Bismuth telluride-based powder and preparation method thereof

Abstract

The invention provides bismuth telluride-based powder and a preparation method thereof, and belongs to the technical field of thermoelectric materials. According to the preparation method of the bismuth telluride-based powder, after the raw materials and the solvent are mixed, the second solution with the pH being 10-13 is prepared through the pH regulator, then the chelating agent is added to form the third solution, the third solution is subjected to high-energy ball milling, and the bismuth telluride-based powder with the high Cohn coefficient can be prepared; when the bismuth telluride-based powder is used for preparing the bismuth telluride-based thermoelectric material, the compression strength, the conductivity and the Seebeck coefficient of the bismuth telluride-based thermoelectric material can be improved.

Description

Technical Field

[0001] The present disclosure relates to the technical field of thermoelectric materials, and in particular to a bismuth telluride-based powder and a preparation method thereof. Background Art

[0002] Thermoelectric material conversion technology is an energy conversion technology based on the Seebeck effect and Peltier effect of materials to achieve direct conversion between thermal energy and electrical energy. It has two basic modes: thermoelectric power generation and thermoelectric cooling. Compared with traditional energy conversion methods, thermoelectric energy conversion devices have the advantages of simple structure, small size, no mechanical transmission parts, high reliability, no pollution, and no noise. As a green energy material with broad application prospects, it continues to attract the attention of the scientific community. Among them, bismuth telluride (Bi2Te3)-based thermoelectric materials are the most mature room-temperature thermoelectric materials in current applications.

[0003] In the current research, Bao Zhiyong et al. (patent CN114618534A) prepared bismuth telluride nanowires by hydrothermal synthesis; Hu Haoyang et al. (patent CN115073176A) also synthesized bismuth telluride-based materials by sealing tube-zone melting-swaying of tellurium, bismuth, selenium and antimony single-element materials, and then obtained bismuth telluride-based powder materials by wet ball milling and drying; Wu Yue et al. (patent CN115305567A) added different single elements into a high-frequency induction furnace according to the chemical mass ratio, melted and prepared alloy ingots, and then obtained bismuth telluride powder materials after jaw crushing and ball milling. In the above methods for preparing bismuth telluride-based powders, on the one hand, the technical route of obtaining bismuth telluride powder by centrifugal drying after hydrothermal synthesis not only has a long hydrothermal reaction time, but also due to the limitation of the high-temperature reactor, usually, the bismuth telluride material prepared by each batch of reaction is only tens of grams to hundreds of grams, which is difficult to meet the needs of commercial and large-scale production of bismuth telluride-based powders; on the other hand, after the alloy block is prepared by melting and mixing the single substances, the bismuth telluride-based powder is obtained by ball milling. The process flow is very complicated, the overall preparation process time is too long, and the powder making cost is high, which is difficult to meet the requirements of low-cost, industrial preparation of bismuth telluride-based powders. In addition, the bismuth telluride-based powder prepared by the hydrothermal method or the melting method is used to prepare bismuth telluride-based thermoelectric materials, and the resulting bismuth telluride-based thermoelectric materials have low compressive strength, electrical conductivity and Seebeck coefficient. Summary of the invention

[0004] The purpose of the present disclosure is to overcome the shortcomings of the prior art and provide a bismuth telluride-based powder and a preparation method thereof. The preparation method of the bismuth telluride-based powder of the present application can quickly synthesize the bismuth telluride-based powder, and the bismuth telluride-based powder of the present application is used to prepare a bismuth telluride-based thermoelectric material. The bismuth telluride-based thermoelectric material has high compressive strength, electrical conductivity and Seebeck coefficient.

[0005] To achieve the above object, the technical solution adopted by the present disclosure is: a method for preparing bismuth telluride-based powder, comprising the following steps:

[0006] A tellurium source and a bismuth source are first mixed according to a stoichiometric ratio to obtain a mixed powder;

[0007] The mixed powder and the solvent are mixed for a second time to obtain a first solution, a pH adjuster is added to the first solution to obtain a second solution with a pH of 10-13, and a chelating agent is added to the second solution for a third time to obtain a third solution;

[0008] The third solution is added into a ball mill, and high-energy ball milling, washing and drying are performed to obtain bismuth telluride-based powder, wherein the rotation speed of the high-energy ball mill is 1000-2000 rpm.

