JP2006128444A - Thermoelectric material - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermoelectric material which is light-weight and does not necessarily contain rare elements and toxic elements, has a relatively high thermoelectric characteristic and has little deterioration in the thermoelectric characteristic with the passage of time. <P>SOLUTION: A first thermoelectric material is composed of a complex material which contains a carrier, an organic compound having electric conductivity and a thermoelectric characteristic which is carried on the surface of the carrier, and a dopant carried on the interface between the carrier and the organic compound. The first complex material has an output factor (S<SP>2</SP>σ) of 10<SP>-7</SP>Wm<SP>-1</SP>K<SP>-2</SP>or above. A second thermoelectric material is composed of a complex material which contains a porous carrier and an organic compound having electric conductivity and a thermoelectric characteristic which is carried in the pore of the carrier. The second complex material has an output factor (S<SP>2</SP>σ) of 10<SP>-7</SP>Wm<SP>-1</SP>K<SP>-2</SP>or above. In the second case, it is preferred that the complex material further contains a dopant carried on the interface between the organic matter and the inner wall surfaces of the pores. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a thermoelectric material, and more particularly to a thermoelectric material constituting a thermoelectric element used for thermoelectric power generation and thermoelectric heating / cooling.

  Thermoelectric conversion refers to the direct conversion of electrical energy into thermal energy for cooling and heating, and conversely, thermal energy into electrical energy using the Seebeck effect and Peltier effect. Thermoelectric conversion (1) No excess waste is discharged during energy conversion, (2) Effective use of exhaust heat is possible, (3) Power can be generated continuously until the material deteriorates (4) Since a movable device such as a motor or a turbine is unnecessary and maintenance is not required, it has been attracting attention as a high-efficiency energy utilization technology.

As an index for evaluating the characteristics of heat energy and electric energy, that is, the characteristics of the thermoelectric material, generally, the figure of merit Z (= S ² σ / κ, where S: Seebeck coefficient, σ: electric conduction Degree, κ: thermal conductivity), or a dimensionless figure of merit ZT expressed as a product of the figure of merit Z and the absolute temperature T indicating the value. The Seebeck coefficient represents the magnitude of electromotive force generated by a temperature difference of 1K. Thermoelectric materials each have their own Seebeck coefficient, and are broadly classified into those having a positive Seebeck coefficient (p-type) and those having a negative Seebeck coefficient (n-type).

The thermoelectric material is usually used in a state where a p-type thermoelectric material and an n-type thermoelectric material are joined. Such a junction pair is generally called a “thermoelectric element”. The performance index of the thermoelectric element depends on the performance index Z _{p of the p-} type thermoelectric material, the performance index Z _{n of} the n-type thermoelectric material, and the shape of the p-type and n-type thermoelectric materials, and the shape is optimized If you are the greater the Z _p and / or Z _n, the figure of merit of the thermoelectric element increases is known. Therefore, in order to obtain a high figure of merit thermoelectric device, the figure of merit Z _p, be used with high Z _n thermoelectric material is important.

Examples of such thermoelectric materials include compound semiconductors such as Bi—Te, Pb—Te, and Si—Ge, Na _x CoO ₂ (0.3 ≦ x ≦ 0.8), (ZnO) _m In ₂ O. ₃ (1 ≦ m ≦ 19), Ca ₃ Co ₄ O _{9 and} other oxide ceramics are known. These materials are generally p-type thermoelectric materials that are processed into columns (hereinafter referred to as “bulk thermoelectric materials”) and n-type bulk thermoelectric materials. It is used in the state of an element (so-called “π-type element”) or a thermoelectric element (so-called “U-type element”) in which one end of a p-type and n-type bulk thermoelectric material is directly joined.

However, the conventional thermoelectric material has a problem that it is difficult to process. In addition, rare elements and toxic elements may be included, which may cause problems in manufacturing cost and environment.
It is also known that the Seebeck coefficient S, electrical conductivity σ, and thermal conductivity κ that determine the figure of merit Z of the thermoelectric material are all functions of the carrier concentration. Therefore, there is a limit to the figure of merit Z that can be reached simply by adjusting the carrier concentration in the thermoelectric material.

