Thermoelectric material and preparation method therefor

Abstract

The present application provides a thermoelectric material and a preparation method therefor. The preparation method for a thermoelectric material comprises: subjecting powder comprising an M element, an A element, and an L element to flash hot-press sintering treatment to obtain the thermoelectric material. M is a group IB element, A is a group IVA element, and L is a group VIA element, and the difference between the highest melting point element and the lowest melting point element among the M element, the A element, and the L element is ≥700°C. The preparation method can prepare a thermoelectric material having fewer defects, a high Seebeck coefficient, and a high thermoelectric figure of merit. The preparation method is simple, has a short preparation cycle, and is suitable for wide application.

Description

A thermoelectric material and its preparation method

[0001] This application claims priority to Chinese Patent Application No. 202411533006.5, filed on October 30, 2024, entitled "A thermoelectric material and a method for preparing the same", the entire contents of which are incorporated herein by reference. Technical Field

[0002] This application belongs to the field of thermoelectric materials, specifically relating to a thermoelectric material and its preparation method. Background Technology

[0003] Energy conservation, carbon reduction, and improved energy efficiency are important measures to actively promote carbon peaking and carbon neutrality, and to facilitate a comprehensive green transformation of economic and social development. Thermoelectric materials are functional materials that can convert heat energy and electrical energy into each other. They achieve direct conversion between electrical and heat energy by transporting charge carriers within the thermoelectric material, eliminating the need for mechanical energy transition. This significantly improves energy efficiency and offers advantages such as noiseless operation, wear-free operation, simple maintenance, small size, and high integration. They have promising applications in thermoelectric power generation, solid-state refrigeration, and temperature control. The thermoelectric performance of thermoelectric materials is typically characterized by the thermoelectric figure of merit (ZT). A higher ZT indicates better thermoelectric performance.

[0004] Copper-based diamond-like carbon (DLC) compounds are considered promising thermoelectric materials. They possess structural and functional units that facilitate the synergistic regulation of electrical and thermal properties. On one hand, their Cu-X framework structure allows for the formation of a three-dimensional conductive network, ensuring excellent electrical transport performance. On the other hand, their distorted crystal structure generates additional phonon scattering, contributing to intrinsically low lattice thermal conductivity. Ternary Cu-Sn-S-based thermoelectric materials are one type of copper-based DLC compound, attracting widespread attention due to their low cost and abundant crustal reserves. However, the significant difference in melting points among the three constituent elements (Cu, Sn, and S) leads to elemental imbalances and compositional segregation during preparation, resulting in a low Seebeck coefficient and deteriorated thermoelectric performance.

[0005] Currently, conventional methods mainly involve elemental doping to introduce new charge carriers and improve the thermoelectric performance of ternary Cu-Sn-S-based thermoelectric materials. For example, CN113013314A discloses a p-type high-performance Cu-Sn-S diamond-like structure thermoelectric material and its preparation method. This p-type high-performance Cu-Sn-S diamond-like structure thermoelectric material improves thermoelectric performance by replacing part of the S element with halogen doping (F, Cl, Br, I, etc.). However, this method, due to halogen doping, suffers from high cost, high toxicity, and poor environmental friendliness; furthermore, the intrinsic defects in the preparation process of this thermoelectric material are not resolved. Summary of the Invention

[0006] This application provides a method for preparing thermoelectric materials, which can produce thermoelectric materials with few defects, high Seebeck coefficient, and high thermoelectric figure of merit. The method is simple, has a short preparation cycle, and does not require halogen doping to prepare thermoelectric materials, thus having the advantages of low cost and good environmental performance.

[0007] This application also provides a method for preparing thermoelectric materials, which can also prepare thermoelectric materials with few defects, high Seebeck coefficient and high thermoelectric figure of merit.

[0008] This application also provides a thermoelectric material, which is prepared by any of the above preparation methods. Therefore, the thermoelectric material has the characteristics of few defects, high Seebeck coefficient and high thermoelectric figure of merit.

[0009] This application provides a method for preparing a thermoelectric material in a first aspect, comprising:

[0010] The thermoelectric material is obtained by flash steaming and hot pressing sintering of powder containing elements M, A, and L.

[0011] Wherein, M is element IB, A is element IVA, and L is element VIA, and the difference between the element with the highest melting point and the element with the lowest melting point among elements M, A, and L is ≥700℃.

