WO2020255898A1 - Thermoelectric material - Google Patents

Thermoelectric material Download PDF

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WO2020255898A1
WO2020255898A1 PCT/JP2020/023300 JP2020023300W WO2020255898A1 WO 2020255898 A1 WO2020255898 A1 WO 2020255898A1 JP 2020023300 W JP2020023300 W JP 2020023300W WO 2020255898 A1 WO2020255898 A1 WO 2020255898A1
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thermoelectric
thermoelectric material
carbon
material according
nanoparticles
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PCT/JP2020/023300
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French (fr)
Japanese (ja)
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崇人 小野
ファズリ ビン サマト カイル
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国立大学法人東北大学
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L29/00—Semiconductor devices adapted for rectifying, amplifying, oscillating or switching, or capacitors or resistors with at least one potential-jump barrier or surface barrier, e.g. PN junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof  ; Multistep manufacturing processes therefor
    • H01L29/02—Semiconductor bodies ; Multistep manufacturing processes therefor
    • H01L29/06—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by their shape; characterised by the shapes, relative sizes, or dispositions of the semiconductor regions ; characterised by the concentration or distribution of impurities within semiconductor regions
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N10/00—Thermoelectric devices comprising a junction of dissimilar materials, i.e. devices exhibiting Seebeck or Peltier effects
    • H10N10/80—Constructional details
    • H10N10/85—Thermoelectric active materials
    • H10N10/851—Thermoelectric active materials comprising inorganic compositions
    • H10N10/852—Thermoelectric active materials comprising inorganic compositions comprising tellurium, selenium or sulfur
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N10/00—Thermoelectric devices comprising a junction of dissimilar materials, i.e. devices exhibiting Seebeck or Peltier effects
    • H10N10/80—Constructional details
    • H10N10/85—Thermoelectric active materials
    • H10N10/851—Thermoelectric active materials comprising inorganic compositions
    • H10N10/855—Thermoelectric active materials comprising inorganic compositions comprising compounds containing boron, carbon, oxygen or nitrogen
    • H—ELECTRICITY
    • H10—SEMICONDUCTOR DEVICES; ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N—ELECTRIC SOLID-STATE DEVICES NOT OTHERWISE PROVIDED FOR
    • H10N10/00—Thermoelectric devices comprising a junction of dissimilar materials, i.e. devices exhibiting Seebeck or Peltier effects
    • H10N10/80—Constructional details
    • H10N10/85—Thermoelectric active materials
    • H10N10/857—Thermoelectric active materials comprising compositions changing continuously or discontinuously inside the material

Definitions

  • the present invention relates to thermoelectric materials.
  • Bi 2 Te 3 is known as a thermoelectric conversion material that can be plated on the surface of an object to be treated and has excellent thermoelectric characteristics in a low temperature region of about room temperature.
  • the electrodeposited Bi 2 Te 3 has a dimensionless figure of merit ZT (where Z is a figure of merit and T is an absolute temperature) of about 0.1 to 0.16, which is smaller than that of a bulk-like one. The value is shown (see, for example, Non-Patent Document 1 or 2). Therefore, in order to enhance the thermoelectric characteristics, a composite material in which Pt nanoparticles or carbon nanotubes (CNTs) are dispersed in Bi 2 Te 3 has been developed.
  • ZT dimensionless figure of merit
  • T is an absolute temperature
  • thermoelectric material composed of a composite material of Bi 2 Te 3 and Pt nanoparticles
  • it is formed by electrodeposition coating by an electrochemical reaction, and power factor S 2 ⁇ (where S is Seebeck).
  • S power factor
  • a coefficient (the coefficient, ⁇ is an electrical conductivity) of 1800 ⁇ W / m ⁇ K 2 and a dimensionless performance index ZT of 0.61 have been developed by the present inventor (see, for example, Non-Patent Document 3).
  • thermoelectric material composed of a composite material of Bi 2 Te 3 and multi-walled carbon nanotubes (MWCNT)
  • MWCNT multi-walled carbon nanotubes
  • thermoelectric material described in Non-Patent Document 3 has excellent thermoelectric characteristics because the values of the output factor S 2 ⁇ and the dimensionless performance index ZT are increased by dispersing Pt nanoparticles in the thermoelectric conversion material. However, considering applications such as power generation, cooling, and exhaust heat recovery, the development of thermoelectric materials having better thermoelectric characteristics is desired. Further, the thermoelectric material described in Non-Patent Document 4 can reduce the electric resistance by dispersing the multilayer carbon nanotubes in the thermoelectric conversion material, but is compared with the thermoelectric material described in Non-Patent Document 3, Seebeck. Since it is considered that the absolute value of the coefficient S is small and the thermal conductivity ⁇ is large, the values of the output factor S 2 ⁇ and the dimensionless performance index ZT are small, and there is a problem that the thermoelectric characteristics are inferior.
  • the present invention has been made focusing on such a problem, and an object of the present invention is to provide a thermoelectric material capable of obtaining more excellent thermoelectric characteristics.
  • thermoelectric material according to the present invention is characterized by being composed of a thermoelectric conversion material, a carbon nanomaterial having one or more pores, and a composite material containing metal nanoparticles.
  • thermoelectric material according to the present invention is composed of a thermoelectric conversion material, a carbon nanomaterial having one or more pores, and a composite material containing metal nanoparticles, conventionally, only Pt nanoparticles are dispersed in the thermoelectric conversion material.
  • the values of the output factor S 2 ⁇ and the dimensionless performance index ZT are larger than those of the conventional one in which only the multilayer carbon nanotubes are dispersed in the thermoelectric conversion material, and more excellent thermoelectric characteristics can be obtained.
