BiCuSeO-based thermoelectric device and preparation method thereof

Abstract

The invention discloses a BiCuSeO-based thermoelectric device and a preparation method of the BiCuSeO-based thermoelectric device. On one hand, the invention provides the high-performance BiCuSeO-based thermoelectric material, and the thermoelectric material is prepared by mixing elements with the BiCuSeO-based thermoelectric material and carrying out ball milling and high-temperature solid-phase reaction; on the other hand, the invention provides a BiCuSeO-based thermoelectric device and a preparation method thereof, in the preparation process of the thermoelectric device, the BiCuSeO-based thermoelectric material is prepared into a thermoelectric block body by adopting a spark plasma sintering (SPS) technology, and then the thermoelectric block body and a base material are welded through a high-temperature welding technology to prepare the thermoelectric device. In order to inhibit element diffusion between a device substrate and a thermoelectric block, an element barrier layer is prepared on a welding interface of the thermoelectric block through a magnetron sputtering technology. The interface resistivity of the prepared BiCuSeO-based thermoelectric device is only 5.06 m omega / cm < 2 >, and the interface shear force is as high as 15.13 MPa.

Description

Technical Field

[0001] The present invention relates to the technical field of new energy material preparation, and in particular to a BiCuSeO-based thermoelectric device and a preparation method thereof. Background Art

[0002] Thermoelectric materials are functional materials that can directly convert heat and electricity based on the Seebeck effect and the Peltier effect. As long as there is a temperature gradient, the carriers inside will have a corresponding special distribution to achieve temperature difference power generation. Its power generation method is completely different from traditional technology. It does not require mechanical moving parts, has no vibration or noise, no emissions, and is highly reliable. It has unique advantages in recycling low-grade industrial waste heat and has received great attention from countries around the world. If the temperature difference power generation technology is used for the recovery and utilization of low-grade industrial waste heat, it is conservatively estimated that more than 400 billion kWh of energy will be saved each year, which is about the annual power generation of four Three Gorges power stations. The direct economic benefits will exceed 300 billion yuan, and the economic and social benefits of emission reduction and environmental protection are even more difficult to estimate.

[0003] However, the current application of thermoelectric materials for temperature difference power generation is still limited to a few special fields such as aerospace and military industry where cost is not taken into account. The main obstacles are the following four aspects: 1) Thermoelectric conversion efficiency is not high. The core problem is that the ZT value of thermoelectric materials is not high; 2) Thermoelectric material system problems and the cost of their preparation and processing. The thermoelectric materials currently used use a large amount of rare or toxic chemical elements such as cobalt, antimony, lead, and rare earths. In addition, the preparation process of thermoelectric materials is energy-intensive and has a long cycle. For example, the preparation process of medium-low temperature bismuth telluride system and medium-high temperature filled cobaltite system thermoelectric materials requires long annealing treatment, and the cost remains high; 3) The preparation process of thermoelectric devices is cumbersome and complex, with large material loss and low yield. Therefore, the development of efficient, stable, and low-cost thermoelectric materials and corresponding thermoelectric device preparation methods is the current research focus in the field of thermoelectric devices. Summary of the invention

[0004] Based on this, in order to solve the problems in the prior art of low thermoelectric conversion efficiency of thermoelectric materials, difficulty in welding of BiCuSeO-based thermoelectric devices, narrow welding temperature range, severe element diffusion and severe performance attenuation, the present invention provides element-doped BiCuSeO-based thermoelectric materials and corresponding thermoelectric devices, and the specific technical solutions are as follows:

[0005] A BiCuSeO-based thermoelectric device, the BiCuSeO-based thermoelectric device is a sandwich structure, the sandwich structure is a copper electrode / soldering piece / thermoelectric block body / soldering piece / copper electrode arranged in sequence; wherein the thermoelectric block body is a thermoelectric block body prepared by element-doped BiCuSeO-based thermoelectric material, and the interface of the soldering piece / thermoelectric block body has an element diffusion barrier layer.

