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

Abstract

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

Description

TECHNICAL FIELD

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

[0002] Thermoelectric devices are devices that directly convert electrical energy and thermal energy into each other, and have important application value in the fields of aerospace, new energy, electronic communication, etc. Bismuth telluride material is one of the earliest discovered semiconductor thermoelectric materials, which exhibits excellent thermoelectric performance near room temperature and becomes the only commercialized thermoelectric material at present.

[0003] At present, the demand for new refrigeration technology in the artificial intelligence and big data storage industry is continuously growing, and higher requirements are put forward for the thermal stability of thermoelectric refrigeration devices. At present, in the field of electronic chip heat dissipation, the working environment temperature of thermoelectric refrigeration devices is 70-150℃, which puts higher requirements on the high-temperature service stability of thermoelectric refrigeration devices.

[0004] The bismuth telluride-based thermoelectric device mainly consists of a ceramic substrate, a metal electrode, a solder layer, an interface barrier layer and a thermoelectric material. The interface barrier layer, as an important part of the thermoelectric device, is used to prevent diffusion and reaction between the solder and the electrode material and the thermoelectric material, and to ensure the stability of the thermoelectric device during service. However, with the increase of working temperature and long-term service at high temperature, the interface barrier layer 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, developing a new type of interface barrier layer material is the key to preparing high-performance and high-reliability bismuth telluride-based thermoelectric devices.

[0005] CN113860873A discloses a preparation method of a bismuth telluride thermoelectric device, which comprises: mixing appropriate amounts of Ni powder raw material and C powder raw material, ball milling to obtain Ni-C mixed powder; filling appropriate amount of bismuth telluride powder in a mold and pre-pressing to form a bismuth telluride thermoelectric material layer; drying the Ni-C mixed powder and filling it into the mold and uniformly stacking it on the bismuth telluride thermoelectric material layer for secondary pre-pressing to form a Ni-C barrier layer; SPS sintering the bismuth telluride thermoelectric material layer and the Ni-C barrier layer, and cooling to obtain a bismuth telluride thermoelectric device. By selecting C raw material to replace part of Ni raw material, the diffusion and reaction of Ni element and Te element at the interface between the bismuth telluride hot spot material layer and the barrier layer can be reduced to some extent, but the effect is not obvious, and the interface contact resistance is high.

[0006] CN 111211214 A An interface barrier layer for a half-Heusler alloy thermoelectric material, the half-Heusler alloy thermoelectric material has a chemical formula of ABX, wherein A is at least one of Sc, Y, Ti, Zr, Hf, V, Nb, Ta, B is at least one of Fe, Co, Ni, Ru, Rh, Pd, Os, Ir, Pt, and X is at least one of Sn, Sb, and Bi; the interface barrier layer is composed of a full-Heusler alloy with the same elements as the half-Heusler alloy thermoelectric material, or a single substance of the interstitial metal element B of the half-Heusler alloy thermoelectric material ABX. The interface barrier layer material matches the lattice parameters and thermal expansion coefficients of the half-Heusler alloy matrix, and the device cracking failure problem caused by the interface thermal stress is reduced to the maximum extent. However, the composition of the interface barrier layer is more demanding, and needs to match the lattice parameters and thermal expansion coefficients of the half-Heusler alloy matrix. SUMMARY

[0007] The present application aims at the problem of poor thermal stability of the interface barrier layer of thermoelectric materials and the performance deterioration of devices at high temperatures, and provides a nickel-based alloy interface barrier layer which can effectively prevent the reaction between the thermoelectric material and the interface barrier layer at a higher temperature, reduce the interface contact resistance, and maintain the stability of the thermoelectric device serving at a higher temperature for a long time.

[0008] To achieve the above-mentioned purpose, the technical scheme adopted by the present application is:

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

[0010] In the present application, Co and W elements are reasonably designed and added on the basis of the commonly used Ni plating layer to inhibit the diffusion of the elements of the interface barrier layer, and the obtained Ni-Co-W alloy plating layer has very small contact resistance as the interface barrier layer of the thermoelectric device, which is less than 4 mu omega·cm 2 Even after 8 days of 150 DEG C aging treatment, the contact resistance only increases to 3.81 mu omega·cm 2 At this contact resistance, the device performance can still reach more than 90% of the material performance, which is beneficial to the long-term service of the thermoelectric device at a higher temperature.

[0011] Preferably, the molar percentage of Ni element is 70-83%, the molar percentage of Co element is 10-22%, and the molar percentage of W element is 1-5%. The plating layer with Co content of more than 10% has more excellent thermal stability.

