Interface barrier layer of bismuth telluride-based thermoelectric device and preparation method and application thereof

Abstract

The invention discloses an interface barrier layer of a bismuth telluride-based thermoelectric device and a preparation method and application of the interface barrier layer, the interface barrier layer is a Ni-Co-W alloy coating, the molar ratio of Ni element is 70-93%, the molar ratio of Co element is 6-25%, and the molar ratio of W element is 1-5%. The material is prepared on an N-type or P-type bismuth telluride-based material through electrochemical deposition. The Ni-Co-W interface barrier layer provided by the invention has good thermal stability, can prolong the service life of the thermoelectric device, and can effectively inhibit the reaction between the interface barrier layer and the thermoelectric material in a long-time high-temperature environment, thereby reducing the interface resistance of the thermoelectric device in high-temperature service, and improving the output performance of the device.

Description

Technical Field

[0001] The present invention relates to the technical field of thermoelectric devices, and in particular to an interface barrier layer of a bismuth telluride-based thermoelectric device, and a preparation method and application thereof. Background Art

[0002] Thermoelectric devices are devices that directly convert electrical energy into thermal energy and vice versa, and have important application value in aerospace, new energy, electronic communications, etc. Bismuth telluride is one of the earliest discovered semiconductor thermoelectric materials. It exhibits excellent thermoelectric properties near room temperature and has become the only commercially applied thermoelectric material.

[0003] At present, the demand for new refrigeration technologies in the artificial intelligence and big data storage industries continues to grow, and higher requirements are placed on the thermal stability of thermoelectric cooling devices. At present, in the fields of electronic chip heat dissipation, the working environment temperature of thermoelectric cooling devices is 70-150°C, which places higher requirements on the high-temperature service stability of thermoelectric cooling devices.

[0004] Bismuth telluride-based thermoelectric devices are mainly composed of ceramic substrates, metal electrodes, solder layers, interface barriers and thermoelectric materials. As an important component of thermoelectric devices, the interface barrier is used to prevent the diffusion and reaction between solder and electrode materials and thermoelectric materials, ensuring the stability of thermoelectric devices during service. However, with the increase of operating temperature and long-term service at high temperature, the interface barrier will react with the bismuth telluride-based thermoelectric material and generate an interface reaction layer, which will deteriorate the performance of the thermoelectric device and further affect the service stability of the device. Therefore, the development of new interface barrier materials is the key to the preparation of high-performance and high-reliability bismuth telluride-based thermoelectric devices.

[0005] CN113860873A discloses a method for preparing a bismuth telluride thermoelectric device, comprising: selecting an appropriate amount of Ni powder raw material and C powder raw material, mixing and ball milling to obtain a Ni-C mixed powder; filling an appropriate amount of bismuth telluride powder into a grinding tool and pre-pressing to form a bismuth telluride thermoelectric material layer; filling the Ni-C mixed powder into a grinding tool after drying, and evenly stacking it on the bismuth telluride thermoelectric material layer for secondary pre-pressing to form a Ni-C barrier layer; performing SPS sintering on the bismuth telluride thermoelectric material layer and the Ni-C barrier layer, and obtaining a bismuth telluride thermoelectric device after cooling. By selecting C raw material to partially replace Ni raw material, the diffusion and reaction of Ni and Te elements at the interface of the bismuth telluride hot spot material layer and the barrier layer can be reduced to a certain extent, but the effect is not very obvious, and the interface contact resistance is high.

[0006] CN 111211214 A An interface barrier layer for a half-Heusler alloy thermoelectric material, wherein the chemical formula of the half-Heusler alloy thermoelectric material is ABX, wherein A is at least one of Sc, Y, Ti, Zr, Hf, V, Nb, and Ta, B is at least one of Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, and Pt, and X is at least one of Sn, Sb, and Bi; the component of the interface barrier layer is a single substance of a full Heusler alloy with a chemical formula of AB2X containing the same elements as the half-Heusler alloy thermoelectric material, or an interstitial metal element B of the half-Heusler alloy thermoelectric material ABX. The interface barrier layer material matches the lattice parameter and thermal expansion coefficient of the half-Heusler alloy matrix, thereby minimizing the problem of device cracking and failure caused by interface thermal stress. However, the interface barrier layer has higher requirements on the composition of the interface barrier layer, which needs to match the lattice parameter and thermal expansion coefficient of the half-Heusler alloy matrix. Summary of the invention

