A post-processing method for bulk thermoelectric materials

Abstract

This invention discloses a post-processing method for bulk thermoelectric materials. The bulk thermoelectric material is embedded within a hollow plastic ring and then heated and pressed as a whole to obtain the post-processed bulk thermoelectric material. This invention, by applying a plastic constraint condition perpendicular to the axial direction to the bulk thermoelectric material and then performing axial hot compression, can further improve the density of the bulk material, refine the grains, form a large number of multi-scale defects in situ, optimize the carrier concentration, and significantly reduce the lattice thermal conductivity of the material. This provides a completely new approach for the microstructure control and performance optimization of bulk thermoelectric materials. Furthermore, the post-processing method involved is simple, easy to operate, and has low requirements for reaction equipment; the process is controllable and practical, making it suitable for widespread application.

Description

Technical Field

[0001] This invention belongs to the field of thermoelectric material preparation technology, specifically relating to a post-processing method for bulk thermoelectric materials. Background Technology

[0002] Thermoelectric conversion technology, with its excellent characteristics of being all-solid-state, without transmission devices, and noiseless, has broad prospects in both power generation and refrigeration. In today's world where fossil fuels are increasingly depleted, it perfectly aligns with the current efforts to improve heat conversion efficiency and waste heat utilization. Thermoelectric conversion efficiency is determined by the dimensionless thermoelectric figure of merit of the material, ZT = (S... 2 σ / κ e +κ L )T (where S is the Seebeck coefficient, σ is the conductivity, κ is the conductivity) e and κ L ZT is determined by electronic thermal conductivity and lattice thermal conductivity (T is absolute temperature). At a given temperature, the higher the ZT value, the higher the thermoelectric conversion efficiency of the material. Typically, the Seebeck coefficient, electrical conductivity, and electronic thermal conductivity of a material can only be synergistically controlled, while lattice thermal conductivity can be decoupled and optimized by controlling the microstructure.

[0003] Doping and solid solution atoms causing matrix point defects and dislocations, as well as the in-situ or ex-situ introduction of nanoscale second phases, have been widely used to optimize the lattice thermal conductivity of thermoelectric materials. Furthermore, some new structures designed to impede phonon transport have been proposed for application in bulk thermoelectric materials, such as van der Waals gaps, the introduction of solid particles to form core-shell structures to suppress phonon transport, and the increase in the average size of the second phase. High-energy ball milling, self-propagating high-temperature reaction combined with spark plasma sintering, and other processes can also be used to obtain refined grains, and can in-situ form defects and nanostructures that scatter phonons.

[0004] However, the defects and nanostructures formed by the above methods mostly require the introduction of non-matrix elements. In particular, the introduced nano-second phase undergoes Ostwald ripening during subsequent service, leading to the failure of the thermoelectric material. Therefore, exploring a process that can control the microstructure and defects of bulk thermoelectric materials in situ is extremely crucial and can provide a new approach for optimizing the performance of bulk thermoelectric materials. Summary of the Invention

[0005] The main objective of this invention is to provide a post-processing method for bulk thermoelectric materials. The bulk materials obtained by this method have high density, can effectively refine grains, form a large number of multi-scale defects in situ, optimize carrier concentration, and greatly reduce the lattice thermal conductivity of the material. This provides a completely new approach for the microstructure control and performance optimization of bulk thermoelectric materials.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A post-processing method for bulk thermoelectric materials includes the following steps:

[0008] 1) The bulk thermoelectric material is embedded in a hollow plastic ring to obtain the sample to be pressed;

[0009] 2) Heat and maintain the temperature of the obtained sample to be pressed as a whole;

[0010] 3) Apply pressure to the heated sample obtained in step 2) and press it to obtain the post-processed bulk thermoelectric material.

[0011] In the above scheme, the hollow structure of the plastic ring is matched with the shape and specifications of the bulk thermoelectric material; during the process of heating and pressing the plastic ring containing the bulk thermoelectric material, a plastic constraint condition perpendicular to the axial direction (i.e., "radial") can be formed on the bulk thermoelectric material.

