Method for connecting skutterudite thermoelectric material and electrode by using high-entropy alloy and soft pure metal composite intermediate layer

Abstract

The invention discloses a method for connecting a skutterudite thermoelectric material and an electrode by using a high-entropy alloy and soft pure metal composite intermediate layer, and relates to a method for connecting the skutterudite thermoelectric material and the electrode. The objective of the invention is to solve the problems of large interface residual stress and easy cracking of an electric connection joint of an existing skutterudite thermoelectric material and an electrode. The method comprises the following steps: 1, cleaning a skutterudite thermoelectric material and an electrode; 2, preparing a composite intermediate layer of soft metal and high-entropy alloy by using methods such as electroplating, physical vapor deposition, sheet or powder intercalation hot pressing and the like, and performing diffusion welding connection on the cobalt ore thermoelectric material and the electrode by using the composite intermediate layer; the material of the soft metal layer comprises but is not limited to Ni, Cu, Fe, Al, Nb, Au, Ag or Pt; and the components of the high-entropy alloy layer comprise but are not limited to an Al-Co-Cr-Fe-Ni system, an Fe-Co-Ni-Cr-Mn system, an Fe-Co-Ni-Cu system, a Mo-Co-Cr-Fe-Ni system, an Hf-Nb-Ta-Ti-Zr system, an Nb-Ti-V-Zr system and an Mo-Nb-Re-Ta-W system. The skutterudite thermoelectric material obtained by utilizing the composite lamination of the soft metal intermediate layer and the high-entropy alloy intermediate layer and the electrode contact have low contact resistivity, extremely high thermal stability and high mechanical property of a connection interface at the same time. The method is suitable for connecting the skutterudite thermoelectric material and the electrode.

Description

Technical Field

[0001] The invention relates to a method for connecting a skutterudite thermoelectric material and an electrode. Background Art

[0002] Thermoelectric materials are based on the Seebeck effect and the Peltier effect, and can directly convert between thermal energy and electrical energy. They are functional materials that can realize the mutual conversion between thermal energy and electrical energy, and have great potential for use in aerospace, automobile exhaust waste heat recovery, industrial waste heat recovery and other fields. In practical applications, thermoelectric materials need to be connected with electrodes to form thermoelectric devices for use. In the process of connecting thermoelectric materials and electrodes, there are problems such as contact effect, interface element reaction and diffusion, and inconsistent thermal expansion coefficient. Selecting a suitable intermediate layer to connect thermoelectric materials and electrodes can obtain a joint with low contact resistivity, high thermal stability and high mechanical strength, thereby realizing reliable operation of thermoelectric devices at service temperature.

[0003] For the connection problem between skutterudite thermoelectric materials and electrodes, there are currently two main mainstream intermediate layers: the first one uses pure metals as intermediate layers, such as Ti, Co, Nb, etc.; the second one uses alloys as intermediate layers, such as CoMo alloys, Ni-Cr-Cu alloys, etc. Although the use of pure metals and alloys as intermediate layers can prevent the reaction and diffusion of interface elements to a certain extent, it cannot solve the problem of diffusion voids introduced by non-equilibrium diffusion in the interface, and the resulting joints have relatively poor thermal stability and high contact resistivity. In recent years, some researchers have used high entropy alloys as intermediate layers, and the low system free energy, lattice distortion effect and diffusion hysteresis effect brought by their high entropy effect can effectively inhibit the diffusion of interface elements, improve the thermal stability of the joint and effectively reduce the contact resistivity. However, compared with pure metals and alloys, the plasticity of high entropy alloys is generally poor. When used as an intermediate layer to connect thermoelectric materials and electrodes, their residual stress is difficult to be relieved through the plastic deformation of the high entropy alloy intermediate layer itself, which easily leads to cracks or even cracks in the joints, seriously affecting the mechanical reliability of the joints connecting skutterudite thermoelectric materials and electrodes. At present, by connecting skutterudite thermoelectric materials and electrodes by means of a high-entropy alloy and a soft pure metal laminate, the high entropy effect of the high-entropy alloy is used to effectively achieve low contact resistivity and high thermal stability of the joint, while the plastic deformation of the soft metal layer is used to effectively release the residual stress of the joint and improve the mechanical strength of the joint. However, no related research on this method has been reported. Summary of the invention

[0004] The present invention aims to solve the problem that the interface of the electrical connection joint between the existing skutterudite thermoelectric material and the electrode is large in residual stress and easy to crack, and proposes a method for connecting the skutterudite thermoelectric material and the electrode by using a high entropy alloy and a soft pure metal composite intermediate layer.

