A method for connecting a skutterudite thermoelectric material and an electrode using a surface-textured barrier layer

Abstract

The application relates to a method for connecting a skutterudite thermoelectric material and an electrode by using a surface-textured barrier layer, and relates to the technical field of connection of a skutterudite thermoelectric material and an electrode. The application aims to solve the problem that the existing welding method for the skutterudite thermoelectric material cannot obtain a joint with high mechanical performance and low contact resistance. The method comprises the following steps: etching a plurality of parallel grooves on the surface of the barrier layer to be welded by using a laser, integrating the skutterudite thermoelectric material and the barrier layer subjected to the texturing treatment by means of hot-pressing sintering, and making the surface of the barrier layer subjected to the texturing treatment face the skutterudite thermoelectric material; placing a filler between the skutterudite thermoelectric material and the electrode to be welded to obtain a workpiece A to be welded, and carrying out brazing on the workpiece A to be welded, or directly contacting the skutterudite thermoelectric material and the electrode to be welded to obtain a workpiece B to be welded, and carrying out diffusion welding on the workpiece B to be welded. The application can obtain a method for connecting a skutterudite thermoelectric material and an electrode by using a surface-textured barrier layer.

Description

Technical Field

[0001] This invention relates to the field of connection technology between cobaltite thermoelectric materials and electrodes, and specifically to a method for connecting cobaltite thermoelectric materials and electrodes using a surface-textured barrier layer. Background Technology

[0002] Thermoelectric materials are a class of materials that utilize the Seebeck and Peltier effects to convert heat energy into and out of electrical energy. They have significant potential applications in aerospace, aviation, automotive exhaust heat recovery, industrial waste heat recovery, building refrigeration and heating, and micro-device refrigeration and power supply. In practical applications, bulk thermoelectric materials require connecting P-type and N-type thermoelectric materials with electrode materials to form thermoelectric pairs. Several thermoelectric pairs are then combined to create a thermoelectric device with a specific power output. At the junction of the thermoelectric material and the electrode material, the contact resistance at the junction significantly reduces the maximum conversion efficiency and output power of the thermoelectric device. The mechanical properties of the junction, with strength as the primary indicator, determine whether the thermoelectric device can withstand mechanical shocks during service.

[0003] Regarding the connection method, the primary approach utilizes a smooth-surfaced barrier layer to connect the cobaltite thermoelectric material and the electrode. This method reduces the thickness of the interfacial reaction layer by blocking diffusion between the thermoelectric material and the electrode. A thinner reaction layer means lower contact resistance, but it also weakens the metallurgical bond between the thermoelectric material and the electrode, leading to a deterioration in the mechanical properties of the joint structure itself. The significant difference in the coefficients of thermal expansion between the barrier layer and the thermoelectric material results in substantial residual stress at the joint, further worsening its mechanical properties. Therefore, this method cannot reconcile the contradiction between mechanical properties and contact resistance, and cannot achieve a joint that combines high mechanical properties with low contact resistance. Currently, no research has been reported on connecting cobaltite thermoelectric materials and electrodes by introducing a surface-roughened barrier layer, resulting in a joint that possesses both extremely high mechanical properties and low contact resistance. Summary of the Invention

[0004] The purpose of this invention is to solve the problem that existing welding methods for cobaltite thermoelectric materials cannot achieve joints with both high mechanical properties and low contact resistance, and to provide a method for connecting cobaltite thermoelectric materials and electrodes using a surface-textured barrier layer.

[0005] A method for connecting a cobaltite thermoelectric material and an electrode using a surface-textured barrier layer comprises the following steps:

[0006] Step 1: Clean the surfaces to be welded of the cobaltite thermoelectric material and electrodes; roughen the surface of the barrier layer. The specific steps of the roughening process are as follows: use a laser to etch several parallel grooves on the surface of the barrier layer to be welded, and the distance between two adjacent grooves is 100-200μm. The shape of the groove cross-section is one or a combination of arc, triangle and quadrilateral.

[0007] The molecular formula of the cobaltite thermoelectric material is R r T t X x R is one or more of alkali metals, alkaline earth metals, rare earth metals, and Group III elements; T is one or more of Cr, Mn, Fe, Co, Ni, Ru, Os, Rh, Ir, Pt, and Au; X is one or more of P, As, Sb, Bi, Se, Te, Si, Ge, Sn, Ga, and In; 0 < r ≤ 1, t = 4, 11.8 ≤ x ≤ 12.4;

[0008] Step 2: Integrate the cobaltite thermoelectric material with the roughened barrier layer by hot pressing and sintering, with the roughened side of the barrier layer facing the cobaltite thermoelectric material.