  In order to solve this problem, various proposals have heretofore been made. For example, Patent Document 1 discloses a hybrid thermoelectric material including a thermoelectric material such as calcium cobalt oxide and a polymer-coated carbon nanotube, a polymer-coated carbon fiber, or a conductive polymer. This document describes that the thermal conductivity can be lowered without lowering the electrical conductivity by adding a polymer-coated carbon nanotube or the like to the thermoelectric material.

  In Patent Document 2, poly (2-butoxy-5-methoxy-1,4-phenylenevinylene), which is a kind of conductive polymer, is dissolved in chloroform, and this solution is dropped on a slide glass and cast. A thermoelectric material obtained by forming a film, drying the film, and further vapor-doping iodine into the film is disclosed. In this document, the performance index Z can be improved by doping polyphenylene vinylene and adjusting the electric conductivity σ to a predetermined range, and by replacing a part of the phenylene group with an alkoxy group. It describes that easy processability can be imparted and that the durability can be improved by sealing the surface of the conductive polymer with an epoxy resin or the like.

JP 2002-245592 A JP 2003-332639 A

  Conventional thermoelectric materials (particularly, Bi—Te and Pb—Te compound semiconductors) have a relatively large specific gravity. Therefore, when a large number of thermoelectric elements using such a thermoelectric material are mounted on a moving body, there is a problem that energy efficiency is lowered. Further, since the conventional thermoelectric material is hard and brittle, there is a problem that the thermoelectric material is easily damaged or the electrode is poorly bonded due to vibration or thermal stress.

  On the other hand, some organic compounds are known to exhibit electrical conductivity (for example, conductive polymers) and are used for antistatic, electromagnetic shielding materials, and the like. In addition, it is known that certain types of conductive polymers exhibit not only electrical conductivity but relatively large thermoelectric properties. Moreover, the conductive polymer is characterized by being lighter than conventional thermoelectric materials and not necessarily containing rare elements and toxic elements. Furthermore, the conductive polymer is more flexible than conventional thermoelectric materials and is easy to process.

On the other hand, since a conductive polymer usually has a low electric conductivity σ as it is, doping is generally performed to increase the electric conductivity σ. Doping is generally performed by adding a dopant from the surface of the conductive polymer via the gas phase or liquid phase. However, when the added dopant volatilizes from the surface of the conductive polymer during use, there is a problem in that the electrical conductivity σ is lowered, thereby reducing the thermoelectric characteristics.
In order to solve this problem, as described in Patent Document 2, it is conceivable to seal the surface of the conductive polymer with an appropriate material. However, the sealing causes an increase in the manufacturing cost of the thermoelectric element, or the sealing may be difficult depending on the shape of the thermoelectric element.

  Furthermore, since the conductive polymer exhibits conductivity when the carrier moves along the polymer chain, in order to obtain a high electric conductivity σ, the polymer chain is oriented in one direction to obtain a high electric conductivity σ. It is preferable to improve mobility. However, in the method of applying a solution containing a conductive polymer to the surface of the glass substrate, it is difficult to orient the polymer chain in one direction.

  The problem to be solved by the present invention is to provide a thermoelectric material that is lightweight and does not necessarily contain rare elements or toxic elements. Another problem to be solved by the present invention is to provide a thermoelectric material having relatively high thermoelectric characteristics and little deterioration of the thermoelectric characteristics over time.

In order to solve the above problems, the first of the thermoelectric materials according to the present invention is a carrier, an organic compound having electrical conductivity and thermoelectric properties carried on the surface of the carrier, and an interface between the carrier and the organic compound. It is a composite comprising a supported dopant, and the summary is that the output factor (S ² σ) of the composite is 10 ⁻⁷ Wm ⁻¹ K ⁻² or more.