[0005] The method of connecting the skutterudite thermoelectric material and the electrode by using a high entropy alloy and a soft pure metal composite intermediate layer is carried out in the following steps:

[0006] 1. Clean the surface of the skutterudite thermoelectric material and the electrode to be welded;

[0007] 2. Prepare a soft metal intermediate layer on the surface of the electrode by electroplating, physical vapor deposition, thin sheet or powder intercalation hot pressing, and prepare a high entropy alloy intermediate layer on the surface of the soft metal intermediate layer; or prepare a soft metal intermediate layer on the surface of the electrode, and prepare a high entropy alloy intermediate layer on the surface of the skutterudite thermoelectric material; or prepare a high entropy alloy intermediate layer on the surface of the skutterudite thermoelectric material, and prepare a soft metal intermediate layer on the surface of the high entropy alloy intermediate layer; then stack the obtained electrode and the skutterudite thermoelectric material, with the composite stack of the soft metal intermediate layer and the high entropy alloy intermediate layer facing inward, to obtain a workpiece to be welded; perform diffusion welding on the workpiece to be welded;

[0008] Alternatively, a high entropy alloy intermediate layer is prepared on the surface of the skutterudite thermoelectric material by electroplating, physical vapor deposition, sheet or powder intercalation hot pressing, and a soft metal intermediate layer is prepared on the surface of the high entropy alloy intermediate layer; the electrode and the skutterudite thermoelectric material are stacked, with the composite stack of the soft metal intermediate layer and the high entropy alloy intermediate layer facing inward, and a brazing material is placed between the skutterudite thermoelectric material and the electrode to obtain a workpiece to be welded; and the workpiece to be welded is brazed;

[0009] The material of the soft metal intermediate layer includes but is not limited to Ni, Cu, Fe, Al, Nb, Au, Ag, or Pt;

[0010] The material of the high entropy alloy intermediate layer is not limited to Al x Co y Cr z Fe m Ni n Department, Fe x Co y Ni z Cr m Mn n Department, Fe x Co y Ni z Cu m Department, Mo x Co y Cr z Fe m Ni n Department, Hf x Nb y Ta z Ti m Zr n Department, Nb x Ti y Vz Zr m Department, Mo x Nb y Re z Ta m W n System; the above x, y, z, m, and n are values ​​0 to 2.

[0011] The principles and beneficial effects of the present invention are:

[0012] The present invention utilizes a composite laminate consisting of a soft metal intermediate layer and a high entropy alloy intermediate layer to achieve a gradient transition of the thermal expansion coefficient between the skutterudite thermoelectric material and the electrode, while also effectively inhibiting the mutual diffusion of elements between the skutterudite thermoelectric material and the electrode, and the resulting joint has low contact resistivity, high thermal stability and high mechanical strength.

[0013] The reason for suppressing the mutual diffusion of elements between the skutterudite thermoelectric material and the electrode is that the low system free energy, lattice distortion effect and diffusion hysteresis effect of the high entropy alloy intermediate layer used in the present invention can effectively suppress the diffusion of elements at the interface of the electrical connection joint between the skutterudite thermoelectric material and the electrode, thereby suppressing the degree of non-equilibrium diffusion in the joint interface, and preventing the nucleation and growth of diffusion voids in the joint, thereby improving the electrical properties and mechanical strength of the joint.

[0014] The reason for having low contact resistivity and high thermal stability is that the use of a high entropy alloy and a soft pure metal composite intermediate layer to connect the skutterudite thermoelectric material and the electrode can achieve a good match of the thermal expansion coefficients among the composite intermediate layer, the skutterudite thermoelectric material and the electrode, thereby reducing the residual stress of the joint and the change in contact resistivity, and improving the thermal stability of the joint. Combined with the diffusion barrier effect of the high entropy alloy on the interface elements of the joint, the composite intermediate layer can effectively inhibit the mutual diffusion of elements between the skutterudite thermoelectric material and the electrode, reduce the increase in contact resistance and the deterioration of electrical properties caused by the diffusion of interface elements, and improve the electrical conductivity of the joint.