[0009] Step 3: Place the brazing filler metal between the cobaltite thermoelectric material and the electrode to be brazed to obtain workpiece A. Braze workpiece A, or directly contact the cobaltite thermoelectric material with the electrode to be brazed to obtain workpiece B. Diffusion braze workpiece B.

[0010] The beneficial effects of this invention are:

[0011] The reason why the surface-textured barrier layer can improve the mechanical properties of the welded joint is that the texturizing treatment gives the surface of the barrier layer used in this invention a series of parallel grooves. During the integrated hot-pressing sintering process, the powdered cobaltite thermoelectric material fills into the grooves of the barrier layer, thereby forming a periodic alternating stress field at the interface, avoiding stress concentration and weakening the deteriorating effect of stress on the mechanical properties of the joint. The grooves on the surface of the barrier layer provide a larger bonding area between the barrier layer and the cobaltite thermoelectric material, and also increase the path for crack propagation along the interface direction, achieving an effect similar to "pinning reinforcement".

[0012] The barrier layer reduces elemental diffusion between the cobaltite thermoelectric material and the electrode because: the barrier layer used in this invention is composed of two elements. At the welding temperature (550℃~650℃), only a limited and slow interdiffusion reaction exists between the electrode and the barrier layer. Between the cobaltite thermoelectric material and the barrier layer, one element (Co or Fe) in the barrier layer and the cobaltite thermoelectric material exhibit only a limited and slow interdiffusion reaction, while the other element (W or Mo), which has low thermal expansion and low reactivity, does not react with the cobaltite thermoelectric material. The introduction of the low thermal expansion and low reactivity element (W or Mo) effectively adjusts the thermal expansion coefficient of the barrier layer, thus matching it with the thermal expansion coefficient of the cobaltite thermoelectric material and improving the mechanical properties of the joint. Furthermore, it microscopically increases the diffusion distance of elements from the cobaltite thermoelectric material into the barrier layer, thereby significantly suppressing the diffusion of the cobaltite thermoelectric material towards the electrode side.

[0013] This invention utilizes a barrier layer to reduce diffusion between the cobaltite thermoelectric material and the electrode, thereby reducing the thickness of the reaction layer at the joint and resulting in a joint with lower contact resistance. Using the joint obtained by this invention, the reaction layer thickness can be reduced to 11.5 μm, and the strength can reach 32 MPa.

[0014] The present invention provides a method for connecting cobaltite thermoelectric materials and electrodes using a surface-textured barrier layer. Attached Figure Description

[0015] Figure 1 In Example 1, a cobaltite thermoelectric material LaFe4Sb was developed using a CoMo alloy as a barrier layer. 12 Microstructure diagram of the welded joint after brazing with Cu electrode;

[0016] Figure 2 This is a photograph of the interface reaction layer obtained in Example 1. Detailed Implementation

[0017] Specific Implementation Method 1: This implementation method describes a method for connecting cobaltite thermoelectric materials and electrodes using a surface-textured barrier layer, which is carried out according to the following steps:

[0018] Step 1: Clean the surfaces to be welded of the cobaltite thermoelectric material and electrodes; roughen the surface of the barrier layer. The specific steps of the roughening process are as follows: use a laser to etch several parallel grooves on the surface of the barrier layer to be welded, and the distance between two adjacent grooves is 100-200μm. The shape of the groove cross-section is one or a combination of arc, triangle and quadrilateral.

[0019] The molecular formula of the cobaltite thermoelectric material is R r T t X xR is one or more of alkali metals, alkaline earth metals, rare earth metals, and Group III elements; T is one or more of Cr, Mn, Fe, Co, Ni, Ru, Os, Rh, Ir, Pt, and Au; X is one or more of P, As, Sb, Bi, Se, Te, Si, Ge, Sn, Ga, and In; 0 < r ≤ 1, t = 4, 11.8 ≤ x ≤ 12.4;

[0020] Step 2: Integrate the cobaltite thermoelectric material with the roughened barrier layer by hot pressing and sintering, with the roughened side of the barrier layer facing the cobaltite thermoelectric material.

[0021] Step 3: Place the brazing filler metal between the cobaltite thermoelectric material and the electrode to be brazed to obtain workpiece A. Braze workpiece A, or directly contact the cobaltite thermoelectric material with the electrode to be brazed to obtain workpiece B. Diffusion braze workpiece B.