[0012] In the above scheme, the bulk thermoelectric material has a regular shape.

[0013] Preferably, the shape of the bulk thermoelectric material can be a cylinder or a cuboid, etc.

[0014] In the above scheme, the density of the bulk thermoelectric material in step 1) is 80% or more; preferably 90% or more.

[0015] In the above scheme, the bulk thermoelectric material can be selected from Bi2Te3-based compounds, MCdInSe3 (M=Cu,Ag)-based compounds, SnQ (Q=S,Se,Te)-based compounds, CoSb3-based compounds, half-Heusler alloys, Cu2Q (Q=S,Se,Te)-based compounds, Ag2Q (Q=S,Se,Te)-based compounds, InSe-based compounds, MgAgSb-based compounds, or Mg3Sb2-based compounds, etc.

[0016] In the above scheme, the bulk thermoelectric material can be densified by methods such as cold pressing, hot pressing, plasma-activated sintering, suspension melting, or high-temperature melt annealing.

[0017] In the above scheme, the plastic ring sleeve can be made of metal or the like, which can maintain good plasticity during the heating process; specifically, it can be made of aluminum, aluminum alloy or magnesium alloy, etc.

[0018] In the above scheme, the bulk thermoelectric material and the hollow plastic ring are bonded together using BN spray or high-temperature resistant inorganic adhesive.

[0019] In the above scheme, the heating temperature is 50-600℃ and the holding time is 30-60min.

[0020] In the above scheme, the pressing rate is 0.01 to 10 mm / s.

[0021] Furthermore, the pressing step can employ methods such as slow pressurization or rapid stamping; wherein the pressing rate for slow pressurization is preferably 0.01 to 0.1 mm / s; and the stamping rate for rapid stamping is preferably 1 to 10 mm / s.

[0022] In the above scheme, the applied pressure is 30 to 1000 MPa; the pressure direction is along the axial direction of the bulk thermoelectric material.

[0023] In the above scheme, in the step 3) of applying pressure, the compression ratio (reduction rate) of the bulk thermoelectric material along the pressure direction is 5% or more; preferably 10 to 60%.

[0024] Based on the above scheme, bulk thermoelectric materials (post-processed bulk thermoelectric materials) are prepared. While ensuring their overall structure, their density is further improved, the grains are significantly refined, and a large number of multi-scale defects can be formed in situ.

[0025] Based on the above content, without departing from the basic technical concept of the present invention, various modifications, substitutions or changes can be made to the content in various forms according to common technical knowledge and means in the field.

[0026] The principle of this invention is as follows:

[0027] This invention applies plastic constraints to bulk thermoelectric materials (especially denser bulk thermoelectric materials) in a direction perpendicular to the axial compression direction (i.e., "radial"), and then performs axial thermal compression on them. On the one hand, under the action of three-dimensional (xyz) stress, it is beneficial for grains to fracture and pin together, thereby achieving grain refinement and avoiding direct cracking of the sample during free thermal compression. On the other hand, during the compression process, stress concentration occurs locally in the sample, resulting in the in-situ formation of a large number of multi-scale defects (such as dislocations, nano-depositions, etc.). This is beneficial for the microstructure control and performance optimization of bulk thermoelectric materials.

[0028] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0029] 1) This invention discloses for the first time a post-processing method for bulk thermoelectric materials, resulting in bulk products with high density and refined grains, which can form a large number of multi-scale defects in situ and optimize carrier concentration;

[0030] 2) The post-processing method described in this invention can simultaneously and significantly reduce the lattice thermal conductivity of the material, providing a completely new approach for the microstructure control and performance optimization of bulk thermoelectric materials;

[0031] 3) The post-processing method involved in this invention is simple and easy to operate, has low requirements for reaction equipment, is applicable to a wide range of material systems, and is suitable for widespread application. Attached Figure Description

[0032] Figure 1 The image shows the optical morphology of the product obtained in Example 1.

[0033] Figure 2 The XRD patterns of the products (A1, B1, C1, D1) obtained in Example 1 are shown below.