The second thermoelectric material according to the present invention comprises a composite comprising a porous carrier and an organic compound having electrical conductivity and thermoelectric properties carried in the pores of the carrier. The gist is that the output factor (S ² σ) of the body is 10 ⁻⁷ Wm ⁻¹ K ⁻² or more. In this case, it is preferable to further include a dopant supported on the interface between the organic substance and the inner wall surface of the pore.

  Since the thermoelectric material according to the present invention is composed of a composite of an organic compound having electrical conductivity and thermoelectric properties and a carrier, it is lighter than conventional thermoelectric materials and does not necessarily contain rare elements or toxic elements. Absent. In addition, in the case of adding a dopant for increasing the conductivity of the organic compound, when the dopant is supported on the interface between the organic compound and the carrier, it is possible to suppress deterioration over time of thermoelectric characteristics due to volatilization of the dopant. Furthermore, when a conductive organic compound is supported in the pores of a porous carrier, the polymer chains are easily oriented in one direction in the pores, and the thermoelectric properties in the orientation direction are improved.

  Hereinafter, an embodiment of the present invention will be described in detail. The thermoelectric material according to the first embodiment of the present invention is composed of a composite including a carrier, an organic compound, and a dopant.

The carrier is for supporting an organic compound on its surface. In the present embodiment, a dense carrier is used. The shape of the carrier is not particularly limited, and various shapes such as a plate shape, a sheet shape, and a cylindrical shape can be taken according to the purpose. When the carrier is plate-shaped or sheet-shaped, the thermoelectric material may be composed of one plate-shaped or sheet-shaped carrier and one layer of organic compound supported on the surface of the carrier, or two sheets. It may be provided with the above plate-like or sheet-like carrier and one or more organic compounds supported between the carriers.
Further, the carrier may be in powder form. Even if an organic compound is supported on the surface of a powdery carrier, it can be compacted or combined with another appropriate material (for example, polymer, rubber, etc.) A thermoelectric element having a predetermined shape can be configured.

The material of the carrier is not particularly limited, and may be any of a conductor, a semiconductor, and an insulator. In general, the figure of merit Z of the thermoelectric material is inversely proportional to the thermal conductivity κ, so that the carrier preferably has a relatively low thermal conductivity in order to obtain a thermoelectric element having high thermoelectric characteristics.
In order to obtain a thermoelectric element having high thermoelectric characteristics, specifically, the thermal conductivity of the carrier is preferably 20 Wm ⁻¹ K ⁻¹ or less, more preferably 5 Wm ⁻¹ K ⁻¹ or less.

Examples of carriers that satisfy such conditions include inorganic materials such as SiO ₂ and TiO ₂ .

An organic compound consists of what has electrical conductivity and a thermoelectric characteristic, and is carry | supported by the surface of a support | carrier. Such organic compounds include the following.
A first specific example of the organic compound is a conductive polymer. Since the conductive polymer is lightweight and does not necessarily contain a rare element and / or a toxic element, it is particularly suitable as an organic compound constituting the thermoelectric material according to the present invention. Specific examples of the conductive polymer include polyacetylene, polyacene, polyvinylene, polypyrrole, polyaniline, polythiophene, and polyquinoline.

These conductive polymers may have various substituents bonded to the main chain skeleton. When various substituents are bonded to the main chain skeleton, various functions can be imparted to the conductive polymer.
For example, introduction of an alkoxy group into the main chain skeleton can impart solvent solubility and heat moldability to the conductive polymer. In this case, 1-20 are preferable and, as for carbon number of an alkoxy group, More preferably, it is 1-10. Further, the alkoxy group may be linear, branched or alicyclic. Furthermore, other substituents may be bonded to the alkoxy group.
For example, when a sulfone group or an alkyl group is added to the main chain, the carrier concentration of the conductive polymer can be changed. Further, the terminal of the added side chain may be substituted with a sulfone group or the like.

