Mg3Sb2-xBix material and thermoelectric and mechanical property coordinated regulation and control method based on room temperature deformation technology

Abstract

The invention relates to the technical field of thermoelectric material preparation, in particular to a Mg3Sb2-xBix material and a thermoelectric and mechanical property coordinated regulation method based on a room temperature deformation technology, and the method comprises the steps: providing a blocky Mg3Sb2-xBix thermoelectric material, xlt; 2; the Mg < 3 > Sb < 2-x > Bi < x > thermoelectric raw material comprises an anion doped element and / or a cation original element doped element; carrying out compression deformation on the blocky Mg < 3 > Sb < 2-x > Bi < x > thermoelectric raw material at room temperature; annealing treatment is conducted on the blocky Mg3Sb2-xBix thermoelectric raw material subjected to compression deformation, high-density microdefects (such as dislocation and twin crystals) are introduced through plastic deformation under the room temperature condition, then the subsequent low-temperature annealing process is combined, accurate regulation and control over the defect types are achieved, namely dislocation unfavorable for thermoelectric performance is selectively eliminated, and the defect type is obtained. And meanwhile, twin crystals contributing to improvement of thermoelectric and mechanical properties are reserved, so that collaborative optimization of the thermoelectric and mechanical properties is achieved.

Description

Technical Field

[0001] This application relates to the field of thermoelectric material preparation technology, specifically to a Mg3Sb 2-x Bi x Materials and methods for synergistic regulation of thermoelectric and mechanical properties based on room temperature deformation technology. Background Technology

[0002] Thermoelectric materials are a class of functional materials capable of directly converting heat energy into electrical energy and vice versa. Their physical basis lies in the Seebeck effect (heat energy → electrical energy) and the Peltier effect (electrical energy → heat energy). This characteristic gives thermoelectric technology unique application value in fields such as waste heat recovery power generation, solid-state refrigeration, and high-precision temperature control. The core indicator for measuring the energy conversion efficiency of thermoelectric materials is the dimensionless thermoelectric figure of merit (zT), defined as zT = (S... 2 T) / ρκ, where S is the Seebeck coefficient, ρ is the resistivity, T is the absolute temperature, and κ is the thermal conductivity. Therefore, the key to improving the zT value lies in synergistically optimizing electrical transport performance (improving the power factor PF=S). 2 / ρ) and thermal transport properties (reducing thermal conductivity κ).

[0003] Currently, significant progress has been made in optimizing the electroacoustic transport properties and improving the zT value of materials through strategies such as element doping, alloying, bandgap engineering, and nanostructuring. However, in industrial applications, thermoelectric devices must withstand complex conditions such as machining loads and long-term service thermal stress. Insufficient mechanical properties (such as strength, toughness, and machinability) of the material will directly lead to low device fabrication yield, degraded service reliability, and shortened service life, thus severely restricting its large-scale commercial application. Although existing research has confirmed that defect engineering (such as introducing dislocations and twins) can effectively enhance mechanical properties and strain engineering can control electrical transport properties, these two approaches have not yet been systematically integrated, and a unified process scheme that can simultaneously optimize thermoelectric and mechanical properties is lacking.

[0004] At the level of specific material systems, Bi2Te3-based materials are currently the only thermoelectric system to achieve large-scale commercial applications. However, their intrinsic brittleness leads to difficulties in precision machining and poor device integration reliability. Furthermore, the high cost of the key element Te limits their application in a wider range of scenarios. In recent years, Mg3Sb... 2-x Bi x Bi2Te3-based thermoelectric materials have become a research hotspot for the next generation of thermoelectric materials due to their excellent thermoelectric properties in a temperature range close to room temperature (zT value comparable to Bi2Te3-based materials), the abundance and low cost of the raw material (Mg), and especially their outstanding room temperature plastic deformation ability (fracture strain can reach more than 30%).

[0005] The material's unique room-temperature plasticity brings significant advantages for industrialization. Firstly, the low risk of material breakage during preparation improves yield. Secondly, high-density micro-defects can be introduced through plastic deformation without requiring a high-temperature, high-pressure environment, providing more possibilities for performance control. Thirdly, the process is simplified, and energy consumption is reduced. Therefore, based on Mg3Sb... 2-x Bi x Given the aforementioned properties of the material, developing an advanced process that can synergistically regulate its thermoelectric and mechanical properties is of paramount importance for promoting the large-scale application of high-performance thermoelectric materials.

[0006] Existing typical technical solutions usually include the following steps: weighing raw materials according to stoichiometric ratios, preparing alloy powder through high-energy ball milling, and then obtaining dense bulk materials using spark plasma sintering technology. Subsequent processing mainly includes: annealing, performed under vacuum or inert atmosphere, aimed at eliminating sintering internal stress and precisely adjusting carrier concentration to optimize electrical conductivity and Seebeck coefficient; and hot deformation treatment, such as hot extrusion and hot rolling, which introduces defects such as grain texture and dislocations through plastic deformation at high temperatures, aiming to improve mechanical properties (such as flexural strength and ductility) while simultaneously reducing lattice thermal conductivity through defect scattering, achieving a synergistic improvement in thermoelectric and mechanical properties.

[0007] Its conventional process flow can be briefly described as follows: Powder synthesis → SPS sintering → Hot extrusion → Annealing; Powder synthesis → SPS sintering → Hot rolling → Texture control → Stabilization annealing; Sintering → Hot forging → Stress relief annealing → Performance testing; However, these existing solutions generally rely on high-temperature deformation and processing, which not only consumes a lot of energy, but also easily leads to compositional deviations in systems containing volatile element Mg, affecting the stability of the final material properties. Summary of the Invention

[0008] In view of this, this application provides a Mg3Sb 2-x Bi x This application proposes a method for synergistic regulation of thermoelectric and mechanical properties based on room temperature deformation technology to address the technical problem of unstable material properties in existing technologies. To achieve one, some, or all of the above objectives, or other objectives, this application provides a Mg3Sb... 2-x Bi x Methods for synergistic regulation of thermoelectric and mechanical properties of materials based on room temperature deformation technology include: Provide bulk Mg3Sb 2-x Bi x Thermoelectric raw materials, wherein 0 ≤ x ≤ 2; the Mg3Sb2-x Bi x Thermoelectric raw materials include anion-doped elements and / or cationic-doped elements; The blocky Mg3Sb 2-x Bi x Thermoelectric raw materials undergo compression deformation at room temperature; The compressed and deformed blocky Mg3Sb 2-x Bi x Thermoelectric raw materials undergo annealing treatment.

[0009] Preferably, the anion doping element is at least one of Te, Se, and S; The cation doping element is at least one of Sc, Y, La, Pr, Ce, Ag, and Mn.

[0010] Preferably, the blocky Mg3Sb 2-x Bi x The preparation method of thermoelectric raw materials is as follows: Weigh out the corresponding mass of each element in the raw material; The weighed elemental raw materials are mixed and then ball-milled into metal powder under a protective atmosphere; The metal powder was loaded into a mold and sintered into block Mg3Sb under vacuum. 2-x Bi x Thermoelectric raw materials, obtaining Mg3Sb with synergistic improvement in thermoelectric and mechanical properties. 2-x Bi x Material.

