A skutterudite thermoelectric component and its preparation method and application

Abstract

The present invention relates to the technical field of thermoelectric components, and specifically discloses a skutterudite thermoelectric component and its preparation method and application. The present invention develops two different types of anti-diffusion layer alloy compositions for N-type and P-type thermoelectric materials in thermoelectric components, respectively, so that their linear expansion coefficients match those of N-type and P-type thermoelectric materials, respectively, to reduce the thermal stress of the interface, thereby improving the reliability and service life of the thermoelectric device. Among them, the anti-diffusion layer composition for N-type thermoelectric material is Fe a Cr b V c , the composition of the anti-diffusion layer for P-type thermoelectric materials is Fe a’ Cr b’ Si c’ ; Wherein, a, b, c, a', b', c' represent the mass percentage of each component, a+b+c=100, a'+b'+c'=100; 70≤a≤90, 10≤b≤20, 0<c≤10; 70≤a'≤90, 10≤b'≤20, 0<c'≤10; a and a', b and b', c and c' may be the same or different.

Description

Technical Field

[0001] The present invention relates to the technical field of thermoelectric components, and in particular to a skutterudite thermoelectric component and a preparation method and application thereof. Background Art

[0002] The shortage of fossil energy and environmental pollution are receiving increasing attention. Diversification and efficient multi-level utilization of energy provide an important technical approach to systematically addressing energy and environmental issues. Thermoelectric materials are materials that can convert heat and electricity into each other using the Seebeck effect. Due to their advantages of no moving parts, no emissions, simple structure, and environmental friendliness, they have broad application prospects in aerospace power generation, the reuse of waste heat from automobile exhaust, and geothermal energy. The conversion efficiency of thermoelectric materials is determined by the thermoelectric figure of merit, ZT. ZT = S 2 σT / κ. Where S is the Seebeck coefficient, σ is the electrical conductivity, T is the temperature, and κ is the thermal conductivity. A larger ZT value indicates a greater energy conversion efficiency and Carnot efficiency of the material, and better thermoelectric conversion performance.

[0003] Skutterudite-based thermoelectric materials are widely studied for medium- and high-temperature applications, with operating temperatures reaching up to 600°C. Both P-type and N-type thermoelectric materials, achieved through doping or filling with large atomic elements and composition optimization, can achieve ZT values ​​exceeding 1.0. However, in thermoelectric devices with long-term service, element diffusion or chemical reactions are prone to occur at the interface between the high-temperature terminal electrode and the thermoelectric material, leading to changes in the interface composition and structure, additional interfacial resistance and thermal resistance, and consequently, device performance degradation or even failure. Therefore, it is necessary to introduce an anti-diffusion layer between the thermoelectric material and the electrode to ensure a good connection and high-temperature interface stability. The design and selection of an anti-diffusion layer typically require considerations: ensuring a good connection between the thermoelectric material and the electrode, maintaining a certain bond strength at operating temperatures; forming a stable interface layer that prevents interdiffusion and chemical reactions between the thermoelectric material and the electrode at high temperatures; and ensuring the anti-diffusion layer itself has low electrical and thermal resistance.

[0004] The prior art has disclosed the use of metals such as Ti and Al as anti-diffusion layers for thermoelectric devices. However, due to the high ambient temperature in which skutterudite thermoelectric devices are used, the thermal expansion coefficients of metals such as Ti and Al differ significantly from those of skutterudite thermoelectric materials and electrodes, leading to interfacial cracking during long-term use at high temperatures. On the other hand, P-type and N-type materials of different components also have different thermal expansion coefficients at high temperatures, and the prior art has not fully considered the need for P-type and N-type materials to match different types of anti-diffusion layer components, further increasing the risk of a short service life of thermoelectric devices due to interfacial cracking during high-temperature use. Summary of the Invention

[0005] In order to solve the problems existing in the prior art, the purpose of the present invention is to provide a skutterudite thermoelectric component and its preparation method and application. In view of the different material components used at the N-end and P-end of the skutterudite thermoelectric material, anti-diffusion layers of different components are used at both ends to achieve a better fit for the thermal expansion coefficient of the thermoelectric material, so that cracking will not occur between the anti-diffusion layer and the thermoelectric material during medium and high temperature applications.