[0009] In some embodiments, the chelating agent is at least one of polyvinyl pyrrolidone, ethylenediaminetetraacetic acid, sodium lauryl sulfate, oxalic acid, glucose, and vitamin C.

[0010] In some embodiments, the ball-to-material ratio of the high-energy ball milling is 3-6:1;

[0011] In some embodiments, the high energy ball milling time is 15-30 min.

[0012] In some embodiments, the mass ratio of the mixed powder to the solvent is 1:3-6;

[0013] In some embodiments, the solvent is alcohol;

[0014] In some embodiments, the pH adjuster is at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, and ammonia water.

[0015] In some embodiments, the first mixing device is a mixer, the rotation cycle of the mixer is 1-5 min / cycle, the rotation angle is 180-360°; and / or the first mixing time is 10-30 min.

[0016] In some embodiments, the tellurium source is at least one of sodium tellurate, tellurium dioxide, tellurium powder, and potassium tellurate;

[0017] In some embodiments, the bismuth source is at least one of bismuth oxide, bismuth nitrate, and bismuth chloride.

[0018] In some embodiments, the mixed powder further includes at least one of an antimony source and a selenium source.

[0019] In some embodiments, the antimony source is at least one of antimony oxide, antimony chloride, and sodium antimonate;

[0020] In some embodiments, the selenium source is at least one of selenium oxide, sodium selenite, and selenium chloride.

[0021] On the other hand, a bismuth telluride-based powder is provided, wherein the bismuth telluride-based powder is prepared by the method for preparing the bismuth telluride-based powder.

[0022] In another aspect, a bismuth telluride-based thermoelectric material is provided, wherein the bismuth telluride-based thermoelectric material is obtained by hot pressing and sintering the bismuth telluride-based powder.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. The present application adopts an integrated high-energy ball milling method to prepare bismuth telluride-based powder, which can prepare bismuth telluride-based powder within 2-3 hours, simplifies the preparation process, shortens the preparation time, can meet the needs of large-scale preparation of bismuth telluride-based powder, and effectively reduces the time cost and economic cost of large-scale industrial preparation of bismuth telluride-based powder.

[0025] 2. The average particle size of the bismuth telluride-based powder prepared in this application is less than 100 μm, which is beneficial to reduce the pressure of hot pressing and sintering and shorten the time of hot pressing and sintering in the subsequent hot pressing and sintering process. It can achieve short-time hot pressing molding under low-pressure conditions, effectively reduce equipment requirements and pressing time, and improve efficiency.

[0026] 3. The bismuth telluride-based powder prepared in the present application has a highly oriented (015) crystal plane, which can improve the texturing characteristics of the bismuth telluride-based thermoelectric material, thereby improving the compressive strength, electrical conductivity and Seebeck coefficient of the bismuth telluride-based thermoelectric material.

[0027] 4. In the preparation method of bismuth telluride-based powder of the present application, the raw materials used are simple, and the preparation process is environmentally friendly and pollution-free, which complies with the policy of green and sustainable development. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a SEM image of the bismuth telluride-based powder of Example 1;

[0029] Figure 2 is the XRD pattern of the bismuth telluride-based powder of Example 1;

[0030] Figure 3 is a size distribution diagram of bismuth telluride-based powder in Example 1;

[0031] Figure 4 is a SEM image of the bismuth telluride-based powder of Example 2;

[0032] Figure 5 is the XRD pattern of the bismuth telluride-based powder of Example 2;

[0033] Figure 6 This is the size distribution diagram of the bismuth telluride-based powder in Example 2. DETAILED DESCRIPTION

[0034] In order to facilitate understanding of the present disclosure, the present disclosure will be described more fully below. However, the present disclosure can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the understanding of the disclosure of the present disclosure more thorough and comprehensive.