[0034] Figure 3 Electron probe microanalyses and corresponding elemental plane distribution diagrams of the polished surfaces of products A1 and D1 obtained in Example 1;

[0035] Figure 4 These are scanning electron microscope images of fresh cross-sections of products A1 and D1 obtained in Example 1;

[0036] Figure 5 The image shows a transmission electron microscope (TEM) image of product C1 obtained in Example 1 and the corresponding selected area electron diffraction (SED) pattern.

[0037] Figure 6 This is a high-resolution transmission electron microscope image of product C1 obtained in Example 1;

[0038] Figure 7 This is a high-angle annular dark field image of product C1 obtained in Example 1;

[0039] Figure 8 The thermoelectric performance test results are for the products (A1, B1, C1, D1) obtained in Example 1;

[0040] Figure 9 The XRD patterns of the products (A2, B2, C2, D2) obtained in Example 2 are shown below.

[0041] Figure 10 Electron probe microanalyses and corresponding elemental plane distribution diagrams of the polished surfaces of products A2 and D2 obtained in Example 2;

[0042] Figure 11 The image shows a fresh cross-sectional scanning electron microscope image of the products (A2, B2, C2, D2) obtained in Example 2.

[0043] Figure 12 The thermoelectric performance test results are for the products (A2, B2, C2, D2) obtained in Example 2;

[0044] Figure 13 This is a scanning electron microscope image of a fresh cross-section of product B3 obtained in Example 3;

[0045] Figure 14 This is a transmission electron microscope image of product B3 obtained in Example 3;

[0046] Figure 15 This is an optical morphology image of product B4 obtained in Example 4;

[0047] Figure 16 The thermal conductivity of products A4 and B4 obtained in Example 4 varies with temperature. Detailed Implementation

[0048] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0049] In the following embodiments, the bulk thermoelectric materials MCdInSe3 (M=Cu,Ag)-based compounds, SnQ (Q=S,Se,Te)-based compounds, CoSb3-based compounds, half-Heusler alloys, Cu2Q (Q=S,Se,Te)-based compounds, Ag2Q (Q=S,Se,Te)-based compounds, and MgAgSb-based compounds were all artificially synthesized in the laboratory using conventional methods in the art; the bulk Bi2Te3-based compounds were prepared by commercial zone melting or artificially synthesized in the laboratory.

[0050] Example 1

[0051] A post-processing method for bulk thermoelectric materials, using cylindrical In 0.01 Cd 0.02 Sn 0.97 For Te samples, the specific steps are as follows:

[0052] 1) The dimensions are Φ13×20mm 3 cylindrical block In 0.01 Cd 0.02 Sn 0.97 Te samples (prepared using self-propagating high-temperature synthesis technology combined with plasma-activated sintering process, with a density of 97%) were placed in containers with dimensions of (Φ60–Φ13) × 20 mm. 3 The aluminum ring sleeve (a hollow cylindrical ring sleeve with an outer diameter of 60mm and an inner diameter of 13mm) was used, and the cylindrical block was bonded to the aluminum ring sleeve as a whole using BN spray, and was numbered A1, B1, C1 and D1 respectively.

[0053] 2) Place the sample to be pressed obtained in step 1) into the same muffle furnace, raise the temperature from room temperature to 450°C at a heating rate of 10°C / min, and hold for 30 min;

[0054] 3) The sample obtained after the heat treatment in step 2) is quickly removed from the muffle furnace and placed on the press base. Products A1, B1, C1, and D1 are obtained by rapid stamping at an axial pressure of 425 MPa and a stamping speed of 3 mm / s. Among them, the compression ratio of group A1 is 0%; the compression ratio of group B1 is 15%; the compression ratio of group C1 is 35%; and the compression ratio of group D1 is 55% (without the above-mentioned aluminum ring mold constraint, the block will be directly crushed; the following examples all have corresponding problems, which will not be repeated).

