Thermoelectric element without metal electrode, device and preparation method thereof

Abstract

The invention discloses a thermoelectric element without a metal electrode, a device and a preparation method thereof, and belongs to the technical field of thermoelectric devices. The thermoelectric element is composed of a P-type thermoelectric arm, a barrier layer and an N-type thermoelectric arm, the barrier layer is arranged between the P-type thermoelectric arm and the N-type thermoelectric arm, connection and electron transmission between the P-type thermoelectric arm and the N-type thermoelectric arm are achieved through the barrier layer, effective separation of components of the P-type thermoelectric arm and the N-type thermoelectric arm is achieved, and meanwhile, the thermal conductivity of the thermoelectric element is improved. As the two sides of the barrier layer are integrally connected with the P-type thermoelectric arm and the N-type thermoelectric arm respectively, the stress problem caused by welding is avoided, and the interface performance and the stability of the thermoelectric element are improved. The process is free of a metal electrode layer, interface resistance and stress can be reduced, performance and reliability of the thermoelectric device are improved, the thermoelectric device prepared by the method shows excellent stability in a high-temperature cycle test, and an innovative solution is provided for high-temperature lossless connection of the thermoelectric device.

Description

Technical Field

[0001] The invention belongs to the technical field of thermoelectric devices and relates to a thermoelectric element without metal electrodes, a device and a preparation method thereof. Background Art

[0002] Based on the Seebeck effect, thermoelectric devices can directly convert thermal energy into electrical energy. They have the advantages of compact structure, high reliability and vibration-free operation, so they show broad prospects in the field of power generation applications. At present, PbTe materials in the medium and high temperature fields have become the focus of research due to their excellent thermoelectric properties. The development and promotion of PbTe thermoelectric devices can not only improve energy utilization efficiency, but also have important strategic significance for promoting the development of key energy application technologies.

[0003] The key to the preparation of thermoelectric devices lies in the construction of the barrier layer and the optimization of the welding process. The barrier layer needs to be in direct contact with the thermoelectric material, so the thermoelectric material must have good chemical stability. In addition, to ensure a strong bond between the barrier layer and the thermoelectric material, its thermal expansion coefficient and work function should match those of the thermoelectric material. This matching not only helps to reduce the interface resistance, but also effectively improves the output performance of the module and the stability of long-term operation.

[0004] At present, the specific steps of the method for constructing the barrier layer are to first select suitable barrier layer materials for the P-type and N-type thermoelectric legs, and sinter them together with the thermoelectric material to form a thermoelectric element with an integrated barrier layer. Welding is the process of connecting the P-type and N-type thermoelectric elements with electrodes to form a ᴨ-type module. This process is prone to cause thermal stress in thermoelectric devices during high-temperature operation. The high-temperature welded joint is the weak point of the module. Therefore, choosing the right method to prepare the device is a difficult problem in the development process of PeTe from materials to devices. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art and provide a thermoelectric element, device and preparation method thereof without metal electrodes, so as to solve the problem that the weak points caused by high-temperature welding mentioned in the above-mentioned background technology easily lead to thermal stress in the thermoelectric device during high-temperature operation.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions: A thermoelectric element without metal electrodes, comprising: The P-type thermoelectric arm is a columnar structure; The N-type thermoelectric arm has the same structure as the P-type thermoelectric arm, and has the same height, cross-sectional shape and cross-sectional size as the P-type thermoelectric arm; A barrier layer is provided between the P-type thermoelectric arm and the N-type thermoelectric arm; The upper end of the barrier layer, the upper end of the P-type thermoelectric arm and the upper end of the N-type thermoelectric arm are aligned horizontally; the two sides of the barrier layer, the two sides of the P-type thermoelectric arm and the two sides of the N-type thermoelectric arm are aligned vertically, and the height of the barrier layer is less than the height of the P-type thermoelectric arm; One side of the blocking layer is integrally connected to the side of the P-type thermoelectric arm, and the other side of the blocking layer is integrally connected to the side of the N-type thermoelectric arm; the blocking layer is used to propagate electrons between the P-type thermoelectric arm and the N-type thermoelectric arm, and the blocking layer is used to block the elements of the P-type thermoelectric arm from diffusing to the N-type thermoelectric arm, and block the elements of the N-type thermoelectric arm from diffusing to the P-type thermoelectric arm.

