, so that alloy powder is obtained. The ball milling time is not suitable to be too long or too short, the too long affects the vacancy number generated in the n-type bismuth telluride material, the carrier concentration is finally affected, and the too short powder is not fine enough.

In one embodiment, the number ratio of the steel balls with the diameters of 15mm, 12mm, 7mm and 5mm is 1:3:10: 22.

In one embodiment, the number of the steel balls with the diameters of 15mm, 12mm, 7mm and 5mm is 1, 3, 10 and 22 respectively. In specific implementation, 1 steel ball with the diameter of 15mm, 3 steel balls with the diameter of 12mm, 10 steel balls with the diameter of 7mm and 22 steel balls with the diameter of 5mm are added into a ball milling tank to ball mill the alloy ingot.

In one embodiment, the ball mill pot is selected from one of a stainless steel ball mill pot and an agate ball mill pot, but is not limited thereto.

In one embodiment, after the ball milling of the alloy ingot to obtain the alloy powder, the method further comprises: sieving with a sieve with the diameter of 300 microns to obtain alloy powder with the particle size of less than 300 microns.

In step S3, in one embodiment, the step of sintering the alloy powder includes:

placing the alloy powder in a first graphite die, and sintering at 500 ℃ and 40-50MPa to obtain a block;

placing the block in a second graphite mold, and sintering at 500 ℃ and 40-50 MPa; the diameter of the first graphite mold is smaller than the diameter of the second graphite mold.

In the embodiment, the sintering temperature and pressure are not suitable to be too low, the temperature is too low, the donor-like effect in the n-type bismuth telluride material is not strong enough, the carrier concentration is difficult to optimize, the performance is low, the temperature is close to the melting point of the bismuth telluride solid solution at 500 ℃, the improvement of the thermoelectric performance is most beneficial, the n-type bismuth telluride-based room-temperature thermoelectric material sintered at too low pressure is not compact, the mechanical performance is poor, the n-type bismuth telluride-based room-temperature thermoelectric material sintered at too high pressure is too compact, the thermal conductivity is increased due to the improvement of the density, and the improvement of the thermoelectric figure of merit is not beneficial.

In this embodiment, the diameter of the first graphite mold is smaller than the diameter of the second graphite mold, and thermal deformation can be achieved. The thermal deformation is favorable for enhancing the texture of the n-type bismuth telluride-based room-temperature thermoelectric material, improving the mobility and improving the electrical property, particularly because of the layered structure and weak-Te of the bismuth telluride¹-Te¹The bond is easy to slip along a basal plane vertical to the c axis of the crystal to form a strong texture, the bismuth telluride-based thermoelectric material is continuously extruded in the thermal deformation process, the texture is easy to generate, and the texture is beneficial to electron transportation and improves the electron mobility. In addition, the thermal deformation can introduce the defects of various scales to the n-type bismuth telluride-based room thermoelectric material, a multi-scale scattering center is formed, phonons of different frequencies are scattered, the lattice thermal conductivity is reduced, the thermoelectric performance is improved, the thermal deformation can also increase the strong donor-like effect of the n-type bismuth telluride-based room thermoelectric material, and the carrier concentration is improved.

In specific implementation, the alloy powder is placed in a first graphite die and then is placed in a plasma discharge sintering furnace to be sintered for 5min at 500 ℃ and 40-50 MPa; and taking out the block after sintering, cleaning the surface of the block, removing the graphite paper, putting the block into a second graphite mold with the diameter larger than that of the first graphite mold, and then putting the block into a plasma discharge sintering furnace to be sintered for 5min at the temperature of 500 ℃ and the pressure of 40-50MPa, thereby realizing the thermal deformation process.

In one embodiment, the first graphite mold has a diameter of 10 to 20mm, and the second graphite mold has a diameter of 12.7 to 25 mm.