[0007] The present invention aims to solve the problem that the interface barrier layer of the thermoelectric material has poor thermal stability and the device performance deteriorates at high temperature. The present invention provides a nickel-based alloy interface barrier layer, which can effectively prevent the reaction between the thermoelectric material and the interface barrier layer at high temperature, reduce the interface contact resistance, and maintain the stability of the thermoelectric device for long-term service at high temperature.

[0008] To achieve the above object, the technical solution adopted by the present invention is:

[0009] An interface barrier layer of a bismuth telluride-based thermoelectric device, wherein the interface barrier layer is a Ni-Co-W alloy plating layer, wherein the molar proportion of the Ni element is 70-93%, the molar proportion of the Co element is 6-25%, and the molar proportion of the W element is 1-5%.

[0010] In the present invention, based on the conventional Ni plating layer, Co and W elements are rationally designed to inhibit the diffusion of interface barrier layer elements. The obtained Ni-Co-W alloy plating layer as the interface barrier layer has a very low contact resistance of the thermoelectric device, which is less than 4μΩ·cm 2 Even after aging at 150°C for 8 days, the contact resistance only increased to 3.81 μΩ·cm 2 About, under this contact resistance, the device performance can still reach more than 90% of the material performance, which is conducive to the thermoelectric device serving at higher temperatures for a long time.

[0011] Preferably, the molar proportion of the Ni element is 70-83%, the molar proportion of the Co element is 10-22%, and the molar proportion of the W element is 1-5%. The thermal stability of the coating with a Co content of more than 10% is better.

[0012] Preferably, the thickness of the Ni-Co-W alloy coating is 2 to 10 μm. The thinner the thickness of the interface barrier layer, the more conducive it is to obtaining a small interface resistance, thereby reducing the loss of electric energy at the interface; however, electrodes of a certain thickness can prevent the diffusion of interface elements during high-temperature use of thermoelectric devices, thereby increasing the service life of the device.

[0013] The present invention also provides a method for preparing the interface barrier layer of the bismuth telluride-based thermoelectric device, comprising the steps of:

[0014] Step 1, grinding, degreasing, pickling and etching, and ultrasonic cleaning of the bismuth telluride-based material wafer;

[0015] Step 2, placing the treated bismuth telluride-based material wafer in an electroplating solution for electrodeposition to form an interface barrier layer on the surface of the wafer;

[0016] The electroplating solution comprises nickel salt, cobalt salt and tungsten salt. Taking the total molar amount of nickel salt, cobalt salt and tungsten salt as 100%, the molar proportion of nickel salt is 70-93%, the molar proportion of cobalt salt is 6-25%, and the molar proportion of tungsten salt is 1-5%.

[0017] The present invention adopts the electrodeposition method to prepare the Ni-Co-W alloy coating, the preparation method is simple, the conditions are easy to control, the repeatability is good, and the obtained interface barrier layer is well combined with the thermoelectric material matrix.

[0018] Preferably,

[0019] The nickel salt includes one or more of nickel sulfate, nickel chloride, nickel sulfamate and hydrates thereof;

[0020] The cobalt salt includes one or more of cobalt sulfate, cobalt chloride, cobalt nitrate and hydrates thereof;

[0021] The tungsten salt includes one or more of sodium tungstate and its hydrate.

[0022] The electroplating solution also includes a pH buffer, a complexing agent and a surfactant.

[0023] During electrodeposition, the bismuth telluride-based material wafer serves as the cathode and the nickel plate serves as the anode.

[0024] The current density during electrodeposition is 1 to 3 A / dm 2 The deposition time is 10 to 20 minutes, and the plating solution temperature is 40 to 50°C.

