A thermoelectric device with a protective layer and a method of manufacture

Abstract

A kind of thermoelectric device containing protective layer and preparation method, thermoelectric device includes thermoelectric conversion material, thermoelectric interface material, the thermoelectric interface material is compounded to at least part surface of the thermoelectric conversion material, at least part surface of the thermoelectric interface material is compounded with protective layer, the protective layer includes magnesium or magnesium alloy.Mg3Sb2-based thermoelectric material protected by coating has excellent stability, after 400 DEG C service for 30 days, the internal resistance change rate, the Seebeck coefficient change rate are all smaller.After large current density extreme test, the internal resistance change rate of material is smaller.

Description

Technical Field

[0001] This invention relates to the field of inorganic bulk thermoelectric technology, specifically to a thermoelectric device with a protective layer and its preparation method. Background Technology

[0002] Thermoelectric conversion technology is a green technology that directly converts waste heat into electrical energy. With the rapid development of the Internet of Things (IoT), a large number of sensors and wearable devices must operate independently and continuously. Thermoelectric conversion technology provides an effective solution for the self-powering of micro-devices. However, the reliability of thermoelectric devices remains an issue, especially for novel high-performance thermoelectric materials synthesized using non-steady-state methods. In existing Bi2Te3-based thermoelectric devices, the thermoelectric materials are synthesized using a melt-smelting steady-state method, exhibiting high stability at low temperatures. However, their raw material costs are high, and their thermoelectric performance at medium and high temperatures is poor, creating bottlenecks for their use in specialized fields. Mg3Sb2-based thermoelectric materials have low-temperature performance comparable to commercial Bi2Te3, and their raw material costs and mechanical properties are far superior to commercial bismuth telluride, showing broad application prospects. Nevertheless, in relatively high-temperature operating environments, the poor thermal stability of these materials easily leads to performance degradation and mechanical failure, hindering the industrial application of these materials. Summary of the Invention

[0003] According to a first aspect, in one embodiment, a thermoelectric device with a protective layer is provided, comprising a thermoelectric conversion material and a thermoelectric interface material, wherein the thermoelectric interface material is composited to at least a portion of the surface of the thermoelectric conversion material, and a protective layer is composited to at least a portion of the surface of the thermoelectric interface material, wherein the protective layer comprises magnesium or a magnesium alloy.

[0004] According to the second aspect, a method for preparing a thermoelectric device according to any one of the first aspects is provided, comprising:

[0005] The composite sintering step includes composited thermoelectric interface material onto at least a portion of the surface of thermoelectric conversion material, sintered, to obtain a thermoelectric device;

[0006] The coating step includes depositing a protective layer onto at least a portion of the surface of the thermoelectric device to obtain a thermoelectric device containing the protective layer.

[0007] According to the above embodiments, a thermoelectric device with a protective layer and its preparation method show that the Mg3Sb2-based thermoelectric material protected by the coating exhibits excellent stability. After 30 days of service at 400°C, the change rate of internal resistance and the change rate of Seebeck coefficient are both small. Even after extreme high current density testing, the change rate of internal resistance is small.

[0008] In one embodiment, the Mg3Sb2-based thermoelectric device protected by the coating exhibits high conversion efficiency and output power density at a hot-end temperature of 400°C and a cold-end temperature of 5°C. After 100 hours of in-situ testing at this temperature difference, the conversion efficiency and output power density show minimal changes. Attached Figure Description

[0009] Figure 1 A schematic diagram illustrating the fabrication process of Mg3Sb2-based thermoelectric devices;

[0010] Figure 2 The graph shows the changes in the surface microstructure of Mg3Sb2-based thermoelectric devices after annealing at 400℃ for different times.

[0011] Figure 3 The X-ray diffraction results of Mg3Sb2-based thermoelectric devices after annealing at 400℃ for different times are shown.