[0012] In the preparation method described above, the flash hot-pressing sintering treatment is carried out at a temperature of 800-920℃, a pressure of 45-50MPa, and a time of 5-10s.

[0013] This application provides a method for preparing a thermoelectric material in a second aspect, comprising:

[0014] The thermoelectric material is obtained by plasma sintering and flash hot pressing sintering of powder containing elements M, A, and L.

[0015] Wherein, M is element IB, A is element IVA, and L is element VIA, and the difference between the element with the highest melting point and the element with the lowest melting point among elements M, A, and L is ≥700℃.

[0016] The preparation method described above, wherein the plasma sintering treatment includes: heating the powder comprising elements M, A, and L to 630-650 K at 36-50 MPa, holding at that temperature for 2-5 min, and then cooling to room temperature; and / or,

[0017] In the flash hot-press sintering process, the temperature is 280-360℃, the pressure is 30-36MPa, and the time is 3-8s.

[0018] The powder is obtained by ball milling an ingot containing elements M, A, and L, as described above.

[0019] In the ball milling process, the rotation speed is 350-450 r / min and the time is 5-6 h.

[0020] The preparation method described above includes the following steps in the ball milling process: immersing the ingot in a solvent, then ball milling it, followed by drying it at room temperature for 10-12 hours to obtain the powder.

[0021] The solvent includes at least one of petroleum ether, pentane, hexane, heptane, octane, nonane, decane, and ethyl acetate.

[0022] The ingot is prepared by the method described above, comprising the following steps:

[0023] Sources M, A, and L are filled into a quartz tube in ascending order of melting point, and then sealed to ensure that sources M, A, and L are contained within the quartz tube.

[0024] The quartz tube is then subjected to a first calcination treatment at 350-380℃ for 1.5-2 hours; followed by a second calcination treatment at 930-950℃ at a rate of 16-20℃ / min for 3-4 hours; then cooled to 800-825℃ and held for 36-48 hours; and finally cooled to room temperature to obtain the ingot.

[0025] In the preparation method described above, the sealing pressure during the sealing process is (2-4)*10. -4 Pa.

[0026] In a third aspect, this application provides a thermoelectric material prepared by the aforementioned preparation method.

[0027] The thermoelectric material described above has the molecular formula Cu. x SnS4, x = 3 or 4.

[0028] The method for preparing thermoelectric materials provided in the first aspect of this application involves flash steaming and hot pressing sintering of powders containing elements IB (M), IVA (A), and VIA (L) to obtain the thermoelectric material. The thermoelectric material obtained by this method has few defects, a high Seebeck coefficient, and a high thermoelectric figure of merit. This preparation method is simple, has a short preparation cycle, and does not require halogen doping during the preparation process. It has the advantages of low cost and good environmental protection, and is suitable for widespread application.

[0029] The method for preparing thermoelectric materials provided in the second aspect of this application obtains thermoelectric materials by performing plasma sintering and flash hot pressing sintering on powders containing elements IB M, IVA A, and VIA L. The method can also prepare thermoelectric materials with few defects, high Seebeck coefficient, and high thermoelectric figure of merit. This preparation method is simple, has the advantages of low cost and good environmental protection, and is suitable for widespread application.

[0030] The thermoelectric material provided in this application is prepared by the above-described preparation method. This thermoelectric material has the characteristics of few defects, high Seebeck coefficient and high thermoelectric figure of merit, thus exhibiting high thermoelectric performance. Furthermore, the constituent elements of this thermoelectric material are abundant, the cost is low, and it is environmentally friendly, making it a promising thermoelectric material. Attached Figure Description

[0031] Figure 1 shows the X-ray diffraction (XRD) patterns of the thermoelectric materials of Embodiment 1, Embodiment 3, Comparative Example 1, and Comparative Example 2 of this application;

[0032] Figure 2 is the X-ray diffraction pattern (XRD) of the thermoelectric material of Embodiment 2 of this application;

[0033] Figure 3 is a graph showing the Seebeck coefficient variation of the thermoelectric materials in Embodiment 1, Comparative Example 1 and Comparative Example 2 of this application.

[0034] Figure 4 is a graph showing the electrical conductivity of the thermoelectric materials in Embodiment 1, Comparative Example 1 and Comparative Example 2 of this application.