[0015] The reason for achieving high mechanical strength is that the present invention utilizes a high entropy alloy and a soft pure metal composite intermediate layer to connect the cobaltite thermoelectric material and the electrode, and its soft metal intermediate layer (Ni, Cu, Fe, Al, Nb, Au, Ag, or Pt) has good plasticity and toughness, and can effectively release the residual stress of the joint through plastic deformation, preventing the joint from cracking and splitting, thereby greatly improving the mechanical strength of the joint.

[0016] The present invention adopts electroplating, physical vapor deposition, thin sheet or powder intercalation hot pressing and other methods that are compatible with large-scale production methods to prepare a high-entropy alloy and a soft pure metal composite intermediate layer, thereby realizing direct welding of skutterudite thermoelectric materials and metal or alloy electrodes, and the process control is simple. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a photograph of the joint structure obtained in Example 1; DETAILED DESCRIPTION

[0018] The technical solution of the present invention is not limited to the specific implementation modes listed below, but also includes any reasonable combination of the specific implementation modes.

[0019] Specific implementation method 1: In this implementation method, the method of connecting the skutterudite thermoelectric material and the electrode using a high entropy alloy and a soft pure metal composite intermediate layer is carried out in the following steps:

[0020] 1. Clean the surface of the skutterudite thermoelectric material and the electrode to be welded;

[0021] 2. Prepare a soft metal intermediate layer on the surface of the electrode by electroplating, physical vapor deposition, thin sheet or powder intercalation hot pressing, and prepare a high entropy alloy intermediate layer on the surface of the soft metal intermediate layer; or prepare a soft metal intermediate layer on the surface of the electrode, and prepare a high entropy alloy intermediate layer on the surface of the skutterudite thermoelectric material; or prepare a high entropy alloy intermediate layer on the surface of the skutterudite thermoelectric material, and prepare a soft metal intermediate layer on the surface of the high entropy alloy intermediate layer; then stack the obtained electrode and the skutterudite thermoelectric material, with the composite stack of the soft metal intermediate layer and the high entropy alloy intermediate layer facing inward, to obtain a workpiece to be welded; perform diffusion welding on the workpiece to be welded;

[0022] Alternatively, a high entropy alloy intermediate layer is prepared on the surface of the skutterudite thermoelectric material by electroplating, physical vapor deposition, sheet or powder intercalation hot pressing, and a soft metal intermediate layer is prepared on the surface of the high entropy alloy intermediate layer; the electrode and the skutterudite thermoelectric material are stacked, with the composite stack of the soft metal intermediate layer and the high entropy alloy intermediate layer facing inward to obtain a workpiece to be welded; and the workpiece to be welded is brazed;

[0023] The material of the soft metal intermediate layer includes but is not limited to Ni, Cu, Fe, Al, Nb, Au, Ag, or Pt;

[0024] The material of the high entropy alloy intermediate layer is not limited to Al x Co y Cr z Fe m Ni n Department, Fe x Co y Ni z Cr m Mn n Department, Fe x Co y Ni z Cu m Department, Mo x Co yCr z Fe m Ni n Department, Hf x Nb y Ta z Ti m Zr n Department, Nb x Ti y V z Zr m Department, Mo x Nb y Re z Ta m W n System; the above x, y, z, m, and n are values ​​0 to 2.

[0025] This embodiment utilizes a composite laminate consisting of a soft metal intermediate layer and a high entropy alloy intermediate layer to achieve a gradient transition of the thermal expansion coefficient between the skutterudite thermoelectric material and the electrode, while also effectively inhibiting the mutual diffusion of elements between the skutterudite thermoelectric material and the electrode, and the resulting joint has low contact resistivity, high thermal stability and high mechanical strength.

[0026] The reason for suppressing the mutual diffusion of elements between the skutterudite thermoelectric material and the electrode is that the low system free energy, lattice distortion effect and diffusion hysteresis effect of the high entropy alloy intermediate layer used in the present invention can effectively suppress the diffusion of elements at the interface of the electrical connection joint between the skutterudite thermoelectric material and the electrode, thereby suppressing the degree of non-equilibrium diffusion in the joint interface, and preventing the nucleation and growth of diffusion voids in the joint, thereby improving the electrical properties and mechanical strength of the joint.

