High-reliability thermoelectric device introduced with foam connection layer and preparation method thereof
By introducing a foam bonding layer at the interface of thermoelectric devices, the problem of thermal stress accumulation under medium and high temperature thermal cycling is solved, and the long-term stability and electrical performance of the devices are improved. This method is applicable to a variety of thermoelectric material systems and device forms.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- NINGBO INST OF MATERIALS TECH & ENG CHINESE ACAD OF SCI
- Filing Date
- 2026-01-07
- Publication Date
- 2026-05-12
AI Technical Summary
Existing medium- and high-temperature thermoelectric devices suffer from performance degradation and structural failure due to the accumulation of interfacial thermal stress during long-term thermal cycling. Traditional rigid interface designs are difficult to effectively solve this problem.
A foam bonding layer is introduced at the interface of the thermoelectric device. The interfacial thermal stress caused by the mismatch of the coefficient of thermal expansion is released by the metal foam material with low equivalent Young's modulus and deformability. The foam is then welded to form a multi-layer synergistic structure with the barrier layer to ensure electrical connection and chemical stability.
It significantly improves the service stability and service life of thermoelectric devices under medium and high temperature and repeated thermal cycling conditions, taking into account both electrical performance and mechanical reliability, and is suitable for a variety of thermoelectric material systems and device forms.
Smart Images
Figure CN122028637A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of thermoelectric device technology, and more specifically, to a high-reliability thermoelectric device incorporating a foam bonding layer and its preparation method. Background Technology
[0002] Thermoelectric devices, based on the Seebeck effect, achieve direct conversion between heat and electrical energy. They offer advantages such as no moving parts, reliable operation, and environmental friendliness, showing broad application prospects in fields such as industrial waste heat recovery, deep space exploration, radioactive isotope power sources, and distributed energy systems. In recent years, with the continuous improvement of thermoelectric material performance, especially the high-temperature thermoelectric material system represented by PbTe achieving high thermoelectric figures of merit (zT) in the 600–800 K temperature range, the initial output power and energy conversion efficiency of thermoelectric devices have met the basic requirements for engineering applications.
[0003] However, compared to improvements in material performance, the long-term stability of thermoelectric devices under actual service conditions is becoming increasingly prominent. In medium- and high-temperature operating conditions, thermoelectric devices typically need to withstand large temperature gradients and frequent start-up and shutdown cycles. The resulting repeated thermal cycling introduces significant thermal stress between the functional layers within the device. Due to the significant differences in thermal expansion coefficients, Young's modulus, and plastic deformation capabilities among thermoelectric materials, barrier layers, metal electrodes, and weld layers, free thermal strain mismatch inevitably occurs at the interfaces during thermal cycling, further evolving into interfacial shear stress and peel stress.
[0004] In existing technologies, research to improve the service reliability of thermoelectric devices mainly focuses on improving interfacial chemical stability. For example, this involves introducing a barrier layer between the thermoelectric material and the metal electrode to suppress element diffusion, prevent the formation of brittle phases, and reduce contact resistivity. Common barrier layer materials are screened based on a match between chemical stability and mechanical properties. While these methods improve interfacial chemical compatibility and initial electrical performance to some extent, their design philosophy is still based on an integrated structure. Each interfacial layer typically strives for a balance of electrical properties, mechanical properties, and chemical inertness, which inevitably leads to incompatibility issues and hinders the search for suitable materials.
[0005] Further research by the inventors revealed that even with low interfacial resistance and effective suppression of chemical reactions, traditional rigid interface structures still struggle to prevent the continuous accumulation of thermal stress at the interface. As the number of thermal cycles increases or the temperature difference widens, microcracks easily form at the interface and gradually propagate, eventually leading to barrier layer cracking, solder layer fatigue failure, and even thermoelectric arm detachment, manifesting as irreversible degradation of device output power and efficiency. This indicates that relying solely on optimizing the interface material composition is insufficient to address the reliability issues of thermoelectric devices under medium- and high-temperature thermal cycling conditions from a mechanical perspective.
[0006] Therefore, it is urgent to propose a novel thermoelectric device structure that can effectively release or alleviate interfacial thermal stress during thermal cycling while ensuring good electrical connection and chemical stability, so as to break through the limitations of traditional rigid integrated design on the long-term service performance of the device. Summary of the Invention
[0007] The technical problem to be solved by the present invention is that existing medium and high temperature thermoelectric devices suffer from performance degradation and structural failure due to the accumulation of interfacial thermal stress during long-term thermal cycling. In order to overcome the above-mentioned defects of the prior art, the present invention provides a high reliability thermoelectric device with a foam bonding layer and its preparation method.