  • the carbon nanomaterial is preferably porous carbon particles and / or carbon nanotubes. More specifically, the carbon nanomaterial may be composed of single-walled carbon nanotubes having a diameter of 20 nm or less, or may be composed of porous carbon particles having a porosity of 8 or more. Further, the carbon nanomaterial may be made of porous carbon black having a particle size of 100 nm or less. In these cases, particularly excellent thermoelectric characteristics can be obtained.
  • the metal nanoparticles are preferably composed of particles containing at least one of Ni, Pt, Ag, Au, Co, Fe, Cu and Pd. Further, the metal nanoparticles preferably have a particle diameter of 50 nm or less, more preferably 40 nm or less, and further preferably 20 nm or less. In these cases, particularly excellent thermoelectric characteristics can be obtained.
  • thermoelectric material according to the present invention preferably contains the carbon nanomaterial in an amount of 6 wt% to 9 wt% and the metal nanoparticles in an amount of 0.5 wt% to 1 wt%. In this case, particularly excellent thermoelectric characteristics can be obtained.
  • the thermoelectric conversion material preferably comprises a substance that can be plated on the surface of the object to be treated.
  • a substance that can be plated on the surface of the object to be treated for example, Bi, Te and Sb such as Bi 2 Te 3 and Sb 2 Te 3 It may be a substance containing at least two or more of them.
  • the plating process forms a thin film on the surface of the object to be treated, so that the surface of the object to be processed can be covered. As a result, a film having excellent thermoelectric characteristics can be obtained.
  • the thermoelectric conversion material comprises a substance used for a plating process such as electroplating, hot-dip plating, electroless plating, vacuum plating, vapor phase plating, and electroplating (electroplating).
  • thermoelectric material according to the present invention has, for example, an output factor S 2 ⁇ (where S is a Seebeck coefficient and ⁇ is an electrical conductivity) of 1000 ⁇ W / m ⁇ K 2 or more, and has a dimensionless figure of merit ZT (here). (Z is a figure of merit and T is an absolute temperature) is 0.65 or more.
  • the thermoelectric material according to the present invention has more excellent thermoelectric characteristics than the conventional one, and is effective when used for power generation, cooling, waste heat recovery, and the like.
  • thermoelectric material capable of obtaining more excellent thermoelectric characteristics.
  • thermoelectric material of the Bi 2 Te 3 thin film (A) Scanning electron microscope (SEM) photograph of the thermoelectric material of the Bi 2 Te 3 thin film, (b) Scanning electron micrograph of the thermoelectric material according to the embodiment of the present invention, (c) Part of (b). It is a magnified scanning electron micrograph.
  • SEM Scanning electron microscope
  • ⁇ Seebeck coefficient S and electrical conductivity ⁇ of the thermoelectric material and Bi 2 Te 3 thin film of the embodiment of the present invention and the content of Pt nanoparticles
  • PF power factor
  • thermoelectric material of the Bi 2 Te 3 thin film (A) Scanning electron micrograph of the thermoelectric material of the Bi 2 Te 3 thin film, (b) Scanning electron micrograph of the thermoelectric material in which carbon black is dispersed in Bi 2 Te 3 according to the embodiment of the present invention. ..
  • the relationship between the content of Bi 2 Te 3 in which carbon black is dispersed thermoelectric material and Bi 2 Te 3 thin film (a) the Seebeck coefficient (Seebeck coefficient) S and carbon (Carbon) The graph shown, (b) the graph showing the relationship between the electrical conductivity ⁇ and the carbon (Carbon) content, (c) the power factor (PF) and the carbon (Carbon) content. It is a graph which shows the relationship.
  • thermoelectric material of the embodiment of the present invention comprises a thermoelectric conversion material, a carbon nanomaterial having one or more pores, and a composite material containing metal nanoparticles.
  • the thermoelectric material of the embodiment of the present invention contains 6 wt% to 9 wt% of carbon nanomaterials and 0.5 wt% to 1 wt% of metal nanoparticles.
  • thermoelectric conversion material is composed of a substance that can be plated on the surface of the object to be treated, and is used for plating such as electroplating, hot-dip plating, electroless plating, vacuum plating, vapor phase plating, and electroplating (electroplating). Consists of the substances used.
  • the thermoelectric conversion material is preferably a substance containing at least two or more of Bi, Te and Sb, and a specific example is Bi 2 Te 3 and Sb 2 Te 3 which can be electrodeposited.
  • Carbon nanomaterials consist of porous carbon particles or carbon nanotubes.
  • the carbon nanomaterial is a single-walled carbon nanotube having a diameter of 20 nm or less, or a porous carbon black having a porosity of 8 or more and a particle diameter of 100 nm or less.
  • the metal nanoparticles have a particle diameter of 20 nm or less and are composed of particles containing at least one of Ni, Pt, Ag, Au, Co, Fe, Cu and Pd.
  • thermoelectric material of the embodiment of the present invention is composed of a thermoelectric conversion material, a carbon nanomaterial having one or more pores, and a composite material containing metal nanoparticles, only Pt nanoparticles are dispersed in the thermoelectric conversion material.
  • the values of the output factor S 2 ⁇ and the dimensionless performance index ZT are larger, and more excellent thermoelectric characteristics can be obtained. Can be done. Therefore, for example, it is effective when used for power generation, cooling, waste heat recovery, and the like.
  • thermoelectric material according to the embodiment of the present invention is formed into a thin film on the surface of the object to be treated by the plating treatment, and can cover the surface of the object to be treated. As a result, a film having excellent thermoelectric characteristics can be obtained.
  • thermoelectric material in which carbon nanotubes and Pt nanoparticles are dispersed in Bi 2 Te 3 Using Bi 2 Te 3 as the thermoelectric conversion material, single-walled carbon nanotubes (SWCNT) as the carbon nanomaterial, and Pt nanoparticles as the metal nanoparticles, the thermoelectric material was produced as follows. That is, first, single-walled carbon nanotubes and Pt nanoparticles were added to an acidic aqueous solution (electrolyte solution) containing Bi-Te ions, and the atmosphere was stirred while being replaced with nitrogen gas.