[0025] The pH buffer includes one or more of citric acid and boric acid;

[0026] The complexing agent includes one or more of sodium citrate and sodium acetate;

[0027] The surfactant includes one or more of sodium dodecyl sulfate and sodium dodecylbenzene sulfonate.

[0028] The bismuth telluride-based material wafer includes N-type or P-type bismuth telluride-based material.

[0029] Preferably, the electroplating solution includes 20-120 g / L nickel salt, 5-10 g / L cobalt salt, 2-10 g / L tungsten salt, 10-60 g / L pH buffer, 40-60 g / L complexing agent, and 0.2-0.5 g / L surfactant.

[0030] The present invention also provides a bismuth telluride-based thermoelectric device, comprising a ceramic substrate, an electrode and a bismuth telluride-based thermoelectric material with an interface barrier layer on the surface, wherein the interface barrier layer on the surface of the bismuth telluride-based thermoelectric material is prepared on the surface of the thermoelectric material by the preparation method.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] (1) The process of the present invention is simple to operate, the conditions are easy to control, and the repeatability is good. The obtained interface barrier layer is well bonded to the thermoelectric material matrix. The interface of the prepared thermoelectric device has a low interface contact resistance, and the performance of the thermoelectric device can be fully exerted.

[0033] (2) The Ni-Co-W alloy interface barrier layer in the present invention can effectively prevent the reaction between the thermoelectric material matrix and the interface material, inhibit the generation of the interface reaction layer, and effectively reduce the interface contact resistance of the thermoelectric device serving at a higher temperature, thereby making the thermoelectric device more thermally stable and greatly improving the service life of the device.

[0034] (3) The Ni-Co-W alloy interface barrier layer in the present invention can be applied to both N-type bismuth telluride-based materials and P-type bismuth telluride-based materials, thereby simplifying the preparation process of bismuth telluride-based thermoelectric devices and making them suitable for large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is the microstructure diagram of the n-Bi2Te3 / Ni-Co-W / SAC305 / Cu thermoelectric junction interface prepared in Example 1.

[0036] Figure 2 Graph showing the change in the interfacial contact resistivity of the thermoelectric junction in Examples 1 and 2 with aging time.

[0037] Figure 3 The XRD patterns of the n-Bi2Te3 material wafer plated with the Ni-Co-W interface barrier layer in Example 1 at different thermal aging conditions.

[0038] Figure 4This is the microstructure diagram of the p-Bi2Te3 / Ni-Co-W / SAC305 / Cu thermoelectric junction interface prepared in Example 2.

[0039] Figure 5 The XRD patterns of the p-Bi2Te3 material wafer plated with a Ni-Co-W interface barrier layer in Example 2 at different thermal aging conditions.

[0040] Figure 6 This is a graph showing the change in the interface contact resistivity of the thermoelectric junction in Example 3 with thermal aging time.

[0041] Figure 7 This is a graph showing the change in interface contact resistivity of the n-Bi2Te3 / Ni-Co-W / SAC305 / Cu thermoelectric junction, n-Bi2Te3 / Ni-Co-Cr / SAC305 / Cu thermoelectric junction and n-Bi2Te3 / Ni / SAC305 / Cu thermoelectric junction prepared in Example 1 and Comparative Example 2 as well as Comparative Example 1 versus aging time.

[0042] Figure 8 This is a graph showing the change in the internal resistance of the thermoelectric device in the application example as a function of thermal aging time. DETAILED DESCRIPTION

[0043] In order to make the purpose, technical scheme and advantages of the present invention clearer, the present invention is further described in detail below in conjunction with embodiment. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. Those skilled in the art can make modifications or equivalent substitutions based on the understanding of the technical scheme of the present invention without departing from the spirit and scope of the technical scheme of the present invention, and all should be included in the protection scope of the present invention.

[0044] The raw materials used in the following specific embodiments are all purchased from the market.