[0008] The first aspect of the present invention provides a method for fabricating a high-reliability thermoelectric device incorporating a foam bonding layer, comprising the following steps: S1. Prepare thermoelectric material powder and barrier layer material powder respectively, and lay the barrier layer material powder on the high-temperature end of the thermoelectric material powder, and form an integrated thermoelectric material layer-barrier layer composite block through sintering process; S2. Cut the thermoelectric material layer-barrier layer composite block obtained in step S1 to obtain at least one initial thermoelectric arm with a barrier layer. S3. Weld a metal foam material with a connected porous structure to the surface of the barrier layer of the initial thermoelectric arm. The equivalent Young's modulus of the metal foam material is lower than that of the thermoelectric material layer and the barrier layer, thus obtaining a functional thermoelectric arm with a foam connecting layer. S4. In the mold, the high-temperature end and low-temperature end of the functional thermoelectric arm are assembled with the corresponding metal electrodes or a substrate covered with metal electrodes. Then, the high-temperature end and low-temperature end of the functional thermoelectric arm are welded to the corresponding metal electrodes to form a thermoelectric device.
[0009] In the above scheme, by setting an independent foam connecting layer between the barrier layer material and the metal electrode and introducing it into the interface structure through welding, while ensuring good electrical connection and chemical stability, the equivalent stiffness of the interface is effectively reduced, and the interfacial thermal stress caused by the mismatch of thermal expansion coefficients is released, thereby significantly improving the service reliability of the thermoelectric device under medium and high temperature and repeated thermal cycling conditions. The thermoelectric material, barrier layer, and foam connecting layer are designed in a synergistic structure, and an integrated sintering—surface modification and processing—foam connecting layer welding—modular assembly process route is adopted. This significantly improves the service stability and service life of the thermoelectric device under medium and high temperature thermal cycling conditions while ensuring low contact resistance and excellent initial output performance. A multi-layer synergistic interface structure of "thermoelectric material layer—barrier layer—foam connecting layer—metal electrode" is constructed at the hot end of the thermoelectric arm. The foam bonding layer is made of metal and alloy materials with interconnected porous structures. Through its low equivalent Young's modulus and deformability, the interfacial thermal stress caused by the mismatch of thermal expansion coefficients is released by the compressibility and deformability of the interconnected porous structure. The barrier layer is used to suppress element interdiffusion and form a stable ohmic contact. The barrier layer achieves metallurgical bonding through an integrated sintering process, thus taking into account both mechanical reliability and electrical performance.
[0010] In one possible implementation, the thermoelectric material powder is a material system suitable for medium and high temperature working conditions, selected from at least one of PbTe-based thermoelectric materials, GeTe-based thermoelectric materials, Half-Heusler alloy system materials, and Skutterudite-based materials.
[0011] In one possible implementation, the barrier layer powder is at least one of the following: metal powder, metal-based compound powder, nitride ceramic powder, carbide ceramic powder, and oxide ceramic powder, which are chemically stable and used to block element diffusion reactions. The resulting barrier layer is disposed between the thermoelectric material layer and the foam bonding layer to reduce interfacial resistance and suppress interfacial reactions.
[0012] In one possible implementation, the sintering process is induction sintering, hot pressing sintering, or spark plasma sintering.
[0013] In one possible implementation, the metal foam material is at least one of the following: transition metal foam material, light metal foam material, transition metal alloy foam material, and light metal alloy foam material, which have stable properties under medium and high temperature conditions.
[0014] In one possible implementation, the porosity of the foam connecting layer is 20% to 80%. The structural parameters, such as the porosity, of the foam connecting layer are within a range that provides deformability.
[0015] In one possible implementation, the welding in step S3 is at least one of diffusion welding, brazing, and metal-based solder welding, wherein the solder used is at least one of tin-based solder, lead-based solder, copper-based solder, and silver-based solder; the welding at the high-temperature end in step S4 is performed by diffusion welding, brazing, or metal-based solder welding, wherein the solder used is at least one of tin-based solder, lead-based solder, copper-based solder, and silver-based solder.
[0016] In one possible implementation, the surface of the metal foam material is further subjected to at least one of electroplating, electroless plating, or spraying before step S3. The plating material used for electroplating, electroless plating, or spraying is at least one of metals and their compounds that can produce a wetting effect with the solder used for welding in step S3 and the solder used for high-temperature end welding in step S4.
[0017] A second aspect of the present invention provides a highly reliable thermoelectric device incorporating a foam bonding layer, which is prepared by the above-described preparation method.
[0018] In one possible implementation, the thermoelectric device is a medium-high temperature thermoelectric power generation module with a working hot end temperature of not less than 700K.
