TW201829572A - Composition for forming thermoelectric conversion layer and production method for thermoelectric conversion layer - Google Patents

Abstract

To provide a composition for thermoelectric conversion layer formation where water serves as the dispersion medium. To produce a thermoelectric conversion layer by a coating process using a composition for thermoelectric conversion layer formation. Provided is a composition for thermoelectric conversion layer formation which comprises (A) water, (B) a cobalt-based oxide, and (C) a polysaccharide. In terms of 100 parts by mass of the composition, the total of (A) and (B) is 90 to 99.98 parts by mass, (B) is 1 to 50 parts by mass, and (C) is 0.02 to 10 parts by mass.

Description

Thermoelectric conversion layer forming composition and method of manufacturing thermoelectric conversion layer

[0001] The present invention relates to a method for producing a thermoelectric conversion layer forming composition for forming a thermoelectric conversion layer and a thermoelectric conversion layer using the composition for forming a thermoelectric conversion layer.

[0002] The electromotive force formed by the Seebeck effect is proportional to the temperature difference between the high temperature portion and the low temperature portion of the thermoelectric conversion element, and is increased in the conventional thermoelectric conversion module in order to increase the temperature difference. It is a block-shaped thermoelectric conversion element. However, the block-shaped thermoelectric conversion element has a problem that it is difficult to perform fine processing and the unit price of the power generation of the module is high. Therefore, in recent years, studies have been made on thermoelectric conversion elements and thermoelectric conversion modules using a coating process which is easy to perform fine processing. Among them, from the viewpoint of environmental protection, it is strongly expected to develop a composition for forming a thermoelectric conversion layer containing water as a main dispersion medium. [0003] As a thermoelectric conversion layer formed by a coating process using water, Patent Document 1 discloses a method of forming a film on a support using a water-based composition containing semiconductor fine particles and a conductive polymer. Further, Patent Document 2 discloses that a thermoelectric conversion sheet is produced from a water-based composition containing metal nanoparticles and a water-soluble conductive polymer. Patent Document 3 discloses that a conjugated conductive polymer is dissolved in water to produce a flexible thermoelectric conversion layer. On the other hand, Patent Document 4 discloses a thermoelectric conversion layer in which a cobalt-based oxide is produced using α-terpineol as a solvent. CITATION LIST Patent Literature [Patent Document 1] Japanese Patent Publication No. 2014-30010 Patent Document 3: JP-A-2014-199838 Patent Document 4: JP-A-2008 Bulletin No. -270410

[Problems to be Solved by the Invention] [0005] Patent Document 1 to Patent Document 3 is a composition for forming a thermoelectric conversion layer in which a thermoelectric conversion material is dispersed or dissolved in water, and a thermoelectric conversion layer is produced by a coating process. technology. However, these prior art techniques use a thermoelectric conversion material having low heat resistance and do not have heat resistance in a medium-high temperature region (300 to 600 ° C). [0006] Patent Document 4 uses an organic solvent in order to produce a thermoelectric conversion layer. In the thermoelectric conversion layer in the medium-high temperature region, there is no example of a composition for forming a thermoelectric conversion layer using water as a solvent or a dispersion medium. An object of the present invention is to provide a thermoelectric conversion layer forming composition which is applicable to a medium-high temperature region of 300 to 600 ° C and which uses water as a dispersion medium. Further, an object of the present invention is to produce a thermoelectric conversion layer by a coating process using a composition for forming a thermoelectric conversion layer. [Means for Solving the Problem] The present invention has been intensively studied to solve the above problems, and as a result, a thermoelectric conversion layer containing (A) water, (B) cobalt-based oxide, and (C) polysaccharide has been found. The composition for formation has good dispersibility and applicability, and it has been found that the polysaccharide contained in the film produced by the composition for forming the thermoelectric conversion layer can be produced by firing in an oxidizing atmosphere. The present invention has been completed in the absence of a thermoelectric conversion layer having excellent thermoelectric properties of a component which hinders thermoelectric properties. According to the present invention, the first aspect of the invention provides a thermoelectric conversion layer forming composition comprising (A) water, (B) a cobalt-based oxide, and (C) a polysaccharide-based thermoelectric conversion layer. The composition is 90 to 99.98 parts by mass in total of (A) and (B), (B) is 1 to 50 parts by mass, and (C) is 0.02 to 10 parts by mass based on 100 parts by mass of the composition. The thermoelectric conversion layer forming composition of the first aspect, wherein the polysaccharide is a cellulose derivative, and the thermoelectric conversion layer forming composition according to claim 2, wherein the cellulose derivative