[0012] Figure 4-1 , Figure 4-2 , Figure 4-3 The graphs show the resistivity changes of Mg3Sb2-based thermoelectric devices after annealing at different temperatures for different times, as well as the resistance changes of the devices under high current densities. Figure 4-1 The graph shows the variation of the differential average resistivity of the sample within the temperature range of 30–500℃. Figure 4-2 The graph shows the change in resistivity of the sample at room temperature. Figure 4-3 For the sample at 8A / cm -2 The graph shows the change in internal resistance under high current density.

[0013] Figure 5 The rate of change of power generation and efficiency of Mg3Sb2-based thermoelectric devices were continuously tested for 100 hours at a hot end of 400°C and a cold end of 5°C.

[0014] Figure 6 The morphology and energy dispersive spectroscopy (EDS) images are shown in the transmission electron microscope (TEM) images.

[0015] Figure 7 This is an in-situ transmission electron microscope image of the substrate without any coating.

[0016] Figure 8 Electron micrograph of a Mg-plated coating;

[0017] Figure 9 Electron micrograph of a Mg+Cr composite coating only;

[0018] Figure 10 The surface morphology of the substrate after Mg and Mg+Cr coatings is shown.

[0019] Figure 11 SEM morphology changes for different metals plated;

[0020] Figure 12 The changes before and after testing for magnesium plating and ME20M plating, as well as SEM and energy dispersive spectroscopy (EDS) analysis graphs. Detailed Implementation

[0021] The present invention will now be described in further detail with reference to specific embodiments and accompanying drawings. In the following embodiments, many details are described to facilitate a better understanding of the present application. However, those skilled in the art will readily recognize that some features may be omitted in different situations, or may be replaced by other materials or methods. In some cases, certain operations related to the present application are not shown or described in the specification. This is to avoid obscuring the core parts of the present application with excessive description. For those skilled in the art, detailed description of these related operations is not necessary; they can fully understand the related operations based on the description in the specification and general technical knowledge in the art.

[0022] Furthermore, the features, operations, or characteristics described in the specification can be combined in any suitable manner to form various embodiments. At the same time, the steps or actions in the method description can be rearranged or adjusted in a manner obvious to those skilled in the art. Therefore, the various orders in the specification and drawings are only for the clear description of a particular embodiment and do not imply a necessary order, unless otherwise stated that a particular order must be followed.

[0023] The serial numbers assigned to components in this article, such as "first" and "second", are used only to distinguish the objects being described and have no sequential or technical meaning.

[0024] Improving the thermal stability of thermoelectric materials is crucial for obtaining reliable thermoelectric devices. To categorize the components of thermoelectric devices, this invention defines the metallization layer (used to improve the connection performance between the thermoelectric material and the electrode) as a thermoelectric interface material (TEiM), while defining the thermoelectric material in a narrower sense as a thermoelectric conversion material (TEcM). Traditional single-leg thermoelectric devices consist of TEiM and TEcM, i.e., a sandwich structure with TEcM in the middle and TEiM at both ends. In one embodiment, this invention uses magnesium alloy plating on the thermoelectric device to improve its stability; the fabrication process can be referred to... Figure 1 .

[0025] According to a first aspect, in one embodiment, a thermoelectric device with a protective layer is provided, comprising a thermoelectric conversion material and a thermoelectric interface material, wherein the thermoelectric interface material is composited to at least a portion of the surface of the thermoelectric conversion material, and a protective layer is composited to at least a portion of the surface of the thermoelectric interface material, wherein the protective layer comprises magnesium or a magnesium alloy.

[0026] In one embodiment, the protective layer is a magnesium alloy.

[0027] In one embodiment, the magnesium alloy includes, but is not limited to, at least one of ME20M, WE43, and AZ31, and the magnesium alloy can be purchased from the market.

[0028] In one embodiment, the thickness of the protective layer is 0.1–100 μm, preferably 0.1–10 μm, and more preferably 0.1–0.5 μm.