[0019] The beneficial effects of this invention are as follows: 1. By introducing a foam bonding layer, interfacial thermal stress is alleviated at the structural level, breaking through the reliability limitations of traditional thermoelectric device designs that integrate interface materials and functions. 2. The foam bonding layer is introduced through subsequent welding, which provides strong process control and is easily compatible with existing thermoelectric device manufacturing processes; 3. While ensuring the basic electrical performance of the device, significantly improve the service stability of thermoelectric devices under medium and high temperature and repeated thermal cycling conditions; 4. A general preparation method applicable to various thermoelectric material systems and device forms is provided, which has potential for engineering applications. Attached Figure Description
[0020] Figure 1 A schematic diagram of the high-temperature end interface structure of the thermoelectric module prepared in this application; Figure 2 This is a process flow diagram of the preparation process of Examples 1-3 of this application; Figure 3 The graphs show the maximum output power and efficiency of the modules in Embodiments 1-3 and Comparative Example 1 of this application as a function of temperature. Figure 4 This is a graph showing the maximum output power and efficiency cyclic test data of the module in Embodiment 1 of this application; Figure 5 This is a graph showing the maximum output power and efficiency cycle test data of the module in Embodiment 2 of this application; Figure 6 This is a graph showing the maximum output power and efficiency cycle test data of the module in Embodiment 3 of this application; Figure 7 This is a graph showing the maximum output power and efficiency cyclic test data of the module in Comparative Example 1 of this application; Figure 8 The figures show the thermal stress simulation results of Comparative Example 1 and Example 3 of this application;
[0021] Figure 9 This is a schematic diagram of the device assembly structure of Embodiment 1 of this application. Detailed Implementation
[0022] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. It should be noted that the following embodiments are only used to illustrate the implementation methods and typical parameters of the present invention, and are not intended to limit the parameter range described in the present invention. Reasonable variations derived therefrom are still within the protection scope of the claims of the present invention.
[0023] It should be noted that the endpoints and any values of the ranges disclosed herein are not limited to the precise ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, the endpoint values of the various ranges, the endpoint values of the various ranges and individual point values, and individual point values can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed herein.
[0024] Unless otherwise defined, all terms, symbols, and other scientific terms used herein are intended to have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. In some instances, terms having a conventional meaning are defined herein for clarification or ease of reference, and such definitions should not be construed as indicating a significant difference from conventional understanding in the art. The technical methods described or referenced herein are generally well understood by those skilled in the art and employed by conventional methods. Unless otherwise stated, the use of commercially available kits, reagents, and instruments shall be performed according to the manufacturer's instructions and parameters.
[0025] This invention provides a highly reliable thermoelectric device incorporating a foam bonding layer, which constructs a multi-layered synergistic interface structure at the high-temperature end of the thermoelectric arm, consisting of a thermoelectric material layer, a barrier layer, a foam bonding layer, and a metal electrode. The foam bonding layer is made of a metal foam material with a connected porous structure, which releases interfacial thermal stress caused by thermal expansion coefficient mismatch through its low equivalent Young's modulus and deformability. The barrier layer inhibits element interdiffusion and forms a stable ohmic contact. The multi-layered structure is metallurgically bonded through an integrated sintering process combined with welding, thus balancing mechanical reliability and electrical performance.
[0026] The high-temperature end structure design drawing of the thermoelectric device is referenced. Figure 1 , refer to Figure 2 The flowchart illustrates a method for fabricating a high-reliability thermoelectric device by introducing a foam bonding layer, comprising the following steps: S1. Construction of the thermoelectric material layer-barrier layer structure: According to Pb 1-x M x Te (M=Na,K), Pb 1-x TeM x (M=Bi,Sb,Cu), Ge 1-x M x Te (M=Sb, Bi, In, Pb, Sn), Half-Heusler alloy system materials of the general formula XYZ (where X is at least one of Ti, Zr, Hf, Y is Ni, Co, or Fe, and Z is Sn, Sb, or Bi) or Skutterudite-based materials MX3 or A x M4X 12 High-purity raw materials are selected according to a predetermined stoichiometric ratio of the general formula (where M is a transition metal such as Co, Rh, Ir, Fe, Ru, etc., X is a main group element such as P, As, Sb, and A is a filler atom such as Na, Nd, Yb, Sr, Ba) to prepare p-type and n-type thermoelectric materials. High-purity raw materials are also weighed according to the stoichiometric ratio of the barrier layer materials (such as Fe, Co, Ti, Fe7Sb3, SnTe, Fe-Te alloy, TiO2) to prepare the barrier layers. The raw materials for each thermoelectric material and each barrier layer are mixed separately and then sealed in a vacuum environment for high-temperature melting. Subsequently, uniform thermoelectric material ingots and barrier layer ingots are obtained through rapid cooling.
[0027] The thermoelectric material ingot and the barrier layer ingot are further pulverized and refined into powder to obtain thermoelectric material powder and barrier layer powder. The thermoelectric material powder and barrier layer powder are sequentially laid up, and then a dense, integrated thermoelectric material layer-barrier layer composite block is prepared using a sintering process. The sintering process is induction sintering, hot pressing sintering, or spark plasma sintering. Different types of thermoelectric materials can be sintered at different temperatures and holding times according to their physical properties, thereby obtaining a thermoelectric arm matrix with good electrical and mechanical properties. The barrier layer powder is at least one of the following: metal powder, metal-based compound powder, nitride ceramic powder, carbide ceramic powder, and oxide ceramic powder, which are used to block element diffusion reactions and have chemical stability.
