Transverse thermoelectric material and preparation method and application thereof

Abstract

The invention relates to the technical field of thermoelectric materials, in particular to a transverse thermoelectric material and a preparation method and application thereof, the transverse thermoelectric material is transition metal doped Mg3Bi2, the transition metal doped Mg3Bi2 is marked as Mg3Bi2: Mx, and M is a transition metal element; x ranges from 0 to 0.3 and is not equal to 0. Negative chemical pressure can be introduced into the Mg3Bi2 material by doping different transition metals, and the existence of the negative chemical pressure can promote an energy band structure to be converted from a topological insulator to topological semimetal and induce Dirac points with obvious linear dispersion characteristics, so that the electron mobility, the magnetic resistance and the transverse thermoelectric force of the material are greatly improved. The transverse thermoelectric material has a topological transformation structure from a topological insulator to Dirac semimetal, so that the transverse thermoelectric material has high transverse thermoelectric performance, and conversion between heat energy and electric energy is expected to be efficiently realized. Moreover, the preparation method of the transverse thermoelectric material is simple and easy to implement, large-scale preparation is easy, the production cost is reduced, and the production efficiency is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of thermoelectric materials, and in particular to a transverse thermoelectric material and a preparation method and application thereof. Background Art

[0002] Traditional thermoelectric technology has many shortcomings. One is that the performance of thermoelectric materials is poor and cannot meet the needs of efficient energy conversion. The conversion efficiency of common thermoelectric materials is far from the ideal level, resulting in a large amount of heat energy waste. The second is that the device preparation process is complicated, which not only increases the production cost, but also limits the possibility of large-scale production. The energy conversion efficiency of the thermoelectric effect is usually determined by the dimensionless quality factor. Due to the strong coupling relationship between the various transport parameters, the coordinated regulation of electric and thermal transmission has always been a historical problem; in addition, the operation of the thermoelectric module requires the serial connection of dozens or even hundreds of P / N paired thermoelectric materials, which makes the efficiency of the thermoelectric device closely related to the contact interface between the metal electrode and the thermoelectric arm. Therefore, the electroacoustic coupling effect at the material level and the complex contact interface problem at the device level make improving the energy conversion efficiency of thermoelectric technology a very challenging task.

[0003] Transverse thermoelectric technology can effectively avoid the above problems. Magnetic field, as a new control method, can drive carriers and phonons to transmit in different directions, thereby decoupling electric and thermal transport and achieving independent control of electrical and thermal conductivity. In addition, transverse thermoelectric devices can be made of one type of material and do not require P / N pairing, which greatly reduces the interface problems in the device manufacturing process. Therefore, transverse thermoelectric technology is expected to achieve an improvement in thermoelectric conversion efficiency. In existing studies, Mg 3 Bi 2 As a potential transverse thermoelectric material, it has attracted attention. It has a special layered crystal structure and topological semimetal band characteristics, and exhibits a linear non-saturated magnetoresistance of 940% under a magnetic field of 14 Tesla. The maximum transverse thermoelectric potential and power factor at 13.5K and 6 Tesla reach 126μV / K and 2182μWm respectively. -1 K -2 However, the lateral thermoelectric potential and power factor of such materials are still low, which greatly limits their future application in lateral thermoelectric energy conversion technology.

[0004] Therefore, the prior art still needs to be improved and developed. Summary of the invention

[0005] In view of the above-mentioned deficiencies in the prior art, an object of the present invention is to provide a transverse thermoelectric material and a preparation method and application thereof, aiming to solve the problem of low transverse thermoelectric potential and power factor of the existing transverse thermoelectric materials.

[0006] The technical solution of the present invention is as follows:

[0007] A lateral thermoelectric material, wherein the lateral thermoelectric material is Mg doped with a transition metal 3 Bi 2 , the transition metal-doped Mg 3 Bi 2 Note: Mg 3 Bi 2 :M x , where M is a transition metal element; the value range of x is 0-0.3 and is not equal to 0.