[0006] In order to achieve the purpose of the present invention, the technical solution of the present invention is as follows:

[0007] In a first aspect, the present invention provides a skutterudite thermoelectric component, wherein the skutterudite thermoelectric component is a thermoelectric pair consisting of an N-type structure and a P-type structure;

[0008] The N-type structure includes an N-type thermoelectric material and an N-type anti-diffusion layer, and the P-type structure includes a P-type thermoelectric material and a P-type anti-diffusion layer;

[0009] The components of the N-type thermoelectric material include Sb, Co, Fe, and Yb, and the components of the P-type thermoelectric material include Sb, Co, Fe, and La;

[0010] The component of the N-type anti-diffusion layer is Fe a Cr b V c The component of the P-type diffusion barrier is Fe a’ Cr b’ Si c’ ; Wherein, a, b, c, a', b', c' represent the mass percentage of each component, a+b+c=100, a'+b'+c'=100; 70≤a≤90, 10≤b≤20, 0<c≤10; 70≤a'≤90, 10≤b'≤20, 0<c'≤10 (a and a', b and b', c and c' may be the same or different).

[0011] More preferably, in the components of the N-type anti-diffusion layer, 75≤a≤88, 12≤b≤18, 2≤c≤8; more preferably 78≤a≤85, 13≤b≤17, 3≤c≤7;

[0012] More preferably, the components of the N-type anti-diffusion layer are 75≤a≤80, 10≤b≤15, and 2≤c≤8; and the components of the P-type anti-diffusion layer are 70≤a'≤82, 15≤b'≤20, and 3≤c'≤10.

[0013] Furthermore, the N-type thermoelectric material is preferably Sb 12 Co 3.75 Fe 0.25 Yb 0.3 , the P-type thermoelectric material is preferably Sb 12CoFe3La 0.7 , where the number represents the number of atoms contained in a single unit cell of the alloy.

[0014] Furthermore, during the preparation of the skutterudite thermoelectric component, the N-type thermoelectric material and the P-type thermoelectric material react with the N-type anti-diffusion layer and the P-type anti-diffusion layer respectively to generate corresponding transition layers.

[0015] Furthermore, the thickness of the transition layer is at the μm level, and the thickness of the anti-diffusion layer is at the mm level.

[0016] Preferably, the thickness of the diffusion prevention layer is 0.1 to 2 mm, more preferably 0.5 to 1 mm.

[0017] In a second aspect, the present invention provides a method for preparing the aforementioned skutterudite thermoelectric component, the method comprising the following steps:

[0018] (1) Weigh and mix high-purity elemental raw materials according to the proportion of thermoelectric material components, and the purity of the elemental raw materials is above 99 at.%; put the weighed raw materials into a graphite tube and seal it in a vacuum of 3×10 -3 In a quartz tube below Pa;

[0019] (2) The sample sealed in the quartz tube was heat treated at a temperature of 1000-1200°C for 10-15 hours to melt and uniformly mix the materials, and then water quenched;

[0020] (3) heat treating the quenched sample at a temperature of 500-700°C for more than 50 hours;

[0021] (4) The ingot after heat treatment is taken out, impurities on the surface are polished off, and then it is crushed and ground into powder with a particle size of less than 200 μm;

[0022] (5) Thermoelectric material powder is loaded into a graphite mold, and diffusion-resistant alloy sheets corresponding to the material type are placed on both sides of the powder. Thermoelectric material blocks with diffusion-resistant layers on both ends are prepared by SPS sintering;

[0023] The SPS sintering conditions are as follows: heating rate of 50-100°C / min, sintering temperature of 600-750°C, holding time of 15-25min, and cooling rate of 10-30°C / min.

[0024] In a third aspect, the present invention provides a skutterudite thermoelectric device, comprising the thermoelectric component of the aforementioned solution of the present invention, and an electrode connecting the N-type end and the P-type end of the thermoelectric component.

[0025] Further preferably, the skutterudite thermoelectric device further comprises a nickel layer located between the electrode and the anti-diffusion layer of the thermoelectric component, and the thickness of the nickel layer is at the μm level.

[0026] In a fourth aspect, the present invention provides a method for preparing the skutterudite thermoelectric device, wherein the P-type and N-type thermoelectric components in the skutterudite thermoelectric component are connected to electrodes by vacuum brazing.

[0027] More specifically, the preparation method comprises the following steps:

[0028] (1) Cut the well-sintered P-type and N-type thermoelectric blocks into thermoelectric arms of certain sizes. Polish the upper and lower end surfaces of the electrodes, N-type thermoelectric arms, and P-type thermoelectric arms with 600M sandpaper to remove the surface oxide layer. Then, clean them with anhydrous ethanol ultrasonic cleaning and dry them.

[0029] (2) Place the electrode-silver-based solder-thermoelectric arm-silver-based solder-electrode on the graphite mold in sequence, and then fix it with a pressing plate;

[0030] (3) Place the assembled mold in a vacuum brazing furnace, set the welding temperature to 670°C, keep warm for 10 minutes, and set the pressure to 2 MPa, and cool it with the furnace.