[0029] In one embodiment, the thermoelectric interface material comprises the following general chemical formula: Fe a Ti b Cr c Mn d Mg e , a=0.5~1.5; b=0.5~1.5; c=0.5~1.5; d=0.5~1.5; e=0.5~1.5.

[0030] In one embodiment, the thermoelectric conversion material comprises an n-type thermoelectric conversion material or a p-type thermoelectric conversion material.

[0031] In one embodiment, the thermoelectric conversion material comprises an n-type thermoelectric conversion material.

[0032] In one embodiment, the thermoelectric conversion material comprises a Mg-Sb-based thermoelectric conversion material.

[0033] In one embodiment, the thermoelectric conversion material comprises an n-type Mg-Sb-based thermoelectric conversion material.

[0034] In one embodiment, the thermoelectric conversion material comprises the following general chemical formula: Mg 3+δ Mn x Sb 2-y-z Bi y A z Where A is a group oxalic element, -0.2≤δ≤0.3; x=0.001~0.4; y=0~1.0; z=0~0.2.

[0035] In one embodiment, the oxalic elements include S, Se, or Te.

[0036] In one embodiment, the thickness of the thermoelectric conversion material can be 3 to 4 mm.

[0037] In one embodiment, the thickness of the thermoelectric interface material layer can be 1 to 1.5 mm.

[0038] In one embodiment, the thermoelectric device includes a single-leg thermoelectric device.

[0039] In one embodiment, the single-leg thermoelectric device includes a thermoelectric conversion material and a thermoelectric interface material compounded to the upper and lower surfaces of the thermoelectric conversion material.

[0040] In one embodiment, the thermoelectric interface material is composited to at least a portion of the surface of the thermoelectric conversion material by sintering.

[0041] In one embodiment, such as Figure 1 As shown, the two electrodes of the thermoelectric conversion material are sequentially combined with the thermoelectric interface material and the protective layer.

[0042] In one embodiment, an electrode layer is further laminated to the outer surface of the protective layer.

[0043] In one embodiment, the electrode layer includes, but is not limited to, copper (Cu).

[0044] According to the second aspect, in one embodiment, a method for fabricating a thermoelectric device according to any one of the first aspects is provided, comprising:

[0045] The composite sintering step includes composited thermoelectric interface material onto at least a portion of the surface of thermoelectric conversion material, sintered, to obtain a thermoelectric device;

[0046] The coating step includes depositing a protective layer onto at least a portion of the surface of the thermoelectric device to obtain a thermoelectric device containing the protective layer.

[0047] In one embodiment, the deposition method in the coating step includes, but is not limited to, magnetron sputtering, vacuum evaporation coating, or arc ion plating.

[0048] In one embodiment, during the coating step, the deposition power can be 50–200 W, and the duration can be 50–1000 W. s .

[0049] In one embodiment, the composite sintering step includes spark plasma sintering.

[0050] In one embodiment, the composite sintering step is carried out at 500–600°C and 30–60 MPa axial pressure.

[0051] In one embodiment, the sintering time in the composite sintering step is 5 to 10 minutes.

[0052] In one embodiment, during the composite sintering step, the heating rate to the sintering temperature is 50–100 °C / min. -1 Typically, the temperature is increased from room temperature to the sintering temperature.

[0053] In one embodiment, the preparation method of the thermoelectric conversion material in the composite sintering step includes: mixing the raw materials according to the ratio, ball milling under inert gas protection, and then sintering into a block by spark plasma sintering at 500-800°C, 5-10 min, and 30-60 MPa axial pressure.

[0054] In one embodiment, the method for preparing the thermoelectric interface material in the composite sintering step includes: mixing the raw materials according to the proportions, ball milling under inert gas protection, and obtaining alloy powder.

[0055] In one embodiment, in the composite sintering step, the raw materials used to prepare the thermoelectric conversion material and the thermoelectric interface material are all elemental raw materials.

[0056] In one embodiment, during the composite sintering step, the particle size of each elemental raw material is 100-300 mesh, and the purity is greater than 98%.