[0022] Specific Implementation Method Two: This implementation method differs from Specific Implementation Method One in that: the electrode in step one is a metal electrode or an alloy electrode; the metal electrode is Cu, Ni, Fe, Co, or Cr, and the alloy electrode is a Cu-based alloy, Ni-based alloy, Fe-based alloy, Co-based alloy, or Cr-based alloy; the Cu-based alloy is CuW or CuMo, the Ni-based alloy is NiW, NiMo, or NiCr, the Fe-based alloy is FeW, FeMo, FeCr, or FeCoNi, the Co-based alloy is CoW, CoMo, CoCr, CoNi, or CoFe, and the Cr-based alloy is CrW, CrMo, CrCoNi, or CrFeNi.

[0023] The other steps are the same as in Specific Implementation Method 1.

[0024] Specific Implementation Method 3: The difference between this implementation method and Specific Implementation Method 1 or 2 is that the cleaning steps in step 1 are as follows: first, rinse with anhydrous ethanol, then place in acetone solution for ultrasonic cleaning for 5 to 30 minutes, and finally air dry.

[0025] The other steps are the same as in Specific Implementation Method 1 or 2.

[0026] Specific Implementation Method Four: The difference between this implementation method and Specific Implementation Methods One to Three is that the barrier layer in step one is a CoMo alloy, CoW alloy, FeMo alloy or FeW alloy with a thickness of 0.02 to 1 mm; the mass fraction of Mo or W element in the barrier layer is 5 to 50%.

[0027] The other steps are the same as those in Specific Implementation Methods One to Three.

[0028] Specific Implementation Method 5: The difference between this implementation method and Specific Implementation Methods 1 to 4 is as follows: The specific steps of integrated hot pressing sintering in step 2 are as follows: The cobaltite thermoelectric material and the roughened barrier layer are placed in a hot press furnace. Under an Ar atmosphere, the cobaltite thermoelectric material and the roughened barrier layer are heated to 700-750°C under a pressure of 50-70 MPa, and held at 700-750°C for 5-15 minutes. After the holding period, the temperature is cooled to room temperature.

[0029] The other steps are the same as those in Specific Implementation Methods One through Four.

[0030] Specific Implementation Method Six: The difference between this implementation method and Specific Implementation Methods One to Five is that: before Ar gas is introduced into the hot pressurizer, the vacuum pressure in the furnace cavity is less than 1 kPa; after Ar gas is introduced, the Ar gas pressure is 0.5 to 1 atm; the heating rate is 80 to 150°C / min, and the cooling rate is 5 to 50°C / min.

[0031] The other steps are the same as those in Specific Implementation Methods 1 to 5.

[0032] Specific Implementation Method Seven: The difference between this implementation method and Specific Implementation Methods One to Six is ​​that the specific steps of brazing in step three are as follows: Place the workpiece A to be brazed in a vacuum heating furnace, heat it to 550-650°C under a pressure of 0.003-0.1 MPa, and hold it at 550-650°C for 1-40 minutes. After holding, first cool it to 50-200°C, and then cool it to room temperature with the furnace. The brazing filler metal is an Ag-based brazing filler metal or an Al-based brazing filler metal with a liquidus temperature of 550-650°C.

[0033] The other steps are the same as those in Specific Implementation Methods 1 to 6.

[0034] Specific Implementation Method Eight: The difference between this implementation method and Specific Implementation Methods One to Seven is that the vacuum pressure inside the vacuum heating furnace is less than 2 × 10⁻⁶. -3 Pa; heating rate is 5–30℃ / min, cooling rate is 2–5℃ / min.

[0035] The other steps are the same as those in Specific Implementation Methods 1 to 7.

[0036] Specific Implementation Method Nine: The difference between this implementation method and Specific Implementation Methods One to Eight is that the specific steps of diffusion welding in step three are as follows: Place the workpiece B to be welded in a heating furnace, heat it to 550-650°C under vacuum or Ar atmosphere and pressure of 5-20 MPa, and keep it at 550-650°C for 1-40 minutes. After the holding time is over, first cool it to 50-100°C, and then cool it to room temperature with the furnace.

[0037] The other steps are the same as those in Specific Implementation Methods 1 to 8.

[0038] Specific Implementation Method Ten: The difference between this implementation method and Specific Implementation Methods One through Nine is that when the heating furnace is in a vacuum atmosphere, the vacuum pressure is less than 2 × 10⁻⁶. -3 Pa; when the heating furnace is filled with Ar atmosphere, the Ar pressure is 0.5-1 MPa; the heating rate is 5-30℃ / min; the cooling rate is 2-5℃ / min.

[0039] The other steps are the same as those in Specific Implementation Methods 1 to 9.