A second specific example of the organic compound is an organic charge transfer complex. The “organic charge transfer complex” is an organic solid, and is a complex (D ^{γ +} A ^γ− ) generated by charge transfer between an electron donor (donor, D) and an electron acceptor (acceptor, A). γ represents the amount of charge transfer). Although not all organic charge transfer complexes have electrical conductivity and thermoelectric properties, certain organic charge transfer complexes have relatively high electrical conductivity and thermoelectric properties.
Specific examples of such an organic charge transfer complex include p-phenylenediamine / tetracyanoquinodimethane and tetrathiafulvalene / tetracyanoquinodimethane.

The dopant is added to increase the electrical conductivity σ of the organic compound. In the present embodiment, at least a part of the dopant is supported on the interface between the organic compound and the carrier. The dopant may be supported only on the interface, or may be supported on the surface or inside of the organic compound in addition to the interface. When the dopant is supported on the interface, the dopant may be supported on the entire surface of the interface, or may be supported only on a necessary part of the interface.
The dopant may be physically supported on the interface, or may be fixed by a chemical bond. In particular, when the dopant is fixed by a chemical bond, volatilization of the dopant is suppressed, so that a thermoelectric material with little deterioration with time is obtained.
Furthermore, the addition amount of a dopant is not specifically limited, The optimal amount is selected according to the kind etc. of a dopant and an organic compound, the characteristic requested | required of a thermoelectric material.

The dopant includes an acceptor dopant (p-type dopant) that receives electrons from an organic compound and a donor dopant (n-type dopant) that supplies electrons to the organic compound.
Specifically, as an acceptor dopant to be added to the conductive polymer,
(1) Halogen such as Cl ₂ , Br ₂ , I ₂ , ICl, ICl ₃ , IBr, IF,
(2) Lewis acids such as PF ₅ , AsF ₅ , SbF ₅ , BF ₃ , BCl ₃ , BBr ₃ , SO ₃ ,
(3) HF, HCl, HNO ₃ , H ₂ SO ₄ , HClO ₄ , protonic acid such as phosphoric acid,
(4) Organic acids such as 2-naphthalenesulfonic acid, dodecylbenzenesulfonic acid, camphorsulfonic acid,
(5) Transition metal compounds such as FeCl ₃ , FeOCl, TiCl ₄ , ZrCl ₄ , HFCl ₄ , NbF ₅ , NbCl ₅ , TaCl ₅ , MoF ₅ , and WF ₆ .
Moreover, as a donor dopant, specifically,
(1) Alkali metals such as Li, Na, K, Rb, Cs,
(2) Alkaline earth metals such as Ca, Sr, Ba,
(3) Lanthanoids such as Eu,
(4) R ₄ N ⁺ , R ₄ P ⁺ , R ₄ As ⁺ , R ₃ S ⁺ (R: alkyl group), acetylcholine,
and so on.

  In the case of an organic charge transfer complex, the electrical conductivity σ may increase by adding a halogen or introducing a substituent to the complex.

Furthermore, the thermoelectric material according to the present embodiment is composed of the composite as described above, and the output factor (S ² σ) of the composite is 10 ⁻⁷ Wm ⁻¹ K ⁻² or more. To do. In order to obtain a thermoelectric element having high thermoelectric characteristics, the output factor (S ² σ) of the organic compound at the use temperature is preferably 10 ⁻⁵ Wm ⁻¹ K ⁻² or more, more preferably 10 ⁻⁴ Wm ^{−. 1} K ^-2 or more. The output factor (S ² σ) can be adjusted by optimizing the kind of organic compound and dopant, the amount of these supported on the carrier, and the like.

  Next, a method for manufacturing a thermoelectric element according to the present embodiment will be described. First, an organic compound is synthesized using a known method. For example, the conductive polymer can be obtained by polymerizing a monomer having a conjugated double bond, a monomer composed of an aromatic compound, or the like by an electric field polymerization method, a chemical oxidation polymerization method, or the like. The organic charge transfer complex is obtained by evaporating a solvent from a solution in which both D and A are dissolved under predetermined conditions to form a complex.