[0057] In one embodiment, during the composite sintering step, when preparing the thermoelectric conversion material and the thermoelectric interface material, the inert gas includes, but is not limited to, at least one of nitrogen (N2), helium (He), neon (Ne), argon (Ar), krypton (Kr), and xenon (Xe).

[0058] According to a third aspect, in one embodiment, a wearable device is provided, comprising a thermoelectric device according to any one of the first aspects.

[0059] According to a third aspect, in one embodiment, a sensor is provided that includes a thermoelectric device according to any one of the first aspects.

[0060] In response to the problems existing in the prior art, in one embodiment, the present invention designs a novel functional protective layer. Thermoelectric devices using this series of functional protective layers have excellent conversion efficiency, output power density and excellent thermal stability.

[0061] In one embodiment, the preparation method of TEcM includes: according to the designed ratio (Mg 3+δ Mn x Sb 2-y-z Bi y A z Where A is a group oxalic element S, Se or Te, -0.2≤δ≤0.3; x, y, z are atomic ratios, x=0.001~0.4; y=0~1.0; z=0~0.2) Weigh the raw materials, and then ball mill them in high energy for 5~10 hours under argon protection. The TEcM powder obtained after ball milling is sintered into blocks by spark plasma sintering at 500~800℃, 5~10min, and 30~60MPa axial pressure.

[0062] In one embodiment, the preparation method of TEiM includes: according to the designed ratio (Fe a Ti b Cr c Mn d Mg e(a, b, c, d, e are atomic ratios, where a = 0.5–1.5; b = 0.5–1.5; c = 0.5–1.5; d = 0.5–1.5; e = 0.5–1.5) Weigh the raw materials and obtain alloy powder by high-energy ball milling under argon protection for 10–20 hours using mechanical alloying.

[0063] In one embodiment, the method for preparing the TEiM / TEcM interface includes: forming the TEiM / TEcM contact interface by electro-plasma sintering of TEiM powder and TEcM bulk at 500–800°C, 5–10 min, and 30–60 MPa axial pressure. The heating rate during the sintering process is 50–100°C / min. -1 The thicknesses of the TEcM bulk and TEiM layer were designed to be 3–4 mm and 1–1.5 mm, respectively, to obtain a cylindrical sandwich structure. Finally, the sandwich structure after lamination and sintering was cut into cuboid blocks along the pressure direction for device fabrication.

[0064] In one embodiment, the method for preparing the functional protective layer of the device includes: using a magnesium element (Mg) or related magnesium alloy (such as ME20M, WE43, AZ31, etc., typical commercial magnesium alloys) target material by magnetron sputtering, vacuum evaporation, or arc ion plating, etc., with a coating thickness between 0.1 and 100 micrometers, a general power of the equipment between 50 and 200W, and a duration between 50 and 1000s.

[0065] In one embodiment, the beneficial effects achieved by this invention include:

[0066] After 15 days of service at 400℃, the Mg3Sb2-based thermoelectric device protected by the coating exhibited an internal resistance change rate of less than 10% and a Seebeck coefficient change rate of less than 10%. Following extreme high-current-density testing, the material's internal resistance change rate remained below 10%. Furthermore, the Mg3Sb2-based thermoelectric device with the subsequent coating protection achieved a conversion efficiency of 10% and an output power density of 1.5 W / cm² at a hot-end temperature of 400℃ and a cold-end temperature of 5℃. -2 After 100 hours of in-situ testing under this temperature difference, the conversion efficiency changed by less than 5%, and the output power density changed by less than 5%.

[0067] In one embodiment, the present invention prepares a functionalized protective coating for n-type Mg3Sb2-based thermoelectric devices, resulting in the best device stability in the industry and improving the practicality of Mg3Sb2-based thermoelectric devices.

[0068] In one embodiment, the target material used for experimental sputtering or evaporation is a pure magnesium target or a commercial magnesium alloy target (alloy grades include, but are not limited to, ME20M, WE43, and AZ31).