[0031] Unless otherwise specified, the percentages mentioned in the present invention are by mass; the raw materials or reagents involved are common commercially available products, and the operations involved are routine operations in the art unless otherwise specified.

[0032] On the basis of conforming to the common sense in this field, the above-mentioned preferred conditions can be combined with each other to obtain a specific implementation method.

[0033] The beneficial effects of the present invention are:

[0034] The present invention first addresses the problem that the existing technology does not consider the matching of linear expansion coefficients between different types (N, P) of thermoelectric materials and anti-diffusion layers. Two different types of anti-diffusion layers are developed for N-type thermoelectric materials and P-type thermoelectric materials, respectively, so that their linear expansion coefficients match those of N-type and P-type thermoelectric materials, respectively. This can reduce the thermal stress at the interface and thereby improve the reliability and service life of the thermoelectric device.

[0035] The thermal expansion coefficient of the Fe element in the diffusion barrier is 12×10 -6 / K, and Co3Sb (10~11)×10 -6 / K is close. Using FeCr alloy as the base alloy, the thermoelectric material and the anti-diffusion layer can form a stable transition layer containing Fe, Cr, and Sb after long-term aging, which can provide an effective barrier. FeCr alloy also has strong corrosion resistance and low cost. In addition, due to the differences in the types and contents of elements in the components of N- and P-type thermoelectric materials, their thermal expansion coefficients differ. Therefore, V is added to the anti-diffusion layer on the N-type end, and Si is added to the anti-diffusion layer on the P-type end, respectively, to achieve a better match between the linear expansion coefficients of the anti-diffusion layer and the corresponding thermoelectric material.

[0036] Furthermore, the present invention introduces a μm-level nickel layer between the electrode and the thermoelectric component, so that nickel, solder (containing silver), and electrode (containing copper) form a nickel-silver-copper alloy during the welding process, achieving a stronger connection.

[0037] Furthermore, the present invention prepares thermoelectric devices by connecting the diffusion prevention layer and the electrodes through vacuum brazing. Compared with the conventional technology of sintering the thermoelectric devices as a whole, this method reduces the preparation time, reduces the equipment cost, facilitates the overall preparation of large-volume thermoelectric devices, and is more suitable for mass production. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present disclosure and, together with the description, serve to explain the principles of the present disclosure.

[0039] In order to more clearly illustrate the embodiments of the present disclosure or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0040] Figure 1 Schematic diagram of the structure of the thermoelectric device of the present invention; wherein 1 is an N-type structure, 11 is an N-type thermoelectric material, 12 is an N-type anti-diffusion layer, 2 is a P-type structure, 21 is a P-type thermoelectric material, 22 is a P-type anti-diffusion layer, 3 is an electrode, and 4 is a nickel layer.

[0041] Figure 2 The curves of thermal expansion coefficients of N-type and P-type thermoelectric materials and N-type and P-type anti-diffusion layers changing with temperature.

[0042] Figure 3 This is the SEM image of the interface between the N-type thermoelectric material and the N-type anti-diffusion layer after aging at 600℃ for 80h.

[0043] Figure 4This is the SEM image of the interface between the P-type thermoelectric material and the P-type anti-diffusion layer after aging at 600°C for 80 hours.

[0044] Figure 5 This is the interface SEM image of experimental group 1 in Example 2 after aging at 600°C for 80 hours.

[0045] Figure 6 This is the interface SEM image of the comparative group 1 in Example 2 after aging at 600°C for 80 hours.

[0046] Figure 7 This is the diffusion-resistant layer-copper electrode welding interface (containing Ni layer) of the experimental group in Example 3.

[0047] Figure 8 This is the diffusion-resistant layer-copper electrode welding interface of the comparative group in Example 3 (excluding the Ni layer). DETAILED DESCRIPTION

[0048] The present invention first provides a skutterudite thermoelectric component, which is a thermoelectric pair consisting of an N-type structure and a P-type structure; the N-type structure includes an N-type thermoelectric material and an N-type anti-diffusion layer, and the P-type structure includes a P-type thermoelectric material and a P-type anti-diffusion layer;

[0049] Among them, the components of N-type thermoelectric material include Sb, Co, Fe, Yb, and the components of N-type anti-diffusion layer are Fe a Cr b V c The components of the P-type thermoelectric material include Sb, Co, Fe, and La, and the component of the P-type diffusion barrier is Fe. a’ Cr b’ Si c’ ;

[0050] Wherein, a, b, c, a', b', c' represent the mass percentage of each component, a+b+c=100, a'+b'+c'=100; 70≤a≤90, 10≤b≤20, 0<c≤10; 70≤a'≤90, 10≤b'≤20, 0<c'≤10; a and a', b and b', c and c' may be the same or different.