[0035] Figure 5 is a thermal conductivity curve of the thermoelectric materials of Embodiment 1, Comparative Example 1 and Comparative Example 2 of this application;

[0036] Figure 6 is a graph showing the thermoelectric figure of merit (ZT) of the thermoelectric materials of Embodiment 1, Comparative Example 1 and Comparative Example 2 of this application. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below in conjunction with the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0038] This application provides a method for preparing a thermoelectric material, including:

[0039] Thermoelectric materials are obtained by flash steam hot pressing sintering of powders containing elements M, A, and L.

[0040] Wherein, M is element IB, A is element IVA, and L is element VIA, and the difference between the element with the highest melting point and the element with the lowest melting point among elements M, A, and L is ≥700℃.

[0041] In this application, element M is element IB. For example, element M can be one of copper (Cu), silver (Ag), and gold (Au), and is preferably copper (Cu).

[0042] Element A is element IVA. For example, element A can be one of carbon (C), silicon (Si), germanium (Ge), tin (Sn), and lead (Pb), and is preferably tin (Sn).

[0043] L is element VIA. For example, element L can be one of oxygen (O), sulfur (S), selenium (Se), tellurium (Te), and polonium (Po), and is preferably sulfur (S).

[0044] In this application, flash hot-press sintering rapidly heats the powder using electrical pulses within an extremely short time (milliseconds to seconds), reaching temperatures exceeding 1000K, enabling the rapid preparation and shaping of thermoelectric materials. In some embodiments, ultra-fast flash hot-press sintering equipment can be used for the flash hot-press sintering process.

[0045] This application prepares thermoelectric materials by flash hot-pressing sintering of powders containing elements IB, IVA, and VIA. The Joule-driven flash hot-pressing sintering process enables phase transformation of the powder and synthesis of the thermoelectric material within milliseconds. Due to the extremely short synthesis time, low-melting-point materials are difficult to volatilize from the bulk phase, ensuring the proportions of each chemical element and guaranteeing phase purity. Furthermore, the rapid heating and cooling cause rapid melting and crystallization, reducing defects and increasing the crystallinity of the thermoelectric material, thus yielding a thermoelectric material with high Seebeck coefficient and high thermoelectric figure of merit. This method is particularly suitable for elements with large melting point differences, especially when the difference between the highest and lowest melting point among elements M, A, and L is ≥700℃. This method can produce thermoelectric materials with higher crystallinity, phase purity, Seebeck coefficient, and thermoelectric figure of merit in a shorter time. This preparation method is simple to operate, has a short preparation cycle, and is suitable for widespread application.

[0046] This application does not impose specific limitations on the parameters of flash hot-press sintering treatment; the parameters can be selected according to actual needs. In one specific embodiment, the flash hot-press sintering treatment is carried out at a temperature of 800-920℃, a pressure of 45-50MPa, and a time of 5-10s.

[0047] When the temperature, pressure, and time parameters of the flash hot-pressing sintering process are within the above range, thermoelectric materials with fewer defects, a high Seebeck coefficient, and a high thermoelectric figure of merit can be prepared in a shorter time.

[0048] For example, in the flash hot pressing sintering process, the temperature can be any or any combination of 800°C, 820°C, 840°C, 860°C, 880°C, 900°C and 920°C.

[0049] The pressure can be any or any combination of 45MPa, 46MPa, 47MPa, 48MPa, 49MPa, 50MPa, 51MPa, 52MPa, 53MPa, 54MPa and 55MPa.

[0050] The time can be any or any combination of 5s, 6s, 7s, 8s, 9s, and 10s.

[0051] This application also provides a method for preparing a thermoelectric material, including:

[0052] Thermoelectric materials are obtained by plasma sintering and flash hot pressing sintering of powders containing elements M, A, and L.

[0053] Wherein, M is element IB, A is element IVA, and L is element VIA, and the difference between the element with the highest melting point and the element with the lowest melting point among elements M, A, and L is ≥700℃.

[0054] In this application, plasma sintering treatment refers to the technique of heating, solidifying, and sintering powder by applying pulsed current and a certain pressure.

