High-performance N-type skutterudite thermoelectric material barrier layer with composite structure and preparation method thereof

Abstract

The invention discloses a high-performance N-type skutterudite thermoelectric material barrier layer with a composite structure and a preparation method thereof, and belongs to the technical field of thermoelectric conversion. The preparation method comprises the following steps that a Mo target is installed at a radio frequency target position, a W target is installed at a direct current target position, a skutterudite wafer substrate is fixed to a substrate, and the substrate is heated and vacuumized; and the argon flow is set and introduced, bias voltage is started, radio frequency and direct current power supplies are synchronously started to pre-sputter the target material, then radio frequency sputtering of the Mo connecting layer and direct current sputtering of the W barrier layer are sequentially carried out, and the W-Mo composite barrier layer is prepared. The method is used for solving the technical problems that due to the limitation of the high melting point of refractory metal W, a compact tungsten barrier layer is difficult to prepare through a common sintering process, the diffusion capacity of barrier elements is reduced, mismatch of thermal expansion coefficients of the metal W and a skutterudite matrix is large, and the barrier layer is prone to failure in a thermal cycle service environment.

Description

Technical Field

[0001] This invention belongs to the field of thermoelectric conversion technology, specifically relating to a composite structure high-performance N-type cobaltite thermoelectric material barrier layer and its preparation method. Background Technology

[0002] Cobaltite thermoelectric materials exhibit outstanding potential among medium-temperature thermoelectric materials due to their high thermoelectric figure of merit, excellent mechanical properties, good thermal stability, and low price. Their service temperature range of 250–500 °C makes them suitable for large-scale waste heat recovery scenarios such as industrial waste heat and automotive exhaust, making them key materials for achieving efficient energy utilization.

[0003] Thermoelectric materials need to be integrated into thermoelectric devices for application. During the integration process, thermoelectric materials are generally welded to electrodes with solder or directly connected to electrodes through a sintering process. When operating at high temperatures for extended periods, severe interdiffusion of elements occurs between the thermoelectric material and adjacent solder or electrodes, causing the thermoelectric material to decompose. This leads to increased resistance and thermal resistance at the connection interface, increased residual stress, and consequently, a decrease in the output power and thermoelectric conversion efficiency of the thermoelectric device, as well as a reduction in its service life.

[0004] To improve the interfacial stability and extend the service life of cobaltite thermoelectric devices, existing technologies typically incorporate a barrier layer between the thermoelectric material and the electrode or solder to mitigate element interdiffusion. Refractory metal W possesses the excellent properties of barrier layer materials, such as a high melting point (3410 ℃) and excellent thermal conductivity (174 W / m²). -1 K -1 While tungsten exhibits good electrical conductivity (30.05% IACS) and chemical stability, its preparation as a barrier layer still faces two major technical challenges: First, due to the high melting point of the refractory metal W, common sintering processes cannot produce a dense tungsten barrier layer, thus reducing its ability to block element diffusion; Second, the excessively large thermal expansion coefficient mismatch between metal W and the cobaltite matrix results in low bonding strength at the interface, making the barrier layer prone to failure in thermal cycling service environments.

[0005] Therefore, developing a W-Mo composite barrier layer preparation process with reliable element diffusion blocking performance and excellent stability is of great significance for the development of high-temperature thermoelectric devices in high-performance cobaltite. Summary of the Invention

[0006] In order to overcome the shortcomings of the prior art, the present invention aims to provide a high-performance N-type spheroidal cobaltite thermoelectric material barrier layer with a composite structure and its preparation method, so as to solve the technical problems that the high melting point of refractory metal W makes it difficult to prepare a dense tungsten barrier layer by commonly used sintering processes, resulting in a reduction in its diffusion resistance, and that the large mismatch between the thermal expansion coefficients of metal W and spheroidal cobaltite matrix easily leads to barrier layer failure in thermal cycling service environments.