[0040] The beneficial effects of the present invention are verified using the following embodiments:

[0041] Example 1: A method for connecting cobaltite thermoelectric material and electrodes using a surface-textured barrier layer, comprising the following steps:

[0042] Step 1: Apply cobaltite thermoelectric material LaFe4Sb 12 The surfaces to be soldered with Cu electrodes are first rinsed with anhydrous ethanol, then ultrasonically cleaned in acetone solution for 15 minutes, and finally air-dried. The surface of a 500 μm thick CoMo alloy barrier layer (Mo mass fraction of 28%) is roughened. The specific steps of the roughening process are as follows: multiple parallel grooves are etched on the surface of the barrier layer to be soldered using a laser, with a spacing of 200 μm between two adjacent grooves and a triangular cross-sectional shape.

[0043] Step 2: Apply LaFe4Sb cobaltite thermoelectric material 12 The texturalized CoMo alloy barrier layer is integrally hot-pressed and sintered with the cobaltite thermoelectric material, with the texturalized side of the barrier layer facing the cobaltite thermoelectric material. The specific steps of the integral hot-pressing and sintering are as follows: the cobaltite thermoelectric material LaFe4Sb... 12 The texturized CoMo alloy barrier layer was placed in a hot press furnace. Under an Ar atmosphere, the cobaltite thermoelectric material and the texturized barrier layer were heated to 700°C at a heating rate of 120°C / min under a pressure of 60 MPa, and held at 700°C for 10 min. After holding, the material was cooled to room temperature at a cooling rate of 20°C / min. Before Ar gas was introduced into the hot press furnace, the vacuum pressure inside the furnace chamber was 500 Pa. After Ar gas was introduced, the Ar gas pressure was 0.5 atm.

[0044] Step 3: Place the Ag-based solder on the cobaltite thermoelectric material LaFe4Sb 12 Between the Cu electrode and the surface to be welded, a workpiece to be welded is obtained; this is the LaFe4Sb cobaltite thermoelectric material. 12 The surface to be welded is the side with a sintered CoMo alloy barrier layer; the workpiece to be welded is placed in a vacuum heating furnace (vacuum pressure 1.8 × 10⁻⁶).-3 Within a pressure of 0.1 MPa, the furnace is heated to 650°C at a heating rate of 15°C / min and held at 650°C for 20 min. After holding, the furnace is cooled to 100°C at a cooling rate of 2°C / min and then cooled to room temperature. The Ag-based solder is a commercially available Ag-based solder with a liquidus temperature of 606°C.

[0045] Figure 1 In Example 1, a cobaltite thermoelectric material LaFe4Sb was developed using a CoMo alloy as a barrier layer. 12 Microstructure diagram of the weld joint after brazing with Cu electrode; as shown. Figure 1 As shown, the LaFe4Sb thermoelectric material is a cobaltite thermoelectric material. 12 The grooves on the surface of the CoMo alloy barrier layer are fully filled, with good interfacial bonding and no defects; LaFe4Sb cobaltite thermoelectric material 12 It bonds well with the Cu metal electrode connector and has no interface defects.

[0046] Figure 2 A photograph of the interface reaction layer obtained in Example 1; as shown Figure 2 As shown, the CoMo alloy barrier layer effectively blocks the cobaltite thermoelectric material LaFe4Sb 12 The reaction layer thickness is 11.5 μm due to interdiffusion with the Cu electrode. Compared with the method of directly connecting the thermoelectric material and the electrode without setting a barrier layer (100 μm), the reaction layer thickness is reduced by about 90%.

[0047] Tests have shown that the LaFe4Sb thermoelectric material from the schödgmate ore in this embodiment... 12 The shear strength of the Cu metal electrode joint is 32 MPa, which is approximately 130% higher than that of the method using a flat barrier layer to connect the cobaltite thermoelectric material to the electrode (14 MPa). Figure 2 As shown, this embodiment yields a brazed joint that combines extremely high mechanical properties with low contact resistance.

[0048] Example 2: A method for connecting cobaltite thermoelectric material and electrodes using a surface-textured barrier layer, comprising the following steps:

[0049] Step 1: Apply cobaltite thermoelectric material LaFe4Sb 12The surfaces to be soldered with the CoMo alloy electrode (Mo mass fraction of 28%) were first rinsed with anhydrous ethanol, then ultrasonically cleaned in acetone solution for 15 min, and finally air-dried. The surface of the 500 μm thick CoMo alloy barrier layer (Mo mass fraction of 28%) was roughened. The specific steps of the roughening process are as follows: multiple parallel grooves were etched on the surface of the barrier layer to be soldered using a laser, with a spacing of 150 μm between two adjacent grooves and a triangular cross-sectional shape.