[0055] Specifically, this application involves first performing plasma sintering on powders containing elements IB, IVA, and VIA to obtain an intermediate thermoelectric material. Then, the intermediate thermoelectric material undergoes flash hot-pressing sintering to homogenize the components, resulting in a thermoelectric material with excellent crystallinity, phase purity, Seebeck coefficient, and thermoelectric figure of merit. The preparation method of this thermoelectric material is particularly suitable for elements with large melting point differences. Especially when the difference between the melting point of the element with the highest melting point and the element with the lowest melting point among elements M, A, and L is ≥700℃, this method can yield thermoelectric materials with even higher crystallinity, phase purity, Seebeck coefficient, and thermoelectric figure of merit. The preparation method of this application is simple to operate and has a short preparation cycle, making it suitable for widespread application.

[0056] This application does not impose specific limitations on the parameters of plasma sintering treatment; the parameters can be selected according to actual needs. In one specific embodiment, the plasma sintering treatment includes: heating a powder containing elements M, A, and L to 630-650K at 36-50MPa, holding at that temperature for 2-5 minutes, and then cooling to room temperature.

[0057] When powders containing elements M, A, and L are subjected to plasma sintering treatment using the method described above, thermoelectric materials with high thermoelectric performance can be finally prepared.

[0058] In one specific embodiment, the flash hot-press sintering process is carried out at a temperature of 280-360℃, a pressure of 30-36MPa, and a time of 3-8s.

[0059] When the temperature, pressure, and time parameters of the flash hot-pressing sintering process are within the above range, thermoelectric materials with fewer defects, a high Seebeck coefficient, and a high thermoelectric figure of merit can be prepared in a shorter time.

[0060] For example, in the flash hot pressing sintering process, the temperature can be any one of 280°C, 300°C, 320°C, 360°C, or a combination of any two of them.

[0061] The pressure can be any one of 30MPa, 32MPa, 35MPa, 36MPa or any combination of two of them;

[0062] The time can be any one of 3s, 4s, 6s, 7s, 8s, or any combination of two.

[0063] In one specific embodiment, the powder is obtained by ball milling an ingot containing elements M, A, and L.

[0064] During ball milling, the rotation speed is 350-450 r / min and the time is 5-6 h.

[0065] Specifically, ingots containing M, A, and L elements can be ball-milled at a speed of 350-450 r / min for 5-6 hours to obtain powder.

[0066] This application uses the above parameters to ball mill ingots containing elements M, A, and L to prepare powder, which enables the ingots containing elements M, A, and L to be more uniformly distributed in the powder, reducing intrinsic defects (such as elemental segregation) in the thermoelectric material during the preparation process, and is beneficial to obtaining thermoelectric materials with high crystallinity and phase purity. At the same time, ball milling can increase the specific surface area of ​​the powder, which is beneficial to subsequent flash hot pressing sintering treatment.

[0067] For example, in ball milling, the rotational speed can be any or any combination of 350 r / min, 360 r / min, 370 r / min, 380 r / min, 390 r / min, 400 r / min, 410 r / min, 420 r / min, 430 r / min, 440 r / min and 450 r / min;

[0068] The time can be any or any combination of 5h, 5.2h, 5.4h, 5.6h, 5.8h and 6h.

[0069] Furthermore, the ball milling process includes: immersing the ingot in a solvent, then ball milling it, followed by drying it at room temperature for 10-12 hours to obtain powder;

[0070] The solvent includes at least one of petroleum ether, pentane, hexane, heptane, octane, nonane, decane, and ethyl acetate.

[0071] Specifically, the ball milling process includes: immersing the ingot in a solvent, then ball milling the ingot to reduce friction between the milling media and the ingot during the milling process, thereby reducing heat accumulation and preventing vaporization of the ingot due to overheating, which could lead to elemental segregation. The ingot is then dried at room temperature for 10-12 hours to thoroughly remove the solvent and obtain a dry powder.

[0072] The ball milling process described above can further prevent elemental segregation during the preparation of thermoelectric materials and improve their thermoelectric performance.

[0073] In one specific embodiment, the ingot is prepared by a method comprising the following steps:

[0074] Sources M, A, and L are filled into a quartz tube in ascending order of melting point, and then sealed to ensure that sources M, A, and L are contained within the quartz tube.

[0075] The quartz tube is then subjected to a first calcination treatment at 350-380℃ for 1.5-2 hours; followed by a second calcination treatment at 930-950℃ at a rate of 16-20℃ / min for 3-4 hours; then cooled to 800-825℃ and held for 36-48 hours; finally cooled to room temperature to obtain the ingot.

