A single-arm GeTe thermoelectric device, a preparation method and application thereof

Abstract

This invention discloses a single-arm GeTe thermoelectric device, its fabrication method, and its applications, relating to the field of thermoelectric materials and devices. It includes a GeTe thermoelectric arm, barrier layers disposed at the upper and lower ends of the GeTe thermoelectric arm, and an electrode layer disposed outside the barrier layers. The GeTe thermoelectric arm has a cuboid structure with a square cross-section, and the ratio of the height to the side length of the cross-section is 2. This invention optimizes the side length and height of the cross-section of the single-arm GeTe thermoelectric device, achieving a device size range with high conversion efficiency.

Description

Technical Field

[0001] This invention relates to the field of thermoelectric materials and devices, and in particular to a single-arm GeTe thermoelectric device, its preparation method, and its application. Background Technology

[0002] Thermoelectric conversion technology can realize the direct conversion between thermal energy and electrical energy. It has advantages such as no moving parts, no noise, small size, high reliability, and environmental friendliness. It has broad application prospects in fields such as industrial waste heat recovery, automobile exhaust waste heat power generation, distributed solid-state power generation, and solid-state refrigeration.

[0003] GeTe-based thermoelectric materials are among the most promising thermoelectric materials in the mid-temperature range (300-800K). They possess high Seebeck coefficients, suitable band gap widths, and excellent electrical and thermal performance tunability, making them an ideal alternative to traditional lead-containing PbTe thermoelectric materials. They have received widespread attention in recent years.

[0004] Currently, most research on GeTe-based materials focuses on intrinsic performance optimization, using methods such as doping, defect engineering, and nanocomposites to improve the thermoelectric figure of merit (ZT). However, research on the geometric design of GeTe devices, especially the impact of the thermoelectric arm length, width, and height matching of single-arm devices on conversion efficiency, is severely lacking.

[0005] Compared to traditional π-type devices, single-arm thermoelectric devices do not require pairing of p-type and n-type materials, resulting in a simpler structure, fewer interfaces, and easier packaging, making them particularly suitable for miniaturized and integrated applications. However, existing single-arm GeTe devices suffer from high ohmic and thermal conductivity losses, excessively high interface contact resistance, and actual conversion efficiencies far below the material's theoretical limits. This prevents the full utilization of the superior performance of GeTe-based materials, severely restricting the practical application of single-arm GeTe devices. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a single-arm GeTe thermoelectric device, its fabrication method, and its applications. This invention optimizes the cross-sectional side length and height of the thermoelectric arm to obtain a single-arm GeTe thermoelectric device structure with high conversion efficiency.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A single-arm GeTe thermoelectric device includes a GeTe thermoelectric arm, a barrier layer disposed at the upper and lower ends of the GeTe thermoelectric arm, and an electrode layer disposed outside the barrier layer. The GeTe thermoelectric arm has a cuboid structure with a square cross-section. The ratio of the height of the GeTe thermoelectric arm to the side length of the cross-section is 2.

[0009] The GeTe thermoelectric arm has a cross-sectional side length of 3-5mm and a height of 6-10mm.

[0010] The GeTe thermoelectric arm has a cross-sectional side length of 5mm and a height of 10mm.

[0011] The material of the GeTe thermoelectric arm is a multi-doped GeTe-based thermoelectric material with the general chemical formula Ge. 1-3x- y Ag x Pb x Sb x Bi y Te 1-z Se z Where x=0.11, y=0.01, z=0.1.

[0012] The barrier layer is a SnTe thermoelectric material, and the thickness of the SnTe barrier layer is 0.2-0.6 mm.

[0013] The electrode layer is a Cu electrode layer with a thickness of 1-2 mm.

[0014] The above-mentioned method for fabricating a single-arm GeTe thermoelectric device includes the following steps:

[0015] S1 Stacked Sample Loading: In the graphite mold, electrode layer powder, barrier layer powder, GeTe thermoelectric powder, barrier layer powder and electrode layer powder are laid out in sequence from bottom to top to form a symmetrical sandwich stacked structure and complete the sample loading.

[0016] S2 Hot Press Molding: The completed graphite mold is placed in a hot press sintering equipment and sintered under vacuum and pressure to obtain a composite thermoelectric block with GeTe thermoelectric arm substrate, barrier layer and electrode layer integrated.

