CN100524867C - Method for manufacturing cobalt stibium antimonide based thermoelectric device - Google Patents

Abstract

The invention relates to a method for manufacturing a cobalt antimonide-based thermoelectric device, which is characterized in that a single pair or multiple pairs of PN thermoelectric blocks are turned over 90° by using the SPS method, and a diffusion barrier film is sprayed on the thermoelectric block by plasma spraying. layer, which can effectively block the diffusion of multiple elements that make up the thermoelectric semiconductor device, and the use of the diffusion barrier layer will transform the connection between the thermoelectric semiconductor and the metal electrode into a metal-to-metal connection process, making the welding of the device easier. The near-eutectic Ag-Cu solder sheet used can not only meet the temperature range of 500-600°C at the high temperature end of cobalt antimonide-based thermoelectric devices, but also provide good soldering materials for the preparation of other medium-temperature thermoelectric material devices. The electrode material is made of Mo-Cu alloy material with a thermal expansion coefficient similar to that of cobalt antimonide, which realizes thermal matching to the greatest extent and reduces thermal stress caused by thermal mismatch.

Description

A kind of manufacturing method of cobalt antimonide based thermoelectric device

technical field

The invention relates to a method for preparing cobalt antimonide CoSb ₃ -based thermoelectric devices, more precisely, the invention relates to a method for connecting cobalt antimonide thermoelectric materials and electrodes, and belongs to the technical field of preparation of CoSb ₃ -based thermoelectric devices.

Background technique

Thermoelectric material is a functional material that directly converts thermal energy and electrical energy into each other. It uses its own Seebeck effect to directly convert thermal energy into electrical energy. With the increasing severity of global environmental pollution and energy crisis, the design and preparation of thermoelectric devices has received more and more attention from all over the world. Refrigeration and power generation devices made of thermoelectric materials are small in size, light in weight, without any mechanical transmission parts, noiseless in operation, and long in service life. They are especially suitable for aerospace, waste heat and waste heat power generation, automobile exhaust, geothermal and other fields. The performance characteristics of thermoelectric materials are characterized by the thermoelectric figure of merit (ZT), where ZT=S ² T/ρκ, S is the Seebeck coefficient, ρ is the resistivity, κ is the thermal conductivity, and T is the absolute temperature.

Cobalt antimonide-based compound thermoelectric materials are considered to be one of the most promising medium-temperature power generation materials, and the thermoelectric figure of merit (ZT) of P-type or N-type cobalt antimonide-based compounds has reached above 1.0, but due to the use of The temperature is high, and the Sn alloy solder used in low-temperature thermoelectric devices is no longer suitable for medium-temperature thermoelectric devices. Therefore, the preparation of cobalt antimonide-based thermoelectric devices is limited by the connection technology at the high-temperature end and progress is slow. Since thermoelectric power generation in the medium temperature field has broad application prospects in space power supply, industrial waste heat, and automobile exhaust, developed countries have begun to pay more and more attention to the research on the preparation technology of cobalt antimonide-based thermoelectric devices. At present, foreign JPL laboratories in the United States have conducted a lot of research on cobalt antimonide-based thermoelectric devices and even cobalt antimonide-based radioisotope generators (RTG), but various specific technologies are strictly kept secret due to military reasons. Now, various countries disclose The literature reports on cobalt antimonide-based thermoelectric devices mainly involve the principle concept of device preparation and the measurement of power generation of P and N thermoelectric pairs, such as patents US20020176815A1, US2006157101A1, documents Efficient segmentedthermoelectric uncouples for space power applications, Energ Convers Manage, 44 (2003) and

H.H.Saber, M.S.Elgenk, T.Caillat, Tests results of skutterudite basedthernmoelectric uncouples, Energ Convers Manage, 48 (2007) etc., all do not see detailed report for specific manufacturing process. Domestic researches on cobalt antimonide-based thermoelectric devices focus on thermoelectric materials, and the preparation of devices has just started. Shanghai Institute of Ceramics has done a lot of work on thermoelectric devices, such as CN1585145A, US20060017170A1, 200710037778.X wait. The present invention intends to provide a method for manufacturing a cobalt antimonide-based thermoelectric device on the basis of the existing work. The preparation of the method is characterized in that the thermoelectric device is formed by wire cutting after the electrodes on both ends of the P-N thermoelectric block are connected. It ensures the good contact of the electrodes to the greatest extent. The high temperature end uses MoCu alloy electrode, near eutectic Ag-Cu solder sheet, Mo, W and other diffusion barrier layers are formed by plasma spraying and quickly welded by SPS, while the low temperature end uses traditional Sn-Pb solder and Cu sheet tin Solder connection.