[0012] Preferably, the thickness of the Ni-Co-W alloy coating is 2-10 μm, and the thinner the thickness of the interface barrier layer, the more beneficial to obtain small interface resistance, thereby reducing the loss of electric energy on the interface; but a certain thickness of the electrode can prevent the diffusion of interface elements during the use of the thermoelectric device at high temperature, thereby improving the service life of the device.

[0013] The application further provides a preparation method of the interface barrier layer of the bismuth telluride-based thermoelectric device, comprising the steps of:

[0014] Step 1, polishing, oil removal, acid pickling corrosion 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 wafer surface;

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

[0017] In the application, the Ni-Co-W alloy coating is prepared by electrodeposition, and 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 substrate.

[0018] Preferably,

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

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

[0021] The tungsten salt comprises one or more of sodium tungstate and hydrates thereof.

[0022] The electroplating solution further comprises a pH buffer, a complexing agent and a surfactant.

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

[0024] During the electrodeposition, the current density is 1-3 A / dm 2 , the deposition time is 10-20 min, and the temperature of the electroplating solution is 40-50℃.

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

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

[0027] The surfactant includes one or more of sodium dodecyl sulfate, sodium dodecyl benzene 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 application also provides a bismuth telluride-based thermoelectric device including a ceramic substrate, an electrode, and a bismuth telluride-based thermoelectric material with an interface barrier layer on the surface of the thermoelectric material, 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 application has the following beneficial effects:

[0032] (1) The process of the application is simple to operate, the conditions are easy to control, and the repeatability is good. The interface barrier layer obtained is well combined with 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 utilized.

[0033] (2) The Ni-Co-W alloy interface barrier layer in the application can effectively prevent the reaction between the thermoelectric material matrix and the interface material, inhibit the generation of the interface reaction layer, effectively reduce the interface contact resistance of the thermoelectric device at a higher temperature, make the thermoelectric device have higher thermal stability, and greatly improve the service life of the device.

[0034] (3) The Ni-Co-W alloy interface barrier layer in the application can be applied to N-type bismuth telluride-based material and P-type bismuth telluride-based material at the same time, so that the preparation process flow of the bismuth telluride-based thermoelectric device is simplified, and the large-scale production is suitable. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 Figure 4 is a microstructure diagram of the n-Bi2Te3 / Ni-Co-W / SAC305 / Cu thermoelectric junction interface prepared in Example 1.

[0036] Figure 2 Figure 5 is a diagram of the interface contact resistivity of the thermoelectric junction changing with the aging time in Examples 1 and 2.

[0037] Figure 3 Figure 6 is an XRD spectrum of the n-Bi2Te3 material wafer plated with the Ni-Co-W interface barrier layer and subjected to different thermal aging in Example 1.

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

[0039] Figure 5 Figure 4 is an XRD pattern of the p-Bi2Te3 material wafer with a Ni-Co-W interface barrier layer after different thermal aging in Example 2.

[0040] Figure 6 Figure 5 is a plot of the interface contact resistivity of the thermoelectric junction versus thermal aging time in Example 3.

[0041] Figure 7 Figure 6 is a plot of the 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 versus thermal aging time prepared in Example 1 and Comparative Example 2 and Comparative Example 1.

[0042] Figure 8 Figure 7 is a plot of the device resistance of the thermoelectric device versus thermal aging time in the Application Example. DETAILED DESCRIPTION

[0043] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and should not be used to limit the present application. Any modification or equivalent replacement made by those skilled in the art based on the technical solutions of the present application without departing from the spirit and scope of the present application should be covered within the protection scope of the present application.

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

[0045] Example 1

[0046] Step 1, the N-type bismuth telluride-based material wafer was pre-treated before plating: including polishing with metallographic sandpaper, removing oil from the wafer surface with an acetone solution, acid washing and etching the wafer surface with an acid washing solution for 4 min, and ultrasonic cleaning the wafer with deionized water for 5 min. The acid washing 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%.