[0051] In a specific embodiment of the present invention, preferably, 75≤a≤88, 12≤b≤18, 2≤c≤8; more preferably, 78≤a≤85, 13≤b≤17, 3≤c≤7;

[0052] In another specific embodiment of the present invention, preferably, 75≤a≤80, 10≤b≤15, 2≤c≤8; 70≤a'≤82, 15≤b'≤20, 3≤c'≤10.

[0053] In one embodiment of the present invention, the N-type thermoelectric material is Sb 12 Co 3.75 Fe 0.25 Yb 0.3 , P-type thermoelectric material is Sb 12 CoFe3La 0.7 .

[0054] Due to the different thermal expansion coefficients of thermoelectric materials of different types and material compositions, the thermoelectric devices prepared therefrom will experience different degrees of thermal expansion in the working environment of heat-electric conversion. Therefore, during long-term use, the bonding between the thermoelectric material and the anti-diffusion layer will become loose, and even the thermoelectric material and the electrode may break, resulting in performance degradation or even failure of the thermoelectric device. In addition, since the operating temperature of the skutterudite thermoelectric device is relatively high, the loose bonding caused by the different thermal expansion between the materials is more obvious.

[0055] According to the present invention, based on the differences in the types and contents of elements in the N-type and P-type thermoelectric material components in the skutterudite thermoelectric assembly, which lead to different thermal expansion coefficients, V elements are added to the anti-diffusion layer at the N-type end and Si elements are added to the anti-diffusion layer at the P-type end, respectively. This can achieve a good match between the linear expansion coefficients of the anti-diffusion layer and the corresponding thermoelectric material, thereby preventing the skutterudite thermoelectric device from being used in a high-temperature environment due to the difference in the thermal expansion coefficients of the materials, which may cause the interface thermal stress between the material and the anti-diffusion layer to increase, thereby reducing the service life of the thermoelectric device.

[0056] Furthermore, during the preparation of the skutterudite thermoelectric component, the N-type thermoelectric material and the P-type thermoelectric material react with the N-type anti-diffusion layer and the P-type anti-diffusion layer, respectively, to form corresponding transition layers. The thickness of the transition layer is in the μm level, and the thickness of the anti-diffusion layer is in the mm level.

[0057] The present invention further provides a method for preparing the skutterudite thermoelectric component, which can be prepared by sintering the anti-diffusion layer and thermoelectric material as a whole, that is, placing the anti-diffusion layer material powder and the thermoelectric material powder together in a mold for SPS sintering.

[0058] Preferably, the method for preparing the skutterudite thermoelectric component comprises the following steps:

[0059] (1) Weigh and mix high-purity elemental raw materials according to the proportion of thermoelectric material components, and the purity of the elemental raw materials is above 99 at.%; put the weighed raw materials into a graphite tube and seal it in a vacuum of 3×10 -3 In a quartz tube below Pa;

[0060] (2) The sample sealed in the quartz tube was heat treated at a temperature of 1000-1200°C for 10-15 hours to melt and uniformly mix the materials, and then water quenched;

[0061] (3) heat treating the quenched sample at a temperature of 500-700°C for more than 50 hours;

[0062] (4) The ingot after heat treatment is taken out, impurities on the surface are polished off, and then it is crushed and ground into powder with a particle size of less than 200 μm;

[0063] (5) Thermoelectric material powder is loaded into a graphite mold, and anti-diffusion layer alloy sheets corresponding to its material type are placed on both sides of the powder. Thermoelectric material blocks with anti-diffusion layers at both ends are prepared by SPS sintering.

[0064] Preferably, the SPS sintering conditions are: heating rate of 50-100°C / min, sintering temperature of 600-750°C, holding time of 15-25 minutes, and cooling rate of 10-30°C / min.

[0065] Compared with the preparation method of sintering the anti-diffusion layer and the thermoelectric material as a whole, the preferred embodiment of the present invention is more suitable for the preparation of a thicker anti-diffusion layer. The thicker anti-diffusion layer can play a better anti-diffusion role and prevent the solder and electrode components from diffusing with the thermoelectric material components during the subsequent use of the thermoelectric device.

[0066] The thermal expansion coefficient of the Fe element in the diffusion barrier is 12×10 -6 / K, and Co3Sb (10~11)×10 -6 Under these sintering conditions, the thermoelectric material and the anti-diffusion layer can form a stable transition layer containing Fe, Cr, and Sb after long-term aging, which can effectively block the components of the thermoelectric material. At the same time, the FeCr alloy also has strong corrosion resistance and low cost.

