CN114538927A - Non-stoichiometric n-type bismuth telluride sintered material and preparation method thereof - Google Patents
Non-stoichiometric n-type bismuth telluride sintered material and preparation method thereof Download PDFInfo
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- 229910052797 bismuth Inorganic materials 0.000 title claims abstract description 76
- JCXGWMGPZLAOME-UHFFFAOYSA-N bismuth atom Chemical compound [Bi] JCXGWMGPZLAOME-UHFFFAOYSA-N 0.000 title claims abstract description 65
- XSOKHXFFCGXDJZ-UHFFFAOYSA-N telluride(2-) Chemical compound [Te-2] XSOKHXFFCGXDJZ-UHFFFAOYSA-N 0.000 title claims abstract description 65
- 239000000463 material Substances 0.000 title claims abstract description 55
- 238000002360 preparation method Methods 0.000 title claims abstract description 13
- 238000005245 sintering Methods 0.000 claims abstract description 39
- 238000000498 ball milling Methods 0.000 claims abstract description 36
- 239000000126 substance Substances 0.000 claims abstract description 32
- 238000002844 melting Methods 0.000 claims abstract description 20
- 230000008018 melting Effects 0.000 claims abstract description 20
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- 238000001816 cooling Methods 0.000 claims description 22
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- 239000010935 stainless steel Substances 0.000 claims description 7
- 229910001220 stainless steel Inorganic materials 0.000 claims description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 7
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 5
- 238000005266 casting Methods 0.000 claims description 5
- 229910002804 graphite Inorganic materials 0.000 claims description 5
- 239000010439 graphite Substances 0.000 claims description 5
- 238000004519 manufacturing process Methods 0.000 claims 2
- 238000012360 testing method Methods 0.000 description 13
- 230000000052 comparative effect Effects 0.000 description 7
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- 150000002500 ions Chemical class 0.000 description 6
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- 150000001450 anions Chemical class 0.000 description 4
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- 230000009286 beneficial effect Effects 0.000 description 3
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- -1 bismuth telluride compound Chemical class 0.000 description 2
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- OCKGFTQIICXDQW-ZEQRLZLVSA-N 5-[(1r)-1-hydroxy-2-[4-[(2r)-2-hydroxy-2-(4-methyl-1-oxo-3h-2-benzofuran-5-yl)ethyl]piperazin-1-yl]ethyl]-4-methyl-3h-2-benzofuran-1-one Chemical compound C1=C2C(=O)OCC2=C(C)C([C@@H](O)CN2CCN(CC2)C[C@H](O)C2=CC=C3C(=O)OCC3=C2C)=C1 OCKGFTQIICXDQW-ZEQRLZLVSA-N 0.000 description 1
- 229910002899 Bi2Te3 Inorganic materials 0.000 description 1
- 239000013590 bulk material Substances 0.000 description 1
- 239000000969 carrier Substances 0.000 description 1
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Abstract
The invention discloses a non-stoichiometric n-type bismuth telluride sintered material and a preparation method thereof, wherein the chemical formula of the stoichiometric n-type bismuth telluride sintered material is Bi2Te2.7‑xSe0.3‑yWherein x is more than or equal to 0 and less than or equal to 0.06, y is more than or equal to 0 and less than or equal to 0.05, and x and y are not 0 at the same time, and the preparation method of the non-stoichiometric n-type bismuth telluride sintered material comprises the following steps: weighing and mixing the Bi, Te and Se simple substances according to the proportion of the chemical formula, performing ball milling and sintering after swinging and melting the simple substances, and repeating the ball milling and sintering operation for multiple times to prepare the non-stoichiometric n-type bismuth telluride sintered material. The non-stoichiometric n-type bismuth telluride sintered material prepared by the method has the advantages of high electrical conductivity, low thermal conductivity and high mechanical strength, and the preparation method realizes that the n-type bismuth telluride thermoelectric block material has higher thermoelectric property and mechanical property.