Next, the dopant is supported on the surface of the carrier having an appropriate shape. As a method for supporting the dopant on the surface of the carrier, specifically,
(1) (a) An OH group is introduced on the surface of the carrier (for example, when the second component is an inorganic material, the second component is treated with a carros solution (H ₂ O ₂ : H ₂ SO ₄ = 1: 4). And)
(B) By causing a condensation reaction between the OH group on the support surface and an alkoxyl group of an alkylalkoxysilane (for example, 3-mercaptopropyltrimethoxysilane), the alkylalkoxysilane is chemically bonded to the support surface;
(C) a method of introducing a dopant into a terminal alkyl group (for example, sulfonation using sulfuric acid or the like),
(2) A method of coating, spraying or spraying a solution containing a dopant on the surface of a carrier to volatilize the solvent,
and so on.

Next, an organic compound is further supported on the surface of the carrier on which the dopant is supported. The method for supporting the organic compound is not particularly limited, and various methods can be used depending on the type of the organic compound.
For example, when the organic compound is a conductive polymer such as polyaniline, the conductive polymer is dissolved in an appropriate solvent (for example, 1-methyl-2-pyrrolidone, chloroform, etc.), and this solution is applied to the surface of the carrier. There are methods such as spraying and volatilizing the solvent.
Further, for example, when the organic compound is an organic charge transfer complex such as tetrathiafulvalene or tetracyanoquinodimethane, there is a method of evaporating and drying a solvent from a solution such as chlorobenzene containing a complex raw material.

  In addition, after making an organic compound carry | support on the support | carrier surface, you may add a dopant through a gaseous phase or a liquid phase further. In addition, a composite composed of two or more plate-shaped or sheet-shaped carriers and an organic compound supported between the carriers is used to support the dopant on the surface of the plate-shaped or sheet-shaped carriers using the various methods described above. Then, an organic compound is supported on the surface of the carrier and obtained by superimposing them.

  Next, the operation of the thermoelectric material according to the present embodiment will be described. Certain organic compounds have electrical conductivity and thermoelectric properties, are relatively lightweight, and do not necessarily contain rare and toxic elements. Therefore, if this is applied to, for example, energy conversion of a mobile body (for example, an automobile), it is considered that energy conversion efficiency can be improved without increasing the load on the environment.

However, in order to obtain high thermoelectric characteristics in this type of organic compound, it is generally necessary to add a dopant for improving the electrical conductivity σ. Conventionally, the dopant has been added from the surface of the organic compound via the gas phase or the liquid phase, so that the dopant volatilizes during use, and the electrical conductivity σ tends to deteriorate over time.
On the other hand, when at least a part of the dopant is fixed to the interface between the organic compound and the carrier that supports the organic compound, volatilization of the dopant can be suppressed, and deterioration of the thermoelectric characteristics over time can be suppressed. In particular, when the dopant is fixed to the surface of the support by chemical bonding, it is possible to further suppress the deterioration with time of the thermoelectric characteristics due to the volatilization of the dopant.

  Next, a thermoelectric element according to the second embodiment of the present invention will be described. The thermoelectric material according to the present embodiment is composed of a composite including a carrier and an organic compound. Among these, the organic compound is the same as that in the first embodiment, and thus the description thereof is omitted.

  In the present embodiment, the carrier is made of a porous body, and at least a part of the organic compound is supported in the pores. That is, the organic compound may be supported only in the pores, or may be supported on the surface of the carrier in addition to the pores. Further, the pores in the carrier need to be continuous from one end for taking out current or applying current to the other end. In particular, when a porous body having one-dimensional pores in which pores are connected from one end portion to the other end portion is used as a support, a composite having high thermoelectric characteristics can be obtained.

The volume fraction of the pores contained in the carrier is not particularly limited, and can be arbitrarily selected according to the organic compound, the material of the carrier, the use of the thermoelectric material, and the like. In general, the larger the volume fraction of the pores in the carrier, the more organic substances can be carried in the pores.
Similarly, the pore diameter of the pores contained in the carrier is not particularly limited and can be arbitrarily selected according to the purpose. In general, the larger the pore diameter, the easier the organic compound is supported in the pores. In the case where a porous body having one-dimensional pores is used as a carrier, if the pore diameter is optimized, the organic compound can be oriented along the longitudinal direction of the pores. can get.