[0008] The lateral thermoelectric material, wherein the transition metal element includes one or more of Nb, Cr, Mn, Co, Ni, Ti, V, Mo, Fe, Cu, and Zn.

[0009] The lateral thermoelectric material, wherein the value of x ranges from 0.1 to 0.3.

[0010] The lateral thermoelectric material, wherein the value range of x is 0.01-0.15.

[0011] A method for preparing a lateral thermoelectric material comprises the following steps:

[0012] Weigh magnesium, bismuth and transition metal raw materials according to the stoichiometric ratio, and perform ball milling to obtain a mixed powder;

[0013] The mixed powder is subjected to spark plasma sintering treatment to obtain a transverse thermoelectric material.

[0014] The method for preparing the transverse thermoelectric material, wherein the ball milling treatment time is 5h-15h, and the ball milling treatment speed is 1000r / min-2500r / min.

[0015] The method for preparing the lateral thermoelectric material, wherein the ball milling process uses large stainless steel balls and small stainless steel balls; the diameter of the large stainless steel balls is larger than the diameter of the small stainless steel balls; the ratio of the number of the large stainless steel balls to the number of the small stainless steel balls is (1-3):(2-6).

[0016] The method for preparing the lateral thermoelectric material, wherein the pressure of the spark plasma sintering treatment is 30MPa-80MPa, the temperature of the spark plasma sintering treatment is 600℃-800℃, the time of the spark plasma sintering treatment is 5min-10min, and the heating rate of the spark plasma sintering treatment is 50℃ / min-150℃ / min.

[0017] A lateral thermoelectric material for use in energy recovery systems.

[0018] Application of a lateral thermoelectric material in a waste heat utilization system.

[0019] Beneficial effect: The present invention provides a lateral thermoelectric material and a preparation method and application thereof, wherein the lateral thermoelectric material is a transition metal-doped Mg 3 Bi 2 , the transition metal-doped Mg 3 Bi 2 Note: Mg 3 Bi 2 :M x , where M is a transition metal element; the value range of x is 0-0.3 and is not equal to 0. Since topological semimetals have linear dispersion band characteristics, they have the advantages of small Fermi surface, high current mobility and electron-hole compensation effect. Therefore, the present invention can be used in Mg by doping with different transition metals. 3 Bi 2 Negative chemical pressure is introduced into the material, and the presence of this negative chemical pressure can cause the energy band structure to change from a topological insulator to a topological semimetal, induce a Dirac point with obvious linear dispersion characteristics, and thus greatly improve the electron mobility, magnetoresistance and transverse thermoelectric potential of such materials. Specifically, the transverse thermoelectric material provided by the present invention has a topological transition structure from a topological insulator to a Dirac semimetal, so that the transverse thermoelectric material has high transverse thermoelectric performance, and is expected to efficiently realize the conversion of heat and electric energy. In addition, the preparation method of the transverse thermoelectric material is simple and easy, easy to prepare on a large scale, and reduces production costs and improves production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 The transition metal doped Mg 3 Bi 2 Schematic diagram of three ways;

[0021] Figure 2 The present invention is to dope the transition metal to increase the Mg 3 Bi 2 Mechanistic diagram of the lateral thermoelectric performance of the base material;

[0022] Figure 3 is the transition metal doped Mg in Example 1 3 Bi 2 XRD diffraction pattern of the material;

[0023] Figure 4 The transition metal doped Mg in Example 1 3 Bi 2 Performance diagram of materials;

[0024] Figure 5 The transition metal doped Mg in Example 1 3 Bi 2Magnetoresistance map of the material. DETAILED DESCRIPTION

[0025] The present invention provides a transverse thermoelectric material and a preparation method and application thereof. 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 herein are only used to explain the present invention and are not used to limit the present invention.

[0026] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as generally understood by those skilled in the art in the art to which the present invention belongs. It should also be understood that terms such as those defined in general dictionaries should be understood to have meanings consistent with the meanings in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless specifically defined as herein.