[0069] In the following examples and comparative examples, the particle size of the elemental raw materials used was 100-300 mesh, and the purity was greater than 98%. The sources of each raw material are as follows:

[0070] Fe powder, 200 mesh, 99.9% purity, manufactured by Macklin;

[0071] Mg scrap, purity greater than 99.9%, manufactured by Acros Organics;

[0072] Cr powder, 200 mesh, 99.9% purity, manufactured by Macklin;

[0073] Ti powder, 200 mesh, 99.9% purity, manufactured by Alfa;

[0074] Mn powder, 200 mesh, 99.5% purity, manufactured by Alfa;

[0075] Sb ingot, purity 99.999%, manufacturer is 5N plus;

[0076] Bi scraps, 99.999% pure, manufactured by 5N plus;

[0077] Te ingot, 99.999% purity, manufactured by 5N plus.

[0078] Example 1

[0079] The fabrication process of Mg3Sb2-based thermoelectric devices is as follows: Figure 1 As shown.

[0080] In this embodiment, the preparation method of TEcM is as follows: each elemental raw material is weighed according to the design ratio, and then high-energy ball milling (stainless steel ball, diameter 10mm) is carried out for 8 hours under argon protection. The TEcM powder obtained after ball milling is sintered into blocks by spark plasma sintering at 675℃ for 5min and 50MPa axial pressure.

[0081] In this embodiment, the preparation method of TEiM is as follows: each elemental raw material is weighed according to the design ratio, and alloy powder is obtained by high-energy ball milling (stainless steel ball with a diameter of 10 mm) for 1 to 2 hours under argon protection through mechanical alloying.

[0082] In this embodiment, the preparation method of the TEiM / TEcM interface is as follows: First, sample loading is performed, specifically, TEiM powder is spread in a graphite mold, that is, spread on the upper and lower surfaces of the TEcM block, forming a sandwich-like structure. Then, spark plasma sintering is performed. The TEiM powder and the TEcM block form the TEiM / TEcM contact interface through spark plasma sintering at 600℃ for 10 min and 30 MPa axial pressure. The heating rate during sintering is 100℃*min.-1 The thicknesses of the TEcM block and the TEiM layer are designed to be 4 mm and 1.5 mm, respectively.

[0083] In this embodiment, the chemical formula of TEcM is as follows: Mg 3.2 Mn 0.01 Sb 1.5 Bi 0.49 Te 0.01 The chemical formula of TEiM is as follows: FeTiCrMnMg. FeTiCrMnMg / Mg is prepared according to the above method. 3.2 Mn 0.01 Sb 1.5 Bi 0.49 Te 0.01 Contact interface.

[0084] Magnetron sputtering was used for coating. The target material was ME20M magnesium alloy purchased from Zhongnuo New Materials (the specific composition of ME20M magnesium alloy by mass percentage is as follows: Mg approximately 96.7-97.8%, Mn approximately 1.3-2.2%, Ce approximately 0.15-0.35%, Al ≤ 0.20%, Zn ≤ 0.30%, Si ≤ 0.10%, Cu ≤ 0.05%, Ni ≤ 0.007%, Fe ≤ 0.05%, Be ≤ 0.01%), and the vacuum degree was 10. -3 The sputtering parameters were: Pa, argon gas flow rate: 5 mL / min, sputtering power: 100 W, sputtering time: 200 s, and coating thickness: approximately 0.2 μm.

[0085] Example 2

[0086] TEcM: Mg 3.2 Mn 0.01 Sb 1.5 Bi 0.49 Te 0.01 TEiM: Fe7Mg2Ti, Fe7Mg2Ti / Mg was prepared according to the method in Example 1. 3.2 Mn 0.01 Sb 1.5 Bi 0.49 Te 0.01 Contact interface.

