JP2022144073A - Laminate with thermoelectric conversion layer and production method thereof, and power generation module - Google Patents

Abstract

To provide a thermoelectric conversion element which can be produced from a material having high biological safety, and which enables the materialization of a flexible and slim thermoelectric conversion module, and provide a method for producing a thermoelectric conversion element having a self-standing property without needing a complicated process.SOLUTION: A thermoelectric conversion element is arranged by laminating a first conductive substrate 1, a thermoelectric conversion oxide layer 2 provided on an upside of the first conductive substrate, and a second conductive substrate 3 on an upside of the thermoelectric conversion oxide layer in this order. In the thermoelectric conversion element, the second conductive substrate is formed so as to have an outer periphery located on or inside an outer periphery of the thermoelectric conversion oxide layer. As to respective areas of the layers, the relation given by the following expressions holds: [Area of the first conductive substrate ]≥[Area of the thermoelectric conversion oxide layer]≥[Area of the second conductive substrate], and [Area of the first conductive substrate]>[Area of the second conductive substrate]. For respective thicknesses of the layers, the relation given by the following equation holds: [Thickness of the thermoelectric conversion oxide layer]:([Thickness of the first conductive substrate]+[Thickness of the second conductive substrate])=1:1 to 1:10.SELECTED DRAWING: Figure 1

Description

TECHNICAL FIELD The present invention relates to a laminate having a thermoelectric conversion layer, a method for producing the laminate, and a power generation module using the laminate.

BACKGROUND ART Conventionally, as one of means for effective use of energy, a system for directly interconverting thermal energy and electrical energy using a thermoelectric conversion module having thermoelectric effects such as the Seebeck effect and the Bertier effect has been put into practical use.
In recent years, these thermoelectric conversion modules have attracted attention as power sources for wearable and flexible devices.In addition to improving the thermoelectric conversion performance, the use of materials that are safer for the environment and the human body, as well as modules with flexibility and elasticity. There is a demand for improved flexibility and thinner modules.

For example, there is a thermoelectric conversion module that has flexibility by mounting micro thermoelectric element chips on mounting lands (which also serve as connection electrodes) on a resin thin film substrate at high density, and ensuring the flexibility of the substrate between the mounting lands. It is disclosed (Patent Document 1).
There is also a proposal for a thermoelectric conversion module using a thermoelectric conversion material chip manufactured using a peeling layer (sacrificial layer) (Patent Document 2).
On the other hand, a thermoelectric conversion layer formed by a coating process that enables thinning is used as a thermoelectric conversion element, and a thermoelectric conversion material powder is mixed with a binder and made into a paste. A device has been disclosed (Patent Document 3).

JP 2009-267316 A WO2020/045379 JP 2008-270410 A

Patent Documents 1 and 2 use the bismuth-tellurium-based thermoelectric semiconductor material used as the thermoelectric conversion material in the examples, but the thermoelectric semiconductor material contains tellurium ( Te) as a constituent element. In addition, the thermoelectric conversion module disclosed in Patent Document 1 seems to be intended to be attached to a drainage pipe, and the thermoelectric element chip itself is relatively thick. And further thinning is desired. Moreover, in the manufacturing process of Patent Document 2, the thermoelectric conversion module itself requires the formation of an unnecessary peeling layer, which complicates the manufacturing process.
Patent Document 3 uses an oxide thermoelectric semiconductor material as a thermoelectric conversion material. However, oxide thermoelectric semiconductor materials are more fragile than metal-based materials such as the above-mentioned bismuth-tellurium-based thermoelectric semiconductor materials, and it is difficult to obtain thermoelectric element chips having self-supporting properties. Therefore, in Patent Document 3, a thin film containing an oxide thermoelectric semiconductor material is formed on the electrodes on the substrate of the thermoelectric conversion module, and the thin film itself does not stand on its own and is poor in handleability.

The present invention provides a thermoelectric conversion element that can be manufactured from a material with high biosafety and that can realize a flexible and thin thermoelectric conversion module. An object of the present invention is to provide a method capable of producing

The present inventors have made intensive studies to solve the above problems, and can provide a thermoelectric conversion element that uses a highly safe thermoelectric conversion oxide material as a thermoelectric conversion material and overcomes the brittleness that is a problem of the material. A manufacturing method was discovered, and the present invention was completed.