Specifically, as a carrier,
(1) A porous body made of an inorganic material such as zeolite, mesoporous silica, TiO ₂ , ZrO ₂ , Al ₂ O ₃ , SnO ₂ , AlPO ₄ ,
(2) Mesoporous silica in which ethylene groups or phenyl groups are uniformly dispersed in the pore walls,
and so on.
Among these, mesoporous silica is particularly suitable as a carrier for supporting an organic compound because mesopores can be aligned in one direction by optimizing the synthesis conditions.

  When the organic compound is supported in the pores of the carrier, the organic compound may be directly supported in the pores, or the dopant may be supported on the interface between the organic compound and the inner wall surface of the pores. good. When the dopant is supported on the interface, the dopant may be physically supported on the inner wall surface of the pore, or may be fixed to the inner wall surface of the pore by a chemical bond. Since other points regarding the dopant are the same as those in the first embodiment, description thereof will be omitted.

Furthermore, the thermoelectric material according to the present embodiment is composed of the composite as described above, and the output factor (S ² σ) of the composite is 10 ⁻⁷ Wm ⁻¹ K ⁻² or more. To do. In order to obtain a thermoelectric element having high thermoelectric characteristics, the output factor (S ² σ) of the organic compound at the use temperature is preferably 10 ⁻⁵ Wm ⁻¹ K ⁻² or more, more preferably 10 ⁻⁴ Wm ^{−. 1} K ^-2 or more. The output factor (S ² σ) can be adjusted by optimizing the types of organic compound and dopant and the amount of these supported on the carrier.

Next, a method for manufacturing a thermoelectric element according to the present embodiment will be described.
First, a porous carrier is prepared. For example, when zeolite is used as the carrier, commercially available zeolite powder is used as it is, or it is molded into a predetermined shape such as a plate, sheet, or cylinder, and compacted to obtain a carrier.
In addition, for example, mesoporous silica is a silica raw material (for example, silane compound such as tetraalkoxysilane, silicic acid such as sodium metasilicate (Na ₂ SiO ₃ ), using a surfactant (for example, hexadodecyltrimethylammonium chloride) as a template. It can be obtained by three-dimensionally polymerizing sodium, kanemite (a layered silicate such as NaHSi ₂ O ₅ .3H ₂ O). In particular,
(1) Add appropriate amount of surfactant and silica raw material (and other raw materials if necessary) to water, and hydrolyze silica raw material (and other raw materials added as needed) under basic conditions Let
(2) separating the product from the solution and removing the surfactant;
Is obtained.
At this time, by optimizing the concentration of the surfactant in the solution, the concentration of the silica raw material, and the ratio of both, mesoporous silica in which mesopores are regularly arranged can be obtained. Moreover, powdery or sheet-like mesoporous silica can be obtained by optimizing the synthesis conditions.

  Next, when an organic compound synthesized using a commercially available or known method is supported in the pores of the support, the thermoelectric material according to the present embodiment is obtained. The method for supporting the organic compound in the pores is not particularly limited, but a method of dissolving the organic compound in an appropriate solvent, immersing the carrier in this solution, and removing the solvent is suitable.

Moreover, the thermoelectric material containing the dopant is specifically,
(1) The various dopant fixing methods described in the first embodiment are applied to the porous body as they are to allow the dopant to be supported on the inner wall surface of the pore, and then the inside of the pore in which the dopant is supported on the inner wall surface. A method of further supporting an organic compound,
(2) First, an organic compound is supported in the pores, and then a dopant is introduced into the pores through a gas phase or a liquid phase,
(3) A method in which a dopant is further added to a solution in which an organic compound is dissolved in an appropriate solvent, the carrier is immersed in a solution containing the organic compound and the dopant, and the solvent is removed.
Etc. When such a method is used, a thermoelectric material in which at least a part of the dopant is supported on the interface between the pore inner wall surface and the organic compound can be obtained.