[0047] Step 2, the N-type bismuth telluride-based material wafer after pre-plating pretreatment in step 1 is subjected to water bath heating in the electroplating solution while direct current electrodeposition is carried out, and a Ni-Co-W alloy plating layer is prepared on the wafer. In the electroplating solution, the total molar amount of nickel salt, cobalt salt and tungsten salt 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: nickel sulfate hexahydrate 80 g / L, cobalt sulfate 6 g / L, sodium tungstate 3 g / L, citric acid 20 g / L, sodium citrate 50 g / L, sodium dodecyl sulfate 0.4 g / L, boric acid 20 g / L. The electroplating process parameters are: the anode is a nickel plate, the cathode is the N-type bismuth telluride-based material wafer, the current density is 3 A / dm 2 , the deposition time is 15 min, and the plating solution temperature is 50℃, to obtain the N-type bismuth telluride-based material wafer containing an interface barrier layer.

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

[0050] The interface micro-morphology of the 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 4-8 μm, 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 is tested, and the test results are shown by the circular points in Figure 2 , which shows that the contact resistivity is 3.33 μΩ·cm 2 , the resistivity is very low, which fully proves 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 the Ni-Co-W alloy interface barrier layer prepared in Example 1 and the n-Bi2Te3 / Ni-Co-W / SAC305 / Cu thermoelectric junction sample are respectively loaded into a quartz tube, vacuumized and sealed, and then placed in an annealing furnace for aging treatment, the aging temperature is 150℃, and the aging time is 1 day, 2 days, 4 days and 8 days respectively.

[0054] X-ray diffractometer (XRD) of PANalytical (Aries DY866) of Holland was used to analyze the phase of the bismuth telluride material wafer after aging treatment, as shown in Figure 3 From the figure, it can be seen that even after 8 days of aging treatment, the N-type bismuth telluride material and the Ni-Co-W interface barrier layer do not have interface reaction and do not produce NiTe reaction layer.

[0055] The interface contact resistivity test results of the thermoelectric junction of different aging time are shown in Figure 2 The circular symbol and Table 2, from the figure, it can be seen that even when the aging time is 8 days, the interface contact resistivity value is only 3.81 μΩ·cm 2 , and the interface performance is still good.

[0056] Example 2

[0057] Step 1, the P-type bismuth telluride-based material wafer was pretreated before plating, including polishing with metallographic sandpaper, removing oil from the surface of the wafer with acetone solution, acid washing and etching the surface of the wafer with acid washing solution for 5 min, and ultrasonic cleaning the wafer with deionized water for 5 min. The acid washing 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 pretreated before plating in step 1 was subjected to direct current electrodeposition while being heated in a water bath in the plating solution to prepare a Ni-Co-W alloy plating layer on the wafer. In the plating solution, the total molar amount of nickel salt, cobalt salt and tungsten salt 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 plating solution is: nickel sulfate hexahydrate 80 g / L, cobalt sulfate 6 g / L, sodium tungstate 3 g / L, citric acid 20 g / L, sodium citrate 50 g / L, sodium dodecyl sulfate 0.4 g / L, boric acid 20 g / L. The anode is a nickel plate, the cathode is a P-type bismuth telluride-based material wafer, the current density is 3 A / dm 2 , the deposition time is 15 min, and the plating solution temperature is 50℃, to obtain an N-type bismuth telluride-based material wafer with an interface barrier layer.

[0060] The P-type bismuth telluride material with Ni-Co-W plating layer in step 2 and the Cu electrode were soldered by reflow soldering with SAC305 tin paste to obtain a p-Bi2Te3 / Ni-Co-W / SAC305 / Cu thermoelectric junction.

[0061] The interface micro-morphology of the 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 the 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 in day 0 in the figure shows that the contact resistivity thereof is 4.49 μΩ·cm 2 , which fully proves 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 the Ni-Co-W alloy interface barrier layer prepared in Example 2 and the p-Bi2Te3 / Ni-Co-W / SAC305 / Cu thermoelectric junction sample were respectively loaded into a quartz tube, vacuum sealed, and placed in an annealing furnace for aging treatment, the aging temperature was 150 ℃, and the aging time was 1 day, 2 days, 4 days, and 8 days, respectively.

[0065] The bismuth telluride material wafer after aging treatment was subjected to phase analysis by using a Netherlands PANalytical (Aries DY866) X-ray polycrystalline diffractometer (XRD), as shown in Figure 5 and Table 2. It can be seen from the figure that even after 8 days of aging treatment, the P-type bismuth telluride material and the Ni-Co-W interface barrier layer do not have interface reaction and do not produce a NiTe reaction layer.

[0066] The interface contact resistivity test results of the thermoelectric junction with different aging times are shown in Figure 2 and 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 5.21 μΩ·cm 2 , and the interface performance is still good.