[0007] To achieve the above objectives, the present invention employs the following technical solution: This invention provides a method for preparing a high-performance N-type cobaltite thermoelectric material barrier layer with a composite structure, comprising the following steps: The Mo target is mounted on the RF target position, the W target is mounted on the DC target position, and the cobaltite wafer substrate is fixed on the substrate. The substrate is heated and a vacuum is drawn. Argon flow rate was set and introduced, bias voltage was turned on, and radio frequency and DC power supply were simultaneously started to pre-sputter the target. Then, radio frequency sputtering of the Mo bonding layer and DC sputtering of the W barrier layer were performed in sequence to obtain the W-Mo composite barrier layer.

[0008] In one embodiment, the process of heating the substrate is as follows: at a vacuum level of 9.0 × 10⁻⁶ -2 At the Pa level, the substrate begins to heat up to 60 °C.

[0009] In one embodiment, the vacuum is 4 × 10⁻⁶. -3 The flow rate of the argon gas is 40~50 SCCM (Standard Cubic Centimeters per Minute), the pressure of the argon gas is 0.4~0.5 Pa, the bias voltage is -70~-80 V, and the pre-sputtering time is 10~20 min.

[0010] In one embodiment, the duty cycle of the Mo interconnect layer during radio frequency sputtering is 70%, the power is 100~120 W, and the sputtering time is 1~1.5 h.

[0011] In one embodiment, the duty cycle of the W barrier layer during DC sputtering is 70%, the power is 100~120 W, and the sputtering time is 2~2.5 h.

[0012] In one embodiment, the preparation process of the cobaltite wafer substrate is as follows: N-type Yb induction melting 0.2 Co4Sb 12 The ingots are cut into wafers, ground and polished, and then subjected to ultrasonic treatment in acetone, alcohol and deionized water in sequence.

[0013] The present invention also provides a composite structure high-performance N-type skua ore thermoelectric material barrier layer, comprising a Mo connecting layer and a W barrier layer sputtered sequentially, wherein the Mo connecting layer serves as a connecting layer between the skua ore wafer substrate and the W barrier layer.

[0014] In one embodiment, the thickness of the Mo bonding layer is 0.4~0.6 μm, and the thickness of the W barrier layer is 2.5~3.5 μm.

[0015] In one embodiment, under thermal aging conditions of 450 °C, an interface reaction layer appears between the Mo bonding layer and the cobaltite wafer substrate, and the thickness of the interface reaction layer increases with the extension of thermal aging time.

[0016] In one embodiment, under thermal aging conditions at 450 °C, diffusion and mutual dissolution occur between the Mo connecting layer and the W barrier layer to form a W-Mo gradient composite barrier layer.

[0017] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a method for preparing a high-performance N-type cobaltite thermoelectric material barrier layer with a composite structure. Metal W has an extremely high melting point, and at the service temperature of cobaltite (250~500 °C), elemental interdiffusion with elements in the cobaltite thermoelectric material is extremely difficult. Furthermore, W possesses high electrical and thermal conductivity, making it well-suited as a barrier layer material. However, high-temperature sintering of W can damage the cobaltite thermoelectric material, while low-temperature sintering results in a porous W layer with poor elemental diffusion resistance. This invention employs magnetron sputtering to prepare the W layer. High-energy W atoms sputtered from a W target collide with the cobaltite wafer substrate, enhancing the bonding force with the substrate while simultaneously diffusing the high-energy atoms on the film surface, continuously filling voids and ultimately producing a dense W barrier layer. Considering the chemical stability of refractory metal W and its significant difference in thermal expansion coefficient compared to cobaltite, to avoid poor bonding strength when directly bonding with cobaltite, metallic Mo was specially designed as a connecting layer between the thermoelectric material and the W layer. Mo and W have similar crystal structures, ensuring bonding between the Mo and W layers. Furthermore, Mo's thermal expansion coefficient is between that of the cobaltite thermoelectric material and metallic W, acting as a transition layer. In addition, the miscibility of Mo and W allows for the formation of a W-Mo solid solution during long-term service. W diffusing into Mo further hinders the diffusion of the thermoelectric material, while Mo diffusing into W facilitates a smooth transition in thermal expansion coefficients. This allows the composite barrier layer to effectively prevent the diffusion of thermoelectric material elements over a long period. Moreover, the connecting layer Mo possesses excellent thermal conductivity (138 W / m²). -1 K -1 With high electrical conductivity (33.28% IACS), it will not introduce excessive thermal resistance and electrical resistance.