[0006] In addition, the present invention also provides a method for preparing a BiCuSeO-based thermoelectric device, the preparation method comprising the following steps:

[0007] 1) mixing a bismuth source, a copper source, a selenium source and a doping element source, and then preparing an element-doped BiCuSeO-based thermoelectric material by ball milling combined with a high-temperature solid phase reaction method;

[0008] 2) preparing a BiCuSeO-based thermoelectric block by using the element-doped BiCuSeO-based thermoelectric material obtained above through SPS technology;

[0009] 3) A layer of element diffusion barrier layer is prepared on the surface of the BiCuSeO-based thermoelectric block obtained above by magnetron sputtering technology, and then a BiCuSeO-based thermoelectric device with a sandwich structure of copper electrode / welding piece / thermoelectric block / welding piece / copper electrode is prepared by high temperature welding technology.

[0010] Furthermore, in step 1, the bismuth source is at least one of bismuth oxide and bismuth powder.

[0011] Furthermore, in step 1, the copper source is at least one of copper powder and copper oxide.

[0012] Furthermore, in step 1, the selenium source is at least one of selenium powder and selenium dioxide.

[0013] Furthermore, in step 1, the doping element source is at least one of Pb, Yb, Ca, Mo, Ni, Mn, Li, Ga, Ag, and Sb;

[0014] The molecular formula after doping is Bi 1-x M x CuSeO, wherein M is the general term for one or more doping elements, x is the amount of all doping elements, and the value of x is 0.02-0.2.

[0015] Furthermore, in step 1, the ball milling combined with high-temperature solid phase reaction method is a first ball milling treatment-high-temperature solid phase reaction-a second ball milling treatment, wherein the time of the first ball milling treatment and the second ball milling treatment are both 1h-20h, and the atmosphere of the first ball milling treatment and the second ball milling treatment are both argon or nitrogen atmosphere; the time of the high-temperature solid phase reaction is 2h-10h, and the temperature of the high-temperature solid phase reaction is 650℃-750℃.

[0016] Furthermore, in step 2, the sintering temperature of the SPS technology is 650°C-750°C, the pressure is 50Mpa-70Mpa, and the time is 2min-15min.

[0017] Further, in step 3, the temperature of the high temperature welding technology is 500-650°C, and the heating rate is 0.5°C / min-5°C / min;

[0018] The time of the high temperature welding technology is 10min-60min;

[0019] The pressure of the high temperature welding technology is 5Mpa-20Mpa;

[0020] The soldering sheet is a special silver-copper soldering sheet, and its composition is CuAg 20 P5.

[0021] Furthermore, in step 3, the element diffusion barrier layer is at least one of a Mo element layer, a Ni element layer, a Ti element layer, and a Fe element layer;

[0022] The thickness of the element blocking layer is 500nm-6000nm.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] 1. The present invention optimizes the preparation of raw materials to obtain element-doped BiCuSeO-based thermoelectric materials, which can be used as ideal thermoelectric materials to develop related thermoelectric devices. The interface resistivity of the BiCuSeO-based thermoelectric device prepared by the present invention is only 5.06 mΩ / cm 2 , the interface shear force is as high as 15.13MPa, and it has excellent thermoelectric conversion efficiency.

[0025] 2. The raw materials for the preparation of the present invention are safe and low in cost. The preparation process is faster and shorter than that of the prior art. The overall process is simple and suitable for industrial-scale production. It can generally solve the problems in the prior art of low thermoelectric conversion efficiency of thermoelectric materials, difficult welding of BiCuSeO-based thermoelectric devices, narrow welding temperature range, severe element diffusion and severe performance attenuation. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 Schematic diagram of the preparation process of the BiCuSeO-based thermoelectric device described in Example 1 of the present invention;

[0027] Figure 2 This is a graph showing the interface resistance of the thermoelectric device prepared in Example 1 of the present invention. DETAILED DESCRIPTION

[0028] In order to make the purpose, technical solution and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with its embodiments. It should be understood that the specific implementation methods described herein are only used to explain the present invention and do not limit the protection scope of the present invention.