That is, the present invention, as a first aspect,
a first conductive substrate;
a thermoelectric conversion oxide layer provided on the upper side of the first conductive substrate;
A second conductive substrate provided on the upper side of the thermoelectric conversion oxide layer is laminated in this order,
The outer periphery of the second conductive substrate is a thermoelectric conversion element formed on or inside the outer periphery of the thermoelectric conversion oxide layer,
Regarding the area of each layer, [Area of first conductive substrate]≧[Area of thermoelectric conversion oxide layer]≧[Area of second conductive substrate] and [Area of first conductive substrate]> The relationship of [the area of the second conductive substrate] is established,
Regarding the thickness of each layer [thickness of thermoelectric conversion oxide layer]: <[thickness of first conductive substrate] + [thickness of second conductive substrate]> = 1:1 to 1:10 It relates to a thermoelectric conversion element characterized in that the relationship of
As a second aspect, a first conductive paste layer is formed between the first conductive substrate and the thermoelectric conversion oxide layer, and between the thermoelectric conversion oxide layer and the second conductive substrate It relates to the thermoelectric conversion element according to the first aspect, in which the second conductive paste layer is formed.
A third aspect relates to the thermoelectric conversion element according to the first aspect or the second aspect, wherein the thermoelectric conversion oxide layer has an area of 0.5 mm ² to 20 mm ² .
As a fourth aspect, the thermoelectric conversion oxide layer is
General formula (1):
_{CaMn1 - xM1xOy} ( ¹ )
(In the formula, M1 is at least ^one element selected from the group consisting of Nb, Ta, Mo and W, and x and y are 0≤x≤0.1, 2.8≤y≤3. It is a number that satisfies 2.)
An n-type thermoelectric conversion layer made of an oxide composite containing a perovskite-type calcium manganese oxide represented by
General formula (2) or general formula (3):
_{Ca3 - pBipCo4Oq} ( ₂ )
(In the formula, p and q are numbers satisfying 0≤p≤1 and 8.5≤q≤10.)
_{Bi2Sr2 - rCarCo2Ot ( 3} )
(In the formula, r and t are numbers satisfying 0.0≦r≦2.0 and 8.5≦t≦10.)
A p-type thermoelectric conversion layer made of an oxide composite containing a cobalt-based oxide represented by
The thermoelectric conversion element according to any one of the first to third aspects.
As a fifth aspect, a method for manufacturing a thermoelectric conversion element,
applying a conductive paste on a first conductive substrate and baking to form a first conductive paste layer;
applying a thermoelectric conversion oxide layer-forming composition onto the first conductive paste layer to form a coating;
a step of baking the coating at 300° C. or higher to form a thermoelectric conversion oxide layer;
Separately, a step of applying a conductive paste on a second conductive substrate and drying to form a second conductive paste layer;
The first conductive substrate and the second conductive substrate are stacked so that the thermoelectric conversion oxide layer and the second conductive paste layer face each other, and the layers are pressed at 300° C. or higher in the stacking direction. the process of pressing,
and a method for manufacturing a thermoelectric conversion element.
As a sixth aspect, a method for manufacturing a thermoelectric conversion element,
applying a conductive paste on a first conductive substrate and baking to form a first conductive paste layer;
applying a thermoelectric conversion oxide layer-forming composition onto the first conductive paste layer to form a coating;
a step of baking the coating at 300° C. or higher to form a thermoelectric conversion oxide layer 1;
Separately, a step of applying a conductive paste on a second conductive substrate and baking to form a second conductive paste layer;
applying a thermoelectric conversion oxide layer-forming composition onto the conductive second conductive paste layer to form a coating;
a step of baking the coating at 300° C. or higher to form a thermoelectric conversion oxide layer 2;
The first conductive substrate and the second conductive substrate are stacked so that the thermoelectric conversion oxide layer 1 and the thermoelectric conversion oxide layer 2 face each other, and are press-pressed at 300° C. or higher in the stacking direction. the process of
and a method for manufacturing a thermoelectric conversion element.
As a seventh aspect, a plurality of the thermoelectric conversion elements described in the fourth aspect are used, and the unjoined end portion of the p-type thermoelectric conversion element having the p-type thermoelectric conversion layer is connected to the n-type thermoelectric conversion element having the n-type thermoelectric conversion layer. A thermoelectric power generation module in which a plurality of thermoelectric conversion elements are connected in series by a method of connecting to unbonded ends of the conversion elements on a substrate.

According to the present invention, a flexible and thin thermoelectric conversion module can be realized, and a thermoelectric conversion element using a material with high biosafety can be provided. Moreover, according to the present invention, it is possible to provide a method for manufacturing a self-supporting thermoelectric conversion element without requiring a complicated process.

FIG. 1 is a view showing aspects (a) and (b) of the thermoelectric conversion element of the present invention, cross-sectional views ((a-1), (b-1)) and top views ((a-2), (b-2)). FIG. 2 shows a top view showing the manufacturing procedure of the thermoelectric conversion module produced in Example 3. FIG. FIG. 3 shows a cross-sectional view of the thermoelectric power generation module produced in Example 3. FIG.

[Thermoelectric conversion element]
The thermoelectric conversion element (laminate having a thermoelectric conversion layer) of the present invention includes a first conductive substrate, a thermoelectric conversion oxide layer provided on the upper side of the first conductive substrate, and a thermoelectric conversion oxide layer on the upper side of the thermoelectric conversion oxide layer. and a second conductive substrate provided in this order, and the outer periphery of the second conductive substrate is formed on or inside the outer periphery of the thermoelectric conversion oxide layer. It is a conversion element.

In the thermoelectric conversion element of the present invention, with respect to the area of each layer, [Area of first conductive substrate]≧[Area of thermoelectric conversion oxide layer]≧[Area of second conductive substrate] and [Area of first conductive substrate] area of the second conductive substrate]>[area of the second conductive substrate].
In addition, in the thermoelectric conversion element having the above-described laminated structure, if the first conductive substrate and the second conductive substrate are in contact (electrically connected), the function of the thermoelectric conversion element is not achieved. Aspects are virtually non-existent. In order to avoid such a contact mode, the outer circumference of the second conductive substrate can usually be formed on or inside the outer circumference of the thermoelectric conversion oxide layer. It is arranged to extend from the inside to the outside of the thermoelectric conversion oxide layer. Further, the outer circumference of the thermoelectric conversion oxide layer can be formed on or inside the outer circumference of the second conductive substrate.
For example, as a preferred embodiment, the relationship of [area of first conductive substrate]≧[area of thermoelectric conversion oxide layer]>[area of second conductive substrate] is established. That is, as illustrated in FIG. 1(a),
When viewed from the cross section (FIG. 1(a-1)), the size of the first conductive substrate 1, the thermoelectric oxide layer 2, and the second conductive substrate 3 decreases toward the upper side of the paper, When viewed from above (FIG. 1(a-2)), it has a configuration in which a second conductive substrate 3 is provided without protruding from the thermoelectric conversion oxide layer 2 .

From the viewpoint of improving the flexibility of the thermoelectric conversion module assembled from the thermoelectric conversion element of the present invention, the area size is preferably as small as possible.
For example, the thermoelectric conversion oxide layer can be an element having a size of 0.5 mm ² to 20 mm ² , preferably the thermoelectric conversion oxide layer has a size of 1 mm ² to 10 mm ² , for example, 2 mm ² to 5 mm ² . It can be said.

