JPH09172204A - Thermoelectric conversion apparatus and thermoelectric its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermoelectric conversion apparatus having a pair of thermoelectric conversion excellent in heat resistance at a high temperature junction and capable of being used in a temperature range in which good thermoelectric conversion efficiency is provided. SOLUTION: A thermoelectric conversion apparatus 1 comprises a pair of thermoelectric conversion devices 2 having a p-type thermoelectric semiconductor device 2p and an n-type thermoelectric semiconductor device 2n electrically connected to each other through a high temperature end electrode 4. A high temperature end junction layer 3 mainly made of Ge and having a thickness of 10 to 300μm is formed on a high temperature end-side paired devices junction. Furthermore, when the p-type and n-type thermoelectric semiconductor devices 2p and 2n are electrically connected to each other through the high temperature end electrode 4, they are soldered at the high temperature end-side paired devices junction by using a solder material mainly made of Ge.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermoelectric generator such as a thermoelectric generator for extracting thermoelectromotive force from a heat source and a thermoelectric cooler which does not use a refrigerant, and a method for manufacturing the same, and more specifically, a thermoelectric converter. The present invention relates to a structure of a joint end portion of a thermoelectric conversion element pair and a manufacturing method thereof.

[0002]

2. Description of the Related Art In a thermoelectric conversion element pair having a structure in which p-type and n-type thermoelectric semiconductors are electrically connected to each other, if one junction is heated to a high temperature and the other junction is cooled to a low temperature, heat generated according to a temperature difference occurs. There is a phenomenon that electromotive force occurs, which is called the Seebeck effect. In the thermoelectric conversion element pair,
When an electric current is passed from one thermoelectric semiconductor to the other thermoelectric semiconductor, there is a phenomenon that one joint absorbs heat and the other joint generates heat, which is called the Peltier effect. Furthermore, when one of the p-type and n-type thermoelectric semiconductors is heated to a high temperature and the other is cooled to cause a current to flow along a temperature gradient, there is a phenomenon that heat is absorbed or generated inside the material depending on the direction of the current. This is called the Thomson effect.

A thermoelectric converter utilizing such an effect has no moving parts that generate vibration, noise, wear, etc.
The thermoelectric conversion device can be a simplified energy direct conversion device having the features of simple structure, high reliability, long life, and easy maintenance. Of thermoelectric semiconductors are electrically connected to each other, and the element pair junction has a structure in which p-type and n-type thermoelectric semiconductors are directly electrically connected to each other, or a p-type thermoelectric semiconductor and Usually, the electrode and the n-type thermoelectric semiconductor are electrically (that is, indirectly) bonded to each other.

In the thermoelectric conversion device having such a configuration, the thermoelectric power generation device utilizing the Seebeck effect for extracting electromotive force depending on the temperature difference set at both ends of the thermoelectric conversion element pair, and the voltage applied to both ends are used. There is a thermoelectric cooling device utilizing the Peltier effect, which cools one end by producing a temperature difference depending on the temperature.

In general, the thermoelectric generator has a higher temperature at the hot end of the thermoelectric conversion element pair than the thermoelectric cooler.
It is known that silicon-germanium, iron silicide, or the like, which has good power generation efficiency at 300 ° C. or higher and excellent heat resistance, is suitable as a thermoelectric semiconductor for power generation used in such a thermoelectric power generator. ing.

However, the element-to-joint portion on the high temperature end side has problems such as breakage and peeling due to high temperature, and reduction in power generation output. Therefore, there are some conventional examples disclosed regarding the structure or manufacturing method of the element-to-junction portion for solving these problems.

(1) For example, there is a method in which both p-type and n-type thermoelectric semiconductor raw material powders are separately packed in the right and left in one molding die, and integrally molded and sintered to directly bond (“iron”). "Silicide": Norio Nishida, Ceramics, Volume 21, p516 (1986), "Silicon-Germanium": Toshiaki Mochimaru, April April issue, p42 (1)
995)).

According to this method, the p-type thermoelectric semiconductor and the n-type thermoelectric semiconductor are directly bonded to each other, and the electrode layer and the bonding layer are not interposed, so that the heat resistance of the bonded portion is quite satisfactory. There is a feature called.

(2) On the other hand, regarding thermoelectric semiconductors containing silicon-germanium as a main component, there is a method of diffusion-bonding p-type and n-type thermoelectric semiconductors to electrodes (G. Fl).
y. Proc. 16th IECEC, II, 307-
12 (1981)). Diffusion bonding in this case is a method of pressing at a temperature below the melting point of the base material and using the diffusion of atoms between the bonding surfaces, so a method of sandwiching the insert metal to promote diffusion There is.