Description
Technical Field
The invention relates to the technical field of thermoelectric materials, in particular to a non-stoichiometric n-type bismuth telluride sintered material and a preparation method thereof.
Background
With the development of science and technology and the improvement of living standard of people, the requirements of people on energy sources are higher and higher, and new alternative energy sources are urgently needed to be searched. The thermoelectric material is a functional material which can realize direct interconversion of heat energy and electric energy by utilizing the movement of internal carriers, and has very wide application prospects in thermoelectric generation and semiconductor refrigeration. Bismuth telluride has been developed as a thermoelectric material since the fifties of the last century and is still the subject of commercial applications to date. The research on the bismuth telluride-based thermoelectric material focuses on the improvement of thermoelectric figure of merit ZT and the enhancement of mechanical properties of the material.
The difficulty in the process of cutting particles is determined by the layered bismuth telluride bulk at present, and in the aspect of thermoelectric property, the zT value of an n-type bismuth telluride-based (BiTeSe) material is generally lower than that of a p-type Bi material2Te3The ZT value of the base material is about 1.4-1.8, but n-type Bi2Te3The ZT value of the base material is rarely higher than 1.0, and the thermoelectric module is acted by an n-type thermoelectric element and a p-type thermoelectric element, so that the thermoelectric conversion efficiency is difficult to improve due to the short n-type performance, and the practical application of the thermoelectric module is severely restricted.
Disclosure of Invention
The invention aims to solve the technical problem of providing a non-stoichiometric n-type bismuth telluride sintered material with high electrical conductivity, low thermal conductivity and high mechanical strength aiming at the defects and the defects of an n-type bismuth telluride base (BiTeSe) material in the prior art.
The invention further aims to solve the technical problem of improving the mechanical strength and the zT value of the n-type bismuth telluride base (BiTeSe) and improving the overall thermoelectric conversion efficiency of the thermoelectric module.
The technical scheme adopted by the invention for solving the technical problems is as follows:a non-stoichiometric n-type bismuth telluride sintered material comprises the following chemical compositions: bi2Te2.7-xSe0.3-yWherein x is more than or equal to 0 and less than or equal to 0.06, y is more than or equal to 0 and less than or equal to 0.05, and x and y are not 0 at the same time.
The invention provides a method for preparing the non-stoichiometric n-type bismuth telluride sintered material, which comprises the following steps:
s1, weighing: according to the chemical formula Bi2Te2.7-xSe0.3-yWeighing and mixing the simple substances Bi, Te and Se according to the proportion, wherein x is more than or equal to 0 and less than or equal to 0.06, y is more than or equal to 0 and less than or equal to 0.05, and x and y are not 0 at the same time, transferring the mixed simple substances into a clean closed reaction tube, and sealing the tube under vacuum;
s2, swing melting: placing the sealed reaction tube into a rocking furnace, rocking and melting at high temperature, and then rapidly cooling to room temperature to obtain a block;
s3, ball milling: ball-milling the block obtained in the step S2 into powder;
s4, sintering powder: s3, placing the obtained powder into a mold, and sintering the powder in a hot-pressing induction furnace or a plasma sintering furnace to obtain an n-type bismuth telluride-based ingot casting block;
s5, repeats S3 and S4: and ball-milling the ingot casting block obtained in the step S4 into powder again according to the step S3, sintering again according to the step S4, and obtaining the n-type bismuth telluride-based sintered block after ball milling and sintering for multiple times.
Further, in S1, the tube was sealed under a vacuum degree <10 Pa.
Further, in the step S2, the melting temperature is 600-950 ℃, and the swinging time is 15-720 minutes.
Further, in S2, the rapid cooling mode is room temperature quenching or room temperature water quenching.
In S4, the mold is made of stainless steel or graphite.
Further, in the S3, the ball milling time is 3-15 minutes, and the rotation speed is 1000-.