[0067] Furthermore, the present invention also provides a skutterudite thermoelectric device, comprising the thermoelectric component of the aforementioned solution of the present invention, and an electrode connecting the N-type end and the P-type end of the thermoelectric component.

[0068] The skutterudite thermoelectric device utilizes the aforementioned thermoelectric assembly. By effectively matching the linear expansion coefficients of the anti-diffusion layer and the corresponding thermoelectric material in the thermoelectric assembly, thermal stress at the interface is reduced, effectively improving the reliability and service life of the thermoelectric device. Furthermore, the use of a thicker anti-diffusion layer in the thermoelectric assembly improves the joint strength between the electrode, solder, and anti-diffusion layer during welding of the skutterudite thermoelectric device, ensuring a sufficient thickness of the anti-diffusion layer to achieve its anti-diffusion effect.

[0069] According to the present invention, based on the differences in the types and contents of elements in the N-type and P-type thermoelectric material components in the skutterudite thermoelectric assembly, which lead to different thermal expansion coefficients, V elements are added to the anti-diffusion layer at the N-type end and Si elements are added to the anti-diffusion layer at the P-type end, respectively. This can achieve a good match between the linear expansion coefficients of the anti-diffusion layer and the corresponding thermoelectric material, thereby preventing the skutterudite thermoelectric device from being used in a high-temperature environment due to the difference in the thermal expansion coefficients of the materials, which may cause the interface thermal stress between the material and the anti-diffusion layer to increase, thereby reducing the service life of the thermoelectric device.

[0070] Further preferably, the skutterudite thermoelectric device further includes a nickel layer positioned between the electrode and the anti-diffusion layer of the thermoelectric assembly. The nickel layer introduced between the electrode and the thermoelectric assembly forms a nickel-silver-copper alloy layer during the welding process between the nickel, the solder (containing silver), and the electrode (containing copper). This prevents fractures between the electrode and the anti-diffusion layer when the thermoelectric device is used in high-temperature environments, achieving a more secure connection.

[0071] like Figure 1 The device comprises a thermoelectric assembly (an N-type structure 1 and a P-type structure 2), an electrode 3 connecting the N-type and P-type ends of the thermoelectric assembly, and a nickel layer 4 located between the electrode and the anti-diffusion layer of the thermoelectric assembly. The N-type structure 1 is composed of an N-type thermoelectric material 11 and an N-type anti-diffusion layer 12, while the P-type structure 2 is composed of a P-type thermoelectric material 21 and a P-type anti-diffusion layer 22. It should be noted that the anti-diffusion layer reacts with the thermoelectric material at high temperatures to form a stable intermediate phase transition layer containing Fe, Cr, and Sb.

[0072] Furthermore, when the present invention uses the thermoelectric assembly to prepare the skutterudite thermoelectric device, solder is introduced as a connecting agent during the welding process of the electrode and the thermoelectric material. In order to prevent the solder (mainly composed of silver) from diffusing into the thermoelectric material, a mm-level anti-diffusion layer is used in the thermoelectric assembly.

[0073] The thickness of the nickel layer is at the μm level, the thickness of the anti-diffusion layer is greater than that of the nickel layer, and the thickness of the anti-diffusion layer is 0.1 to 2 mm, preferably 0.5 to 1 mm.

[0074] The present invention achieves the purpose of preventing mutual diffusion of elements between the electrode and the thermoelectric material, and between the solder and the thermoelectric material, by ensuring a sufficiently thick anti-diffusion layer. This prevents the thermoelectric material from penetrating into the electrode and reacting with the electrode, thereby increasing the interface resistance. This also prevents fractures between the electrode and the anti-diffusion layer when the thermoelectric device is used in a high-temperature environment.

[0075] It should be understood that other products further comprising the skutterudite thermoelectric devices described herein also fall within the scope of protection of the present invention. Such products include, but are not limited to, multiple thermoelectric device strings and / or parallel thermoelectric device groups, thermoelectric device strings and / or parallel thermoelectric device groups comprising the skutterudite thermoelectric devices described herein and other thermoelectric materials, and the like.

[0076] The present invention further provides a method for preparing the skutterudite thermoelectric device, wherein the P-type and N-type thermoelectric components in the skutterudite thermoelectric component are connected to electrodes by vacuum brazing.

[0077] The preparation method specifically comprises the following steps:

[0078] (1) Cut the well-sintered P-type and N-type thermoelectric blocks into thermoelectric arms of certain sizes. Polish the upper and lower end surfaces of the electrodes, N-type thermoelectric arms, and P-type thermoelectric arms with 600M sandpaper to remove the surface oxide layer. Then, clean them with anhydrous ethanol ultrasonic cleaning and dry them.