The composition for forming a thermoelectric conversion layer according to any one of the first aspect to the third aspect, wherein the cobalt-based oxide is represented by the following general formula (1): (wherein A ¹ is a group selected from the group consisting of Na, K, Li, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Pb, Sr, Ba, Al, Bi, Y, and lanthanum elements. At least one element of the group, A ² is at least one element selected from the group consisting of Ti, V, Cr, Mn, Fe, Ni, Cu, Ag, Mo, W, Nb, and Ta, 2.2≦a1≦3.6; 0≦b1≦0.8;2.0≦c1≦4.5;0≦d1≦2.0;8≦e1≦10), or with the following general formula (2): (wherein A ¹ is a group selected from the group consisting of Na, K, Li, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Pb, Sr, Ba, Al, Bi, Y, and lanthanum elements. a group of at least one element, A ² being at least one element selected from the group consisting of Ti, V, Cr, Mn, Fe, Ni, Cu, Ag, Mo, W, Nb, and Ta, 0 < a2 ≦ 2; 0≦b2≦0.6;0<c2≦2;0≦d2≦0.6;1.0≦e2≦3.0), or is the general formula (3) below: (wherein M ¹ is Sr or Pb, and A ¹ is selected from the group consisting of Na, K, Li, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Pb, Sr, Ba, Al, Bi, Y and At least one element of the group consisting of lanthanum elements, A ² being at least one element selected from the group consisting of Ti, V, Cr, Mn, Fe, Ni, Cu, Ag, Mo, W, Nb, and Ta , 1.8≦a3≦2.2; 0≦f3≦0.4; 1.8≦b3≦2.2; 1.6≦c3≦2.2; 0≦d3≦0.5; 8≦e3≦10) the compound represented; the fifth viewpoint is a thermoelectric conversion layer The manufacturing method of the thermoelectric conversion layer forming composition according to any one of the first aspect to the fourth aspect, comprising the step of applying a thermoelectric conversion layer forming composition to a substrate to form a film; and subsequently, in order to remove the polysaccharide from the film, The method of firing the film in an oxidizing atmosphere of 300 ° C or higher; the sixth aspect is a method for producing a thermoelectric conversion layer, comprising: forming a thermoelectric conversion layer according to any one of the first aspect to the fourth aspect; a step of forming a film by coating a composition on a substrate; and then, in order to remove the polysaccharide from the film, the film is irradiated with light by irradiation in an oxidizing atmosphere. The method of producing a thermoelectric conversion layer according to any one of the first aspect to the fourth aspect, wherein the thermoelectric conversion layer forming composition is applied to a substrate to form a film. a step of firing the film in an oxidizing atmosphere at 300 ° C or higher in order to remove the polysaccharide from the film; and then subjecting the film to photo-sintering by light irradiation in an oxidizing atmosphere. [Effects of the Invention] In the present invention, since water is used as a main solvent, it is possible to provide a composition for forming a thermoelectric conversion layer which is less polluted in the environment and the working environment. Further, by using the composition, it is possible to provide a thermoelectric conversion layer which has heat resistance in a medium-high temperature region, is excellent in thermoelectric characteristics, and has processability and shape freedom.

[0012] Hereinafter, the present invention will be described in detail. The thermoelectric conversion layer forming composition of the present invention is a composition of a thermoelectric conversion layer composed of a cobalt-based oxide by being applied to a substrate and fired. That is, in the composition, the cobalt-based oxide for forming the thermoelectric conversion layer is dispersed in the state of fine particles, and the water and the polysaccharide contained in the composition are used for improving the dispersion of the cobalt-based oxide. The composition of the state. [0013] The basic characteristics of the thermoelectric conversion layer are determined by the type of the cobalt-based oxide dispersed in the thermoelectric conversion layer-forming composition. In other words, the cobalt-based oxide dispersed in the thermoelectric conversion layer-forming composition of the present invention can be directly used as a thermoelectric conversion material composed of a known cobalt-based oxide as long as it can be dispersed in water. From other viewpoints, a cobalt-based oxide having a Sibeck coefficient of 50 μV/K or more at 100 ° C may also be referred to as a thermoelectric conversion material, and in the present invention, such a known cobalt-based oxide may be used as a starting material. . [0014] When the thermoelectric conversion layer forming composition of the present invention is formed into a thermoelectric conversion layer, the polysaccharide is added to the particles of the cobalt-based oxide. By adding a polysaccharide, even after the drying of the thermoelectric conversion layer forming composition, the particles are not peeled off from the substrate during the film formation of the thermoelectric conversion layer, and can be present as a thermoelectric conversion layer on the substrate. on. On the other hand, when the polysaccharide is not contained, when the composition is dried, the cobalt-based oxide particles are likely to fall off from the substrate and cannot exist as a thermoelectric conversion layer. When the polysaccharide is contained in a large amount, the electrical resistance of the thermoelectric conversion layer is deteriorated. However, by burning and decomposing at a high temperature of 300 ° C or higher, good electrical conductivity can