[0076] In this application, source M can be a compound commonly used in the art that contains element M. Source A can be a compound commonly used in the art that contains element A. Source L can be a compound commonly used in the art that contains element L.

[0077] Specifically, the ingot can be prepared by the following steps: M source, A source, and L source are filled into a quartz tube in ascending order of melting point to prevent low-melting-point materials from volatilizing upwards and high-melting-point materials from accumulating at the bottom of the quartz tube during subsequent calcination, thus preventing contact with the high-melting-point materials and ultimately leading to an imbalance in the elemental composition of the material. The tube is then sealed to ensure the M, A, and L sources are fully contained within it. Next, the quartz tube containing the M, A, and L sources is placed at 350-380℃ for a first calcination treatment of 1.5-2 hours to completely vaporize or liquefy the L source. Then, the temperature is increased to 930-950℃ at a rate of 16-20℃ / min for a second calcination treatment of 3-4 hours to ensure complete melting of the M, A, and L sources and thorough mixing of the elements. The tube is then cooled to 800-825℃ and held for 36-48 hours to form a thermoelectric material structure with thermoelectric properties, while simultaneously eliminating defects in the material's crystal lattice. Finally, the tube is cooled to room temperature to obtain the ingot.

[0078] In some embodiments, the quartz tube can be placed in a muffle furnace for a first calcination treatment, a second calcination treatment, cooling, and heat preservation in sequence.

[0079] The above method can produce ingots with fewer defects, which helps to form thermoelectric materials with high crystallinity and phase purity.

[0080] In one specific embodiment, the sealing pressure during the sealing process is (2-4)*10. -4 Pa.

[0081] When the pressure parameters of the sealing process are within the above range, the M source, L source and A source can be better sealed in the quartz tube to prevent the M source, A source and L source from volatilizing during the subsequent calcination process, thereby improving the thermoelectric performance of the thermoelectric material.

[0082] For example, the sealing pressure can be 2*10 -4 Pa, 3*10 -4 Pa and 4*10 -4 The range consisting of any one or both of Pa.

[0083] This application also provides a thermoelectric material prepared by the above-described preparation method.

[0084] The thermoelectric material of this application can be an n-type thermoelectric material or a p-type thermoelectric material.

[0085] The thermoelectric material of this application is prepared by the above-described preparation method. The thermoelectric material has the characteristics of few defects, high Seebeck coefficient and high thermoelectric figure of merit. In addition, the constituent elements of the thermoelectric material are abundant, the cost is low and the environmental protection is good, and it has high application potential.

[0086] In one specific embodiment, the thermoelectric material has the molecular formula Cu. x SnS4, x = 3 or 4.

[0087] When the molecular formula of the thermoelectric material is Cu x When the molecular formula of the thermoelectric material is Cu3SnS4 or Cu4SnS4, x = 3 or 4, it is possible to obtain thermoelectric materials with fewer defects, higher Seebeck coefficient, and higher thermoelectric figure of merit.

[0088] This application provides a detailed description of its implementation methods through the following examples and comparative models.

[0089] Example 1

[0090] The method for preparing the thermoelectric material in this embodiment includes:

[0091] The raw materials, Cu, Sn, and S, were weighed separately in a stoichiometric ratio of 3:1:4. Then, following an increasing order of melting point, the Cu, Sn, and S sources were filled into a cleaned quartz tube and sealed. The sealing pressure was 2.5 × 10⁻⁶. -4 Pa;

[0092] The sealed quartz tube is then placed in a muffle furnace and subjected to a first firing treatment at 350°C for 1.5 hours; then the temperature is increased to 950°C at 20°C / min for a second firing treatment for 3 hours; then the temperature is cooled to 800°C in the muffle furnace and held for 38 hours; and finally cooled to room temperature in the muffle furnace to obtain the ingot.

[0093] The ingot was placed in a ball mill, and petroleum ether was added to ensure that the ingot was completely submerged. The ingot was then ball-milled at 350 r / min for 5 hours. After ball milling, the ingot was dried at room temperature for 10 hours to obtain powder.

[0094] The powder was placed in an ultra-fast flash hot-press sintering equipment and subjected to flash hot-press sintering treatment at a temperature of 800℃ and a pressure of 45MPa for 6s to obtain the thermoelectric material Cu3SnS4.