Specifically, a method of diffusion bonding a P ₈ or B ₈ doped Si ₈ Ge ₂ -5 mol% GaP thermoelectric semiconductor and a B-doped Si electrode coated with 3 μm of an Si ₂ Ge ₈ alloy corresponding to an insert metal. It is shown. In this case, temperature: about 1250 ° C, pressure: 14
Bonding is possible under the bonding condition of 0 MPa, and Si is
It has been reported that the ₂ Ge ₈ alloy layer diffuses rapidly into the thermoelectric semiconductor layer and the electrode layer. Further, after the bonding, the structure is such that a clear bonding layer is not formed in the visual field of the optical microscope, and the heat resistance of the bonding portion between the thermoelectric semiconductor and the electrode is high.

(3) On the other hand, as another element-joint structure and manufacturing method, a method of brazing or soldering a thermoelectric semiconductor and an electrode to a lead-tellurium-based thermoelectric semiconductor used in a low temperature range Is disclosed. Of these, brazing is a method in which molten metal (wax) is added between the base materials and joining is performed by utilizing the wetting and flow with the base materials. Soldering is a type of brazing joint. is there. A layer in which a metal layer is interposed between the thermoelectric semiconductor layer and the brazing filler metal layer is provided in order to suppress an excessive reaction between the thermoelectric semiconductor and the brazing filler metal, and to improve the wettability and bonding strength of the brazing filler metal. Many configurations and manufacturing methods have been proposed (Japanese Patent Laid-Open Nos. 5-41543 and 5-55638, etc.).
The method of brazing or soldering has the advantage of being suitable for mass production.

(4) Further, for iron silicide, there has been proposed a thermoelectric conversion element pair constructed by brazing and joining to a Cu electrode with a brazing material such as a Ni—Cu system (Japanese Patent Laid-Open No. Hei 10 (1999) -29100). 6-97512).

[0013]

[Problems to be solved by the invention]

(1) However, in the prior art of the above (1), p
This process is extremely complicated because the raw material powders for both the mold and the n-type thermoelectric semiconductor are separately packed into the right and left in one molding die and only the joint portion is mixed but the other portions are not mixed. Further, since both p and n impurities are present in the vicinity of the joint, there is a problem that the characteristics of the joint are not stable for each mold, such as a decrease in mobility and a decrease in electric conductivity. Furthermore, in this manufacturing method, since it is necessary to press-form or hot-press sinter the thermoelectric conversion element pairs one by one, a flame for an emergency power generator or a gas stove, which is composed of several pairs of thermoelectric elements, for example, a candle as a heat source, is used. Although a generator and the like can be produced, there is a problem in that it is not possible to mass-produce a thermoelectric generator that includes hundreds of element pairs, such as a vehicle-mounted or exhaust heat utilization generator.

(2) Further, in the prior art of the above (2), since a considerably high pressure is required for manufacturing,
A large-scale pressurizing / heating device is required. The thermoelectric conversion device of the prior art (2) was developed with the intention of a power supply for a spacecraft for Jupiter exploration, and is premised on small-scale production. It is difficult to mass-produce such thermoelectric generators. Also,
The thermoelectric conversion efficiency of a thermoelectric semiconductor is proportional to the reciprocal of the thermal conductivity, but this manufacturing method pressurizes and heats when forming the joint, which improves the sintered density and crystallinity of the thermoelectric semiconductor, thus improving the thermal conductivity. However, there is a problem in that the thermoelectric conversion efficiency may decrease due to the increase in the temperature.

(3) Further, in the prior art of the above (3), the temperature that can be used in the case of a thermoelectric generator such as a vehicle-mounted or other exhaust heat utilization generator is a high temperature of 300 to 900 ° C., so that lead tellurium is used. There is a problem that the heat resistance of the thermoelectric semiconductor of the system is insufficient.

(4) Further, in the prior art of the above (4), when the Cu content in the brazing material is large, the reaction between the Cu component and the iron silicide easily proceeds excessively at high temperature, and the iron silicide is eroded. As a result of melting, voids are formed at the interface between the iron silicide and the brazing material, excessive diffusion in the iron silicide, and oxidation and volatilization result in an increase in the thermal and electrical resistance of the joint, There is a problem such as a decrease in bonding strength, and there is a problem that heat resistance is not sufficiently satisfactory.

[0017]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and solves the above problems, and is a highly versatile thermoelectric generator for use in vehicles or other exhaust heat utilization power generators. It is an object of the present invention to provide a thermoelectric conversion element pair applicable to an apparatus, and to provide such a thermoelectric conversion element pair by a manufacturing method capable of mass production.

Specifically, the thermoelectric conversion element pair, which has excellent heat resistance at the high temperature end joint and can be used in a temperature range with good thermoelectric conversion efficiency, does not require a large-scale device such as a high temperature / high pressure sintering device. The purpose is to be able to manufacture.

[0019]

A thermoelectric conversion device according to the present invention has a p-type and an n-type as described in claim 1.
Type thermoelectric semiconductors, or a thermoelectric conversion device having a thermoelectric conversion element pair in which p-type and n-type thermoelectric semiconductors are electrically joined via electrodes, in which at least the element pair junction on the high temperature end side contains Ge as a main component. It is characterized in that the bonding layer is formed.