[0045] Example 1

[0046] Step 1, pre-treating the N-type bismuth telluride-based material wafer before plating: including metallographic sandpaper polishing, using acetone solution to degrease the wafer surface, using pickling solution to pickle and etch the wafer surface for 4 minutes, and using deionized water to ultrasonically clean the wafer for 5 minutes. The volume ratio of nitric acid, sulfuric acid and deionized water in the pickling solution is 1:1:4, wherein the nitric acid is 68% concentrated nitric acid by mass, and the sulfuric acid is 98% concentrated sulfuric acid by mass.

[0047] Step 2, the N-type bismuth telluride-based material wafer that has been pre-treated before plating in step 1 is heated in a water bath in an electroplating solution while performing direct current electrodeposition to prepare a Ni-Co-W alloy coating on the wafer. The total molar amount of nickel salt, cobalt salt and tungsten salt in the electroplating solution is 100%, wherein the molar proportion of nickel salt is 81%, the molar proportion of cobalt salt is 16%, and the molar proportion of tungsten salt is 3%.

[0048] The formula of the electroplating solution is: 80g / L nickel sulfate hexahydrate, 6g / L cobalt sulfate, 3g / L sodium tungstate, 20g / L citric acid, 50g / L sodium citrate, 0.4g / L sodium dodecyl sulfate, 20g / L boric acid. The electroplating process parameters are: the anode is a nickel plate, the cathode is an N-type bismuth telluride-based material wafer, and the current density is 3A / dm 2 , the deposition time is 15 minutes, the plating solution temperature is 50°C, and an N-type bismuth telluride-based material wafer containing an interface barrier layer is obtained.

[0049] In order to demonstrate the effect of the interface barrier layer in practical applications, an N-type bismuth telluride-based material wafer plated with a Ni-Co-W interface barrier layer was welded to a Cu electrode to prepare a thermoelectric junction of an N-type bismuth telluride material and an electrode. The specific operation is: the N-type bismuth telluride material plated with a Ni-Co-W layer obtained in step 2 and the Cu electrode are reflow soldered using SAC305 solder paste to obtain an n-Bi2Te3 / Ni-Co-W / SAC305 / Cu thermoelectric junction.

[0050] The interface micromorphology of n-Bi2Te3 / Ni-Co-W / SAC305 / Cu thermoelectric junction is shown in Figure 1 The thickness of the Ni-Co-W interface barrier layer is 4-8μm, which can effectively block the diffusion of Sn-based solder.

[0051] The interface contact resistance of the finally obtained n-Bi2Te3 / Ni-Co-W / SAC305 / Cu thermoelectric junction was tested, and the test results are shown in Figure 2 The circular point shown on day 0 shows that its contact resistivity is 3.33 μΩ·cm 2 , the resistivity is very low, which fully demonstrates the excellent interface performance of the Ni-Co-W interface barrier layer.

[0052] Thermal stability test

[0053] The N-type bismuth telluride material wafer plated with a Ni-Co-W alloy interface barrier layer and the n-Bi2Te3 / Ni-Co-W / SAC305 / Cu thermoelectric junction sample prepared in Example 1 were respectively placed in quartz tubes, vacuum-sealed, and placed in an annealing furnace for aging treatment at an aging temperature of 150°C for 1 day, 2 days, 4 days, and 8 days, respectively.

[0054] The phase analysis of the bismuth telluride material wafer after aging treatment was carried out using the Netherlands PANalytical (Aries DY866) X-ray polycrystalline diffractometer (XRD), such as Figure 3 As shown, it can be seen from the figure that even after 8 days of aging treatment, no interface reaction occurred between the N-type bismuth telluride material and the Ni-Co-W interface barrier layer, and no NiTe reaction layer was produced.

[0055] The test results of the thermoelectric junction interface contact resistivity at different aging times are shown in Figure 2 The circular symbols and Table 2 show that even when the aging time is 8 days, the interface contact resistivity is only 3.81 μΩ·cm 2 , the interface performance is still good.