[0011] Preferably, in Mg3Sb 2-x Bi x The metal powder is sintered at 0.5-0.8 times the melting point temperature of the thermoelectric raw material.

[0012] Preferably, the sintering method is spark plasma sintering, and the sintering time is 2-5 minutes.

[0013] Preferably, the ball milling time is 6-10 hours, and the particle size of the metal powder is 5-20 μm.

[0014] Preferably, 0.45≤x≤1.55.

[0015] Preferably, bulk Mg3Sb 2-x Bi x The strain of thermoelectric raw materials after compression deformation is 10%-15%.

[0016] Preferably, the annealing temperature is 473-773K and the annealing time is 30-60 minutes.

[0017] Another aspect of this application also provides a Mg3Sb 2-x Bi x Materials, such as Mg3Sb as described in any of the above. 2- x Bi x The material was prepared using a method that synergistically regulates the thermoelectric and mechanical properties based on room temperature deformation technology.

[0018] Implementing the embodiments of this application will have the following beneficial effects: This invention is based on Mg3Sb 2-x Bi x The unique room-temperature plastic deformation capability of the base material, compared to other intrinsically brittle thermoelectric materials, allows for the introduction of high-density micro-defects (such as dislocations and twins) through plastic deformation at room temperature. Combined with subsequent low-temperature annealing, this enables precise control over defect types—selectively eliminating dislocations detrimental to thermoelectric performance while retaining twins that enhance thermoelectric and mechanical properties, thus achieving synergistic optimization of thermoelectric and mechanical properties. This process offers the following significant advantages: Simplified process and low equipment requirements: Since plastic deformation can be achieved without high temperatures, the stringent requirements for deformation equipment are reduced, making the process faster and simpler. Reduced energy consumption and stable composition: By avoiding high-temperature treatment, energy consumption during preparation is significantly reduced, and the loss of volatile elements such as Mg is effectively suppressed, ensuring the accuracy of material composition and the stability of performance.

[0019] Synergistic performance enhancement: The twins in the material are preserved after annealing, while the dislocation density is significantly reduced; for example, the yield strength and hardness of the sample treated by "strain + annealing" are significantly improved, achieving simultaneous enhancement of thermoelectric and mechanical properties. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] in: Figure 1 In one embodiment, blocky Mg 3.2 Sb 1.5 Bi 0.49 Te 0.01 Materials and bulk Mg 3.2 Sb 0.49 Bi 1.5 Te 0.01Schematic diagram of the intrinsic properties of the material.

[0022] Figure 2 In one embodiment, blocky Mg 3.2 Sb 1.5 Bi 0.49 Te 0.01 Materials and Mg 3.2 Sb 0.49 Bi 1.5 Te 0.01 Schematic diagram of the stress-strain curve of the material; Figure 3 For example, Mg under different compressive strains in one embodiment 3.2 Sb 1.5 Bi 0.49 Te 0.01 Performance change diagram; Figure 4 For example, Mg under different compressive strains in one embodiment 3.2 Sb 0.49 Bi 1.5 Te 0.01 Performance change diagram; Figure 5 For example, Mg under different compressive strains in one embodiment 3.2 Sb 1.5 Bi 0.49 Te 0.01 Schematic diagram of the microstructure of internal twinning variations; Figure 6 For example, Mg under different compressive strains in one embodiment 3.2 Sb 1.5 Bi 0.49 Te 0.01 A schematic diagram of the microstructure of internal dislocation changes; Figure 7 For example, Mg under different compressive strains in one embodiment 3.2 Sb 0.49 Bi 1.5 Te 0.01 Schematic diagram of the microstructure of internal twinning variations; Figure 8 For example, Mg under different compressive strains in one embodiment 3.2 Sb 0.49 Bi 1.5 Te 0.01 Schematic diagram of internal dislocation changes; Figure 9 In one embodiment, annealed Mg 3.2 Sb 1.5 Bi 0.49 Te 0.01 Schematic diagram illustrating the changes in thermoelectric properties; Figure 10In one embodiment, annealed Mg 3.2 Sb 0.49 Bi 1.5 Te 0.01 Schematic diagram of thermoelectric performance changes; Figure 11 In one embodiment, annealed Mg 3.2 Sb 1.5 Bi 0.49 Te 0.01 Schematic diagram of changes in internal twins and dislocations; Figure 12 In one embodiment, annealed Mg 3.2 Sb 0.49 Bi 1.5 Te 0.01 Schematic diagram of changes in internal twins and dislocations; Figure 13 For one embodiment, strain and annealing of Mg 3.2 Sb 1.5 Bi 0.49 Te 0.01 and Mg 3.2 Sb 0.49 Bi 1.5 Te 0.01 Schematic diagram of yield strength variation of the two components; Figure 14 For one embodiment, strain and annealing of Mg 3.2 Sb 1.5 Bi 0.49 Te 0.01 and Mg 3.2 Sb 0.49 Bi 1.5 Te 0.01 Schematic diagram of hardness changes in the two components; Figure 15 Mg in one embodiment 3.2 Sb 1.5 Bi 0.49 Te 0.01 The relationship between strain and annealing carrier concentration and Hall mobility with temperature T is shown in the curves. Figure 16 For example, strain and Mg after annealing in one embodiment 3.2 Sb 0.49 Bi 1.5 Te 0.01 The relationship between strain, annealing carrier concentration, Hall mobility, and temperature T is shown in the curves. Detailed Implementation

[0023] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings. Preferred embodiments of this application are shown in the drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of this application.

[0024] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein in the specification of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application.

[0025] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0026] In this application, numerical ranges are referred to as continuous unless otherwise specified, and include the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0027] In this application, when referring to units of data ranges, if the unit is only followed by the right endpoint, it indicates that the units of the left and right endpoints are the same. For example, 10 1000nm means that the units for both the left endpoint "10" and the right endpoint "1000" are nm (nanometers).

[0028] In this application, terms such as "multiple," "various," and "repeatedly" are used unless otherwise specified, referring to a quantity greater than or equal to 2. For example, "multiple" means two or more. This document only specifically discloses some numerical ranges. However, any lower limit can be combined with any upper limit to form an unspecified range; and any lower limit can be combined with other lower limits to form an unspecified range, just as any upper limit can be combined with any other upper limit to form an unspecified range. Furthermore, each individually disclosed point or single value can itself serve as a lower or upper limit and be combined with any other point or single value or with other lower or upper limits to form an unspecified range.

[0029] The "scope" disclosed in this application is defined by a lower limit and an upper limit. A given scope is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific scope. The scope defined in this way may include end values ​​or not.

[0030] Unless otherwise specified, the temperature parameters in this application may be either constant temperature processing or processing within a certain temperature range. The constant temperature processing allows for temperature fluctuations within the precision range controlled by the instrument.

[0031] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions. Unless otherwise specified, all technical features and optional technical features of this application can be combined to form new technical solutions.

[0032] Unless otherwise specified, all steps of this application may be performed sequentially or randomly, but sequentially is preferred.