be obtained. Although the polysaccharide is not present in the thermoelectric conversion layer after firing, since the cobalt-based oxides are weakly melted, they can exist as a layer. The polysaccharide also has an effect of improving the dispersibility of the cobalt-based oxide fine particles in water. Further, the thermoelectric conversion layer of the cobalt-based oxide obtained by the composition for forming a thermoelectric conversion layer of the present invention is not limited in crystallinity. In order to obtain good characteristics as a thermoelectric conversion layer, it is preferably crystallized. However, for example, if the starting material is amorphous, the composition for forming a thermoelectric conversion layer is applied to a substrate, and then fired by crystallization. A thermoelectric conversion layer with good characteristics can be obtained. Further, in the starting material of the cobalt-based oxide, for example, if the carbon component remaining in the production process is contained in the cobalt-based oxide, if the carbon component can be decomposed by firing, thermoelectric characteristics can be obtained. Good thermoelectric conversion layer. Further, similarly, the oxygen atom of the cobalt-based oxide can be introduced in the calcination step after coating, so that a cobalt-based oxide having a smaller oxygen content than the stoichiometric ratio can be used. [0019] In the case where the composition for forming a thermoelectric conversion layer of the present invention is applied to a substrate, if sufficient characteristics as a thermoelectric conversion layer can be obtained by a suitable baking treatment, the cobalt as a starting material is used. The oxide may not have sufficient thermoelectric conversion characteristics. [0020] The cobalt-based oxide is represented by the following general formula (1), (2) or (3). General formula (1): (wherein A ¹ is a group selected from the group consisting of Na, K, Li, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Pb, Sr, Ba, Al, Bi, Y, and lanthanum elements. At least one element of the group, A ² is at least one element selected from the group consisting of Ti, V, Cr, Mn, Fe, Ni, Cu, Ag, Mo, W, Nb, and Ta, 2.2≦a1≦3.6; 0≦b1≦0.8; 2.0≦c1≦4.5; 0≦d1≦2.0; 8≦e1≦10) A particularly preferred cobalt-based oxide represented by the general formula (1) is shown in Table 1. [0021] [0022] In the above general formula (1), the lanthanum element may be exemplified by La, Ce, Pr, Nd, Sm, Eu, Gd, Dy, Ho, Er, Tm, Yb, Lu, and the like. [0023] General formula (2): (wherein A ¹ is a group selected from the group consisting of Na, K, Li, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Pb, Sr, Ba, Al, Bi, Y, and lanthanum elements. a group of at least one element, A ² being at least one element selected from the group consisting of Ti, V, Cr, Mn, Fe, Ni, Cu, Ag, Mo, W, Nb, and Ta, 0 < a2 ≦ 2; 0≦b2≦0.6; 0<c2≦2;0≦d2≦0.6; 1.0≦e2≦3.0) [0024] General formula (3): (wherein M ¹ is Sr or Pb, and A ¹ is selected from the group consisting of Na, K, Li, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Pb, Sr, Ba, Al, Bi, Y and At least one element of the group consisting of lanthanum elements, A ² being at least one element selected from the group consisting of Ti, V, Cr, Mn, Fe, Ni, Cu, Ag, Mo, W, Nb, and Ta , 1.8≦a3≦2.2; 0≦f3≦0.4; 1.8≦b3≦2.2; 1.6≦c3≦2.2; 0≦d3≦0.5; 8≦e3≦10) [0025] In the present invention, in order to make the cobalt-based oxide Dispersed in water, the cobalt-based oxide must be in the form of particles. When the average particle diameter of the cobalt-based oxide is from 1 nm to 100 μm, a uniform dispersion can be easily prepared. When it is 1 nm or less, the particles are agglomerated and are not easily dispersed. When the particles are 100 μm or more, not only the dispersibility is deteriorated, but also a problem that a uniform thermoelectric conversion layer cannot be formed is obtained. The average particle diameter is preferably 5 μm or less, and particularly preferably 1 μm or less, from the viewpoints of the coatability of the dispersion and the thermoelectric characteristics of the thermoelectric conversion layer. Here, the average particle diameter is a particle diameter measured by a dynamic light scattering method using Nanotrac UPA-EX manufactured by Microtrac Bel. The starting material in the case of preparing the thermoelectric conversion layer-forming composition of the present invention is not particularly limited as long as the average particle diameter of the cobalt-based oxide is 1 nm or more. Even if the particle diameter of the starting material is 100 μm or more, the particles may be pulverized by wet pulverization after mixing with water to obtain a cobalt-based oxide which can be dispersed in the particle diameter of water. [0027] The polysaccharide is a generic term for a substance in which a monosaccharide molecule is polymerized by two or more molecules by a glycosidic bond. The polysaccharide used in the present invention is preferably cellulose, starch, Amylose, Amylopectin, Glycogen, Chitin, Agarose. Carrageenan, Heparin, Hyaluronic Acid, Pectin, Xyloglucan, and the like. [0028] The polysaccharide is added to the thermoelectric conversion layer forming composition of the present invention for the purpose of improving the dispersibility and coatability of the cobalt-based oxide. In the composition, the polysaccharide is present in a state of being dissolved or dispersed in water. [0029] Cellulose in polysaccharides, which is more well known, is a partially denatured derivative, such as carboxymethyl cellulose, hydroxyethyl