[0028] S2, Precision Machining: The integrated thermoelectric material layer-barrier layer composite block is machined to achieve predetermined dimensions. After cleaning, the machined composite block is cut into multiple initial thermoelectric arms to meet modular assembly requirements.
[0029] S3, Surface Modification The surface of the metal foam material is subjected to at least one of the following surface modification treatments: electroplating, electroless plating, or spraying. The plating material used in electroplating, electroless plating, or spraying is at least one of a metal or its compound that can wet the solder used in step S4 and the solder used in the high-temperature end welding in step S5, thereby improving the bonding reliability between the solder used when welding the foam connecting layer and the barrier layer, and between the foam connecting layer and the metal electrode. The metal foam material is at least one of the following: a transition metal foam material, a light metal foam material, a transition metal alloy foam material, and a light metal alloy foam material that exhibits stable performance under medium- and high-temperature conditions.
[0030] S4. The barrier layer and the foam bonding layer are constructed as an integrated unit: A surface-modified metal foam material is welded to the barrier layer end of the initial thermoelectric arm to form a foam connecting layer. The metal foam material has a connected porous structure and an equivalent Young's modulus lower than that of the thermoelectric material layer and the barrier layer. The metal foam material is at least one of the following: transition metal foam material, light metal foam material, transition metal alloy foam material, and light metal alloy foam material, which exhibit stable performance under medium- and high-temperature conditions. Preferably, it is at least one of Fe-based alloy foam, metallic Fe foam, metallic Al foam, and metallic Ti foam. A functional thermoelectric arm with a foam connecting layer is obtained. The barrier layer improves interfacial electrical bonding and inhibits interfacial reactions. The porosity of the foam connecting layer is 20%-80%, making it a deformable structural layer used to alleviate interfacial thermal stress generated during thermal cycling. The welding in step S4 is at least one of diffusion welding, brazing, and metal-based solder welding, wherein the solder used is at least one of tin-based solder, lead-based solder, copper-based solder, and silver-based solder. In step S4, since the foam connecting layer is made of metal and alloy materials with porous or compressible structures, after the thermoelectric material and the barrier layer are sintered, the foam connecting layer is introduced by welding to prevent the pore structure of the metal foam material from collapsing during high-temperature sintering, thereby maintaining good deformability and thus constructing an integrated hot end structure of thermoelectric material layer / interface barrier layer / foam connecting layer.
[0031] S5, Thermoelectric Module Assembly: In the mold, the high-temperature end and low-temperature end of the functional thermoelectric arm are assembled with corresponding metal electrodes or a substrate covered with metal electrodes according to the required assembly structure. Then, the high-temperature end and low-temperature end of the functional thermoelectric arm are welded together with the corresponding metal electrodes to form a thermoelectric device, also known as a thermoelectric module. The specific welding steps are as follows: one end of the functional thermoelectric arm with the foam connecting layer is designated as the high-temperature end, and the other end as the low-temperature end. The high-temperature end and the low-temperature end are welded to the metal electrodes respectively using different welding materials, such as welding at 290°C for 10 minutes, to adapt to the service requirements in different temperature ranges. The high-temperature end welding in step S5 is at least one of diffusion welding, brazing, and metal-based solder welding, wherein the solder used is at least one of tin-based solder, lead-based solder, copper-based solder, and silver-based solder. The welding material for the high-temperature end in step S5 is preferably Ag-based solder that is stable at high temperatures, and the welding material for the low-temperature end is selected from low-melting-point solder paste. Preferably, in step S5, high-temperature stable welding materials such as nano-silver paste are used at the high-temperature end, and low-melting-point welding materials such as SnBi solder paste are used at the low-temperature end.
[0032] The aforementioned thermoelectric material system, barrier layer material, and foam connecting layer material are not limited to the material combinations shown, but are only used to illustrate the structural design concept proposed in this application. The thermoelectric material layer is selected from thermoelectric material systems suitable for medium- and high-temperature operating conditions; the interface barrier layer is selected from functional materials capable of forming a stable electrical connection between the thermoelectric material and the subsequent connecting structure and blocking the diffusion of interface elements; the foam connecting layer is selected from at least one of transition metals, light metals, and their alloy foam materials with a connected porous structure to provide deformability and reduce the equivalent stiffness of the interface. In one embodiment, the thermoelectric material can be a PbTe-based thermoelectric material, FeSb or SnTe can be selected as the barrier layer, and Fe-Ni alloy foam can be selected as the foam connecting layer.
[0033] S6. The assembled devices can be tested and evaluated for service life: The assembled thermoelectric module was placed in a vacuum environment for performance testing. By applying different temperature conditions to the hot and cold ends of the thermoelectric module to establish a stable temperature gradient, the output voltage, current, and output power of the module were measured, and the heat flow information during the device's operation was acquired simultaneously.