In an embodiment of the thermoelectric conversion device according to the present invention, as described in claim 2, the bonding layer has a thickness of 10 to 300 μm, or in claim 3. As described above, the main component of the thermoelectric semiconductor can be silicon-germanium, or as described in claim 4, the main component of the thermoelectric semiconductor can be iron silicide.

The method of manufacturing a thermoelectric conversion device according to the present invention has a p-type and an n-type as described in claim 5.
When electrically bonding type thermoelectric semiconductors or p-type and n-type thermoelectric semiconductors through electrodes, brazing using a brazing material containing Ge as a main component is performed at least at the element pair junction on the high temperature end side. It is characterized by having done.

In an embodiment of the method for manufacturing a thermoelectric conversion device according to the present invention, as described in claim 6, a brazing material containing Ge at 90 atomic% or more in the brazing material component is used. It can be brazed and used.

[0023]

According to the thermoelectric conversion device of the present invention, as described in claim 1, p-type and n-type thermoelectric semiconductors are electrically connected to each other or p-type and n-type thermoelectric semiconductors are electrically connected to each other via electrodes. In a thermoelectric conversion device having a pair of thermoelectric conversion elements, Ge is formed at least in the element pair junction portion on the high temperature end side.
In the thermoelectric conversion device having such a thermoelectric conversion element pair, one end side of the thermoelectric conversion element pair is connected to the heat source side. In this case, the heat energy from this heat source is transmitted to the opposite side of the thermoelectric conversion element pair via the high temperature end side bonding layer, and a temperature difference is generated at both ends of the thermoelectric semiconductor.

Since the power generated by the Seebeck effect is proportional to the square of this temperature difference, it is assumed that only 80% of the heat energy is conducted from the heat source side to the thermoelectric semiconductor because the thermal resistance of the high temperature end side junction is high. Although the output will be reduced to 64%, in the present invention, at least the bonding layer on the high temperature end side is made of Ge as the main component, so that the silicon used as the thermoelectric semiconductor in the bonding layer. -Germanium (Si _x Ge _1-x ,
x = 0.4 to 0.8) and the thermal conductivity can be made higher than that of iron silicide, and the thermoelectric conversion efficiency can be further improved.

The p-type and n-type thermoelectric semiconductors are electrically connected directly or indirectly via an electrode, and it is preferable that the electric resistance of the bonding layer is small. That is, when the electric resistance is large, the generated power is not only converted into Joule heat at the joint to be lost, but also the temperature rises locally due to Joule heat, so that peeling or brazing filler metal and thermoelectric semiconductor are excessive. It may also cause a reaction and deteriorate the thermoelectric properties of the thermoelectric semiconductor. The thermoelectric semiconductor used for the thermoelectric conversion element pair is a degenerate semiconductor having a high impurity concentration. However, in the present invention, since the bonding layer contains Ge as the main component, even if the amount of the impurity is about the same, the thermoelectric semiconductor is more than Also, high electric conductivity can be obtained.

In the present invention, it is assumed that a bonding layer containing Ge as a main component is formed at least in the element-to-bonding portion on the high temperature end side. In order to increase the bonding strength with thermoelectric semiconductors and electrodes, to relieve thermal stress, to control the coefficient of thermal expansion, etc., one or more sub-components should be contained. You can In this case, as the accessory component, for example, B, Al, Ga, C, Si,
P, As, Sb, Ti, Zr, Hf, V, Nb, Ta,
Cr, Mo, W, Mn, Fe, Ru, Co, Rh, I
r and Ni are mentioned. In addition to being supplied as a brazing filler metal component, these sub-components may be supplied by being diffused into the bonding layer after end face treatment such as a diffusion barrier layer applied to the end face of the thermoelectric semiconductor before brazing.

In the thermoelectric conversion device according to the present invention,
As described in claim 2, the thickness of the bonding layer is 10 to 10.
More preferably, it is 300 μm. In this case, the thickness of the bonding layer can be formed by adjusting the composition of the thermoelectric semiconductor, the composition of the brazing material, the brazing temperature, the brazing time, the amount of the brazing material, etc.
When the thickness is less than 0 μm, the voids resulting from insufficient wetting of the bonding layer with the recesses on the end surface such as the sintered pores and grain boundary portions of the thermoelectric semiconductor that is a sintered body, and a part of the brazing filler metal component The thermoelectric semiconductor may react too much and the voids resulting from the corrosion of the semiconductor layer may become noticeable. Therefore, the thermal / electrical contact resistance at the interface between the thermoelectric semiconductor and the bonding layer tends to increase, and the bonding strength tends to be insufficient. On the other hand, if the thickness exceeds 300 μm, cracks due to thermal stress may occur at the time of temperature rising / falling, so that the thermal / electrical resistance of the joint portion tends to increase or the joint strength tends to decrease.