[0067] Example 3

[0068] Step 1, the P-type bismuth telluride material wafer was pretreated before plating, including polishing with metallographic sandpaper, removing oil on the wafer surface with an acetone solution, acid washing and etching the wafer surface with an acid washing solution for 5 min, and ultrasonic cleaning the wafer with deionized water for 5 min. The nitric acid, sulfuric acid and deionized water in the acid washing solution are 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 after pre-plating pretreatment in step 1 is subjected to water bath heating in an electroplating solution while direct current deposition is carried out, so as to prepare Ni-Co-W plating layers with Co element contents of 6%, 9%, 12% and 21% on the wafer. In the electroplating solution, the total molar amount of nickel salt, cobalt salt and tungsten salt is 100%, wherein the molar proportion of the nickel salt is adjusted to 91%, 88%, 85% and 76%, the molar proportion of the cobalt salt is 6%, 9%, 12% and 21%, and the molar proportion of the tungsten salt is 3%.

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

[0071] The anode is a nickel plate, the cathode is the N-type bismuth telluride-based material wafer, the current density is 3 A / dm 2 , the deposition time is 15 min, and the plating solution temperature is 50℃, so as to obtain the N-type bismuth telluride-based material wafer with an interface barrier layer. The plating layer is verified by EDS energy spectrum test for the proportion of metal elements, and the specific contents are shown in Table 1.

[0072] Table 1 EDS energy spectrum element content analysis of different Ni-Co-W plating layers of the bismuth telluride-based material wafer prepared in Example 3

[0073] Sample No. Ni element 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 the Ni-Co-W plating layer in step 2 and the Cu electrode are soldered by reflow soldering through SAC305 tin paste to obtain an n-Bi2Te3 / Ni-Co-W / SAC305 / Cu thermoelectric junction. The thermoelectric junction sample is loaded into a quartz tube, vacuum sealed, and placed in an annealing furnace for aging treatment, with an aging temperature of 150℃ and an aging time of 1 day, 2 days, 4 days and 8 days.

[0076] The interface contact resistance of the finally obtained n-Bi2Te3 / Ni-Co-W / SAC305 / Cu thermoelectric junction is tested, and the test results are shown in Figure 6As shown in Table 2, it can be seen that the interface contact resistivity of the thermoelectric junction samples with Co content of 0%, 6% and 9% increases significantly, and the increase rate of the interface contact resistivity becomes slow with the increase of the Co content; for the samples with Co content greater than 10% (12%, 21%), the Ni-Co-W plating layer 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: The N-type bismuth telluride-based material wafer was pre-plated and pretreated, including polishing with metallographic sandpaper, removing oil from the wafer surface with an acetone solution, acid pickling and etching the wafer surface with an acid pickling solution for 4 min, and ultrasonic cleaning the wafer with deionized water for 5 min. The acid pickling solution was prepared by mixing nitric acid, sulfuric acid and deionized water in a volume ratio of 1:1:4, wherein the nitric acid was concentrated nitric acid with a mass fraction of 68%, and the sulfuric acid was concentrated sulfuric acid with a mass fraction of 98%.

[0079] Step 2: The N-type bismuth telluride-based material wafer pre-plated and pretreated in step 1 was subjected to direct current deposition while being heated in a water bath in an electroplating solution to prepare a Ni plating layer on the wafer. The electroplating solution was prepared by mixing 100 g / L of nickel sulfate hexahydrate, 30 g / L of citric acid, 40 g / L of sodium citrate, 0.4 g / L of sodium dodecyl sulfate and 20 g / L of boric acid. The electroplating process parameters were as follows: the anode was a nickel plate, the cathode was the N-type bismuth telluride-based material wafer, the current density was 1.5 A / dm 2 , the deposition time was 15 min, and the plating solution temperature was 50°C. Thus, an N-type bismuth telluride-based material wafer with an interface barrier layer was obtained.

[0080] The N-type bismuth telluride material plated with the Ni plating layer in step 2 and a Cu electrode were soldered by reflow soldering with SAC305 tin paste to obtain an n-Bi2Te3 / Ni / SAC305 / Cu thermoelectric junction. The thermoelectric junction sample was sealed in a quartz tube after being vacuumized, and was 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.

[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 Table 2 and Table 3. Figure 7 As shown in Table 2 and Table 3, it can be seen that the interface contact resistivity of the thermoelectric junction with the Ni plating layer increases rapidly with the extension of the aging time.

