High-strength high-plasticity thermoelectric composite material, preparation method and application thereof

Abstract

The application belongs to the technical field of thermoelectric materials, and particularly relates to a high-strength high-plasticity thermoelectric composite material and a preparation method and application thereof. The application introduces nano TiB2, which can form an energy barrier with a matrix, and improves the Zabek coefficient without significantly reducing the electrical conductivity. Meanwhile, the nano-pores generated by sintering are used to jointly optimize and adjust the thermal conductivity, so that the power factor and the thermal conductivity of the material are synergistically optimized. The composite nano TiB2 also enhances the mechanical properties of the material. The thermoelectric composite material provided by the application has high plasticity, high compressive strength, high hardness and high thermoelectric performance, excellent mechanical properties, good processability, non-toxic elements and low cost.

Description

Technical Field

[0001] This invention belongs to the field of thermoelectric materials technology, specifically relating to a high-strength, high-plasticity thermoelectric composite material, its preparation method, and its application. Background Technology

[0002] Thermoelectric materials have attracted widespread attention due to their ability to directly convert heat energy into electrical energy. With the development of thermoelectric technology, the demand for thermoelectric materials with high thermoelectric performance, high strength, and high ductility at room temperature is constantly increasing. The performance of thermoelectric materials is characterized by the dimensionless thermoelectric figure of merit (ZT), ZT = S 2 σT / κ, where S is the Seebeck coefficient, σ is the electrical conductivity, κ is the thermal conductivity, and T is the absolute temperature.

[0003] Currently, most traditional thermoelectric materials are brittle, have extremely poor processability, low strength, and poor structural stability during application. Summary of the Invention

[0004] The purpose of this invention is to provide a high-strength, high-plasticity thermoelectric composite material, its preparation method, and its application. The thermoelectric composite material provided by this invention has high strength, high plasticity, and high thermoelectric properties.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] This invention provides a thermoelectric composite material with the chemical composition Mg. 3.2 Sb 1.5 Bi 0.49 Te 0.01 -xTiB2; where x is the molar mass fraction, 0.01≤x≤0.05; the TiB2 in the thermoelectric composite material is nano-TiB2.

[0007] Preferably, x is 0.03 to 0.05.

[0008] The present invention also provides a method for preparing the thermoelectric composite material described above, comprising the following steps:

[0009] (1) Mg, Bi, Sb, Te and TiB2 were ball-milled in an inert atmosphere to obtain precursor powder;

[0010] (2) The precursor powder is sintered to obtain the thermoelectric composite material.

[0011] Preferably, the TiB2 is TiB2 powder; the particle size of the TiB2 powder is 50-100 nm.

[0012] Preferably, the molar ratio of Mg to TiB2 is 3.2:0.01-0.05; the molar ratio of Bi to TiB2 is 0.49:0.01-0.05; the molar ratio of Sb to TiB2 is 1.5:0.01-0.05; and the molar ratio of Te to TiB2 is 0.01:0.01-0.05.

[0013] Preferably, the ball mill is a vibratory ball mill; the rotation speed of the ball mill is 1000-1500 rpm; the running speed of the ball mill fixture is 850-890 cycles / minute; the ball milling time is 3-10 hours; and the ball milling method is: stop the ball milling for 1 hour every 2 hours.

[0014] Preferably, the sintering pressure is 40-60 MPa; the sintering temperature is 750-850 °C; and the sintering time is 10-20 min.

[0015] Preferably, the sintering temperature rise program is as follows: the temperature is raised to 600-650°C within 4-6 minutes, and then raised to the sintering temperature within 5-6 minutes.

[0016] Preferably, the sintering process further includes cooling the resulting reaction system; the cooling process involves reducing the pressure to 0.05-0.1 MPa within 1-2 minutes, and then cooling the furnace to room temperature.

[0017] The present invention also provides the application of the thermoelectric composite material described in the above-described scheme or the thermoelectric composite material obtained by the preparation method described in the above-described scheme in the field of thermoelectric devices.

