Mg3Bi2-based thermoelectric material and preparation method thereof
By selecting magnesium raw materials of specific orientations and sintering with bismuth, Mg3Bi2-based thermoelectric materials were prepared, which solved the problem of low lateral thermoelectric properties of existing thermoelectric materials, achieved high lateral thermoelectric properties under specific conditions, and promoted the efficient conversion of thermal energy and electrical energy.
Patent Information
- Application Number
- CN202411695237.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-11-25
- Publication Date
- 2025-04-11
AI Technical Summary
The low lateral thermoelectric potential and power factor of existing thermoelectric materials limit their application potential in lateral thermoelectric energy conversion technology.
By selecting magnesium raw materials with a relative strength ratio of more than 50% of the (002) peak to (101) peak to sinter with bismuth, Mg3Bi2-based thermoelectric material was prepared, and mechanical alloying and discharge plasma sintering technology was used.
The prepared Mg3Bi2-based thermoelectric material exhibits excellent lateral thermoelectric properties under specific conditions, with a magnetoresistance of up to 3342-5089%, which helps to achieve efficient conversion of thermal energy and electrical energy.
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Figure CN119797386A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of thermoelectric materials, and in particular to a Mg 3 Bi 2 Based thermoelectric material and preparation method thereof. Background Art
[0002] Traditional thermoelectric technology still has many shortcomings. On the one hand, the energy conversion efficiency of the thermoelectric effect is determined by the dimensionless quality factor (ZT = S2σT / κ, where S is the Seebeck coefficient, σ is the electrical conductivity, T is the absolute temperature, and κ is the thermal conductivity), and there is a strong coupling relationship between the various transport parameters. Realizing the coordinated regulation of electric and thermal transmission has always been a historical problem. On the other hand, the efficiency of thermoelectric devices is closely related to the contact interface between the metal electrode and the thermoelectric arm, and the preparation process of traditional thermoelectric devices is complicated, which not only limits the efficiency of thermoelectric devices, but also greatly increases the production cost. Therefore, the electroacoustic coupling effect at the material level and the complex contact interface problems at the device level make improving the energy conversion efficiency of thermoelectric technology a very challenging task.
[0003] The emergence of lateral thermoelectric technology provides a new approach to solving the above problems. Based on the Nernst effect, lateral thermoelectric technology uses magnetic fields as a new means of regulation to drive carriers and phonons to travel in different directions, thereby decoupling electrical and thermal transport and achieving independent regulation of electrical and thermal conductivity. In addition, lateral thermoelectric devices can be made of one type of material and do not require P / N pairing, which greatly reduces interface problems in the device manufacturing process. Therefore, lateral thermoelectric technology is expected to achieve an improvement in thermoelectric conversion efficiency. In existing studies, Mg 3 Bi 2 As a promising transverse thermoelectric material, it has attracted extensive attention. It exhibits a linear non-saturated magnetoresistance of 940% under a magnetic field of 14 Tesla, and the maximum transverse thermoelectric potential and power factor reach 126 μV / K and 2182 μWm at 13.5 K and 6 Tesla, respectively. -1 K -2 However, the lateral thermoelectric potential and power factor of such materials are still relatively low, which largely limits their potential for future applications in lateral thermoelectric energy conversion technology.
[0004] Therefore, the prior art needs to be further improved and enhanced. Summary of the invention
[0005] In view of the above-mentioned deficiencies in the prior art, the object of the present invention is to provide a Mg 3 Bi 2Thermoelectric material and its preparation method. The purpose is to select magnesium metal elements, select magnesium with strong (002) orientation growth as raw material, and sinter it with bismuth to obtain Mg 3 Bi 2 The base thermoelectric material has excellent lateral thermoelectric performance.