Contents of the invention

The object of the present invention is to provide a kind of manufacturing method of CoSb ₃ base thermoelectric device, namely provide a kind of connection method of cobalt antimonide thermoelectric material and electrode, the connection method provided is to use discharge plasma (SPS) method at first The PN thermoelectric block is prepared by sintering, and after the two ends are connected to the electrodes, it is cut along the PN interface by wire cutting. By plasma spraying a thin diffusion barrier layer on the thermoelectric block body, the diffusion of one or more elements of the thermoelectric semiconductor device is effectively blocked, so that the prepared device has reliable thermal performance. Secondly, the use of the diffusion barrier layer will transform the connection between the thermoelectric semiconductor and the metal electrode into a metal-to-metal connection process, making the welding of the device easier. The near-eutectic Ag-Cu solder sheet used can not only meet the temperature range of 500-600°C at the high-temperature end of cobalt-antimonide-based thermoelectric devices, but also provide good soldering materials for the preparation of other medium-temperature thermoelectric material devices. The electrode material is made of Mo-Cu alloy material with a thermal expansion coefficient similar to that of cobalt antimonide, which realizes thermal matching to the greatest extent and reduces thermal stress caused by thermal mismatch.

Utilizing the present invention can form a single pair or multiple pairs of π-shaped thermoelectric devices at one time by rationally designing the size, which can simplify the method of preparing a single pair of thermoelectric devices by welding a single P-type and N-type pin, and because it is in a large block of thermoelectric materials After welding, the electrode is cut and formed, which ensures the good contact of the electrodes at both ends to the greatest extent.

The manufacturing process of the cobalt antimonide-based thermoelectric device provided by the present invention comprises the following steps:

a) Use SPS to prepare single or multiple pairs of PN-type CoSb ₃ -based thermoelectric semiconductors in a square mold. SPS sintering is shown in Figure 1. The specific sintering parameters are vacuum degree of 5-15Pa and sintering pressure of 50-60MPa , the heating rate is 80-150°C/min, the sintering temperature is 580-600°C, and then the temperature is kept for 10-20min, and the SPS sintering is completed.

b) Flip the sintered single or multiple pairs of thermoelectric blocks by 90°, change the two sides into upper and lower end faces, use cutting or rough grinding to the required size of the mold, use sandblasting method, use fine sand to The upper and lower end faces are treated to obtain a certain surface roughness, and the impurity particles on the two end faces are ultrasonically cleaned, as shown in Figure 2(a).

c) On both ends of the PN-type CoSb ₃ -based thermoelectric semiconductor, spray a thin diffusion barrier layer with a plasma spraying method, the thickness of the diffusion barrier layer is 10-40 μm, and the barrier layer is composed of Mo, W, Ti, Nb and Ta etc. to prevent the diffusion of thermoelectric material elements and Ag-Cu alloy solder elements or Sn-Pb solder elements for connection. The specific process parameters of plasma spraying are working arc voltage 70-80V, The working current is 250-350A, the spray distance is 80-120mm, the powder supply volume is 30-50g/min, and the powder supply gas flow rate is 0.5-0.6m ³ /h. The schematic diagram of the block after plasma spraying is shown in Fig. 2(b).

d) The Ag-Cu alloy solder sheet after cleaning with absolute ethanol is placed on the two end faces of the PN type CoSb ₃ -based thermoelectric material after plasma spraying in step c), and then put into the electrode having the same thermal expansion coefficient as the CoSb ₃ -based thermoelectric material. The matching Mo-Cu alloy electrode is quickly welded by SPS with a square mold. The specific process parameters of SPS welding are vacuum degree 5-15Pa, sintering pressure 10-25MPa, heating rate 200-250℃/min, at sintering temperature Keep the temperature at 520-600°C for 60-300 seconds, then slowly cool down, the cooling rate is controlled at 100-150°C/min, the SPS welding is completed, and the electrode is sintered, as shown in Figure 2(c).