cellulose, hydroxyethyl group. Cellulose, hydroxypropylcellulose, hydroxypropylmethylcellulose, methylcellulose, ethylcellulose, ethylhydroxyethylcellulose, carboxymethylethylcellulose, nitrocellulose, acetic acid Cellulose, etc. When forming the thermoelectric conversion layer, methyl cellulose, hydroxypropyl methyl cellulose, hydroxypropyl cellulose, and hydroxyethyl are preferred from the viewpoint of forming a thermoelectric conversion layer having good film formability and small volume resistivity. Methyl cellulose, hydroxyethyl cellulose, and more preferably hydroxypropyl methyl cellulose. [0030] The amount of the polysaccharide added is 0.02 to 10 parts by mass based on 100 parts by mass of the thermoelectric conversion layer-forming composition of the present invention. The more the polysaccharide is added, the better the adhesion between the cobalt-based oxide particles is, and the better the film formation property is. On the other hand, in order to obtain a thermoelectric conversion layer having good electrical conductivity, it is necessary to decompose the polysaccharide remaining in the thermoelectric conversion layer, and from this point of view, it is preferred that the polysaccharide is less. From the above reasons, the amount of the polysaccharide added is preferably from 0.04 to 5 parts by mass, particularly preferably from 0.1 to 2.5 parts by mass. The water contained in the thermoelectric conversion layer forming composition of the present invention has a function of dispersing a dispersion medium of a cobalt-based oxide. By containing water in the thermoelectric conversion layer forming composition, the cobalt-based oxide can be uniformly dispersed to form a uniform thermoelectric conversion layer. Further, in the present invention, water is used as a main dispersion medium from the viewpoint of environmental and work environment protection. Therefore, the total amount of (A) water and (B) cobalt-based oxide must be 90 parts by mass or more, and preferably 95 parts by mass or more, based on 100 parts by mass of the thermoelectric conversion layer-forming composition of the present invention. [0033] The composition for forming a thermoelectric conversion layer of the present invention can add a hydrophilic solvent within a range that does not pollute the environment and the working environment. The hydrophilic solvent may be added to water in advance to constitute a dispersion medium. The hydrophilic solvent is mainly added for the purpose of suppressing foaming and improving film formability. Specifically, methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, acetonitrile can be preferably used. [0034] The dispersion medium other than water is preferably 9.98 parts by mass or less, and particularly preferably 5 parts by mass, from the viewpoint of environmental and working environment protection, with respect to 100 parts by mass of the thermoelectric conversion layer-forming composition. the following. [0035] The composition for forming a thermoelectric conversion layer of the present invention, (B) a cobalt-based oxide and (C) a polysaccharide are present as a solid component. When the solid content concentration of the composition is too high, the composition does not have fluidity, and the thermoelectric conversion layer cannot be easily obtained by a coating method. On the other hand, when the solid content concentration is too low, the composition cannot obtain a uniform film. Therefore, the total of (B) the cobalt-based oxide and the (C) polysaccharide must be 1.02 to 60 parts by mass, preferably 10 to 30 parts by mass, particularly preferably 15 to 25, based on 100 parts by mass of the composition. Parts by mass. The preparation method of the thermoelectric conversion layer forming composition of the present invention is not particularly limited. Each of the raw materials may be added to the reaction container in an appropriate amount and mixed, and if necessary, wet-pulverized to obtain the thermoelectric conversion layer-forming composition of the present invention. In the preparation example, for example, water and a cellulose derivative may be added to a container and stirred until the cellulose derivative is completely dissolved. The cobalt-based oxide is then added to the same vessel. 1-propanol to suppress foaming may be added as needed. Then, in order to uniformly mix and disperse, a ball-milling treatment using zircon beads is carried out, whereby a composition for forming a thermoelectric conversion layer can be obtained. The conditions of the ball milling treatment are carried out, for example, on a mixing rotor (rotation number of the rotor: 100 rpm) for 5 days or in a sand mill (rotation number of 500 rpm) for 4 hours. The zircon beads are filtered using a sieve having a mesh size of 1 mm or less, whereby the composition can be easily removed. [0037] The thermoelectric conversion layer forming composition of the present invention can be formed by dropping the composition onto a substrate to form a film of the composition, and then drying the dispersion medium to form a thermoelectric conversion layer composed of a cobalt-based oxide. . However, in this state, since the polysaccharide is present between the particles of the cobalt-based oxide, the thermoelectric conversion layer having markedly deteriorated electrical conductivity is obtained. In order to obtain a thermoelectric conversion layer having good electrical conductivity, it is necessary to further calcine to the decomposition temperature of the polysaccharide. This firing is preferably at 300 ° C or higher