[0027] The present invention provides a lateral thermoelectric material, wherein the lateral thermoelectric material is a transition metal-doped Mg 3 Bi 2 , the transition metal-doped Mg 3 Bi 2 Note: Mg 3 Bi 2 :M x , where M is a transition metal element; the value range of x is 0-0.3 and is not equal to 0.

[0028] In this embodiment, if Figure 1 As shown, transition metal doped Mg 3 Bi 2 include Figure 1 (a) Tetrahedral doping, Figure 1 (b) Vertex octahedral doping and Figure 1 (c) Interstitial octahedral doping in the lateral thermoelectric material; the lateral thermoelectric material has a topological transition structure from a topological insulator to a Dirac semimetal, which has a significant impact on the thermoelectric performance. The thermoelectric performance mechanism diagram is shown in Figure 2 As shown, different transition metal doping can be used to 3 Bi 2Negative chemical pressure is introduced into the material, and the presence of this negative chemical pressure can cause the energy band structure to change from a topological insulator to a topological semimetal, induce a Dirac point with obvious linear dispersion characteristics, and thus greatly improve the electron mobility, magnetoresistance and transverse thermoelectric potential of such materials. Specifically, the transverse thermoelectric material provided by the present invention has a topological transition structure from a topological insulator to a Dirac semimetal, so that the transverse thermoelectric material has high transverse thermoelectric performance, and is expected to efficiently realize the conversion of heat and electric energy. In addition, the preparation method of the transverse thermoelectric material is simple and easy, easy to prepare on a large scale, and reduces production costs and improves production efficiency.

[0029] Specifically, the lateral thermoelectric material provided by the present invention has a topological transition structure from a topological insulator to a Dirac semimetal, and has high lateral thermoelectric performance; the lateral thermoelectric potential of the lateral thermoelectric material can be as high as 617 μV / K at 14K and 14 Tesla; the lateral power factor can be as high as 20393 μWm at 14K and 14 Tesla. -1 K -2 ; At 2K, the magnetic resistance is as high as 16600%. These performance indicators are significantly improved compared with existing lateral thermoelectric materials, and are expected to achieve efficient conversion of thermal energy into electrical energy.

[0030] In some embodiments, the transition metal element is not limited to one or more of Nb, Cr, Mn, Co, Ni, Ti, V, Mo, Fe, Cu, and Zn. 3 Bi 2 Doping materials can induce a topological transition from a topological insulator to a Dirac semimetal, which has a significant impact on the thermoelectric properties.

[0031] In some embodiments, the value range of x is 0.1-0.3. Controlling the doping amount x of the transition metal element within the above range can make the doping of the transition metal element in Mg 3 Bi 2 Negative chemical pressure is introduced inside the material, and the existence of this negative chemical pressure can cause the band structure to change from a topological insulator to a topological semimetal, inducing Dirac points with obvious linear dispersion characteristics, thereby greatly improving the electron mobility, magnetoresistance and transverse thermoelectric potential of such materials.

[0032] In some embodiments, the value of x is in the range of 0.01-0.15. When x is equal to 0, the lateral thermoelectric material is Mg 3 Bi 2 , which is an undoped state. When x is not equal to 0, the lateral thermoelectric material is a transition metal-doped Mg 3 Bi 2 :M x, has a topological transition structure from topological insulator to Dirac semimetal and possesses high lateral thermoelectric performance.

[0033] In addition, the present invention also provides a method for preparing a lateral thermoelectric material, comprising the steps of:

[0034] Step S10: weighing magnesium, bismuth and transition metal raw materials according to the stoichiometric ratio, and performing ball milling to obtain a mixed powder;

[0035] Step S20: performing spark plasma sintering on the mixed powder to obtain a transverse thermoelectric material.

[0036] In this embodiment, the preparation method of the lateral thermoelectric material is simple and easy, and the mechanical alloying and spark plasma sintering technology are used, which is 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.