Further, in the thermoelectric conversion element of the present invention, regarding the thickness of each layer, [thickness of thermoelectric conversion oxide layer]: <[thickness of first conductive substrate] + [thickness of second conductive substrate] >= 1:1 to 1:10.
From the viewpoint of thermoelectric conversion efficiency, most of the thermoelectric conversion elements proposed so far usually have a thermoelectric conversion layer that is relatively thicker than the upper and lower conductive substrates.
In the thermoelectric conversion element (laminate) of the present invention, from the viewpoint of improving the flexibility of the thermoelectric conversion module assembled from the element, the thermoelectric conversion element does not impair the self-sustainability and thermoelectric conversion performance of the thermoelectric conversion element itself. It is desirable that the overall thickness be as thin as possible.
For example, when the entire thermoelectric conversion element is thick, when the thermoelectric conversion module provided with the element is bent into a curved surface, the elements may come into contact with each other if the element is provided inside the curved surface. Further, when the element is provided outside the curved surface, there is a risk that the upper electrode (outside the curved surface) connecting the elements may be stretched and cut.
However, in the thermoelectric conversion element of the present invention, when the first conductive substrate and the second conductive substrate are too thin, the thermoelectric conversion oxide layer is obtained by sintering the oxide as described later. Since it is a relatively fragile layer, there is a possibility that the self-sustainability of the element may not be maintained, so care must be taken. On the other hand, if the first conductive substrate and the second conductive substrate are too thick, the thermoelectric conversion module may become excessively hot, the module may be difficult to handle, and the cost may increase. .
In view of these, in the thermoelectric conversion element of the present invention, the thickness of the thermoelectric conversion layer is made substantially equal to or thinner than the thickness of the conductive substrate located outside it, that is, the above relationship is constructed so that In a preferred embodiment, the thermoelectric conversion element of the present invention has [thickness of thermoelectric conversion oxide layer]: <[thickness of first conductive substrate] + [thickness of second conductive substrate]> = 1 : 2 to 1:5.

In the thermoelectric conversion element of the present invention, the thickness of each layer constituting the laminate can be appropriately set in view of the above-mentioned matters. The thickness of the entire device can range from 100 μm to 2.2 mm.

In a preferred embodiment, a first conductive paste layer is provided between the first conductive substrate and the thermoelectric conversion oxide layer, and a second conductive paste layer is provided between the thermoelectric conversion oxide layer and the second conductive substrate. A paste layer is provided.
By providing these conductive paste layers, good conductivity can be imparted between the thermoelectric conversion layer and the conductive substrate, and the conductive paste layer serves as an anchor, and the conductive substrate and the thermoelectric conversion oxide layer It is possible to improve the bondability (binding property) with.
In addition, regarding the area of these conductive paste layers, [Area of first conductive substrate]≧[First conductive paste layer]≧[Area of thermoelectric conversion oxide layer]≧[Second conductive paste layer]≧[area of second conductive substrate]. Preferably [Area of first conductive substrate] ≥ [First conductive paste layer] ≥ [Area of thermoelectric conversion oxide layer] > [Second conductive paste layer] ≥ [Second conductive substrate area] is established (see FIG. 1(b)). That is, as illustrated in FIG. 1B, when viewed from the cross section (FIG. 1B-1), the first conductive substrate 1
, the first conductive paste layer 4 , the thermoelectric oxide layer 2 , the second conductive paste layer 5 , and the second conductive substrate 3 become more dense as they move toward the upper side of the paper (second conductive substrate 3 ). The size is reduced, and when viewed from above (FIG. 1(n-2)), it has a configuration in which the second conductive substrate 3 is provided without protruding from the thermoelectric conversion oxide layer 2 .
Moreover, it is desirable that the conductive paste layer has a thickness capable of exhibiting an anchor effect while not preventing an increase in the thickness of the entire device.

[First conductive substrate, second conductive substrate]
The conductive substrate (first and second) is not particularly limited as long as it is made of a material having sufficient electrical conductivity. is preferred. For example, a substrate made of a sheet-like conductive metal, a conductive ceramics substrate, an insulating ceramics substrate coated with a conductive metal, or the like can be used.
Among these, from the viewpoint of the flexibility of the thermoelectric conversion module, that is, from the viewpoint of making the thermoelectric conversion element itself thinner, having flexibility in the substrate itself, and being difficult to break, sheet-like conductive metal is used as the conductive substrate material. It can be preferably used.

The conductive metal may be any metal that does not oxidize or melt at the operating temperature of the thermoelectric conversion module. Preferably, noble metal alloys containing about 70% by mass or more, or base metals such as copper, iron, titanium, and aluminum can be used.
Specific examples of the sheet-like conductive metal include copper foil, silver foil, gold foil, and iron foil.
Among them, silver foil (silver sheet) is preferably used from the viewpoint of price, electrical resistivity, thermal conductivity, etc. For example, silver foil having a thickness of about 50 μm to 1 mm can be preferably used.

[Thermoelectric conversion oxide layer]
In the present invention, the material constituting the thermoelectric conversion oxide layer is an oxide known as a thermoelectric conversion material, provided that it can be dispersed in a thermoelectric conversion oxide layer-forming composition described later and applied to form a layer. can be used. From another point of view, manganese-based oxides and cobalt-based oxides having a Seebeck coefficient of −50 μV/K or more at 100° C. can be said to be thermoelectric conversion materials, and these known oxides can be used as starting materials. can.
Moreover, in the thermoelectric conversion oxide layer, the crystallinity of the oxide is not limited. In order to obtain good properties as a thermoelectric conversion layer, it is preferable to be crystalline. A thermoelectric conversion oxide layer with good properties can be obtained by firing the material.
In addition, even if the starting material, for example, a manganese-based oxide or a cobalt-based oxide, contains a carbon component remaining in the manufacturing process, if the carbon component can be decomposed by firing as described later, good thermoelectric properties can be obtained. A thermoelectric conversion oxide layer can be obtained.
Similarly, oxygen atoms in manganese-based oxides and cobalt-based oxides can be introduced in the baking process after coating, so manganese-based oxides with less oxygen atom content than the stoichiometric ratio can be used. and cobalt-based oxides can also be used as starting materials.
In other words, as will be described later, if the composition for forming a thermoelectric conversion oxide layer of the present invention can be applied to a substrate and then subjected to an appropriate baking treatment to obtain sufficient properties as a thermoelectric conversion layer, it is possible to use the composition as a starting material. The oxide may not have sufficient thermoelectric conversion properties.
The thermoelectric conversion layer is an n-type thermoelectric conversion layer made of an oxide composite containing a perovskite-type calcium-manganese oxide represented by the general formula (1) described later, or by the following general formula (2) or (3) It can be a p-type thermoelectric conversion layer made of an oxide composite containing the cobalt-based oxide represented.