[0006] The above object of the present invention is achieved through the following technical scheme: a Mg 3 Bi 2 A method for preparing a thermoelectric material, comprising the following steps:
[0007] Selecting a magnesium-containing raw material whose relative intensity ratio of the (002) peak to the (101) peak is greater than 50% as the magnesium raw material;
[0008] Weigh the magnesium raw material and bismuth according to a stoichiometric ratio, mix the magnesium raw material and bismuth, and then ball-mill them to obtain a mixed powder;
[0009] The mixed powder is sintered to obtain the Mg 3 Bi 2 Based thermoelectric materials.
[0010] The following are preferred technical solutions of the present invention, but are not intended to limit the technical solutions provided by the present invention. Through the following preferred technical solutions, the objectives and beneficial effects of the present invention can be better achieved and realized.
[0011] As a preferred technical solution, the Mg 3 Bi 2 A method for preparing a thermoelectric material based on a magnesium-containing raw material, wherein the magnesium raw material is selected with a relative intensity ratio of (002) peak to (101) peak greater than 50%, comprising:
[0012] preparing several magnesium-containing raw materials into corresponding blocks respectively, performing X-ray diffraction test on the blocks to obtain XRD diffraction patterns;
[0013] The XRD diffraction pattern is analyzed, and a magnesium-containing raw material having a relative intensity ratio of (002) peak to (101) peak greater than 50% is selected as the magnesium raw material.
[0014] As a preferred technical solution, the Mg 3 Bi 2 A method for preparing a thermoelectric material based on magnesium, wherein the magnesium raw material and the bismuth are mixed and then ball-milled to obtain a mixed powder, comprising:
[0015] Mixing all of the magnesium raw material and part of the bismuth in an inert atmosphere and then performing a pre-crushing treatment;
[0016] After the pre-crushing is completed, the remaining bismuth is added and ball milling is continued to obtain a mixed powder.
[0017] As a preferred technical solution, the Mg 3 Bi 2 A method for preparing a thermoelectric material based on magnesium, wherein in the pre-crushing process, the mass ratio of magnesium to bismuth is 1:0.5-1.5.
[0018] As a preferred technical solution, the Mg 3 Bi 2 The preparation method of the thermoelectric material comprises sintering the mixed powder, comprising: sintering at a sintering temperature of 600-800° C. and an axial pressure of 30-80 MPa.
[0019] As a preferred technical solution, the Mg 3 Bi 2 The method for preparing a thermoelectric material comprises the following steps: the pre-crushing time is 1.5-3 hours.
[0020] As a preferred technical solution, the Mg 3 Bi 2 The method for preparing a thermoelectric material comprises the following steps: the ball milling is continued for 7 to 10 hours and the rotation speed during the ball milling is 1500 to 1725 r / min.
[0021] As a preferred technical solution, the Mg 3 Bi 2 A method for preparing a thermoelectric material, wherein during the sintering process, the heating rate is 80-120°C / min.
[0022] In the second aspect, a Mg 3 Bi 2 Based thermoelectric material, wherein the Mg 3 Bi 2 The base thermoelectric material is prepared by the preparation method described above.
[0023] As a preferred technical solution, the Mg 3 Bi 2 Based thermoelectric material, wherein the Mg 3 Bi 2 The base thermoelectric material has a magnetoresistance of 3342-5089% at 2K temperature and 14 Tesla magnetic field.
[0024] Beneficial effects: Compared with the prior art, the preparation method provided by the present invention uses the Mg metal raw material with preferential orientation in the (002) direction as a template, combines mechanical alloying and sintering technology, and prepares Mg with preferential orientation in the (002) direction. 3 Bi2 This method is expected to provide a reference for the preparation of preferentially oriented structures of other Mg-based compounds.