  • acidic aqueous solution electrophilic aqueous solution
  • a working electrode (WE), a counter electrode (CE), and a reference electrode (RE) are placed in the stirred solution, and the potential between the working electrode and the reference electrode is controlled by a potentiostat while facing the working electrode. Electroplating was performed by passing a current between the electrode and the electrode. In this way, a thin-film thermoelectric material was formed on the surface of the working electrode.
  • the electrolytic solution used was a solution of Te 2 O 3 and Bi 2 O 4 in an aqueous solution of nitric acid (HNO 3 ). Further, the aqueous solution is not limited to the nitric acid aqueous solution, and an aqueous solution of Ni (NO 3 ) 2 or (NH 4 ) 2 PtCl 6 can also be used.
  • a gold-coated silicon substrate was used as the working electrode, platinum was used as the counter electrode, and silver chloride was used as the reference electrode.
  • thermoelectric material samples Pt-SWCNTs / Bi 2 Te 3- I, II, III with different Pt nanoparticles content were used to measure the thermoelectric properties of the thermoelectric material.
  • Each sample has a Pt nanoparticle content of 0.4 wt%, 0.6 wt%, and 0.9 wt%, and a single-walled carbon nanotube (SWCNT) content of 5.7 to 7.8 wt%.
  • SWCNT single-walled carbon nanotube
  • FIGS. 1 (b) and 1 (c) Scanning electron microscope (SEM) photographs of the prepared samples Pt-SWCNTs / Bi 2 Te 3- I and Bi 2 Te 3 thin films are shown in FIG.
  • the sample Pt-SWCNTs / Bi 2 Te 3- I to which the single-walled carbon nanotubes and Pt nanoparticles were added is the Bi 2 Te 3 thin film of FIG. 1 (a).
  • the crystals of Bi 2 Te 3 were finer.
  • FIG. 1 (c) it was also confirmed that in the sample Pt-SWCNTs / Bi 2 Te 3- I, crystals of Bi 2 Te 3 were grown on the surface of the single-walled carbon nanotubes.
  • the output factor PF becomes 1000 ⁇ W / m ⁇ K 2 or more when the content of Pt nanoparticles is 0.6 wt% and 0.9 wt%, which is 0.6 wt%. It was confirmed that it sometimes showed a peak.
  • the peak value of the output factor PF is about 1800 ⁇ W / m ⁇ K 2 .
  • the value of thermal conductivity ⁇ decreases as the content of Pt nanoparticles increases. It was also confirmed that the dimensionless figure of merit ZT was 0.85 or more when the content of Pt nanoparticles was 0.6 wt% and 0.9 wt%, and peaked at 0.6 wt%. The peak value of the dimensionless figure of merit ZT is 0.99.
  • thermoelectric material sample (thickness; 4.5 ⁇ m) having a Pt nanoparticle content of 0.9 wt% and a single-walled carbon nanotube (SWCNT) content of 6.8 to 8.5 wt% was produced. Then, the hardness was measured by the nanoindentation method. For comparison, the hardness of the Bi 2 Te 3 thin film (thickness: 9.5 ⁇ m) was measured in the same manner. As a result of the measurement, the content of Pt nanoparticles 0.9 wt% of the samples, the hardness was from 39.2 to 42.0 in terms 0.67 ⁇ 0.73 GPa, and the Vickers hardness H V.
  • thermoelectric material was hardened by adding the single-walled carbon nanotubes and Pt nanoparticles.
  • Bi 2 Te 3 as the thermoelectric conversion material
  • carbon black powder as the carbon nanomaterial
  • the thermoelectric material was produced in the same manner as each sample in Table 1.
  • the thermoelectric material produced does not contain metal nanoparticles.
  • porous Ketjen Black (“EC600JD” manufactured by Lion Specialty Chemicals Co., Ltd .; Porousness 13.7) was used.
  • carbon black was used after being coated with PDDA (polydiallyldimethylammonium chloride).
  • thermoelectric properties of the thermoelectric material As shown in Table 2, in order to measure the thermoelectric properties of the thermoelectric material, three types of samples (CB / Bi 2 Te 3- I, II, III) with different carbon (C) contents were prepared. .. Each sample has a carbon content of 3.4 wt%, 3.7 wt% and 4.3 wt%, respectively.
  • CB / Bi 2 Te 3- I, II, III three types of samples with different carbon (C) contents were prepared. ..
  • CB / Bi 2 Te 3- I, II, III three types of samples (CB / Bi 2 Te 3- I, II, III) with different carbon (C) contents were prepared. .. Each sample has a carbon content of 3.4 wt%, 3.7 wt% and 4.3 wt%, respectively.
  • the Bi 2 Te 3 thin films in Table 1 are also shown in Table 2.
  • thermoelectric materials were produced in the same manner as in each sample in Table 1.
  • the thermoelectric material produced does not contain metal nanoparticles.
  • thermoelectric properties of thermoelectric materials As shown in Table 3, three types of samples (SWCNTs / Bi 2 Te 3- I, II, III, and MWCNTs / Bi) with different carbon contents were used to measure the thermoelectric properties of thermoelectric materials. 2 Te 3- I, II, III) was manufactured. Each sample has a carbon content of 3.8 wt%, 4.1 wt%, 4.4 wt%, 3.6 wt%, 4.1 wt% and 4.8 wt%, respectively.
  • the Bi 2 Te 3 thin films in Table 1 are also shown in Table 3.
  • the output factor PF is about 790 to 950 ⁇ W / m ⁇ K 2 in the sample to which carbon black is added, which is larger than that in the sample to which carbon nanotubes are added. It was confirmed that it was. Further, as shown in Table 2, it was confirmed that the dimensionless figure of merit ZT was 0.64 in the sample to which carbon black was added, which was larger than that of the Bi 2 Te 3 thin film.