Further, in the step S4, after the vacuum pumping is performed in the sintering process to below 10Pa, the temperature is gradually increased to the sintering temperature of 450-600 ℃, then the pressure is gradually increased to 50-100 Mpa, when the forming pressure is reached, the temperature and pressure are kept for 5-60 min, and finally the temperature and the pressure are reduced and relieved along with the furnace.
Further, in the S5, the number of repetitions of S3 and S4 is 2 to 4.
Specifically, when the bismuth telluride-based thermoelectric material prepared by the method is used for testing the electrothermal transport performance, the thermoelectric block is cut into 3.0mm by 12mm
10mm by 2mm test sample.
The invention has the following beneficial effects:
the invention prepares an n-type bismuth telluride material with a chemical formula of Bi2Te2.7-xSe0.3-yWherein x is more than or equal to 0 and less than or equal to 0.06, y is more than or equal to 0 and less than or equal to 0.05, and x and y are not 0 at the same time, and the proportion of Te and Se elements is artificially reduced in the burdening process. According to the valence sum of the compounds being 0, the proportion of the positive ions and the negative ions of the bismuth telluride compound is 2:3, and the invention reduces the proportion of Te and Se, so that the proportion of the positive ions and the negative ions of the bismuth telluride compound is more than 2:3, the number of the negative ions is reduced, and the negative ion vacancy is introduced. The anion vacancy effectively makes up the deficiency of the donor-like effect, induces and generates enough electrons, enhances the carrier concentration, increases the vacancy point defect distribution, improves the phonon scattering probability and is beneficial to reducing the lattice thermal conductivity. In addition, a large number of introduced anion vacancies are uniformly dispersed in the crystal grains, so that the mechanical strength of the n-type bismuth telluride bulk material is enhanced.
According to the invention, multiple ball milling and sintering operations are carried out in the process of preparing the n-type bismuth telluride material, so that the preferred orientation of bismuth telluride-based crystal grains is effectively improved, high mobility is formed, and the power factor is improved by about 15% due to the high mobility and high carrier concentration. According to the thermoelectric figure of merit formula ZT ═ S2σT/κtotWherein S is a Seebeck coefficient, σ is an electric conductivity, T is an absolute temperature, and κtotIn order to achieve the total thermal conductivity, the n-type bismuth telluride material prepared by the invention has a large power factor (PF ═ S)2Sigma) and smaller thermal conductivity, so that the ZT value of the alloy is obviously improved, thereby improvingThe thermoelectric property of the n-type bismuth telluride thermoelectric material is improved.
The non-stoichiometric n-type bismuth telluride sintered material prepared by the method has the advantages of high electrical conductivity, low thermal conductivity and high mechanical strength, and the method comprehensively realizes that the n-type bismuth telluride thermoelectric block material has higher thermoelectric property and mechanical property.
Drawings
FIG. 1 is a graph showing a comparison of Vickers hardnesses of samples obtained in comparative example 1 and example 2 of the present invention;
FIG. 2 is a comparison of PF-T curves for inventive example 2 and comparative example 3;
FIG. 3 is a comparison of the kappa-T curves of inventive example 2 and comparative example 3;
FIG. 4 is a graph comparing ZT-T curves of inventive example 2 and comparative example 3.
Detailed Description
In order to clearly understand the technical features, objects and effects of the present invention, the present invention will be further described in detail with reference to the following embodiments, which are only used for explaining the present invention and are not to be construed as limiting the scope of the present invention.
A non-stoichiometric n-type bismuth telluride sintered material comprises the following chemical compositions: bi2Te2.7-xSe0.3-yWherein x is more than or equal to 0 and less than or equal to 0.06, y is more than or equal to 0 and less than or equal to 0.05, and x and y are not 0 at the same time. The raw material proportion of the invention only needs to reduce the proportion of the whole anions according to a chemical formula, does not limit the relative proportion of Te and Se elements, and is applicable to the invention within the proportion range.