[0018] This invention designs and fabricates a high-performance composite barrier layer for N-type cobaltite thermoelectric materials. After continuous thermal aging at 450 °C for 3 and 7 days, it was found that the diffusion of thermoelectric material elements essentially ceases in regions with higher W content, and the interfacial reaction layer thickness is very small. Furthermore, elemental intersolubility was observed between the barrier layer W and the connecting layer Mo, resulting in a smooth transition in the thermal expansion coefficient of the entire composite barrier layer. If the W layer further diffuses into the Mo layer, the ability of the thermoelectric material to diffuse deeper will be further weakened. This thermal aging experiment demonstrates the excellent ability of the composite barrier layer to block element diffusion. The composite barrier layer prepared using the magnetron sputtering process described in this invention has advantages such as density, thinness, uniformity, simple processing, and high repeatability, which is of great significance for the production and application of cobaltite thermoelectric devices. Attached Figure Description

[0019] Figure 1 Yb is an N-type cobaltite material 0.2 Co4Sb 12 Schematic diagram of the W-Mo composite barrier layer structure prepared above; Figure 2 N-type Yb 0.2 Co4Sb 12 W-Mo composite barrier layer of thermoelectric material: (a) cobaltite wafer substrate coated with composite barrier layer; (b) original morphology of the interface between composite barrier layer and thermoelectric material; (c) interface morphology of composite barrier layer and thermoelectric material after 3 days of thermal aging at 450 ℃; (d) interface morphology of composite barrier layer and thermoelectric material after 7 days of thermal aging at 450 ℃. Figure 3 W-Mo composite barrier layer and Yb 0.2 Co4Sb 12 Line element distribution at thermoelectric material interfaces: (a) original; (b) thermally aged at 450 ℃ for 3 days; (c) thermally aged at 450 ℃ for 7 days; Figure 4 W-Mo composite barrier layer and Yb 0.2 Co4Sb 12 The thickness variation of the interfacial reaction layer of thermoelectric materials. Detailed Implementation

[0020] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0021] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0022] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0023] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0024] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0025] This invention provides a high-performance N-type skua ore thermoelectric material barrier layer with a composite structure and its preparation method. The preparation method involves preparing a metal composite barrier layer on a clean skua ore wafer substrate using magnetron sputtering. The preparation of the metal composite barrier layer refers to the sequential sputtering of a Mo bonding layer and a W barrier layer on the skua ore wafer substrate.

[0026] The aforementioned cobaltite wafer substrate refers to the substrate made of N-type thermoelectric material Yb 0.2 Co4Sb 12 The prepared wafer.

[0027] Specifically, this invention is achieved through the following W-Mo composite barrier layer magnetron sputtering technology: Step 1, N-type Yb 0.2 Co4Sb 12 Preparation of cobaltite wafer substrate for thermoelectric materials The N-type Yb molten by induction melting was cut using electrical discharge wire cutting. 0.2 Co4Sb 12 The ingot is cut into wafers with a thickness of 4 mm and a diameter of 45 mm. Then, the top and bottom surfaces of the wafers are polished with 1200#, 1500#, 2000# and 3000# sandpaper in sequence, and then polished with diamond polishing paste with a grit of 1.5.

[0028] The second step is cleaning the cobalt ore wafer substrate before coating. The cobaltite wafer substrate was ultrasonically cleaned in acetone, alcohol and deionized water for 10-20 minutes in sequence to remove impurities from the surface of the cobaltite wafer substrate and keep the upper and lower surfaces of the cobaltite wafer substrate clean.

[0029] The third step is to load the sample and vacuum the vacuum. Mount the Mo target on the RF target position and the W target on the DC target position. Fix the cobaltite wafer substrate onto the substrate. Close the furnace door and perform a vacuum evacuation operation. The vacuum level reaches 9.0 × 10⁻⁶. -2 At the Pa level, the substrate is heated to 60 °C, and the vacuum inside the furnace is evacuated to 4 × 10⁻⁶. -3 Below Pa.