[0025] The mechanical alloying and sintering techniques used in the preparation method provided by the present invention are common material processing methods and are easy to implement in large-scale production. This not only reduces production costs, but also improves production efficiency, which is conducive to the wide application of materials in practice. By rationally combining these methods, the preparation of the material of the present invention can be achieved on the basis of existing production equipment and processes without investing a large amount of new equipment and new technology research and development costs. The prepared Mg 3 Bi 2 The base thermoelectric material has excellent transverse thermoelectric performance (magnetoresistance is 3342-5089% at 2K temperature and 14 Tesla magnetic field). BRIEF DESCRIPTION OF THE DRAWINGS
[0026] Figure 1 The present invention provides a Mg 3 Bi 2 Schematic diagram of the layered crystal structure of the material;
[0027] Figure 2 is the XRD diffraction pattern of the preferentially oriented Mg raw material;
[0028] Figure 3 It is the preferred orientation Mg 3 Bi 2 XRD diffraction pattern of base thermoelectric materials;
[0029] Figure 4 Is the same preferred orientation Mg 3 Bi 2 Schematic diagram of the magnetoresistance of the base thermoelectric material;
[0030] Figure 5 It is the preferred orientation Mg 3 Bi 2 Thermoelectric properties of based thermoelectric materials. DETAILED DESCRIPTION
[0031] The present invention provides a Mg 3 Bi 2 In order to make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail below. It should be understood that the specific embodiments described here are only used to explain the present invention and are not used to limit the present invention.
[0032] In addition, the features, operations or characteristics described in the specification can be combined in any appropriate manner to form various implementation methods. At the same time, the steps or actions in the method description can also be interchanged or adjusted in a manner that is obvious to those skilled in the art. Therefore, the various sequences in the specification and the drawings are only for the purpose of clearly describing a certain embodiment and do not mean a necessary sequence, unless otherwise specified that a certain sequence must be followed. The serial numbers themselves, such as "first", "second", etc., assigned to the components herein are only used to distinguish the objects described and do not have any order or technical meaning.
[0033] The present invention provides a Mg 3 Bi 2 A method for preparing a thermoelectric material comprises the following steps:
[0034] S100, selecting a magnesium-containing raw material having a relative intensity ratio of (002) peak to (101) peak greater than 50% as a magnesium raw material.
[0035] Specifically, appropriate amounts of different magnesium raw materials are taken, loaded into a 12.7 mm mold, and prepared into magnesium blocks at 180°C and 30-50 MPa axial pressure, and XRD tests are performed on the blocks to obtain XRD diffraction patterns. The obtained XRD diffraction patterns are analyzed, and magnesium raw materials with a relative intensity ratio of (002) peak to (101) peak greater than 50% are taken as the preparation raw materials. By selecting magnesium with a higher (002) peak intensity as the raw material, when mixed and sintered with bismuth, Mg with excellent transverse thermoelectric performance can be obtained. 3 Bi 2 Based thermoelectric materials.
[0036] S200, weighing the magnesium raw material and bismuth according to a stoichiometric ratio, mixing the magnesium raw material and the bismuth, and then ball-milling to obtain a mixed powder.
[0037] Specifically, according to the corresponding stoichiometric ratio (Mg 3 Bi 2 ) Calculate the mass of magnesium and bismuth required as raw materials, weigh all magnesium and about 3.2g of Bi with an electronic balance in a glove box with protective gas (argon) and place them in a high-energy ball mill, and pre-crush them for 1.5-3 hours under argon protection. Through the pre-crushing operation, magnesium and bismuth can be mixed more evenly and fully.
[0038] After the pre-crushing stage, the remaining bismuth is placed in a high-energy ball mill and subjected to subsequent high-energy ball milling for 7-10 hours to obtain Mg 3 Bi 2Powder. Among them, there are 1-3 large stainless steel balls, 2-4 small stainless steel balls, and the rotation speed is 1500r / min-1725r / min. The ball milling process uses high-energy ball milling to fully mix the raw materials and form a dense material structure, which is beneficial to improving the thermoelectric performance of the material.
[0039] S300, sintering the mixed powder to obtain the Mg 3 Bi 2 Based thermoelectric materials.
[0040] Specifically, appropriate powders are weighed in a glove box, and sintered into blocks by spark plasma sintering at a sintering temperature of 600-800°C, a holding time of 0-20min, a heating rate of 80-120°C / min, and an axial pressure of 30-80MPa. Through these treatment methods, the microstructure of the material can be effectively improved to obtain preferentially oriented Mg 3 Bi 2 Based on thermoelectric materials, the carrier mobility is improved, thereby improving the lateral thermoelectric performance of the material.