[0033] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0034] In some embodiments, a Mg3Sb is provided. 2-x Bi x A method for synergistic regulation of the thermoelectric and mechanical properties of materials based on room temperature deformation technology includes the following steps: S1: Provides bulk Mg3Sb 2-x Bi x Thermoelectric materials, of which 0 <x<2;Mg3Sb 2-x Bi x Thermoelectric raw materials include anion-doped elements and / or cationic-doped elements.

[0035] Specifically, Mg3Sb 2-x Bi x Thermoelectric raw material is Mg3Sb 2-x Bi xThis is a basic thermoelectric material, doped with anionic and / or cationic elements. Its composition is not fixed; the system has no miscibility gaps, and Sb and Bi can form a continuous solid solution across the entire composition range. Beyond this range (x < 0 or x > 2), the material is no longer a solid solution but a single-phase compound (x = 0 is Mg3Sb2, x = 2 is Mg3Bi2), and its thermoelectric performance deteriorates significantly. Because elemental doping requires synthesis in an environment with excess Mg to suppress Mg vacancies, n-type doping can be achieved. 2-x Bi x The amount of Mg in the thermoelectric raw materials is greater than that of Mg3Sb. 2-x Bi x The proportion of the chemical formula should be higher, for example, Mg in the specific examples below. 3.2 Sb 1.5 Bi 0.49 Te 0.01 and Mg 3.2 Sb 0.49 Bi 1.5 Te 0.01 .

[0036] When x=2, it is a single-phase Mg3Bi2, and its performance deteriorates significantly. Its crystal structure changes to a trigonal crystal system (space group). Although its structure is consistent with that of a solid solution, its lattice parameters are further expanded (a = 4.671 Å, c = 7.403 Å), and the absence of Sb atom substitution leads to the disappearance of lattice distortion. Its band structure belongs to a topological nodal line half-metal, with electron and hole pockets coexisting near the Fermi level, the band gap disappearing, and carrier types mixed. Thermoelectric properties: The absolute value of the Seebeck coefficient is significantly reduced (approaching 0 at room temperature), and the power factor collapses; although the lattice thermal conductivity is low (≈0.4 W / m²), it exhibits other characteristics. m -1 K -1 However, the overall thermoelectric figure of merit zT value decreased significantly (zT < 0.1 at room temperature). In terms of mechanical properties, the Mg-Bi bond length is greater than that of the Mg-Sb bond, the interlayer bonding force is weaker, the fracture toughness is further reduced, and it is prone to cracking during processing.

[0037] When x=0, it is a single-phase Mg3Sb2, and its properties are relatively limited. The crystal structure of pure Mg3Sb2 is a trigonal Zintl phase (space group). The crystal structure exhibits no Bi atom substitution in the lattice, resulting in weak lattice distortion and mass fluctuation scattering. It also possesses a relatively large band gap (0.4-0.7 eV) and low carrier concentration at room temperature (<10). 19 cm -3 The conduction band degeneracy (Nv = 6) was not fully optimized. In terms of thermoelectric properties, the lattice thermal conductivity is high (room temperature ≈ 1.5 W). m-1 K -1 Insufficient power factor (<1.0 mW) m -1 K -2 The zT value at room temperature is only 0.2-0.3, far below the optimal value for solid solutions. In terms of mechanical properties, the solid solution strengthening effect disappears, and the Vickers hardness and flexural strength are lower than those of Bi-doped solid solutions, with more significant brittleness.

[0038] Mg3Sb 2-x Bi x Thermoelectric raw materials are doped with anionic and / or cationic elements. Anionic doping (substituting Sb / Bi sites) aims to introduce electrons through heterovalent substitution, thereby controlling carrier concentration while weakly affecting the crystal structure. Preferably, the anionic doping element is at least one of Te (tellurium), Se (selenium), and S (sulfur). Te, Se, and S are Group VIA elements with six valence electrons. When they partially substitute Sb³... - / Bi³ - When this process is repeated, additional valence electrons are introduced. Each Te / Se / S atom replacing Sb / Bi is equivalent to providing an extra free electron, making the material an n-type semiconductor, effectively increasing the electron carrier concentration, and thus significantly improving conductivity (reducing resistivity). The atomic radii of Te, Se, and S are relatively close to those of Sb and Bi, making them easy to integrate into the crystal lattice and form substitutional solid solutions without causing severe lattice distortion.

[0039] Band structure manipulation: This type of heavy element doping can also affect the band structure of the material (such as band convergence), which may increase the carrier concentration without excessively degrading the Seebeck coefficient (S), thus helping to obtain a high power factor (PF).

[0040] Cation doping (substitution of Mg sites), which involves replacing Mg with trivalent / polyvalent cations. 2+ This provides additional electrons and improves the thermal stability of the material. Preferably, the cation doping includes at least one of Group III elements (Sc, Y), lanthanides (La, Pr, Ce), or other cations (Ag, Mn). Sb and Bi are Group VA elements, each with 5 valence electrons. In the Zintl phase Mg3Sb2, Mg provides 2 electrons, and on average each Sb gains 3 electrons, achieving an octet stable structure. Mg is a +2 valence cation. When Mg is partially replaced by Group III elements (Sc, Y: +3 valence) or lanthanides (La, Pr, Ce: +3 valence), the cations improve the material's thermal stability. 2+When Mg is introduced, positive charge centers are introduced. To maintain electroneutrality, the material needs to compensate for the negative charge, which is usually achieved by generating cation vacancies or introducing interstitial atoms. This process provides free electrons, also achieving n-type doping and improving conductivity. Meanwhile, rare earth or transition metal elements such as Sc, Y, and La have higher melting points and lower vapor pressures. After replacing Mg in the crystal lattice, they act as "pinning" elements, enhancing lattice energy and raising the atomic diffusion barrier, thereby effectively suppressing the volatilization of Mg during sintering and service, ensuring the long-term stability of the material's composition and thermoelectric properties. Ag + radius and Mg 2+ Unlike other materials, Ag's substitution may introduce stronger point defect scattering, which helps reduce lattice thermal conductivity. Simultaneously, the introduction of Ag may alter the sintering behavior of the material, promoting densification. Mn, with its multiple valence states, may introduce resonant energy levels, optimizing the Seebeck coefficient; it also acts as a strong scattering center, effectively reducing thermal conductivity.

[0041] S2: Block Mg3Sb 2-x Bi x Thermoelectric raw materials undergo compression deformation at room temperature.

[0042] Specifically, Mg3Sb 2-x Bi x The base material exhibits excellent plastic deformation capabilities at room temperature. Compared to other intrinsically brittle thermoelectric materials, it can undergo plastic deformation at room temperature to introduce high-density defects. This is demonstrated by using bulk Mg3Sb. 2-x Bi x The material is cut to appropriate dimensions and subjected to compression plastic deformation using a universal testing machine. Plastic deformation generates high-density defects within the material, such as dislocations and twins. Performance studies have shown that dislocations deteriorate the thermoelectric properties of the material, while twins have a smaller impact. Furthermore, high-density twin boundaries can improve the thermoelectric and mechanical properties of the material. Moreover, controlling the internal defect density by varying the strain is beneficial for Mg3Sb. 2-x Bi x Performance improvements in thermoelectric materials.

[0043] S3: The compressed and deformed blocky Mg3Sb 2-x Bi x Annealing of thermoelectric raw materials yields Mg3Sb with synergistic improvements in thermoelectric and mechanical properties. 2-x Bi x Material.