[0030] Step 4: Magnetron sputtering of W-Mo composite barrier layer The argon gas flow rate was set to 40-50 SCCM. Argon gas was introduced, and the bias voltage was started. The RF power supply and DC power supply were started simultaneously for pre-sputtering of the target material. After pre-sputtering, the Mo bonding layer and the W barrier layer were sputtered separately. The specific sputtering parameters are shown in Table 1. After sputtering, the wafer with the film was cooled to room temperature in the furnace before being taken out.

[0031] Table 1 Magnetron sputtering experimental parameters

[0032] The experimental testing methods are as follows: The specific process of cutting and tissue characterization is as follows: A cobaltite wafer substrate coated with a W-Mo composite barrier layer was machined into thermoelectric particles using diamond wire cutting. After mounting, the particles were polished and then analyzed under a scanning electron microscope. 0.2 Co4Sb 12 The interface was used for SEM morphology observation, and EDS was used for W-Mo / Yb analysis. 0.2 Co4Sb 12 The interface is analyzed using both surface and line scans of elements.

[0033] The specific process of the thermal aging test is as follows: The cobaltite wafer substrate coated with W-Mo composite barrier layer was processed into thermoelectric particles by diamond wire cutting. To eliminate the influence of air, the cut thermoelectric particles were vacuum-sealed in a quartz tube, and then the thermoelectric particles were subjected to constant temperature thermal aging test in a heat treatment furnace.

[0034] The tissue analysis following the thermal aging experiment is detailed below: The thermally aged thermoelectric particles were examined under a scanning electron microscope for W-Mo / Yb. 0.2 Co4Sb 12The interface was observed using scanning electron microscopy (SEM), and the W-Mo / Yb morphology was analyzed using energy dispersive spectroscopy (EDS). 0.2 Co4Sb 12 The interface is analyzed using both surface and line scans of elements.

[0035] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0036] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0037] To better understand the present invention, the details of the invention are further described below with reference to the accompanying drawings and examples. The magnetron sputtering equipment used in this embodiment is a JP-500BY magnetron sputtering instrument, which can simultaneously use both RF and DC target positions.

[0038] Example 1: Step 1, N-type Yb 0.2 Co4Sb 12 Preparation of cobaltite wafer substrate for thermoelectric materials The induction-melted Yb was cut using electrical discharge wire cutting. 0.2 Co4Sb 12 The ingot is cut into wafers with a thickness of 4 mm and a diameter of 45 mm. Then, the top and bottom surfaces of the wafers are polished with 1200#, 1500#, 2000# and 3000# sandpaper in sequence, and then polished with diamond polishing paste with a grit of 1.5.

[0039] The second step is cleaning the cobalt ore wafer substrate before coating. The cobaltite wafer substrate was ultrasonically cleaned in acetone, alcohol and deionized water for 15 minutes in sequence. The acetone was used to clean the surface of the cobaltite wafer substrate to remove impurities, the alcohol was used to wash away the acetone, and the deionized water was used to wash away the alcohol, so that the upper and lower surfaces of the cobaltite wafer substrate were clean.

[0040] The third step is to load the sample and vacuum the vacuum. Install the Mo target on the RF target position, install the W target on the DC target position, and install the Yb target on the DC target position. 0.2 Co4Sb12 The cobaltite wafer substrate is fixed onto the wafer. The furnace door is closed, and a vacuum operation is performed. The vacuum level reaches 9 × 10⁻⁶. -2 At the Pa level, the substrate is heated to 60 °C, and the vacuum inside the furnace is evacuated to 3.3 × 10⁻⁶. -3 Pa.