[0029] In one embodiment of the present invention, a BiCuSeO-based thermoelectric device is a sandwich structure, wherein the sandwich structure is a copper electrode / soldering piece / thermoelectric block / soldering piece / copper electrode arranged in sequence; wherein the thermoelectric block is a thermoelectric block prepared by element-doped BiCuSeO-based thermoelectric material, and an element diffusion barrier layer is provided at the interface of the soldering piece / thermoelectric block.

[0030] In one embodiment, the present invention further provides a method for preparing a BiCuSeO-based thermoelectric device, the preparation method comprising the following steps:

[0031] 1) mixing a bismuth source, a copper source, a selenium source and a doping element source, and then preparing an element-doped BiCuSeO-based thermoelectric material by ball milling combined with a high-temperature solid phase reaction method;

[0032] 2) preparing a BiCuSeO-based thermoelectric block by using the element-doped BiCuSeO-based thermoelectric material obtained above through SPS technology;

[0033] 3) A layer of element diffusion barrier layer is prepared on the surface of the BiCuSeO-based thermoelectric block obtained above by magnetron sputtering technology, and then a BiCuSeO-based thermoelectric device with a sandwich structure of copper electrode / welding piece / thermoelectric block / welding piece / copper electrode is prepared by high temperature welding technology.

[0034] In one embodiment, in step 1, the bismuth source is at least one of bismuth oxide and bismuth powder.

[0035] In one embodiment, in step 1, the copper source is at least one of copper powder and copper oxide.

[0036] In one embodiment, in step 1, the selenium source is at least one of selenium powder and selenium dioxide.

[0037] In one embodiment, in step 1, the doping element source is at least one of Pb, Yb, Ca, Mo, Ni, Mn, Li, Ga, Ag, and Sb;

[0038] The molecular formula after doping is Bi 1-x M x CuSeO, wherein M is the general term for one or more doping elements, x is the amount of all doping elements, and the value of x is 0.02-0.2.

[0039] In one embodiment, the value of x is preferably 0.05-0.15.

[0040] In one embodiment, in step 1, the ball milling combined with high-temperature solid phase reaction method is a first ball milling treatment-high-temperature solid phase reaction-a second ball milling treatment, wherein the time of the first ball milling treatment and the second ball milling treatment are both 1h-20h, and the atmosphere of the first ball milling treatment and the second ball milling treatment are both argon or nitrogen atmosphere; the time of the high-temperature solid phase reaction is 2h-10h, and the temperature of the high-temperature solid phase reaction is 650℃-750℃.

[0041] In one embodiment, the time of the first ball milling treatment and the second ball milling treatment is preferably 5h-15h.

[0042] In one embodiment, the high temperature solid phase reaction time is preferably 3h-6h.

[0043] In one embodiment, in step 2, the sintering temperature of the SPS technology is 650° C.-750° C., the pressure is 50 Mpa-70 Mpa, and the time is 2 min-15 min.

[0044] In one embodiment, in step 3, the temperature of the high temperature welding technology is 500-650°C, and the heating rate is 0.5°C / min-5°C / min;

[0045] The time of the high temperature welding technology is 10min-60min;

[0046] The pressure of the high temperature welding technology is 5Mpa-20Mpa;

[0047] The soldering sheet is a special silver-copper soldering sheet, and its composition is CuAg 20 P5.

[0048] In one embodiment, in step 3, the element diffusion barrier layer is at least one of a Mo element layer, a Ni element layer, a Ti element layer, and a Fe element layer;

[0049] In one embodiment, the thickness of the element blocking layer is 500nm-6000nm. If it is too thin, it cannot effectively block the diffusion of elements, and if it is too thick, it will affect the performance such as interface bonding strength and interface resistance.

[0050] The above scheme obtains the element-doped BiCuSeO-based thermoelectric material, which can be used as an ideal thermoelectric material to develop related thermoelectric devices. The interface resistivity of the BiCuSeO-based thermoelectric device prepared by the present invention is only 5.06 mΩ / cm 2 , the interface shear force is as high as 15.13MPa, and it has excellent thermoelectric conversion efficiency.

[0051] The embodiments of the present invention will be described in detail below with reference to specific examples.