[0056] Example 2

[0057] Step 1, pre-treating the P-type bismuth telluride-based material wafer before plating, including metallographic sandpaper polishing, using acetone solution to degrease the wafer surface, using pickling solution to pickle and etch the wafer surface for 5 minutes, and using deionized water to ultrasonically clean the wafer for 5 minutes. The pickling solution contains nitric acid, sulfuric acid and deionized water in a volume ratio of 1:1:4, wherein the nitric acid is concentrated nitric acid with a mass fraction of 68%, and the sulfuric acid is concentrated sulfuric acid with a mass fraction of 98%.

[0058] Step 2, the P-type bismuth telluride-based material wafer that has been pre-treated before plating in step 1 is heated in a water bath in an electroplating solution while performing direct current electrodeposition to prepare a Ni-Co-W alloy coating on the wafer. The total molar amount of nickel salt, cobalt salt and tungsten salt in the electroplating solution is 100%, wherein the molar proportion of nickel salt is 81%, the molar proportion of cobalt salt is 16%, and the molar proportion of tungsten salt is 3%.

[0059] The formula of the electroplating solution is: 80g / L nickel sulfate hexahydrate, 6g / L cobalt sulfate, 3g / L sodium tungstate, 20g / L citric acid, 50g / L sodium citrate, 0.4g / L sodium dodecyl sulfate, 20g / L boric acid. The electroplating process parameters are: the anode is a nickel plate, the cathode is a P-type bismuth telluride-based material wafer, and the current density is 3A / dm 2 , the deposition time is 15 minutes, the plating solution temperature is 50°C, and an N-type bismuth telluride-based material wafer containing an interface barrier layer is obtained.

[0060] The P-type bismuth telluride material plated with a Ni-Co-W layer in step 2 and the Cu electrode are reflow soldered using SAC305 solder paste to obtain a p-Bi2Te3 / Ni-Co-W / SAC305 / Cu thermoelectric junction.

[0061] The interface micromorphology of p-Bi2Te3 / Ni-Co-W / SAC305 / Cu thermoelectric junction is shown in Figure 4The thickness of the Ni-Co-W interface barrier layer is 4-6 μm, which can effectively block the diffusion of Sn-based solder.

[0062] The interface contact resistance of the finally obtained p-Bi2Te3 / Ni-Co-W / SAC305 / Cu thermoelectric junction was tested, and the test results are shown in Figure 2 The square point shown on day 0 shows that its contact resistivity is 4.49 μΩ·cm 2 , which fully demonstrates the excellent interface performance of the Ni-Co-W interface barrier layer.

[0063] Thermal stability test

[0064] The P-type bismuth telluride material wafer plated with a Ni-Co-W alloy interface barrier layer and the p-Bi2Te3 / Ni-Co-W / SAC305 / Cu thermoelectric junction sample prepared in Example 2 were respectively placed in quartz tubes, vacuum-sealed, and placed in an annealing furnace for aging treatment at an aging temperature of 150°C for 1 day, 2 days, 4 days, and 8 days, respectively.

[0065] The phase analysis of the bismuth telluride material wafer after aging treatment was carried out using the Netherlands PANalytical (Aries DY866) X-ray polycrystalline diffractometer (XRD), such as Figure 5 As shown in Figure 2 and Table 2, it can be seen that even after 8 days of aging treatment, no interface reaction occurred between the P-type bismuth telluride material and the Ni-Co-W interface barrier layer, and no NiTe reaction layer was produced.

[0066] The test results of the thermoelectric junction interface contact resistivity at different aging times are shown in Figure 2 As shown in Table 2, it can be seen from the figure that even when the aging time is 8 days, the interface contact resistivity value is only 5.21μΩ·cm 2 , the interface performance is still good.

[0067] Example 3

[0068] Step 1, pre-treating the P-type bismuth telluride-based material wafer before plating, including metallographic sandpaper polishing, using acetone solution to degrease the wafer surface, using pickling solution to pickle and etch the wafer surface for 5 minutes, and using deionized water to ultrasonically clean the wafer for 5 minutes. The pickling solution contains nitric acid, sulfuric acid and deionized water in a volume ratio of 1:1:4, wherein the nitric acid is concentrated nitric acid with a mass fraction of 68%, and the sulfuric acid is concentrated sulfuric acid with a mass fraction of 98%.