[0041] Step 4: Magnetron sputtering of W-Mo composite barrier layer Argon gas flow rate was set to 50 SCCM. Argon gas was introduced, bias was initiated, sputtering pressure was set to 0.5 Pa, substrate bias was -80 V, and duty cycle was 70%. First, the RF power supply and DC power supply were simultaneously activated for target pre-sputtering. After pre-sputtering, the Mo bonding layer and W barrier layer were sputtered separately. When preparing the W-Mo composite barrier layer, magnetron sputtering was performed first using a metallic Mo target at an RF target site with a sputtering power of 120 W for 1.5 h. Immediately afterwards, a metallic W target was used for DC sputtering at a DC target site with a sputtering power of 120 W for 2.5 h. The prepared composite barrier layer had a Mo layer thickness of approximately 0.6 μm and a W layer thickness of approximately 3.5 μm.

[0042] The specific experimental parameters are shown in Table 2. After sputtering, the cobaltite wafer substrate was cooled to room temperature before being removed from the furnace.

[0043] Table 2 Magnetron sputtering experimental parameters in Example 1

[0044] Step 5: Cutting and Tissue Characterization A cobaltite wafer substrate coated with a W-Mo composite barrier layer was machined into thermoelectric particles with dimensions of 5×5×4 mm using diamond wire cutting. After mounting, the particles were polished and then analyzed under a scanning electron microscope. 0.2 Co4Sb 12 The interface was observed using scanning electron microscopy (SEM), and the W-Mo / Yb morphology was analyzed using energy dispersive spectroscopy (EDS). 0.2 Co4Sb 12 The interface is analyzed using both surface and line scans of elements.

[0045] Step 6, Thermal aging test A cobaltite wafer substrate coated with a W-Mo composite barrier layer was machined into thermoelectric particles with dimensions of 5×5×4 mm using diamond wire cutting. To eliminate the influence of air, the thermoelectric particles were vacuum-sealed in a quartz tube with a vacuum level of 2.6×10⁻⁶. -4 Pa, and then the thermoelectric particles were subjected to constant temperature thermal aging experiments in a heat treatment furnace. The thermal aging temperature was 450 °C for 3 days and 7 days respectively, and then air-cooled.

[0046] Step 7: Tissue analysis after thermal aging experiment The thermally aged thermoelectric particles were examined under a scanning electron microscope for W-Mo / Yb. 0.2 Co4Sb 12 The interface was observed using scanning electron microscopy (SEM), and the W-Mo / Yb morphology was analyzed using energy dispersive spectroscopy (EDS). 0.2 Co4Sb 12 The interface is analyzed using both surface and line scans of elements.

[0047] After preparing the barrier layer sample strictly according to the above parameters and undergoing thermal aging, as follows: Figure 2 , Figure 3 and Figure 4 As shown, after 3-day and 7-day thermal aging experiments, only weak elemental interdiffusion occurred in the cobaltite and W-Mo composite barrier layer, indicating that the composite barrier layer effectively blocked the diffusion of elements in the thermoelectric material; furthermore, W-Mo and Mo-Yb 0.2 Co4Sb 12 Smaller interfaces can facilitate interface integration.

[0048] Example 2 Step 1, N-type Yb 0.2 Co4Sb 12 Preparation of cobaltite wafer substrate for thermoelectric materials The induction-melted Yb was cut using electrical discharge wire cutting. 0.2 Co4Sb 12 The ingot is cut into wafers with a thickness of 4 mm and a diameter of 45 mm. Then, the top and bottom surfaces of the wafers are polished with 1200#, 1500#, 2000# and 3000# sandpaper in sequence, and then polished with diamond polishing paste with a grit of 1.5.

[0049] The second step is cleaning the cobalt ore wafer substrate before coating. The cobaltite wafer substrate was ultrasonically cleaned in acetone, alcohol and deionized water for 15 minutes in sequence. The acetone was used to clean the surface of the cobaltite wafer substrate to remove impurities, the alcohol was used to wash away the acetone, and the deionized water was used to wash away the alcohol, so that the upper and lower surfaces of the cobaltite wafer substrate were clean.