[0041] Based on the same inventive concept, the present invention also provides a Mg 3 Bi 2 Based thermoelectric material, wherein the Mg 3 Bi 2 The base thermoelectric material is prepared by the preparation method described above.
[0042] The specific preparation method has been described in detail above and will not be repeated here.
[0043] The prepared Mg 3 Bi 2 The base thermoelectric material has excellent transverse thermoelectric performance, with a magnetoresistance of 3342-5089% at 2K temperature and 14 Tesla magnetic field.
[0044] The thermoelectric material is expected to achieve efficient conversion of heat and electric energy, improve energy utilization efficiency, and reduce energy waste. The mechanical alloying and spark plasma sintering techniques used in the preparation method are common material processing methods, which are easy to achieve large-scale production. This not only reduces production costs, but also improves production efficiency, which is conducive to the wide application of materials in practice. By rationally combining these methods, the preparation of the material of the present invention can be achieved on the basis of existing production equipment and processes, without investing a large amount of new equipment and new technology research and development costs.
[0045] The material of the present invention has broad application prospects in the fields of energy recovery and waste heat utilization. For example, in the industrial waste heat recovery system, waste heat can be efficiently converted into electrical energy to reduce energy waste. A large amount of waste heat will be generated in the industrial production process. If this waste heat can be effectively used to generate electricity, the energy utilization efficiency will be greatly improved. In the heat dissipation management of electronic equipment, its thermoelectric properties are used to achieve better temperature control and improve the stability and service life of the equipment. Electronic equipment will generate heat during operation. If the heat cannot be dissipated in time, it will affect the performance and service life of the equipment. The material of the present invention can convert heat into electrical energy through the thermoelectric effect, and at the same time play a role in heat dissipation, thereby improving the stability and service life of the equipment.
[0046] The following is a specific preparation example to illustrate the Mg 3 Bi 2 The thermoelectric material and its preparation method are further explained.
[0047] Example 1
[0048] Three different magnesium raw materials were prepared into magnesium blocks at 180°C and 45 MPa axial pressure for XRD testing, and the XRD diffraction patterns of the three different magnesium raw materials were obtained, such as Figure 2 The three XRD diffraction patterns were analyzed, the relative intensity ratio of the (002) peak to the (101) peak was calculated, and the relative intensity of the (002) peak in the figure was ranked. Figure 2 Describes the Mg metal raw materials with different (002) preferred orientations. The Mg raw materials with different preferred orientations have an important effect on the synthesis of preferred oriented Mg. 3 Bi 2 The impact of thermoelectric materials is huge.
[0049] Select magnesium raw material No. 2 with strong orientation growth in the (002) direction. 3 Bi 2 The required raw materials were weighed according to the chemical stoichiometry. First, all magnesium and about 3.2g of bismuth were weighed with an electronic balance in a glove box with a protective gas (argon) environment and placed in a high-energy ball mill for 3 hours of pre-crushing. After the pre-crushing stage, the remaining bismuth was placed in a high-energy ball mill and continued to be high-energy ball milled for 7 hours to obtain Mg 3 Bi 2 powder.
[0050] Mg 3 Bi 2 The powder was loaded into a graphite mold and sintered at 710°C for 5 minutes under a pressure of 50 MPa using spark plasma sintering (SPS) technology. During the sintering process, the heating rate was controlled at 100°C / min to ensure uniform heating of the material and obtain polycrystalline Mg with preferential orientation. 3 Bi2 Materials, responding to XRD diffraction patterns such as Figure 3 shown. Figure 3 The middle picture shows the Mg prepared based on different preferred orientation Mg raw materials. 3 Bi 2 Preferred orientation behavior of base thermoelectric materials in the (002) direction.