[0055] The products B1, C1, and D1 obtained in step 3) of this embodiment were subjected to wire cutting and subsequent macroscopic morphology optical imaging, as shown below. Figure 1 As shown, the obtained products B1, C1, and D1 have no obvious cracks on their surfaces, while the cut samples exhibit a "drum" shape, being smaller at both ends and larger in the middle. Density testing using the Archimedes method revealed that the products all had a density greater than 97%, indicating that this process can obtain high-density bulk materials.

[0056] Figure 2 The XRD analysis results of the product obtained in this embodiment show that the main phases A1, B1, C1, and D1 of the product are consistent, indicating that the post-processing method described in this invention does not change the phase of the sample.

[0057] Figure 3 The images shown are EPMA (electron probe microanalysis) images of the polished surfaces of products A1 and D1 obtained in this embodiment, along with their corresponding elemental distribution maps. It can be seen that the sample with a compression ratio of 55% has significantly fewer pores and a denser surface.

[0058] Figure 4 The FESEM (Field Emission Scanning Electron Microscopy) images of the fresh cross-sections of products A1 and D1 show that the sample with a compression ratio of 55% has significantly finer grains than the sample with a compression ratio of 0%.

[0059] Figure 5 The TEM (transmission electron microscope) image of product C1 and the corresponding SAED (selected area electron diffraction) image show that a large number of uniformly oriented moiré fringes are evenly distributed in the observed micro-region. In the electron diffraction along the [3-43] zone axis, in addition to the strong diffraction points of the matrix, we can also see the appearance of additional weak diffraction points, indicating that a uniformly distributed superstructure-like defect has been formed in the matrix. Figure 6 The HRTEM (high-resolution transmission electron microscopy) image of product C1 shows that there are distinct nano-precipitation regions in the matrix phase. Figure 7 The HAADF (High Angle Ring Dark Field Image) image of product C1 allows observation of the generation of multi-scale defects such as dislocations; this demonstrates that this process can generate a large number of multi-scale defects such as dislocations and superstructure defects in situ.

[0060] Figure 8 The figure shows the thermoelectric performance data of the bulk thermoelectric materials (A1, B1, C1, D1) obtained in this embodiment. As can be seen from the figure, the grain refinement and the in-situ formation of a large number of multi-scale defects such as dislocations, superstructure defects and nanoprecipitates optimize the electrical transport performance, effectively scatter phonons, effectively reduce the lattice thermal conductivity, and improve the quality factor B value of the bulk thermoelectric material.

[0061] Example 2

[0062] A post-processing method for bulk thermoelectric materials, using cylindrical bulk SnTe samples, includes the following specific steps:

[0063] 1) Take 4 pieces with dimensions of Φ13×25mm 3 Bulk SnTe samples (prepared using self-propagating high-temperature synthesis technology combined with plasma-activated sintering process, with a density of 97%) were placed in containers with dimensions of (Φ60–Φ13) × 25 mm. 3 In the aluminum ring sleeve, the cylindrical block and the aluminum ring sleeve are bonded together by BN spray and are respectively numbered A2, B2, C2 and D2;

[0064] 2) Place the sample obtained in step 1) into the same muffle furnace and heat it from room temperature to 450°C at a heating rate of 10°C / min, and hold it at that temperature for 30 min;

[0065] 3) The sample obtained after the heat treatment in step 2) is quickly removed from the muffle furnace and placed on the press base. Products A2, B2, C2, and D2 are obtained by rapid stamping at an axial pressure of 400 MPa and a stamping speed of 3 mm / s. Among them, the compression ratio of group A2 is 0%; the compression ratio of group B2 is 15%; the compression ratio of group C2 is 35%; and the compression ratio of group D2 is 55%.

[0066] The products obtained in step 3) of this embodiment were subjected to phase analysis (XRD analysis), such as... Figure 9 As shown, all samples were cubic SnTe phase, indicating that this method does not change the phase of the samples. Density testing of the products using the Archimedes method revealed that their density was all above 98%, indicating that this method can obtain high-density bulk materials.