[0050] The third step is to load the sample and vacuum the vacuum. Install the Mo target on the RF target position, install the W target on the DC target position, and install the Yb target on the DC target position. 0.2 Co4Sb 12 The cobaltite wafer substrate is fixed onto the wafer. The furnace door is closed, and a vacuum operation is performed. The vacuum level reaches 9 × 10⁻⁶. -2 At the Pa level, the substrate is heated to 60 °C, and the vacuum inside the furnace is evacuated to 3.3 × 10⁻⁶. -3 Pa.

[0051] Step 4: Magnetron sputtering of W-Mo composite barrier layer Argon gas flow rate was set to 40 SCCM. Argon gas was introduced, bias was initiated, sputtering pressure was set to 0.4 Pa, substrate bias was -70 V, and duty cycle was 70%. First, the RF power supply and DC power supply were simultaneously activated for target pre-sputtering. After pre-sputtering, the Mo bonding layer and W barrier layer were sputtered separately. When preparing the W-Mo composite barrier layer, the magnetron sputtering was performed first using a metallic Mo target at an RF target site with a sputtering power of 100 W for 1 h, followed immediately by DC sputtering using a metallic W target at a DC target site with a sputtering power of 100 W for 2 h. The prepared composite barrier layer had a Mo layer thickness of approximately 0.4 μm and a W layer thickness of approximately 2.5 μm.

[0052] The specific experimental parameters are shown in Table 3. After sputtering, the cobaltite wafer substrate was cooled to room temperature before being removed from the furnace.

[0053] Table 3 Magnetron sputtering experimental parameters in Example 2

[0054] Figure 1 For Yb 0.2 Co4Sb 12 A schematic diagram of the structural design for fabricating a W-Mo composite barrier layer on a thermoelectric material. If the thermoelectric material is directly connected to a copper electrode or solder, and operates for extended periods at the service temperature (250~500 ℃) of the cobaltite thermoelectric device, Yb... 0.2 Co4Sb 12 Medium elements (especially Sb) readily undergo severe interdiffusion with copper or solder, degrading device performance. Therefore, a W-Mo composite barrier layer is fabricated between the thermoelectric material and Cu using magnetron sputtering, utilizing the Mo bonding layer to promote the diffusion of the thermoelectric material Yb. 0.2 Co4Sb 12 The combination with the barrier layer W utilizes the barrier layer W to block the interdiffusion of elements between the thermoelectric material and the electrode material.

[0055] Figure 2 (a) is a cobaltite wafer substrate after the composite barrier layer was prepared by magnetron sputtering in Example 1; Figure 2 (b) indicates the W-Mo composite barrier layer and Yb 0.2 Co4Sb 12 The original morphology of the thermoelectric material interface; Figure 2 (c) indicates the W-Mo composite barrier layer and Yb 0.2 Co4Sb 12 Morphology of thermoelectric material interface after 3 days of thermal aging at 450 °C; Figure 2 (d) indicates the W-Mo composite barrier layer and Yb0.2 Co4Sb 12 The morphology of the thermoelectric material interface after 7 days of thermal aging at 450 °C was observed. It was found that the thickness of the barrier layer W was approximately 3.5 μm, and the thickness of the connecting layer Mo was approximately 0.6 μm. A thin, rough layer appeared in the region between the Mo layer and the cobaltite, and the layer thickness slowly increased with increasing thermal aging time.

[0056] Figure 3 The W-Mo composite barrier layer and Yb in Example 1 0.2 Co4Sb 12 Micro-area energy dispersive spectral lines at the thermoelectric material interface. Figure (a) shows the original elemental distribution at the interface between the composite barrier layer and the thermoelectric material; figure (b) shows the elemental distribution at the interface after thermal aging at 450 °C for 3 days; and figure (c) shows the elemental distribution at the interface after thermal aging at 450 °C for 7 days. Figure 3 It can be seen that after 7 days of thermal aging at 450 °C, the diffusion of Sb and Co elements in the thermoelectric material is deeper than that after 3 days of thermal aging, but the diffusion basically stops after passing through a small amount of W element region. In addition, mutual solubility also occurs between the barrier layer W and the connecting layer Mo, which will be conducive to the formation of W-Mo gradient composite barrier layer, and help to improve the diffusion capacity of barrier elements and reduce thermal stress.