[0034] In the same embodiment, under test conditions where the cold end temperature is maintained at 300K and the hot end temperature varies between 643K and 753K, the output stability of the device under long-term thermal cycling conditions is evaluated, and the thermoelectric energy conversion efficiency is calculated based on the relationship between output power and heat flow, thereby verifying the effect of the foam connecting layer structure on improving the service reliability of the thermoelectric device.
[0035] The technical effects of the present invention will be further explained below with reference to the accompanying drawings and specific embodiments.
[0036] Example 1 This example fabricates a PbTe-based thermoelectric device and provides a thermoelectric module structure incorporating a foam bonding layer, with reference to... Figure 1 In this design, a barrier layer is positioned between the thermoelectric material layer and the foam bonding layer to improve interfacial electrical connectivity and suppress interfacial reactions. The foam bonding layer, serving solely as a functional layer for alleviating thermal stress, forms a metallurgical bond above the barrier layer. In this embodiment, the high-temperature end of the n-type thermoelectric arm is sequentially composed of n-type PbTe / FeSb / Fe-Ni alloy foam, and the high-temperature end of the p-type thermoelectric arm is sequentially composed of p-type PbTe / SnTe / FeSb / Fe-Ni alloy foam. In one implementation, the porosity, pore size, or skeleton structure parameters of the foam bonding layer are set within a range that can significantly reduce its equivalent Young's modulus while maintaining structural continuity, for example, it can be set to 20%–80%, but is not limited thereto.
[0037] The PbTe-based thermoelectric device in this embodiment is fabricated through the following steps: S1, according to Na 0.02 Pb 0.98 p-type PbTe-based thermoelectric materials and their corresponding barrier layer materials were prepared according to the stoichiometric ratio of Te, Fe7Sb3, and SnTe. 0.96 Ge 0.05 Cu 0.02 Te 0.96 Se 0.04 n-type PbTe-based thermoelectric materials and their corresponding barrier layer materials were prepared using a stoichiometric ratio of Fe7Sb3. The raw materials were mixed and sealed in a vacuum environment for high-temperature (1323K) melting, followed by rapid cooling (quenching at room temperature) to obtain uniform thermoelectric material ingots and barrier layer ingots. These ingots were further pulverized and refined into thermoelectric material powder and barrier layer powder, respectively. The corresponding thermoelectric material powder and barrier layer powder were sequentially laid out, and then a dense, integrated thermoelectric material layer-barrier layer composite block was formed using an induction sintering process. The sintering temperature for n-type elements was 500℃, with a holding time of 20 min; the sintering temperature for p-type elements was 550℃, with a holding time of 10 min, resulting in the integrated thermoelectric material layer-barrier layer composite block.
[0038] S2. Cut the integrated thermoelectric material layer-barrier layer composite block into 3.5mm*3.5mm p-type initial thermoelectric arm and n-type initial thermoelectric arm that are suitable for device assembly. S3. Surface treatment of Fe7Ni3 alloy foam material, namely cleaning the surface of Fe7Ni3 alloy foam material, and then electroplating Ni and Sn. Electroplating Ni for 30 minutes at a constant current of 1.5A and Sn for 20 minutes at a constant current of 2A to improve its weldability. The high-temperature end foam connecting layer of the S4 and p-type initial thermoelectric arms is prepared using commercially available Fe7Ni3 alloy foam material with a porosity of 20%. The Fe7Ni3 alloy foam material is welded to the barrier layer side of the p-type initial thermoelectric arm using Ag-based solder at 290°C for 5 minutes to obtain the p-type functional thermoelectric arm. Similarly, the high-temperature end foam connecting layer of the n-type initial thermoelectric arm is also prepared using commercially available Fe7Ni3 alloy foam material (with a porosity of 20%). The Fe7Ni3 alloy foam material is welded to the barrier layer side of the n-type initial thermoelectric arm using Ag-based solder at 290°C for 5 minutes to obtain the n-type functional thermoelectric arm.
[0039] S5. Assemble the high-temperature and low-temperature ends of the p-type functional thermoelectric arm and the high-temperature and low-temperature ends of the n-type functional thermoelectric arm with the corresponding Cu-coated Al3O2 substrate in the mold (e.g., Figure 9 As shown, the assembly method is as follows: a high-temperature Al3O2 ceramic substrate, N hot-end electrodes, N thermoelectric units, N cold-end electrodes, and a low-temperature Al3O2 ceramic substrate are sequentially pressed together along the direction from the heat source to the cold source. Each thermoelectric unit includes a pair of p-type and n-type thermoelectric arms connected in series. The p-type thermoelectric arm in one thermoelectric unit is connected in series with the n-type thermoelectric arm in the adjacent thermoelectric unit via the hot-end and cold-end electrodes. In the figure, the p-type and n-type thermoelectric arms are marked in red and blue respectively for easy distinction. Figure 9 This is just a schematic diagram. The red and blue colors can be interchanged. The solder paste represents the low-temperature end of the welding process. The high-temperature end of the welding process is not shown in the diagram. The high-temperature end Cu electrode is welded to the high-temperature end of the functional thermoelectric arm using Ag-based solder at 290°C for 10 minutes. The low-temperature end Cu electrode is welded to the low-temperature end of the functional thermoelectric arm using SnBi solder paste at room temperature to form a thermoelectric device.