[0035] As used herein:

[0036] "Prepared from" is synonymous with "comprising." As used herein, the terms "comprising," "including," "having," "containing," or any other variation thereof, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises the listed elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

[0037] The conjunction "consisting of excludes any unspecified element, step, or component. If used in a claim, this phrase renders the claim closed-ended so that it does not include materials other than those described, except for conventional impurities associated therewith. When the phrase "consisting of" appears in a clause of the body of a claim rather than immediately following the subject matter, it limits only the elements described in that clause; other elements are not excluded from the claim as a whole.

[0038] When amount, concentration or other value or parameter is represented by range, preferred range or a series of upper preferred value and lower preferred value, this should be understood as specifically disclosing all ranges formed by any pairing of any range upper limit or preferred value and any range lower limit or preferred value, regardless of whether the range is disclosed separately. For example, when disclosing range "1-5", described range should be interpreted as including range "1-4", "1-3", "1-2", "1-2 and 4-5", "1-3 and 5" etc. When numerical range is described in this article, unless otherwise stated, the range is intended to include its end value and all integers and fractions within the range.

[0039] In these examples, parts and percentages are by mass unless otherwise indicated.

[0040] "Parts by mass" refers to the basic unit of measurement for expressing the mass ratio of multiple components. 1 part can represent any unit mass, such as 1g or 2.689g. If we say that the mass of component A is a parts and the mass of component B is b parts, it means the ratio of the mass of component A to the mass of component B is a:b. Alternatively, it means that the mass of component A is aK and the mass of component B is bK (K is an arbitrary number, indicating a multiple factor). It should not be misunderstood that, unlike the mass parts, the sum of the mass of all components is not limited to 100 parts.

[0041] "And / or" is used to indicate that one or both of the stated situations may occur, for example, A and / or B includes (A and B) and (A or B).

[0042] In order to solve the problem that bismuth telluride-based powders are difficult to prepare on a large scale and that bismuth telluride-based thermoelectric materials have low compressive strength, electrical conductivity and Seebeck coefficient.

[0043] In one aspect, the present disclosure provides a method for preparing bismuth telluride-based powder, comprising the following steps:

[0044] A tellurium source and a bismuth source are first mixed according to a stoichiometric ratio to obtain a mixed powder;

[0045] The mixed powder and the solvent are mixed for a second time to obtain a first solution, a pH adjuster is added to the first solution to obtain a second solution with a pH of 10-13, and a chelating agent is added to the second solution for a third time to obtain a third solution;

[0046] The third solution is added into a ball mill, and high-energy ball milling, washing and drying are performed to obtain bismuth telluride-based powder, wherein the rotation speed of the high-energy ball mill is 1000-2000 rpm.

[0047] For example, in different embodiments, the pH of the second solution may be, but is not limited to, 10, 10.2, 10.5, 10.7, 11, 11.3, 11.5, 11.7, 12, 12.2, 12.5, 12.8, or 13.

[0048] For example, in different embodiments, the rotation speed of the high energy ball mill can be but is not limited to 1000 rpm, 1100 rpm, 1200 rpm, 1300 rpm, 1400 rpm, 1500 rpm, 1600 rpm, 1700 rpm, 1800 rpm, 1900 rpm, and 2000 rpm.

[0049] In the present application, after mixing the powder and the solvent, a pH regulator is first used to prepare a second solution with a pH of 10-13, and then a chelating agent is added to form a third solution. The third solution is subjected to high-energy ball milling to prepare a bismuth telluride-based powder with a high Cohen coefficient. The bismuth telluride-based powder is used to prepare a bismuth telluride-based thermoelectric material, which can improve the compressive strength, electrical conductivity and Seebeck coefficient of the bismuth telluride-based thermoelectric material.