The invention provides a method for preparing the non-stoichiometric n-type bismuth telluride sintered material, which comprises the following steps:
s1, weighing: according to the chemical formula Bi2Te2.7-xSe0.3-yWeighing and mixing the simple substances Bi, Te and Se according to the proportion, wherein x is more than or equal to 0 and less than or equal to 0.06, y is more than or equal to 0 and less than or equal to 0.05, and x and y are not 0 at the same time, transferring the mixed simple substances into a clean closed reaction tube, sealing the tube under vacuum, and particularly, preferably selecting the vacuum degree<Sealing the pipe under 10 Pa; the vacuum degree here refers to the reading of a vacuum gauge, and the vacuum degree<10Pa, and is not limited thereto.
S2, swing melting: placing the sealed reaction tube into a rocking furnace, rocking and melting at high temperature, and then rapidly cooling to room temperature to obtain a block; specifically, the melting temperature is preferably 600-950 ℃, and the swinging time is preferably 15-720 minutes; the rapid cooling mode is room temperature quenching or room temperature water quenching;
s3, ball milling: ball-milling the block obtained in the step S2 into powder; the ball milling time is 3-15 minutes, and the rotating speed is 1000-;
s4, sintering powder: placing the powder obtained in the step S3 into a mold, and sintering the powder in a hot-pressing induction furnace or a plasma sintering furnace to obtain an n-type bismuth telluride-based ingot block, wherein the mold is preferably made of stainless steel or graphite; after the vacuum degree is vacuumized to be below 10Pa in the sintering process, gradually heating to the sintering temperature of 450-600 ℃, then gradually increasing the pressure to 50-100 Mpa, keeping the temperature and the pressure for 5-60 min when the forming pressure is reached, and finally cooling and releasing the pressure along with the furnace;
s5, repeats S3 and S4: and ball-milling the ingot casting block obtained in the step S4 into powder again according to the step S3, sintering again according to the step S4, and obtaining the n-type bismuth telluride-based sintered block after ball milling and sintering for multiple times. The number of repetitions of S3 and S4 is 2 to 4.
The following is illustrated by specific examples:
comparative example 1, this example is a conventional stoichiometric n-type bismuth telluride sintered material is Bi2Te2.7Se0.3. For comparison of the non-stoichiometric n-type bismuth telluride sintered material of the present invention.
The preparation method of the n-type bismuth telluride sintered material in the embodiment is as follows:
s1: weighing: according to the chemical formula Bi2Te2.7Se0.3Proportionally weighing elementary substances of Bi, Te and Se, mixing, transferring into a clean closed reaction tube, and sealing the tube under vacuum of 10 Pa;
s2: swing melting: placing the sealed reaction tube into a swinging furnace, melting at 750 ℃, swinging for 350 minutes at the same time, and then quickly cooling to room temperature, wherein the quick cooling is normal-temperature water quenching;
s3: ball milling: ball-milling the block obtained in the step S2 into powder, wherein the ball-milling time is 9 minutes, and the rotating speed is 1200 rpm;
s4: sintering powder: putting the powder obtained in the step S3 into a stainless steel mold, and then putting the mold into a hot-pressing induction furnace; when the vacuum is pumped to 10Pa, the temperature is gradually increased to the sintering temperature of 420 ℃; gradually increasing the pressure to 70Mpa, keeping the temperature and pressure for 30min when the molding pressure is reached, and finally cooling and releasing the pressure along with the furnace to obtain an n-type bismuth telluride-based sintered block;
s5: repeat S3 and S4: the ingot obtained in S4 was again ball-milled into powder and sintered, and the above operation was repeated 3 times to obtain Bi as a chemical composition2Te2.7Se0.3The n-type bismuth telluride-based sintered block.