[0018] This invention provides a thermoelectric composite material. The invention introduces nano-TiB2, which can form an energy barrier with the matrix, increasing the Seebeck coefficient without significantly reducing electrical conductivity. Simultaneously, the nanopores generated by Mg3(Sb,Bi)2 sintering, together with the composite nano-TiB2, optimize and regulate thermal conductivity, ultimately achieving synergistic optimization of the material's power factor and thermal conductivity. The nanopores and composite nano-TiB2 synergistically enhance the material's mechanical properties. The thermoelectric composite material provided by this invention possesses high plasticity, high compressive strength, high hardness, and high thermoelectric properties, excellent mechanical properties, good processability, non-toxic elements, and low cost.

[0019] The results of the examples show that the thermoelectric figure of merit of the thermoelectric composite material provided by the present invention is about 0.64 at room temperature, and the average thermoelectric figure of merit is 1.24 in the range of 323 to 773 K. The Vickers hardness is 0.71 GPa, and the compressive strength is 730 MPa while maintaining 45% compressive strain.

[0020] This invention also provides a method for preparing the thermoelectric composite material described above. The preparation method provided by this invention is simple in steps, convenient in operation, and highly feasible.

[0021] This invention also provides the application of the thermoelectric composite material described in the above-described scheme or the thermoelectric composite material obtained by the preparation method described in the above-described scheme in the field of thermoelectric devices. The thermoelectric composite material provided by this invention has the characteristics of high strength, high plasticity and high thermoelectric properties, and has great application potential in thermoelectric devices. Attached Figure Description

[0022] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0023] Figure 1 The electrical conductivity curves of the thermoelectric composite materials of Examples 1-3 and Comparative Example 1 are shown.

[0024] Figure 2 See the Seebeck coefficient curves of the thermoelectric composite materials of Examples 1-3 and Comparative Example 1;

[0025] Figure 3 Power factor curves of the thermoelectric composite materials of Examples 1-3 and Comparative Example 1 are shown.

[0026] Figure 4 The thermal conductivity curves of the thermoelectric composite materials of Examples 1-3 and Comparative Example 1 are shown.

[0027] Figure 5 Thermoelectric figure of merit diagrams for the thermoelectric composite materials of Examples 1-3 and Comparative Example 1;

[0028] Figure 6 Vickers hardness diagrams of the thermoelectric composite materials of Examples 1-3 and Comparative Example 1;

[0029] Figure 7 The images show the compressive stress-strain curves of the thermoelectric composite materials in Example 1 and Comparative Examples 1-2. Detailed Implementation

[0030] This invention provides a thermoelectric composite material with the chemical composition Mg. 3.2 Sb 1.5 Bi 0.49 Te 0.01 -xTiB2; where x is the molar mass fraction, 0.01≤x≤0.05; the TiB2 in the thermoelectric composite material is nano-TiB2.

[0031] In this invention, x is preferably 0.03 to 0.05, specifically 0.03, 0.035, 0.04, 0.045, or 0.05. This invention improves the thermoelectric and mechanical properties of the material by controlling the content of nano-TiB2.

[0032] In this invention, the formula for calculating x is specifically as follows:

[0033] x = M2 × m / M1;

[0034] Where M1 is Mg 3.2 Sb 1.5 Bi 0.5 Te 0.01 The total molar mass is M2, where M2 is the molar mass of TiB2 and m is the required mass of TiB2.

[0035] This invention introduces nano-TiB2, which can form an energy barrier with the matrix, thereby increasing the Seebeck coefficient without significantly reducing electrical conductivity. At the same time, the nanopores generated by sintering Mg3(Sb,Bi)2 and the composite nano-TiB2 work together to regulate the thermal conductivity of the material, ultimately improving the room temperature ZT of the material. In addition, the nanopores generated by sintering weaken stress concentration and improve the plasticity of the material, while the composite nano-TiB2 also blocks the movement of dislocations, enhancing the mechanical properties of the material.