in an oxidizing atmosphere. However, when the baking temperature is too high, the cobalt-based oxide having thermoelectric properties undergoes a phase change, so the upper limit of the firing temperature is limited by the phase transition temperature of the cobalt-based oxide. For example, when Ca ₃ Co ₄ O _{9 is} used as the cobalt-based oxide, the phase transition temperature is obtained at 860 ° C. Therefore, the firing temperature is preferably 850 ° C or lower. In addition, the upper limit of the firing temperature is also limited by the substrate used. For example, when a flexible substrate made of a resin is used, the firing temperature is preferably 450 ° C or lower. On the other hand, when a substrate having extremely high heat resistance, for example, a ceramic substrate such as alumina or a quartz substrate, is used, it can be fired at a temperature of 600 ° C or higher. [0038] In the firing step, in addition to heating and baking according to an oven or the like, photo-baking (photo-sintering) may be performed using light irradiation such as ultraviolet light, visible light, or flash. Further, it is also possible to use heat baking and light baking in combination. In the photo-baking, the film obtained by forming the composition for thermoelectric conversion layer formation may be baked at a temperature at which the polysaccharide can be decomposed. Examples of the light source for light irradiation include a mercury lamp, a metal halide lamp, a xenon lamp, a chemical lamp, a carbon arc lamp, and the like. For the light irradiation, for example, a high-illumination flash exposure such as a scanning exposure by an infrared laser, a xenon discharge lamp, or the like, an infrared lamp exposure, or the like can be preferably exemplified. For example, krypton pulsed light irradiation is mentioned. Since the light is irradiated to the surface of the film and heated in a short time, there is an advantage that the influence of heat on the substrate can be reduced. Further, since the light is fired, since it can be fired in a short time, it has the advantage of high productivity. The substrate is not particularly limited as long as it is an electrically insulating substrate, and a quartz substrate, a glass substrate, a ceramic substrate such as alumina, a resin substrate such as polyimide, or a metal having an insulating layer can be used. Substrate, etc. [0040] A drying device and a coating film drying and baking device can be generally used. Specific examples thereof include a spin coater, a slit coater, a knife coater, a roll coater, an inkjet, a dip coater, and screen printing. Examples of the apparatus used for drying and baking include a heating plate, an oven, a lamp heating device, and the like. Further, in addition to the heating device, the device used for firing may be a light irradiation device such as ultraviolet light, visible light, or glitter. EXAMPLES The present invention will be more specifically described by the following examples, but the present invention is not limited to the following description. In the examples, the apparatus and conditions used for the adjustment of the sample and the analysis of the physical properties are as follows. [Installation] (1) Electric furnace (sleeve furnace) Device: Yamada Electric Co., Ltd. tabletop furnace Y-2025-N (2) Rotary coating machine: Spin Coater 1H-D7 by Mikasa Co., Ltd. (3 ) Resistivity meter (measurement of surface resistance) Device: Loresta GP manufactured by Mitsubishi Chemical Corporation Co., Ltd. Probe: PSP Probe manufactured by Mitsubishi Chemical Corporation Co., Ltd. (distance between probes: 1.5 mm) (4) Scanning electron microscope device: Japan Electronics Co., Ltd. Co., Ltd. Electric Field Radiation Scanning Electron Microscope JSM-7400F (5) Film Thickness Measuring Device: Fine Shape Measuring Machine manufactured by Otaru Research Institute Co., Ltd. Surfcoder ET4000 (6) Wide-angle X-ray diffraction device: X-ray manufactured by Rigaku Co., Ltd. Diffraction device RINT Ultime+ Measurement conditions: X-ray source; Cu, voltage; 40kV, current; 40mA, STEP width; 0.04°, integrated time; 0.5sec/STEP, divergence slit; 1°, divergent longitudinal limit slit 10mm, Scattering slit 1°, photosensitive slit 0.3 mm (7) Thermoelectric characteristics evaluation device: Thermoelectric characteristics measuring device RZ2001i manufactured by Ozawa Science Co., Ltd. Electrode: Thin film electrode (8) Particle size analyzer device Nanotrac Microtrac Bel Co. Ltd. (registered trademark) UPA-EX (9) baking the optical apparatus: Xenon Corporation Canon Pulse light sintering apparatus S-2210 [0042] [feed] ‧ per-cobalt oxides: Ca ₃ Co ₄ O ₉ (Use: Ca ₃ Co ₄ O ₉ with a volume cumulative 50% of 0.46 μm when the volume particle size distribution was measured by Nanotrac UPA-EX manufactured by Microtrac Bel Co., Ltd.) ‧ HPMC-1: Hydroxypropyl methylcellulose (Metolose (registered trademark) 60SH-03 manufactured by Shin-Etsu Chemical Co., Ltd.) ‧HPMC-2: Hydroxypropylmethylcellulose (Metolose 60SH-15 manufactured by Shin-Etsu Chemical Co., Ltd.) ‧MC: Methylcellulose ( Meitolose MC manufactured by Shin-Etsu Chemical Co., Ltd. ‧HEC: Hydroxyethyl cellulose (HEC Daicel SE400 manufactured by Daicel FineChem Co., Ltd.) ‧PVA: Polyvinyl alcohol (AT-17 manufactured by Japan Vam & Poval Co., Ltd.) ‧PEG : Polyethylene Glycol (PEG #4000, manufactured by Nippon Oil Co., Ltd.) ‧ n-Propanol (manufactured by Junsei Chemical Co., Ltd.) [Example 1] HPMC-1 (0.05 g, 1 part by mass) was dissolved in Water (3.5 g, 74 parts by mass) was used as the polysaccharide. Ca ₃ Co ₄ O ₉ (1.0 g, 