In specific implementation, a first graphite mold with the diameter of 10mm and a second graphite mold with the diameter of 12.7mm can be selected to realize the thermal deformation process; or a first graphite die with the diameter of 12.7mm and a second graphite die with the diameter of 15mm can be selected to realize the thermal deformation process; the thermal deformation process can also be realized by selecting a first graphite mold with the diameter of 15mm and a second graphite mold with the diameter of 20 mm; the thermal deformation process can also be realized by selecting a first graphite mold with the diameter of 20mm and a second graphite mold with the diameter of 25 mm.

The invention is further illustrated by the following specific examples.

Example 1

n-type Bi_2-xSb_xTe₃Preparation of room temperature thermoelectric materials

According to the chemical formula Bi_2-xSb_xTe₃The stoichiometric ratio of the elements in the formula (2-x): x: 3 (wherein x is 0, 0.1, 0.3, 0.5, 0.6, 0.8, 1.0, 1.2, 1.3), and the Bi metal block, the Sb metal block, and the Te metal block were weighed out in the respective masses. Then placing the Sb metal block into a quartz tube, then placing the Te metal block into the quartz tube, finally placing the Bi metal block into the quartz tube, vacuumizing and then sealing by using hydrogen flame, then vertically placing the vertical (the Sb metal block, the Te metal and the Bi metal block are sequentially arranged from bottom to top of the quartz tube) into a high-temperature box type resistance furnace, gradually increasing the temperature from room temperature to 650 ℃ at the temperature rise speed of 2 ℃/min, preserving heat for 2h, then increasing the temperature to 900 ℃ at the temperature rise speed of 4 ℃/min, preserving heat for 10h, and cooling to obtain the alloy ingot block. Then adding the alloy ingot, 1 steel ball with the diameter of 15mm, 3 steel balls with the diameter of 12mm, 10 steel balls with the diameter of 7mm and 22 steel balls with the diameter of 5mm into a stainless steel ball milling tank, ball milling for 20min at the rotating speed of 1200r/min, and sieving by using a sieve with the diameter of 300 microns to obtain alloy powder with the particle size of less than 300 microns. Placing the alloy powder in a graphite die with the diameter of 15mm, and then sintering for 5min in a plasma discharge sintering furnace at the temperature of 500 ℃ and under the pressure of 40-50 MPa; taking out the block after sinteringCleaning the surface of the block, removing graphite paper, placing the block into a graphite mold with a diameter of 20mm, and sintering in a plasma discharge sintering furnace at 500 ℃ and 40-50MPa for 5min to obtain n-type Bi_2-xSb_xTe₃Thermoelectric material, wherein x is 0, 0.1, 0.3, 0.5, 0.6, 0.8, 1.0, 1.2, 1.3. For Bi_2-xSb_xTe₃The thermoelectric material is subjected to Seebeck coefficient (seebeck coefficient) test, the results are shown in figure 1, the Seebeck coefficients of all samples are negative numbers, and the Bi prepared by the method is proved_2-xSb_xTe₃The thermoelectric material is n-type.