<Perovskite-type calcium-manganese-based oxide>
_{CaMn1 - xM1xOy} ( ¹ )
(In the formula, M1 is at least ^one element selected from the group consisting of Nb, Ta, Mo and W, and x and y are 0≤x≤0.1, 2.8≤y≤3. It is a number that satisfies 2.)
Table 1 shows particularly preferred perovskite-type calcium-manganese oxides represented by the general formula (1).

<Cobalt oxide>
_{Ca3 - pBipCo4Oq} ( ₂ )
(In the formula, p and q are numbers satisfying 0≤p≤1 and 8.5≤q≤10.)
_{Bi2Sr2 - rCarCo2Ot ( 3} )
(In the formula, r and t are numbers satisfying 0.0≦r≦2.0 and 8.5≦t≦10.)
Table 2 shows particularly preferred cobalt-based oxides represented by general formula (2) or formula (3).

[Conductive paste layer]
A conductive paste layer is a layer formed from a conductive paste.
The conductive paste layer serves as a bonding agent for bonding the thermoelectric conversion layer to the conductive substrate, and contains a conductive metal containing one or a mixture of two or more of noble metals such as silver, gold, platinum, and palladium. formed from a conductive paste comprising:
The conductive metal is usually blended in the conductive paste in the form of powder. The particle size of the metal powder is not particularly limited, but powder having a particle size with a 50% average particle size in the range of about 0.05 to 50 μm in particle size distribution can be used.

[Method for producing thermoelectric conversion element]
The thermoelectric conversion element of the present invention, for example, a thermoelectric conversion element including a conductive paste layer can be produced by the following steps (1-1) to (1-5). Note that in the case of an embodiment that does not include a conductive paste layer, steps (1-1) and (1-4) are omitted, and the first conductive paste layer in step (1-2) is applied to the first conductive substrate, The second conductive paste layer in step (1-5) can be read as the second conductive substrate.
(1-1) applying a conductive paste on a first conductive substrate and firing to form a first conductive paste layer;
(1-2) a step of applying a thermoelectric conversion oxide layer-forming composition onto the first conductive paste layer to form a coating;
(1-3) baking the coating at 300° C. or higher to form a thermoelectric conversion oxide layer;
(1-4) Separately, a step of applying a conductive paste onto a second conductive substrate and drying to form a second conductive paste layer;
(1-5) The first conductive substrate and the second conductive substrate are stacked so that the thermoelectric conversion oxide layer and the second conductive paste layer are opposed to each other, and are stacked in the stacking direction at 300°C. The process of pressure-pressing in the above.

In still another aspect, the thermoelectric conversion element of the present invention including a conductive paste layer can be produced by the following steps (2-1) to (2-7). Note that in the case of an embodiment that does not include a conductive paste layer, steps (2-1) and (2-4) are omitted, and the first conductive paste layer in step (2-2) is applied to the first conductive substrate, The second conductive paste layer in step (2-5) can be read as the second conductive substrate.
(2-1) applying a conductive paste on a first conductive substrate and firing to form a first conductive paste layer;
(2-2) a step of applying a thermoelectric conversion oxide layer-forming composition onto the first conductive paste layer to form a coating;
(2-3) a step of baking the coating at 300° C. or higher to form a thermoelectric conversion oxide layer 1;
(2-4) Separately, a step of applying a conductive paste on a second conductive substrate and firing to form a second conductive paste layer;
(2-5) a step of applying a thermoelectric conversion oxide layer-forming composition onto the second conductive paste layer to form a coating;
(2-6) a step of baking the coating at 300° C. or higher to form a thermoelectric conversion oxide layer 2;
(2-7) The first conductive substrate and the second conductive substrate are laminated so that the thermoelectric conversion oxide layer 1 and the thermoelectric conversion oxide layer 2 are opposed to each other, and are laminated at 300° C. in the stacking direction. The process of pressure-pressing in the above.
The above (2-1) to (2-3) steps and (2-4) to (2-6) steps follow the above (1-1) to (1-3) steps, and (2-7) step can be carried out following the above (1-5) step.

(1-1) Step of applying a conductive paste onto a first conductive substrate and firing to form a first conductive paste layer:
In this step, first, the conductive paste is applied onto the conductive substrate by a screen printing method or the like.
After the application, the solvent and the like contained in the conductive paste are dried, for example, at around 100° C., and then baked if necessary. Although the firing temperature is not particularly limited, for example, firing at a temperature of about 500 to 900° C. strengthens the bonding with the conductive substrate, and also serves as an anchor effect for the thermoelectric conversion oxide layer described later. can do.

(1-2) a step of applying a thermoelectric conversion oxide layer-forming composition onto the first conductive paste layer to form a coating;
The thermoelectric conversion oxide layer-forming composition used in this step contains the thermoelectric conversion material described above, that is, the perovskite-type calcium-manganese-based oxide or cobalt-based oxide, and a dispersion medium. The method for preparing the thermoelectric conversion layer-forming composition is not particularly limited, and an appropriate amount of the above-mentioned oxide, dispersion medium, etc. may be added to a reaction (mixing) vessel and mixed, and wet pulverization, ball mill treatment, etc. may be performed as necessary. good.
The composition may optionally contain a polysaccharide such as ethyl cellulose for the purpose of improving the dispersibility and coatability of the oxide, and a conductive paste or the like as a conductive aid.