[0040] Example 2 The difference between this embodiment and Embodiment 1 is that the porosity parameter of the foam bonding layer is increased to 40%, thereby enhancing its effect on improving interfacial thermal stress. The other steps are the same as in Embodiment 1.
[0041] Example 3: This embodiment further increases the porosity of the foam connecting layer to 60% based on Embodiment 2, thereby enhancing the deformability of the foam connecting layer and improving its stress release and redistribution effect under thermal cycling conditions. Other steps are the same as in Embodiment 1.
[0042] Example 4: This embodiment fabricates a GeTe-based thermoelectric device to support the selection of GeTe thermoelectric materials and elemental metal foam materials. Its structural form is as follows: Figure 1 A barrier layer is placed between the thermoelectric material layer and the foam bonding layer to improve the interfacial electrical connection and suppress interfacial reactions; the foam bonding layer serves as a functional layer to alleviate thermal stress, forming a metallurgical bond. The high-temperature end of the n-type thermoelectric arm is sequentially composed of n-type PbTe / FeSb / foam Ti, while the high-temperature end of the p-type thermoelectric arm is composed of Ge. 0.95 Sb 0.05 Te / Co / Foam Ti.
[0043] The GeTe-based thermoelectric device in this embodiment is fabricated through the following steps: S1, according to Ge 0.95 Sb 0.05 p-type GeTe-based thermoelectric materials and their corresponding barrier layer materials were prepared using a stoichiometric ratio of Te and Co. The raw materials were mixed and then sealed in a vacuum environment for high-temperature (1173 K) melting. Following this, uniform thermoelectric material ingots and barrier layer ingots were obtained through rapid cooling (quenching at room temperature). These ingots were further pulverized and refined into thermoelectric material powder and barrier layer powder, respectively. The corresponding thermoelectric material powder and barrier layer powder were sequentially laid together, and then a dense, integrated thermoelectric material layer-barrier layer composite block was formed using a spark plasma sintering process. The p-type element was sintered at 520°C for 15 min to obtain the integrated thermoelectric material layer-barrier layer composite block. The n-type element used the n-type PbTe material and its barrier layer from Example 1.
[0044] S2. Cut the integrated thermoelectric material layer-barrier layer composite block into 3.5mm*3.5mm p-type initial thermoelectric arm and n-type initial thermoelectric arm that are suitable for device assembly. S3. Surface treatment of the foamed Ti material, namely cleaning the surface of the foamed Ti material, and then electroplating Ni and Sn. Electroplating Ni for 30 minutes at a constant current of 1.5A and Sn for 20 minutes at a constant current of 2A to improve its solderability. The high-temperature end foam connecting layer of the S4 and p-type initial thermoelectric arm is prepared using commercially available foam Ti with a porosity of 60%. The foam Ti is then soldered to one side of the barrier layer of the p-type initial thermoelectric arm using SnPbAg solder at 300°C for 5 minutes to obtain the p-type functional thermoelectric arm. Similarly, the high-temperature end foam connecting layer of the n-type initial thermoelectric arm is also prepared using foam Ti (with a porosity of 60%). The foam Ti is then soldered to one side of the barrier layer of the n-type initial thermoelectric arm using SnPbAg solder at 300°C for 5 minutes to obtain the n-type functional thermoelectric arm.
[0045] S5. Assemble the high-temperature end and low-temperature end of the p-type functional thermoelectric arm and the n-type functional thermoelectric arm with the corresponding Al3O2 substrate with Cu electrode in the mold (assembly method is the same as in Example 1). Then, use SnPbAg solder to weld the high-temperature end Cu electrode to the high-temperature end of the functional thermoelectric arm at 320°C for 10 minutes. Use SnBi solder paste to weld the low-temperature end Cu electrode to the low-temperature end of the functional thermoelectric arm at room temperature to form a thermoelectric device.
[0046] Example 5: This embodiment fabricates a Half-Heusler-based thermoelectric device to support the selection of Half-Heusler thermoelectric materials and ceramic powder barrier layers. Its structural form is as follows: Figure 1 The high-temperature ends of the n-type thermoelectric arm are successively n-type Hf 0.5 Zr 0.5 NiSn / TiO2 / foamed Cu, with the high-temperature end of the p-type thermoelectric arm being NbFeSb / TiO2 / foamed Cu.