[0036] The present invention also provides a method for preparing the thermoelectric composite material described above, comprising the following steps:

[0037] (1) Mg, Bi, Sb, Te and TiB2 were ball-milled in an inert atmosphere to obtain precursor powder;

[0038] (2) The precursor powder is sintered to obtain the thermoelectric composite material.

[0039] This invention involves ball milling Mg, Bi, Sb, Te, and TiB2 in an inert atmosphere to obtain precursor powder. The source of the Mg, Bi, Sb, Te, and TiB2 is not particularly limited; commercially available products well-known to those skilled in the art can be used.

[0040] In this invention, the Mg is preferably Mg particles; the purity of the Mg is preferably 99.95%; the Bi is preferably Bi particles; the purity of the Bi is preferably 99.999%; the Sb is preferably Sb particles; the purity of the Sb is preferably 99.99%; the Te is preferably Te powder; the purity of the Te is preferably 99.99%; the TiB2 is preferably TiB2 powder; the particle size of the TiB2 powder is preferably 50-100 nm, specifically 50 nm, 60 nm, 70 nm, 80 nm, 90 nm or 100 nm; the purity of the TiB2 is preferably 99.9%.

[0041] In this invention, the molar ratio of Mg to TiB2 is preferably 3.2:0.01 to 0.05, specifically 3.2:0.01, 3.2:0.02, 3.2:0.03, 3.2:0.04, or 3.2:0.05. This invention adds excess Mg to prevent magnesium volatilization due to prolonged heat treatment, ensuring that the thermoelectric composite material is an n-type semiconductor.

[0042] In this invention, the molar ratio of Bi to TiB2 is preferably 0.49:0.01 to 0.05, specifically 0.49:0.01, 0.49:0.02, 0.49:0.03, 0.49:0.04 or 0.49:0.05.

[0043] In this invention, the molar ratio of Sb to TiB2 is preferably 1.5:0.01 to 0.05, specifically 1.5:0.01, 1.5:0.02, 1.5:0.03, 1.5:0.04 or 1.5:0.05.

[0044] In this invention, the molar ratio of Te to TiB2 is preferably 0.01:0.01 to 0.05, specifically 0.01:0.01, 0.01:0.02, 0.01:0.03, 0.01:0.04, or 0.01:0.05. This invention, while adding excess Mg, limits the proportions of each element to ensure that each element fully functions and improves the thermoelectric properties of the thermoelectric composite material.

[0045] In this invention, the inert atmosphere is preferably argon; the water and oxygen content of the inert atmosphere is preferably less than 1 ppm, specifically 0.9 ppm, 0.7 ppm, 0.5 ppm, 0.4 ppm, 0.3 ppm, 0.2 ppm, or 0.1 ppm. Since Mg readily reacts with water and oxygen in the air, causing a sharp decrease in the power factor of the material, the batching in this embodiment is carried out in an argon-filled glove box.

[0046] In this invention, the ball milling is preferably a vibratory ball milling process; the rotational speed of the ball mill is preferably 1000–1500 rpm, specifically 1000 rpm, 1100 rpm, 1200 rpm, 1300 rpm, 1400 rpm, or 1500 rpm; the clamping speed of the ball mill is preferably 850–890 cycles / minute, specifically 850 cycles / minute, 860 cycles / minute, 875 cycles / minute, or 890 cycles / minute. By employing the above-mentioned ball milling parameters, this invention ensures the thoroughness of the ball milling and the stability of the milled products, thereby guaranteeing the repeatability of material preparation.

[0047] In this invention, the ball milling equipment is preferably a Spex ball mill; the ball milling time is preferably 3 to 10 hours, specifically 3 hours, 5 hours, 7 hours or 10 hours; the ball milling method is preferably to stop ball milling for 1 hour every 2 hours.