[0050] Step 2: Apply LaFe4Sb cobaltite thermoelectric material 12 The cobalt-cobalt alloy barrier layer, after being roughened, is integrally hot-pressed and sintered with the cobalt-cobalt thermoelectric material. The specific steps of the integral hot-pressing and sintering are as follows: the cobalt-cobalt thermoelectric material and the roughened barrier layer are placed in a hot press furnace. Under an Ar atmosphere, the cobalt-cobalt thermoelectric material and the roughened barrier layer are heated to 725°C at a heating rate of 120°C / min under a pressure of 50 MPa, and held at 725°C for 20 min. After the holding period, the material is cooled to room temperature at a cooling rate of 20°C / min. Before Ar gas is introduced into the hot press furnace, the vacuum pressure inside the furnace is 500 Pa. After Ar gas is introduced, the Ar gas pressure is 0.5 atm.

[0051] Step 3: Place the Ag-based solder on the cobaltite thermoelectric material LaFe4Sb 12 Between the welding surfaces of the CoMo alloy electrode and the workpiece to be welded, a cobaltite thermoelectric material LaFe4Sb is obtained. 12 The surface to be welded is the side with a sintered CoMo alloy barrier layer; the workpiece to be welded is placed in a vacuum heating furnace (vacuum pressure 1.5 × 10⁻⁶). -3 Within a pressure of 0.05 MPa, the material is heated to 650°C at a heating rate of 10°C / min and held at 650°C for 15 min. After holding, the material is cooled to 150°C at a cooling rate of 2.5°C / min and then cooled to room temperature with the furnace. The Ag-based solder is a commercially available Ag-based solder with a liquidus temperature of 606°C.

[0052] Tests have shown that the LaFe4Sb thermoelectric material from the schödgmate ore in this embodiment... 12 The joint with the CoMo alloy electrode is well bonded and free of any defects, with a reaction layer thickness of 11.8 μm and a shear strength of 28 MPa.

[0053] Example 3: A method for connecting cobaltite thermoelectric material and electrodes using a surface-textured barrier layer, comprising the following steps:

[0054] Step 1: Apply cobaltite thermoelectric material LaFe4Sb 12The surfaces to be soldered with CuMo alloy electrodes (Mo mass fraction of 28%) were first rinsed with anhydrous ethanol, then ultrasonically cleaned in acetone solution for 15 min, and finally air-dried. The surface of the 500 μm thick CoMo alloy barrier layer (Mo mass fraction of 28%) was roughened. The specific steps of the roughening process are as follows: multiple parallel grooves were etched on the surface of the barrier layer to be soldered using a laser, with a spacing of 100 μm between two adjacent grooves and a triangular cross-sectional shape.

[0055] Step 2: Apply LaFe4Sb cobaltite thermoelectric material 12 The cobalt-cobalt alloy barrier layer, after being roughened, is integrally hot-pressed and sintered with the cobalt-cobalt thermoelectric material. The specific steps of the integral hot-pressing and sintering are as follows: the cobalt-cobalt thermoelectric material and the roughened barrier layer are placed in a hot press furnace. Under an Ar atmosphere, the cobalt-cobalt thermoelectric material and the roughened barrier layer are heated to 750°C at a heating rate of 120°C / min under a pressure of 55 MPa, and held at 750°C for 15 min. After the holding period, the material is cooled to room temperature at a cooling rate of 20°C / min. Before Ar gas is introduced into the hot press furnace, the vacuum pressure inside the furnace is 500 Pa. After Ar gas is introduced, the Ar gas pressure is 0.5 atm.

[0056] Step 3: Place the Ag-based solder on the cobaltite thermoelectric material LaFe4Sb 12 Between the welding surfaces of the CuMo alloy electrode and the workpiece to be welded, a cobaltite thermoelectric material LaFe4Sb is obtained. 12 The surface to be welded is the side with a sintered CoMo alloy barrier layer; the workpiece to be welded is placed in a vacuum heating furnace (vacuum pressure 1.6 × 10⁻⁶). -3 Within a pressure of 0.03 MPa, the material is heated to 640°C at a heating rate of 12°C / min and held at 640°C for 20 min. After holding, the material is cooled to 200°C at a cooling rate of 2°C / min and then cooled to room temperature with the furnace. The Ag-based solder is a commercially available Ag-based solder with a liquidus temperature of 606°C.

[0057] Tests have shown that the LaFe4Sb thermoelectric material from the schödgmate ore in this embodiment... 12 The junction with the CuMo alloy electrode is well bonded and free of any defects, with a reaction layer thickness of 11.6 μm and a shear strength of 30 MPa.