[0007] A further improvement of the present invention is: Preferably, the difference between the thermal expansion coefficients of the P-type thermoelectric arm material, the barrier layer material and the N-type thermoelectric arm material is in the range of 5% to 10%.

[0008] Preferably, the barrier layer is composed of a first barrier layer and a second barrier layer, the first barrier layer and the second barrier layer are integrally connected, the first barrier layer is arranged between the second barrier layer and the P-type thermoelectric arm, and the second barrier layer is arranged between the first barrier layer and the N-type thermoelectric arm; The first barrier layer is used to block the diffusion of elements of the P-type thermoelectric arm, and the second barrier layer is used to block the diffusion of elements of the N-type thermoelectric arm.

[0009] Preferably, the integral connection is a connection through mutual diffusion between elements.

[0010] Preferably, the P-type thermoelectric arm is P-type PbTe, the N-type thermoelectric arm is N-type PbTe, the first barrier layer is SnTe, and the second barrier layer is FeSb.

[0011] Preferably, the P-type PbTe is Pb 0.98 Na 0.02 Te, the N-type PbTe is Pb 0.9 Ge 0.1 Te 0.996 I 0.004 .

[0012] A method for preparing the above-mentioned thermoelectric element without metal electrodes comprises the following steps: Step 1, stacking the corresponding powders in a sintering mold in the order of a P-type thermoelectric arm, a barrier layer, and an N-type thermoelectric arm, or in the order of an N-type thermoelectric arm, a barrier layer, and a P-type thermoelectric arm; Step 2, sintering according to set sintering parameters to obtain a sintered block; the sintered block is composed of a P-type thermoelectric arm, a barrier layer and an N-type thermoelectric arm which are integrally connected in sequence from one end to the other end; Step 3, cutting the sintered block into tetrahedral blocks; Step 4, according to the set size of the thermoelectric element, cutting inward from one side of the tetrahedral block along the height direction of the tetrahedral block, removing part of the blocking layer in the height direction, and forming a process thermoelectric element; Step 5, cutting the process thermoelectric element along the height direction of the square block according to the set size of the thermoelectric element, wherein the cutting direction is perpendicular to the length direction of the process thermoelectric device, to form N PbTe thermoelectric elements, wherein N is a natural number ≥1.

[0013] Preferably, in step 3 and step 4, cutting is performed by wire electric discharge cutting technology.

[0014] A method for preparing a thermoelectric device comprises tinning the bottom of a P-type thermoelectric arm and the bottom of an N-type thermoelectric arm in the thermoelectric element, and welding a plurality of tinned thermoelectric elements on a copper plate according to set positions to obtain a thermoelectric device.

[0015] A thermoelectric device manufactured by the above manufacturing method comprises a copper plate on which a plurality of thermoelectric elements are arrayed.

[0016] Compared with the prior art, the present invention has the following beneficial effects: The invention discloses a thermoelectric element without metal electrodes, which consists of a P-type thermoelectric arm, a barrier layer and an N-type thermoelectric arm. The element of the invention sets a barrier layer between the P-type thermoelectric arm and the N-type thermoelectric arm, and the barrier layer realizes the mechanical connection and electron transmission between the P-type thermoelectric arm and the N-type thermoelectric arm, and can realize the effective separation of the components of the P-type thermoelectric arm and the N-type thermoelectric arm, because the two sides of the barrier layer are respectively connected to the P-type thermoelectric arm and the N-type thermoelectric arm as a whole, avoiding the stress problem formed by welding, and improving the interface performance and stability of the thermoelectric element. This process has no metal electrode layer, significantly reduces the interface resistance and stress, and improves the performance and reliability of the thermoelectric device. The thermoelectric device prepared by this method shows excellent stability in high-temperature cycle tests, providing an innovative solution for high-temperature lossless connection of thermoelectric devices.

[0017] Furthermore, the present invention discloses a P-type thermoelectric arm material, a barrier layer material and an N-type thermoelectric arm material. Both the P-type thermoelectric arm material and the N-type thermoelectric arm material are PbTe material powders, and the diffusion layer is composed of two alloys, SnTe and FeSb. SnTe can achieve good combination with P-type PbTe and significantly reduce the migration of other elements to P-type PbTe; while FeSb has no significant diffusion after combining with N-type PbTe, which can achieve effective separation of P-type and N-type thermoelectric arm components. Therefore, SnTe and FeSb are used as two adjacent barrier layer materials. The structure of the present invention has no difference in thermodynamic properties of metal electrodes at the interface of PbTe thermoelectric elements without metal electrodes, and avoids thermal shock caused by high-temperature welding.