[0087] The coating was deposited using magnetron sputtering with a target of pure magnesium (purity: 5N, i.e., 99.999%) and a vacuum level of 10. -3 The sputtering parameters were: Pa, argon gas flow rate: 5 mL / min, sputtering power: 100 W, sputtering time: 200 s, and coating thickness: approximately 0.2 μm.

[0088] Comparative Example 1

[0089] In this comparative example, the chemical formula of the TEcM bulk obtained is as follows: Mg3.2 Mn 0.01 Sb 1.5 Bi 0.49 Te 0.01 TEiM: 304 stainless steel (304SS), 304 stainless steel / Mg was prepared according to the method in Example 1. 3.2 Mn 0.01 Sb 1.5 Bi 0.49 Te 0.01 Contact interface.

[0090] Comparative Example 1 was not coated.

[0091] The comparative analysis results are as follows:

[0092] Uncoated devices ( Figure 2 The first row, i.e., the As-fabricated group, and the Mg-plated devices ( Figure 2 The second row (Mg sputtering group) shows devices plated with ME20M. Figure 2 The third row (ME20M sputtering group) shows the changes in the surface microstructure of the sample after annealing at 400℃ for 30 days, as follows: Figure 2 As shown, the coating effectively protects the thermoelectric material. The uncoated surface becomes porous after annealing. While the Mg coating provides good protection, some cracks still appear after 30 days, indicating limited protective effect. This is mainly because pure magnesium has limited oxidation resistance, resulting in a loose oxide film that cannot prevent further oxidation. In contrast, the ME20M alloy protective coating exhibits a uniform and dense structure both before and after heat treatment, effectively inhibiting subsequent oxidation and decomposition.

[0093] like Figure 3 As shown, Figure 3 The phrase "after testing" refers to annealing at 400℃ for 30 days. X-ray diffraction analysis of the above samples revealed that the samples without a protective coating had higher oxidation peaks, while the samples with a protective coating had lower oxidation peaks. This indicates that the magnesium alloy protective coating effectively protected the thermoelectric material from deterioration, and the dense oxide film formed on the surface greatly improved the stability of the material.

[0094] Figure 4-1 In the middle, the vertical coordinate Δρ avg / ρ avg，0 It refers to the rate of change of average resistivity of thermoelectric devices at temperatures ranging from 30 to 500°C; Figure 4-2 In the figure, the vertical axis Δρ / ρ0 refers to the rate of change of resistivity of the thermoelectric device at 30℃; Figure 4-3 The vertical axis ΔR / R0 refers to the rate of change of internal resistance.

[0095] △ρ / ρ0、△ρ avg / ρ avg，0 It is calculated using the following formula: △ρ / ρ0=(ρ x -ρ0) / ρ0,△ρ avg / ρ avg，0 =(ρ avg，x -ρ avg，0 ) / ρ avg，0 , where subscript 0 is the initial value and subscript x is the value after different annealing times.

[0096] from Figure 4-1 It can be seen that ME20M has the lowest rate of change in average resistivity in the range of 30–500℃.

[0097] from Figure 4-2 As can be seen from the thermoelectric performance tests of the three samples, the sample with the ME20M protective coating showed the smallest change in thermoelectric resistivity, while the sample without the protective coating showed the largest change in thermoelectric resistivity. Figure 4-3 It is evident that, under high current density cycling tests of 100,000 times for 10 consecutive days, the sample with the ME20M protective coating was the most stable, indicating that the sample using the magnesium alloy coating has better overall stability.

[0098] In one embodiment, the thermoelectric devices prepared in Embodiments 1, 2, and Comparative Example 1 of the present invention have a conversion efficiency of approximately 10% and an output power density of approximately 1.5 W*cm². -2 Devices using the ME20M protective coating exhibit higher stability. For example... Figure 5 As shown, the conversion efficiency of the uncoated sample decreased by nearly 10% after 20 hours, while the device with ME20M protective coating showed no significant degradation in conversion efficiency and output power after 100 hours of testing.

[0099] Figure 5 In the figure, η represents the device conversion efficiency, P represents the output power, and the vertical axis represents the relative change of the above parameters.