  • thermoelectric material in which carbon nanotubes and Pt nanoparticles are dispersed in Bi 2 Te 3 (see, for example, FIGS. 2 and 3) and a thermoelectric material in which carbon black or carbon nanotubes are dispersed in Bi 2 Te 3
  • the thermoelectric material in which both carbon nanotubes and Pt nanoparticles are dispersed has an output factor PF of 1000 ⁇ W / m ⁇ K 2 by adjusting their contents.
  • the dimensionless performance index ZT is 0.65 or more, and it can be said that excellent thermoelectric characteristics can be obtained as compared with the thermoelectric material to which only one of carbon black and carbon nanotube is added.

Abstract

[Problem] To provide a thermoelectric material which is capable of achieving more excellent thermoelectric characteristics. [Solution] A thermoelectric material according to the present invention is composed of a composite material that contains a thermoelectric conversion material, a carbon nanomaterial having one or more pores, and metal nanoparticles. It is preferable that the thermoelectric conversion material is composed of a substance that is able to be plated on the surface of an object to be processed. It is preferable that the carbon nanomaterial is composed of porous carbon particles and/or carbon nanotubes. It is preferable that the metal nanoparticles are composed of particles that contain at least one of Ni, Pt, Ag, Au, Co, Fe, Cu and Pd. It is preferable that the thermoelectric material contains from 6 wt% to 9 wt% of the carbon nanomaterial and from 0.5 wt% to 1 wt% of the metal nanoparticle.

Description

熱電材料Thermoelectric material
　本発明は、熱電材料に関する。 The present invention relates to thermoelectric materials.
　従来、被処理物の表面にメッキ処理可能な熱電変換材料のうち、室温程度の低温領域で優れた熱電特性を有するものとして、Ｂｉ２Ｔｅ３が知られている。電着塗装されたＢｉ２Ｔｅ３は、無次元性能指数ＺＴ（ここで、Ｚは性能指数、Ｔは絶対温度である）が０．１～０．１６程度であり、バルク状のものより小さい値を示す（例えば、非特許文献１または２参照）。そこで、熱電特性を高めるために、Ｂｉ２Ｔｅ３の中にＰｔナノ粒子またはカーボンナノチューブ（ＣＮＴ）を分散させた複合材料が開発されている。 Conventionally, Bi 2 Te 3 is known as a thermoelectric conversion material that can be plated on the surface of an object to be treated and has excellent thermoelectric characteristics in a low temperature region of about room temperature. The electrodeposited Bi 2 Te 3 has a dimensionless figure of merit ZT (where Z is a figure of merit and T is an absolute temperature) of about 0.1 to 0.16, which is smaller than that of a bulk-like one. The value is shown (see, for example, Non-Patent Document 1 or 2). Therefore, in order to enhance the thermoelectric characteristics, a composite material in which Pt nanoparticles or carbon nanotubes (CNTs) are dispersed in Bi 2 Te 3 has been developed.
　例えば、Ｂｉ２Ｔｅ３とＰｔナノ粒子との複合材料から成る熱電材料として、電気化学反応により電着塗装を行うことにより形成され、出力因子（Power Factor）Ｓ２σ（ここで、Ｓはゼーベック係数、σは電気伝導度である）が１８００μＷ／ｍ・Ｋ２、無次元性能指数ＺＴが０．６１のものが、本発明者により開発されている（例えば、非特許文献３参照）。この熱電材料は、Ｂｉ２Ｔｅ３中に分散したＰｔナノ粒子でのフォノン散乱により熱伝導率κが低下するため、無次元性能指数ＺＴ（＝Ｓ２σＴ／κ）が大きくなっているものと考えられる。 For example, as a thermoelectric material composed of a composite material of Bi 2 Te 3 and Pt nanoparticles, it is formed by electrodeposition coating by an electrochemical reaction, and power factor S 2 σ (where S is Seebeck). A coefficient (the coefficient, σ is an electrical conductivity) of 1800 μW / m · K 2 and a dimensionless performance index ZT of 0.61 have been developed by the present inventor (see, for example, Non-Patent Document 3). In this thermoelectric material, the thermal conductivity κ decreases due to phonon scattering in Pt nanoparticles dispersed in Bi 2 Te 3 , so the dimensionless figure of merit ZT (= S 2 σT / κ) is large. Conceivable.
　また、Ｂｉ２Ｔｅ３と多層カーボンナノチューブ（ＭＷＣＮＴ）との複合材料から成る熱電材料として、電気化学反応による電着塗装で形成され、電気抵抗を０．９３×１０－５Ω・ｍまで低下させたものが開発されている（例えば、非特許文献４参照）。 Further, as a thermoelectric material composed of a composite material of Bi 2 Te 3 and multi-walled carbon nanotubes (MWCNT), it is formed by electrodeposition coating by an electrochemical reaction, and the electric resistance is reduced to 0.93 × 10 -5 Ω · m. Has been developed (see, for example, Non-Patent Document 4).
　非特許文献３に記載の熱電材料は、熱電変換材料にＰｔナノ粒子を分散させることにより、出力因子Ｓ２σおよび無次元性能指数ＺＴの値が大きくなり、優れた熱電特性を有しているが、発電や冷却、排熱回収などへの応用を考慮すると、より優れた熱電特性を有する熱電材料の開発が望まれている。また、非特許文献４に記載の熱電材料は、熱電変換材料に多層カーボンナノチューブを分散させることにより、電気抵抗を小さくすることはできるが、非特許文献３に記載の熱電材料と比べると、ゼーベック係数Ｓの絶対値が小さく、熱伝導率κが大きくなると考えられるため、出力因子Ｓ２σおよび無次元性能指数ＺＴの値は小さくなり、熱電特性に劣るという課題があった。 The thermoelectric material described in Non-Patent Document 3 has excellent thermoelectric characteristics because the values of the output factor S 2 σ and the dimensionless performance index ZT are increased by dispersing Pt nanoparticles in the thermoelectric conversion material. However, considering applications such as power generation, cooling, and exhaust heat recovery, the development of thermoelectric materials having better thermoelectric characteristics is desired. Further, the thermoelectric material described in Non-Patent Document 4 can reduce the electric resistance by dispersing the multilayer carbon nanotubes in the thermoelectric conversion material, but is compared with the thermoelectric material described in Non-Patent Document 3, Seebeck. Since it is considered that the absolute value of the coefficient S is small and the thermal conductivity κ is large, the values of the output factor S 2 σ and the dimensionless performance index ZT are small, and there is a problem that the thermoelectric characteristics are inferior.