20 parts by mass) and n-propanol (0.25 g, 5 parts by mass) were added. Then, zircon beads having a diameter of 1 mm were added, and ball milling treatment was performed on a mixing rotor (100 rpm) for 5 days to obtain an example composition A. [Examples 2 to 4] The composition of Examples B to D was obtained by the same procedure as in Example 1 except that the composition of the third table was constituted. [Comparative Example 1] PVA (0.05 g, 1 part by mass) was dissolved in water (3.5 g, 74 parts by mass). Ca ₃ Co ₄ O ₉ (1.0 g, 20 parts by mass) and n-propanol (0.25 g, 5 parts by mass) were added. Then, zircon beads having a diameter of 1 mm were added, and ball milling treatment was performed on a mixing rotor (100 rpm) for 5 days to obtain a comparative example composition a. [Comparative Example 2] A comparative example composition of the composition of the fourth table was obtained by the same procedure as in Comparative Example 1, except that PEG (0.05 g, 1 part by mass) was used instead of PVA. . [Comparative Example 3] A comparative example composition c of the composition of the fourth table was obtained by the same procedure as in Comparative Example 1, except that PVA was not added. [Comparative Example 4] A comparative example composition having the composition of the fourth table was obtained by the same procedure as in Example 1 except that HPMC-1 (0.0005 g, 0.01 parts by mass) was used as the polysaccharide. d. [Comparative Example 5] A comparative example composition having the composition of the fourth table was obtained by the same procedure as in Example 1 except that HPMC-1 (0.0001 g, 0.002 parts by mass) was used as the polysaccharide. e. [Example 5] A small amount of the example composition A was dropped on an alkali-free glass substrate (25 mm × 25 mm), and a coating film was formed by a spin coating method (700 rpm). The obtained coating film was dried at 100 ° C for 5 minutes, and then fired at 600 ° C for 1 hour to obtain an example layer A1. In the example layer A1, even after drying at 100 ° C and after firing at 600 ° C, no cracking or peeling was observed, and it was confirmed that the layer A1 was uniformly coated on the glass substrate. Fig. 1 is a view showing the observation of the surface state and the cross-sectional state of the layer A1 of the example according to the scanning electron microscope (SEM). From the SEM observation, it was confirmed that in the example layer A1, the Ca ₃ Co ₄ O ₉ fine particles were laminated to form a 3.2 μm layer. [Example 6] A small amount of the example composition A was dropped on an alumina substrate (10 mm × 15 mm), and a coating film was formed by a spin coating method (700 rpm). The obtained coating film was dried at 100 ° C for 5 minutes, and then fired at 600 ° C for 1 hour to obtain an example layer A2. In the example layer A2, even after drying of the dispersion medium and after firing of the coating film, no cracking or peeling was observed, and it was confirmed that the layer A2 was uniformly coated on the alumina substrate. The measurement result of the wide-angle X-ray diffraction of the example layer A2 is shown in Fig. 2. In Fig. 2, (b) is a raw material powder, and (a) is a thermoelectric conversion layer composed of a cobalt-based oxide, which has a diffraction peak of a coating film and Ca ₃ Co ₄ O ₉ . [Example 7] The Sibeck coefficient of the example layer A2 formed on the alumina substrate obtained in Example 6 was applied to the layer A2 of the example layer heated to 100 ° C, 350 ° C or 600 ° C. A temperature difference of 0 to 5 ° C was generated in the plane, and the voltage generated at this time was measured and calculated. The Sibeck coefficient of Example Layer A2 heated to 100 ° C, 350 ° C or 600 ° C is shown in Table 2. In the example layer A2, it was confirmed that the thermoelectric conversion energy was excellent even in a medium-high temperature region of 600 °C. [Example 8] A small amount of the example composition A was dropped on an alkali-free glass substrate (25 mm × 25 mm), and a coating film was formed by a spin coating method (700 rpm). The obtained coating film was dried at 100 ° C for 5 minutes, and then fired at 600 ° C for 1 hour to obtain Example Layer A3. In the example layer A3, even after drying of the dispersion medium and after baking of the coating film, no cracking or peeling was observed, and it was confirmed that the layer A3 was uniformly coated on the glass substrate. Further, the film thickness of the example layer A3 was 4.4 μm, and the volume resistivity was 148 m Ω cm. The composition A3 of the embodiment shows that it is a composition which does not load the environment, and can form a uniform thermoelectric conversion layer having good characteristics. [Examples 9 to 13] The composition of Examples E to I was obtained by the same procedure as in Example 1 except that the composition was the same as that of the third table. [Examples 14 to 21] The example layers B1 to I1 were obtained by the same procedures as those in Example 8 except that the example compositions B to I were used. In the example layers B1 to I1, even after drying at 100 ° C and after firing at 600 ° C, no cracking or peeling was observed, and it was confirmed that the layers were uniformly coated on the glass substrate. The film thickness and conductivity of the examples B to D are shown in Table 5. The compositions B to D of the examples show that they are compositions which do not impose a load on the environment, and can form a uniform thermoelectric conversion layer having good characteristics. [Comparative