[0052] Embodiment 1:

[0053] A method for preparing a BiCuSeO-based thermoelectric device comprises the following steps:

[0054] According to the chemical formula Bi 0.88 Pb 0.06 Ca 0.03 Yb 0.03 CuSeO, accurately weigh the powders of Bi2O3, Bi, PbO, CaO, Yb2O3, Cu, and Se, and then put the above raw materials into a ball mill, and use nitrogen atmosphere protection, and then use a planetary ball mill to mechanically alloy for 4 hours at a speed of 300r / min, and then drop 40mL of ethanol and continue ball milling for 2 hours to obtain a slurry, and then vacuum dry the slurry at 50°C for 12 hours to obtain a completely dried mixed powder A;

[0055] The mixed powder A was placed in a tubular furnace protected by N2 atmosphere, heated to 700°C at a heating rate of 5°C / min, and kept at 700°C for 5 hours. After cooling, the mixed powder A was placed in a ball mill and 40 mL of ethanol was added. The mixed powder A was ball milled for 3 hours to obtain a slurry. The slurry was then vacuum dried at 50°C for 12 hours to obtain a mixed powder B.

[0056] The mixed powder B obtained above was placed into a graphite mold with a diameter of 15 mm by spark plasma sintering (SPS) technology, and sintered for 5 min under vacuum pressure of 60 MPa and temperature of 998 K to obtain a cylindrical block, which was then cut to obtain Bi of the required size. 0.88 Pb 0.06 Ca 0.03 Yb 0.03 CuSeO thermoelectric block;

[0057] Under the condition of 100W power, the Bi 0.88 Pb 0.06 Ca 0.03 Yb 0.03 The CuSeO thermoelectric block needs to be welded on a Mo barrier layer with a thickness of about 3000nm. Then, the pre-welded parts are assembled according to the structure of copper electrode / welding piece / thermoelectric block / welding piece / copper electrode, and a pressure of 10Mpa is applied to it. The pre-welded parts are heated to 600℃ at a heating rate of 2℃ / min and kept warm for 20min to obtain Cu / CuAg 20 P5 / Mo / Bi 0.88 Pb 0.06 Ca0.03 Yb 0.03 CuSeO structured thermoelectric devices.

[0058] The performance test results show that Bi 0.88 Pb 0.06 Ca 0.03 Yb 0.03 The ZT of CuSeO thermoelectric block can reach 1.0 at 500℃, while that of Cu / CuAg 20 P5 / Mo / Bi 0.88 Pb 0.06 Ca 0.03 Yb 0.03 The initial interface resistivity of the CuSeO thermoelectric device joint is only 1.37 mΩ / cm 2 After 40 hours of use, the highest interface resistivity is only 5.12 mΩ / cm 2 ,like Figure 2 In addition, the shear force of the joint interface is as high as 15.13Mpa and remains stable after 40 hours of use.

[0059] Embodiment 2:

[0060] A method for preparing a BiCuSeO-based thermoelectric device comprises the following steps:

[0061] According to the chemical formula Bi 0.9 Pb 0.06 Yb 0.04 CuSeO, accurately weigh the powders of Bi2O3, Bi, PbO, Yb2O3, Cu, and Se respectively, then put the above raw materials into a ball mill, and use nitrogen atmosphere protection, then use a planetary ball mill, mechanically alloy at a speed of 300r / min for 6h, then drop 40mL of ethanol and continue ball milling for 2h to obtain slurry, and then vacuum dry the slurry at 50°C for 12h to obtain a completely dried mixed powder A;

[0062] The mixed powder A was placed in a tubular furnace protected by N2 atmosphere, heated to 700°C at a heating rate of 5°C / min, and kept at 700°C for 5 hours. After cooling, the mixed powder A was placed in a ball mill and 40 mL of ethanol was added. The mixed powder A was ball milled for 5 hours to obtain a slurry. The slurry was then vacuum dried at 50°C for 12 hours to obtain a mixed powder B.