[0037] Specifically, mechanical alloying and spark plasma sintering techniques can be used to dope Mg with different transition metals. 3 Bi 2 Negative chemical pressure is introduced into the material, and the existence of this negative chemical pressure can promote the transition of the band structure from topological insulator to topological semimetal, induce Dirac points with obvious linear dispersion characteristics, and thus greatly improve the electron mobility, magnetoresistance and transverse thermoelectric potential of such materials. The present invention significantly improves its transverse thermoelectric performance through precise material design and optimized preparation process, while maintaining other excellent properties of the material, simplifying the preparation process and reducing costs to meet practical application needs.

[0038] In some embodiments, the ball milling time is 5h-15h, and the ball milling speed is 1000r / min-2500r / min. By using ball milling, by controlling parameters such as ball milling time and speed, the raw materials are ensured to be fully mixed and evenly formed to form a stable precursor powder, i.e., a mixed powder.

[0039] In a preferred embodiment, the ball milling treatment time is 8h-10h, and the rotation speed of the ball milling treatment is 1500r / min-2400r / min, thereby improving the efficiency of the ball milling treatment and shortening the preparation cycle.

[0040] In some embodiments, the ball milling process uses large stainless steel balls and small stainless steel balls; the diameter of the large stainless steel balls is greater than the diameter of the small stainless steel balls; the ratio of the number of the large stainless steel balls to the number of the small stainless steel balls is (1-3): (2-6). By adjusting the ratio of the stainless steel balls, the mixing degree of the raw materials can be improved, ensuring that the raw materials are fully mixed and uniformly mixed to form a stable precursor powder.

[0041] In a preferred embodiment, the number of the large stainless steel balls is 1-3, and the number of the small stainless steel balls is 2-6.

[0042] It should be noted that large stainless steel balls and small stainless steel balls are relative and not fixed in size. The combination of large stainless steel balls and small stainless steel balls is used to avoid dead corners between the balls that may lead to insufficient mixing of the raw materials.

[0043] In some embodiments, the spark plasma sintering process is performed under a pressure of 30 MPa to 80 MPa, a temperature of 600°C to 800°C, a time of 5 min to 10 min, and a heating rate of 50°C / min to 150°C / min. The sintering temperature is closely related to the density of the material. The higher the sintering temperature, the better the density of the material and the higher the corresponding conductivity. However, Mg 3 Bi 2 The material will undergo a structural phase transition from α phase to β phase at a high temperature above 700°C, and the phase transition behavior will inhibit the material's electrical conductivity. Therefore, it is necessary to adjust the sintering temperature to synergistically optimize the material's density and structural phase transition. Through trial and error, it was found that sintering in the range of 600-800°C can obtain the best electrical transport behavior. In addition, precise control of the above parameters is crucial to forming an ideal crystal structure and microstructure, which directly affects the material's thermoelectric properties.

[0044] In addition, the present invention also provides an application of a lateral thermoelectric material in an energy recovery system, and an application of a lateral thermoelectric material in a waste heat utilization system.

[0045] In this embodiment, the provided lateral thermoelectric material has broad application prospects in the fields of energy recovery and waste heat utilization; for example, in industrial waste heat recovery systems, waste heat can be efficiently converted into electrical energy to reduce energy waste; in electronic equipment heat dissipation management, its thermoelectric properties can be used to achieve better temperature control and improve equipment stability and service life.

[0046] The following examples are further given to illustrate the present invention in detail. It should also be understood that the following examples are only used to further illustrate the present invention and cannot be understood as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention belong to the scope of protection of the present invention.

[0047] Example 1

[0048] Weigh magnesium (Mg), bismuth (Bi) and manganese (Mn) raw materials to make the Mn doping amount x = 0.1. Put the raw materials into a stainless steel ball mill, add stainless steel balls, and ball mill for 8 hours under argon protection. During the ball milling process, keep the argon pressure stable, the number of stainless steel balls is 2 large and 4 small, and the rotation speed is 1725r / min.

[0049] The mixed powder was loaded into a graphite mold and sintered at 700°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 polycrystalline Mn-doped Mg 3 Bi 2 :Mn 0.1 Material.