[0069] Step 2, the N-type bismuth telluride-based material wafer that has been pre-treated before plating in step 1 is heated in a water bath in an electroplating solution while being subjected to direct current electrodeposition to prepare Ni-Co-W coatings with Co element contents of 6%, 9%, 12%, and 21% on the wafer. The total molar amount of nickel salt, cobalt salt, and tungsten salt in the electroplating solution is 100%, wherein the molar proportion of nickel salt is adjusted to 91%, 88%, 85%, and 76%, the molar proportion of cobalt salt is 6%, 9%, 12%, and 21%, and the molar proportion of tungsten salt is 3%.

[0070] The mass concentrations of nickel sulfate hexahydrate in the formula of the electroplating solution are 110g / L, 100g / L, 90g / L, and 70g / L, cobalt sulfate is 1.5g / L, 3g / L, 4.5g / L, and 8g / L, sodium tungstate is 3g / L, citric acid is 20g / L, sodium citrate is 50g / L, sodium dodecyl sulfate is 0.4g / L, and boric acid is 20g / L.

[0071] The electroplating process parameters are: the anode is a nickel plate, the cathode is an N-type bismuth telluride-based material wafer, and the current density is 3A / dm 2 , the deposition time is 15min, the plating solution temperature is 50℃, and an N-type bismuth telluride-based material wafer containing an interface barrier layer is obtained. The EDS spectrum test verifies the proportion of metal elements in the coating, as shown in Table 1.

[0072] Table 1 EDS spectrum element content analysis of different Ni-Co-W coatings on bismuth telluride-based material wafers prepared in Example 3

[0073] Sample No. Ni content / % Co element content / % W element content / % 1 90.91 6.04 3.05 2 87.67 9.12 3.21 3 84.82 12.20 2.98 4 75.25 21.71 3.04

[0074] Thermal stability test

[0075] The N-type bismuth telluride material plated with Ni-Co-W in step 2 and the Cu electrode were reflow soldered with SAC305 solder paste to obtain n-Bi2Te3 / Ni-Co-W / SAC305 / Cu thermoelectric junction. The thermoelectric junction sample was placed in a quartz tube, vacuum-sealed, and placed in an annealing furnace for aging treatment at an aging temperature of 150°C for 1 day, 2 days, 4 days, and 8 days, respectively.

[0076] The interface contact resistance of the finally obtained n-Bi2Te3 / Ni-Co-W / SAC305 / Cu thermoelectric junction was tested, and the test results are shown in Figure 6From Table 2, we can see that for the thermoelectric junction samples with Co content of 0%, 6% and 9%, the interface contact resistivity increases significantly, and with the increase of Co content, the increase of interface contact resistivity becomes slow; for samples with Co content greater than 10% (12%, 21%), the Ni-Co-W coating can more effectively prevent the reaction and diffusion between the interfaces, and the interface contact resistance increases slowly and remains at a lower value.

[0077] Comparative Example 1

[0078] Step 1, pre-treating the N-type bismuth telluride-based material wafer before plating, including metallographic sandpaper polishing, using acetone solution to degrease the wafer surface, using pickling solution to pickle and etch the wafer surface for 4 minutes, and using deionized water to ultrasonically clean the wafer for 5 minutes. The volume ratio of nitric acid, sulfuric acid and deionized water in the pickling solution is 1:1:4, wherein the nitric acid is 68% concentrated nitric acid by mass, and the sulfuric acid is 98% concentrated sulfuric acid by mass.

[0079] Step 2, the N-type bismuth telluride-based material wafer that has been pre-treated before plating in step 1 is heated in a water bath in an electroplating solution while performing direct current electrodeposition to prepare a Ni coating on the wafer. The formula of the electroplating solution is: 100g / L nickel sulfate hexahydrate, 30g / L citric acid, 40g / L sodium citrate, 0.4g / L sodium dodecyl sulfate, and 20g / L boric acid. The electroplating process parameters are: the anode is a nickel plate, the cathode is an N-type bismuth telluride-based material wafer, and the current density is 1.5A / dm 2 , the deposition time is 15 minutes, the plating solution temperature is 50°C, and an N-type bismuth telluride-based material wafer containing an interface barrier layer is obtained.