[0047] The Half-Heusler-based thermoelectric device of this embodiment is fabricated through the following steps: S1, according to Hf 0.5 Zr 0.5 Half-Heusler-based thermoelectric materials and barrier layers were prepared using a stoichiometric ratio of NiSn, NbFeSb, and TiO2. The raw materials were mixed and then sealed in a vacuum environment for high-temperature (1573 K) melting. Following this, a rapid cooling process (quenching at room temperature) was used to obtain uniform thermoelectric material ingots and barrier layer ingots. These ingots were further pulverized and refined into thermoelectric material powder and barrier layer powder, respectively. The corresponding thermoelectric material powder and barrier layer powder were sequentially layered, and then a dense, integrated thermoelectric material layer-barrier layer composite block was formed using a spark plasma sintering process. The n-type material was sintered at 1173 K and 40 MPa for 20 min, and the p-type material was sintered at 1153 K and 40 MPa for 20 min, resulting in the integrated thermoelectric material layer-barrier layer composite block.
[0048] S2. Cut the integrated thermoelectric material layer-barrier layer composite block into 4mm*4mm p-type initial thermoelectric arm and n-type initial thermoelectric arm for device assembly. The subsequent preparation steps are the same as in Example 4.
[0049] Example 6: This embodiment fabricates a Skutterudite-based thermoelectric device to support the selection of Skutterudite thermoelectric material and barrier layer. Its structural form is as follows: Figure 1 The high-temperature ends of the n-type thermoelectric arm are sequentially n-type Yb. 0.2 Co4Sb 12 / NiSb / foamed Cu, p-type thermoelectric arm high-temperature end is Ce 0.3 Fe3CoSb 12 / NiSb / foam Cu.
[0050] The HH-based thermoelectric device in this embodiment is fabricated through the following steps: S1, according to Yb 0.2 Co4Sb 12 NiSb, Ce 0.3 Fe3CoSb 12 Skutterudite-based thermoelectric materials and barrier layers were prepared using a stoichiometric method. The raw materials were mixed and then sealed in a vacuum environment for high-temperature (1373 K) melting. Following this, a rapid cooling process (quenching at room temperature) was used to obtain uniform thermoelectric material ingots and barrier layer ingots. These ingots were further pulverized and refined into thermoelectric material powder and barrier layer powder, respectively. The corresponding thermoelectric material powder and barrier layer powder were sequentially layered and then vacuum-sintered at 873 K and 55 MPa for 15 minutes using a spark plasma sintering process to obtain an integrated thermoelectric material layer-barrier layer composite block.
[0051] S2. Cut the integrated thermoelectric material layer-barrier layer composite block into 4mm*4mm p-type initial thermoelectric arm and n-type initial thermoelectric arm for device assembly. The subsequent preparation steps are the same as in Example 4.
[0052] Comparative Example 1: To compare and verify the effect of the foam connecting layer, this comparative example provides a thermoelectric module structure of the same type as Example 1 without introducing a foam connecting layer. The high-temperature end of the n-type thermoelectric arm is a conventional n-type PbTe / FeSb structure, and the high-temperature end of the p-type thermoelectric arm is a p-type PbTe / FeSb / SnTe structure. Other steps are consistent with Example 1.
[0053] To verify the mitigation effect of the foam bonding layer on interfacial thermal stress, thermal stress simulation analysis was performed on Example 3, which introduced the foam bonding layer, and Comparative Example 1, which did not introduce the foam bonding layer. Under the same temperature load conditions, the stress distribution in the thermoelectric interface region was compared and calculated.