The thermoelectric conversion device according to the present invention comprises:
The thermoelectric semiconductor contains silicon-germanium as a main component, or the thermoelectric semiconductor contains iron silicide as a main component. Or you can
The electrodes are layers placed between the p-type and n-type thermoelectric semiconductors and preferably have electrical conductivity equal to or higher than that of the thermoelectric semiconductors. As the electrode material, for example, an alloy containing Si as a main component, an alloy containing silicon-germanium as a main component, which has higher electrical conductivity than a thermoelectric semiconductor, an α-phase or ε-phase iron silicide, or MoSi.
An alloy containing a metal silicide as a main component such as ₂ can be used.

It is also possible to adopt a structure in which the p-type and n-type thermoelectric semiconductors are directly bonded via the bonding layer without using electrodes. Further, the bonding layer according to the present invention is used for forming a bonding portion on the high temperature end side, but it can of course be used as a bonding portion on the low temperature end side.

In the method for manufacturing a thermoelectric conversion device according to the present invention, as described in claim 5, p-type and n-type thermoelectric semiconductors are electrically connected to each other or p-type and n-type thermoelectric semiconductors are electrically connected via electrodes. At the time of joining, at least the element pair joining portion on the high temperature end side is brazed by using a brazing material containing Ge as a main component. Therefore, in the joining layer, silicon-germanium or iron silicide used as a thermoelectric semiconductor is used. Also, the thermal conductivity can be made high, and the thermoelectric conversion efficiency can be further improved.

Then, as described in claim 6,
It is more preferable to braze using a brazing material containing 90 atomic% or more of Ge in the brazing material component. Brazing at this time must be performed at a temperature higher than the high temperature end temperature when the thermoelectric conversion device is used and lower than the sintering temperature or melting point of the thermoelectric semiconductor. Therefore, G in the optimum brazing material
Although the e content depends on the composition of the thermoelectric semiconductor and the electrode,
It is preferably 90 atomic% or more. If it is less than 90 atomic%, the liquidus point (temperature) of the brazing material rises,
Since the brazing temperature rises, there is a tendency that the sintering density of the thermoelectric semiconductor will change during brazing, or the dopant will escape and the characteristics will deteriorate. 90 atom%
If it is less than the above, the reaction of the thermoelectric semiconductor or the electrode with a part of the auxiliary components of the brazing filler metal component may be excessively promoted, so that the thermoelectric semiconductor or the electrode is eroded and a void is formed in the joint surface to cause thermal damage. Problems such as an increase in electrical contact resistance and a decrease in bonding strength tend to occur.

The brazing material may be used in the form of a plate, foil or paste, but the brazing filler component used in the present invention does not include a solvent or an organic binder when it is adjusted to a paste. I shall. G
As the brazing material component other than e, for adjusting the electric conductivity of the formed bonding layer, for improving the wettability of the brazing material with the thermoelectric semiconductor or the electrode, or for the thermal expansion coefficient of the formed bonding layer. It is also possible to contain one or a plurality of types of subcomponents for the purpose of controlling the temperature, relaxing the thermal stress, and the like. And, as the sub-component, for example, B, Al, Ga, C, Si, P, A
s, Sb, Ti, Zr, Hf, V, Nb, Ta, Cr,
Mo, W, Mn, Fe, Ru, Co, Rh, Ir, Ni
And the like.

The brazing method can be performed according to a conventional method. Then, for example, a fastening jig or a load is used to position and hold the thermoelectric semiconductor and the electrode, and heating is performed in a vacuum or an inert gas to perform brazing and joining. The manufacturing method of the present invention is characterized by brazing thermoelectric semiconductors or thermoelectric semiconductors and electrodes with the brazing material of the present invention, and is not limited to the manufacturing steps before and after the brazing step. For example, in order to improve the wettability of the brazing filler metal with the thermoelectric semiconductor or the electrode, to increase the bonding strength, or to prevent a part of the brazing filler metal component from excessively diffusing into the thermoelectric semiconductor layer or the electrode layer. For the purpose, before the brazing step, a surface treatment step of previously forming an active metal layer, a diffusion barrier layer or the like on the joint end surface of the thermoelectric semiconductor or the electrode can be inserted. Further, after passing through a step of cutting the thermoelectric semiconductor into a desired size, not only the manufacturing step of brazing with each electrode but also thick p-type and n-type thermoelectric semiconductors are brazed as shown in FIG. After that, it may be divided into a plurality of thermoelectric conversion element pairs. Further, as shown in FIG. 5 to be described later, after forming a laminated body or an assembly in which side surfaces of a plurality of thermoelectric semiconductor element pairs are joined via an insulating adhesive material or a heat insulating material, electrodes are brazed and joined. You can also do it.