In the present invention, in order to disperse the oxides (perovskite-type calcium-manganese-based oxides, cobalt-based oxides) in the dispersion medium, the oxides are preferably in the form of particles, with an average particle diameter of 1 nm. It is preferable to use an oxide having a diameter of about 100 μm because a uniform dispersion (thermoelectric conversion oxide layer-forming composition) can be easily prepared. Note that the particle diameter is 1
If the particle size is less than 100 μm, the particles aggregate and become difficult to disperse. The average particle size is preferably 5 μm or less, more preferably 1 μm or less, from the viewpoint of the coating properties of the dispersion (composition), the thermoelectric properties of the thermoelectric conversion oxide layer, and the like. Here, the average particle size is obtained as a 50% average particle size according to the particle size distribution.
The average particle size of the oxide as the starting material may be 1 nm or more, and even if the particle size of the starting material is 100 μm or more, after mixing with the dispersion medium etc. By pulverizing the particles, an oxide having a particle size that can be dispersed in the dispersion medium can be obtained.

As the dispersion medium, an organic solvent or insulating water is preferably used. Examples of organic solvents include terpineol (main component is α-terpineol), alcohols such as phenoxyethanol, aliphatic halogen solvents such as chloroform, N,N-dimethylformamide (DMF), N-methyl-2-pyrrolidone (NMP ), aprotic polar solvents such as dimethyl sulfoxide (DMSO), aromatic solvents such as chlorobenzene, dichlorobenzene, benzene, toluene, xylene, mesitylene, tetralin, tetramethylbenzene, pyridine, cyclohexanone, acetone, methyl ethyl kentone ketone solvents such as diethyl ether, tetrahydrofuran (THF), t-butyl methyl ether, dimethoxyethane and diglyme, and hydrocarbon solvents such as decane, undecane, dodecane, tridecane and tetradecane. Among these organic solvents, one type can be used alone, or two or more types can be used in combination.

In the thermoelectric conversion oxide layer-forming composition, the amount (% by mass) of the oxides (perovskite-type calcium manganese-based oxide, cobalt-based oxide) can be, for example, 0.1 to 90% by mass. . If the oxide concentration is too high, the composition will not have fluidity, making it difficult to obtain a thermoelectric conversion oxide layer by a coating method. On the other hand, if the solid content concentration is too low, the composition cannot form a uniform film.
When the above-described conductive paste is blended as the above-described conductive aid, the blending amount thereof can be 10 to 30% by mass with respect to the above-described thermoelectric conversion oxide layer-forming composition.

The method and apparatus for applying the above composition onto the conductive paste layer (or the conductive substrate) to obtain a film are not particularly limited. For example, coating methods such as spin coating, blade coating, bar coating, roll coating, curtain coating, spray coating, dip coating, and screen printing are used, and known devices can be used for these methods.

(1-3) Step of baking the film at 300° C. or higher to form a thermoelectric conversion oxide layer In this step, the film obtained in the above step is baked to form the oxide (perovskite-type calcium manganese Cobalt-based oxide) is sintered to obtain a thermoelectric conversion oxide layer.
The calcination of the coating removes and decomposes components that do not participate in thermoelectric properties such as dispersion media and polysaccharides, and components that may adversely affect thermoelectric properties such as carbon components, crystallizes the oxides, and For the purpose of sintering the oxide, it can be carried out at a temperature and time suitable for the purpose, for example, it can be carried out at 300° C. or higher in an oxidizing atmosphere. However, if the firing temperature is too high, the phase transition of the perovskite-type calcium-manganese-based oxide and the cobalt-based oxide changes the thermoelectric properties, so the upper limit of the firing temperature is limited by the phase transition temperature of the oxide. For example, when CaMn _0.98 Mo _0.02 O ₃ is used as the perovskite-type calcium-manganese-based oxide, the thermoelectric properties change when fired at 1300° C. or higher. When Ca ₃ Co ₄ O ₉ is used as the system oxide, it has a phase transition temperature of 860° C., so the firing temperature is preferably 850° C. or less.
The baking can be performed by heating with an oven or the like, or by light baking (photosintering) using light irradiation such as ultraviolet light, visible light, and flash light. Moreover, heat baking and light baking can also be used together.

(1-4) Separately, a step of applying a conductive paste on a second conductive substrate and drying to form a second conductive paste layer. After drying, it can be carried out in the same manner as the above-mentioned step (1-1), except that the baking is not carried out.

(1-5) The first conductive substrate and the second conductive substrate are stacked so that the thermoelectric conversion oxide layer and the second conductive paste layer are opposed to each other, and are stacked in the stacking direction at 300°C. The step of pressurizing in the above step This step includes the substrate obtained in steps (1-1) to (1-3) (first conductive substrate-first conductive paste layer-thermoelectric conversion oxide layer) and the substrate (second conductive substrate-second conductive paste layer) obtained in step (1-4), these conductive substrates facing outward, and the thermoelectric conversion oxide layer and the second After stacking the conductive paste layers so that they face each other, they are press-pressed in the stacking direction (perpendicular to the bonding surface). After pressure pressing, the thermoelectric conversion oxide layer and the second conductive paste layer are bonded to obtain a thermoelectric conversion element as a laminate.
The pressurization can be performed at a pressure that does not damage or deform the thermoelectric conversion layer, the conductive substrate, etc., for example, at a pressure of 1 to 20 MPa and a temperature of about 500 to 1000.degree.

According to the manufacturing method of the present invention, the first conductive paste layer and the thermoelectric conversion oxide layer having approximately the same size are formed on the first conductive substrate, while the first conductive substrate has the same size. When adopting a smaller size of the second conductive substrate (for example, 1/3 to 1/10 the size of the first conductive substrate) and making them face each other, (the first conductive substrate A plurality of second conductive substrates (on which the second conductive paste layers are formed) can be arranged at appropriate intervals on the thermoelectric conversion oxide layer (on the substrate). Then, after pressure pressing, the thermoelectric conversion oxide layer portion exposed between one second conductive substrate and another second conductive substrate is moved in the stacking direction (thermoelectric conversion oxide layer-first It is possible to obtain a plurality of thermoelectric conversion elements by cutting the conductive paste layer (first conductive substrate).