[0050] The same preparation method as in Example 1 was used to prepare polycrystalline Mn-doped Mg 3 Bi 2 :Mn 0.01 Materials and Mg 3 Bi 2 :Mn 0.05 Material; and prepare polycrystalline Cr-doped Mg with Cr doping amount x = 0.1 3 Bi 2 :Cr 0.1 Material: polycrystalline Co-doped Mg with Co doping amount x = 0.1 3 Bi 2 :Co 0.1 Materials, and polycrystalline Ni-doped Mg with Ni doping amount x = 0.01 3 Bi 2 :Ni 0.01 The material prepared above was characterized, and its XRD diffraction pattern was as follows Figure 3 As shown, #1 is Mg 3 Bi 2 :Mn 0.01 , #2 is Mg 3 Bi 2 :Mn 0.05 , #3 is Mg 3 Bi 2 :Mn 0.1 , #4 is Mg 3 Bi 2 :Cr 0.1 , #5 is Mg 3 Bi 2 :Co 0.1 , #6 is Mg 3 Bi 2 :Ni 0.01, indicating that polycrystalline transition metal element-doped lateral thermoelectric materials have been successfully produced.

[0051] The Mg prepared in Example 1 3 Bi 2 :Mn 0.1 Materials are tested for performance, such as Figure 4 As shown, Figure 4 (a) is the transverse thermoelectric potential under different temperatures and magnetic fields, and (b) is the power factor under different temperatures and magnetic fields. The results show that at 14K and 14Tesla, the transverse thermoelectric potential reaches 617μV / K and the transverse power factor reaches 20393μWm -1 K -2 .

[0052] In addition, the above preparation method was used to prepare polycrystalline Mn-doped Mg 3 Bi 2 :Mn 0.075 Material, Mg 3 Bi 2 :Mn 0.125 Materials and Mg 3 Bi 2 :Mn 0.15 Materials, transition metal-doped Mg 3 Bi 2 The material is tested and its magnetic resistance diagram is as follows Figure 5 As shown, Figure 5 (a) is Mg 3 Bi 2 :Mn 0.01 , (b) is Mg 3 Bi 2 :Mn 0.05 , (c) is Mg 3 Bi 2 :Mn 0.075 , (d) is Mg 3 Bi 2 :Mn 0.1 , (e) is Mg 3 Bi 2 :Mn 0.125 、(f) is Mg 3 Bi 2 :Mn 0.15 As can be seen from the figure, at 2K, the magnetic resistance reaches 16600%, which meets the requirements of the present invention.

[0053] Example 2

[0054] Weigh magnesium (Mg), bismuth (Bi) and cobalt (Co) samples to make the Co doping amount x = 0.05. Put the raw materials into a stainless steel ball mill, add stainless steel balls, and ball mill for 9 hours under argon protection. During this process, adjust the ball milling parameters, such as the number of stainless steel balls 2 large and 4 small, and the rotation speed of 1725r / min, to adapt to different doping amounts.

[0055] The mixed powder was loaded into a graphite mold and sintered at 750°C for 8 minutes under a pressure of 60 MPa using spark plasma sintering (SPS) technology. During the sintering process, the heating rate was controlled to 100°C / min to ensure uniform heating of the material, and polycrystalline Co-doped Mg 3 Bi 2 :Co 0.05 Material.

[0056] The performance test results show that the material also has good thermoelectric performance under the corresponding conditions, and all indicators are within the range required by the present invention. Specifically, at 14K and 14T Tesla, the transverse thermoelectric potential reaches 295μV / K and the transverse power factor reaches 7350μWm -1 K -2 At 2K, the magnetic resistance reaches 4600%, which meets the requirements of the present invention.

[0057] Example 3

[0058] Weigh magnesium (Mg), bismuth (Bi) and chromium (Cr) raw materials to make the Cr doping amount x = 0.125. Put the raw materials into a stainless steel ball mill and mill them for 10 hours under argon protection. Adjust the ball milling parameters according to the doping amount, the number of stainless steel balls is 2 large and 4 small, and the rotation speed is 1725r / min.