[0079] (2) Place the electrode-silver-based solder-thermoelectric arm-silver-based solder-electrode on the graphite mold in sequence, and then fix it with a pressing plate;

[0080] (3) Place the assembled mold in a vacuum brazing furnace, set the brazing temperature to 670°C, hold for 10 minutes, and hold at a pressure of 2 MPa, and cool with the furnace. In the above preparation method, since the N-type thermoelectric arm and the P-type thermoelectric arm of the thermoelectric assembly provided by the present invention have a thicker anti-diffusion layer, it will be more conducive to achieving the connection between the electrode, the brazing material, and the anti-diffusion layer during the welding process, and after the connection, there is still a sufficient thickness of the anti-diffusion layer to achieve the anti-diffusion effect.

[0081] In addition, the preparation method adopts spot welding, which is more conducive to the rapid preparation of thermoelectric devices and can realize the preparation of large-volume thermoelectric devices, making it convenient to subsequently cut large-volume thermoelectric devices according to the shape and size of the products, and is suitable for large-scale production.

[0082] In order to more clearly understand the above-mentioned objectives, features and advantages of the present disclosure, the scheme of the present disclosure will be further described below. It should be noted that the embodiments of the present disclosure and the features therein can be combined with each other in the absence of conflict.

[0083] In the following description, many specific details are set forth to facilitate a full understanding of the present disclosure, but the present disclosure may also be implemented in other ways different from those described herein; it is obvious that the embodiments in the specification are only part of the embodiments of the present disclosure, rather than all of the embodiments.

[0084] The preferred embodiments of the present invention will be described in detail below with reference to the examples. It should be understood that the following examples are provided for illustrative purposes only and are not intended to limit the scope of the present invention. Those skilled in the art may make various modifications and substitutions to the present invention without departing from the purpose and spirit of the present invention.

[0085] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0086] Unless otherwise specified, the materials and reagents used in the following examples can be obtained from commercial sources.

[0087] Example 1

[0088] Using high-purity raw materials according to the chemical formula of N-type thermoelectric material Sb 12 Co 3.75 Fe 0.25 Yb 0.1 Weigh the ingredients and ensure that the purity of the raw materials is above 99at.%. Vacuum seal the raw materials and the vacuum degree is 3×10 -3 Pa or less. The sample was heat treated at 1050℃ for 20h and then water quenched. The quenched sample was heat treated at 600℃ for 100h. The alloy ingot was then taken out and crushed into powder with a particle size of less than 200μm. The powder was placed in a graphite mold and 1mm thick N-type diffusion barrier sheets were placed on both sides of the powder. The chemical composition of the diffusion barrier is Fe 80 Cr 15 V5 (the subscript number represents the mass percentage). Then the powder and the diffusion barrier sample were subjected to SPS sintering, wherein the heating rate was 60℃ / min, the sintering temperature was 750℃, the holding time was 15 minutes, and the cooling rate was 20℃ / min. Then the sample was cut into a cuboid with a bottom side length of 5mm and a height of 10mm, as shown in FIG. Figure 1 The N-type structure 1 in the figure is prepared. Then the P-type structure 2 is prepared according to the same process steps. The chemical formula of the P-type thermoelectric material is Sb 12 Co1Fe3La 0.7 , the chemical formula of the P-type diffusion barrier is Fe 74 Cr 19Si7 was sintered using the following process parameters: a heating rate of 50°C / min, a sintering temperature of 640°C, a holding time of 15 minutes, and a cooling rate of 20°C / min. The upper and lower surfaces of the electrodes, N-type thermoelectric arms, and P-type thermoelectric arms were polished with 600M sandpaper to remove the surface oxide layer, then ultrasonically cleaned with anhydrous ethanol and dried. A graphite mold was then placed in the order of electrode, silver-based brazing filler metal, thermoelectric arm, silver-based brazing filler metal, and electrode, secured with a press plate. The assembled mold was placed in a vacuum brazing furnace at a temperature of 670°C, a holding temperature of 10 minutes, and a pressure of 2 MPa, followed by cooling. This resulted in the fabrication of a π-shaped thermocouple.

[0089] Figure 2 The thermal expansion coefficients of the N-type and P-type thermoelectric materials and the N-type and P-type diffusion barrier layers vary with temperature. The maximum difference in thermal expansion coefficient between the materials and the diffusion barrier layers is no more than 5%, indicating low interfacial stress at operating temperatures. Figure 3 、 4 The following SEM images show the interfaces between the N-type and P-type thermoelectric materials and the N-type and P-type diffusion barrier layers after aging at 600°C for 80 hours. A transition layer approximately 20 μm thick, containing Fe, Cr, and Sb, is formed at the interface and is uniformly distributed. No diffusion of the material components occurs at either end of the transition layer, demonstrating the alloy's excellent barrier properties.