[0082] Comparative Example 2

[0083] Step 1, the N-type bismuth telluride-based material wafer is pre-plated and pretreated, including polishing with metallographic sandpaper, removing oil on the wafer surface with an acetone solution, acid washing and etching the wafer surface with an acid solution for 4 minutes, and ultrasonic cleaning the wafer with deionized water for 5 minutes. The acid 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%.

[0084] Step 2, the N-type bismuth telluride-based material wafer pre-plated and pretreated in step 1 is subjected to direct current deposition while being heated in a water bath in an electroplating solution to prepare a Ni-Co-Cr plating layer on the wafer. In the electroplating solution, the total molar amount of nickel salt, cobalt salt and tungsten salt 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: nickel sulfate hexahydrate 80 g / L, cobalt sulfate 6 g / L, chromium chloride hexahydrate 20 g / L, citric acid 20 g / L, sodium citrate 50 g / L, sodium dodecyl sulfate 0.4 g / L, boric acid 20 g / L. The electroplating process parameters are: the anode is a nickel plate, the cathode is a P-type bismuth telluride-based material wafer, the current density is 2 A / dm 2 , the deposition time is 15 minutes, and the plating solution temperature is 30℃. An N-type bismuth telluride-based material wafer containing an interface barrier layer is obtained.

[0086] The N-type bismuth telluride material plated with a Ni-Co-Cr plating layer in step 2 and a Cu electrode are welded by reflow soldering with SAC305 tin paste to obtain an n-Bi2Te3 / Ni-Co-Cr / SAC305 / Cu thermoelectric junction. The thermoelectric junction sample is placed in a quartz tube and sealed by vacuumizing, and then placed in an annealing furnace for aging treatment. The aging temperature is 150℃, and the aging time is 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 is tested, and the test results are shown in Figure 7 and Table 2. It can be seen that the interface thermal stability of the thermoelectric junction with a Ni-Co-Cr plating layer increases rapidly with the extension of the aging time, and the effect is far inferior to that of the thermoelectric junction of the embodiment.

[0088] Table 2 Interface contact resistance of thermoelectric junctions prepared in the embodiment and comparative examples at different aging times

[0089]

[0090] Application Example

[0091] Step 1: The N-type and P-type bismuth telluride material wafers plated with Ni-Co-W alloy interface barrier layer prepared in Example 1 and Example 2 were cut into 2x2x3mm 3 thermoelectric particles using a wire cutting machine.

[0092] Step 2: The surfaces of the thermoelectric particles in Step 1 were coated with SAC305 tin paste, and connected with a copper clad ceramic substrate, and then placed in a tube furnace for reflow soldering to prepare a thermoelectric device containing a Ni-Co-W plating layer.

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

[0094] The internal resistance of the thermoelectric device aged for different times was tested, and the results are shown in Figure 8 From the figure, it can be seen that compared with the conventional thermoelectric device containing a Ni plating layer, the internal resistance of the thermoelectric device containing a Ni-Co-W plating layer rises more slowly, and has better thermal stability.

Claims

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

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

3. The method of claim 2, wherein the method further comprises: The nickel salt comprises one or more of nickel sulfate, nickel chloride, nickel sulfamate, and hydrates thereof; The cobalt salt comprises one or more of cobalt sulfate, cobalt chloride, cobalt nitrate, and hydrates thereof; The tungsten salt comprises one or more of sodium tungstate and hydrates thereof.

4. The method of claim 2, wherein the method further comprises: The electroplating solution further comprises a pH buffer, a complexing agent, and a surfactant.

5. The method of claim 2, wherein the method further comprises: The bismuth telluride-based material wafer serves as the cathode during electrodeposition, and a nickel plate serves as the anode.

6. The method of claim 2, wherein the method further comprises: The current density during electrodeposition is 1-3 A / dm 2 , the deposition time is 10-20 min, and the plating solution temperature is 40-50°C.

7. The method of producing an interface barrier layer for a bismuth telluride-based thermoelectric device according to claim 4, wherein The pH buffer comprises one or more of citric acid and boric acid; The complexing agent comprises one or more of sodium citrate and sodium acetate; The surfactant comprises one or more of sodium dodecyl sulfate and sodium dodecyl benzene sulfonate.

8. The method of claim 2, wherein the method further comprises: The bismuth telluride-based material wafer comprises N-type or P-type bismuth telluride-based material.

9. The method of producing an interface barrier layer for a bismuth telluride-based thermoelectric device according to claim 2, wherein 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 by, The ceramic substrate, the electrode, and the bismuth telluride-based thermoelectric material with the interface barrier layer on the surface are prepared by the method of any one of claims 2-9.

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