[0027] The reason for having low contact resistivity and high thermal stability is that the use of a high entropy alloy and a soft pure metal composite intermediate layer to connect the skutterudite thermoelectric material and the electrode can achieve a good match of the thermal expansion coefficients among the composite intermediate layer, the skutterudite thermoelectric material and the electrode, thereby reducing the residual stress of the joint and the change in contact resistivity, and improving the thermal stability of the joint. Combined with the diffusion barrier effect of the high entropy alloy on the interface elements of the joint, the composite intermediate layer can effectively inhibit the mutual diffusion of elements between the skutterudite thermoelectric material and the electrode, reduce the increase in contact resistance and the deterioration of electrical properties caused by the diffusion of interface elements, and improve the electrical conductivity of the joint.

[0028] The reason for achieving high mechanical strength is that the present invention utilizes a high entropy alloy and a soft pure metal composite intermediate layer to connect the cobaltite thermoelectric material and the electrode, and its soft metal intermediate layer (Ni, Cu, Fe, Al, Nb, Au, Ag, or Pt) has good plasticity and toughness, and can effectively release the residual stress of the joint through plastic deformation, preventing the joint from cracking and splitting, thereby greatly improving the mechanical strength of the joint.

[0029] This embodiment adopts electroplating, physical vapor deposition, thin film or powder intercalation hot pressing and other methods that are compatible with large-scale production methods to prepare a high-entropy alloy and a soft pure metal composite intermediate layer, thereby realizing direct welding of skutterudite thermoelectric materials and metal or alloy electrodes, and the process control is simple.

[0030] Specific implementation method 2: This implementation method is different from specific implementation method 1 in that: the cleaning process in step 1 is: first rinse with anhydrous ethanol, then ultrasonically clean in acetone for 5 to 30 minutes, and finally air-dry.

[0031] Specific implementation method three: This implementation method is different from specific implementation methods one or two in that: the electrode in step one is a metal electrode or an alloy electrode;

[0032] The metal electrode is made of Cu, Ni, Fe, Co or Cr;

[0033] The alloy electrode is made of Cu-based alloy, Ni-based alloy, Fe-based alloy, Co-based alloy, or Cr-based alloy;

[0034] 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.

[0035] Specific embodiment 4: This embodiment differs from any one of specific embodiments 1 to 3 in that: the material of the soft metal intermediate layer in step 2 includes but is not limited to Ni, Cu, Fe, Al, Nb, Au, Ag, or Pt.

[0036] Specific embodiment 5: This embodiment differs from any one of specific embodiments 1 to 4 in that: the material of the high entropy alloy intermediate layer in step 2 includes but is not limited to Al x Co y Cr z Fe m Ni n Department, Fe x Co y Ni z Cr m Mn n Department, Fe x Co y Ni z Cu m Department, Mo x Co y Cr z Fe m Nin Department, Hf x Nb y Ta z Ti m Zr n Department, Nb x Ti y V z Zr m Department, Mo x Nb y Re z Ta m W n System; the above x, y, z, m, and n are values ​​0 to 2.

[0037] Specific implementation method 6: This implementation method is different from any one of specific implementation methods 1 to 5 in that: the thickness of the soft metal intermediate layer in step 2 is 1 to 100 μm; the thickness of the high entropy alloy intermediate layer is 1 to 300 μm.

[0038] Specific embodiment 7: This embodiment differs from any one of specific embodiments 1 to 6 in that: the skutterudite thermoelectric material in step 1 has a molecular formula of R r T t X x , wherein: R is one or more elements of alkali metal, alkaline earth metal, rare earth metal or third main group element; T is one or more elements of Cr, Mn, Fe, Co, Ni, Ru, Os, Rh, Ir, Pt or Au; X is one or more elements of P, As, Sb, Bi, Se, Te, Si, Ge, Sn, Ga or In; 0﹤r≤1, t=4, 11.8≤x≤12.4.

[0039] Specific embodiment 8: This embodiment differs from any one of specific embodiments 1 to 7 in that: the brazing process in step 2 is: the vacuum pressure in the vacuum heating furnace is less than 2×10 -3 Pa, the pressure applied to the workpiece during welding is 0.003~0.1MPa, first heat to 550~650℃ at a rate of 5~30℃ / min and keep warm for 1~40min, then cool to 50~100℃ at a rate of 2~5℃ / min, and then cool to room temperature with the furnace.