[0059] The mixed powder was loaded into a graphite mold and sintered at 700°C for 10 minutes under a pressure of 40 MPa using spark plasma sintering (SPS) technology. The parameters during the sintering process were strictly controlled, and the heating rate was 100°C / min to obtain polycrystalline Cr-doped Mg 3 Bi 2 :Cr 0.05 Material.

[0060] After testing, the material also meets the high-performance thermoelectric performance indicators set by the present invention. At 14K and 14Tesla, the thermoelectric potential reaches 202μV / K and the lateral power factor reaches 3800μWm -1 K -2 ; At 2K, the magnetic resistance reaches 2100%.

[0061] In summary, the present invention provides a lateral thermoelectric material and a preparation method and application thereof, wherein the lateral thermoelectric material is a transition metal-doped Mg 3 Bi2 , the transition metal-doped Mg 3 Bi 2 Note: Mg 3 Bi 2 :M x , where M is a transition metal element; the value range of x is 0-0.3 and is not equal to 0. Since topological semimetals have linear dispersion band characteristics, they have the advantages of small Fermi surface, high current mobility and electron-hole compensation effect. Therefore, the present invention can be used in Mg by doping with different transition metals. 3 Bi 2 Negative chemical pressure is introduced into the material, and the presence of this negative chemical pressure can cause the energy band structure to change from a topological insulator to a topological semimetal, induce a Dirac point with obvious linear dispersion characteristics, and thus greatly improve the electron mobility, magnetoresistance and transverse thermoelectric potential of such materials. Specifically, the transverse thermoelectric material provided by the present invention has a topological transition structure from a topological insulator to a Dirac semimetal, so that the transverse thermoelectric material has high transverse thermoelectric performance, and is expected to efficiently realize the conversion of heat and electric energy. In addition, the preparation method of the transverse thermoelectric material is simple and easy, easy to prepare on a large scale, and reduces production costs and improves production efficiency.

[0062] 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 lateral thermoelectric material, characterized in that: The lateral thermoelectric material is transition metal-doped Mg3Bi2, and the transition metal-doped Mg3Bi2 is denoted as Mg3Bi2:M x , where M is a transition metal element; the value range of x is 0-0.3 and is not equal to 0.

2. The lateral thermoelectric material according to claim 1, characterized in that: The transition metal element includes one or more of Nb, Cr, Mn, Co, Ni, Ti, V, Mo, Fe, Cu, and Zn.

3. The lateral thermoelectric material according to claim 1, characterized in that: The value range of x is 0.1-0.

3.

4. The lateral thermoelectric material according to claim 1, characterized in that: The value range of x is 0.01-0.

15.

5. A method for preparing a lateral thermoelectric material according to any one of claims 1 to 4, characterized in that: Includes steps: Weigh magnesium, bismuth and transition metal raw materials according to the stoichiometric ratio, and perform ball milling to obtain a mixed powder; The mixed powder is subjected to spark plasma sintering treatment to obtain a transverse thermoelectric material.

6. The method for preparing a lateral thermoelectric material according to claim 5, characterized in that: The ball milling treatment time is 5h-15h, and the ball milling treatment speed is 1000r / min-2500r / min.

7. The method for preparing a lateral thermoelectric material according to claim 5, characterized in that: The ball milling process uses large stainless steel balls and small stainless steel balls; the diameter of the large stainless steel balls is greater than the diameter of the small stainless steel balls; the number ratio of the large stainless steel balls to the small stainless steel balls is (1-3):(2-6).

8. The method for preparing a lateral thermoelectric material according to claim 5, characterized in that: The pressure of the spark plasma sintering treatment is 30MPa-80MPa, the temperature of the spark plasma sintering treatment is 600°C-800°C, the time of the spark plasma sintering treatment is 5min-10min, and the heating rate of the spark plasma sintering treatment is 50°C / min-150°C / min.

9. Use of the lateral thermoelectric material according to any one of claims 1 to 4 in an energy recovery system.

10. Use of the lateral thermoelectric material according to any one of claims 1 to 4 in a waste heat utilization system.

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