It should be reminded that the Mo-Cu alloy electrode needs to be pre-treated by sandblasting before SPS to make the surface have a certain surface roughness, and the surface impurities are removed by ultrasonic.

e) On the low-temperature end of the PN-type CoSb _3- based thermoelectric element, electroplate or vacuum sputter a Ni layer with a thickness of about 5-10 μm on the barrier layer, and then use Sn-Pb solder to connect the low-temperature end to the Cu sheet on the ceramic substrate Make solder connections. After the soldering of the low-temperature end is completed, it is shown in Figure 2(d).

f) Use wire cutting to cut a gap with a width of 0.5-2 mm along the junction of P-type and N-type thermoelectric materials, so that after the cutting is completed, a single pair or multiple pairs of P-N thermoelectric elements are formed, as shown in Figure 2 (e) Show.

The high-temperature terminal electrode selected by the present invention is Mo-Cu alloy and the coefficient of thermal expansion of _CoSb3 alloy is very close, which ensures that the thermal stress on the interface is reduced to the minimum when working at high temperature for a long time, and prolongs the life of the thermoelectric device to the greatest extent. . The Ag-Cu alloy soldering piece at the high temperature end is used to quickly connect with the thermoelectric pin by using the fast heating speed of SPS, which solves the shortcoming that ordinary soldering pieces cannot withstand high temperature work. The scanning electron microscope at the high-temperature end interface shows that the interface is well bonded, and there are no obvious cracks or micro-cracks.

The CoSb ₃ matrix is pure or CoSb ₃ is used as the matrix doped or filled with one or more of Ce, Fe, Eu, Yb, Ba, K, Na;

The mass percent content of Cu element in the Ag-Cu alloy solder sheet is 30-60%, and the rest is Ag and a small amount of unavoidable impurity elements Bi or Zn; the thickness of the Ag-Cu alloy solder sheet used is 0.005-0.2 mm.

In the Sn-Pb solder, the mass percentage of Sn element is 25-60%, and the rest is Pb and unavoidable small amount of impurity elements Zn or Ag;

In the Mo-Cu alloy electrode, the mass percentage of Cu is 30-60%, and the rest is Mo and a small amount of unavoidable impurities.

The present invention provides a method different from the conventional method of cutting thermoelectric legs and then welding π-type thermoelectric devices. Its biggest feature is that after the electrodes at both ends of the P-N thermoelectric block are connected, the gap is cut along the PN interface line to the high-temperature electrodes. It is made at the place, which ensures the connection and contact degree of the electrodes at both ends to the greatest extent.

Description of drawings

Figure 1 is a schematic diagram of a single pair of P-N type thermoelectric blocks prepared by SPS.

Figure 2(a) is a schematic diagram of the sintered block after SPS; (b) is a schematic diagram after spraying a diffusion barrier layer Mo at both ends; (c) is a schematic diagram after the high-temperature end electrode is connected; (d) is a schematic diagram after the low-temperature end electrode is connected ; (e) Schematic diagram of the device after cutting along the PN interface line.

Fig. 3 is a scanning electron microscope image of a cross-section of a low-temperature end of a thermoelectric device.

Figure 4 is a surface scan diagram of each element of the high-temperature end section CoSb ₃ /AgCu/Mo ₅₀ Cu ₅₀ of the thermoelectric device, where (a) is the SEI of the selected area; (b) Mo element; (c) Cu element; (d) Ag element; Figure 4 (e) Co element; (f) Sb element.

In the figure 1. Diffusion barrier layer; 2. Ag-Cu alloy sheet; 3. Mo-Cu electrode at high temperature end; 4. Thermoelectric block; 5. Ni metal layer; 6. Sn-Pb solder layer; 7. Cu at low temperature end electrode

Detailed ways

The substantive characteristics and remarkable progress of the present invention are illustrated below through specific examples.