[0063] The mixed powder B obtained above was placed into a graphite mold with a diameter of 15 mm by spark plasma sintering (SPS) technology, and sintered for 10 min under vacuum pressure of 62 MPa and temperature of 998 K to obtain a cylindrical block, which was then cut to obtain Bi of the required size. 0.9 Pb 0.06 Yb 0.04CuSeO thermoelectric block;

[0064] Under the condition of 100W power, the Bi 0.9 Pb 0.06 Yb 0.04 A Ni barrier layer with a thickness of about 1500nm was sputtered on the surface of the CuSeO thermoelectric block to be welded. Then, the pre-welded parts were assembled according to the structure of copper electrode / welding piece / thermoelectric block / welding piece / copper electrode, and a pressure of 15Mpa was applied to them. Subsequently, the pre-welded parts were heated to 600℃ at a heating rate of 2℃ / min and kept warm for 20min to obtain Cu / CuAg 20 P5 / Mo / Bi 0.9 Pb 0.06 Yb 0.04 CuSeO structured thermoelectric devices.

[0065] The performance test results show that Bi 09 Pb 006 Yb 004 The ZT of CuSeO thermoelectric block can reach 0.94 at 500℃, while that of Cu / CuAg 20 P5 / Mo / Bi 0.9 Pb 0.06 Yb 0.04 The initial interface resistivity of the CuSeO thermoelectric device joint is only 1.82 mΩ / cm 2 After 40 hours of use, the highest interface resistivity is only 6.07 mΩ / cm 2 In addition, the shear force of the joint interface is as high as 14.82Mpa and remains stable after 40 hours of use.

[0066] Embodiment 3:

[0067] A method for preparing a BiCuSeO-based thermoelectric device comprises the following steps:

[0068] The difference between Example 3 and Example 1 is that Example 3 controls the sputtering time in Bi 0.88 Pb 0.06 Ca 0.03 Yb 0.03 The CuSeO thermoelectric block needs to be welded with a 5000nm Mo element barrier layer sputtered on its surface, and the other processes are the same as those in Example 1.

[0069] The initial interface resistivity of the BiCuSeO-based thermoelectric device prepared in Example 3 is 2.03 mΩ / cm 2 The initial welding strength of the joint is 12.37MPa, which is mainly due to the fact that the element barrier layer is too thick, resulting in poor welding performance between the thermoelectric block and the welding piece.

[0070] Comparative Example 1:

[0071] The difference between Comparative Example 1 and Example 1 is that in Comparative Example 1, there is no 0.88 Pb 0.06 Ca 0.03 Yb 0.03 The CuSeO thermoelectric block needs to have a Mo element barrier layer sputtered on the welding surface, and the other processes are the same as those in Example 1.

[0072] The initial interface resistivity of the BiCuSeO-based thermoelectric device prepared in Comparative Example 1 is 5.06 mΩ / cm 2 , and increased to 56 mΩ / cm after annealing for 10 h 2 This is mainly because the performance of the solder deteriorates, resulting in cracks between the solder and the copper plate, and because there is no element barrier layer, serious element diffusion occurs between the thermoelectric block and the solder sheet, resulting in the attenuation of thermoelectric performance. In addition, the initial welding strength of the thermoelectric device joint is 9.37MPa, which decreases to 1.31MPa after annealing for 10h, indicating that the service life of the thermoelectric device joint is less than 10h.

[0073] Comparative Example 2:

[0074] The difference between Comparative Example 2 and Example 1 is that in Comparative Example 2, the magnetron sputtering time is controlled in Bi 0.88 Pb 0.06 Ca 0.03 Yb 0.03 The thickness of the element barrier layer sputtered on the surface of the CuSeO thermoelectric block to be welded is 400 nm, and the other processes are the same as those in Example 1.

[0075] The initial interface resistivity of the BiCuSeO-based thermoelectric device prepared in Comparative Example 2 is 4.77 mΩ / cm 2 , and increased to 54 mΩ / cm after annealing for 10 h 2 This is mainly because the solder performance deteriorates, resulting in cracks between the solder and the copper plate, and because the element barrier layer is too thin, element diffusion occurs between the thermoelectric block and the solder sheet, resulting in the attenuation of thermoelectric performance. In addition, the initial welding strength of the thermoelectric device joint is 10.02MPa, which decreases to 1.73MPa after annealing for 10h, indicating that the service life of the thermoelectric device joint is less than 10h.