[0051] The performance of the prepared material was tested, and the results showed that the preferentially oriented Mg 3 Bi 2 The material has a magnetic resistance of 3342% at 2K temperature and 14 Tesla magnetic field. Figure 4 As shown, Figure 4 By comparing different preferred orientations of Mg 3 Bi 2 The magnetoresistance of the thermoelectric material shows that the preferred orientation of the material of the present invention is obtained by the aforementioned synthesis and preparation process. 3 Bi 2 The magnetic field response capability of the base material is significantly improved. At 28K temperature and 14Tesla magnetic field, the transverse thermoelectric potential can reach 175μV / K. Figure 5 As shown, it meets the requirements of the present invention. Figure 5 The Mg prepared based on the preferentially oriented Mg raw material 3 Bi 2 The thermoelectric properties of the based thermoelectric materials verify the effectiveness of the invention.
[0052] Example 2
[0053] Select magnesium raw material No. 3 with strong orientation growth in the (002) direction. 3 Bi 2 The required raw materials were weighed according to the chemical stoichiometry. First, all magnesium and about 3.2g of bismuth were weighed with an electronic balance in a glove box with a protective gas (argon) environment and placed in a high-energy ball mill for 2 hours of pre-crushing. After the pre-crushing stage, the remaining bismuth was placed in a high-energy ball mill and continued to be high-energy ball milled for 8 hours to obtain Mg 3 Bi 2 powder.
[0054] Mg 3 Bi 2 The powder was loaded into a graphite mold and sintered at 700°C for 10 minutes under a pressure of 30 MPa using spark plasma sintering (SPS) technology. During the sintering process, the heating rate was controlled at 120°C / min to ensure uniform heating of the material and obtain polycrystalline Mg with preferential orientation. 3 Bi 2 Materials, whose response XRD diffraction patterns are as follows Figure 3 shown.
[0055] The performance of the prepared material was tested, and the results showed that the preferentially oriented Mg 3 Bi 2 The magnetic resistance of the material can reach 5089% at 2K temperature and 14 Tesla magnetic field. Figure 4 As shown, it is much higher than the reported non-preferentially oriented Mg 3 Bi 2 The material has a magnetic resistance of 940%, which meets the requirements of the present invention.
[0056] In summary, the present invention provides a Mg 3 Bi 2 Thermoelectric material and preparation method thereof, the method comprising: selecting a magnesium-containing raw material with a relative intensity ratio of (002) peak to (101) peak greater than 50% as a magnesium raw material; weighing the magnesium raw material and bismuth according to a stoichiometric ratio, mixing the magnesium raw material and the bismuth, and then ball milling to obtain a mixed powder; sintering the mixed powder to obtain the Mg 3 Bi 2 Compared with the prior art, the present invention proposes a new method for preparing preferentially oriented Mg 3 Bi 2 The method uses a Mg metal raw material with a preferred orientation in the (002) direction as a template, combines mechanical alloying and spark plasma sintering technology to prepare a Mg with a preferred orientation in the (002) direction. 3 Bi 2 Based thermoelectric material, the Mg 3 Bi 2 The Mg-based thermoelectric material has excellent transverse thermoelectric performance. This method is expected to provide a reference for the preparation of preferred orientation structures of other Mg-based compounds.
[0057] The preferred orientation Mg of the present invention 3 Bi 2 After the above treatment, the base thermoelectric material has high transverse thermoelectric performance, including significant improvement in transverse thermoelectric potential and transverse power factor under specific conditions compared with existing materials. For example, under certain temperature and magnetic field conditions, the magnetic resistance is increased to 3342%, and the transverse thermoelectric potential can be increased to 175μV / K, which is expected to achieve efficient conversion of thermal energy and electrical energy, improve energy utilization efficiency, and reduce energy waste. The mechanical alloying and spark plasma sintering technologies used in the preparation method are common material processing methods, which are easy to achieve large-scale production. This not only reduces production costs, but also improves production efficiency, which is conducive to the wide application of materials in practice. By rationally combining these methods, the preparation of the materials of the present invention can be achieved on the basis of existing production equipment and processes, without investing a lot of new equipment and new technology research and development costs.