[0034]

【Example】

(Embodiment 1) FIG. 1 shows a structure of a thermoelectric conversion device according to a first embodiment of the present invention. The thermoelectric conversion device 1 shown in FIG. 1 includes a p-type thermoelectric semiconductor 2p and an n-type thermoelectric semiconductor 2n. And a plurality of thermoelectric conversion element pairs 2 arranged alternately. The high temperature end side of the thermoelectric conversion element pair 2 is bonded to the high temperature end electrode 4 via a high temperature end bonding layer 3 containing Ge as a main component. Thus, the high temperature end sides of the P-type thermoelectric semiconductor 2p and the n-type thermoelectric semiconductor 2n are electrically connected to each other, the high temperature end electrode 4 is held by the high temperature end substrate 5, and the low temperature of the thermoelectric conversion element pair 2 is low. By bonding the end side to the low temperature end electrode 7 via the silver paste layer 6, the low temperature end sides of the p-type thermoelectric semiconductor 2p and the n-type thermoelectric semiconductor 2n are electrically connected to each other, and the low temperature end electrode 7 is formed. Low temperature substrate 8
It is the structure that is held by.

In manufacturing the thermoelectric conversion device 1 having such a configuration, the p-type thermoelectric semiconductor 2p and the n-type thermoelectric semiconductor 2n are 1250 each of Si ₂ Ge powder containing 0.1% by weight of B or P, respectively. At a temperature of ℃ and 2
Hot-press sintering at 0 MPa pressure, 120φ × 10
After forming a sintered body of mm, 5 × 5 × 10 from each sintered body
It was obtained by cutting the p-type and n-type thermoelectric semiconductors 2p and 2n of mm.

Further, the high temperature end electrode 4 was obtained by hot pressing and sintering Si powder containing 3 wt% of P, and cutting this sintered body into length and width of 5 × 11 mm and thickness of 1.5 mm.
And the brazing filler metal is Ge: 96 at%, P: 3 at%,
Mo: A raw material powder having a composition of 1 atomic% was pulverized, passed through a 22 μm mesh sieve, and kneaded with a commercially available binder for metal brazing material to form a paste.

FIG. 2 shows a manufacturing process diagram of the thermoelectric conversion device 1 shown in FIG.

After the p-type and n-type thermoelectric semiconductors 2p and 2n made of the Si ₂ Ge sintered body and the high temperature end electrode 4 made of the Si sintered body are washed with an HF aqueous solution to remove the oxide film. As shown in FIG. 2 (A), a lower brazing / bonding jig 1 made of machinable ceramics and capable of positioning and holding the thermoelectric semiconductors 2p and 2n.
The p-type and n-type thermoelectric semiconductors 2p and 2n cut as described above are alternately arranged on the top of 1 through the assembling spacer 12 so that 5 pairs of p and n are arranged side by side. The above-mentioned brazing material paste was applied to the portion, the high temperature end electrode material was attached, and dried. Then, a load of 20 g is placed on the upper brazing and joining jig 13, and a vacuum firing furnace is used.
Pressure: 10 ⁻⁵ Torr, Temperature: 1050 ° C., Time: 1
It was brazed and baked under the condition of 0 minutes.

Next, as shown in FIG. 2B, a low temperature end electrode 7 made of copper was attached to the end faces on the opposite side of the thermoelectric semiconductors 2p and 2n using a general-purpose silver paste and dried. And FIG.
As shown in (C), AlN substrates 5 and 8 were attached to the surfaces of both electrodes 4 and 7 by alumina-based ceramic bond.

Next, a Pt wire for extracting power generation output was attached to the low temperature end electrode 7 with silver paste, the high temperature end substrate 5 was brought into contact with a heater, and the low temperature end substrate 8 was attached to a water cooling block with grease. Thus, the output result of measuring the generated electric power by the thermoelectric conversion device 1 of this Example 1 is shown in FIG. 3 together with the output result of Comparative Example 1 described later.

As shown in FIG. 3, even when the temperature difference between the high temperature end and the low temperature end is 500 ° C. or more and the temperature at the high temperature end is 590 ° C., the high temperature end is not destroyed and the power generation output is generated without causing any abnormality. Could be detected.

(Comparative Example 1) Si ₂ Ge as in Example 1
Example 1 except that the thermoelectric semiconductors 2p and 2n made of a sintered body and the high temperature end electrode 4 made of a Si sintered body were used and the high temperature end electrode 4 was brazed with a commercially available silver solder (72Ag-28Cu). A similar thermoelectric conversion device 1 was created. Then, the result of measuring the power generation output in the same manner as in Example 1 is as shown in FIG. 3, and in Comparative Example 1, the output was 400 ° C. at the temperature difference between the high temperature end and the low temperature end and 460 ° C. at the high temperature end. It dropped and the wire was broken. In this case, the breaking point is a joint portion by silver brazing, the Si ₂ Ge thermoelectric semiconductors 2p and 2n are excessively reacted with Cu in the silver brazing component and eroded, and the reaction product is oxidized and volatilized to the joint portion. It was observed that the voids were widening.

From the results of Comparative Example 1 and Example 1, it was confirmed that the heat resistance at the high temperature end was improved by adopting the constitution in which the bonding layer according to the present invention was formed.
In addition, a thermoelectric generator with high heat resistance could be manufactured without using a large-scale high-pressure / high-temperature device.