[0095] Example 2

[0096] The method for preparing the thermoelectric material in this embodiment includes:

[0097] The raw materials, Cu source, Sn source, and S source, were weighed separately in a stoichiometric ratio of 4:1:4. Then, following an increasing order of melting point, the Cu, Sn, and S sources were filled into a cleaned quartz tube and sealed. The sealing pressure was 3*10⁻⁶. -4 Pa;

[0098] The sealed quartz tube was then placed in a muffle furnace and subjected to a first firing treatment at 350°C for 1.8 hours; then the temperature was increased to 950°C at 20°C / min for a second firing treatment for 3.5 hours; then the temperature was cooled to 800°C in the muffle furnace and held for 40 hours; and finally cooled to room temperature in the muffle furnace to obtain the ingot.

[0099] The ingot was placed in a ball mill, and petroleum ether was added to ensure that the ingot was completely submerged. The ingot was then ball-milled at 380 r / min for 6 hours. After ball milling, the ingot was dried at room temperature for 11 hours to obtain powder.

[0100] The powder was placed in an ultra-fast flash hot-press sintering equipment and subjected to flash hot-press sintering treatment at a temperature of 860℃ and a pressure of 46MPa for 7s to obtain the thermoelectric material Cu4SnS4.

[0101] Example 3

[0102] The method for preparing the thermoelectric material in this embodiment includes:

[0103] The raw materials, Cu, Sn, and S, were weighed separately in a stoichiometric ratio of 3:1:4. Then, following an increasing order of melting point, the Cu, Sn, and S sources were filled into a cleaned quartz tube and sealed. The sealing pressure was 3.2 × 10⁻⁶. -4 Pa;

[0104] The sealed quartz tube is then placed in a muffle furnace and subjected to a first firing treatment at 350°C for 2 hours; then the temperature is increased to 950°C at 20°C / min for a second firing treatment for 4 hours; then it is cooled to 800°C in the muffle furnace and held for 43 hours; then it is cooled to room temperature in the muffle furnace to obtain the ingot.

[0105] The ingot was placed in a ball mill, and petroleum ether was added to ensure that the ingot was completely submerged. The ingot was then ball-milled at a speed of 450 r / min for 6 hours. After ball milling, the ingot was dried at room temperature for 12 hours to obtain powder.

[0106] The powder was placed in a mold and heated to 650K at 50MPa for plasma sintering for 5 minutes. After cooling to room temperature, the plasma-sintered product was obtained.

[0107] The plasma-sintered product was placed in an ultra-fast flash hot-press sintering equipment and subjected to flash hot-press sintering treatment at a temperature of 350℃ and a pressure of 32MPa for 6s to obtain the thermoelectric material Cu3SnS4.

[0108] Example 4

[0109] The method for preparing the thermoelectric material in this embodiment includes:

[0110] The raw materials, Cu source, Sn source, and S source, were weighed separately according to a stoichiometric ratio of 4:1:4. Then, in ascending order of melting point, the Cu source, Sn source, and S source were filled into a cleaned quartz tube and sealed. The sealing pressure was 4*10. -4 Pa;

[0111] The sealed quartz tube was then placed in a muffle furnace and subjected to a first firing treatment at 350°C for 1.9 hours; then the temperature was increased to 950°C at 20°C / min for a second firing treatment for 4 hours; then the temperature was cooled to 800°C in the muffle furnace and held for 47 hours; and then the temperature was cooled to room temperature in the muffle furnace to obtain the ingot.

[0112] The ingot was placed in a ball mill, and petroleum ether was added to ensure that the ingot was completely submerged. The ingot was then ball-milled at 370 r / min for 5.5 h. After ball milling, the ingot was dried at room temperature for 11 h to obtain powder.

[0113] The powder was placed in a mold and heated to 650K at 50MPa for 4 minutes for plasma sintering. After cooling to room temperature, the plasma-sintered product was obtained.

[0114] The plasma-sintered product was placed in an ultra-fast flash hot-press sintering equipment and subjected to flash hot-press sintering treatment at a temperature of 350℃ and a pressure of 35MPa for 4s to obtain the thermoelectric material Cu4SnS4.