Examples 6 to 10] In addition to the use of the comparative example compositions a to e, the comparison of the example layers a1 to e1 was attempted by the same procedure as in the example 5, but the comparative layers a1 to e1 were Cracking or peeling after drying at 100 ° C cannot form a thermoelectric conversion layer on the substrate. With respect to the comparative layers a1 and b1, it is considered that since PVA or PEG is not sufficiently dispersed with Ca ₃ Co ₄ O ₉ to cause aggregation, it is impossible to fix the Ca ₃ Co ₄ O ₉ particles on the substrate by the resin component. Cracking or peeling occurs after drying. Regarding the comparative example layers c1 to e1, it is considered that since a sufficient amount of the polysaccharide is not present, the components in which the particles or the particles are bonded to the substrate are insufficient, and cracking or peeling occurs after drying. It was confirmed that PVA or PEG was added instead of the composition of the polysaccharide (Comparative Example a, Comparative Example b), or the composition in which the amount of the polysaccharide was insufficient (Comparative Example c~e) It is impossible to function as a composition for forming a thermoelectric conversion layer. [Film Formability] The examples A to I and the comparative examples a to e prepared in Examples 1 to 4, 9 to 13, and Comparative Examples 1 to 5 were visually evaluated to be alkali-free. Film formation on glass. ○: No cracking or peeling of the thermoelectric conversion layer was observed. ×: Cracking or peeling of the thermoelectric conversion layer was observed. [Surface resistance value] For the sample to obtain the thermoelectric conversion layer, the surface resistance value at 3 points was measured using the Loresta GP, and The average value of the three points is set to the surface resistance value of the thermoelectric conversion layer. [Volume Resistivity] From the results of the surface resistance value and the film thickness measurement, the volume resistivity was calculated according to the following formula. Volume resistivity (mΩcm) = surface resistance value (Ω / □) × film thickness (μm) × 10 ^-1 [Example 22] HPMC-1 (1.5 g, 1 part by mass) was dissolved in water (118.5 g, 79 parts by mass) as a polysaccharide. Ca ₃ Co ₄ O ₉ (22.5 g, 15 parts by mass) and n-propanol (7.5 g, 5 parts by mass) were added. Then, zircon beads of φ 1 mm were added, and ball milling treatment was carried out for 4 hours using a sand mill (500 rpm) to obtain an example composition J. [Example 23] A small amount of Example Composition J was dropped on an alkali-free glass substrate (25 mm × 25 mm), and a coating film was formed by a spin coating method (700 rpm). The obtained coating film was dried at 100 ° C for 5 minutes, and then fired at 600 ° C for 1 hour to obtain an example layer J1. In the example layer J1, even after drying at 100 ° C and after firing at 600 ° C, no cracking or peeling was observed, and it was confirmed that it was uniformly coated on the glass substrate. The film formability, surface resistance value and volume resistivity of Example Layer J1 are shown in Table 7. [Example 24] A small amount of the example composition J was dropped on an alkali-free glass substrate (25 mm × 25 mm), and a coating film was formed by a spin coating method (700 rpm). The obtained coating film was dried at 100 ° C for 5 minutes, and then fired at 350 ° C for 1 hour to obtain an example layer J2. The film formability, surface resistance value and volume resistivity of Example Layer J2 are shown in Table 7. [0059] [Example 25] A small amount of the example composition J was dropped on an alumina substrate (15 mm × 15 mm), and a coating film was formed by a spin coating method (700 rpm). The obtained coating film was dried at 100 ° C for 5 minutes, and then fired at 600 ° C for 1 hour to obtain an example layer J3. [Example 26] A small amount of Example Composition J was dropped on an alumina substrate (15 mm × 15 mm), and a coating film was formed by a spin coating method (700 rpm). The obtained coating film was dried at 100 ° C for 5 minutes, and then fired at 350 ° C for 1 hour to obtain an example layer J4. [Example 27] The Sibeck coefficient of the example layer J3 formed on the alumina substrate was caused to have a temperature difference of 0 to 5 ° C in the plane of the example layer J3 heated to 100 ° C, 350 ° C or 600 ° C. And calculate the voltage generated at this time and calculate it. The Sibeck coefficient of the embodiment layer J3 is as shown in the eighth table. In the example layer J3, since it has a Schiebeck coefficient of 50 μV/K or more, it was confirmed that it has thermoelectric conversion energy. With respect to the example layer J4, the Sibeck coefficient of the example layer heated to 100 ° C and 350 ° C was also calculated by the same method. The Sibeck coefficient of the embodiment layer J4 is as shown in the eighth table. In the example layer J4, since the Schiebeck coefficient of 50 μV/K or more was also obtained, it was confirmed that the thermoelectric conversion energy was obtained. [Example 28] The composition of Example A was dropped on an alkali-free glass substrate (25 mm × 25 mm), and a coating film was formed by a spin coating method (700 rpm). The obtained coating film was dried at 100 ° C for 5 minutes, and then fired at 350 ° C for 1 hour. Finally, the coating film was subjected to photo sintering (voltage: 3000 V, 300 μsec) to obtain Example Layer A4. The film thickness of the example layer A4 was 0.8 μm, and the volume resistivity was 3.1 × 10 ² m Ω cm.