(Example 2, Comparative Example 2) The same thermoelectric semiconductors 2p and 2n made of Si ₂ Ge sintered body as in Example 1 and the high temperature end electrode 4 made of Si sintered body having a thickness of 3 mm were used. G
A thermoelectric conversion element pair 2 having a pair of p-type and n-type thermoelectric semiconductors 2p and 2n was formed by brazing and joining with e solder. Then, contact the high temperature end electrode 4 on the heater 6
It is heated at 00 ° C., and the temperature T ₀ of the high temperature end electrode 4 and the Si ₂ Ge thermoelectric semiconductor 2p,
The temperature T ₁ at the high temperature end of 2n was measured. Where 1-T ₁
/ T ₀ represents the contact thermal resistance of the joint. And this is 0
Indicates that there is no contact thermal resistance.

After that, a cut and polished surface sample was prepared, and the joint portion was observed with an optical microscope. Table 1 shows the Ge brazing composition used for brazing, the coating amount, the brazing conditions and the temperature measurement results.

[0046]

[Table 1]

As shown in Table 1, by adopting the constitution of the bonding layer of the present invention, it is possible to form a good thermoelectric conversion device in which the contact thermal resistance at high temperature is small and voids and cracks are not observed in the bonding portion. did it. Moreover, the thermoelectric semiconductor could be formed by brazing in a temperature range of 1200 ° C. or lower that does not deteriorate the temperature.

On the other hand, the samples which did not depend on the brazing material of the present invention (Comparative Examples 2-1 and 2-2) and the samples which could not be formed into the structure having the bonding layer of the present invention (Comparative Examples 2-3 and 2-).
In 4), joining could not be performed or contact thermal resistance was large, cracks were generated and voids were observed at the joining interface.

(Example 3 and Comparative Example 3) FeS containing 6 atomic% of CoSi ₂ or Mn ₁₁ Si ₁₉ , respectively.
The i ₂ raw material powder was hot-press sintered to prepare an α-FeSi ₂ sintered body. Then, annealing is performed in Ar at 850 ° C. for 100 hours to obtain p-type and n-type β-FeS.
Each i ₂ thermoelectric semiconductor was prepared and cut into 5 × 5 × 10 mm. On the other hand, for the high temperature end electrode, an α-FeSi ₂ sintered body was used, and it was cut into a size of 5 × 11 mm in length and width and 2 mm in thickness. As the brazing filler metal, a raw material powder having the composition shown in Table 2 was pulverized to a mesh of 22 μm or less, and a commercially available binder for metal brazing filler metal was added and kneaded to form a paste.

Then, the high temperature end electrode and the p-type and n-type thermoelectric semiconductors were brazed in vacuum at 1100 ° C. for 10 minutes to form a thermoelectric conversion element pair. Also, p-type,
The end of the low temperature end of the n-type thermoelectric semiconductor was plated with Ni, and a low temperature end electrode made of copper was soldered. Then, an alumina substrate was attached to the surfaces of both electrodes with an alumina-based ceramics bond to obtain thermoelectric generators of Example 3 and Comparative Example 3.

Then, in the same manner as in Example 1, a heater and a water cooling block were respectively brought into contact with the high temperature end substrate and the low temperature end substrate, and the power generation output was measured at a temperature difference of 550 ° C. between the high temperature end and the low temperature end. Here, the brazing temperature is higher than the α-β phase change point, but since the brazing time is short, no decrease in power generation output was observed. Then, the cut and polished surface of the high temperature end joint was observed with an optical microscope. Table 2 shows the results.

[0052]

[Table 2]

As shown in Table 2, by the brazing method of the present invention, it was possible to prepare a thermoelectric conversion device having excellent heat resistance in which the high temperature end joint portion did not peel off even at a temperature difference of 550 ° C. On the other hand, when the brazing material of the comparative example was used, it was not joined or many voids were formed at the interface between the brazing material and FeSi ₂ , so that the electrical resistance increased and the output decreased.

(Embodiment 4) The manufacturing process of the thermoelectric conversion device in Embodiment 4 is shown in FIG.

In this example, as the p-type Si ₂ Ge thermoelectric semiconductor 2p, a Si ₄ Ge sintered body containing B: 0.5 atomic% and GaP: 5 atomic% was used, and n-type Si ₂ G was used.
e As the thermoelectric semiconductor 2n, P: 0.5 atomic%, GaP:
These sintered bodies were formed by hot press sintering, using the Si ₄ Ge sintered bodies containing 5 atomic%. And 4 x 50 x 10 mm from each sintered body
Was cut and washed with an HF aqueous solution to remove the oxide film. Then, the two sintered bodies were joined together with a paste-like brazing material having a composition ratio of 95Ge-3Al-2Ti (atomic%), as shown in FIG.
As shown in (A), the thermoelectric conversion element pair 2 in which the p-type and n-type thermoelectric semiconductors 2p and 2n were joined by the high-temperature end joining layer 3 having a joining layer thickness of 200 μm was formed.