[0067] Figure 10 The EPMA (electron probe microanalysis) images and corresponding elemental distribution maps of the polished surfaces of products A2 and D2 show that the pores in the sample with a compression ratio of 55% are significantly reduced and the surface is more compact.

[0068] Figure 11The FESEM (Field Emission Scanning Electron Microscopy) images of the fresh cross-sections of products A2, B2, C2, and D2 show that the grains of the samples become significantly finer as the compression ratio increases.

[0069] Figure 12 The figure shows the thermoelectric performance data of the bulk thermoelectric materials (A2, B2, C2, D2) obtained in this embodiment. As can be seen from the figure, this method effectively scatters phonons, effectively reduces the lattice thermal conductivity, and improves the quality factor of the bulk thermoelectric materials while optimizing the electrical transport performance.

[0070] Example 3

[0071] A post-processing method for bulk thermoelectric materials, using a rectangular bulk Bi2Te3-based sample, includes the following steps:

[0072] 1) Take two pieces with dimensions of 15×15×5mm (length×width×height). 3 Bulk Bi2Te3-based samples (p-type bismuth telluride zone melt rods with a density of 95%) were placed in containers with dimensions of (Φ70–15×15)×5mm. 3 Aluminum ring sleeve (outer diameter 70mm, central hole 15×15×5mm) 3 In the hollow rectangular ring, BN spray is used to bond the cylindrical block to the aluminum ring as a whole, and they are numbered A3 and B3 respectively.

[0073] 2) Place the sample to be pressed obtained in step 1) into the same muffle furnace, raise the temperature from room temperature to 440℃ at a heating rate of 10℃ / min, and hold for 30min;

[0074] 3) The sample obtained by the heat treatment in step 2) is quickly taken out of the muffle furnace and placed on the press base. Products A3 and B3 are obtained by rapid stamping with an axial pressure of 400 MPa and a stamping speed of 3.5 mm / s. The compression ratio of group A3 is 10% and the compression ratio of group B3 is 30%.

[0075] The fresh cross-section of product B3 obtained in step 3) of this embodiment was characterized by FESEM (Field Emission Scanning Electron Microscopy), such as... Figure 13 As shown, the sample grains become significantly finer with increasing compression ratio. Density testing of the products using the Archimedes method revealed that their density was consistently above 96%, indicating that this method can yield high-density bulk materials.

[0076] Figure 14 The image shown is a TEM (transmission electron microscope) image of product B3 obtained in this embodiment. A large number of uniformly distributed and oriented dislocation defects are present in the observed micro-region, indicating that this method has the effect of controlling the microstructure of bulk thermoelectric materials, especially the defects.

[0077] Example 4

[0078] A post-processing method for bulk thermoelectric materials, using cylindrical bulk Cu2Se samples, includes the following specific steps:

[0079] 1) Take two pieces with dimensions Φ13×20mm 3 Cylindrical bulk SnTe samples (prepared using self-propagating high-temperature synthesis technology combined with plasma-activated sintering process, with a density of 97%) were placed in containers with dimensions of (Φ60–Φ13) × 20 mm. 3 In the aluminum ring sleeve, BN spray is used to bond the cylindrical block to the aluminum ring sleeve as a whole, and they are numbered A4 and B4 respectively;

[0080] 2) Place the sample to be pressed obtained in step 1) into the same muffle furnace, raise the temperature from room temperature to 500℃ at a heating rate of 10℃ / min, and hold for 30min;

[0081] 3) The sample obtained by the heat treatment in step 2) is quickly taken out of the muffle furnace and placed on the press base. Products A4 and B4 are obtained by rapid stamping with an axial pressure of 425 MPa and a stamping speed of 2 mm / s. The compression ratio of group A4 is 0% and the compression ratio of group B4 is 50%.

[0082] Macroscopic morphology optical imaging was performed on product B4 obtained in step 3) of this embodiment, such as... Figure 15 As shown, there are no obvious cracks on its surface. The density of products A4 and B4 was tested using the Archimedes method and found to be 97.7% and 98.8% respectively, indicating that this method can obtain bulk materials with higher density.