[0040] Specific embodiment 9: This embodiment is different from any one of specific embodiments 1 to 8 in that: the diffusion welding process described in step 2 is: the diffusion welding is carried out in a heating furnace, the atmosphere of the heating furnace is a vacuum or Ar gas protective atmosphere, and the vacuum pressure of the furnace chamber is less than 2×10 -3Pa, when the heating furnace is Ar gas protective atmosphere, the Ar gas pressure is -0.5Mpa; during welding, the pressure applied to the workpiece to be welded is 5~20Mpa, first heated to 550~650℃ at a speed of 5~30℃ / min and kept warm for 1~40min, then cooled to 50~100℃ at a speed of 2~5℃ / min, and then cooled to room temperature with the furnace.

[0041] Specific embodiment ten: This embodiment differs from any one of specific embodiments one to nine in that: the solder described in step two is an Ag-based solder or an Al-based solder having a liquidus line of 550° C.-650° C.

[0042] Embodiment 1:

[0043] The method of connecting the skutterudite thermoelectric material and the electrode by using the high entropy alloy and the soft pure metal composite intermediate layer in this embodiment is carried out in the following steps:

[0044] 1. Clean the surface of the cobaltite thermoelectric material and the electrode to be welded; the cobaltite thermoelectric material is Yb 0.4 4Sb 12 , the electrode is a CuW electrode;

[0045] The cleaning process in step 1 is: first rinse with anhydrous ethanol, then ultrasonically clean in acetone for 15 minutes, and finally air dry;

[0046] 2. A soft metal intermediate layer is prepared on the surface of the electrode by a powder intercalation hot pressing method, and a high entropy alloy intermediate layer is prepared on the surface of the soft metal intermediate layer; then the obtained electrode and the skutterudite thermoelectric material are stacked, with the composite stack of the soft metal intermediate layer and the high entropy alloy intermediate layer facing inward, to obtain a workpiece to be welded; and diffusion welding is performed on the workpiece to be welded;

[0047] The soft metal intermediate layer in step 2 is made of Ni with a purity of >99%;

[0048] The high entropy alloy intermediate layer in step 2 is made of Al x CoCrFeNi; x is 0.1 in the high entropy alloy intermediate layer;

[0049] In step 2, the thickness of the soft metal intermediate layer is 65 μm; the thickness of the high entropy alloy intermediate layer is 260 μm;

[0050] The diffusion welding process described in step 2 is as follows: the diffusion welding is carried out in a heating furnace, the atmosphere of the heating furnace is an Ar gas protective atmosphere, and the Ar gas pressure is -0.5Mpa; the pressure applied to the workpiece to be welded during welding is 60Mpa, first heated to 700°C at a rate of 110°C / min, 50°C / min, and 25°C / min and kept warm for 10min, then cooled to 300°C at a rate of 5°C / min, and then cooled to room temperature with the furnace.

[0051] Figure 1 is a photo of the joint structure obtained in Example 1; Figure 1 As shown, Yb 0.4 4Sb 12 The skutterudite thermoelectric material and the CuW alloy electrode joint are well combined without any interface defects. The high entropy alloy and the soft pure metal composite intermediate layer Ni / Al 0.1 CoCrFeNi effectively blocks the diffusion of Cu in the electrode into skutterudite, and the Yb and Sb atoms in the skutterudite matrix are effectively blocked from the Yb 0.4 4Sb 12 The skutterudite thermoelectric material side. After testing, the contact resistivity of the joint is 1.3μΩcm 2 The shear strength of the joint is 38MPa. After annealing at 550℃ for 120h, the joint is well bonded and the contact resistivity of the joint is less than 2μΩcm 2 , the shear strength of the joint is 32MPa.