Example 1

First, a 12×12×14mm P-N thermoelectric block was prepared in a square mold, and after being turned over 90°, the two end faces perpendicular to the PN interface were roughly ground to 12×12×12mm, and then ultrasonically cleaned in ethanol. Next, Mo was plasma-sprayed on both end surfaces for about 5 seconds to form a Mo diffusion barrier layer with a thickness of about 10 μm. Put the P-N type thermoelectric block back into the square mold, put the cut Ag-Cu solder piece and Mo-Cu electrode into the mold in turn on the P-N type thermoelectric block, and perform SPS connection. The sintering pressure is 15MPa, and the heating rate is 200°C/min, keep warm at 550°C for 30 seconds, then slowly lower the temperature, the cooling rate is controlled at 100°C/min, and the welding of the high-temperature end electrode is completed. Put the P-N type thermoelectric block connected with the high-temperature electrode on the Mo layer at the low-temperature end and then vacuum sputter a Ni layer with a thickness of about 5 μm to facilitate better soldering, and then use Sn-Pb solder to connect the low-temperature end to the ceramic substrate. The Cu chip is connected by soldering. Cut the P-N type thermoelectric block connected with the electrodes at both ends to form a 0.5mm gap along the PN interface line to form a single pair of π-type devices. The interface of the cut devices is well bonded, and no cracks are found.

Example 2

First, a P-N type thermoelectric block of 8×8×10 mm was prepared in a square mold, and after being turned over 90°, the two end faces perpendicular to the PN interface were roughly ground to 8×8×8 mm, and the same as in Example 1 Methods and conditions The P-N type thermoelectric block is treated and plasma sprayed, and the P-N type thermoelectric block is put back into the square mold, and the cut Ag-Cu soldering piece and Mo-Cu electrode are put into the mold in turn. P-N type thermoelectric block On the block, SPS connection is carried out, the sintering pressure is 20MPa, the heating rate is 250°C/min, the temperature is kept at 550°C for 45 seconds, and then the temperature is slowly lowered, and the cooling rate is controlled at 150°C/min, and the welding of the high-temperature end electrode is completed. Put the P-N type thermoelectric block connected with the high-temperature electrode on the Mo layer at the low-temperature end and then vacuum sputter a Ni layer with a thickness of about 5 μm to facilitate better soldering, and then use Sn-Pb solder to connect the low-temperature end to the ceramic substrate. The Cu chip is connected by soldering. Cut the P-N type thermoelectric block connected with the electrodes at both ends to form a 1mm gap along the PN interface line to form a single pair of π-type devices. The interface of the cut devices is well bonded, and no cracks are found.

Example 3

First, a 6×6×8mm P-N thermoelectric block was prepared in a square mold, and after being turned over 90°, the two end surfaces perpendicular to the PN interface were roughly ground to 6×6×6mm, and the same as in Example 1 Methods and Conditions Treat the P-N type thermoelectric block, plasma spray W on both ends for about 5 seconds, and form a W diffusion barrier layer with a thickness of about 30 μm. Put the P-N type thermoelectric block back into the square mold, put the cut Ag-Cu solder piece and Mo-Cu electrode into the mold in turn on the P-N type thermoelectric block, and perform SPS connection. The sintering pressure is 15MPa, and the heating rate is 250°C/min, keep warm at 550°C for 60 seconds, then slowly lower the temperature, the cooling rate is controlled at 150°C/min, and the welding of the high-temperature end electrode is completed. Put the P-N type thermoelectric block connected with the high-temperature electrode on the Mo layer at the low-temperature end and then vacuum sputter a Ni layer with a thickness of about 10 μm to facilitate better soldering, and then use Sn-Pb solder to connect the low-temperature end to the ceramic substrate. The Cu chip is connected by soldering. The P-N type thermoelectric block connected with the electrodes at both ends was cut along the PN interface line to form a 1.5mm gap to form a single pair of π-type devices. The interface of the cut devices was well bonded, and no cracks were found.

Example 4

First, multiple pairs of PN-type thermoelectric blocks were prepared by the SPS method. After turning over 90°, the vertical and multiple pairs of PN interfaces were roughly ground, and multiple pairs of PNπ-type thermoelectric devices were fabricated by the same process as in Examples 1-3.