[0115] Comparative Example 1

[0116] The preparation method of the thermoelectric material in this comparative example includes:

[0117] The raw materials, Cu, Sn, and S, were weighed separately in a stoichiometric ratio of 3:1:4. Then, following an increasing order of melting point, the Cu, Sn, and S sources were filled into a cleaned quartz tube and sealed. The sealing pressure was 2.5 × 10⁻⁶. -4 Pa;

[0118] The sealed quartz tube is then placed in a muffle furnace and subjected to a first firing treatment at 350°C for 1.5 hours; then the temperature is increased to 950°C at 20°C / min for a second firing treatment for 3 hours; then the temperature is cooled to 800°C in the muffle furnace and held for 38 hours; and finally cooled to room temperature in the muffle furnace to obtain the ingot.

[0119] The ingot was placed in a ball mill, and petroleum ether was added to ensure that the ingot was completely submerged. The ingot was then ball-milled at 350 r / min for 5 hours. After ball milling, the ingot was dried at room temperature for 10 hours to obtain powder.

[0120] The powder was placed in a mold and heated to 650K at 50MPa for plasma sintering treatment for 5 minutes. After cooling to room temperature, the thermoelectric material Cu3SnS4 was obtained.

[0121] Comparative Example 2

[0122] The preparation method of the thermoelectric material in this comparative example includes:

[0123] The raw materials, Cu, Sn, and S, were weighed separately in a stoichiometric ratio of 3:1:4. Then, following an increasing order of melting point, the Cu, Sn, and S sources were filled into a cleaned quartz tube and sealed. The sealing pressure was 2.5 × 10⁻⁶. -4 Pa;

[0124] The sealed quartz tube is then placed in a muffle furnace and subjected to a first firing treatment at 350°C for 1.5 hours; then the temperature is increased to 950°C at 20°C / min for a second firing treatment for 3 hours; then the temperature is cooled to 800°C in the muffle furnace and held for 38 hours; and finally cooled to room temperature in the muffle furnace to obtain the ingot.

[0125] The ingot was placed in a ball mill, and petroleum ether was added to ensure that the ingot was completely submerged. The ingot was then ball-milled at 350 r / min for 5 hours. After ball milling, the ingot was dried at room temperature for 10 hours to obtain powder.

[0126] The powder was placed in a mold and hot-pressed at 200℃ and 1MPa for 0.5 hours to obtain the thermoelectric material Cu3SnS4.

[0127] Performance Characterization

[0128] 1. X-ray diffraction pattern (XRD):

[0129] XRD tests were performed on the thermoelectric materials in the examples and comparative examples to obtain the XRD patterns of the thermoelectric materials in the examples and comparative example 1.

[0130] Figure 1 shows the X-ray diffraction patterns of the thermoelectric materials Cu3SnS4 in Examples 1, 3, Comparative Examples 1 and 2 of this application, and Figure 2 shows the X-ray diffraction pattern (XRD) of the thermoelectric material Cu4SnS4 in Example 2 of this application.

[0131] As shown in Figure 1, the Cu3SnS4 material prepared in the example has higher diffraction peak intensity and no CuO impurity peaks, indicating that the present application can obtain Cu3SnS4 material with higher crystallinity and pure phase through flash hot pressing sintering treatment.

[0132] As shown in Figure 2, Cu4SnS4 thermoelectric material was prepared in Example 2. The inventors discovered that plasma sintering or hot pressing alone could not produce Cu4SnS4 thermoelectric material with an atomic ratio of 4:1:4; the resulting material was still Cu3SnS4. This indicates that combining flash hot pressing sintering or plasma sintering with flash hot pressing sintering can significantly suppress elemental segregation and phase separation when synthesizing thermoelectric materials with significantly different element melting points.

[0133] 2. Thermoelectric properties

[0134] (1) Seebeck coefficient

[0135] The thermoelectric materials in the examples and comparative examples were placed in a non-uniform temperature field, so that there was a temperature difference between the two ends of the thermoelectric materials. The temperature difference and the corresponding thermoelectric potential difference were measured respectively, and the temperature difference was divided by the thermoelectric potential difference.

[0136] (2) Conductivity

[0137] The thermoelectric materials in the examples and comparative examples were prepared into long strip samples. The cross-sectional area s (width and thickness) and the distance between the two probe thermocouples of the device were measured. When a constant current was applied between the upper and lower main electrodes, the voltage between the two probes was measured. The conductivity of the thermoelectric material was calculated according to Ohm's law.