[0018] The present invention also discloses a method for preparing a thermoelectric element without metal electrodes, wherein the preparation method uses an induction hot pressing device to sinter P-type and N-type PbTe materials and barrier layer materials into blocks, and cuts them into U-type thermoelectric elements. Through induction hot pressing sintering, it is possible to form a structure that ensures that the P-type thermoelectric arm and the barrier layer, as well as the barrier layer and the N-type thermoelectric arm can be diffusely connected to each other as a whole, thereby improving the strength of the connection interface and avoiding stress at the connection interface. The stress distribution of U-shaped and conventional Π-shaped particles is simulated and analyzed under the conditions of Tc = 300 K and Th = 850K. It can be observed that the stress in the U-shaped particles is mainly concentrated at the connection between the P-type and N-type legs. The stress in the U-shaped particles is significantly lower than that in the Π-shaped particles, indicating that co-sintering is an effective method for improving the output performance and reliability of thermoelectric devices, and the high temperature end of the obtained PbTe thermoelectric device has low resistance and high stability.

[0019] The invention also discloses a thermoelectric device without metal electrodes. The thermoelectric device is obtained by soldering the above-mentioned thermoelectric element on a copper plate after tinning, so that the thermoelectric device has low resistance characteristics at the high temperature end and high stability. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0021] Figure 1 This is a process flow chart of connecting a PbTe thermoelectric device without metal electrodes according to the present invention; Figure 2 This is a specific physical photo of the PbTe thermoelectric device without metal electrodes prepared by the present invention; Figure 3 The results of the effects of different thicknesses of P-type PbTe / SnTe-FeSb / N-type PbTe layers on device output performance in the embodiment are shown; Among them, Figure a is the open circuit voltage, Figure b is the internal resistance, Figure c is the output power, Figure d is the heat flow, Figure e is the conversion efficiency, and Figure f is a summary of the device output power and conversion efficiency using different interface thicknesses n.

[0022] Figure 4 The SEM images of the interface element distribution of the P-type PbTe / SnTe-FeSb / N-type PbTe layer and the test results of its interface resistivity in the embodiment are shown; Among them, Figure a is a physical picture; Figure b is a SEM picture; Figure c is the interface resistance; Figure d is a comparison of the interface resistance of different barrier layers Figure 5is the thermal cycle test result of the PbTe thermoelectric device without metal electrodes prepared in the embodiment of the present invention; Among them, Figure a is the open circuit voltage, Figure b is the internal resistance, Figure c is the output power, and Figure d is the conversion efficiency; Figure 6 The thermal stress simulation results of the U-shaped module and the Π-shaped module in the embodiments of the present invention are shown.

[0023] Figure a is the simulated stress distribution diagram; Figure b is the average stress of devices with different structures; DETAILED DESCRIPTION The present invention is further described in detail below in conjunction with the accompanying drawings: In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

[0024] In this document, unless otherwise specified, “includes,” “including,” “contains,” “has,” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0025] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0026] The following examples use conventional instruments and equipment in the art. The experimental methods in the following examples where specific conditions are not specified are usually carried out under conventional conditions or under conditions recommended by the manufacturer. The various raw materials used in the following examples are conventional commercial products unless otherwise specified, and their specifications are conventional specifications in the art. In the specification of the present invention and the following examples, unless otherwise specified, "%" means weight percentage, "part" means weight part, and ratio means weight ratio.

[0027] The first aspect of the present invention discloses a thermoelectric element without metal electrodes, comprising a P-type thermoelectric arm, an N-type thermoelectric arm and a barrier layer; the P-type thermoelectric arm is a columnar structure; the N-type thermoelectric arm has the same structure as the P-type thermoelectric arm, and has the same height, cross-sectional shape and cross-sectional size as the P-type thermoelectric arm; the barrier layer is arranged between the P-type thermoelectric arm and the N-type thermoelectric arm; the upper end of the barrier layer, the upper end of the P-type thermoelectric arm and the upper end of the N-type thermoelectric arm are horizontally flush; the two sides of the barrier layer, the two sides of the P-type thermoelectric arm and the two sides of the N-type thermoelectric arm are vertically flush, and the height of the barrier layer is less than the height of the P-type thermoelectric arm; one side of the barrier layer is integrally connected to the side of the P-type thermoelectric arm, and the other side of the barrier layer is integrally connected to the side of the N-type thermoelectric arm, the barrier layer can propagate electrons between the P-type thermoelectric arm and the N-type thermoelectric arm, and the barrier layer is used to block the elements of the P-type thermoelectric arm from diffusing to the N-type thermoelectric arm, and block the elements of the N-type thermoelectric arm from diffusing to the P-type thermoelectric arm.