The thermoelectric conversion element of the present invention comprises an element having an n-type thermoelectric conversion layer made of an oxide composite containing a perovskite-type calcium-manganese-based oxide as a thermoelectric conversion oxide layer (hereinafter referred to as an n-type thermoelectric conversion element), and a cobalt-based An element having a p-type thermoelectric conversion layer made of an oxide composite containing an oxide (hereinafter referred to as a p-type thermoelectric conversion element) is arranged in parallel with the temperature difference direction, and these n-type/p-type thermoelectric conversion elements are arranged above and below. A thermoelectric conversion module (also referred to as a thermoelectric power generation module) can be created by electrically connecting a plurality of thermoelectric conversion elements in series with the connection wiring and pulling out lead wires or the like from the end of the series connection.

EXAMPLES The present invention will be described in more detail below with reference to Examples, but the present invention is not limited by the following description.

[ _Production of _{Ca2.7Bi0.3Co4O9 powder ]}
The Ca _2.7 Bi _0.3 Co ₄ O ₉ powder used in this example was synthesized as follows with reference to Japanese Unexamined Patent Publication No. 2003-246678.
First, calcium carbonate (CaCO ₃ ), bismuth oxide (Bi ₂ O ₃ ) and cobalt oxide (Co ₃ O ₄ ) are mixed in a stoichiometric ratio (Ca:Bi:Co=2.7:0.3:4). and mixed in a mortar. Next, the mixed sample was placed in an alumina crucible and fired in air at 800° C. for 10 hours, and the resulting fired product was thoroughly mixed using an agate mortar and pestle to obtain powder. This powder was press-molded into a disc having a diameter of 20 mm and a thickness of about 2 to 10 mm to obtain a compact. A gold sheet was laid on an alumina boat, the compact was placed thereon, and heated in the air at 880°C.
After firing for 20 hours, a sintered body was obtained. Next, the resulting sintered body was pulverized using an agate mortar and pestle, and a metal sieve with an opening of 38 μm was used to obtain Ca _2.7 Bi _0.3 Co ₄ O ₉ powder that had passed through the metal sieve. Obtained.

[ _Production of _{CaMn0.98Mo0.02O3 powder} ]
The CaMn _0.98 Mo _0.02 O ₃ powder used in this example was synthesized as follows with reference to the content disclosed in JP-A-2009-117449.
First, calcium carbonate (CaCO ₃ ), manganese oxide (Mn ₂ O ₃ ), and molybdenum oxide (MoO ₃ ) were mixed in a stoichiometric ratio (Ca:Mn:Mo=1:0.98:0.02). Weighed and mixed in a mortar. Next, the mixed sample was placed in an alumina crucible and calcined in air at 1000° C. for 15 hours, and the calcined product was pulverized and mixed in a mortar to obtain a powder. The obtained powder was press-molded into a disc having a diameter of 20 mm and a thickness of about 2 to 10 mm to obtain a compact. A single-phase CaMn _0.98 Mo ₀ sintered body was obtained by repeating the operation of laying a gold sheet on an alumina boat, placing the molded body on it, and firing in the air at 1250 ° C. for 12 hours twice. _{.02 O3} was made. Next, the resulting sintered body was pulverized using an agate mortar and pestle, and a metal sieve with an opening of 38 μm was used to obtain CaMn _0.98 Mo _0.02 O ₃ powder that passed through the metal sieve. .

Ca ₃ Co ₄ O ₉ powder used in this example has a BET specific surface area of 70 m ² /g as measured by _Macsorb HM model _- 1208 manufactured by _Mountec Co., Ltd.

[Preparation Example 1: Preparation of thermoelectric conversion layer forming liquid 1 (1)]
Ca _2.7 Bi _0.3 Co ₄ O ₉ powder (8 g, 100 parts by weight), Ca ₃ Co ₄ O ₉ powder (2 g, 25 parts by weight) and α-terpineol (8 g, 100 parts by weight) were put into a bottle. , using a rotation-revolution mixer (Awatori Mixer, manufactured by Thinky Co., Ltd.) at 2,000 rpm for 4 minutes, the mixture was repeatedly mixed 10 times to obtain a thermoelectric conversion layer-forming liquid 1 (composition C).

[Preparation Example 2: Preparation of thermoelectric conversion layer forming liquid 2 (2)]
CaMn _0.98 Mo _0.02 O ₃ powder (8 g, 100 parts by mass), silver paste (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., product name: MH-108A-10) (2 g, 25 parts by mass) and α-terpineol (8 g, 100 parts by mass) is put in a bottle and mixed repeatedly 10 times under the conditions of 2,000 rpm and 4 minutes using a rotation-revolution mixer (manufactured by Thinky Co., Ltd., Awatori Mixer) to form a thermoelectric conversion layer. Liquid 2 (composition M) was obtained.