[0100] Figure 6 The images show the morphology and energy dispersive spectroscopy (EDS) spectra. Figure 6 (a) indicates that the coating and the substrate are well bonded and there are no pores. Figure 6 (b) In-situ heating detection was used to observe the changes in morphology, which confirmed that the coating could work stably at 400℃, and Bi single-phase precipitation only began to appear at 430℃.

[0101] Figure 7The image shows an in-situ transmission electron microscope observation of the substrate without any coating. It can be seen that the substrate without any coating begins to precipitate black particles at 300-350°C, which is Bi single phase, while the substrate with a protective coating will only precipitate at 400°C.

[0102] Figure 8 The image shows an electron microscope image of a Mg-plated coating. It can be seen that there are gaps between the Mg-plated coating and the substrate, resulting in poor bonding performance, a loose and porous coating, and poor mechanical properties.

[0103] Figure 9 The image shows an electron microscope image of a Mg+Cr composite coating. It can be seen that although there is no gap between the coating and the substrate, the bonding performance is still poor, the coating is still loose and porous, and the mechanical properties are poor.

[0104] Figure 10 The images show the surface morphology of the substrate after Mg and Mg+Cr plating.

[0105] Figure 11 The image shows the SEM morphology changes of different metals. It can be seen that the surface coatings of different metals are dendritic and porous, and cannot form a dense layer similar to ME20M, thus preventing the failure of the substrate material.

[0106] Figure 12 The results of the tests on magnesium plating and ME20M plating, along with SEM and energy dispersive spectroscopy (EDS) images, show that the Mg plating cracked and peeled off after the test, failing to provide adequate protection, while the ME20M plating remained intact.

[0107] In one embodiment, high-energy ball-milled TEiM powder and TEcM sintered into a block by spark plasma sintering are further diffused and sintered into a block under conditions of 500–600°C, 5–10 min, and 30–60 MPa. The sample has a layered composite interface structure (TEiM / TEcM / TEiM), and the diffusion bonding is achieved using a spark plasma sintering process. Then, magnetron sputtering or vacuum evaporation deposition is performed, and the deposition layer includes, but is not limited to, Mg or its alloys.

[0108] In one embodiment, the present invention provides a novel, highly stable single-leg thermoelectric device that can be applied to an Internet of Things (IoT) self-powered system.

[0109] The reliability of thermoelectric devices largely depends on the thermal stability of the thermoelectric material itself. In one embodiment, this invention provides a type of coating protection for thermoelectric materials and its preparation method (the coating is a magnesium alloy, and the plating process is physical deposition plating methods such as magnetron sputtering, vacuum evaporation plating, or arc ion plating). After 15 days of service at 400°C, the Mg3Sb2-based thermoelectric material protected by the coating exhibits an internal resistance change rate of less than 10% and a Seebeck coefficient change rate of less than 10%. After extreme high current density testing, the material's internal resistance change rate is less than 10%. Furthermore, the Mg3Sb2-based thermoelectric device protected by the coating achieves a conversion efficiency of 10% and an output power density of 1.5 W*cm² at a hot-end temperature of 400°C and a cold-end temperature of 5°C. -2 After 100 hours of in-situ testing under this temperature difference, the conversion efficiency changed by less than 5%, and the output power density changed by less than 5%.

[0110] The above examples illustrate the present invention only to aid in understanding it and are not intended to limit the scope of the invention. Those skilled in the art can make various simple deductions, modifications, or substitutions based on the principles of this invention.