　本発明は、このような課題に着目してなされたもので、より優れた熱電特性を得ることができる熱電材料を提供することを目的とする。 The present invention has been made focusing on such a problem, and an object of the present invention is to provide a thermoelectric material capable of obtaining more excellent thermoelectric characteristics.
　上記目的を達成するために、本発明に係る熱電材料は、熱電変換材料と、１または複数の孔を有する炭素ナノ材料と、金属ナノ粒子とを含む複合材料から成ることを特徴とする。 In order to achieve the above object, the thermoelectric material according to the present invention is characterized by being composed of a thermoelectric conversion material, a carbon nanomaterial having one or more pores, and a composite material containing metal nanoparticles.
　本発明に係る熱電材料は、熱電変換材料と、１または複数の孔を有する炭素ナノ材料と、金属ナノ粒子とを含む複合材料から成るため、熱電変換材料にＰｔナノ粒子のみを分散させた従来のものや、熱電変換材料に多層カーボンナノチューブのみを分散させた従来のものと比べて、出力因子Ｓ２σや無次元性能指数ＺＴの値が大きく、より優れた熱電特性を得ることができる。 Since the thermoelectric material according to the present invention is composed of a thermoelectric conversion material, a carbon nanomaterial having one or more pores, and a composite material containing metal nanoparticles, conventionally, only Pt nanoparticles are dispersed in the thermoelectric conversion material. The values of the output factor S 2 σ and the dimensionless performance index ZT are larger than those of the conventional one in which only the multilayer carbon nanotubes are dispersed in the thermoelectric conversion material, and more excellent thermoelectric characteristics can be obtained.
　本発明に係る熱電材料で、前記炭素ナノ材料は、多孔質の炭素粒子および／またはカーボンナノチューブであることが好ましい。より具体的には、前記炭素ナノ材料は、直径が２０ｎｍ以下の単層カーボンナノチューブから成っていてもよく、多孔度が８以上の多孔質の炭素粒子から成っていてもよい。また、前記炭素ナノ材料は、粒子径が１００ｎｍ以下の多孔質のカーボンブラックから成っていてもよい。これらの場合、特に優れた熱電特性を得ることができる。 In the thermoelectric material according to the present invention, the carbon nanomaterial is preferably porous carbon particles and / or carbon nanotubes. More specifically, the carbon nanomaterial may be composed of single-walled carbon nanotubes having a diameter of 20 nm or less, or may be composed of porous carbon particles having a porosity of 8 or more. Further, the carbon nanomaterial may be made of porous carbon black having a particle size of 100 nm or less. In these cases, particularly excellent thermoelectric characteristics can be obtained.
　本発明に係る熱電材料で、前記金属ナノ粒子は、Ｎｉ、Ｐｔ、Ａｇ、Ａｕ、Ｃｏ、Ｆｅ、ＣｕおよびＰｄのうちの少なくとも１つを含む粒子から成ることが好ましい。また、前記金属ナノ粒子は、粒子径が５０ｎｍ以下であることが好ましく、粒子径が４０ｎｍ以下、さらに２０ｎｍ以下であることがより好ましい。これらの場合、特に優れた熱電特性を得ることができる。 In the thermoelectric material according to the present invention, the metal nanoparticles are preferably composed of particles containing at least one of Ni, Pt, Ag, Au, Co, Fe, Cu and Pd. Further, the metal nanoparticles preferably have a particle diameter of 50 nm or less, more preferably 40 nm or less, and further preferably 20 nm or less. In these cases, particularly excellent thermoelectric characteristics can be obtained.
　本発明に係る熱電材料は、前記炭素ナノ材料を６ｗｔ％乃至９ｗｔ％含み、前記金属ナノ粒子を０．５ｗｔ％乃至１ｗｔ％含むことが好ましい。この場合、特に優れた熱電特性を得ることができる。 The thermoelectric material according to the present invention preferably contains the carbon nanomaterial in an amount of 6 wt% to 9 wt% and the metal nanoparticles in an amount of 0.5 wt% to 1 wt%. In this case, particularly excellent thermoelectric characteristics can be obtained.
　本発明に係る熱電材料で、前記熱電変換材料は、被処理物の表面にメッキ処理可能な物質から成ることが好ましく、例えば、Ｂｉ２Ｔｅ３やＳｂ２Ｔｅ３など、Ｂｉ、ＴｅおよびＳｂのうちの少なくとも２種類以上を含む物質であってもよい。この場合、メッキ処理により、被処理物の表面に薄膜状に形成され、被処理物の表面を覆うことができる。これにより、優れた熱電特性を有する被膜を得ることができる。熱電変換材料は、例えば、電気メッキ、溶融メッキ、無電解メッキ、真空メッキ、気相メッキ、電気メッキ（電着塗装）などのメッキ処理に使用される物質から成る。 In the thermoelectric material according to the present invention, the thermoelectric conversion material preferably comprises a substance that can be plated on the surface of the object to be treated. For example, Bi, Te and Sb such as Bi 2 Te 3 and Sb 2 Te 3 It may be a substance containing at least two or more of them. In this case, the plating process forms a thin film on the surface of the object to be treated, so that the surface of the object to be processed can be covered. As a result, a film having excellent thermoelectric characteristics can be obtained. The thermoelectric conversion material comprises a substance used for a plating process such as electroplating, hot-dip plating, electroless plating, vacuum plating, vapor phase plating, and electroplating (electroplating).