[0048] In this invention, after ball milling, it is preferable to scrape the powder off the inner wall of the ball mill in an inert atmosphere, and then ball mill for another 1-3 minutes. Through these operations, this invention prevents damage to the ball mill and uneven ball milling caused by powder agglomeration, ensures the completeness of the ball mill powder reaction and the uniformity of element distribution, and prevents large particles from affecting sintering.

[0049] In a specific embodiment of the invention, it is preferable to weigh 6-10g of raw materials (Mg, Bi, Sb, Te, and TiB2) each time and place them in a ball mill jar containing two 0.5-inch stainless steel balls. This invention ensures the thoroughness of the ball milling process by controlling the input amount of raw materials.

[0050] After obtaining the precursor powder, the present invention sintersulates the precursor powder to obtain the thermoelectric composite material. In the present invention, the sintering is preferably discharge plasma sintering.

[0051] In this invention, the sintering pressure is preferably 40-60 MPa, specifically 40 MPa, 45 MPa, 50 MPa, 55 MPa or 60 MPa, more preferably 50 MPa.

[0052] In this invention, the sintering temperature is preferably 750-850°C, specifically 750°C, 760°C, 770°C, 790°C, 800°C, 810°C, 830°C or 850°C, more preferably 800°C.

[0053] In this invention, the sintering time is preferably 10–20 min, specifically 10 min, 12 min, 14 min, 15 min, 16 min, 18 min, or 20 min. By limiting the sintering parameters, this invention achieves a full reaction of the precursor powder, adjusts the grain size and pore size, generates various nanopores, and thus improves the thermoelectric properties of the thermoelectric composite material.

[0054] In this invention, the preferred sintering temperature rise procedure is to raise the temperature to 600-650°C within 4-6 minutes, and then raise it to the sintering temperature within 5-6 minutes. This sintering temperature rise procedure ensures thorough sintering of the precursor powder. The higher sintering temperature and holding time also allow for sufficient grain growth and introduce numerous nanopores, thus guaranteeing the material's electrical and thermal conductivity.

[0055] In this invention, the sintering process preferably includes cooling the resulting reaction system; the cooling process is preferably: reducing the pressure to 0.05-0.1 MPa within 1-2 minutes, and then cooling the furnace to room temperature.

[0056] The method for preparing thermoelectric composite materials provided by the present invention, by limiting the process parameters of ball milling and sintering, enables the matrix powder (Mg, Bi, Sb and Te) and nano TiB2 powder to be fully sintered, and promotes the full growth of grain size and the formation of nanopores, thereby further improving the thermoelectric properties of the thermoelectric composite material.

[0057] The present invention also provides the application of the thermoelectric composite material described in the above-described scheme or the thermoelectric composite material obtained by the preparation method described in the above-described scheme in the field of thermoelectric devices.

[0058] The thermoelectric composite material provided by this invention possesses high strength, high plasticity, and high thermoelectric properties, and has great application potential in thermoelectric devices. Example results show that the thermoelectric figure of merit of the composite material provided by this invention is approximately 0.64 at room temperature, with an average thermoelectric figure of merit of 1.24 in the range of 323–773 K, a Vickers hardness of 0.71 GPa, and a compressive strength of 730 MPa while maintaining 45% compressive strain.

[0059] To further illustrate the present invention, the following detailed description of the invention's solutions, in conjunction with the accompanying drawings and embodiments, is provided, but should not be construed as limiting the scope of protection of the present invention.

[0060] Example 1

[0061] The thermoelectric composite material prepared in this embodiment has a chemical composition of Mg3Sb. 1.5 Bi 0.49 Te 0.01 -0.03TiB2.