[0090] Example 2

[0091] A skutterudite thermoelectric component, comprising a thermoelectric pair consisting of an N-type structure 1 and a P-type structure 2; the N-type structure 1 is composed of an N-type thermoelectric material 11 and an anti-diffusion layer 12 at the outer end of the N-type thermoelectric material; the P-type structure is composed of a P-type thermoelectric material 21 and an anti-diffusion layer 22 at the outer end of the P-type thermoelectric material; wherein the N-type thermoelectric material 11 is composed of Sb, Co, Fe, and Yb, and the N-type anti-diffusion layer 12 is composed of Fe a Cr b V c The P-type thermoelectric material 21 is composed of Sb, Co, Fe, and La, and the P-type diffusion prevention layer 22 is composed of Fe a Cr b Si c , a, b, and c represent mass percentages.

[0092] The experimental group and the comparison group were designed according to the different numerical ranges of a, b, and c in the table below. The contact resistance values ​​of the experimental group and the comparison group after the thermoelectric components were used continuously at 600°C for 80 hours, as well as the interface electron microscope scanning results, were used to demonstrate the anti-diffusion layer effect of the present technical solution.

[0093] The following table lists the contact resistance of thermoelectric devices with different barrier layer compositions. It can be found that when the barrier layer composition is within the composition range of the present invention, the contact resistance of the thermoelectric device is between 20 μΩcm and 100 μΩcm.2 The following are the components of Comparative Examples 1 and 2, which are outside the present invention, and the contact resistance is 50μΩcm 2 The above results indicate that the thermoelectric performance of the thermoelectric devices in the comparison group is worse, and they may have lower output power and lifespan than those in the experimental group.

[0094] Table 1: Contact resistance of thermoelectric devices with different barrier layer compositions

[0095]

[0096] Figure 5 and Figure 6 These are SEM images of the interfaces of experimental group 1 and comparative group 1 after aging at 600°C for 80 hours. The reaction layer at the interface in the experimental group is approximately 20 μm thick and is uniform, stable, and dense, with virtually no pores or cracks. In contrast, the reaction layer at the interface in the comparative group is thicker, approximately 50 μm, and contains numerous pores several microns in size. This results in lower interface bonding strength and higher contact resistance.

[0097] Example 3

[0098] A skutterudite thermoelectric device, such as Figure 1 As shown, it includes a thermoelectric pair consisting of an N-type structure 1 and a P-type structure 2, an electrode 3 connecting the N-type end and the P-type end, and a nickel layer 4 located between the electrode and the anti-diffusion layer of the thermoelectric component. The anti-diffusion layer and the thermoelectric material are prepared by SPS sintering, and then a layer of nickel metal is deposited on the outside of the anti-diffusion layer. The electrode is then soldered to the thermoelectric component by brazing. Scanning the interface between the anti-diffusion layer and the electrode using an electron microscope reveals that the interface scanned in the control group without a deposited nickel metal layer has obvious connection traces. In the experimental group with a deposited nickel metal layer, due to the high mutual solubility between nickel and silver-copper solder, a better metallurgical bonding layer can be formed. As a result, during use, the experimental group is less likely to crack between the electrode and the anti-diffusion layer compared to the control group because the nickel atoms in the experimental group form metallic bonds with Ag, Cu and other atoms in the solder, resulting in a tighter bond. This results in a longer service life and lower contact resistance. Figure 7 The figure shows the anti-diffusion layer-copper electrode welding interface (containing Ni layer) of the implementation group. It can be clearly seen that a Ni transition layer is formed between the electrode and the anti-diffusion layer. Figure 8 This is the barrier layer-copper electrode welding interface of the comparison group (without Ni layer). In the figure, only a contact interface is formed between the electrode and the anti-diffusion layer, and no metallurgical bonding layer is formed.

[0099] The foregoing description is intended only to provide specific embodiments of the present disclosure, intended to enable those skilled in the art to understand and implement the present disclosure. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present disclosure. Therefore, the present disclosure is not intended to be limited to the embodiments described herein, but rather to be construed in the broadest manner consistent with the principles and novel features disclosed herein.

Claims

1. A skutterudite thermoelectric component, characterized in that: The skutterudite thermoelectric component is a thermoelectric pair consisting of an N-type structure and a P-type structure; the N-type structure includes an N-type thermoelectric material and an N-type anti-diffusion layer, and the P-type structure includes a P-type thermoelectric material and a P-type anti-diffusion layer; The components of the N-type thermoelectric material include Sb, Co, Fe, and Yb, and the components of the P-type thermoelectric material include Sb, Co, Fe, and La; The component of the N-type anti-diffusion layer is Fe a Cr b V c The component of the P-type diffusion barrier is Fe a’ Cr b’ Si c’ ; Wherein, a, b, c, a', b', c' represent the mass percentage of each component, a+b+c=100, a'+b'+c'=100; 70≤a≤90, 10≤b≤20, 0<c≤10; 70≤a'≤90, 10≤b'≤20, 0<c'≤10.