[0050] The applicant found that the pH of the second solution and the rotation speed of the high-energy ball mill have a great influence on the bismuth telluride-based powder and the bismuth telluride-based thermoelectric material. If the pH of the second solution is too low, it will lead to the occurrence of side reactions, so that some by-product impurities exist in the final sample, affecting the performance of the bismuth telluride-based thermoelectric material. If the pH of the second solution is too high, it will cause cations such as Bi and Te to precipitate and generate hydroxides or hydrolyze into oxides, making it difficult to obtain the target compound. If the rotation speed of the high-energy ball mill is too low, the raw materials cannot react with each other and the bismuth telluride-based powder cannot be obtained. If the rotation speed of the high-energy ball mill is too high, the preparation process will have high energy consumption and poor safety.

[0051] In some embodiments, the chelating agent is at least one of polyvinylpyrrolidone (PVP), ethylenediaminetetraacetic acid (EDTA), sodium dodecyl sulfate (SDS), oxalic acid, glucose, and vitamin C.

[0052] The chelating agent can improve the dispersion uniformity of the mixed powder in the third solution and promote the reaction between the raw materials. The applicant found that when the chelating agent is ethylenediaminetetraacetic acid and / or sodium dodecyl sulfate, the Cohen coefficient of the obtained bismuth telluride-based powder is higher, and the compressive strength, electrical conductivity and Seebeck coefficient of the bismuth telluride-based thermoelectric material are higher.

[0053] In some embodiments, the ball-to-material ratio of the high-energy ball milling is 3-6:1, for example, but not limited to 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1.

[0054] In some embodiments, the high-energy ball milling time is 15-30 min, for example, but not limited to 15 min, 17 min, 20 min, 23 min, 25 min, 28 min, 30 min.

[0055] In some embodiments, the mass ratio of the mixed powder to the solvent is 1:3-6; for example, it can be but is not limited to 1:3, 1:3.5, 1:4, 1:4.5, 1:5, 1:5.5, 1:6.

[0056] In some embodiments, the solvent is an alcohol; for example, in different embodiments, the alcohol is at least one of ethanol, propanol, and ethylene glycol.

[0057] In some embodiments, the pH adjuster is at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, and ammonia water.

[0058] In some embodiments, the first mixing device is a mixer, the rotation cycle of the mixer is 1-5 min / cycle, the rotation angle is 180-360°; and / or the first mixing time is 10-30 min.

[0059] The applicant has found that mixing the raw materials under the above conditions can improve the mixing uniformity between the raw materials, which is beneficial for their reaction during the high-energy ball milling process.

[0060] In some embodiments, the tellurium source is at least one of sodium tellurate, tellurium dioxide, tellurium powder, and potassium tellurate.

[0061] In some embodiments, the bismuth source is at least one of bismuth oxide, bismuth nitrate, and bismuth chloride.

[0062] In some embodiments, the mixed powder further includes at least one of an antimony source and a selenium source.

[0063] In some embodiments, the antimony source is at least one of antimony oxide, antimony chloride, and sodium antimonate.

[0064] In some embodiments, the selenium source is at least one of selenium oxide, sodium selenite, and selenium chloride.

[0065] Specifically, the present application does not impose any special restrictions on the washing solvent, as long as it can clean the ball-milled material. For environmental protection, the present application selects ethanol or water as the washing solvent. The present application does not impose any special restrictions on the number of washing times, and technicians in this field can adjust it according to actual needs, for example, 1-3 times.

[0066] Specifically, the present application does not impose any special restrictions on the drying method, as long as the material can be dried, such as vacuum drying, air drying, oven drying, microwave drying, freeze drying, reduced pressure drying, etc.; in order to shorten the preparation time of bismuth telluride-based powder, the present application selects vacuum drying as the drying method; preferably, the vacuum drying temperature is 60-120°C and the time is 10-30min.

[0067] On the other hand, a bismuth telluride-based powder is provided, wherein the bismuth telluride-based powder is prepared by the method for preparing the bismuth telluride-based powder.