[0044] Specifically, annealing is a heat treatment process that optimizes the properties of a material by controlling the heating and cooling process to alter its microstructure. In this application, annealing specifically refers to annealing Mg3Sb that has undergone room temperature compression plastic deformation. 2-x Bi xThe process of heating a bulk material to a specific temperature (e.g., 773 K) in a vacuum environment, holding it at that temperature for a certain time (e.g., 30 minutes), and then cooling it.

[0045] Annealing can be used to control the Mg3Sb content. 2-x Bi x The types of internal defects in thermoelectric materials are identified, and defects that contribute to thermoelectric and mechanical properties are retained to achieve synergistic regulation of thermoelectric and mechanical properties.

[0046] In some embodiments, bulk Mg3Sb 2-x Bi x The preparation method of thermoelectric materials is as follows: (1) Weigh out the corresponding mass of each element of the raw material; (2) After the weighed elemental raw materials are mixed, they are ball-milled into metal powder under a protective atmosphere; (3) The metal powder is loaded into a mold and sintered into block Mg3Sb under vacuum. 2-x Bi x Thermoelectric materials.

[0047] Specifically, Mg3Sb 2-x Bi x Thermoelectric materials are prepared by ball milling and sintering high-purity elemental Mg, Sb, Bi, and their dopants, typically with a purity of over 99.99%. First, the corresponding masses of elemental Mg, Sb, Bi, and dopants are weighed according to atomic ratios, with a weighing accuracy to ±0.001 g. The elemental raw materials are then transferred to a ball mill and ball-milled under the protection of an inert gas to ensure sufficient reaction between the elemental raw materials. The inert gas includes argon and nitrogen.

[0048] Ball milling is an important technology for powder processing and modification using mechanical force. Its core principle is to repeatedly apply impact, friction, and shearing forces to powder particles using high-speed moving grinding media (usually cemented carbide or ceramic balls) within the mill jar. Elements such as Mg, Sb, and Bi have significant differences in melting point and density, making direct melting prone to segregation. Ball milling can force them to mix uniformly in the solid state and pre-alloy them, ensuring the chemical homogeneity of the powder before sintering. Ball-milled powders have small particle sizes, numerous defects, and large specific surface areas, exhibiting extremely high surface energy and reactivity, which is beneficial for obtaining highly dense, homogeneous bulk materials after subsequent sintering.

[0049] In some implementations, Mg3Sb 2-x Bi x Thermoelectric raw materials: 0.45≤x≤1.55.

[0050] Specifically, Sb has an atomic weight of approximately 121.8, while Bi has an atomic weight of approximately 209.0, a significant difference. In the solid solution Mg3Sb... 2-x Bi x In Sb and Bi, Sb and Bi are randomly distributed in the crystal lattice, creating mass fluctuations. The different atomic radii of Sb and Bi also lead to lattice distortion and strain field fluctuations. Both of these fluctuations are strong phonon scattering centers. The closer x is to 1 (i.e., Sb:Bi ≈ 1:1), the greater the lattice disorder, the stronger the phonon scattering, and the lower the lattice thermal conductivity. Typically, the lattice thermal conductivity reaches its minimum in the x ∈ [1.0-1.55]. Alloying Sb and Bi alters the structure of the conduction band (for n-type) or valence band (for p-type). Studies show that in the x ∈ [1.0-1.55] range, multi-band convergence or effective mass optimization may occur, resulting in a higher power factor for a given carrier concentration. Although alloying significantly improves phonon scattering, it also scatters electrons, leading to a decrease in carrier mobility. When x is too large (close to 2) or too small (close to 0), the electron scattering effect may become too strong, causing a significant decrease in conductivity σ, which is counterproductive. The x ∈ [1.0-1.55] range finds the optimal compromise between "reducing lattice thermal conductivity" and "maintaining a high power factor". When the Bi content is too low (x < 0.45), the alloy scattering effect is not strong enough, the decrease in lattice thermal conductivity is not significant, and the material properties are closer to pure Mg3Sb2. Its zT value in the room temperature to medium temperature range is usually not as good as the optimized alloy. x ≤ 1.55 avoids excessive electron scattering.

[0051] In some embodiments, the ball milling time is 6-10 hours, and the particle size of the metal powder is 5-20 μm. Preferably, the ball milling time is 8 hours.

[0052] The total ball milling time was set at 6-10 hours to ensure sufficient reaction of the raw materials. Too short a time resulted in insufficient alloying, while too long a time led to excessive oxidation, agglomeration, or the introduction of excessive impurities. The final metal powder mixture had a particle size of 5-20 μm. Powders in this size range have a large specific surface area and high surface energy, making them more prone to plastic deformation and atomic diffusion during sintering, thus achieving rapid densification at lower sintering temperatures and shorter holding times. This helps obtain bulk materials with near-theoretical density, reduces scattering of charge carriers by pores, and optimizes electrical conductivity. Fine powder particles achieve more complete alloying and more uniform mixing during ball milling. Furthermore, it ensures highly uniform chemical composition at the microscale of the sintered bulk material, avoiding thermoelectric instability caused by component segregation and guaranteeing performance repeatability. A small initial powder particle size is a prerequisite for obtaining fine-grained bulk materials. During the rapid sintering process of SPS, the grains do not have time to grow, and the final material maintains a submicron grain size. This fine-grained structure strongly scatters phonons, which is a key means of significantly reducing lattice thermal conductivity (κ). At the same time, the fine-grained structure can also improve the mechanical properties of materials (such as hardness and strength) through the grain-refining strengthening mechanism.

[0053] In some embodiments, the sintering method is spark plasma sintering, and the sintering time is 2-5 minutes.

[0054] Specifically, spark plasma sintering (SPS) is an advanced rapid sintering technology in the field of powder metallurgy. Its core principle is to apply high-energy, instantaneous DC pulse current directly through the powder or a conductive mold (such as graphite) while applying uniaxial pressure. The plasma generated between powder particles by the pulse discharge and the Joule heating effect are used to achieve rapid heating, purification, and densification of the powder. In this application, the ball-milled metal powder is placed in a sintering mold, and an axial pressure of 3-8 kN is applied under a vacuum of less than 40 Pa. Preferably, the axial pressure is 5-5.5 kN.

[0055] The use of spark plasma sintering (SPS) in this application has the following advantages: The sintering temperature is low and the time is short. Conventional hot pressing sintering requires several hours, and the temperature is usually 200-300℃ lower than the material's melting point; while spark plasma sintering only takes a few minutes to tens of minutes, and the sintering temperature is 50-150℃ lower than hot pressing. (For Mg3Sb) 2-x Bi x For systems containing volatile elements (Mg), low-temperature short-time sintering can significantly reduce the volatilization of Mg, prevent the composition from deviating from the stoichiometric ratio, and thus ensure the stability of thermoelectric properties.

[0056] The grain refinement effect is significant. Due to the extremely short sintering time and limited atomic diffusion time, powder particles are difficult to grow, and the final bulk material can maintain a nanocrystalline or submicron crystalline structure. Grain refinement is one of the key means to reduce the lattice thermal conductivity of thermoelectric materials (grain boundary phonon scattering). At the same time, the nanocrystalline structure can also improve the mechanical properties of the material (such as hardness and plasticity), which is particularly beneficial for Mg3Sb. 2-x Bi x Optimizing the mechanical properties of the base material is crucial.