[0080] The N-type bismuth telluride material plated with Ni in step 2 and the Cu electrode were reflow soldered with SAC305 solder paste to obtain n-Bi2Te3 / Ni / SAC305 / Cu thermoelectric junction. The thermoelectric junction sample was placed in a quartz tube, vacuum-sealed, and placed in an annealing furnace for aging treatment at a temperature of 150°C for 1 day, 2 days, 4 days, and 8 days, respectively.

[0081] The interface contact resistance of the finally obtained n-Bi2Te3 / Ni / SAC305 / Cu thermoelectric junction was tested, and the test results are shown in Figure 7 As shown in Table 2, it can be seen that the interfacial contact resistivity of the thermoelectric junction with Ni plating increases rapidly with the extension of aging time.

[0082] Comparative Example 2

[0083] Step 1, pre-treating the N-type bismuth telluride-based material wafer before plating, including metallographic sandpaper polishing, using acetone solution to degrease the wafer surface, using pickling solution to pickle and etch the wafer surface for 4 minutes, and using deionized water to ultrasonically clean the wafer for 5 minutes. The volume ratio of nitric acid, sulfuric acid and deionized water in the pickling solution is 1:1:4, wherein the nitric acid is 68% concentrated nitric acid by mass, and the sulfuric acid is 98% concentrated sulfuric acid by mass.

[0084] Step 2, the N-type bismuth telluride-based material wafer that has been pre-treated before plating in step 1 is heated in a water bath in an electroplating solution while performing direct current electrodeposition to prepare a Ni-Co-Cr coating on the wafer. The total molar amount of nickel salt, cobalt salt and tungsten salt in the electroplating solution is 100%, wherein the molar proportion of nickel salt is 77%, the molar proportion of cobalt salt is 20%, and the molar proportion of chromium salt is 3%.

[0085] The formula of the electroplating solution is: 80g / L nickel sulfate hexahydrate, 6g / L cobalt sulfate, 20g / L chromium chloride hexahydrate, 20g / L citric acid, 50g / L sodium citrate, 0.4g / L sodium dodecyl sulfate, 20g / L boric acid. The electroplating process parameters are: the anode is a nickel plate, the cathode is a P-type bismuth telluride-based material wafer, and the current density is 2A / dm 2 , the deposition time is 15 minutes, the plating solution temperature is 30°C, and an N-type bismuth telluride-based material wafer containing an interface barrier layer is obtained.

[0086] The N-type bismuth telluride material plated with Ni-Co-Cr in step 2 and the Cu electrode were reflow soldered with SAC305 solder paste to obtain n-Bi2Te3 / Ni-Co-Cr / SAC305 / Cu thermoelectric junction. The thermoelectric junction sample was placed in a quartz tube, vacuum-sealed, and placed in an annealing furnace for aging treatment at an aging temperature of 150°C for 1 day, 2 days, 4 days, and 8 days, respectively.

[0087] The interface contact resistance of the finally obtained n-Bi2Te3 / Ni-Co-Cr / SAC305 / Cu thermoelectric junction was tested, and the test results are shown in Figure 7 From Table 2, we can see that the interface thermal stability and interface contact resistivity of the thermoelectric junction with Ni-Co-Cr coating increase rapidly with the extension of aging time, and the effect is far inferior to that of the thermoelectric junction in the embodiment.

[0088] Table 2 Interface contact resistance of thermoelectric junctions prepared in Examples and Comparative Examples at different aging times

[0089]

[0090] Application Examples

[0091] Step 1: Cut the N-type and P-type bismuth telluride material wafers coated with the Ni-Co-W alloy interface barrier layer prepared in Example 1 and Example 2 into 2×2×3 mm 3 of thermoelectric particles.

[0092] Step 2: SAC305 solder paste is coated on both ends of the thermoelectric particles in step 1, and the surfaces are connected to the copper-clad ceramic substrate, and then placed in a tube furnace for reflow soldering to prepare a thermoelectric device containing a Ni-Co-W coating.