Claims

1. A thermoelectric device with a protective layer, characterized in that, The thermoelectric conversion material and the thermoelectric interface material are included. The thermoelectric interface material is composited to at least a portion of the surface of the thermoelectric conversion material. At least a portion of the surface of the thermoelectric interface material is composited with a protective layer. The protective layer includes magnesium or a magnesium alloy. The thermoelectric conversion material contains a Mg-Sb-based thermoelectric conversion material. The thermoelectric interface material comprises the following general chemical formula: Fe a Ti b Cr c Mn d Mg e , a=0.5~1.5; b=0.5~1.5; c=0.5~1.5; d=0.5~1.5; e=0.5~1.5; The thermoelectric conversion material comprises the following general chemical formula: Mg 3+δ Mn x Sb 2-y-z Bi y A z Where A is a group oxalic element, -0.2≤δ≤0.3; x=0.001~0.4; y=0~1.0; z=0~0.

2.

2. The thermoelectric device as described in claim 1, characterized in that, The magnesium alloy includes at least one of ME20M, WE43, and AZ31.

3. The thermoelectric device as described in claim 1, characterized in that, The thickness of the protective layer is 0.1~100μm.

4. The thermoelectric device as described in claim 3, characterized in that, The thickness of the protective layer is 0.1~10μm.

5. The thermoelectric device as described in claim 4, characterized in that, The thickness of the protective layer is 0.1~0.5μm.

6. The thermoelectric device as described in claim 1, characterized in that, The thermoelectric conversion material includes n-type thermoelectric conversion material or p-type thermoelectric conversion material.

7. The thermoelectric device as claimed in claim 1, characterized in that, The thermoelectric conversion material includes n-type Mg-Sb-based thermoelectric conversion materials.

8. The thermoelectric device as claimed in claim 1, characterized in that, The oxalic elements include S, Se, or Te.

9. The thermoelectric device as claimed in claim 1, characterized in that, The thickness of the thermoelectric conversion material is 3~4mm.

10. The thermoelectric device as claimed in claim 1, characterized in that, The thickness of the thermoelectric interface material layer is 1~1.5mm.

11. The thermoelectric device as claimed in claim 1, characterized in that, The thermoelectric device includes a single-leg thermoelectric device.

12. The thermoelectric device as claimed in claim 11, characterized in that, The single-leg thermoelectric device includes a thermoelectric conversion material and a thermoelectric interface material compounded to the upper and lower surfaces of the thermoelectric conversion material.

13. The thermoelectric device as claimed in claim 1, characterized in that, The thermoelectric interface material is composited to at least a portion of the surface of the thermoelectric conversion material by sintering.

14. The thermoelectric device as claimed in claim 1, characterized in that, The thermoelectric conversion material has a thermoelectric interface material and a protective layer sequentially bonded to its two electrode ends.

15. The thermoelectric device as claimed in claim 14, characterized in that, An electrode layer is also laminated to the outer surface of the protective layer.

16. The method for preparing a thermoelectric device according to any one of claims 1 to 15, characterized in that, include: The composite sintering step includes composited thermoelectric interface material onto at least a portion of the surface of thermoelectric conversion material, sintered, to obtain a thermoelectric device; The coating step includes depositing a protective layer material onto at least a portion of the surface of the thermoelectric device to obtain a thermoelectric device containing a protective layer.

17. The preparation method according to claim 16, characterized in that, In the coating process, the deposition methods include magnetron sputtering, vacuum evaporation coating, or arc ion plating.

18. The preparation method according to claim 16, characterized in that, In the coating process, the deposition power is 50~200W and the duration is 50~1000s.

19. The preparation method according to claim 16, characterized in that, In the composite sintering step, the sintering includes spark plasma sintering.

20. The preparation method according to claim 16, characterized in that, In the composite sintering step, the sintering is carried out at 500~600 ℃ and 30~60 MPa axial pressure.

21. The preparation method according to claim 16, characterized in that, In the composite sintering step, the sintering time is 5~10 minutes.

22. The preparation method according to claim 20, characterized in that, In the composite sintering process, the rate of heating to the sintering temperature is 50~100 ℃*min. -1 .

23. A wearable device, characterized in that, It includes the thermoelectric device according to any one of claims 1 to 15.

24. A sensor, characterized in that, It includes the thermoelectric device according to any one of claims 1 to 15.

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