[0057] High density. The plasma generated by the pulsed current can remove the oxide film and adsorbed gas on the surface of the powder particles. At the same time, the axial pressure and instantaneous high temperature work together to make the green body quickly reach 98%~100% of the theoretical density, which is much higher than that of atmospheric pressure sintering and comparable to hot isostatic pressing.

[0058] It exhibits good compositional homogeneity with no significant segregation. Low-temperature, short-time sintering suppresses long-range elemental diffusion, avoiding the compositional segregation problem commonly encountered in traditional solid-state sintering; simultaneously, the cleaning effect of plasma reduces impurity introduction, making it suitable for complex multi-component systems (such as Mg3Sb). 2-x Bi x Preparation of filled cobaltite, etc.

[0059] Low energy consumption and high efficiency. Compared with hot pressing and hot isostatic pressing, SPS sintering time is shortened by more than an order of magnitude, energy consumption is significantly reduced, and the process flow is simple, making it suitable for the integration of laboratory research and industrial production.

[0060] The following reaction occurs during spark plasma sintering: Powder particle rearrangement and plastic deformation. In the initial stage of heating, powder particles rapidly rearrange under pressure, filling pores. As the temperature rises, the kinetic energy of atoms on the particle surface increases, resulting in localized plastic deformation (especially in grain boundary regions), further eliminating pores. Compared with hot pressing, the pulsed discharge of spark plasma sintering can generate instantaneous high-temperature plasma at the particle contact points, making the local temperature at the contact points much higher than the overall sintering temperature, making plastic deformation easier to occur and significantly increasing the densification rate.

[0061] Grain boundary slip and atomic diffusion. In the intermediate temperature stage, the diffusion coefficient of grain boundary atoms increases significantly, leading to grain boundary slip. Simultaneously, atoms fuse particles through a combination of grain boundary diffusion and volume diffusion. Due to the extremely short holding time in spark plasma sintering (typically 5–20 min), long-range atomic diffusion is suppressed. The final bulk material retains the fine-grained / nanocrystalline structure of high-energy ball milling, with grain sizes typically ranging from 0.5 to 2 μm, much smaller than the grain size of hot-pressed sintering (5–10 μm).

[0062] Oxide film rupture and surface cleaning. Oxide films such as MgO and Sb2O3 are easily formed on the surface of powder particles after ball milling. The instantaneous high voltage electric field generated by the pulse discharge of SPS can break down the oxide film, and at the same time, the high temperature causes the oxide film to brittlely fracture. The reducing atmosphere of the graphite mold can also help remove some of the oxide film.

[0063] The volatility of Mg deviates from the stoichiometric ratio. Mg has a lower boiling point (approximately 1107 °C), while Mg3Sb... 2-x Bi x The sintering temperature is typically 550~650 ℃, which is lower than the boiling point of Mg. However, under vacuum / inert atmosphere, Mg will still volatilize on the surface, resulting in trace amounts of Mg vacancies in the bulk. The higher the sintering temperature, the longer the holding time, and the higher the vacuum level, the more severe the Mg volatilization. Appropriately increasing the axial pressure can suppress Mg volatilization (reduce porosity and reduce the escape channels of Mg atoms).

[0064] Homogenization of the solid solution and precipitation of trace second phases. The powder after high-energy ball milling is a supersaturated solid solution (Sb and Bi atoms are randomly distributed in the crystal lattice). During spark plasma sintering, short-range atomic diffusion causes Sb and Bi atoms to be uniformly distributed, forming a stable Mg3(Sb,Bi)2 solid solution. If there is compositional segregation in the ball-milled powder, trace amounts of MgSb2 or MgBi2 second phases may precipitate in local areas. Spark plasma sintering, with its low temperature and short duration, can suppress the growth of the second phase, resulting in precipitated phases that are mostly nanoscale (<100 nm), rather than the coarse second phases found in traditional sintering.

[0065] In some embodiments, the sintering mold is a graphite mold. After ball milling, the surface of the powder particles easily forms oxide films such as MgO and Sb₂O₃. The instantaneous high-voltage electric field generated by the pulse discharge of spark plasma sintering can break down the oxide film, while the high temperature causes brittle fracture of the oxide film. In a vacuum SPS sintering furnace, the graphite mold not only serves as a pressure-bearing and heat-transferring tool, but also reacts with trace amounts of residual oxygen or possible oxides on the material surface at high temperatures, thereby creating and maintaining a strongly reducing environment. On the one hand, at high temperatures, the carbon (C) in the graphite mold is itself a strong reducing agent. It can react with any free oxygen: C + O₂ → CO₂ or 2C + O₂ → 2CO, further consuming trace amounts of oxygen. More importantly, carbon can reduce the extremely thin oxide film (e.g., Sb₂O₃, Bi₂O₃, etc.) that may have already formed on the surface of the raw materials. The reaction may generate CO or CO₂ gas, which can be removed by the vacuum system, thereby purifying the material surface and promoting metallic bonding between particles during sintering. The general reaction formula is: MO + C → M + CO.

[0066] In some implementations, in Mg3Sb 2-x Bi xThe metal powder is sintered at 0.5-0.8 times the melting point temperature of the thermoelectric raw material.

[0067] Specifically, Mg3Sb can be obtained by consulting phase diagram data. 2-x Bi x The melting point temperature of a material. A phase diagram is a graphical tool that describes the phase composition and phase equilibrium relationships of a material system under different temperature, pressure, and compositional conditions. Essentially, it's a "map" that guides our understanding of how the microstructure of a material changes with external conditions, serving as the cornerstone of material design and heat treatment. The relationship between the various components in the phase diagram and temperature is typically determined based on thermodynamic calculations combined with experiments. Therefore, Mg3Sb... 2-x Bi x Different materials have different melting points depending on their specific composition. Spark plasma sintering at 0.5-0.8 times the melting point temperature can efficiently alloy these materials while maintaining good mechanical properties. This method requires less heating temperature, making it more energy-efficient and environmentally friendly.

[0068] In some embodiments, bulk Mg3Sb 2-x Bi x The strain after compression deformation is 10%-15%.

[0069] Specifically, high-density micro-defects, including dislocations and twins, are introduced into the material through plastic deformation. Dislocations have a negative impact on thermoelectric properties. Annealing reduces the dislocation density within the material while retaining twins. The twins improve the material's mechanical properties and also enhance its thermoelectric properties to some extent. By controlling the compressive strain, the density of internal defects can be adjusted, thereby regulating the material's properties to the target range.

[0070] In some implementations, the annealing temperature is 473-773 K and the annealing time is 30-60 minutes.

[0071] Specifically, the annealing temperature is set to 473-773K and the annealing time is set to 30-60 minutes. The core objective is to effectively eliminate harmful dislocations during the "recovery" stage while strictly avoiding "recrystallization" and excessive volatilization of Mg, thereby achieving synergistic optimization of thermoelectric and mechanical properties.