[0028] The P-type thermoelectric arm, N-type thermoelectric arm and barrier layer of the above structure form a U-shaped thermoelectric element, which transfers the transmission electron part at the upper end of the original ᴨ-type thermoelectric element to between the P-type thermoelectric arm and the N-type thermoelectric arm, avoiding the welding process.

[0029] It should be understood that the above-mentioned N-type thermoelectric arm and P-type thermoelectric arm are the common N-type legs and P-type legs, whose basic structure is a columnar structure, and the cross-sectional shape can be adjusted according to actual needs, such as rectangular, square or circular, and the size can be adjusted and designed according to actual conditions.

[0030] In some embodiments of the present invention, the difference in thermal expansion coefficients between the P-type thermoelectric arm material, the barrier layer material and the N-type thermoelectric arm material is in the range of 5% to 10%. The difference in thermal expansion coefficients is within a certain range, so that when working as a thermoelectric material, defects caused by excessive differences in expansion coefficients between materials can be avoided. Preferably, the smaller the difference in thermal expansion coefficients, the better.

[0031] The main function of the barrier layer is to propagate electrons between the P-type thermoelectric arm and the N-type thermoelectric arm, and at the same time to block the P-type thermoelectric arm and the N-type thermoelectric arm. The blocking method is to limit the diffusion of elements in the two layers. However, in actual operation, it is difficult to select the same material that can simultaneously satisfy the propagation of electrons and have a blocking effect on the elements of the two layers. Therefore, in some embodiments of the present invention, the barrier layer is composed of a first barrier layer and a second barrier layer, wherein the first barrier layer and the second barrier layer have the same thickness, the first barrier layer and the second barrier layer are integrally connected, the first barrier layer is arranged between the second barrier layer and the P-type thermoelectric arm, and the second barrier layer is arranged between the first barrier layer and the N-type thermoelectric arm. The first barrier layer is used to block the diffusion of elements in the P-type thermoelectric arm, and the second barrier layer is used to block the diffusion of elements in the N-type thermoelectric arm. This scheme combines the barrier effect through two materials with good conductivity, so that the conductive and barrier effects can be satisfied at the same time. When selecting materials, this scheme also needs to ensure that the connectivity between the first barrier layer and the second barrier layer materials is good, that is, through the subsequent sintering process, the two can achieve a firm connection relationship through mutual diffusion between elements.

[0032] In some embodiments of the present invention, the above-mentioned integrated connection is connected by mutual diffusion between elements, that is, the two types of materials on both sides of the connection interface form a connection relationship by mutual diffusion between each other, and a similar "transition layer" is formed at the connection interface. The transition layer will include all elements on both sides of the connection interface. Through this method, the connection force at the connection interface is strong and there is no stress concentration phenomenon. It should be understood that in the above-mentioned U-type thermoelectric element with two barrier layers, there are three "transition layers", namely, the P-type thermoelectric arm and the first barrier layer, the first barrier layer and the second barrier layer, and the second barrier layer and the third barrier layer.

[0033] It should be understood that the first barrier layer of the present invention can cause a small amount of mutual diffusion of elements with the P-type layer to achieve diffusion connection, but it can also prevent the elements of the P-type layer from further diffusing into the second barrier layer, thus playing a blocking role. The same applies to the second barrier layer and the N-type layer.

[0034] It should be understood that the dimensions of the above-mentioned barrier layer, including the vertical cross-sectional dimensions and thickness, are adjusted according to actual conditions, and resistance, mechanical strength, power and efficiency must be comprehensively considered, wherein the resistance is desired to be as low as possible, the mechanical strength is desired to be as high as possible, and the power and efficiency must be able to meet the requirements of the thermoelectric element.