Example 2A nonstoichiometric sintered n-type bismuth telluride material was Bi2Te2.67Se0.28。
The preparation method of the nonstoichiometric n-type bismuth telluride sintered material in the embodiment is as follows:
s1: weighing: according to the chemical formula Bi2Te2.67Se0.28Proportionally weighing elementary substances of Bi, Te and Se, mixing, transferring into a clean closed reaction tube, and sealing the tube under vacuum with the vacuum degree of 10 Pa;
s2: swing melting: sealing the reaction tube, putting the reaction tube into a swinging furnace, melting at 750 ℃, swinging for 350 minutes at the same time, and then quickly cooling to room temperature, wherein the quick cooling is room temperature quenching or normal temperature water quenching;
s3: ball milling: ball-milling the block obtained in the step S2 into powder, wherein the ball-milling time is 9 minutes, and the rotating speed is 1200 rpm;
s4: sintering powder: putting the powder obtained in the step S3 into a stainless steel mold, and then putting the mold into a hot-pressing induction furnace; after vacuum pumping is carried out to below 10Pa, the temperature is gradually increased to the sintering temperature of 420 ℃; gradually increasing the pressure to 70Mpa, keeping the temperature and pressure for 30min when the molding pressure is reached, and finally cooling and releasing the pressure along with the furnace to obtain an n-type bismuth telluride-based sintered block;
s5: repeat S3 and S4: the ingot obtained in S4 was again ball-milled into powder and firedRepeating the above operation 3 times to obtain Bi2Te2.67Se0.28The n-type bismuth telluride-based sintered block.
Comparative example 3A nonstoichiometric sintered n-type bismuth telluride material was Bi2Te2.67Se0.28。
The preparation method of the nonstoichiometric n-type bismuth telluride sintered material in the embodiment is as follows:
s1: weighing: according to the chemical formula Bi2Te2.67Se0.28Proportionally weighing the elementary substances Bi, Te and Se, mixing, transferring into a clean closed reaction tube, and adding<Sealing the tube under vacuum of 10 Pa;
s2: swing melting: sealing the reaction tube, putting the reaction tube into a swinging furnace, melting at 750 ℃, swinging for 350 minutes at the same time, and then quickly cooling to room temperature, wherein the quick cooling is room temperature quenching or normal temperature water quenching;
s3: ball milling: ball-milling the block obtained in the step S2 into powder, wherein the ball-milling time is 9 minutes, and the rotating speed is 1200 rpm;
s4: sintering powder: putting the powder obtained in the step S3 into a stainless steel or graphite mold, and then putting the mold into a hot-pressing induction furnace or a plasma sintering furnace; after vacuum pumping is carried out to below 10Pa, the temperature is gradually increased to the sintering temperature of 420 ℃; then gradually increasing the pressure to 70Mpa, keeping the temperature and pressure for 30min when the molding pressure is reached, and finally cooling and releasing the pressure along with the furnace to obtain the chemical composition Bi2Te2.67Se0.28The n-type bismuth telluride-based sintered block.
This example is a comparative example to example 2, except that the step S5 of the present invention was not performed, and ball milling and sintering were performed only once.
Example 4A nonstoichiometric sintered n-type bismuth telluride material was Bi2Te2.64Se0.3。
The preparation method of the nonstoichiometric n-type bismuth telluride sintered material in the embodiment is as follows:
s1: weighing: according to the chemical formula Bi2Te2.64Se0.3Proportionally weighing the simple substances of Bi, Te and Se, mixing, and transferring to a cleanIn a closed reaction tube at<Sealing the tube under vacuum of 10 Pa;
s2: swing melting: sealing the reaction tube, putting the reaction tube into a swinging furnace, melting at 950 ℃, swinging for 15 minutes at the same time, and then quickly cooling to room temperature, wherein the quick cooling is room temperature quenching;
s3: ball milling: ball-milling the block obtained in the step S2 into powder, wherein the ball-milling time is 15 minutes, and the rotating speed is 1000 rpm;
s4: sintering powder: putting the powder obtained in the step S3 into a stainless steel mold, and then putting the mold into a plasma sintering furnace; after vacuum pumping is carried out to below 10Pa, the temperature is gradually increased to the sintering temperature of 480 ℃; gradually increasing the pressure to 100Mpa, keeping the temperature and pressure for 5min when the molding pressure is reached, and finally cooling and releasing the pressure along with the furnace to obtain an n-type bismuth telluride-based sintered block;
s5: repeat S3 and S4: the ingot obtained in S4 was again ball-milled into powder, and sintered, and the above operation was repeated 4 times to obtain Bi as a chemical composition2Te2.64Se0.3The n-type bismuth telluride-based sintered block.