[0054] Device testing and analysis were performed on Examples 1-3 and Comparative Example 1. The high-temperature end temperature was raised to 803 K during the heating process, and cyclic testing was conducted between 643 K and 753 K at the high-temperature end temperature. The results are as follows: Figure 3-8 As shown, Figure 3 The graphs show the maximum output power and efficiency of the modules in Embodiments 1-3 and Comparative Example 1 of this application as a function of temperature. Figure 4 This is a graph showing the maximum output power and efficiency cyclic test data of the module in Embodiment 1 of this application; Figure 5 This is a graph showing the maximum output power and efficiency cycle test data of the module in Embodiment 2 of this application; Figure 6 This is a graph showing the maximum output power and efficiency cycle test data of the module in Embodiment 3 of this application; Figure 7 This is a graph showing the maximum output power and efficiency cyclic test data of the module in Comparative Example 1 of this application; Figure 8 The figures show the thermal stress simulation results for Comparative Example 1 and Example 3 of this application. (Through...) Figure 3 It can be seen that after introducing foam connecting layers with different structural parameters into the thermoelectric device, the overall output performance of the device remains within an acceptable range, and the energy conversion efficiency of the module does not decrease significantly, while the output power exhibits certain differences under different implementation methods. Test results show that the structural characteristics of the foam connecting layer, while regulating interfacial stress, also affect the heat transfer path of the device, thus impacting the output power. Furthermore, when the deformability of the foam connecting layer is enhanced, its stress relief effect is more significant, but it may also introduce additional thermal resistance. Therefore, in practical applications, the structural parameters of the foam connecting layer can be rationally selected according to actual service conditions to achieve a balance between stress buffering capacity and device output performance. Figure 4-7 As can be seen, the control module without a buffer layer experienced a rapid performance decline in the early stages of testing, indicating that traditional rigid interface structures are ill-suited to the interfacial thermal stress generated under repeated temperature changes. In contrast, the module with a foam connecting layer maintained a relatively stable output state during thermal cycling. Furthermore, with the optimization of the foam connecting layer's structural parameters, its improvement effect on thermal cycling stability became more pronounced. This demonstrates that a foam connecting layer with appropriate porosity can effectively adapt to the mismatch in thermal expansion coefficients of different materials within the thermoelectric module, resulting in the thermoelectric module obtained in this embodiment exhibiting good stability and structural reliability during service. Figure 8Theoretical calculations show that under the same temperature load conditions, the stress at the interface is significantly reduced after introducing the foam bonding layer, effectively suppressing stress concentration at the interface. The thermoelectric device structure with a foam bonding layer proposed in this application can significantly improve the service reliability of thermoelectric devices under medium- and high-temperature thermal cycling conditions without significantly sacrificing electrical performance, and has good prospects for engineering applications.
[0055] Examples 4-6 verify that various thermoelectric material systems can be applied to the structural design of this invention.
[0056] The above description is merely a specific embodiment of this application, but the scope of protection of this application is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in this application should be included within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.
Claims
1. A method for fabricating a high-reliability thermoelectric device incorporating a foam bonding layer, characterized in that, Includes the following steps: S1. Prepare thermoelectric material powder and barrier layer material powder respectively, and lay the barrier layer material powder on the high-temperature end of the thermoelectric material powder, and form an integrated thermoelectric material layer-barrier layer composite block through sintering process; S2. Cut the thermoelectric material layer-barrier layer composite block obtained in step S1 to obtain at least one initial thermoelectric arm with a barrier layer. S3. Weld a metal foam material with a connected porous structure to the surface of the barrier layer of the initial thermoelectric arm. The equivalent Young's modulus of the metal foam material is lower than that of the thermoelectric material layer and the barrier layer, thus obtaining a functional thermoelectric arm with a foam connecting layer. S4. In the mold, the high-temperature end and low-temperature end of the functional thermoelectric arm are assembled with the corresponding metal electrode or a substrate covered with metal electrode. Then, the high-temperature end and low-temperature end of the functional thermoelectric arm are welded to the corresponding metal electrode to form a thermoelectric device.
2. The preparation method according to claim 1, characterized in that, The thermoelectric material powder is selected from at least one of PbTe-based thermoelectric materials, GeTe-based thermoelectric materials, Half-Heusler alloy system materials, and Skutterudite-based materials.
3. The preparation method according to claim 1, characterized in that, The barrier layer powder is at least one of the following: metal powder, metal-based compound powder, nitride ceramic powder, carbide ceramic powder, and oxide ceramic powder, which are used to block element diffusion reactions and have chemical stability.
4. The preparation method according to claim 1, characterized in that, The sintering process is induction sintering, hot pressing sintering, or spark plasma sintering.
5. The preparation method according to claim 1, characterized in that, The metal foam material is at least one of the following: transition metal foam material, light metal foam material, transition metal alloy foam material, and light metal alloy foam material, which have stable properties under medium and high temperature conditions.
6. The preparation method according to claim 1, characterized in that, The porosity of the foam connecting layer is 20% to 80%.
7. The preparation method according to claim 1, characterized in that, The welding in step S3 is at least one of diffusion welding, brazing, and metal-based solder welding, wherein the solder used for welding is at least one of tin-based solder, lead-based solder, copper-based solder, and silver-based solder; the welding at the high-temperature end in step S4 is performed by diffusion welding, brazing, or metal-based solder welding, wherein the solder used is at least one of tin-based solder, lead-based solder, copper-based solder, and silver-based solder.
8. The preparation method according to claim 1 or 7, characterized in that, It also includes surface modification treatment of the surface of the metal foam material before step S3, which involves electroplating, chemical plating, or spraying. The plating material used for electroplating, chemical plating, or spraying is at least one of a metal and its compound that can produce a wetting effect with the solder used in the welding in step S3 and the solder used in the high-temperature end welding in step S4.
9. A high-reliability thermoelectric device incorporating a foam bonding layer, characterized in that, It is prepared by the preparation method according to any one of claims 1-8.
10. The high-reliability thermoelectric device with a foam bonding layer according to claim 9, characterized in that, The high-reliability thermoelectric device is a medium-high temperature thermoelectric power generation module with a working hot end temperature of not less than 700K.