[0035] In some specific embodiments of the present invention, the thermoelectric element is a PbTe-based lossless connection thermoelectric element. The P-type thermoelectric arm is P-type PbTe, the N-type thermoelectric arm is N-type PbTe, the first barrier layer is SnTe, and the second barrier layer is FeSb. The barrier layer contains four elements: Sn, Te, Fe and Sb.

[0036] It should be understood that in other embodiments, PbTe powder can be replaced by other types of thermoelectric material powders, and lossless connection thermoelectric devices with similar structures can also be prepared and achieve the same substantial effects. Therefore, these alternatives should also be included in the protection scope of the present invention.

[0037] Furthermore, the P-type PbTe is Pb 0.98 Na 0.02 Te, the N-type PbTe is Pb 0.9 Ge 0.1 Te 0.996 I 0.004 .

[0038] The second aspect of the present invention discloses a method for preparing a PbTe thermoelectric device without a metal electrode, the method comprising the following steps: Step 1, stacking the corresponding powders in a sintering mold in the order of a P-type thermoelectric arm, a barrier layer, and an N-type thermoelectric arm, or in the order of an N-type thermoelectric arm, a barrier layer, and a P-type thermoelectric arm; Step 2, sintering according to set sintering parameters to obtain a sintered block; the sintered block is composed of a P-type thermoelectric arm, a barrier layer and an N-type thermoelectric arm which are integrally connected in sequence from one end to the other end; Step 3, cutting the sintered block into tetrahedral blocks; Step 4, according to the set size of the thermoelectric element, cutting inward from one side of the tetrahedral block along the height direction of the tetrahedral block, removing part of the blocking layer in the height direction, and forming a process thermoelectric element; Step 5, cutting the process thermoelectric element along the height direction of the square block according to the set size of the thermoelectric element, wherein the cutting direction is perpendicular to the length direction of the process thermoelectric device, to form N PbTe thermoelectric elements, wherein N is a natural number ≥1.

[0039] A specific embodiment of the present invention discloses a method for preparing a PbTe-based thermoelectric element, comprising the following steps: Step 1, preparing sintering powder, including preparing PbTe-based thermoelectric powder, preparing SnTe, FeSb barrier layer powder; Step 2, the step of preparing square sintered blocks, placing PbTe-based thermoelectric powder and SnTe, FeSb barrier layer powders in a sintering mold according to P-type PbTe / SnTe / FeSb / N-type PbTe, obtaining sintered blocks under set pressure, set temperature and set insulation time, and cutting them into cubic blocks by electric spark cutting.

[0040] Step 3: prepare a U-shaped thermoelectric element and cut it into a plurality of U-shaped thermoelectric elements by electric spark cutting.

[0041] Preferably, the sintered abrasive tool is a graphite abrasive tool. Graphite molds have high stability, can withstand high temperature and high pressure, meet the requirements of the sintering process, and do not react with the sintering powder, thereby ensuring the smooth progress of the sintering process and ensuring the structural integrity and performance stability of the sintered material.

[0042] Preferably, the set oil pressure is 60 MPa, the temperature is 853 K, and the holding time is 15-20 minutes. These parameters can be appropriately adjusted according to the composition and thickness of the barrier layer, and are not limited to the above set values, to meet different material systems and performance requirements.

[0043] Preferably, the size of the square block is 10 mm × 20 mm, and the size of the U-shaped thermoelectric element is 3.5 mm × 3.5 mm × 10 mm.

[0044] The present invention also discloses a method for preparing a thermoelectric device, wherein the bottom of the P-type thermoelectric arm and the bottom of the N-type thermoelectric arm in the thermoelectric element are tinned, and a plurality of tinned thermoelectric elements are welded on a copper plate according to a set position to obtain a thermoelectric device. Through the tinning operation, the thermoelectric element can be welded on the copper plate to prepare the thermoelectric device.

[0045] In a specific embodiment, after the tetrahedral block is prepared as described above, a tinning operation can be performed, that is, the bottom of the entire tetrahedral block is tinned, simplifying the entire tinning process. After the tinning operation, subsequent cutting operations can be performed.

[0046] The present invention also discloses a thermoelectric device, which consists of a copper plate and PbTe thermoelectric devices arranged on a low-temperature copper-clad plate. U-shaped thermoelectric elements are welded to the low-temperature copper-clad plate in a specific arrangement sequence to assemble the thermoelectric device.