[0058] Example 4: A method for connecting cobaltite thermoelectric material and electrodes using a surface-textured barrier layer, comprising the following steps:

[0059] Step 1: Apply cobaltite thermoelectric material Yb 0.3 Fe4Sb12 The surfaces to be soldered with the CoW alloy electrode (W mass fraction of 40%) were first rinsed with anhydrous ethanol, then ultrasonically cleaned in acetone solution for 15 min, and finally air-dried. The surface of the 1000 μm thick CoW alloy barrier layer (W mass fraction of 40%) was roughened. The specific steps of the roughening process are as follows: multiple parallel grooves were etched on the surface of the barrier layer to be soldered using a laser, with a spacing of 200 μm between two adjacent grooves and a triangular cross-sectional shape.

[0060] Step 2: Apply cobaltite thermoelectric material Yb 0.3 Fe4Sb 12 The cobalt-cobalt alloy barrier layer, after being roughened, is integrally hot-pressed and sintered with the cobalt-cobalt thermoelectric material. The specific steps of the integral hot-pressing and sintering are as follows: the cobalt-cobalt thermoelectric material and the roughened barrier layer are placed in a hot press furnace. Under an Ar atmosphere, the cobalt-cobalt thermoelectric material and the roughened barrier layer are heated to 750°C at a heating rate of 120°C / min under a pressure of 60 MPa, and held at 750°C for 10 min. After the holding period, the material is cooled to room temperature at a cooling rate of 20°C / min. Before Ar gas is introduced into the hot press furnace, the vacuum pressure inside the furnace chamber is 500 Pa. After Ar gas is introduced, the Ar gas pressure is 0.5 atm.

[0061] Step 3: Place the Ag-based solder on the cobaltite thermoelectric material Yb 0.3 Fe4Sb 12 Between the welding surfaces of the CoW alloy electrode and the workpiece to be welded, a cobaltite thermoelectric material Yb is obtained. 0.3 Fe4Sb 12 The surface to be welded is the side with a sintered CoW alloy barrier layer; the workpiece to be welded is placed in a vacuum heating furnace (vacuum pressure 1.0 × 10⁻⁶). -3 Within a pressure of 0.02 MPa, the material is heated to 600°C at a heating rate of 15°C / min and held at 600°C for 18 min. After holding, the material is cooled to 175°C at a cooling rate of 3°C / min and then cooled to room temperature with the furnace. The Ag-based solder is a commercially available Ag-based solder with a liquidus temperature of 567°C.

[0062] Tests have shown that the Yb cobalt ore thermoelectric material in this embodiment... 0.3 Fe4Sb 12 The joint with the CoW alloy electrode is well bonded and free of any defects, with a reaction layer thickness of 9.5 μm and a shear strength of 31 MPa.

[0063] Example 5: A method for connecting cobaltite thermoelectric material and electrodes using a surface-textured barrier layer, comprising the following steps:

[0064] Step 1: Apply cobaltite thermoelectric material Yb 0.3 Fe4Sb 12 The surfaces to be soldered with the CuW alloy electrode (W mass fraction 40%) were first rinsed with anhydrous ethanol, then ultrasonically cleaned in acetone solution for 15 min, and finally air-dried. The surface of the 1000 μm thick CoW alloy barrier layer (W mass fraction 40%) was roughened. The specific steps of the roughening process are as follows: multiple parallel grooves were etched on the surface of the barrier layer to be soldered using a laser, with a spacing of 150 μm between two adjacent grooves and a triangular cross-sectional shape.

[0065] Step 2: Apply cobaltite thermoelectric material Yb 0.3 Fe4Sb 12 The cobalt-cobalt alloy barrier layer, after being roughened, is integrally hot-pressed and sintered with the cobalt-cobalt thermoelectric material. The specific steps of the integral hot-pressing and sintering are as follows: The cobalt-cobalt thermoelectric material and the roughened barrier layer are placed in a hot press furnace. Under an Ar atmosphere, the cobalt-cobalt thermoelectric material and the roughened barrier layer are heated to 700°C at a heating rate of 120°C / min under a pressure of 55 MPa, and held at 700°C for 20 min. After the holding period, the material is cooled to room temperature at a cooling rate of 20°C / min. Before Ar gas is introduced into the hot press furnace, the vacuum pressure inside the furnace chamber is 500 Pa. After Ar gas is introduced, the Ar gas pressure is 0.5 atm.