[0072] The lower temperature limit (~473 K) ensures sufficient thermal activation energy to drive atomic motion, causing high-energy dislocations to annihilate and recombine, thereby effectively reducing dislocation density. The upper temperature limit (~773 K) serves as a safety boundary, designed to suppress the "recrystallization" process. Once recrystallization occurs, new, strain-free grains will form within the material. This not only eliminates all deformation-induced defects (including twins that need to be retained), but may also coarsen the grains, adversely affecting both thermal conductivity and mechanical properties.

[0073] Increasing the annealing temperature and time can improve the recovery effect. However, excessively long holding times can promote recrystallization and the precipitation of Mg. Therefore, this application sets the annealing time within a reasonable range of 30-60 minutes.

[0074] With Mg 3.2 Sb 1.5 Bi 0.49 Te 0.01 and Mg 3.2 Sb 0.49 Bi 1.5 Te 0.01 Taking the preparation of two components by sintering as an example.

[0075] Example 1 With Mg 3.2 Sb 1.5 Bi 0.49 Te 0.01 Based on 10g of material, the following elements were weighed: Mg 2.1362 g, Sb 5.0163 g, Bi 2.8125 g, and Te 0.035 g. The weighed material was placed in a ball mill jar equipped with two 10 mm balls and ball-milled for 8 hours under an inert atmosphere to obtain a metal powder mixture. The above-mentioned metal powder mixture was loaded into a graphite mold and subjected to spark plasma sintering in a vacuum environment. The vacuum degree was 40 Pa, the axial pressure was set to 5 kN, the sintering temperature was 1123 K, and the sintering time was 5 min; thus, bulk Mg was prepared. 3.2 Sb 1.5 Bi 0.49 Te 0.01 Material.

[0076] Example 2 The difference between this embodiment and Embodiment 1 is that the sintering temperature is 1083K and the sintering time is 2min.

[0077] Example 3 With Mg 3.2 Sb 0.49 Bi1.5 Te 0.01 Based on 10g of material, weigh out 1.72g of Sb, 1.3194g of Bi, 6.9323g of Te, and 0.0282g of Te. The weighed material was placed in a ball mill jar equipped with two 10 mm balls and ball-milled for 8 hours under an inert atmosphere to obtain a metal powder mixture. The above-mentioned metal powder mixture was loaded into a graphite mold and subjected to spark plasma sintering in a vacuum environment. The vacuum degree was 40 Pa, the axial pressure was set to 5 kN, the sintering temperature was 1053 K, and the sintering time was 5 min; thus, bulk Mg was prepared. 3.2 Sb 0.49 Bi 1.5 Te 0.01 Material.

[0078] Example 4 The difference between this embodiment and Embodiment 3 is that the sintering temperature is 1023K and the sintering time is 2min.

[0079] The blocky Mg prepared in Examples 1-4 3.2 Sb 1.5 Bi 0.49 Te 0.01 Materials and bulk Mg 3.2 Sb 0.49 Bi 1.5 Te 0.01 Intrinsic property testing of materials, such as Figure 1 As shown.

[0080] in, Figure 1 (a) shows the relationship between the resistivity of the material and temperature, measuring the material's ability to impede the passage of electric current. It is inversely related to the conductivity. The lower the value (the higher the curve in the figure), the better the conductivity. The resistivity of all sample examples increased significantly with increasing temperature.

[0081] Figure 1 (b) shows the Seebeck coefficient (S) as a function of temperature. The Seebeck coefficient (S), also known as thermoelectric potential, reflects the ability of a material to generate voltage under temperature difference. The negative sign indicates that the material is an n-type semiconductor (electrons are the majority carriers). The larger the absolute value, the greater the thermoelectric conversion potential. The absolute value generally increases with increasing temperature, but may saturate or slightly decrease in the high-temperature range (>700K).

[0082] Figure 1(c) The relationship between power factor (PF) and temperature. Power factor (PF) is a core indicator for comprehensively evaluating the electrical output performance of materials. The higher the value, the greater the electrical power generated per unit temperature difference. All curves exhibit a "hump" shape, rising rapidly at the peak and then slowly declining. The temperature corresponding to the peak PF is the operating point where the material's electrical performance is optimal.

[0083] Figure 1 (d) shows the relationship between thermal conductivity (κ) and temperature, which measures a material's ability to conduct heat. For thermoelectric materials, it is desirable for this value to be as low as possible to maintain the temperature difference across the device. All samples generally show a slow decreasing trend with increasing temperature. Mg 3.2 Sb 0.49 Bi 1.5 Te 0.01 The component sample showed a slow rise after about 500K, but this did not affect the overall performance requirements.

[0084] Figure 1 (e) shows the relationship between the thermoelectric figure of merit (zT) and temperature. The thermoelectric figure of merit is the ultimate comprehensive index for measuring the energy conversion efficiency of thermoelectric materials. The higher the zT value, the better the thermoelectric performance. Similar to the power factor PF, it shows a trend of first increasing and then decreasing, reaching a peak value (peak zT) at a certain temperature. The peak value is the optimal operating temperature range of the material.

[0085] from Figure 1 It can be seen that different material compositions and heat treatment processes have a certain impact on the material properties. The thermoelectric properties of all material samples meet the application requirements of medium- and low-temperature thermoelectric materials. Mg 3.2 Sb 1.5 Bi 0.49 Te 0.01 The optimal composition of zT occurs at high temperatures, exhibiting a wide high-performance temperature range, making it suitable for high-temperature operation. It can effectively convert thermal energy into electrical energy, demonstrating potential as a thermoelectric power generation material. Mg 3.2 Sb 0.49 Bi 1.5 Te 0.01 The optimal zT is concentrated in the medium-low temperature range, especially suitable for efficient conversion of electrical and thermal energy in near-room temperature scenarios, demonstrating good application prospects as a thermoelectric refrigeration material. The total thermal conductivity of the samples decreases with increasing temperature and remains at a low value. The most important indicator—the dimensionless thermoelectric figure of merit—is greater than 0.5 throughout the entire test temperature range, and the peak zT value of the optimal sample exceeds 1.4, appearing at a temperature of approximately 675 K. This performance indicator has reached or is close to the level of commercial thermoelectric materials (such as Bi2Te3-based materials), fully demonstrating the great potential of this material system in medium-low temperature applications such as waste heat recovery. Mg3Sb prepared by the above process2- x Bi x The base material's thermoelectric properties (especially peak zT and optimal operating temperature) fully meet the core requirements of medium and low temperature thermoelectric applications, demonstrating excellent industrialization prospects.

[0086] Furthermore, the blocky Mg prepared in Examples 1 and 4... 3.2 Sb 1.5 Bi 0.49 Te 0.01 Materials and bulk Mg 3.2 Sb 0.49 Bi 1.5 Te 0.01 The material undergoes room temperature compression deformation and annealing treatment, with the specific process as follows: Through 0.0001 s -1 The strain was measured by compressing the material samples. The compression rate was calculated as sample length * 60 / 10000; this yielded corresponding strain values ​​of 5%, 10%, and 15% for blocky Mg. 3.2 Sb 1.5 Bi 0.49 Te 0.01 Materials and bulk Mg 3.2 Sb 0.49 Bi 1.5 Te 0.01 Material.