[0057] Figure 4 This indicates the W-Mo composite barrier layer and Yb in Example 1. 0.2 Co4Sb 12 The thickness of the interfacial reaction layer at the thermoelectric material interface changes with prolonged thermal aging. As shown in the figure, the initial interfacial reaction layer thickness is approximately 1.64 μm; after 3 days of thermal aging at 450 °C, the thickness increases to approximately 3.46 μm; after 7 days of thermal aging at 450 °C, the thickness increases to approximately 3.85 μm. The slow increase in the interfacial reaction layer thickness indicates that the composite barrier layer has excellent ability to block element diffusion.

[0058] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A method for preparing a high-performance N-type cobaltite thermoelectric material barrier layer with a composite structure, characterized in that, Includes the following steps: The Mo target is mounted on the RF target position, the W target is mounted on the DC target position, and the cobaltite wafer substrate is fixed on the substrate. The substrate is heated and a vacuum is drawn. Argon flow rate was set and introduced, bias voltage was turned on, and radio frequency and DC power supply were simultaneously started to pre-sputter the target. Then, radio frequency sputtering of the Mo bonding layer and DC sputtering of the W barrier layer were performed in sequence to obtain the W-Mo composite barrier layer.

2. The method for preparing the composite structure high-performance N-type cobaltite thermoelectric material barrier layer according to claim 1, characterized in that, The process of heating the substrate is as follows: At a vacuum level of 9.0 × 10⁻⁶ -2 At the Pa level, the substrate begins to heat up to 60 °C.

3. The method for preparing the composite structure high-performance N-type cobaltite thermoelectric material barrier layer according to claim 1, characterized in that, The vacuum is 4 × 10⁻⁶. -3 The flow rate of the argon gas is 40~50 SCCM, the pressure of the argon gas is 0.4~0.5 Pa, the bias voltage is -70~-80 V, and the pre-sputtering time is 10~20 min.

4. The method for preparing the composite structure high-performance N-type cobaltite thermoelectric material barrier layer according to claim 1, characterized in that, The duty cycle of the Mo bonding layer during radio frequency sputtering is 70%, the power is 100~120 W, and the sputtering time is 1~1.5h.

5. The method for preparing the composite structure high-performance N-type cobaltite thermoelectric material barrier layer according to claim 1, characterized in that, The duty cycle of the W barrier layer during DC sputtering is 70%, the power is 100~120 W, and the sputtering time is 2~2.5h.

6. The method for preparing the composite structure high-performance N-type cobaltite thermoelectric material barrier layer according to claim 1, characterized in that, The preparation process of the cobaltite wafer substrate is as follows: N-type Yb induction melting 0.2 Co4Sb 12 The ingots are cut into wafers, ground and polished, and then subjected to ultrasonic treatment in acetone, alcohol and deionized water in sequence.

7. The composite structure high-performance N-type cobaltite thermoelectric material barrier layer prepared by the method for preparing the composite structure high-performance N-type cobaltite thermoelectric material barrier layer according to any one of claims 1 to 6, characterized in that, It includes a Mo bonding layer and a W barrier layer that are sputtered sequentially, wherein the Mo bonding layer serves as a bonding layer between the cobaltite wafer substrate and the W barrier layer.

8. The composite structure high-performance N-type cobaltite thermoelectric material barrier layer according to claim 7, characterized in that, The thickness of the Mo bonding layer is 0.4~0.6 μm, and the thickness of the W barrier layer is 2.5~3.5 μm.

9. The composite structure high-performance N-type cobaltite thermoelectric material barrier layer according to claim 7, characterized in that, Under thermal aging conditions of 450 °C, an interface reaction layer appears between the Mo bonding layer and the cobaltite wafer substrate, and the thickness of the interface reaction layer increases with the extension of thermal aging time.

10. The composite structure high-performance N-type cobaltite thermoelectric material barrier layer according to claim 7, characterized in that, Under thermal aging conditions of 450 °C, diffusion and mutual dissolution occur between the Mo connecting layer and the W barrier layer to form a W-Mo gradient composite barrier layer.

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