[0062] The specific steps of the preparation method of the thermoelectric composite material described in this embodiment are as follows:

[0063] (1) In a glove box with an argon atmosphere containing less than 1 ppm of water and oxygen, 1.6591 g of Mg metal particles, 3.8967 g of Sb metal particles, 2.1844 g of Bi metal particles, 0.02676 g of Te metal powder, and 0.2330 g of nano TiB2 powder were weighed. The molar ratio of Mg metal particles, Sb metal particles, Bi metal particles to Te metal powder was 3.2:1.5:0.49:0.01. The content of nano TiB2 was Mg3Sb 1.5 Bi 0.49 Te 0.01 3% of the total molar mass; and the weighed Mg metal particles, Sb metal particles, Bi metal particles, Te metal powder and TiB2 nano powder were added to a Spex ball mill containing two 0.5-inch stainless steel balls and ball-milled for 5 hours. First, run for 1 hour, then stop and scrape the powder off the ball mill jar wall. After that, every 2 hours, scrape off the powder adhering to the ball mill jar wall in the glove box and put it back into the jar to continue ball milling. After the ball milling is finished, ball mill for another 1 minute to ensure that the obtained precursor powder is free of agglomerated particles; the speed of the ball mill is 1500 rpm and the clamp running rate is 875 cycles / minute;

[0064] (2) The precursor powder obtained in step (1) was loaded into a graphite mold in an inert atmosphere. The graphite mold was placed in a spark plasma sintering furnace. Under a pressure of 50 MPa, the temperature was raised to 610 °C within 5 min, and then raised to 800 °C within another 5 min. The temperature was held at 800 °C for 15 min for spark plasma sintering. After sintering, the pressure was reduced to 0.05 MPa within 1 min, and then the furnace was cooled to room temperature to obtain Mg3Sb. 1.5 Bi 0.49 Te 0.01 -0.03TiB2 thermoelectric composite material.

[0065] Example 2

[0066] The preparation method in this embodiment is the same as in Example 1, except that the chemical composition of the thermoelectric composite material is Mg3Sb. 1.5 Bi 0.49 Te 0.01 -0.01TiB2; correspondingly, the raw materials are 1.6920g of Mg metal particles, 3.9733g of Sb metal particles, 2.2277g of Bi metal particles, 0.0275g of Te metal powder and 0.0792g of nano TiB2 powder, wherein the content of nano TiB2 is Mg3Sb 1.5 Bi 0.49 Te 0.011% of the total molar amount; other details are the same as in Example 1.

[0067] Example 3

[0068] The preparation method in this embodiment is the same as in Example 2, except that the chemical composition of the thermoelectric composite material is Mg3Sb. 1.5 Bi 0.49 Te 0.01 -0.05TiB2; correspondingly, the raw materials are 1.6275g of Mg metal particles, 3.8219g of Sb metal particles, 2.1428g of Bi metal particles, 0.02670g of Te metal powder and 0.3809g of nano TiB2 powder, wherein the content of nano TiB2 is Mg3Sb 1.5 Bi 0.49 Te 0.01 5% of the total molar amount, otherwise the same as in Example 2.

[0069] Comparative Example 1

[0070] The preparation method of this comparative example is the same as that of Example 1, except that: no composite nano-TiB2 powder is used, and the chemical composition of the thermoelectric material is Mg3Sb. 1.5 Bi 0.49 Te 0.01 Correspondingly, the raw materials are 1.7089g of Mg metal particles, 4.0130g of Sb metal particles, 2.2500g of Bi metal particles and 0.028g of Te metal powder, wherein the molar ratio of Mg metal particles, Sb metal particles, Bi metal particles and Te metal powder is 3.2:1.5:0.49:0.01; other aspects are the same as in Example 1.

[0071] Comparative Example 2

[0072] The preparation method of this comparative example is the same as that of Example 1, except that: no composite nano-TiB2 powder is used, and the chemical composition of the thermoelectric material is Mg3Sb. 1.5 Bi 0.49 Te 0.01 Correspondingly, the raw materials are 1.7089g of Mg metal particles, 4.0130g of Sb metal particles, 2.2500g of Bi metal particles and 0.028g of Te metal powder, wherein the molar ratio of Mg metal particles, Sb metal particles, Bi metal particles and Te metal powder is 3.2:1.5:0.49:0.01; the sintering temperature is 750℃, and other conditions are the same as in Example 1.