　本発明に係る熱電材料は、例えば、出力因子Ｓ２σ（ここで、Ｓはゼーベック係数、σは電気伝導度である）が１０００μＷ／ｍ・Ｋ２以上であり、無次元性能指数ＺＴ（ここで、Ｚは性能指数、Ｔは絶対温度である）が０．６５以上である。本発明に係る熱電材料は、従来よりも優れた熱電特性を有しており、例えば、発電や冷却、排熱回収などに利用されると効果的である。 The thermoelectric material according to the present invention has, for example, an output factor S 2 σ (where S is a Seebeck coefficient and σ is an electrical conductivity) of 1000 μW / m · K 2 or more, and has a dimensionless figure of merit ZT (here). (Z is a figure of merit and T is an absolute temperature) is 0.65 or more. The thermoelectric material according to the present invention has more excellent thermoelectric characteristics than the conventional one, and is effective when used for power generation, cooling, waste heat recovery, and the like.
　本発明によれば、より優れた熱電特性を得ることができる熱電材料を提供することができる。 According to the present invention, it is possible to provide a thermoelectric material capable of obtaining more excellent thermoelectric characteristics.
（ａ）Bi2Te3薄膜の熱電材料の走査型電子顕微鏡（ＳＥＭ）写真、（ｂ）本発明の実施の形態の熱電材料の走査型電子顕微鏡写真、（ｃ）　（ｂ）の一部を拡大した走査型電子顕微鏡写真である。(A) Scanning electron microscope (SEM) photograph of the thermoelectric material of the Bi 2 Te 3 thin film, (b) Scanning electron micrograph of the thermoelectric material according to the embodiment of the present invention, (c) Part of (b). It is a magnified scanning electron micrograph. 本発明の実施の形態の熱電材料およびBi2Te3薄膜の（ａ）ゼーベック係数（Seebeck coefficient）Ｓおよび電気伝導度（Electrical conductivity）σとＰｔナノ粒子の含有量との関係を示すグラフ、（ｂ）出力因子（Power Factor；ＰＦ）とＰｔナノ粒子の含有量との関係を示すグラフである。A graph showing the relationship between (a) Seebeck coefficient S and electrical conductivity σ of the thermoelectric material and Bi 2 Te 3 thin film of the embodiment of the present invention and the content of Pt nanoparticles, ( b) It is a graph which shows the relationship between the power factor (PF) and the content of Pt nanoparticles. 本発明の実施の形態の熱電材料およびBi2Te3薄膜の、熱伝導率（Thermal Conductivity）κおよび無次元性能指数ＺＴとＰｔナノ粒子の含有量との関係を示すグラフである。It is a graph which shows the relationship between the thermal conductivity (Thermal Conductivity) κ and the dimensionless figure of merit ZT and the content of Pt nanoparticles of the thermoelectric material and the Bi 2 Te 3 thin film of the embodiment of this invention. （ａ）Bi2Te3薄膜の熱電材料の走査型電子顕微鏡写真、（ｂ）本発明の実施の形態に関する、Bi2Te3にカーボンブラックを分散させた熱電材料の走査型電子顕微鏡写真である。(A) Scanning electron micrograph of the thermoelectric material of the Bi 2 Te 3 thin film, (b) Scanning electron micrograph of the thermoelectric material in which carbon black is dispersed in Bi 2 Te 3 according to the embodiment of the present invention. .. 本発明の実施の形態に関する、Bi2Te3にカーボンブラックを分散させた熱電材料およびBi2Te3薄膜の（ａ）ゼーベック係数（Seebeck coefficient）Ｓと炭素（Carbon）の含有量との関係を示すグラフ、（ｂ）電気伝導度（Electrical conductivity）σと炭素（Carbon）の含有量との関係を示すグラフ、（ｃ）出力因子（Power Factor；ＰＦ）と炭素（Carbon）の含有量との関係を示すグラフである。Regarding the embodiment of the present invention, the relationship between the content of Bi 2 Te 3 in which carbon black is dispersed thermoelectric material and Bi 2 Te 3 thin film (a) the Seebeck coefficient (Seebeck coefficient) S and carbon (Carbon) The graph shown, (b) the graph showing the relationship between the electrical conductivity σ and the carbon (Carbon) content, (c) the power factor (PF) and the carbon (Carbon) content. It is a graph which shows the relationship.
　以下、実施例等に基づいて、本発明の実施の形態について説明する。
　本発明の実施の形態の熱電材料は、熱電変換材料と、１または複数の孔を有する炭素ナノ材料と、金属ナノ粒子とを含む複合材料から成っている。本発明の実施の形態の熱電材料は、炭素ナノ材料を６ｗｔ％乃至９ｗｔ％含み、金属ナノ粒子を０．５ｗｔ％乃至１ｗｔ％含んでいる。 Hereinafter, embodiments of the present invention will be described based on examples and the like.
The thermoelectric material of the embodiment of the present invention comprises a thermoelectric conversion material, a carbon nanomaterial having one or more pores, and a composite material containing metal nanoparticles. The thermoelectric material of the embodiment of the present invention contains 6 wt% to 9 wt% of carbon nanomaterials and 0.5 wt% to 1 wt% of metal nanoparticles.