Claims (10)

1, a kind of manufacture method of cobalt stibium antimonide based thermoelectric device is characterized in that concrete steps are:

A) utilize the discharge plasma sintering method in square dies, prepare single to or the CoSb of how right P-N type ₃Base thermoelectric semiconductor,

B) with step a) single to or many to 90 ° of the thermoelectric block body upsets that sinter, former side is become upper and lower end face, make PN junction perpendicular to upper and lower end face, utilize sand-blast to adopt fine sand that its upper and lower end face is handled, make its upper and lower end face obtain certain surface roughness, the ultrasonic impurity particle that cleans out end face;

C) single to or many CoSb to the P-N type ₃The first-class plasma spray one diffusion barrier thin layer of the upper and lower end face of base thermoelectric semiconductor, the diffusion barrier thin layer is made up of at least a element among Mo, W, Ti, Nb and the Ta, with Ag-Cu alloy weld tabs element or the Sn-Pb scolder elemental diffusion that prevents the thermoelectric material element and be used to connect;

D) CoSb of the P-N type behind the plasma spraying ₃The upper and lower end face of base thermoelectric semiconductor is made as temperature end and low-temperature end respectively, selects for use Ag-Cu alloy weld tabs to be positioned over described CoSb ₃On the temperature end of base thermoelectric semiconductor, select for use then and CoSb ₃The Mo-Cu alloy electrode that the base thermoelectricity material thermal coefficient of expansion is complementary is positioned on the Ag-Cu alloy weld tabs, utilize the plasma discharging body technology, adopt square dies to weld, welding condition is vacuum degree 5-15Pa, sintering pressure is 10-25MPa, 520-600 ℃ of welding insulations, coolings then; The quality percentage composition of Cu element is 30-60% in the described Ag-Cu alloy weld tabs, and all the other are Ag and inevitable small amount of impurities element; The quality percentage composition of Cu is 30-60% in the described Mo-Cu alloy electrode, and all the other are Mo and inevitable small amount of impurities;

E) at the CoSb of P-N type ₃The low-temperature end of base thermoelectric semiconductor is electroplated or vacuum sputtering layer of Ni layer on the diffusion barrier thin layer that step c) forms, and adopts the Sn-Pb scolder that Cu sheet on low-temperature end and the ceramic substrate is carried out soldering then and is connected; The quality percentage composition of Sn element is 25-60% in the described Sn-Pb scolder, and all the other are Pb and inevitable small amount of impurities element;

F) utilize line cutting to cut out the space of a width for 0.5-2mm along P type and N type thermoelectric material combination interface place, after cutting finishes, form single to or many to π type thermoelectric device.

2, by the manufacture method of the described cobalt stibium antimonide based thermoelectric device of claim 1, the parameter that it is characterized in that the described discharge plasma sintering method of step a) is vacuum degree 5-15Pa, and sintering pressure is 50-60MPa, and sintering temperature is 580-600 ℃.

3, by the manufacture method of the described cobalt stibium antimonide based thermoelectric device of claim 2, the heating rate when it is characterized in that the discharge plasma sintering is 80-150 ℃/min, and the temperature retention time when reaching sintering temperature is 10-20min.

4, by the manufacture method of the described cobalt stibium antimonide based thermoelectric device of claim 1, the thickness that it is characterized in that described diffusion barrier thin layer is 10-40 μ m.

5, press the manufacture method of claim 1 or 4 described cobalt stibium antimonide based thermoelectric devices, running parameter when it is characterized in that adopting plasma spraying method to form the diffusion barrier thin layer is: arc voltage 70-80V, operating current 250-350A, spray is apart from 80-120mm, for powder amount 30-50g/min, supplying the throughput of powder is 0.5-0.6m ³/ h.

6,, it is characterized in that it is 0.05-0.2mm that temperature end is used Ag-Cu alloy weld tabs thickness by the manufacture method of the described cobalt stibium antimonide based thermoelectric device of claim 1.

7, by the manufacture method of the described cobalt stibium antimonide based thermoelectric device of claim 1, the heating rate when it is characterized in that the welding of alloy weld tabs temperature end is 200-250 ℃/min, and insulation is 1-5 minutes during 520-600 ℃ of temperature.

8, by the manufacture method of the described cobalt stibium antimonide based thermoelectric device of claim 1, the speed when it is characterized in that the described cooling of step d) is 100-150 ℃/min.

9, by the manufacture method of the described cobalt stibium antimonide based thermoelectric device of claim 1, it is characterized in that the described Ni layer thickness of step e) is 5-10 μ m.

10, by the manufacture method of the described cobalt stibium antimonide based thermoelectric device of claim 1, it is characterized in that described CoSb ₃Base thermoelectric semiconductor is with CoSb ₃Be matrix, mix or filling Ce Fe, Eu, Yb, Ba, one or more elements among K and the Na.

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