[0073] Performance testing

[0074] The electrical properties of the thermoelectric composite materials obtained in Examples 1-3 and Comparative Example 1 were tested using the LSR-3 electrical performance testing system. The conductivity test curves are shown below. Figure 1 As shown, the test curve for the Seebeck coefficient is as follows: Figure 2 As shown, the power factor test curve is as follows: Figure 3 As shown. According to Figures 1-3 It can be seen that after TiB2 is incorporated into the matrix, the electrical conductivity decreases slightly, while the Seebeck coefficient increases significantly, thereby improving the power factor of the prepared thermoelectric composite material.

[0075] The thermal diffusivity F of the thermoelectric composite materials obtained in Examples 1-3 and Comparative Example 1 was tested using the laser flare method (LFA-457 laser thermal conductivity meter). The sample density D was determined by combining the results with the Archimedes displacement method. d And formula C p [J g -1 K -1 ]=3NR / MW·(1+1.3×10 -4 ×T-4×10 -3 ×T 2 The calculated heat capacity C p Then calculate the total thermal conductivity κ using the following formula: κ = C p D d The results of the total thermal conductivity are as follows Figure 4 As shown. According to Figure 4 It can be seen that when the amount of nano-TiB2 composite is small, the thermal conductivity of the thermoelectric composite material decreases compared to the matrix, but as the amount of composite increases, the thermal conductivity of the material increases.

[0076] Using the formula ZT = S 2 σT / κ tot The thermoelectric figure of merit of the thermoelectric composite materials obtained in Examples 1-3 and Comparative Example 1 were calculated, and the results are as follows: Figure 5 As shown. According to Figure 5 It can be seen that the thermoelectric performance of the material is improved overall after composite nano-TiB2.

[0077] The surfaces of the thermoelectric composite materials obtained in Examples 1-3 and Comparative Example 1 were polished, and then the Vickers hardness was measured using a Vickers hardness tester (MH-50 microhardness tester). The results are as follows: Figure 6 As shown. According to Figure 6 It can be seen that the Vickers hardness of the thermoelectric composite material of the present invention increases with the increase of the composite amount of nano-TiB2.

[0078] The thermoelectric composite materials obtained in Example 1 and Comparative Examples 1-2 were cut into 4×2×2 mm long rods. All six surfaces of the rods were polished smooth, and compression tests were performed using a universal testing machine (Instron 5982). The results are as follows: Figure 7 As shown. According to Figure 7 It can be seen that after composite nano-TiB2, the compressive strain of the thermoelectric composite material prepared by this invention decreases slightly, but can still be maintained at more than 40%, while the compressive strength is greatly improved.

[0079] As can be seen from the above embodiments, the thermoelectric composite material provided by the present invention achieves a thermoelectric figure of merit that is improved across the entire temperature range due to the simultaneous improvement of power factor and thermal conductivity. At the same time, due to the composite of nano-TiB2, the thermoelectric composite material improves Vickers hardness and compressive strength while maintaining plasticity, resulting in excellent comprehensive performance.