[0083] Figure 16 The figure shows the total thermal conductivity of the product obtained in this embodiment as a function of temperature. As can be seen from the figure, this method can significantly reduce the thermal conductivity of Cu2Se at room temperature, indicating that this method can regulate the performance of bulk thermoelectric materials.

[0084] Example 5

[0085] A post-processing method for bulk thermoelectric materials, using cylindrical bulk CuCdInSe3 samples, includes the following specific steps:

[0086] 1) The dimensions are Φ15×20mm 3 A cylindrical bulk CuCdInSe3 sample (prepared by high-temperature melting combined with plasma-activated sintering process, with a density of 98%) was placed in a container with dimensions of (Φ60–Φ15) × 20 mm. 3 The cylindrical block is bonded to the aluminum ring sleeve using commercially available high-temperature resistant inorganic adhesive (ZS-1071) to form a single unit.

[0087] 2) Place the sample to be pressed obtained in step 1) into the same muffle furnace, raise the temperature from room temperature to 500℃ at a heating rate of 10℃ / min, and hold for 30min;

[0088] 3) The sample obtained by the heat treatment in step 2) is quickly taken out of the muffle furnace and placed on the press base. A high-performance bulk CuCdInSe3 material with a compression ratio of 55% is obtained by rapid stamping with an axial pressure of 425MPa and a stamping speed of 3mm / s.

[0089] The product obtained in this embodiment has no obvious cracks on its surface and a density higher than 98%.

[0090] Example 6

[0091] A post-processing method for bulk thermoelectric materials, taking a cylindrical bulk CoSb3 sample as an example, includes the following specific steps:

[0092] 1) The dimensions are Φ20×20mm 3 A cylindrical bulk CoSb3 sample (prepared using self-propagating high-temperature synthesis technology combined with plasma-activated sintering process, with a density of 97%) was placed in a container with dimensions of (Φ70–Φ20) × 20 mm. 3 In the magnesium ring sleeve, commercially available high-temperature resistant inorganic adhesive (ZS-1071) is used to bond the cylindrical block to the aluminum ring sleeve as a whole;

[0093] 2) Place the sample to be pressed obtained in step 1) into the same muffle furnace, raise the temperature from room temperature to 500℃ at a heating rate of 10℃ / min, and hold for 30min;

[0094] 3) The sample obtained in step 2) is quickly taken out of the muffle furnace and placed on the press base. High-performance bulk CoSb3 material with a compression ratio of 45% is obtained by rapid stamping with an axial pressure of 425MPa and a stamping speed of 3mm / s.

[0095] The product obtained in this embodiment has no obvious cracks on its surface and a density higher than 97%.

[0096] Example 7

[0097] A post-processing method for bulk thermoelectric materials, taking a cylindrical bulk Ag₂Se sample as an example, includes the following specific steps:

[0098] 1) The dimensions are Φ13×20mm 3 A cylindrical block of Ag₂Se sample (prepared by dissociation adsorption reaction combined with cold pressing, with a density of 97%) was placed in a container with dimensions of (Φ50–Φ13) × 20 mm. 3 In the magnesium-aluminum alloy ring sleeve, BN spray is used to bond the cylindrical block to the magnesium-aluminum alloy ring sleeve into one piece;

[0099] 2) Place the sample to be pressed obtained in step 1) into the same muffle furnace, raise the temperature from room temperature to 400℃ at a heating rate of 10℃ / min, and hold for 30min;

[0100] 3) The sample obtained in step 2) is quickly taken out of the muffle furnace and placed on the press base. A high-performance bulk Ag2Se material with a compression ratio of 50% is obtained by slow stamping with an axial pressure of 50MPa and a pressing rate of 0.01mm / s.

[0101] The product obtained in this embodiment has no obvious cracks on its surface and a density higher than 97%.