[0087] like Figure 2 As shown, it is blocky Mg 3.2 Sb 1.5 Bi 0.49 Te 0.01 Materials and Mg 3.2 Sb 0.49 Bi 1.5 Te 0.01 The stress-strain curve of the material illustrates the stress-strain relationship at 0.0001 s. -1 At the strain rate, the strain does not change abruptly below 40%, indicating that room temperature compression deformation is safe and effective.

[0088] All compressed samples were annealed at 773 K for 30 min.

[0089] like Figure 3 As shown, Mg under different compressive strains 3.2 Sb 1.5 Bi 0.49 Te 0.01 Performance changes. Among them... Figure 3(a) shows the resistivity (ρ) versus temperature. For all samples (at different strains), the resistivity initially decreases rapidly with increasing temperature, then levels off or slightly increases. In most temperature ranges, the resistivity of strained samples (especially those with 5% and 10%) is higher than that of unstrained samples (ε=0%). This increase in resistivity is a typical characteristic of semiconductors, stemming from the increase in carrier concentration with increasing temperature. The fact that strain can increase resistivity indicates that defects introduced by plastic deformation (such as dislocations and lattice distortions) reduce carrier transport within this range. Figure 15 , Figure 16 As shown, where Figure 15 (a) and Figure 16 (a) The carrier concentration n is set for the material under different strains. H The curve showing the relationship between temperature T and temperature. Figure 15 (b) and Figure 16 (b) is the Hall mobility of the material under different strain variables. The curve showing the relationship between temperature T and temperature. Figure 15 and Figure 16 It can be seen that Mg 3.2 Sb 1.5 Bi 0.49 Te 0.01 and Mg 3.2 Sb 0.49 Bi 1.5 Te 0.01 After room temperature plastic deformation, the carrier concentration decreased to some extent in all materials, especially below 450 K, where the decrease was significant. Hall mobility also decreased to some extent below 450 K, thus negatively impacting the thermoelectric figure of merit. However, with increasing temperature, especially above 600 K, some plastically deformed materials showed a slight increase in both carrier concentration and Hall mobility, thereby improving the thermoelectric figure of merit. Therefore, annealing at 773 K can have a positive impact on the overall electrical properties of the material. Figure 3 (b) shows the Seebeck coefficient (S) as a function of temperature. The |S| values ​​of the unstrained samples all increase monotonically with increasing temperature, while the |S| values ​​of the strained samples all decrease first and then increase with temperature. The effect of strain on the S value is relatively complex, but overall, moderate strain (e.g., 5%, 10%) does not significantly damage the S value; in some temperatures, it is even comparable to or slightly better than the unstrained sample. The increase in S value with increasing temperature is related to the increase in the effective mass of charge carriers or the multi-band effect. The key point is that strain does not lead to a significant decrease in the S value, indicating that while increasing resistivity (reducing conductivity), the core ability of the material to generate thermal voltage is maintained, laying the foundation for obtaining a high power factor. Figure 3(c) shows the variation of the power factor (PF) with temperature. The PF of all samples exhibits a "hump" shape, initially increasing and then decreasing, peaking around 600 K. Samples subjected to 5% or 10% strain show significantly lower peak PF values ​​than unstrained (ε=0%) samples. The decrease in PF of strained samples is directly related to their higher resistivity (lower conductivity), although their Seebeck coefficient increases somewhat. This demonstrates that room-temperature plastic deformation reduces the electrical transport properties of the material. Figure 3 (d) shows the variation of thermal conductivity (κ) with temperature. The effect of strain on thermal conductivity is not as significant as on electrical parameters, but the thermal conductivity of strained samples generally shows a slight decreasing trend. Defects introduced by strain (such as dislocations and grain boundaries) can act as additional phonon scattering centers, which helps to further reduce lattice thermal conductivity, which is beneficial for improving the zT value.

[0090] Figure 4 Mg under different compressive strains 3.2 Sb 0.49 Bi 1.5 Te 0.01 Performance changes. The trend of these changes is similar to... Figure 3 Mg 3.2 Sb 1.5 Bi 0.49 Te 0.01 The performance change trends are basically the same.

[0091] from Figure 3 , Figure 4 It can be seen that for Mg3Sb 2-x Bi x Applying 5%–15% room-temperature plastic deformation (strain) to the base material reduces its thermoelectric properties. Specifically, compared to undeformed samples, strained samples (especially those with 10% strain) increase the Seebeck coefficient but significantly increase resistivity, leading to a decrease in the power factor (PF). Furthermore, defects introduced by plastic deformation contribute to phonon scattering, resulting in an overall decrease in the material's thermal conductivity. Ultimately, this significant reduction in electrical transport properties leads to a decrease in the thermoelectric figure of merit (zT).

[0092] like Figure 5 As shown, Mg under different compressive strains 3.2 Sb 1.5 Bi 0.49 Te 0.01 Internal twinning changes. Figure 6 Mg under different compressive strains 3.2 Sb 1.5 Bi 0.49 Te 0.01 Changes in internal dislocations. Figure 7 Mg under different compressive strains3.2 Sb 0.49 Bi 1.5 Te 0.01 Internal twinning changes. Figure 8 Mg under different compressive strains 3.2 Sb 0.49 Bi 1.5 Te 0.01 Internal dislocation changes. It can be seen that as the strain increases, Mg... 3.2 Sb 1.5 Bi 0.49 Te 0.01 Materials and Mg 3.2 Sb 0.49 Bi 1.5 Te 0.01 Both twins and dislocations are increasing within the material. Twins are represented in the figure as a straight line, or a curved, disordered network or cluster within the same grain. Dislocations... Figure 6 and Figure 8 The color in the middle is green.

[0093] Figure 9 Mg after annealing 3.2 Sb 1.5 Bi 0.49 Te 0.01 The changes in thermoelectric properties show that after annealing, Mg... 3.2 Sb 1.5 Bi 0.49 Te 0.01 The thermoelectric properties returned to their initial state (ɛ=0%).

[0094] Figure 10 Mg after annealing 3.2 Sb 0.49 Bi 1.5 Te 0.01 The changes in thermoelectric properties show that after annealing, Mg... 3.2 Sb 0.49 Bi 1.5 Te 0.01 The thermoelectric properties are higher than in the initial state (ɛ=0%).

[0095] Therefore, from Figure 9 and Figure 10 It can be seen that annealing after applying 5-15% strain improves the overall thermoelectric performance to a certain extent.

[0096] Figure 11 Mg after annealing 3.2 Sb 1.5 Bi 0.49 Te 0.01The changes in internal twins and dislocations can be seen in Mg 3.2 Sb 1.5 Bi 0.49 Te 0.01 The internal twins remain largely unchanged (lateral comparison of the two columns on the left), while the dislocation density decreases (lateral comparison of the two columns on the right, the green color becomes lighter). Twins are planar defects that have a relatively small impact on thermoelectric properties, but their interfaces effectively hinder dislocation movement, thereby improving the material's mechanical properties (such as strength and hardness). Retaining twins is key to enhancing mechanical properties. Dislocations are line defects that strongly scatter charge carriers (electrons), severely degrading the material's electrical conductivity and harming thermoelectric properties. Through low-temperature annealing, atoms gain energy migration, causing these high-energy, unstable dislocations to annihilate or recombine, thus effectively reducing the dislocation density.