[0011] Fig. 1 is an observation image of the surface shape and the cross-sectional shape of the thermoelectric conversion layer A1 taken by a scanning electron microscope. Fig. 2(a) is an X-ray diffraction pattern of the embodiment layer A2 on the alumina substrate [□ is a diffraction peak of the alumina substrate], and Fig. 2(b) is a Ca ₃ Co ₄ O used as a raw material. ₉ X-ray diffraction pattern of powder [Ca ₃ Co ₄ O ₉ , denoted as Co349 in Figure 2].

Claims (7)

A composition for forming a thermoelectric conversion layer, which comprises a composition for forming a thermoelectric conversion layer of (A) water, (B) a cobalt-based oxide, and (C) a polysaccharide, and is 100 parts by mass based on the composition ( The total of A) and (B) is 90 to 99.98 parts by mass, (B) is 1 to 50 parts by mass, and (C) is 0.02 to 10 parts by mass. The thermoelectric conversion layer forming composition according to claim 1, wherein the (C) polysaccharide is a cellulose derivative. The thermoelectric conversion layer forming composition according to claim 2, wherein the cellulose derivative is hydroxypropylmethylcellulose. The thermoelectric conversion layer forming composition according to any one of claims 1 to 3, wherein the (B) cobalt-based oxide is represented by the following general formula (1): (wherein A ¹ is a group selected from the group consisting of Na, K, Li, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Pb, Sr, Ba, Al, Bi, Y, and lanthanum elements. At least one element of the group, A ² is at least one element selected from the group consisting of Ti, V, Cr, Mn, Fe, Ni, Cu, Ag, Mo, W, Nb, and Ta, 2.2≦a1≦3.6; 0≦b1≦0.8;2.0≦c1≦4.5;0≦d1≦2.0;8≦e1≦10), or with the following general formula (2): (wherein A ¹ is a group selected from the group consisting of Na, K, Li, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Pb, Sr, Ba, Al, Bi, Y, and lanthanum elements. a group of at least one element, A ² being at least one element selected from the group consisting of Ti, V, Cr, Mn, Fe, Ni, Cu, Ag, Mo, W, Nb, and Ta, 0 < a2 ≦ 2; 0≦b2≦0.6;0<c2≦2;0≦d2≦0.6;1.0≦e2≦3.0), or is the general formula (3) below: (wherein M ¹ is Sr or Pb, and A ¹ is selected from the group consisting of Na, K, Li, Ti, V, Cr, Mn, Fe, Ni, Cu, Zn, Pb, Sr, Ba, Al, Bi, Y and At least one element of the group consisting of lanthanum elements, A ² being at least one element selected from the group consisting of Ti, V, Cr, Mn, Fe, Ni, Cu, Ag, Mo, W, Nb, and Ta , 1.8≦a3≦2.2; 0≦f3≦0.4; 1.8≦b3≦2.2; 1.6≦c3≦2.2; 0≦d3≦0.5; 8≦e3≦10) the compound represented. A method of producing a thermoelectric conversion layer, comprising: a step of applying a composition for forming a thermoelectric conversion layer according to any one of claims 1 to 4 to a substrate to form a film; and then removing the polysaccharide from the film And the step of firing the film in an oxidizing atmosphere of 300 ° C or higher. A method of producing a thermoelectric conversion layer, comprising: a step of applying a composition for forming a thermoelectric conversion layer according to any one of claims 1 to 4 to a substrate to form a film; and then removing the polysaccharide from the film And the step of photo-firing the film by light irradiation in an oxidizing environment. A method of producing a thermoelectric conversion layer, comprising: a step of applying a composition for forming a thermoelectric conversion layer according to any one of claims 1 to 4 to a substrate to form a film; and removing a polysaccharide from the film And the step of firing the film in an oxidizing atmosphere of 300 ° C or higher; and then photo-firing the film by light irradiation in an oxidizing atmosphere.