　熱電変換材料は、被処理物の表面にメッキ処理可能な物質から成り、例えば、電気メッキ、溶融メッキ、無電解メッキ、真空メッキ、気相メッキ、電気メッキ（電着塗装）などのメッキ処理に使用される物質から成る。熱電変換材料は、Ｂｉ、ＴｅおよびＳｂのうちの少なくとも２種類以上を含む物質であることが好ましく、具体的な一例では、電着塗装可能なＢｉ２Ｔｅ３や、Ｓｂ２Ｔｅ３である。 The thermoelectric conversion material is composed of a substance that can be plated on the surface of the object to be treated, and is used for plating such as electroplating, hot-dip plating, electroless plating, vacuum plating, vapor phase plating, and electroplating (electroplating). Consists of the substances used. The thermoelectric conversion material is preferably a substance containing at least two or more of Bi, Te and Sb, and a specific example is Bi 2 Te 3 and Sb 2 Te 3 which can be electrodeposited.
　炭素ナノ材料は、多孔質の炭素粒子、または、カーボンナノチューブから成る。具体的な一例では、炭素ナノ材料は、直径が２０ｎｍ以下の単層カーボンナノチューブや、多孔度が８以上で、粒子径が１００ｎｍ以下の多孔質のカーボンブラックである。金属ナノ粒子は、粒子径が２０ｎｍ以下であり、Ｎｉ、Ｐｔ、Ａｇ、Ａｕ、Ｃｏ、Ｆｅ、ＣｕおよびＰｄのうちの少なくとも１つを含む粒子から成る。 Carbon nanomaterials consist of porous carbon particles or carbon nanotubes. As a specific example, the carbon nanomaterial is a single-walled carbon nanotube having a diameter of 20 nm or less, or a porous carbon black having a porosity of 8 or more and a particle diameter of 100 nm or less. The metal nanoparticles have a particle diameter of 20 nm or less and are composed of particles containing at least one of Ni, Pt, Ag, Au, Co, Fe, Cu and Pd.
　次に、作用について説明する。
　本発明の実施の形態の熱電材料は、熱電変換材料と、１または複数の孔を有する炭素ナノ材料と、金属ナノ粒子とを含む複合材料から成るため、熱電変換材料にＰｔナノ粒子のみを分散させた従来のものや、熱電変換材料に多層カーボンナノチューブのみを分散させた従来のものと比べて、出力因子Ｓ２σや無次元性能指数ＺＴの値が大きく、より優れた熱電特性を得ることができる。このため、例えば、発電や冷却、排熱回収などに利用されると効果的である。 Next, the action will be described.
Since the thermoelectric material of the embodiment of the present invention is composed of a thermoelectric conversion material, a carbon nanomaterial having one or more pores, and a composite material containing metal nanoparticles, only Pt nanoparticles are dispersed in the thermoelectric conversion material. Compared with the conventional one in which only the multilayer carbon nanotubes are dispersed in the thermoelectric conversion material, the values of the output factor S 2 σ and the dimensionless performance index ZT are larger, and more excellent thermoelectric characteristics can be obtained. Can be done. Therefore, for example, it is effective when used for power generation, cooling, waste heat recovery, and the like.
　また、本発明の実施の形態の熱電材料は、メッキ処理により、被処理物の表面に薄膜状に形成され、被処理物の表面を覆うことができる。これにより、優れた熱電特性を有する被膜を得ることができる。 Further, the thermoelectric material according to the embodiment of the present invention is formed into a thin film on the surface of the object to be treated by the plating treatment, and can cover the surface of the object to be treated. As a result, a film having excellent thermoelectric characteristics can be obtained.
［Ｂｉ２Ｔｅ３にカーボンナノチューブとＰｔナノ粒子とを分散させた熱電材料］
　熱電変換材料としてＢｉ２Ｔｅ３、炭素ナノ材料として単層カーボンナノチューブ（ＳＷＣＮＴ）、金属ナノ粒子としてＰｔナノ粒子を用いて、以下のようにして熱電材料を製造した。すなわち、まず、Ｂｉ－Ｔｅイオンが入った酸性水溶液（電解液）に、単層カーボンナノチューブとＰｔナノ粒子とを加え、雰囲気を窒素ガスで置換しながら撹拌した。撹拌後の溶液に、作用電極（ＷＥ）と対向電極（ＣＥ）と参照電極（ＲＥ）とを入れ、ポテンショスタットにより、作用電極と参照電極との間の電位を制御しつつ、作用電極と対向電極との間に電流を流して電気メッキを行った。こうして、作用電極の表面に薄膜状の熱電材料を形成した。 [Thermoelectric material in which carbon nanotubes and Pt nanoparticles are dispersed in Bi 2 Te 3 ]
Using Bi 2 Te 3 as the thermoelectric conversion material, single-walled carbon nanotubes (SWCNT) as the carbon nanomaterial, and Pt nanoparticles as the metal nanoparticles, the thermoelectric material was produced as follows. That is, first, single-walled carbon nanotubes and Pt nanoparticles were added to an acidic aqueous solution (electrolyte solution) containing Bi-Te ions, and the atmosphere was stirred while being replaced with nitrogen gas. A working electrode (WE), a counter electrode (CE), and a reference electrode (RE) are placed in the stirred solution, and the potential between the working electrode and the reference electrode is controlled by a potentiostat while facing the working electrode. Electroplating was performed by passing a current between the electrode and the electrode. In this way, a thin-film thermoelectric material was formed on the surface of the working electrode.
　なお、電解液は、硝酸（ＨＮＯ３）の水溶液中に、Ｔｅ２Ｏ３とＢｉ２Ｏ４を溶かしたものを使用した。また、水溶液は、硝酸水溶液に限らず、Ｎｉ（ＮＯ３）２や（ＮＨ４）２ＰｔＣｌ６の水溶液を用いることもできる。また、作用電極として金でコーティングしたシリコン基板、対向電極として白金、参照電極として塩化銀を用いた。 The electrolytic solution used was a solution of Te 2 O 3 and Bi 2 O 4 in an aqueous solution of nitric acid (HNO 3 ). Further, the aqueous solution is not limited to the nitric acid aqueous solution, and an aqueous solution of Ni (NO 3 ) 2 or (NH 4 ) 2 PtCl 6 can also be used. A gold-coated silicon substrate was used as the working electrode, platinum was used as the counter electrode, and silver chloride was used as the reference electrode.