[0058] The material of the present invention has broad application prospects in the fields of energy recovery and waste heat utilization. For example, in the industrial waste heat recovery system, waste heat can be efficiently converted into electrical energy to reduce energy waste. A large amount of waste heat will be generated in the industrial production process. If this waste heat can be effectively used to generate electricity, the energy utilization efficiency will be greatly improved. In the heat dissipation management of electronic equipment, its thermoelectric properties are used to achieve better temperature control and improve the stability and service life of the equipment. Electronic equipment will generate heat during operation. If the heat cannot be dissipated in time, it will affect the performance and service life of the equipment. The material of the present invention can convert heat into electrical energy through the thermoelectric effect, and at the same time play a role in heat dissipation, thereby improving the stability and service life of the equipment.
[0059] It should be understood that the application of the present invention is not limited to the above examples. For ordinary technicians in this field, improvements or changes can be made based on the above description. All these improvements and changes should fall within the scope of protection of the claims attached to the present invention.
Claims
1. A method for preparing a Mg3Bi2-based thermoelectric material, characterized in that: The method comprises the following steps: Selecting a magnesium-containing raw material with a relative intensity ratio of (002) peak to (101) peak greater than 50% as the magnesium raw material; Weigh the magnesium raw material and bismuth according to a stoichiometric ratio, mix the magnesium raw material and bismuth, and then ball-mill them to obtain a mixed powder; The mixed powder is sintered to obtain the Mg3Bi2-based thermoelectric material.
2. The method for preparing the Mg3Bi2-based thermoelectric material according to claim 1, characterized in that: The method of selecting a magnesium-containing raw material having a relative intensity ratio of the (002) peak to the (101) peak greater than 50% as the magnesium raw material comprises: preparing several magnesium-containing raw materials into corresponding blocks respectively, performing X-ray diffraction test on the blocks to obtain XRD diffraction patterns; The XRD diffraction pattern is analyzed, and a magnesium-containing raw material having a relative intensity ratio of (002) peak to (101) peak greater than 50% is selected as the magnesium raw material.
3. The method for preparing the Mg3Bi2-based thermoelectric material according to claim 1, characterized in that: The step of mixing the magnesium raw material and the bismuth and then ball milling the mixture to obtain a mixed powder comprises: Mixing all of the magnesium raw material and part of the bismuth in an inert atmosphere and then performing a pre-crushing treatment; After the pre-crushing is completed, the remaining bismuth is added and ball milling is continued to obtain the mixed powder.
4. The method for preparing the Mg3Bi2-based thermoelectric material according to claim 3, characterized in that: In the pre-crushing process, the mass ratio of magnesium to bismuth is 1:0.5-1.
5.
5. The method for preparing the Mg3Bi2-based thermoelectric material according to claim 1, characterized in that: The mixed powder is sintered, including: sintering at a sintering temperature of 600-800° C. and an axial pressure of 30-80 MPa.
6. The method for preparing the Mg3Bi2-based thermoelectric material according to claim 3, characterized in that: The pre-crushing time is 1.5-3 hours.
7. The method for preparing the Mg3Bi2-based thermoelectric material according to claim 3, characterized in that: The ball milling is continued for 7-10 hours at a rotation speed of 1500-1725 r / min.
8. The method for preparing the Mg3Bi2-based thermoelectric material according to claim 5, characterized in that: During the sintering process, the heating rate is 80-120℃ / min.
9. A Mg3Bi2-based thermoelectric material, characterized in that: The Mg3Bi2-based thermoelectric material is prepared by the preparation method described in any one of claims 1-8.
10. The Mg3Bi2-based thermoelectric material according to claim 9, characterized in that: The Mg3Bi2-based thermoelectric material has a magnetic resistance of 3342-5089% at a temperature of 2K and a magnetic field of 14 Tesla.