[0076] Comparative Example 3:

[0077] The difference between Comparative Example 3 and Example 1 is that in Comparative Example 3, no other impurity elements are doped into the BiCuSeO thermoelectric, the synthesized thermoelectric material is BiCuSeO, and the other processes are the same as those in Example 1.

[0078] The ZT of the BiCuSeO-based thermoelectric block prepared in Comparative Example 3 at 500°C is 0.81, and the initial interface resistivity of the corresponding thermoelectric device is 2.86 mΩ / cm 2 After 40 hours of use, the highest interface resistivity is 8.32mΩ / cm 2

[0079] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. A BiCuSeO-based thermoelectric device, characterized in that: The BiCuSeO-based thermoelectric device is a sandwich structure, which is a copper electrode / soldering piece / thermoelectric block / soldering piece / copper electrode arranged in sequence; wherein the thermoelectric block is a thermoelectric block prepared by element-doped BiCuSeO-based thermoelectric material, and the interface of the soldering piece / thermoelectric block has an element diffusion barrier layer.

2. A method for preparing a BiCuSeO-based thermoelectric device, characterized in that: The preparation method is used to prepare the BiCuSeO-based thermoelectric device according to claim 1, and the preparation method comprises the following steps: 1) mixing a bismuth source, a copper source, a selenium source and a doping element source, and then preparing an element-doped BiCuSeO-based thermoelectric material by ball milling combined with a high-temperature solid phase reaction method; 2) preparing a BiCuSeO-based thermoelectric block by using the element-doped BiCuSeO-based thermoelectric material obtained above through SPS technology; 3) A layer of element diffusion barrier layer is prepared on the surface of the BiCuSeO-based thermoelectric block obtained above by magnetron sputtering technology, and then a BiCuSeO-based thermoelectric device with a sandwich structure of copper electrode / welding piece / thermoelectric block / welding piece / copper electrode is prepared by high temperature welding technology.

3. The preparation method according to claim 2, characterized in that: In step 1, the bismuth source is at least one of bismuth oxide and bismuth powder.

4. The preparation method according to claim 2, characterized in that: In step 1, the copper source is at least one of copper powder and copper oxide.

5. The preparation method according to claim 2, characterized in that: In step 1, the selenium source is at least one of selenium powder and selenium dioxide.

6. The preparation method according to claim 2, characterized in that: In step 1, the doping element source is at least one of Pb, Yb, Ca, Mo, Ni, Mn, Li, Ga, Ag, and Sb; The molecular formula after doping is Bi 1-x M x CuSeO, wherein M is the general term for one or more doping elements, x is the amount of all doping elements, and the value of x is 0.02-0.

2.

7. The preparation method according to claim 1, characterized in that: In step 1, the ball milling combined with high-temperature solid-phase reaction method is a first ball milling treatment-high-temperature solid-phase reaction-a second ball milling treatment, wherein the time of the first ball milling treatment and the second ball milling treatment are both 1h-20h, and the atmosphere of the first ball milling treatment and the second ball milling treatment are both argon or nitrogen atmosphere; the time of the high-temperature solid-phase reaction is 2h-10h, and the temperature of the high-temperature solid-phase reaction is 650℃-750℃.

8. The preparation method according to claim 2, characterized in that: In step 2, the sintering temperature of the SPS technology is 650° C.-750° C., the pressure is 50 Mpa-70 Mpa, and the time is 2 min-15 min.

9. The preparation method according to claim 2, characterized in that: In step 3, the temperature of the high temperature welding technology is 500-650°C, and the heating rate is 0.5°C / min-5°C / min; The high temperature welding time is 10min-60min; The pressure of the high temperature welding technology is 5Mpa-20Mpa; The soldering sheet is a special silver-copper soldering sheet, and its composition is CuAg 20 P5.

10. The preparation method according to claim 2, characterized in that: In step 3, the element diffusion barrier layer is at least one of a Mo element layer, a Ni element layer, a Ti element layer, and a Fe element layer; The thickness of the element blocking layer is 500nm-6000nm.

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