[0138] (3) Thermal conductivity

[0139] The thermoelectric material is prepared into a circular sample, and the cross-sectional area s (width and thickness) and the distance between the upper and lower temperature sensors of the device are measured. When a constant heat source is applied from the top and bottom, the temperature difference between the two probes is measured, and the thermal conductivity of the thermoelectric material is calculated according to the thermal resistance formula.

[0140] (4) Thermoelectric figure of merit (ZT)

[0141] The Seebeck coefficient (S), electrical conductivity (σ), and thermal conductivity (κ) were measured at different temperatures (T), and then the equation ZT = S was defined. 2 σT / κ is calculated.

[0142] Figure 3 shows the Seebeck coefficient curves of the thermoelectric materials of Embodiment 1, Comparative Example 1, and Comparative Example 2 of this application; Figure 4 shows the electrical conductivity curves of the thermoelectric materials of Embodiment 1, Comparative Example 1, and Comparative Example 2 of this application; Figure 5 shows the thermal conductivity curves of the thermoelectric materials of Embodiment 1, Comparative Example 1, and Comparative Example 2 of this application; Figure 6 shows the thermoelectric figure of merit (ZT) curves of the thermoelectric materials of Embodiment 1, Comparative Example 1, and Comparative Example 2 of this application.

[0143] As shown in Figures 3-6, compared with the thermoelectric materials prepared by the method of Comparative Example 1 and the method of Comparative Example 2, the thermoelectric material prepared by the method of Example 1 has lower thermal conductivity and higher Seebeck coefficient. Moreover, the ZT value of the thermoelectric material of Example 1 can reach 0.8, which shows that the method provided in this application can prepare thermoelectric materials with high Seebeck coefficient and high thermoelectric figure of merit.

[0144] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for preparing a thermoelectric material, wherein, include: The thermoelectric material is obtained by flash steaming and hot pressing sintering of powder containing elements M, A, and L. Wherein, M is element IB, A is element IVA, and L is element VIA, and the difference between the element with the highest melting point and the element with the lowest melting point among elements M, A, and L is ≥700℃.

2. The preparation method according to claim 1, wherein, In the flash hot-press sintering process, the temperature is 800-920℃, the pressure is 45-50MPa, and the time is 5-10s.

3. A method for preparing a thermoelectric material, wherein, include: The thermoelectric material is obtained by plasma sintering and flash hot pressing sintering of powder containing elements M, A, and L. Wherein, M is element IB, A is element IVA, and L is element VIA, and the difference between the element with the highest melting point and the element with the lowest melting point among elements M, A, and L is ≥700℃.

4. The preparation method according to claim 3, wherein, The plasma sintering treatment includes: heating the powder containing elements M, A, and L to 630-650K at 36-50MPa, holding at that temperature for 2-5 minutes, and then cooling to room temperature; and / or, In the flash hot-press sintering process, the temperature is 280-360℃, the pressure is 30-36MPa, and the time is 3-8s.

5. The preparation method according to any one of claims 1-4, wherein, The powder is obtained by ball milling an ingot containing elements M, A, and L. In the ball milling process, the rotation speed is 350-450 r / min and the time is 5-6 h.

6. The preparation method according to claim 5, wherein, The ball milling process includes: immersing the ingot in a solvent, then ball milling it, followed by drying it at room temperature for 10-12 hours to obtain the powder. The solvent includes at least one of petroleum ether, pentane, hexane, heptane, octane, nonane, decane, and ethyl acetate.

7. The preparation method according to claim 5 or 6, wherein, The ingot is prepared by a method comprising the following steps: Sources M, A, and L are filled into a quartz tube in ascending order of melting point, and then sealed to ensure that sources M, A, and L are contained within the quartz tube. The quartz tube is then subjected to a first calcination treatment at 350-380℃ for 1.5-2 hours; followed by a second calcination treatment at 930-950℃ at a rate of 16-20℃ / min for 3-4 hours; then cooled to 800-825℃ and held for 36-48 hours; and finally cooled to room temperature to obtain the ingot.

8. The preparation method according to claim 7, wherein, In the sealing process, the sealing pressure is (2-4)*10. -4 Pa.

9. A thermoelectric material, wherein, It is prepared by the preparation method according to any one of claims 1-8.

10. The thermoelectric material according to claim 9, wherein, The molecular formula of the thermoelectric material is Cu. x SnS4, x = 3 or 4.

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