Since the thermoelectric material according to the present embodiment includes an organic compound having thermoelectric properties, the thermoelectric material is lighter than conventional thermoelectric materials and does not necessarily include a rare element or a toxic element. Further, since the organic compound is supported in the pores of the carrier, the thermoelectric characteristics in the orientation direction are improved particularly when the pores are oriented in one direction.
Furthermore, when at least a part of the dopant is fixed to the interface between the inner wall surface of the pore and the organic compound supported in the pore, volatilization of the dopant can be suppressed and deterioration with time of the thermoelectric characteristics can be suppressed. In particular, when the dopant is fixed to the inner wall surface of the pore by a chemical bond, it is possible to further suppress deterioration with time of thermoelectric characteristics due to the volatilization of the dopant.

(Comparative Example 1)
A solution (basic polyaniline concentration: 10 wt%) in which basic polyaniline was dissolved in 1-methyl-2-pyrrolidone was prepared. This solution was cast on a SiO ₂ substrate by a spin coating method to form a basic polyaniline thin film (thickness: 5000 mm (500 nm)). Furthermore, the obtained thin film was dried at room temperature in a nitrogen stream for 24 hours. Thereafter, the thin film was immersed in a sulfuric acid solution and subjected to liquid phase doping.

Example 1
The SiO ₂ substrate was immersed in a carros solution (H ₂ O ₂ : H ₂ SO ₄ = 1: 4 solution) for 1 hour to introduce OH groups on the surface of the SiO ₂ substrate. Thereafter, it was thoroughly washed with pure water. Next, in order to remove moisture on the substrate surface, the substrate was immersed in ethanol for 10 minutes, then immersed in an ethanol + toluene (1: 1) solution for 10 minutes, and further immersed in toluene for 10 minutes.
Next, the substrate was immersed in a toluene solution (concentration 5 wt%) of 3-mercaptopropyltrimethoxysilane for 24 hours. Next, the substrate was washed with a 60 ° C. toluene solution, further thoroughly washed with pure water, and finally dried with a dryer (50 ° C.). By this operation, 3-mercaptopropyltrimethoxysilane was fixed to the substrate surface by chemical bonding.
Next, the substrate was immersed in a sulfuric acid solution for 15 minutes, then thoroughly washed with pure water and dried with a dryer (50 ° C.). By this treatment, the terminal of 3-mercaptopropyltrimethoxysilane was sulfonated. That is, an SiO ₂ substrate having a sulfone group chemically fixed on the surface was obtained.
The basic polyaniline solution prepared in Comparative Example 1 was cast on the surface of the substrate using a spin coating method to form a polyaniline thin film (thickness: 5000 mm (500 nm)).

  For the thermoelectric materials obtained in Comparative Example 1 and Example 1, the electrical conductivity σ, which is an important factor of thermoelectric characteristics, was measured by a four-terminal method. Further, the obtained thin film was exposed to an air stream at room temperature, and the change with time in electrical conductivity σ was measured. Table 1 shows the results. In Table 1, the electric conductivity σ immediately after the film formation was set to 100, and the electric conductivity σ after a certain time elapsed was expressed as a relative value with respect to the value immediately after the film formation.

  In Comparative Example 1, a significant decrease in electrical conductivity σ considered to be caused by dopant volatilization was observed. On the other hand, in Example 1, the electrical conductivity σ did not change greatly. This is presumably because the sulfone group fixed on the substrate acts as a dopant and does not volatilize, so that the electrical conductivity σ did not decrease. In addition, the slight decrease in electrical conductivity σ in Example 1 may be attributed to the volatilization of the solvent remaining in the thin film. That is, it is presumed that the electrical conductivity σ has changed due to the shrinkage of the polymer film due to the volatilization of the solvent.

(Example 2)
[1. Production of porous body]
50 g of kanemite (NaHSi ₂ O ₅ .3H ₂ O) calcined at 700 ° C. was dispersed in a 0.1 mol / dm ³ aqueous solution of hexadodecyltrimethylammonium chloride. This solution was stirred at 70 ° C. for 3 h. After the solution was cooled to room temperature, HCl solution was added to adjust the pH of the aqueous solution to 8.5. Then, it filtered and washed with water, and obtained powder was dried in air | atmosphere. Further, the obtained powder was fired at 700 ° C. for 6 hours. From the XRD measurement and nitrogen adsorption measurement, it was found that the obtained powder was mesoporous silica having a pore diameter of about 2.7 nm and a specific surface area of about 800 m ² / g.