2. The skutterudite thermoelectric component according to claim 1, characterized in that: Among the components of the N-type anti-diffusion layer, 75≤a≤88, 12≤b≤18, and 2≤c≤8.

3. The skutterudite thermoelectric component according to claim 2, characterized in that: Among the components of the N-type anti-diffusion layer, 78≤a≤85, 13≤b≤17, and 3≤c≤7.

4. The skutterudite thermoelectric component according to claim 1, characterized in that: Among the components of the N-type anti-diffusion layer, 75≤a≤80, 10≤b≤15, and 2≤c≤8; among the components of the P-type anti-diffusion layer, 70≤a'≤82, 15≤b'≤20, and 3≤c'≤10.

5. The skutterudite thermoelectric component according to any one of claims 1 to 4, characterized in that: N-type thermoelectric material is Sb 12 Co 3.75 Fe 0.25 Yb 0.3 , P-type thermoelectric material is Sb 12 CoFe3La 0.7 , where the number represents the number of atoms contained in a single unit cell of the alloy.

6. The skutterudite thermoelectric component according to claim 1, characterized in that: During the preparation of the skutterudite thermoelectric component, the N-type thermoelectric material and the P-type thermoelectric material react with the N-type anti-diffusion layer and the P-type anti-diffusion layer respectively to generate corresponding transition layers.

7. The skutterudite thermoelectric component according to claim 6, characterized in that: The thickness of the transition layer is at the μm level, and the thickness of the diffusion prevention layer is at the mm level.

8. The skutterudite thermoelectric component according to claim 7, characterized in that: The thickness of the diffusion prevention layer is 0.1 to 2 mm.

9. The skutterudite thermoelectric component according to claim 8, characterized in that: The thickness of the anti-diffusion layer is 0.5-1 mm.

10. The method for preparing the skutterudite thermoelectric component according to any one of claims 1 to 9, characterized in that: The preparation method comprises the following steps: (1) Weigh and mix high-purity elemental raw materials according to the proportion of thermoelectric material components, and the purity of the elemental raw materials is above 99 at.%; put the weighed raw materials into a graphite tube and seal it in a vacuum of 3×10 -3 In a quartz tube below Pa; (2) The sample sealed in the quartz tube was heat treated at a temperature of 1000-1200°C for 10-15 hours to melt and uniformly mix the materials, and then water quenched; (3) heat treating the quenched sample at a temperature of 500-700°C for more than 50 hours; (4) The ingot after heat treatment is taken out, impurities on the surface are polished off, and then it is crushed and ground into powder with a particle size of less than 200 μm; (5) Thermoelectric material powder is loaded into a graphite mold, and anti-diffusion layer alloy sheets corresponding to its material type are placed on both sides of the powder. Thermoelectric material blocks with anti-diffusion layers at both ends are prepared by SPS sintering.

11. The preparation method according to claim 10, characterized in that: The conditions for SPS sintering are: heating rate of 50-100°C / min, sintering temperature of 600-750°C, holding time of 15-25min, and cooling rate of 10-30°C / min.

12. A skutterudite thermoelectric device, characterized in that: The invention comprises the thermoelectric component according to any one of claims 1 to 9, and an electrode connecting the N-type end and the P-type end of the thermoelectric component.

13. The skutterudite thermoelectric device according to claim 12, characterized in that: The skutterudite thermoelectric device further includes a nickel layer located between the electrode and the anti-diffusion layer of the thermoelectric component, and the thickness of the nickel layer is at the μm level.

14. The method for preparing a skutterudite thermoelectric device according to claim 12 or 13, characterized in that: The preparation method comprises the following steps: (1) Cut the well-sintered P-type and N-type thermoelectric blocks into thermoelectric arms of certain sizes. Polish the upper and lower end surfaces of the electrodes, N-type thermoelectric arms, and P-type thermoelectric arms with 600M sandpaper to remove the surface oxide layer. Then, clean them with anhydrous ethanol ultrasonic cleaning and dry them. (2) Place the electrode-silver-based solder-thermoelectric arm-silver-based solder-electrode on the graphite mold in sequence, and then fix it with a pressing plate; (3) Place the assembled mold in a vacuum brazing furnace, set the welding temperature to 670°C, keep warm for 10 minutes, and set the pressure to 2 MPa, and cool it with the furnace.

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