[0052] Embodiment 2:

[0053] The method of connecting the skutterudite thermoelectric material and the electrode by using the high entropy alloy and the soft pure metal composite intermediate layer in this embodiment is carried out in the following steps:

[0054] 1. Clean the surface of the cobaltite thermoelectric material and the electrode to be welded; the cobaltite thermoelectric material is La 0.8 Ga 0.1 Ti 0.1 Fe 3.3 4Sb 12 , the electrode is a CuW electrode;

[0055] The cleaning process in step 1 is: first rinse with anhydrous ethanol, then ultrasonically clean in acetone for 15 minutes, and finally air dry;

[0056] 2. A soft metal intermediate layer is prepared on the surface of the electrode by a powder intercalation hot pressing method, and a high entropy alloy intermediate layer is prepared on the surface of the soft metal intermediate layer; then the obtained electrode and the skutterudite thermoelectric material are stacked, with the composite stack of the soft metal intermediate layer and the high entropy alloy intermediate layer facing inward, to obtain a workpiece to be welded; and diffusion welding is performed on the workpiece to be welded;

[0057] The soft metal intermediate layer in step 2 is made of Ni with a purity of >99%;

[0058] The high entropy alloy intermediate layer in step 2 is made of Al x CoCrFeNi; x is 0.3 in the high entropy alloy intermediate layer;

[0059] In step 2, the thickness of the soft metal intermediate layer is 65 μm; the thickness of the high entropy alloy intermediate layer is 260 μm;

[0060] The diffusion welding process described in step 2 is as follows: the diffusion welding is carried out in a heating furnace, the atmosphere of the heating furnace is an Ar gas protective atmosphere, and the Ar gas pressure is -0.5Mpa; the pressure applied to the workpiece to be welded during welding is 60Mpa, first heated to 650°C at a rate of 125°C / min, 50°C / min, and 25°C / min and kept warm for 10 minutes, then cooled to 300°C at a rate of 5°C / min, and then cooled to room temperature with the furnace.

[0061] After testing, La 0.8 Ga 0.1 Ti 0.1 Fe 3.3 4Sb 12 The skutterudite thermoelectric material and the CuW alloy electrode joint are well bonded, and the contact resistivity of the joint is about 1.2μΩcm 2 The shear strength of the joint is 40MPa. After annealing at 550℃ for 120h, the joint is well bonded and the contact resistivity of the joint is less than 2μΩcm 2 , the shear strength of the joint is 33MPa.

[0062] Embodiment 3:

[0063] The method of connecting the skutterudite thermoelectric material and the electrode by using the high entropy alloy and the soft pure metal composite intermediate layer in this embodiment is carried out in the following steps:

[0064] 1. Clean the surface of the cobaltite thermoelectric material and the electrode to be welded; the cobaltite thermoelectric material is Yb 0.4 4Sb 12 , the electrode is a CuW electrode;

[0065] The cleaning process in step 1 is: first rinse with anhydrous ethanol, then ultrasonically clean in acetone for 15 minutes, and finally air dry;

[0066] 2. Preparing a high entropy alloy intermediate layer on the surface of the skutterudite thermoelectric material by a powder intercalation hot pressing method, and preparing a soft metal intermediate layer on the surface of the high entropy alloy intermediate layer; stacking the electrode and the skutterudite thermoelectric material, with the composite stack of the soft metal intermediate layer and the high entropy alloy intermediate layer facing inward, placing BAg56CuZnSn brazing material between the skutterudite thermoelectric material and the electrode, to obtain a workpiece to be welded; and brazing the workpiece to be welded;

[0067] The soft metal intermediate layer in step 2 is made of Ni with a purity of >99%;

[0068] The high entropy alloy intermediate layer in step 2 is made of Al xCoCrFeNi; x is 0.1 in the high entropy alloy intermediate layer;

[0069] In step 2, the thickness of the soft metal intermediate layer is 60 μm; the thickness of the high entropy alloy intermediate layer is 260 μm;

[0070] The brazing process in step 2 is as follows: use a tubular furnace for heating, an Ar gas atmosphere, and a pressure of 5 MPa applied to the workpiece to be welded. First, heat to 680°C at a rate of 30°C / min and keep warm for 2 minutes, then cool to 100°C at a rate of 5°C / min, and then cool to room temperature with the furnace.