[0017] S3 Single-Arm Machining: The obtained composite thermoelectric block (GeTe thermoelectric arm substrate) is cut into a cuboid single arm of a preset size, and then ground and polished for later use; the preset size is a cuboid structure with a square cross-section and the ratio of the height of the cuboid structure to the side length of the cross-section is 2.

[0018] In step S1, the GeTe thermoelectric powder is prepared by the following method: high-purity Ge, Te and doped element are mixed in a preset stoichiometric ratio, vacuum sealed and then melted at high temperature, quenched and annealed to obtain GeTe alloy ingot, and the GeTe alloy ingot is ball-milled.

[0019] In step S1, the barrier layer powder is prepared by the following method: high-purity Sn and Te are mixed in a preset stoichiometric ratio, vacuum sealed, and then melted and quenched at high temperature to obtain SnTe alloy ingots. The SnTe alloy ingots are then ball-milled.

[0020] The above-mentioned single-arm GeTe thermoelectric devices are used in the fields of industrial waste heat recovery in the mid-temperature range, automobile exhaust waste heat power generation, and distributed solid-state power generation.

[0021] The beneficial effects of this invention are as follows:

[0022] (1) This invention optimizes the cross-sectional side length and height of the single-arm GeTe thermoelectric device to obtain a device size range with high conversion efficiency. Experimental results show that when the thermoelectric arm size is 5mm×5mm×10mm, the device exhibits high thermoelectric conversion efficiency.

[0023] (2) The size design adopted in this invention is conducive to improving the matching relationship between the ohmic loss and thermal conduction loss of the device, and helps to reduce the proportion of interface contact resistance in the total internal resistance, thereby improving the overall thermoelectric conversion performance of the device.

[0024] (3) The device structure of the present invention is relatively simple, the preparation process is controllable, and it has good repeatability. It is suitable for application scenarios such as industrial waste heat recovery in the medium temperature range, automobile exhaust waste heat power generation and distributed solid-state power generation. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the overall structure of the single-arm GeTe thermoelectric device of the present invention.

[0026] Figure 2 The graph shows the thermoelectric conversion performance test results of Example 1, Comparative Example 1, and Comparative Example 2.

[0027] In the attached figure, 1-GeTe thermoelectric arm, 2-barrier layer, 3-electrode layer. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0029] The inventors discovered that the lack of systematic optimization in the size design of single-arm GeTe devices, along with unreasonable aspect ratios and poor matching between cross-sectional area and height, are the main reasons why the actual conversion efficiency of the devices is far lower than the theoretical limit of the material. Based on this, this invention optimizes the cross-sectional side length and height of the thermoelectric arm to obtain a single-arm GeTe thermoelectric device structure with higher conversion efficiency.

[0030] See Figure 1 The present invention provides a single-arm GeTe thermoelectric device, which includes a GeTe thermoelectric arm 1, a barrier layer 2 disposed at the upper and lower ends of the GeTe thermoelectric arm 1, and an electrode layer 3 disposed outside the barrier layer 2. The GeTe thermoelectric arm 1 has a cuboid structure with a square cross-section. The ratio of the height of the GeTe thermoelectric arm 1 to the side length of the cross-section is 2.

[0031] Specifically, the cross-sectional side length of the GeTe thermoelectric arm 1 is 3-5mm, and the height of the GeTe thermoelectric arm 1 is 6-10mm.

[0032] More preferably, the cross-sectional side length of the GeTe thermoelectric arm 1 is 5mm, and the height of the GeTe thermoelectric arm 1 is 10mm.

[0033] The material of the GeTe thermoelectric arm 1 is a multi-doped GeTe-based thermoelectric material with the general chemical formula Ge. 1-3x- y Ag x Pb x Sb x Bi y Te 1-z Se z Where x=0.11, y=0.01, z=0.1.

[0034] The barrier layer 2 is a SnTe thermoelectric material with a thickness of 0.2-0.6 mm; the electrode layer 3 is a Cu electrode layer with a thickness of 1-2 mm.

[0035] The above-mentioned method for fabricating a single-arm GeTe thermoelectric device includes the following steps:

[0036] S1 Layered Sample Preparation: In the graphite mold, electrode layer powder, barrier layer powder, GeTe thermoelectric powder, barrier layer powder and electrode layer powder are laid out sequentially from bottom to top to form a symmetrical sandwich layered structure, thus completing the sample preparation; after each layer of powder is laid, it is lightly pressed to level it, ensuring that there is no cross-contamination between layers and that the thickness is uniform.