[0093] The prepared thermoelectric device was placed in an annealing furnace for aging treatment at a temperature of 150° C. The aging times were 1 day, 2 days, 4 days, and 8 days, respectively.

[0094] The internal resistance of thermoelectric devices with different aging times was tested. The results are as follows: Figure 8 As shown in the figure, compared with conventional thermoelectric devices containing Ni coating, the internal resistance of thermoelectric devices containing Ni-Co-W coating increases more slowly and has better thermal stability.

Claims

1. An interface barrier layer for a bismuth telluride-based thermoelectric device, characterized in that: The interface barrier layer is a Ni-Co-W alloy coating, wherein the molar proportion of the Ni element is 70-93%, the molar proportion of the Co element is 6-25%, and the molar proportion of the W element is 1-5%.

2. The method for preparing an interface barrier layer of a bismuth telluride-based thermoelectric device according to claim 1, characterized in that: Includes steps: Step 1, grinding, degreasing, pickling and etching, and ultrasonic cleaning of the bismuth telluride-based material wafer; Step 2, placing the treated bismuth telluride-based material wafer in an electroplating solution for electrodeposition to form an interface barrier layer on the wafer surface; The electroplating solution comprises nickel salt, cobalt salt and tungsten salt. Taking the total molar amount of nickel salt, cobalt salt and tungsten salt as 100%, the molar proportion of nickel salt is 70-93%, the molar proportion of cobalt salt is 6-25%, and the molar proportion of tungsten salt is 1-5%.

3. The method for preparing an interface barrier layer of a bismuth telluride-based thermoelectric device according to claim 2, characterized in that: The nickel salt includes one or more of nickel sulfate, nickel chloride, nickel sulfamate and hydrates thereof; The cobalt salt includes one or more of cobalt sulfate, cobalt chloride, cobalt nitrate and hydrates thereof; The tungsten salt includes one or more of sodium tungstate and its hydrate.

4. The method for preparing an interface barrier layer of a bismuth telluride-based thermoelectric device according to claim 2, characterized in that: The electroplating solution also includes a pH buffer, a complexing agent and a surfactant.

5. The method for preparing an interface barrier layer of a bismuth telluride-based thermoelectric device according to claim 2, characterized in that: During electrodeposition, the bismuth telluride-based material wafer serves as the cathode and the nickel plate serves as the anode.

6. The method for preparing an interface barrier layer of a bismuth telluride-based thermoelectric device according to claim 2, characterized in that: The current density during electrodeposition is 1 to 3 A / dm 2 The deposition time is 10 to 20 minutes, and the plating solution temperature is 40 to 50°C.

7. The method for preparing an interface barrier layer of a bismuth telluride-based thermoelectric device according to claim 2, characterized in that: The pH buffer includes one or more of citric acid and boric acid; The complexing agent includes one or more of sodium citrate and sodium acetate; The surfactant includes one or more of sodium dodecyl sulfate and sodium dodecylbenzene sulfonate.

8. The method for preparing an interface barrier layer of a bismuth telluride-based thermoelectric device according to claim 2, characterized in that: The bismuth telluride-based material wafer includes N-type or P-type bismuth telluride-based material.

9. The method for preparing an interface barrier layer of a bismuth telluride-based thermoelectric device according to claim 2, characterized in that: The electroplating solution comprises 20-120 g / L of nickel salt, 5-10 g / L of cobalt salt, 2-10 g / L of tungsten salt, 10-60 g / L of pH buffer, 40-60 g / L of complexing agent and 0.2-0.5 g / L of surfactant.

10. A bismuth telluride-based thermoelectric device, characterized in that: The invention comprises a ceramic substrate, an electrode and a bismuth telluride-based thermoelectric material with an interface barrier layer on the surface, wherein the interface barrier layer on the surface of the bismuth telluride-based thermoelectric material is prepared on the surface of the thermoelectric material by the preparation method according to any one of claims 2 to 9.

Images