[0068] In another aspect, a bismuth telluride-based thermoelectric material is provided, wherein the bismuth telluride-based thermoelectric material is obtained by hot pressing and sintering the bismuth telluride-based powder.

[0069] Specifically, the hot pressing sintering temperature is 400-500° C., the pressure is 30-50 MPa, and the time is 45-90 min.

[0070] In order to further illustrate the present invention, the preparation method of the bismuth telluride-based powder provided by the present invention is described in detail below in conjunction with the accompanying drawings and examples, but they should not be construed as limiting the scope of protection of the present invention.

[0071] Example 1

[0072] This embodiment provides a method for preparing bismuth telluride-based powder, comprising the following steps:

[0073] (1) adding bismuth nitrate and antimony chloride into a mixer at a stoichiometric ratio of Bi:Te=2:3, and mixing for 30 minutes at a rotation period of 1 minute / cycle and a rotation angle of 180° to obtain a mixed powder;

[0074] (2) performing a second mixing of the mixed powder and ethanol to obtain a first solution, adding sodium hydroxide to the first solution to obtain a second solution with a pH of 11, and adding sodium dodecyl sulfate to the second solution to perform a third mixing to obtain a third solution, wherein the mass ratio of the mixed powder to the ethanol is 1:3;

[0075] (3) The third solution was added to a ball mill, and high-energy ball milling was performed at a rotation speed of 1800 rpm for 10 min, with a ball-to-material ratio of 6:1; after the ball milling, the obtained material was washed with water for 3 times, and then vacuum dried at a temperature of 110° C. for 30 min to obtain a bismuth telluride-based powder.

[0076] Example 2

[0077] This embodiment provides a method for preparing bismuth telluride-based powder, comprising the following steps:

[0078] (1) adding bismuth nitrate, sodium tellurite and antimony chloride into a mixer according to the stoichiometric ratio of Bi:Sb:Te=1:3:6, and mixing for 10 minutes under the condition that the mixer rotates at a cycle of 5 minutes / cycle and a rotation angle of 360° to obtain a mixed powder;

[0079] (2) performing a second mixing of the mixed powder and ethanol to obtain a first solution, adding sodium hydroxide to the first solution to obtain a second solution with a pH of 11, and adding sodium dodecyl sulfate to the second solution to perform a third mixing to obtain a third solution, wherein the mass ratio of the mixed powder to the ethanol is 1:6;

[0080] (3) The third solution was added to a ball mill, and high-energy ball milling was performed at a rotation speed of 1800 rpm for 30 minutes, with a ball-to-material ratio of 3:1; after the ball milling, the obtained material was washed with ethanol for 3 times, and then vacuum dried at 90° C. for 30 minutes to obtain a bismuth telluride-based powder.

[0081] Example 3

[0082] This embodiment provides a method for preparing bismuth telluride-based powder, comprising the following steps:

[0083] (1) adding bismuth nitrate, sodium tellurite and antimony chloride into a mixer according to the stoichiometric ratio of Bi:Sb:Te=1:3:6, and mixing for 20 minutes under the condition that the mixer rotates at a cycle of 3 minutes / cycle and a rotation angle of 180° to obtain a mixed powder;

[0084] (2) performing a second mixing of the mixed powder and ethanol to obtain a first solution, adding sodium hydroxide to the first solution to obtain a second solution with a pH of 11, and adding sodium dodecyl sulfate to the second solution to perform a third mixing to obtain a third solution, wherein the mass ratio of the mixed powder to the ethanol is 1:4;

[0085] (3) The third solution was added to a ball mill, and high-energy ball milling was performed at a rotation speed of 1800 rpm for 20 minutes, with a ball-to-material ratio of 5:1; after the ball milling, the obtained material was washed with water for 3 times, and then vacuum dried at a temperature of 110° C. for 30 minutes to obtain a bismuth telluride-based powder.

[0086] Example 4

[0087] This embodiment provides a method for preparing bismuth telluride-based powder. The method for preparing bismuth telluride-based powder in this embodiment is different from that in Example 3 only in that the pH of the second solution is different. In this embodiment, the pH of the second solution is 10.