[0102] Example 8

[0103] A post-processing method for bulk thermoelectric materials, taking a cylindrical bulk ZrNiSn sample as an example, includes the following specific steps:

[0104] 1) The dimensions are Φ15×20mm 3 A cylindrical bulk ZrNiSn sample (prepared using self-propagating high-temperature synthesis technology combined with plasma-activated sintering process, with a density of 97%) was placed in a container with dimensions of (Φ55–Φ15) × 20 mm. 3 In the magnesium-aluminum alloy ring sleeve, commercially available high-temperature resistant inorganic adhesive ZS-1071 is used to bond the cylindrical block to the magnesium-aluminum alloy ring sleeve into one piece;

[0105] 2) Place the sample to be pressed obtained in step 1) into the same muffle furnace, raise the temperature from room temperature to 550°C at a heating rate of 10°C / min, and hold for 40 min;

[0106] 3) The sample obtained in step 2) is quickly taken out of the muffle furnace and placed on the press base. High-performance bulk ZrNiSn material with a compression ratio of 60% is obtained by rapid stamping with an axial pressure of 510MPa and a stamping rate of 3mm / s.

[0107] The product obtained in this embodiment has no obvious cracks on its surface and a density higher than 98%.

[0108] Example 9

[0109] A post-processing method for bulk thermoelectric materials, taking a cuboid bulk MgAgSb-based sample as an example, includes the following specific steps:

[0110] 1) The length × width × height dimensions are 13 × 13 × 20 mm 3 Bulk MgAgSb-based samples (prepared by high-energy ball milling combined with plasma-activated sintering, with a density of 94%) were placed in containers with dimensions of (Φ70–13×13)×20mm. 3In the aluminum ring sleeve, BN spray is used to bond the cylindrical block to the aluminum ring sleeve as a whole;

[0111] 2) Place the sample to be pressed obtained in step 1) into the same muffle furnace, raise the temperature from room temperature to 450°C at a heating rate of 10°C / min, and hold for 30 min;

[0112] 3) The sample obtained in step 2) is quickly taken out of the muffle furnace and placed on the press base. High-performance bulk MgAgSb material with a compression ratio of 50% is obtained by rapid stamping with an axial pressure of 350MPa and a stamping speed of 3mm / s.

[0113] The product obtained in this embodiment has no obvious cracks on its surface and a density higher than 97%.

[0114] Obviously, the above embodiments are merely examples for clear illustration and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A post-processing method for bulk thermoelectric materials, characterized in that, Includes the following steps: 1) The bulk thermoelectric material is embedded in a hollow plastic ring to obtain the sample to be pressed; 2) Heat and maintain the temperature of the entire sample to be compressed; 3) Apply pressure to the heated sample obtained in step 2) and press it to obtain the post-processed bulk thermoelectric material; The heating temperature is 50~550℃; The pressing rate is 1~10mm / s; The hollow structure of the plastic ring is matched with the shape and specifications of the bulk thermoelectric material, and the matching gap is 0. In step 3), during the pressing process, the compression ratio of the bulk thermoelectric material along the pressure direction is more than 5%.

2. The post-processing method according to claim 1, characterized in that, The bulk thermoelectric material has a regular shape.

3. The post-processing method according to claim 1, characterized in that, Step 1) The density of the bulk thermoelectric material is above 80%.

4. The post-processing method according to claim 1, characterized in that, The bulk thermoelectric material is a Bi2Te3-based compound; an MCdInSe3-based compound, wherein M = Cu or Ag; a SnQ-based compound, wherein Q = S, Se, or Te; a CoSb3-based compound; a half-Heusler alloy; a Cu2Q-based compound, wherein Q = S, Se, or Te; an Ag2Q-based compound, wherein Q = S, Se, or Te; an InSe-based compound; a MgAgSb-based compound; or a Mg3Sb2-based compound.

5. The post-processing method according to claim 1, characterized in that, The bulk thermoelectric material is bonded to the hollow plastic ring using BN spray or high-temperature resistant inorganic adhesive.

6. The post-processing method according to claim 1, characterized in that, The heat preservation time is 30~60 min.

7. The post-processing method according to claim 1, characterized in that, The applied pressure is 30~1000 MPa; the pressure direction is along the axial direction of the bulk thermoelectric material.

Images