[0071] After testing, Yb 0.4 4Sb 12 The skutterudite thermoelectric material and the CuW alloy electrode joint are well combined without any interface defects. The high entropy alloy and the soft pure metal composite intermediate layer Ni / Al 0.1 CoCrFeNi effectively blocks the diffusion of Cu in the electrode into skutterudite, and the Yb and Sb atoms in the skutterudite matrix are effectively blocked from the Yb 0.4 4Sb 12 On the skutterudite thermoelectric material side, the contact resistivity of the joint is 1.7μΩcm 2 The shear strength of the joint is 37MPa. After annealing at 550℃ for 600h, the joint is well bonded and the contact resistivity of the joint is less than 3μΩcm 2 , the shear strength of the joint is 31MPa.

[0072] Embodiment 4:

[0073] The method of connecting the skutterudite thermoelectric material and the electrode by using the high entropy alloy and the soft pure metal composite intermediate layer in this embodiment is carried out in the following steps:

[0074] 1. Clean the surface of the cobaltite thermoelectric material and the electrode to be welded; the cobaltite thermoelectric material is La 0.8 Ga 0.1 Ti 0.1 Fe 3.3 4Sb 12 , the electrode is a Cu electrode;

[0075] The cleaning process in step 1 is: first rinse with anhydrous ethanol, then ultrasonically clean in acetone for 20 minutes, and finally air dry;

[0076] 2. Preparing a high entropy alloy intermediate layer on the surface of the skutterudite thermoelectric material by a powder intercalation hot pressing method, and preparing a soft metal intermediate layer on the surface of the high entropy alloy intermediate layer; stacking the electrode and the skutterudite thermoelectric material, with the composite stack of the soft metal intermediate layer and the high entropy alloy intermediate layer facing inward, placing BAg56CuZnSn brazing material between the skutterudite thermoelectric material and the electrode, to obtain a workpiece to be welded; and brazing the workpiece to be welded;

[0077] The soft metal intermediate layer in step 2 is made of Fe with a purity of >99%;

[0078] The high entropy alloy intermediate layer in step 2 is made of Al x CoCrFeNi; x is 0.75 in the high entropy alloy intermediate layer;

[0079] In step 2, the thickness of the soft metal intermediate layer is 70 μm; the thickness of the high entropy alloy intermediate layer is 250 μm;

[0080] The brazing process in step 2 is as follows: use a tubular furnace for heating, an Ar gas atmosphere, and a pressure of 5 MPa applied to the workpiece to be welded. First, heat to 680°C at a rate of 30°C / min and keep warm for 2 minutes, then cool to 100°C at a rate of 3°C / min, and then cool to room temperature with the furnace.

[0081] After testing, La 0.8 Ga 0.1 Ti 0.1 Fe 3.3 4Sb 12 The skutterudite thermoelectric material and the Cu electrode joint are well bonded, and the contact resistivity of the joint is 1.5μΩcm 2 The shear strength of the joint is 42MPa. After annealing at 550℃ for 600h, the joint is well bonded and the contact resistivity of the joint is less than 3μΩcm 2 , the shear strength of the joint is 36MPa.

Claims

1. A method for connecting skutterudite thermoelectric material and electrode using a high entropy alloy and a soft pure metal composite intermediate layer, characterized in that: The method proceeds as follows:

1. Clean the surface of the skutterudite thermoelectric material and the electrode to be welded; 2. Prepare a soft metal intermediate layer on the surface of the electrode by electroplating, physical vapor deposition, thin sheet or powder intercalation hot pressing, and prepare a high entropy alloy intermediate layer on the surface of the soft metal intermediate layer; or prepare a soft metal intermediate layer on the surface of the electrode, and prepare a high entropy alloy intermediate layer on the surface of the skutterudite thermoelectric material; or prepare a high entropy alloy intermediate layer on the surface of the skutterudite thermoelectric material, and prepare a soft metal intermediate layer on the surface of the high entropy alloy intermediate layer; then stack the obtained electrode and the skutterudite thermoelectric material, with the composite stack of the soft metal intermediate layer and the high entropy alloy intermediate layer facing inward, to obtain a workpiece to be welded; perform diffusion welding on the workpiece to be welded; Alternatively, a high entropy alloy intermediate layer is prepared on the surface of the skutterudite thermoelectric material by electroplating, physical vapor deposition, thin sheet or powder intercalation hot pressing, and a soft metal intermediate layer is prepared on the surface of the high entropy alloy intermediate layer; The electrode and the skutterudite thermoelectric material are stacked, with the composite stack of the soft metal intermediate layer and the high entropy alloy intermediate layer facing inward to obtain a workpiece to be welded; and the workpiece to be welded is brazed; The material of the soft metal intermediate layer includes but is not limited to Ni, Cu, Fe, Al, Nb, Au, Ag, or Pt; The material of the high entropy alloy intermediate layer is not limited to Al x Co y Cr z Fe m Ni n Department, Fe x Co y Ni z Cr m Mn n Department, Fe x Co y Ni z Cu m Department, Mo x Co y Cr z Fe m Ni n Department, Hf x Nb y Ta z Ti m Zr n Department, Nb x Ti y V z Zr m Department, Mo x Nb y Re z Ta m W n System; the above x, y, z, m, and n take values ​​of 0~2.