[0097] Figure 12 Mg after annealing 3.2 Sb 0.49 Bi 1.5 Te 0.01 The changes in internal twins and dislocations show that, compared to Mg 3.2 Sb 1.5 Bi 0.49 Te 0.01 The internal twins and dislocations exhibit the same pattern of change: the twins remain essentially unchanged (lateral comparison of the two columns on the left), while the dislocation density decreases (lateral comparison of the two columns on the right, the green color becomes lighter). Therefore, through a precisely controlled low-temperature annealing process, the "decoupling" regulation of the two defects introduced by deformation was successfully achieved—that is, selectively eliminating harmful dislocations while retaining beneficial twins. This provides the most direct microstructural evidence for ultimately achieving synergistic optimization of thermoelectric and mechanical properties.

[0098] Figure 13 For strain and after annealing, Mg 3.2 Sb 1.5 Bi 0.49 Te 0.01 and Mg 3.2 Sb 0.49 Bi 1.5 Te 0.01 Changes in yield strength between the two components. From Figure 13 It can be seen that, when comparing the inflection points of the same color curves, the yield strength of both components is increased.

[0099] Figure 14 For strain and after annealing, Mg 3.2 Sb 1.5 Bi 0.49 Te 0.01 and Mg 3.2 Sb 0.49 Bi 1.5 Te 0.01The hardness change of the two components. From Figure 13 It can be seen that the hardness of both components is increased.

[0100] Therefore, it can be confirmed that the Mg3Sb obtained through this application... 2-x Bi x Mg3Sb prepared by a method of synergistic regulation of thermoelectric and mechanical properties 2-x Bi x The thermoelectric and mechanical properties are better coordinated. Although some components of the material do not show significant improvement in thermoelectric properties, their mechanical properties are significantly improved, resulting in a significant improvement in overall performance.

[0101] This invention is based on Mg3Sb 2-x Bi x The unique room-temperature plastic deformation capability of the base material, compared to other intrinsically brittle thermoelectric materials, allows for the introduction of high-density micro-defects (such as dislocations and twins) through plastic deformation at room temperature. Combined with subsequent low-temperature annealing, this enables precise control over defect types—selectively eliminating dislocations detrimental to thermoelectric performance while retaining twins that enhance thermoelectric and mechanical properties, thus achieving synergistic optimization of thermoelectric and mechanical properties. This process offers the following significant advantages: Simplified process and low equipment requirements: Since plastic deformation can be achieved without high temperatures, the stringent requirements for deformation equipment are reduced, making the process faster and simpler. Reduced energy consumption and stable composition: By avoiding high-temperature treatment, energy consumption during preparation is significantly reduced, and the loss of volatile elements such as Mg is effectively suppressed, ensuring the accuracy of material composition and the stability of performance.

[0102] Synergistic performance enhancement: After annealing, the twins in the material are retained, while the dislocation density is significantly reduced; for example, the yield strength and hardness of the sample treated by "strain + annealing" are significantly improved, realizing the synchronous regulation or enhancement of thermoelectric and mechanical properties.

[0103] On the other hand, this application also provides a Mg3Sb 2-x Bi x The material, based on the above Mg3Sb 2-x Bi x A method for synergistic regulation of the thermoelectric and mechanical properties of materials was obtained. After annealing, twins in the material were retained, while the dislocation density decreased significantly. For example, samples treated with "strain + annealing" showed significant improvements in yield strength and hardness, achieving simultaneous enhancement of thermoelectric and mechanical properties.

[0104] The above-disclosed embodiments are merely preferred embodiments of this application and should not be construed as limiting the scope of this application. Therefore, any equivalent variations made in accordance with the claims of this application shall still fall within the scope of this application.

Claims

1. A Mg3Sb 2-x Bi x A method for synergistic regulation of thermoelectric and mechanical properties of materials based on room temperature deformation technology, characterized in that: include: Provide bulk Mg3Sb 2-x Bi x thermoelectric raw materials, where 0 < x < 2; the Mg3Sb 2-x Bi x thermoelectric raw materials include anion doping elements and / or cationic element doping; The blocky Mg3Sb 2-x Bi x Thermoelectric raw materials undergo compression deformation at room temperature; The compressed and deformed blocky Mg3Sb 2-x Bi x Annealing of thermoelectric raw materials yields Mg3Sb with synergistic improvements in thermoelectric and mechanical properties. 2-x Bi x Material.

2. The Mg3Sb as described in claim 1 2-x Bi x A method for synergistic regulation of thermoelectric and mechanical properties of materials based on room temperature deformation technology, characterized by: The anion doping element is at least one of Te, Se, and S; The cation doping element is at least one of Sc, Y, La, Pr, Ce, Ag, and Mn.

3. The Mg3Sb as described in claim 1 2-x Bi x A method for synergistic regulation of the thermoelectric and mechanical properties of materials, characterized in that, The blocky Mg3Sb 2-x Bi x The preparation method of thermoelectric raw materials is as follows: Weigh out the corresponding mass of the single-element raw material for each element; The weighed elemental raw materials are mixed and then ball-milled into metal powder under a protective atmosphere; The metal powder was loaded into a mold and sintered into block Mg3Sb under vacuum. 2-x Bi x Raw materials for thermoelectric power.

4. The Mg3Sb as described in claim 3 2-x Bi x A method for synergistic regulation of thermoelectric and mechanical properties of materials based on room temperature deformation technology, characterized in that: In bulk Mg3Sb 2-x Bi x The metal powder is sintered at 0.5-0.8 times the melting point temperature of the thermoelectric raw material.

5. The Mg3Sb as described in claim 4 2-x Bi x A method for synergistic regulation of thermoelectric and mechanical properties of materials based on room temperature deformation technology, characterized in that: The sintering method is spark plasma sintering, and the sintering time is 2-5 minutes.

6. The Mg3Sb as described in claim 3 2-x Bi x A method for synergistic regulation of thermoelectric and mechanical properties of materials based on room temperature deformation technology, characterized in that: The ball milling time is 6-10 hours, and the particle size of the metal powder is 5-20 μm.

7. The Mg3Sb as described in claim 1 2-x Bi x A method for synergistic regulation of thermoelectric and mechanical properties of materials based on room temperature deformation technology, characterized in that: 0.45≤x≤1.55。 8. The Mg3Sb as described in claim 1 2-x Bi x A method for synergistic regulation of thermoelectric and mechanical properties of materials based on room temperature deformation technology, characterized in that: blocky Mg3Sb 2-x Bi x The strain of thermoelectric raw materials after compression deformation is 10%-15%.

9. The Mg3Sb as described in claim 1 2-x Bi x A method for synergistic regulation of thermoelectric and mechanical properties of materials based on room temperature deformation technology, characterized in that: The annealing temperature is 473-773K, and the annealing time is 30-120 minutes.

10. A Mg3Sb 2-x Bi x The material is Mg3Sb as described in any one of claims 1-9 2-x Bi x The material was prepared using a method that synergistically regulates the thermoelectric and mechanical properties based on room temperature deformation technology.

Images