[0088] Example 5

[0089] This embodiment provides a method for preparing bismuth telluride-based powder. The method for preparing bismuth telluride-based powder in this embodiment is different from that in Example 3 only in that the pH of the second solution is different. In this embodiment, the pH of the second solution is 12.

[0090] Example 6

[0091] This embodiment provides a method for preparing bismuth telluride-based powder. The method for preparing bismuth telluride-based powder in this embodiment is different from that in Example 3 only in that the pH of the second solution is different. In this embodiment, the pH of the second solution is 13.

[0092] Example 7

[0093] This embodiment provides a method for preparing bismuth telluride-based powder. The difference between the method for preparing bismuth telluride-based powder in this embodiment and that in Example 3 is that the chelating agent is different. The chelating agent in this embodiment is oxalic acid.

[0094] Example 8

[0095] This embodiment provides a method for preparing bismuth telluride-based powder. The difference between the method for preparing bismuth telluride-based powder in this embodiment and that in Example 3 is that the chelating agent is different. The chelating agent in this embodiment is glucose.

[0096] Example 9

[0097] This embodiment provides a method for preparing bismuth telluride-based powder. The difference between the method for preparing bismuth telluride-based powder in this embodiment and that in Example 3 is that the chelating agent is different. The chelating agent in this embodiment is vitamin C.

[0098] Example 10

[0099] This embodiment provides a method for preparing bismuth telluride-based powder. The difference between the method for preparing bismuth telluride-based powder in this embodiment and that in Example 3 is that the chelating agent is different. The chelating agent in this embodiment is polyvinyl pyrrolidone.

[0100] Embodiment 11

[0101] This embodiment provides a method for preparing bismuth telluride-based powder. The method for preparing bismuth telluride-based powder in this embodiment is different from that in Example 3 only in that the rotation speed of the high-energy ball mill is different. In this embodiment, the rotation speed of the high-energy ball mill is 1400 rpm.

[0102] Example 12

[0103] This embodiment provides a method for preparing bismuth telluride-based powder. The method for preparing bismuth telluride-based powder in this embodiment is different from that in Example 3 only in that the rotation speed of the high-energy ball mill is different. In this embodiment, the rotation speed of the high-energy ball mill is 1000 rpm.

[0104] Embodiment 13

[0105] This embodiment provides a method for preparing bismuth telluride-based powder. The difference between the method for preparing bismuth telluride-based powder in this embodiment and that in Example 3 is that the rotation speed of the high-energy ball mill is different. In this embodiment, the rotation speed of the high-energy ball mill is 2000 rpm.

[0106] Comparative Example 1

[0107] This comparative example provides a method for preparing bismuth telluride-based powder. The difference between the method for preparing bismuth telluride-based powder in this comparative example and that in Example 3 is that the rotation speed of the high-energy ball mill is different. In this example, the rotation speed of the high-energy ball mill is 800 rpm.

[0108] Comparative Example 2

[0109] This comparative example provides a method for preparing bismuth telluride-based powder. The difference between the method for preparing bismuth telluride-based powder in this comparative example and that in Example 3 is that the chelating agent is different, and the chelating agent in this comparative example is aminocarboxylic acid.

[0110] Comparative Example 3

[0111] This comparative example provides a method for preparing bismuth telluride-based powder. The difference between the method for preparing bismuth telluride-based powder in this comparative example and that in Example 3 is that the pH of the second solution is different. In this comparative example, the pH of the second solution is 8.

[0112] Comparative Example 4

[0113] This comparative example provides a method for preparing bismuth telluride-based powder. The difference between the method for preparing bismuth telluride-based powder in this comparative example and that in Example 3 is that the pH of the second solution is different. In this comparative example, the pH of the second solution is 14.