[0066] Step 3: Place the Ag-based solder on the cobaltite thermoelectric material Yb 0.3 Fe4Sb 12 Between the CuW alloy electrode and the surface to be welded, a workpiece to be welded is obtained, consisting of cobaltite thermoelectric material Yb. 0.3 Fe4Sb 12 The surface to be welded is the side with a sintered CoW alloy barrier layer; the workpiece to be welded is placed in a vacuum heating furnace (vacuum pressure 1.25 × 10⁻⁶). -3 Within a pressure of 0.01 MPa, the furnace is heated to 590°C at a heating rate of 12.5°C / min and held at 590°C for 10 min. After holding, the furnace is cooled to 120°C at a cooling rate of 2.5°C / min and then cooled to room temperature. The Ag-based solder is a commercially available Ag-based solder with a liquidus temperature of 567°C.

[0067] Tests have shown that the Yb cobalt ore thermoelectric material in this embodiment... 0.3 Fe4Sb 12 The joint with the CuW alloy electrode is well bonded and free of any defects, with a reaction layer thickness of 9.6 μm and a shear strength of 29 MPa.

[0068] Example 6: A method for connecting a cobaltite thermoelectric material and an electrode using a surface-textured barrier layer, comprising the following steps:

[0069] Step 1: Apply cobaltite thermoelectric material Yb 0.3 Fe4Sb 12 The surfaces to be soldered with FeW alloy electrodes (W mass fraction 40%) were first rinsed with anhydrous ethanol, then ultrasonically cleaned in acetone solution for 15 min, and finally air-dried. The surface of the 1000 μm thick CoW alloy barrier layer (W mass fraction 40%) was roughened. The specific steps of the roughening process are as follows: multiple parallel grooves were etched on the surface of the barrier layer to be soldered using a laser, with a spacing of 100 μm between two adjacent grooves and a triangular cross-sectional shape.

[0070] Step 2: Apply cobaltite thermoelectric material Yb 0.3 Fe4Sb 12 The cobalt-cobalt alloy barrier layer, after being roughened, is integrally hot-pressed and sintered with the cobalt-cobalt thermoelectric material. The specific steps of the integral hot-pressing and sintering are as follows: the cobalt-cobalt thermoelectric material and the roughened barrier layer are placed in a hot press furnace. Under an Ar atmosphere, the cobalt-cobalt thermoelectric material and the roughened barrier layer are heated to 725°C at a heating rate of 120°C / min under a pressure of 50 MPa, and held at 725°C for 15 min. After the holding period, the material is cooled to room temperature at a cooling rate of 20°C / min. Before Ar gas is introduced into the hot press furnace, the vacuum pressure inside the furnace chamber is 500 Pa. After Ar gas is introduced, the Ar gas pressure is 0.5 atm.

[0071] Step 3: Place the Ag-based solder on the cobaltite thermoelectric material Yb 0.3 Fe4Sb 12 Between the welding surfaces of the FeW alloy electrode and the workpiece to be welded, a cobaltite thermoelectric material Yb is obtained. 0.3 Fe4Sb 12 The surface to be welded is the side with a sintered CoW alloy barrier layer; the workpiece to be welded is placed in a vacuum heating furnace (vacuum pressure 1.2 × 10⁻⁶). -3 Within a pressure of 0.005 MPa, the furnace is heated to 625°C at a heating rate of 14°C / min and held at 625°C for 10 min. After holding, the furnace is cooled to 150°C at a cooling rate of 3°C / min and then cooled to room temperature. The Ag-based brazing filler metal is a commercially available Ag-based brazing filler metal with a liquidus temperature of 567°C.

[0072] Tests have shown that the Yb cobalt ore thermoelectric material in this embodiment... 0.3 Fe4Sb12 The joint with the FeW alloy electrode is well bonded and free of any defects, with a reaction layer thickness of 9.9 μm and a shear strength of 27 MPa.

Claims

1. A method for connecting a cobaltite thermoelectric material and an electrode using a surface-textured barrier layer, characterized in that... The connection method is performed according to the following steps: Step 1: Clean the surfaces to be welded of the cobaltite thermoelectric material and electrodes; roughen the surface of the barrier layer. The specific steps of the roughening process are as follows: use a laser to etch several parallel grooves on the surface of the barrier layer to be welded, and the distance between two adjacent grooves is 100~200μm. The shape of the groove cross-section is one or a combination of arc, triangle and quadrilateral. The molecular formula of the cobaltite thermoelectric material is R r T t X x R is one or more of alkali metals, alkaline earth metals, rare earth metals, and Group III elements; T is one or more of Cr, Mn, Fe, Co, Ni, Ru, Os, Rh, Ir, Pt, and Au; X is one or more of P, As, Sb, Bi, Se, Te, Si, Ge, Sn, Ga, and In; 0 < r ≤ 1, t = 4, 11.8 ≤ x ≤ 12.4; The electrode in step one is a metal electrode or an alloy electrode; The barrier layer in step one is a CoMo alloy, CoW alloy, FeMo alloy, or FeW alloy; Step 2: Integrate the cobaltite thermoelectric material with the roughened barrier layer by hot pressing and sintering, with the roughened side of the barrier layer facing the cobaltite thermoelectric material. Step 3: Place the brazing filler metal between the cobaltite thermoelectric material and the electrode to be brazed to obtain workpiece A. Braze workpiece A, or directly contact the cobaltite thermoelectric material with the electrode to be brazed to obtain workpiece B. Diffusion braze workpiece B.