Example 5A nonstoichiometric sintered n-type bismuth telluride material was Bi2Te2.7Se0.25。
The preparation method of the nonstoichiometric n-type bismuth telluride sintered material in the embodiment is as follows:
s1: weighing: according to the chemical formula Bi2Te2.7Se0.25Proportionally weighing elementary substances of Bi, Te and Se, mixing, transferring into a clean closed reaction tube, and adding<Sealing the tube under vacuum of 10 Pa;
s2: swing melting: putting the sealed reaction tube into a swing furnace, melting at 600 ℃, swinging for 720 minutes, and then quickly cooling to room temperature, wherein the quick cooling is room temperature quenching or normal temperature water quenching;
s3: ball milling: ball-milling the block obtained in the step S2 into powder, wherein the ball-milling time is 3 minutes, and the rotating speed is 1400 rpm;
s4: sintering powder: putting the powder obtained in the step S3 into a graphite mold, and then putting the mold into a hot-pressing induction furnace; after the vacuum pumping is carried out to below 10Pa, the temperature is gradually increased to the sintering temperature of 450 ℃; gradually increasing the pressure to 50Mpa, keeping the temperature and pressure for 60min when the molding pressure is reached, and finally cooling and releasing the pressure along with the furnace to obtain an n-type bismuth telluride-based sintered block;
s5: repeat S3 and S4: the ingot obtained in S4 was again ball-milled into powder and sintered, and the above operation was repeated 2 times to obtain Bi as a chemical composition2Te2.7Se0.25The n-type bismuth telluride-based sintered block.
Bi of other proportions2Te2.7-xSe0.3-yX is more than or equal to 0 and less than or equal to 0.06, y is more than or equal to 0 and less than or equal to 0.05, and x and y are not 0 at the same time, the invention is applicable to all proportions, and the preparation method can refer to examples 2 and 4-5.
And (3) comparison test:
first, hardness test
The test instrument: HV-1000 microhardness meter
The test steps are as follows: the Vickers hardness was measured 10 times under a load of 50N.
Second, thermoelectric performance test
1. Thermoelectric performance PF
The test instrument: ZEM-3
The test steps are as follows: the thermoelectric block was cut into 3.0mm by 12mm, and the electrical conductivity and seebeck coefficient of the material were tested to obtain a power factor.
2. Thermoelectric properties kappa
The test instrument: LFA467
The test steps are as follows: cutting thermoelectric blocks into
10mm by 2mm sheets, the thermal diffusivity of the material was tested to obtain thermal conductivity.
The test results are shown in FIGS. 1-4.
FIG. 1 shows: the left side is the hardness test result of the stoichiometric (conventional) base sample, and the right side is the hardness test result of the non-stoichiometric base sample of the present invention. As seen in the figure: compared with a conventional proportioning matrix sample, the dispersed vacancies introduced in the non-stoichiometric proportion improve the Vickers hardness of the material by 18 percent, which is similar to the strengthening mechanism of the traditional metal and alloy.
As can be seen from fig. 2 to 4, the increase of the dispersion distribution of vacancy point defects increases the phonon scattering probability, which is beneficial to the reduction of the lattice thermal conductivity. The anion vacancy effectively makes up the deficiency of the donor-like effect, induces and generates enough electrons, and enhances the carrier concentration; and the repeated ball milling and sintering processes for multiple times can effectively improve the preferred orientation of the bismuth telluride-based crystal grains, form high mobility, and improve the power factor by about 15 percent due to the non-stoichiometric proportion and the repeated ball milling and sintering mechanisms for multiple times. According to the thermoelectric figure of merit formula ZT ═ S2σT/κtotWherein S is a Seebeck coefficient, σ is an electric conductivity, T is an absolute temperature, and κtotFor the total thermal conductivity, the ZT value of the n-type bismuth telluride polycrystalline alloy obtained by the invention is remarkably improved by 15 percent, and the maximum ZT value is 1.22 at 375K. Therefore, in materials possessing significant anisotropy, the vacancy strengthening formed by the present invention is a good strategy for achieving both high thermoelectric performance and high mechanical properties.