[0047] It should be understood that the location and number of the U-shaped thermoelectric elements on the thermoelectric device are adjusted according to actual conditions.

[0048] The following is further described in conjunction with specific embodiments: Example 1 like Figure 1FIG. 1 is a flow chart of a connection process of a PbTe thermoelectric device without a metal electrode according to the present invention. The process includes the following steps: Step 1, placing PbTe-based thermoelectric powder and SnTe, FeSb diffusion barrier layer powders according to P-type PbTe / SnTe / FeSb / N-type PbTe on a sintering mold and sintering them into a block; Step 2, cutting the sintered block into square blocks with a size of 10 mm × 20 mm; Step 3, tinning the bottom of the square block to obtain a square block with tinned bottom; Step 4, cutting the square block obtained in step 3 from the tin-plated end inward to remove part of SnTe and FeSb therein; Step 5, cutting the square block obtained in step 4 into a plurality of U-shaped thermoelectric elements with a size of 3.5 mm × 3.5 mm × 10 mm; Step 6, finally, the obtained U-shaped thermoelectric element is welded on the copper plate through the tinned end, assembled into a device, and the preparation of the entire thermoelectric device is completed.

[0049] In this embodiment, the process parameters specifically set during the co-sintering process include a temperature of 823 K, a pressure of 60 MPa, and a heat and pressure holding time of 15 minutes.

[0050] The PbTe thermoelectric powder layer and the barrier layer are co-sintered into a block using an induction sintering method, cut into squares and electroplated with tin on one end surface, and the square blocks are prepared into a plurality of U-shaped thermoelectric elements to form a PbTe-based lossless connection thermoelectric device. like Figure 2 The figure shows a PbTe thermoelectric device without metal electrodes prepared by co-sintering, using the connection method of P-type powder / diffusion layer / N-type powder. This method does not require high-temperature terminal electrodes, thereby ensuring a strong bond between the barrier layer and the thermoelectric material.

[0051] like Figure 3 As shown, the relationship between the thickness of the connection layer and the performance of the thermoelectric device is studied. According to the method of the above embodiment, the thickness of the barrier layer SnTe / FeSb in the mold is adjusted, and the thickness of the barrier layer SnTe and the barrier layer FeSb are equal. The research results show that different connection layer thicknesses have a significant impact on the conversion efficiency and output power of the thermoelectric device, and there are differences in the optimal connection layer thickness corresponding to different performance indicators.

[0052] like Figure 4, which is a schematic diagram of the content of each element at the interface of the P-type PbTe / SnTe-FeSb / N-type PbTe layer when n=3.5 mm in an embodiment of the present invention. The results show that the element distribution between the PbTe, FeSb, and SnTe layers presents a clear boundary. This indicates that FeSb is chemically inert to N-type PbTe, SnTe is chemically inert to P-type PbTe, and FeSb is also chemically inert to SnTe.

[0053] like Figure 5 As shown in Figure 1, the results of the cycle test of the PbTe thermoelectric device without metal electrodes when n=3.5 mm prepared in the embodiment of the present invention was connected under the condition of high temperature end temperature of 593 K-793 K. The test results show that after 20 thermal cycles, the device performance did not change significantly, showing its excellent stability and reliability.

[0054] like Figure 6 The figure shows the stress simulation of the U-type and Π-type modules when n=3.5mm in the embodiment of the present invention; the stress distribution of the U-type and Π-type modules under the conditions of Tc=300K and Th=850K is analyzed, and the thermal stress difference between the two connection methods is analyzed. Figure 6 It can be observed that the stress in the U-shaped module is mainly concentrated in the connection of the P-type and N-type legs. The stress in the U-shaped legs is significantly lower than that in the Π-shaped module, and the stress between the P-type and N-type thermoelectric arms in the U-shaped thermoelectric pair is very similar. In the U-shaped module, there are only three connection joints between the P-type and N-type thermoelectric arms: P-type PbTe / SnTe, SnTe / FeSb, FeSb / N-type PbTe. In contrast, the Π-type module has five interfaces: P-type PbTe / SnTe, SnTe / FeSb, FeSb / Cu, Cu / FeSb, FeSb / N-type PbTe. In addition, the mechanical properties of SnTe and FeSb are very similar to those of PbTe, which also helps to reduce the thermal stress in the U-shaped module. Lower thermal stress leads to higher thermal stability of the U-shaped module.