[0037] S2 Hot Press Molding (Integrated Hot Press Molding for Preparing Composite Thermoelectric Blocks): The prepared graphite mold is placed in a hot press sintering equipment and sintered under vacuum and pressure to obtain a composite thermoelectric block consisting of a GeTe thermoelectric arm substrate, barrier layer 2, and electrode layer 3 integrally formed; specifically, the prepared graphite mold is placed in a hot press sintering equipment and vacuumed to 1×10⁻⁶. -2 Below Pa, the temperature is raised to 400-500℃, and a sintering pressure of 40-50MPa is applied simultaneously. The temperature and pressure are maintained for 5-30 minutes. After the holding period, the temperature is lowered to room temperature with the furnace, and the pressure is slowly released before demolding to obtain an integrated composite thermoelectric block with a GeTe thermoelectric arm matrix, a SnTe barrier layer and a Cu electrode that are simultaneously densified. The relative density of the block is ≥98%, the interface is well bonded, and there is no obvious interdiffusion of elements.

[0038] S3 Single-Arm Machining: The obtained composite thermoelectric block (mainly the GeTe thermoelectric arm substrate) is cut into cuboid single arms of a preset size, and then ground and polished for later use. The preset size is a cuboid structure with a square cross-section, and the ratio of the height of the cuboid structure to the side length of the cross-section is 2. Specifically, the sintered thermoelectric device block is first processed into cuboid single arms using a wire cutting machine. The processed thermoelectric arm is then ground with sandpaper at progressively finer grits from 800 grit to 5000 grit to remove the surface cutting damage layer and oxide layer, thus obtaining the single-arm GeTe thermoelectric device.

[0039] In step S1, the GeTe thermoelectric powder is preferably prepared using the following method: high-purity Ge, Te, and doping elemental substances are mixed according to a preset stoichiometric ratio, vacuum-sealed, and then melted at high temperature, quenched, and annealed to obtain a GeTe alloy ingot. The GeTe alloy ingot is then ball-milled. The specific operating steps are as follows: using high-purity Ge (99.999%), Te (99.999%), Ag (99.999%), Pb (99.999%), Sb (99.999%), Bi (99.999%), and Se (99.999%) as raw materials, according to Ge... 1-3x-y (AgPbSb) x Bi y Te 1-z Se z The stoichiometric ratio is accurately measured and the sample is placed in a high-purity quartz tube; the quartz tube is then evacuated to a vacuum of 1×10⁻⁶. -3 After the material is melted and sealed below Pa, it is placed in a tube furnace and heated to 900-1000℃ and held for 8-10 hours to allow the raw material to fully melt and react. Then, the quartz tube is removed, quickly quenched in ice water, and then annealed in a box furnace at 600-680℃ for 48-96 hours to obtain Ge. 1-3x-y (AgPbSb) x Bi y Te 1-z Sez Ingot casting; the ingot is ground into powder using a ball mill and sealed for later use under an argon protective atmosphere.

[0040] The barrier layer powder in step S1 is prepared by the following method: high-purity Sn and Te are mixed according to a preset stoichiometric ratio, vacuum-sealed, and then melted and quenched at high temperature to obtain a SnTe alloy ingot. The SnTe alloy ingot is then ball-milled. The specific operating steps are as follows: high-purity Sn (99.999%) and Te (99.999%) are used as raw materials, accurately weighed according to the stoichiometric ratio of SnTe, with a total mass of 10g, and placed in a high-purity quartz tube; the quartz tube is then evacuated to 1×10⁻⁶. -3 After the Pa is below 1, it is melted and sealed, placed in a tube furnace, heated to 850-950℃ and held for 6-10 hours to allow the raw materials to fully melt and react. Then it is cooled to 600℃ and held for 48-72 hours for annealing treatment to obtain SnTe ingots. The ingots are ground into powder using a ball mill and sealed for later use under an argon protective atmosphere.