It is to be understood that the foregoing examples, while indicating the preferred embodiments of the invention, are given by way of illustration and description, and are not to be construed as limiting the scope of the invention; it should be noted that, for a person skilled in the art, the above technical features can be freely combined, and several changes and modifications can be made without departing from the concept of the present invention, which all belong to the protection scope of the present invention; therefore, all equivalent substitutions and modifications made within the scope of the claims of the present invention should be covered by the claims of the present invention.
Claims (9)
1. A non-stoichiometric n-type bismuth telluride sintered material is characterized by having the following chemical formula: bi2Te2.7- xSe0.3-yWherein x is more than or equal to 0 and less than or equal to 0.06, y is more than or equal to 0 and less than or equal to 0.05, and x and y are not 0 at the same time.
2. A preparation method of a nonstoichiometric n-type bismuth telluride sintered material is characterized by comprising the following steps:
s1, weighing: according to the chemical formula Bi2Te2.7-xSe0.3-yWeighing and mixing the simple substances Bi, Te and Se according to the proportion, wherein x is more than or equal to 0 and less than or equal to 0.06, y is more than or equal to 0 and less than or equal to 0.05, and x and y are not 0 at the same time, transferring the mixed simple substances into a clean closed reaction tube, and sealing the tube under vacuum;
s2, swing melting: placing the sealed reaction tube into a rocking furnace, rocking and melting at high temperature, and then rapidly cooling to room temperature to obtain a block;
s3, ball milling: ball-milling the block obtained in the step S2 into powder;
s4, sintering powder: s3, placing the obtained powder into a mold, and sintering the powder in a hot-pressing induction furnace or a plasma sintering furnace to obtain an n-type bismuth telluride-based ingot casting block;
s5, repeats S3 and S4: and ball-milling the ingot casting block obtained in the step S4 into powder again according to the step S3, sintering again according to the step S4, and obtaining the n-type bismuth telluride-based sintered block after ball milling and sintering for multiple times.
3. The method for producing a nonstoichiometric n-type bismuth telluride sintered material according to claim 2, wherein in S1, the tube is sealed under a vacuum degree <10 Pa.
4. The method for preparing a nonstoichiometric sintered n-type bismuth telluride material according to claim 2, wherein in S2, the melting temperature is 600 to 950 ℃ and the rocking time is 15 to 720 minutes.
5. The method for preparing a non-stoichiometric n-type bismuth telluride sintered material as claimed in claim 2, wherein in S2, the rapid cooling is performed by room temperature quenching or room temperature water quenching.
6. The method of claim 2, wherein in S4, the mold is made of stainless steel or graphite.
7. The method for preparing a non-stoichiometric n-type bismuth telluride sintered material as in claim 2, wherein the ball milling time in S3 is 3-15 minutes, and the rotation speed is 1000-1400 rpm.
8. The method for preparing a non-stoichiometric n-type bismuth telluride sintered material as claimed in claim 2, wherein in S4, the sintering is: after the vacuum is pumped to below 10Pa, the temperature is gradually increased to the sintering temperature of 450-600 ℃, then the pressure is gradually increased to 50-100 Mpa, when the forming pressure is reached, the temperature and pressure are kept for 5-60 min, and finally the temperature is reduced and the pressure is relieved along with the furnace.
9. The method for producing a nonstoichiometric n-type bismuth telluride sintered material according to claim 2, wherein the number of times of repeating the S3 step and the S4 step in S5 is 2 to 4.
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