[0080] Although the above embodiments have provided a detailed description of the present invention, they are only some embodiments of the present invention, and not all embodiments. Other embodiments can be obtained based on these embodiments without creative effort, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for producing a thermoelectric composite material, characterized by, The specific steps are as follows: (1) In an argon atmosphere glove box with water and oxygen content less than 1 ppm, 1.6591 g of Mg metal particles, 3.8967 g of Sb metal particles, 2.1844 g of Bi metal particles, 0.02676 g of Te metal powder and 0.2330 g of nano TiB2 powder are weighed; and the weighed Mg metal particles, Sb metal particles, Bi metal particles, Te metal powder and TiB2 nano powder are added into a spex ball mill containing two 0.5-inch stainless steel balls for ball milling for 5 h, running for 1 h first, stopping and scraping the powder on the wall of the ball mill tank, then scraping the powder sticking to the wall of the ball mill tank every 2 h in the glove box, putting it into the tank for continuous ball milling, and ball milling for 1 min after the ball milling is completed to ensure that the obtained precursor powder has no agglomerated particles; the rotation speed of the ball mill is 1500 rpm, and the clamp running rate is 875 cycles / minute; (2) The precursor powder obtained in step (1) is loaded into a graphite mold in an inert atmosphere, the graphite mold is placed in a spark plasma sintering furnace, and sintering is performed under a pressure of 50 MPa, the temperature is raised to 610 ℃ within 5 min, then the temperature is raised to 800 ℃ within 5 min, and the temperature is kept at 800 ℃ for 15 min for spark plasma sintering; After sintering is completed, the pressure is reduced to 0.05 MPa within 1 min, and then the furnace is cooled to room temperature to obtain the thermoelectric composite material.

2. A method for producing a thermoelectric composite material, characterized by, The specific steps are as follows: (1) In an argon atmosphere glove box with water and oxygen content less than 1 ppm, 1.6591 g of Mg metal particles, 3.8967 g of Sb metal particles, 2.1844 g of Bi metal particles, 0.02676 g of Te metal powder and 0.2330 g of nano TiB2 powder are weighed; and the weighed Mg metal particles, Sb metal particles, Bi metal particles, Te metal powder and TiB2 nano powder are added into a spex ball mill containing two 0.5-inch stainless steel balls for ball milling for 5 h, running for 1 h first, stopping and scraping the powder on the wall of the ball mill tank, then scraping the powder sticking to the wall of the ball mill tank every 2 h in the glove box, putting it into the tank for continuous ball milling, and ball milling for 1 min after the ball milling is completed to ensure that the obtained precursor powder has no agglomerated particles; the rotation speed of the ball mill is 1500 rpm, and the clamp running rate is 875 cycles / minute; (2) The precursor powder obtained in step (1) is loaded into a graphite mold in an inert atmosphere, the graphite mold is placed in a spark plasma sintering furnace, and sintering is performed under a pressure of 50 MPa, the temperature is raised to 610 ℃ within 5 min, then the temperature is raised to 800 ℃ within 5 min, and the temperature is kept at 800 ℃ for 15 min for spark plasma sintering; After sintering is completed, the pressure is reduced to 0.05 MPa within 1 min, and then the furnace is cooled to room temperature to obtain the thermoelectric composite material.

3. A method for producing a thermoelectric composite material, characterized by, The specific steps are as follows: (1) In an argon atmosphere glove box with water and oxygen content less than 1 ppm, 1.6275 g of Mg metal particles, 3.8219 g of Sb metal particles, 2.1428 g of Bi metal particles, 0.02670 g of Te metal powder and 0.3809 g of nano TiB2 powder were weighed; and the weighed Mg metal particles, Sb metal particles, Bi metal particles, Te metal powder and TiB2 nano powder were added to a spex ball mill containing two 0.5-inch stainless steel balls and ball milled for 5 h, running for 1 h first, stopping and scraping the powder on the wall of the ball mill, then every 2 h in the glove box, the powder sticking to the wall of the ball mill was scraped off and put into the tank for continuous ball milling, after the ball milling was completed, it was ball milled for another 1 min to ensure that the obtained precursor powder had no agglomerated particles; the rotation speed of the ball mill was 1500 rpm and the clamp running rate was 875 cycles / min; (2) The precursor powder obtained in step (1) was loaded into a graphite mold in an inert atmosphere, the graphite mold was placed in a spark plasma sintering furnace, heated to 610 ℃ under a pressure of 50 MPa in 5 min, then heated to 800 ℃ in another 5 min, and sintered by spark plasma sintering at 800 ℃ for 15 min; After sintering, the pressure was reduced to 0.05 MPa in 1 min, then the furnace was cooled to room temperature, and the thermoelectric composite material was obtained.

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