[Example 1: Preparation of thermoelectric conversion element 1 (p-type thermoelectric conversion element) (1)]
A silver paste (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., product name: MH-108A-10) was applied by screen printing on silver foil 1 (thickness 50 μm, size 20 mm × 20 mm), and baked at 860 ° C. After obtaining a silver paste layer 1, a thermoelectric conversion layer forming liquid 1 (composition C) was applied thereon to a liquid thickness of 200 μm and fired at 850° C. to obtain a thermoelectric conversion layer.
Separately, a silver paste (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., product name: MH-108A-10) was applied by screen printing on 64 sheets of silver foil 2 (thickness: 100 µm, size: 2 mm x 2 mm), and the temperature was 100°C. to obtain a silver paste layer 2.
Next, these 64 silver foils 2 are arranged with equal intervals of 0.5 mm in length and width so that there are 8 sheets in each length and width, and the thermoelectric conversion layer of the silver foil 1 and the silver paste layer 2 of the silver foil 2 are arranged. They were stacked so as to face each other and pressurized (30 kgf/cm ² ) at 950° C. in the stacking direction. The thermoelectric conversion layer was strongly bonded to the silver foil 2 via the silver paste layer 2 to obtain a thin laminate.
Finally, in the laminate, a cutting blade is passed through the gap (0.5 mm) between the silver foils 2 arranged vertically and horizontally to form a piece of about 2.1 to 2.2 mm×2.1 to 2.1 mm. A small piece of 2 mm size is cut, and it has a laminated structure of silver foil 1-silver paste layer 1-thermoelectric conversion layer-silver paste layer 2-silver foil 2, and the size of the two silver foils is different (area: silver foil 1 > silver foil 2 ) Thermoelectric conversion elements 1 (64 pieces) were obtained. No cracks or peeling was observed in the obtained thermoelectric conversion element 1 .

[Example 2: Production of thermoelectric conversion element 2 (n-type thermoelectric conversion element) (2)]
A thermoelectric conversion element 2 was produced in the same procedure as in Example 1, except that the thermoelectric conversion layer forming liquid 2 (composition M) was used instead of the thermoelectric conversion layer forming liquid 1 (composition C). No cracking or peeling was observed in the thermoelectric conversion element 2 .

[Comparative Example 1]
A silver paste (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., product name: MH-108A-10) was applied by screen printing onto the silver foil H1 (thickness: 200 μm, size: 20 mm x 20 mm) and baked at 860°C. After obtaining a silver paste layer H1-1, the thermoelectric conversion layer forming liquid 1 (composition C) was applied thereon to a liquid thickness of 200 μm and fired at 850 ° C. to obtain a thermoelectric conversion layer H1-1. .
Separately, silver paste (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., product name: MH-108A-10) was applied by screen printing on silver foil H2 (thickness 200 μm, size 20 mm × 20 mm), and was applied at 860 ° C. After firing to obtain the silver paste layer H1-2, the thermoelectric conversion layer forming liquid 1 (composition C) was applied thereon to a liquid thickness of 200 μm and fired at 850° C. to form the thermoelectric conversion layer H1-2. Obtained.
The silver foil 1 and the silver foil 2 are stacked so that the thermoelectric conversion layer H1-1 and the thermoelectric conversion layer H1-2 face each other, heated at 450 ° C., after removing the organic component, pressurized at 930 ° C. in the stacking direction. (30 kgf/cm ² ). The thermoelectric conversion layer H1-1 and the thermoelectric conversion layer H1-2 were strongly bonded to each other to obtain a thin laminate.
Finally, when an attempt was made to cut the laminate into small pieces of 2.0 mm x 2.0 mm size using a cutting machine, the silver foil on the side where the blade was applied was peeled off from the thermoelectric conversion layer due to the impact of cutting, and the laminate was cut. It was not possible to obtain a retained piece of element.

[Comparative Example 2]
Silver paste (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., product name: MH-108A-10) was applied by screen printing onto a PET sheet (thickness: 220 µm, size: 4 mm x 7 mm), and dried at 100°C. After obtaining the silver paste layer H2-1, the thermoelectric conversion layer forming liquid 1 (composition C) was applied thereon to a liquid thickness of 200 μm and fired at 850° C. to obtain the thermoelectric conversion layer H2.
Next, on the thermoelectric conversion layer, a silver paste (manufactured by Tanaka Kikinzoku Kogyo Co., Ltd., product name: MH-108A-10) is applied by screen printing (conditions), dried at 100 ° C., and silver paste is applied. Layer H2-2 was obtained.
Finally, this sheet was pressure-pressed (30 kgf/cm ² ) at 950° C. in the stacking direction. After pressing, a thin piece having silver films formed on both sides of the thermoelectric conversion layer H2 was obtained, but it collapsed when lifted, and a self-supporting element was not obtained.

[Resistance measurement]
As a result of measuring the resistance values of the thermoelectric conversion element 1 and the thermoelectric conversion element 2 obtained by the above procedure, both showed about 0.8Ω.
In addition, the measurement of the resistance value was performed by the DC four-terminal method. A platinum wire is connected to the surface of silver foil 1 and silver foil 2 using silver paste, each platinum wire is connected to an ammeter and a voltmeter, current is applied at 1 mA or 10 mA, the voltage at that time is calculated, and the current ( The slope of a straight line (horizontal axis) - voltage (vertical axis) was taken as electrical resistance.

[Example 3 Fabrication of thermoelectric conversion module (thermoelectric power generation module)]
Using the thermoelectric conversion element 1 (p-type thermoelectric conversion element) obtained in Example 1 and the thermoelectric conversion element 2 (n-type thermoelectric conversion element) obtained in Example 2, a thermoelectric conversion module was produced.
First, on a Kapton (polyimide) film of 34 mm × 38 mm square and 65 µm thick having an adhesive layer on one side, 50 silver sheets 1 of 2 mm × 5 mm and 100 µm thick were arranged with a gap of 1.5 mm. , was fixed using adhesiveness (Fig. 2(A)).
A conductive silver paste (die bonding paste, trade name: DBC130SD) was applied from both ends of each silver sheet 1 to about 2 mm inside. A total of 50 thermoelectric conversion elements 1 (p-type element in the figure) and 2 thermoelectric conversion elements 2 (n-type element in the figure) of Example 1 were alternately placed on the silver paste. , 180° C. for 20 minutes in air to solidify the silver paste. At this time, the side of the silver foil 1 having a large area of each thermoelectric conversion element was adhered to the silver paste (FIG. 2(B)).
Next, a conductive silver paste (die bonding paste, trade name: DBC130SD) was applied on the silver foil 2 having a small area of each thermoelectric conversion element so as not to protrude from the silver foil. A silver sheet 2 having a length of 5 mm, a width of 1 mm, and a thickness of 100 μm was placed thereon so as to connect adjacent thermoelectric conversion elements 1 and 2 that were not connected by the silver sheet 1. . In this way, 50 pairs of thermoelectric conversion elements were connected in series, and 80 mm long silver sheets 3 were connected to the thermoelectric conversion elements at both ends to form power extraction lines (Fig. 2(C)).
Finally, a hot plate is used to heat in the air at 180° C. for 20 minutes to solidify the silver paste to produce a thermoelectric conversion module composed of 50 pairs of p-type thermoelectric conversion elements and n-type thermoelectric conversion elements. did. FIG. 3 shows a cross-sectional view of the thermoelectric conversion module obtained. The obtained thermoelectric conversion module was flexible.