Example 2

n-type Bi_1.5Sb_0.5Te₃Preparation of room temperature thermoelectric materials

According to the chemical formula Bi_2-xSb_xTe₃The stoichiometric ratio of each element in the formula (I) is 1.5: 0.5: 3, weighing Bi metal blocks, Sb metal blocks and Te metal blocks with corresponding mass. Then placing the Sb metal block into a quartz tube, then placing the Te metal block into the quartz tube, finally placing the Bi metal block into the quartz tube, vacuumizing and then sealing by using hydrogen flame, then vertically placing the vertical (the Sb metal block, the Te metal and the Bi metal block are sequentially arranged from bottom to top of the quartz tube) into a high-temperature box type resistance furnace, gradually increasing the temperature from room temperature to 650 ℃ at the temperature rise speed of 2 ℃/min, preserving heat for 2h, then increasing the temperature to 900 ℃ at the temperature rise speed of 4 ℃/min, preserving heat for 10h, and cooling to obtain the alloy ingot block. Then adding the alloy ingot, 1 steel ball with the diameter of 15mm, 3 steel balls with the diameter of 12mm, 10 steel balls with the diameter of 7mm and 22 steel balls with the diameter of 5mm into a stainless steel ball milling tank, ball milling for 20min at the rotating speed of 1200r/min, and sieving by using a sieve with the diameter of 300 microns to obtain alloy powder with the particle size of less than 300 microns. Placing the alloy powder in a graphite die with the diameter of 15mm, and then sintering for 5min in a plasma discharge sintering furnace at the temperature of 500 ℃ and under the pressure of 40-50 MPa; taking out the block after sintering, cleaning the surface of the block, removing graphite paper, putting the block into a graphite mold with the diameter of 20mm, and then putting the block into a plasma discharge sintering furnace at the temperature of 500 ℃ and under the pressure of 40-50MPaSintering for 5min to obtain n-type Bi_1.5Sb_0.5Te₃A room temperature thermoelectric material.

Testing the zT value:

for n-type Bi in example 2_1.5Sb_0.5Te₃The result of the zT value test of the thermoelectric material is shown in fig. 2, where HD represents the thermal deformation and it can be seen that n-type Bi is around 330K_1.5Sb_0.5Te₃The room temperature performance of the thermoelectric material is higher than that of most n-type thermoelectric materials, but is slightly lower than that of Bi doped or subjected to multiple thermal deformation or other more complex processes₂Te_{3- x}Se_xFrom this, it is known that n-type Bi_1.5Sb_0.5Te₃The room temperature thermoelectric material has a better thermoelectric figure of merit near room temperature.

And (3) repeatability testing:

the preparation steps of example 2 are repeated 4 times, and the obtained 4 samples are subjected to the zT value test, the result of which is shown in fig. 3, the highest performance of all the samples is 330-350K, and the original performance can be still maintained after the multiple preparation and multiple tests.

And p-type Bi_1.5Sb_0.5Te₃The matching test of (2):

for n-type Bi in example 2_1.5Sb_0.5Te₃P-type Bi in the prior art_1.5Sb_0.5Te₃And n-type Bi₂Te_2.7Se_0.3The results of the expansion coefficient test are shown in FIG. 4. As can be seen from FIG. 4, the n-type Bi in example 1 is not lower than 300K and not lower than 360K at low temperature_1.5Sb_0.5Te₃Are all than n type Bi₂Te_2.7Se_0.3Is more matched with p-type Bi_1.5Sb_0.5Te₃。

For the n-type Bi in example 2_1.5Sb_0.5Te₃P-type Bi in the prior art_1.5Sb_0.5Te₃And n-type Bi₂Te_2.7Se_0.3The compression and bending resistance tests were carried out, and the results are shown in FIG. 5, as can be seen from FIG. 5N-type Bi in example 2_1.5Sb_0.5Te₃Higher compression resistance than p-type Bi_1.5Sb_0.5Te₃And n-type Bi₂Te_2.7Se_0.3Bending resistance of p-type Bi_1.5Sb_0.5Te is more matched.

In summary, the chemical formula of the n-type bismuth telluride-based room-temperature thermoelectric material and the preparation method thereof provided by the invention is Bi_2-xSb_xTe₃Wherein x is 0-1.3, which has a better thermoelectric figure of merit around room temperature due to n-type Bi_2-xSb_xTe₃And p-type Bi_2-xSb_xTe₃The components are the same, so that the temperature zone matching and the mechanical matching are not only applied to temperature zone matching, but also better matched in mechanical mechanics, and the service life and the yield of the thermoelectric device can be greatly prolonged. The preparation method provided by the invention is simple, low in cost and good in repeatability.

It is to be understood that the invention is not limited to the examples described above, but that modifications and variations may be effected thereto by those of ordinary skill in the art in light of the foregoing description, and that all such modifications and variations are intended to be within the scope of the invention as defined by the appended claims.