Next, as shown in FIG. 4B, a cutting groove 15 is formed in the joining layer portion using a low speed saw, leaving the high temperature end joining layer 3 having a height (h) of 3 mm, and As shown in FIG. 4 (C), the thermoelectric conversion element pair 2 is divided into five equal parts to form five pairs, and as shown in FIG. 4 (D), the p-type thermoelectric semiconductor 2p and the n-type thermoelectric semiconductor 2n are alternately arranged. 4E, the low temperature end electrodes 7 are attached with a silver paste, and the AlN high and low temperature end substrates 5 and 8 are bonded to both ends with zirconia-silica ceramics bond as shown in FIG. 4 (E). It was attached and dried to obtain a thermoelectric conversion device 1.

In this thermoelectric converter 1, the Pt wire for taking out the power generation output was soldered to the low temperature end electrode 7. Then, when a cooling block for water cooling and a heater for heating were respectively brought into contact with both ends of the prepared thermoelectric conversion device 1 and a power generation output was tested, a temperature difference: 600 ° C., a high temperature end:
A power generation of 1.5 W was obtained at 680 ° C. Further, no decrease in the power generation output after 50 hours was observed.

As described above, by using the brazing material of the present invention to form the thermoelectric conversion element of the present invention, a thermoelectric conversion device having excellent heat resistance at the high temperature end could be produced. In addition, a thermoelectric conversion device can be simply manufactured in a process of forming a plurality of thermoelectric conversion element pairs by one brazing process without molding each one of the thermoelectric conversion element pairs and performing hot press sintering. It was

(Embodiment 5) The manufacturing process of the thermoelectric conversion device in Embodiment 5 is shown in FIG.

In this embodiment, a p-type thermoelectric semiconductor 2p and an n-type thermoelectric semiconductor 2n, which are the same as those in the fourth embodiment, are arranged side by side in FIG.
As shown in (A), the machinable insulating ceramics 1
A thermoelectric semiconductor assembly was prepared by solidifying in 7 a slightly curved shape as a whole. Then, a patterning mask is applied to one end face of the aggregate, and as shown in FIG. 5B, a Ni—Cr layer is formed as the surface treatment layer 18 in the thermoelectric semiconductors 2p and 2p.
It was formed by sputtering to a thickness of 0.5 μm only on the other end face of n.

Next, as shown in FIG.
The high temperature end electrode 4, which is an α-FeSi ₂ sintered body cut into 11 mm and a thickness of 1 mm, is 98 atomic% Ge-2 atomic% Ga.
The brazing material having the composition was brazed under the condition of 1050 ° C. for 10 min, and the thermoelectric semiconductors 2p and 2n were electrically bonded via the high temperature end bonding layer 3 mainly composed of Ge. Next, as shown in FIG. 5D, a Cu low-temperature end electrode 7 was attached to the arc-shaped low-temperature end substrate 8 cut out from the cylindrical alumina tube by an alumina-based ceramic bond. Then, the low temperature end electrode 7 was attached to one end surface of the thermoelectric semiconductor assembly through the silver paste layer 6 to obtain the thermoelectric conversion device 1.

Next, an output test of the thermoelectric converter 1 was conducted by bringing a cooling block for water cooling into contact with the outside of the thermoelectric converter 1 and a cylindrical heater inside with the glass wool. As a result, an output of 0.5 W was obtained when the temperature difference between both ends of the thermoelectric converter 1 was 400 ° C. Then, when the cut and polished surface of the high temperature end bonding portion was observed with an optical microscope, the bonding layer between the thermoelectric semiconductor and the electrode was 80 μm. Further, as a result of composition analysis of the joint portion by an X-ray microanalyzer, the main component was Ge and other Si, Ga, Ni, Cr were detected.

As described above, by manufacturing the thermoelectric conversion device by the manufacturing method of the present invention, it is possible to easily manufacture the thermoelectric power generating device having a shape which is difficult to design by the manufacturing method using the pressurizing / heating device. did it. In addition, it was possible to manufacture a thermoelectric generator having high heat resistance at the high temperature end joint.

[0064]

According to the thermoelectric conversion device of the present invention,
As described in claim 1, a thermoelectric conversion device comprising a thermoelectric conversion element pair in which p-type and n-type thermoelectric semiconductors are electrically connected to each other or p-type and n-type thermoelectric semiconductors are electrically joined via electrodes, Since the bonding layer containing Ge as a main component is formed at least at the element-to-bonding portion on the high temperature end side, it is possible to prevent peeling or breakage from occurring at the bonding portion on the high temperature end side. In addition, it is possible to provide a thermoelectric conversion device that can be used at a high temperature of about 500 to 600 ° C., and to reduce the thermal resistance or the electrical resistance at the joint portion of the thermoelectric conversion element pair even under the high temperature during use. It is possible to provide a thermoelectric conversion device with a low power generation output loss, which is a significant advantage.

Then, as described in claim 2,
When the thickness of the bonding layer is 10 to 300 μm, it is possible to reduce the thermal electrical resistance at the thermoelectric semiconductor and the bonding interface, and it is also difficult for cracks to occur when the temperature is raised or lowered. As described in claim 3, the main component of the thermoelectric semiconductor is silicon-germanium, or as described in claim 4, By using iron silicide as the main component of the thermoelectric semiconductor, it is possible to use silicon-germanium or iron silicide having a high power generation efficiency at 300 ° C. or higher, which is a remarkably excellent effect.