The power output of the thermoelectric conversion module was measured by a four-terminal method. A pair of terminals was connected to a DC ammeter to measure the current output from the thermoelectric conversion module while varying the external load. At the same time, the voltage was measured at the other pair of terminals connected to the voltmeter.
The surface of the thermoelectric conversion module on the Kapton side was heated with a hot plate, and a heat-conducting and electrically insulating film was placed on the opposite surface. . An external resistor was connected to the lead wire of the thermoelectric conversion module (Fig. 2 (C) and Fig. 3: silver sheet 3), and the voltage and current were measured while changing the value of the resistance, and the maximum power output was obtained from the voltage x current. . Table 3 shows the surface temperature of the hot plate and the power output.

As shown in Table 3, the thermoelectric conversion module produced using the thermoelectric conversion element (p-type thermoelectric conversion element, n-type thermoelectric conversion element) of the present invention has thermoelectric conversion ability, and the amount of thermal energy (hot plate surface It was confirmed that the maximum power output increased as the temperature) increased.

Claims (7)

a first conductive substrate;
a thermoelectric conversion oxide layer provided on the upper side of the first conductive substrate;
A second conductive substrate provided on the upper side of the thermoelectric conversion oxide layer is laminated in this order,
The outer periphery of the second conductive substrate is a thermoelectric conversion element formed on or inside the outer periphery of the thermoelectric conversion oxide layer,
Regarding the area of each layer, [Area of first conductive substrate]≧[Area of thermoelectric conversion oxide layer]≧[Area of second conductive substrate] and [Area of first conductive substrate]> The relationship of [the area of the second conductive substrate] is established,
Regarding the thickness of each layer [thickness of thermoelectric conversion oxide layer]: <[thickness of first conductive substrate] + [thickness of second conductive substrate]> = 1:1 to 1:10 A thermoelectric conversion element characterized in that the relationship of A first conductive paste layer is formed between the first conductive substrate and the thermoelectric conversion oxide layer, and a second conductive paste layer is formed between the thermoelectric conversion oxide layer and the second conductive substrate. A paste layer is formed,
The thermoelectric conversion element according to claim 1. The thermoelectric conversion oxide layer has an area of 0.5 mm ² to 20 mm ² ,
The thermoelectric conversion element according to claim 1 or 2. The thermoelectric conversion oxide layer is
General formula (1):
_{CaMn1 - xM1xOy} ( ¹ )
(In the formula, M1 is at least ^one element selected from the group consisting of Nb, Ta, Mo and W, and x and y are 0≤x≤0.1, 2.8≤y≤3. It is a number that satisfies 2.)
An n-type thermoelectric conversion layer made of an oxide composite containing a perovskite-type calcium manganese oxide represented by
General formula (2) or general formula (3):
_{Ca3 - pBipCo4Oq} ( ₂ )
(In the formula, p and q are numbers satisfying 0≤p≤1 and 8.5≤q≤10.)
_{Bi2Sr2 - rCarCo2Ot ( 3} )
(In the formula, r and t are numbers satisfying 0.0≦r≦2.0 and 8.5≦t≦10.)
A p-type thermoelectric conversion layer made of an oxide composite containing a cobalt-based oxide represented by
The thermoelectric conversion element according to any one of claims 1 to 3. A method for manufacturing a thermoelectric conversion element,
applying a conductive paste on a first conductive substrate and baking to form a first conductive paste layer;
applying a thermoelectric conversion oxide layer-forming composition onto the first conductive paste layer to form a coating;
a step of baking the coating at 300° C. or higher to form a thermoelectric conversion oxide layer;
Separately, a step of applying a conductive paste on a second conductive substrate and drying to form a second conductive paste layer;
The first conductive substrate and the second conductive substrate are stacked so that the thermoelectric conversion oxide layer and the second conductive paste layer face each other, and the layers are pressed at 300° C. or higher in the stacking direction. the process of pressing,
and a method for manufacturing a thermoelectric conversion element. A method for manufacturing a thermoelectric conversion element,
applying a conductive paste on a first conductive substrate and baking to form a first conductive paste layer;
applying a thermoelectric conversion oxide layer-forming composition onto the first conductive paste layer to form a coating;
a step of baking the coating at 300° C. or higher to form a thermoelectric conversion oxide layer 1;
Separately, a step of applying a conductive paste on a second conductive substrate and baking to form a second conductive paste layer;
applying a thermoelectric conversion oxide layer-forming composition onto the conductive second conductive paste layer to form a coating;
a step of baking the coating at 300° C. or higher to form a thermoelectric conversion oxide layer 2;
The first conductive substrate and the second conductive substrate are stacked so that the thermoelectric conversion oxide layer 1 and the thermoelectric conversion oxide layer 2 face each other, and are press-pressed at 300° C. or higher in the stacking direction. the process of
and a method for manufacturing a thermoelectric conversion element. A plurality of the thermoelectric conversion elements according to claim 4 are used, and the unjoined end portion of the p-type thermoelectric conversion element having the p-type thermoelectric conversion layer is connected to the unjoined n-type thermoelectric conversion element having the n-type thermoelectric conversion layer. A thermoelectric power generation module in which a plurality of thermoelectric conversion elements are connected in series by a method of connecting on a substrate to the end of the

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