2. The method for connecting cobaltite thermoelectric material and electrode using a surface-textured barrier layer according to claim 1, characterized in that... The metal electrode is Cu, Ni, Fe, Co, or Cr; the alloy electrode is a Cu-based alloy, Ni-based alloy, Fe-based alloy, Co-based alloy, or Cr-based alloy; the Cu-based alloy is CuW or CuMo; the Ni-based alloy is NiW, NiMo, or NiCr; the Fe-based alloy is FeW, FeMo, FeCr, or FeCoNi; the Co-based alloy is CoW, CoMo, CoCr, CoNi, or CoFe; and the Cr-based alloy is CrW, CrMo, CrCoNi, or CrFeNi.

3. The method for connecting cobaltite thermoelectric material and electrode using a surface-textured barrier layer according to claim 1, characterized in that... The cleaning steps in step one are as follows: first rinse with anhydrous ethanol, then ultrasonically clean in acetone solution for 5-30 minutes, and finally air dry.

4. The method for connecting cobaltite thermoelectric material and electrode using a surface-textured barrier layer according to claim 1, characterized in that... In step one, the thickness of the barrier layer is 0.02~1mm; the mass fraction of Mo or W in the barrier layer is 5~50%.

5. The method for connecting cobaltite thermoelectric material and electrode using a surface-textured barrier layer according to claim 1, characterized in that... The specific steps of the integrated hot pressing sintering in step two are as follows: The cobaltite thermoelectric material and the roughened barrier layer are placed in a hot press furnace. Under an Ar atmosphere, the cobaltite thermoelectric material and the roughened barrier layer are heated to 700-750℃ under a pressure of 50-70MPa and held at 700-750℃ for 5-15 minutes. After the holding period, the material is cooled to room temperature.

6. A method for connecting a cobaltite thermoelectric material and an electrode using a surface-textured barrier layer according to claim 1 or 5, characterized in that... Before Ar gas is introduced into the hot pressurizer, the vacuum pressure inside the furnace cavity is less than 1 kPa. After Ar gas is introduced, the Ar gas pressure is 0.5~1 atm. The heating rate is 80~150℃ / min, and the cooling rate is 5~50℃ / min.

7. The method for connecting cobaltite thermoelectric material and electrode using a surface-textured barrier layer according to claim 1, characterized in that... The specific steps of brazing in step three are as follows: Place the workpiece A to be brazed in a vacuum heating furnace, heat it to 550~650℃ under a pressure of 0.003~0.1MPa, and hold it at 550~650℃ for 1~40 minutes. After holding, first cool it to 50~200℃, and then cool it to room temperature with the furnace. The brazing filler metal is an Ag-based brazing filler metal or an Al-based brazing filler metal with a liquidus temperature of 550~650℃.

8. A method for connecting a cobaltite thermoelectric material and an electrode using a surface-textured barrier layer according to claim 1 or 7, characterized in that... The vacuum pressure inside the vacuum heating furnace is less than 2×10 -3 Pa; heating rate is 5~30℃ / min, cooling rate is 2~5℃ / min.

9. A method for connecting a cobaltite thermoelectric material and an electrode using a surface-textured barrier layer according to claim 1, characterized in that... The specific steps of diffusion welding in step three are as follows: Place the workpiece B to be welded in a heating furnace, heat it to 550~650℃ under vacuum or Ar atmosphere and pressure of 5~20MPa, and hold it at 550~650℃ for 1~40min. After holding, first cool it to 50~100℃, and then cool it to room temperature with the furnace.

10. A method for connecting a cobaltite thermoelectric material and an electrode using a surface-textured barrier layer according to claim 1 or 9, characterized in that... When the heating furnace is in a vacuum atmosphere, the vacuum pressure is less than 2 × 10⁻⁶. -3 Pa; when the heating furnace is filled with Ar atmosphere, the Ar pressure is 0.5~1MPa; the heating rate is 5~30℃ / min; the cooling rate is 2~5℃ / min.

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