[0055] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A thermoelectric element without metal electrodes, characterized in that: include: The P-type thermoelectric arm is a columnar structure; The N-type thermoelectric arm has the same structure as the P-type thermoelectric arm, and has the same height, cross-sectional shape and cross-sectional size as the P-type thermoelectric arm; A barrier layer is provided between the P-type thermoelectric arm and the N-type thermoelectric arm; The upper end of the barrier layer, the upper end of the P-type thermoelectric arm and the upper end of the N-type thermoelectric arm are aligned horizontally; the two sides of the barrier layer, the two sides of the P-type thermoelectric arm and the two sides of the N-type thermoelectric arm are aligned vertically, and the height of the barrier layer is less than the height of the P-type thermoelectric arm; One side of the blocking layer is integrally connected to the side of the P-type thermoelectric arm, and the other side of the blocking layer is integrally connected to the side of the N-type thermoelectric arm; the blocking layer is used to propagate electrons between the P-type thermoelectric arm and the N-type thermoelectric arm, and the blocking layer is used to block the elements of the P-type thermoelectric arm from diffusing to the N-type thermoelectric arm, and block the elements of the N-type thermoelectric arm from diffusing to the P-type thermoelectric arm.

2. A thermoelectric element without metal electrodes according to claim 1, characterized in that: The difference between the thermal expansion coefficients of the P-type thermoelectric arm material, the barrier layer material and the N-type thermoelectric arm material ranges from 5% to 10%.

3. The thermoelectric element without metal electrodes according to claim 1, characterized in that: The barrier layer is composed of a first barrier layer and a second barrier layer, the first barrier layer and the second barrier layer are integrally connected, the first barrier layer is arranged between the second barrier layer and the P-type thermoelectric arm, and the second barrier layer is arranged between the first barrier layer and the N-type thermoelectric arm; The first blocking layer is used to block the diffusion of elements of the P-type thermoelectric arm, and the second blocking layer is used to block the diffusion of elements of the N-type thermoelectric arm.

4. A thermoelectric element without metal electrodes according to claim 3, characterized in that: The integral connection is a connection through mutual diffusion between elements.

5. The thermoelectric element without metal electrodes according to claim 3, characterized in that: The P-type thermoelectric arm is P-type PbTe, the N-type thermoelectric arm is N-type PbTe, the first barrier layer is SnTe, and the second barrier layer is FeSb.

6. A thermoelectric element without metal electrodes according to claim 5, characterized in that: The P-type PbTe is Pb 0.98 Na 0.02 Te, the N-type PbTe is Pb 0.9 Ge 0.1 Te 0.996 I 0.004 .

7. A method for preparing a thermoelectric element without metal electrodes according to claim 1, characterized in that: The following steps are involved: Step 1, stacking the corresponding powders in a sintering mold in the order of a P-type thermoelectric arm, a barrier layer, and an N-type thermoelectric arm, or in the order of an N-type thermoelectric arm, a barrier layer, and a P-type thermoelectric arm; Step 2, sintering according to set sintering parameters to obtain a sintered block; the sintered block is composed of a P-type thermoelectric arm, a barrier layer and an N-type thermoelectric arm which are integrally connected in sequence from one end to the other end; Step 3, cutting the sintered block into tetrahedral blocks; Step 4, according to the set size of the thermoelectric element, cutting inward from one side of the tetrahedral block along the height direction of the tetrahedral block, removing part of the blocking layer in the height direction, and forming a process thermoelectric element; Step 5, cutting the process thermoelectric element along the height direction of the square block according to the set size of the thermoelectric element, the cutting direction is perpendicular to the length direction of the process thermoelectric device, to form N PbTe thermoelectric elements, wherein N is a natural number ≥1.

8. The preparation method according to claim 7, characterized in that: In step 3 and step 4, cutting is performed by wire electric discharge cutting technology.

9. A method for preparing a thermoelectric device, characterized in that: The bottom of the P-type thermoelectric arm and the bottom of the N-type thermoelectric arm in the thermoelectric element according to claim 1 are tinned, and a plurality of tinned thermoelectric elements are welded on a copper plate according to set positions to obtain a thermoelectric device.

10. A thermoelectric device prepared by the preparation method according to claim 9, characterized in that: The invention comprises a copper plate on which a plurality of thermoelectric elements are arrayed.

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