[0041] Example 1:

[0042] This embodiment provides a single-arm GeTe thermoelectric device based on size control design. The specific fabrication steps are as follows:

[0043] 1. Preparation of GeTe-based thermoelectric powder: Using 99.999% high-purity Ge, Te, Ag, Pb, Sb, Bi, and Se elements as raw materials, according to Ge... 0.66 Ag 0.11 Pb 0.11 Sb 0.11 Bi 0.01 Te 0.9 Se 0.1 Weigh 10g, vacuum seal (vacuum degree ≤ 1×10 -3 After Pa), the ingot is melted and reacted in a tubular furnace at 950-1000℃ for 10 hours, and then quenched in ice water to obtain an ingot; the ingot is then ground and vacuum-packed for later use.

[0044] 2. Preparation of SnTe barrier layer powder: Using 99.999% high-purity Sn and Te as raw materials, 10g of SnTe is weighed according to the SnTe stoichiometric ratio, and SnTe dense barrier layer block is prepared by the same vacuum melting, quenching, grinding and hot pressing sintering process.

[0045] 3. Integrated molding: In a graphite mold with an inner diameter of 13.2mm, Cu electrode sheet, SnTe barrier layer, GeTe substrate, SnTe barrier layer, and Cu electrode sheet are laid sequentially from bottom to top to form a symmetrical stacked structure; hot-pressed and held at 450-500℃ and 40-50MPa for 10-30 minutes under vacuum, and demolded to obtain an integrated composite thermoelectric block.

[0046] 4. Single-arm machining: The composite block is cut into a rectangular single arm of 5×5×10mm (cross-section 5mm×5mm, height 10mm), and after grinding and polishing, the target device is obtained.

[0047] Compare with Example 1:

[0048] The only difference between this comparative example and Example 1 is that the dimensions of the single arm of the cuboid are 3mm×3mm×7mm (cross-section 3mm×3mm, height 7mm; the ratio of height to cross-section side length is 2.3). The rest of the preparation steps and test conditions are exactly the same.

[0049] Compare with Example 2:

[0050] The only difference between this comparative example and Example 1 is that the dimensions of the single arm of the cuboid are 3mm×3mm×9mm (cross-section 3mm×3mm, height 9mm; the ratio of height to cross-section side length is 3). The rest of the preparation steps and test conditions are exactly the same.

[0051] The thermoelectric conversion performance of Example 1, Comparative Example 1, and Comparative Example 2 was tested, and the results are as follows: Figure 2 As shown. Figure 2 The test results show that the maximum conversion efficiency η of the three single-arm GeTe thermoelectric devices is [missing information]. max All depend on the temperature difference between the hot and cold ends The increase in T showed a significant monotonic upward trend.

[0052] Throughout the entire tested temperature range, the 5×5×10mm device from Example 1 consistently exhibited optimal thermoelectric conversion performance, with its η... max The temperature difference was significantly higher than that of Control Example 1 and Control Example 2 at all test temperature points. Specific performance characteristics are as follows:

[0053] When ΔT = 400K, the η of the device in Example 1 max The percentage reached 13.6%, compared to control example 2 (3×3×9mm, η). max =10.3%), an increase of 32.0%, compared to control example 1 (3×3×7mm, η max =8.1%) increased by 68%;

[0054] It is worth noting that as the temperature difference between the hot and cold ends increases, the efficiency difference between the device in Example 1 and the control example device continues to widen, indicating that the optimized size structure of the present invention has more significant performance advantages under large temperature difference conditions, and is perfectly adapted to typical large temperature difference application scenarios such as industrial waste heat recovery in the medium temperature range and automobile exhaust waste heat power generation.

[0055] The core mechanism by which this invention significantly improves the conversion efficiency of single-arm GeTe devices through geometric dimension control lies in:

[0056] First, the preferred thermoelectric arm of this invention has a size of 5×5×10mm and an aspect ratio (height / cross-sectional side length) of 2, achieving an optimal balance between ohmic loss and thermal conduction loss. The reasonable increase in the height of the thermoelectric arm reduces heat leakage and improves the effective utilization of the temperature difference between the hot and cold ends; while the increase in cross-section significantly reduces the bulk resistance of the thermoelectric arm and reduces Joule heat loss during current flow. The synergistic optimization of these two factors maximizes the conversion efficiency.

[0057] Second, a larger cross-sectional area can significantly reduce the absolute value of the interfacial contact resistance and its proportion in the total internal resistance of the device, greatly reducing interfacial Joule heat loss and interfacial thermal resistance, and fully utilizing the intrinsic superior performance of GeTe-based thermoelectric materials. The 3×3mm cross-sectional area of ​​Comparative Examples 1 and 2 is relatively small, and the proportion of interfacial contact resistance is high, which becomes the core factor limiting the performance of the device. The 5×5mm cross-section of the present invention effectively solves this technical bottleneck.