2. The method for connecting skutterudite thermoelectric material and electrode by using high entropy alloy and soft pure metal composite intermediate layer according to claim 1, characterized in that: The cleaning process in step 1 is: first rinse with anhydrous ethanol, then ultrasonically clean in acetone for 5 to 30 minutes, and finally air dry.

3. The method for connecting skutterudite thermoelectric material and electrode by using high entropy alloy and soft pure metal composite intermediate layer according to claim 1, characterized in that: In step 1, the electrode is a metal electrode or an alloy electrode.

4. The method for connecting skutterudite thermoelectric material and electrode by using high entropy alloy and soft pure metal composite intermediate layer according to claim 3, characterized in that: The metal electrode is made of Cu, Ni, Fe, Co or Cr; the alloy electrode is made of Cu-based alloy, Ni-based alloy, Fe-based alloy, Co-based alloy or Cr-based alloy.

5. The method for connecting skutterudite thermoelectric material and electrode by using high entropy alloy and soft pure metal composite intermediate layer according to claim 4, characterized in that: 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.

6. The method for connecting skutterudite thermoelectric material and electrode by using high entropy alloy and soft pure metal composite intermediate layer according to claim 1, characterized in that: The thickness of the soft metal intermediate layer in step 2 is 1-100 μm; The thickness of the high entropy alloy intermediate layer is 1~300μm.

7. The method for connecting skutterudite thermoelectric material and electrode by using high entropy alloy and soft pure metal composite intermediate layer according to claim 1, characterized in that: The skutterudite thermoelectric material described in step 1 has a molecular formula of R r T t X x , wherein: R is one or more elements of alkali metal, alkaline earth metal, rare earth metal or third main group element; T is one or more elements of Cr, Mn, Fe, Co, Ni, Ru, Os, Rh, Ir, Pt or Au; X is one or more elements of P, As, Sb, Bi, Se, Te, Si, Ge, Sn, Ga or In; 0﹤r≤1, t=4, 11.8≤x≤12.

4.

8. The method for connecting skutterudite thermoelectric material and electrode by using high entropy alloy and soft pure metal composite intermediate layer according to claim 1, characterized in that: The brazing process in step 2 is as follows: the vacuum pressure in the vacuum heating furnace is less than 2×10 - 3 Pa, the pressure applied to the workpiece during welding is 0.003~0.1MPa, first heated to 550~650℃ at a rate of 5~30℃ / min and kept warm for 1~40min, then cooled to 50~100℃ at a rate of 2~5℃ / min, and then cooled to room temperature with the furnace.

9. The method for connecting skutterudite thermoelectric material and electrode by using high entropy alloy and soft pure metal composite intermediate layer according to claim 1, characterized in that: The diffusion welding process in step 2 is as follows: the diffusion welding is carried out in a heating furnace, the atmosphere of the heating furnace is a vacuum or Ar gas protective atmosphere, and the vacuum pressure of the furnace chamber is less than 2×10 -3 Pa, when the heating furnace is Ar gas protective atmosphere, the Ar gas pressure is -0.5Mpa; during welding, the pressure applied to the workpiece to be welded is 5~20Mpa, first heated to 550~650℃ at a rate of 5~30℃ / min and kept warm for 1~40min, then cooled to 50~100℃ at a rate of 2~5℃ / min, and then cooled to room temperature with the furnace.

10. The method for connecting skutterudite thermoelectric material and electrode by using high entropy alloy and soft pure metal composite intermediate layer according to claim 1, characterized in that: The solder described in step 2 is an Ag-based solder or an Al-based solder having a liquidus line of 550°C-650°C.

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