[0114] Comparative Example 5

[0115] This comparative example provides a method for preparing a bismuth telluride-based powder. The difference between the method for preparing the bismuth telluride-based powder in this comparative example and that in Example 3 is that step (2) is different. Step (2) in this comparative example is: mixing the mixed powder and ethanol for a second time to obtain a first solution, adding sodium dodecyl sulfate to the first solution for a third mixing to obtain a second solution, wherein the mass ratio of the mixed powder to the ethanol is 1:4.

[0116] Comparative Example 6

[0117] This comparative example provides a method for preparing bismuth telluride-based powder, comprising the following steps:

[0118] (1) According to the stoichiometric ratio of Bi:Sb:Te=1:2:6, bismuth nitrate, sodium tellurite and antimony chloride are placed in a graphite crucible with a boron nitride top cover in order from the lowest melting point to the highest melting point;

[0119] (2) Place the graphite crucible filled with raw materials in a vacuum high-frequency electromagnetic induction heating furnace and evacuate the cavity to a vacuum degree of 10 -5 Torr, argon gas was introduced for protection and the temperature was raised to 1023K at a rate of 60K / min, and the temperature was kept for 60min. During the holding process, a boron nitride stirring paddle was used for mechanical stirring at a stirring rate of 100rpm. The bismuth telluride alloy ingot was obtained by cooling to room temperature with the furnace, and the surface of the ingot was cleaned with a steel brush;

[0120] (3) The alloy ingot is crushed into small pieces by a jaw crusher and then placed in a quartz tube and sealed under vacuum at a vacuum degree of 10 -6After 10000 ℃, the quartz tube containing the material is placed in a vertical zone furnace and pulled at 1123K at a speed of 2mm / min to grow into a single crystal or quasi-single crystal bismuth telluride rod with a diameter of 30mm;

[0121] (4) The obtained single crystal rod is placed in a jaw crusher for crushing, the diameter of the jaw plate outlet is set to 2 mm, and the crushing speed is 200 times / min. The obtained fine particles or blocks are then placed in a ball mill, the ball mill is evacuated to vacuum and argon is introduced as a protective atmosphere, and then the ball mill is placed in a planetary ball mill for grinding, the ball-to-material ratio is 3:1, the ball milling time is 50 min, and the rotation speed is 240 rpm to obtain bismuth telluride-based powder.

[0122] Application Examples

[0123] This application example provides a method for preparing a bismuth telluride-based thermoelectric material, comprising the following steps:

[0124] The bismuth telluride-based powders obtained in the examples and comparative examples were respectively placed in molds and vacuumed to 1.0×10 -3 The bismuth telluride-based thermoelectric material was obtained by hot pressing and sintering for 60 min under the conditions of 50 MPa, 50 MPa pressure and 420°C temperature.

[0125] Performance Testing

[0126] The bismuth telluride-based powders obtained in the examples and comparative examples, and the bismuth telluride-based thermoelectric materials obtained in the application examples were subjected to performance tests, and the test methods were as follows:

[0127] (1) Phase: tested by X-ray diffractometer;

[0128] (2) Cohen coefficient: tested by electron backscatter diffractometer;

[0129] (3) Average particle size: tested by laser particle size analyzer according to standard GB / T 19077-2016;

[0130] (4) Compression strength: tested by universal testing machine in accordance with standard GB / T 7314-2017;

[0131] (5) Electrical conductivity and Seebeck coefficient: measured at 25°C using a ZEM-3 thermoelectric performance analysis system.

[0132] The test results are shown in Table 1.

[0133] Table 1

[0134]

[0135]

[0136] From the experimental data in Table 1, it can be seen that the Cohen coefficient of the bismuth telluride-based powder disclosed in the present invention is greater than 0.6. The bismuth telluride-based thermoelectric material prepared by using the bismuth telluride-based powder disclosed in the present invention has a compressive strength of 100-125 MPa and an electrical conductivity of (1.02-1.38)×10 5 S / m, and the Seebeck coefficient is 180-219μV / K.

[0137] By comparing Examples 3-6 and Comparative Examples 3-4, it can be seen that when the pH of the second solution is too low, impurities may be present in the bismuth telluride-based powder, resulting in a decrease in the compressive strength, electrical conductivity and Seebeck coefficient of the bismuth telluride-based thermoelectric material.