[0058] Third, the optimally sized device of this invention has superior thermal stress matching characteristics. Under large temperature difference operating conditions, the thermal stress distribution inside the thermoelectric arm is more uniform, avoiding problems such as interface cracking and increased contact resistance under large temperature differences, thus ensuring the performance stability of the device in high-temperature and large-temperature-difference environments. Even at T=400K, the conversion efficiency can still be continuously improved without significant performance degradation.

[0059] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention. The above embodiments are provided only for the purpose of describing the present invention and are not intended to limit the present invention. Parts not described in detail in this specification are well-known in the art and are not intended to limit the scope of the present invention. The scope of the present invention is defined by the appended claims. All equivalent substitutions and modifications made without departing from the spirit and principle of the present invention should be covered within the scope of the present invention.

Claims

1. A single-arm GeTe thermoelectric device, characterized in that, It includes a GeTe thermoelectric arm, a barrier layer disposed at the upper and lower ends of the GeTe thermoelectric arm, and an electrode layer disposed outside the barrier layer. The GeTe thermoelectric arm has a cuboid structure with a square cross-section. The ratio of the height of the GeTe thermoelectric arm to the side length of the cross-section is 2.

2. The single-arm GeTe thermoelectric device according to claim 1, characterized in that, The cross-sectional side length of the GeTe thermoelectric arm is 3-5mm, and the height of the GeTe thermoelectric arm is 6-10mm.

3. The single-arm GeTe thermoelectric device according to claim 2, characterized in that, The GeTe thermoelectric arm has a cross-sectional side length of 5mm and a height of 10mm.

4. The single-arm GeTe thermoelectric device according to claim 1, characterized in that, The material of the GeTe thermoelectric arm is a multi-doped GeTe-based thermoelectric material with the general chemical formula Ge. 1-3x-y Ag x Pb x Sb x Bi y Te 1-z Se z Where x=0.11, y=0.01, z=0.

1.

5. The single-arm GeTe thermoelectric device according to claim 1, characterized in that, The barrier layer is a SnTe thermoelectric material, wherein the thickness of the SnTe barrier layer is 0.2-0.6 mm.

6. The single-arm GeTe thermoelectric device according to claim 1, characterized in that, The electrode layer is a Cu electrode layer, and the thickness of the electrode layer is 1-2 mm.

7. The method for fabricating the single-arm GeTe thermoelectric device according to any one of claims 1 to 6, characterized in that, Includes the following steps: S1 Stacked Sample Loading: In the graphite mold, electrode layer powder, barrier layer powder, GeTe thermoelectric powder, barrier layer powder and electrode layer powder are laid out in sequence from bottom to top to form a symmetrical sandwich stacked structure and complete the sample loading. S2 Hot Press Molding: The completed graphite mold is placed in a hot press sintering equipment and sintered under vacuum and pressure to obtain a composite thermoelectric block with GeTe thermoelectric arm substrate, barrier layer and electrode layer integrated. S3 Single-arm machining: The obtained composite thermoelectric block is cut into a rectangular single arm of a preset size, and then ground and polished for later use; The preset dimensions are a cuboid structure with a square cross-section. The ratio of the height of the cuboid structure to the side length of the cross-section is 2.

8. The method for fabricating a single-arm GeTe thermoelectric device according to claim 7, characterized in that, The GeTe thermoelectric powder in step S1 is prepared by the following method: high-purity Ge, Te and doping element are mixed in a preset stoichiometric ratio, vacuum sealed in a tube, and then melted, quenched and annealed at high temperature to obtain a GeTe alloy ingot. The GeTe alloy ingot is then ball-milled.

9. The method for fabricating a single-arm GeTe thermoelectric device according to claim 7, characterized in that, The barrier layer powder in step S1 is prepared by the following method: high-purity Sn and Te are mixed in a preset stoichiometric ratio, vacuum sealed, and then melted and quenched at high temperature to obtain SnTe alloy ingots. The SnTe alloy ingots are then ball-milled.

10. The application of the single-arm GeTe thermoelectric device according to any one of claims 1 to 6 in the fields of industrial waste heat recovery in the mid-temperature range, automobile exhaust waste heat power generation, and distributed solid-state power generation.

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