Further, according to the method of manufacturing a thermoelectric conversion device of the present invention, as described in claim 5, the p-type and n-type thermoelectric semiconductors are interleaved or the p-type and n-type thermoelectric semiconductors are interposed via electrodes. At the time of electrical joining by means of brazing using a brazing material containing Ge as the main component, at least at the element pair joining portion on the high temperature end side, large pressure / heating means are not required, and it is inexpensive. The thermoelectric converter can be manufactured at low cost because it can be joined in a simple firing furnace at a low temperature.Because no pressurizing / heating equipment is used, the size and shape of the jig for joining is limited. Without
This has the remarkable effect of increasing the degree of freedom in designing thermoelectric converters according to the characteristics and shape of the heat source.
Furthermore, according to the above-mentioned manufacturing method of the present invention, since it is possible to bond by heating for a short time at a temperature lower than the sintering temperature or melting point of the thermoelectric semiconductor, a thermoelectric conversion device is manufactured without impairing the thermoelectric characteristics of the semiconductor. Furthermore, since a plurality of thermoelectric conversion element pairs can be joined at the same time, the thermoelectric conversion element can be applied to a highly versatile thermoelectric generation device such as a vehicle-mounted or other exhaust heat utilization power generation device. The remarkable advantage is that mass production of pairs is also possible.

Then, as described in claim 6,
By brazing using a brazing material containing 90 atomic% or more of Ge in the brazing material component, it is possible to braze at a temperature certainly lower than the sintering temperature or melting point of the thermoelectric semiconductor. The remarkably excellent effect of

[Brief description of the drawings]

FIG. 1 is a schematic explanatory diagram showing a basic configuration of a thermoelectric conversion device according to a first embodiment of the present invention.

FIG. 2 shows a manufacturing process of the thermoelectric conversion device shown in FIG.
It is explanatory drawing which divides into (B) and (C) and shows one by one.

FIG. 3 is a graph showing a result of an output test of thermoelectric conversion devices according to Example 1 and Comparative Example 1.

FIG. 4 is an explanatory view showing the manufacturing steps of a thermoelectric conversion device according to a fourth embodiment of the present invention, which are sequentially divided into (A), (B), (C), (D), and (E).

FIG. 5 is an explanatory view showing a manufacturing process of a thermoelectric conversion device according to a fifth embodiment of the present invention, which is divided into (A), (B), (C), and (D).

[Explanation of symbols]

 1 thermoelectric conversion device 2 thermoelectric conversion element pair 2n n-type thermoelectric semiconductor 2p p-type thermoelectric semiconductor 3 high temperature end bonding layer 4 high temperature end electrode 5 high temperature end substrate 6 silver paste layer 7 low temperature end electrode 8 low temperature end substrate

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Miyoshi Mito 2-56, Sudacho, Mizuho-ku, Nagoya, Aichi Prefecture Insulator Himoto Incorporated (72) Inventor Keiko Kushibiki Takaracho, Kanagawa-ku, Yokohama, Kanagawa No. 2 Nissan Motor Co., Ltd. (72) Inventor Kazuhiko Shinohara No. 2 Takaracho, Kanagawa-ku, Yokohama, Kanagawa Prefecture Nissan Motor Co., Ltd. (72) Masakazu Kobayashi No. 2 Takara-cho, Kanagawa-ku, Yokohama, Nissan Co., Ltd. (72) Inventor Kenji Furuya 2 Takaracho, Kanagawa-ku, Yokohama-shi, Kanagawa Nissan Motor Co., Ltd.

Claims (6)

[Claims] 1. A thermoelectric conversion device comprising a thermoelectric conversion element pair in which p-type and n-type thermoelectric semiconductors are electrically connected to each other or p-type and n-type thermoelectric semiconductors are electrically connected via electrodes, at least an element at a high temperature end side. A thermoelectric conversion device, wherein a bonding layer containing Ge as a main component is formed at the paired bonding portion. 2. The thermoelectric conversion device according to claim 1, wherein the bonding layer has a thickness of 10 to 300 μm. 3. The thermoelectric conversion device according to claim 1, wherein the main component of the thermoelectric semiconductor is silicon-germanium. 4. The thermoelectric conversion device according to claim 1, wherein the main component of the thermoelectric semiconductor is iron silicide. 5. When electrically connecting p-type and n-type thermoelectric semiconductors or p-type and n-type thermoelectric semiconductors via electrodes, Ge is formed at least at the element-to-joint portion on the high temperature end side.
A method for manufacturing a thermoelectric conversion device, which comprises brazing using a brazing material containing as a main component. 6. The method of manufacturing a thermoelectric conversion device according to claim 5, wherein brazing is performed using a brazing material containing 90 atomic% or more of Ge in the brazing material component.