[0138] It can be seen from Comparative Example 3, Examples 7-10 and Comparative Example 2 that the chelating agent is at least one of polyvinylpyrrolidone (PVP), ethylenediaminetetraacetic acid (EDTA), sodium dodecyl sulfate (SDS), oxalic acid, glucose, and vitamin C, which can effectively improve the compressive strength, electrical conductivity and Seebeck coefficient of bismuth telluride-based thermoelectric materials, especially oxalic acid, glucose, and vitamin C.

[0139] By comparing Example 3, Examples 11-13 and Comparative Example 1, it can be seen that if the rotation speed of the high-energy ball mill is too low, impurities will be present in the bismuth telluride-based powder, resulting in a decrease in the compressive strength, electrical conductivity and Seebeck coefficient of the bismuth telluride-based thermoelectric material.

[0140] Finally, it should be noted that the above embodiments are used to illustrate the technical solution of the present disclosure rather than to limit the protection scope of the present disclosure. Although the present disclosure has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solution of the present disclosure can be modified or replaced by equivalents without departing from the essence and scope of the technical solution of the present disclosure.

Claims

1. A method for preparing bismuth telluride-based powder, characterized in that: The following steps are involved: A tellurium source and a bismuth source are first mixed according to a stoichiometric ratio to obtain a mixed powder; The mixed powder and the solvent are mixed for a second time to obtain a first solution, a pH adjuster is added to the first solution to obtain a second solution with a pH of 10-13, and a chelating agent is added to the second solution for a third time to obtain a third solution; The third solution is added into a ball mill, and high-energy ball milling, washing and drying are performed to obtain bismuth telluride-based powder, wherein the rotation speed of the high-energy ball mill is 1000-2000 rpm.

2. The method for preparing bismuth telluride-based powder according to claim 1, characterized in that: The chelating agent is at least one of polyvinyl pyrrolidone, ethylenediaminetetraacetic acid, sodium lauryl sulfate, oxalic acid, glucose and vitamin C.

3. The method for preparing bismuth telluride-based powder according to claim 1, characterized in that: The ball-to-material ratio of the high-energy ball mill is 3-6:1; And / or, the high energy ball milling time is 15-30 min.

4. The method for preparing bismuth telluride-based powder according to claim 1, characterized in that: The mass ratio of the mixed powder to the solvent is 1:3-6; and / or, the solvent is alcohol; And / or, the pH adjuster is at least one of sodium hydroxide, potassium hydroxide, sodium carbonate, sodium bicarbonate, and ammonia water.

5. The method for preparing bismuth telluride-based powder according to claim 1, characterized in that: The first mixing device is a mixer, the rotation cycle of the mixer is 1-5 min / cycle, and the rotation angle is 180-360°; and / or the first mixing time is 10-30 min.

6. The method for preparing bismuth telluride-based powder according to claim 1, characterized in that: The tellurium source is at least one of sodium tellurate, tellurium dioxide, tellurium powder, and potassium tellurate; And / or, the bismuth source is at least one of bismuth oxide, bismuth nitrate and bismuth chloride.

7. The method for preparing bismuth telluride-based powder according to claim 1, characterized in that: The mixed powder also includes at least one of an antimony source and a selenium source.

8. The method for preparing bismuth telluride-based powder according to claim 7, characterized in that: The antimony source is at least one of antimony oxide, antimony chloride and sodium antimonate; And / or, the selenium source is at least one of selenium oxide, sodium selenite and selenium chloride.

9. A bismuth telluride-based powder, characterized in that: The bismuth telluride-based powder is prepared by the method for preparing the bismuth telluride-based powder according to any one of claims 1 to 8.

10. A bismuth telluride-based thermoelectric material, characterized in that: The bismuth telluride-based thermoelectric material is obtained by hot pressing and sintering the bismuth telluride-based powder as claimed in claim 9.

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