[2. Sulfonation of pore surface]
1.2 g of mesoporous silica was immersed in a chloroform solution (concentration: 2 wt%) of 3-mercaptopropyltrimethoxysilane and stirred at room temperature for 24 hours. Then, it filtered and the powder was fully washed with water. Next, mesoporous silica was immersed in a sulfuric acid solution for 15 minutes, washed thoroughly with pure water, and dried with a dryer (50 ° C.). By the above operation, the terminal of 3-mercaptopropyltrimethoxysilane added to the pore surface of mesoporous silica was sulfonated.

[3. Introduction of conductive polymer]
Sulfonated mesoporous silica was immersed in a 1-methyl-2-pyrrolidone solution of basic polyaniline (concentration 2 wt%) and stirred for 24 hours under reduced pressure. Then, it dried under reduced pressure at 50 degreeC for 48 hours, and removed excess 1-methyl-2-pyrrolidone. By this treatment, basic polyaniline was supported in the pores.

(Comparative Example 2)
[1. ] In the mesoporous silica prepared in [3. ] Basic polyaniline was supported by the same procedure as described above.

[Evaluation]
The mesoporous silica (Comparative Example 3), the polyaniline-supported mesoporous silica (Comparative Example 2), and the polyaniline-supported sulfonated mesoporous silica (Example 2) were each compacted, and the electrical conductivity σ of the resulting molded product was The measurement was performed by the 4-terminal method.
Mesoporous silica and polyaniline-supported mesoporous silica were insulators, whereas polyaniline-supported sulfonated mesoporous silica exhibited electrical conductivity. Further, it was confirmed that the electrical conductivity σ of the polyaniline-supported sulfonated mesoporous silica was almost the same as that immediately after the production and at 24 h.

  Although the embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the gist of the present invention.

Thermoelectric materials according to the present invention include solar thermoelectric generators, seawater temperature difference thermoelectric generators, fossil fuel thermoelectric generators, various types of thermoelectric generators such as factory exhaust heat and automobile exhaust heat regenerative generators, photodetection elements, and laser diodes. As a thermoelectric material that constitutes thermoelectric elements used in precision temperature control devices such as field effect transistors, photomultiplier tubes, spectrophotometer cells, chromatography columns, thermostats, air conditioners, refrigerators, power supplies for watches, etc. Can be used.

Claims (8)

A carrier;
An organic compound having electrical conductivity and thermoelectric properties carried on the surface of the carrier;
A composite comprising the carrier and a dopant supported at the interface of the organic compound;
A thermoelectric material having an output factor (S ² σ) of the composite of 10 ⁻⁷ Wm ⁻¹ K ⁻² or more.   The thermoelectric material according to claim 1, wherein the dopant is fixed to the surface of the carrier by a chemical bond. A porous carrier;
The composite comprising an organic compound having electrical conductivity and thermoelectric properties carried in the pores of the carrier,
A thermoelectric material having an output factor (S ² σ) of the composite of 10 ⁻⁷ Wm ⁻¹ K ⁻² or more.   The thermoelectric material according to claim 3, further comprising a dopant supported at an interface between the organic compound and the inner wall surface of the pore.   The thermoelectric material according to claim 4, wherein the dopant is fixed to the inner wall surface of the pore by a chemical bond.   The organic compound is one or more conductive polymers selected from polyacetylene-based, polyacene-based, polyaromatic vinylene-based, polypyrrole-based, polyaniline-based, and polythiophene-based compounds. Thermoelectric material.   The thermoelectric material according to claim 6, wherein the organic compound further includes a substituent. The thermoelectric material according to any one of claims 1 to 5, wherein the organic compound is an organic charge transfer complex.