　表１に示すように、熱電材料の熱電特性を測定するために、Ｐｔナノ粒子の含有量を変えた、３種類の熱電材料の試料（Pt-SWCNTs/ Bi2Te3-I, II, III）を製造した。各試料は、それぞれＰｔナノ粒子の含有量が 0.4 wt％、0.6 wt％、0.9 wt％であり、単層カーボンナノチューブ（ＳＷＣＮＴ）の含有量が 5.7～7.8 wt％である。また、比較のため、単層カーボンナノチューブとＰｔナノ粒子とを加えずに、電気メッキを行ったBi2Te3の薄膜から成る熱電材料も製造した。 As shown in Table 1, three types of thermoelectric material samples (Pt-SWCNTs / Bi 2 Te 3- I, II, III) with different Pt nanoparticles content were used to measure the thermoelectric properties of the thermoelectric material. ) Was manufactured. Each sample has a Pt nanoparticle content of 0.4 wt%, 0.6 wt%, and 0.9 wt%, and a single-walled carbon nanotube (SWCNT) content of 5.7 to 7.8 wt%. For comparison, a thermoelectric material consisting of an electroplated thin film of Bi 2 Te 3 was also produced without adding single-walled carbon nanotubes and Pt nanoparticles.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
　製造した試料Pt-SWCNTs/ Bi2Te3-I、および、Bi2Te3薄膜の走査型電子顕微鏡（ＳＥＭ）写真を、図１に示す。図１（ｂ）および（ｃ）に示すように、単層カーボンナノチューブとＰｔナノ粒子とを加えた試料Pt-SWCNTs/ Bi2Te3-Iは、図１（ａ）のBi2Te3薄膜と比べて、Bi2Te3の結晶が微細化していることが確認された。また、図１（ｃ）に示すように、試料Pt-SWCNTs/ Bi2Te3-Iは、単層カーボンナノチューブの表面に、Bi2Te3の結晶が成長していることも確認された。 Scanning electron microscope (SEM) photographs of the prepared samples Pt-SWCNTs / Bi 2 Te 3- I and Bi 2 Te 3 thin films are shown in FIG. As shown in FIGS. 1 (b) and 1 (c), the sample Pt-SWCNTs / Bi 2 Te 3- I to which the single-walled carbon nanotubes and Pt nanoparticles were added is the Bi 2 Te 3 thin film of FIG. 1 (a). In comparison, it was confirmed that the crystals of Bi 2 Te 3 were finer. Further, as shown in FIG. 1 (c), it was also confirmed that in the sample Pt-SWCNTs / Bi 2 Te 3- I, crystals of Bi 2 Te 3 were grown on the surface of the single-walled carbon nanotubes.
　製造した各試料のゼーベック係数（Seebeck coefficient）Ｓ、および、電気伝導度（Electrical conductivity）σを測定し、表１および図２（ａ）に示す。また、その測定結果から、各試料の出力因子（Power Factor；ＰＦ＝Ｓ２σ）を求め、表１および図２（ｂ）に示す。また、各試料の熱伝導率（Thermal Conductivity）κを測定して、無次元性能指数ＺＴ（＝Ｓ２σＴ／κ）を求め、表１および図３に示す。 The Seebeck coefficient S and the electrical conductivity σ of each of the produced samples were measured and shown in Table 1 and FIG. 2 (a). Further, the power factor (PF = S 2 σ) of each sample was obtained from the measurement results, and is shown in Table 1 and FIG. 2 (b). In addition, the thermal conductivity κ of each sample was measured to obtain the dimensionless figure of merit ZT (= S 2 σT / κ), which is shown in Table 1 and FIG.
　図２（ａ）に示すように、Ｐｔナノ粒子の含有量が多くなるに従って、ゼーベック係数Ｓの絶対値が大きくなり、電気伝導度σの値は小さくなることが確認された。また、図２（ｂ）に示すように、出力因子ＰＦは、Ｐｔナノ粒子の含有量が 0.6 wt％および 0.9 wt％のときに、1000 μW/m・K2以上になり、0.6 wt％のときにピークを示すことが確認された。その出力因子ＰＦのピーク値は、約1800 μW/m・K2である。 As shown in FIG. 2A, it was confirmed that as the content of Pt nanoparticles increased, the absolute value of the Seebeck coefficient S increased and the value of the electric conductivity σ decreased. Further, as shown in FIG. 2 (b), the output factor PF becomes 1000 μW / m · K 2 or more when the content of Pt nanoparticles is 0.6 wt% and 0.9 wt%, which is 0.6 wt%. It was confirmed that it sometimes showed a peak. The peak value of the output factor PF is about 1800 μW / m · K 2 .
　図３に示すように、Ｐｔナノ粒子の含有量が多くなるに従って、熱伝導率κの値が小さくなることが確認された。また、無次元性能指数ＺＴは、Ｐｔナノ粒子の含有量が 0.6 wt％および 0.9 wt％のときに、0.85以上になり、0.6 wt％のときにピークを示すことが確認された。その無次元性能指数ＺＴのピーク値は、0.99である。 As shown in FIG. 3, it was confirmed that the value of thermal conductivity κ decreases as the content of Pt nanoparticles increases. It was also confirmed that the dimensionless figure of merit ZT was 0.85 or more when the content of Pt nanoparticles was 0.6 wt% and 0.9 wt%, and peaked at 0.6 wt%. The peak value of the dimensionless figure of merit ZT is 0.99.
　表１の各試料と同様にして、Ｐｔナノ粒子の含有量が0.9 wt％、単層カーボンナノチューブ（ＳＷＣＮＴ）の含有量が 6.8～8.5 wt％の熱電材料の試料（厚み；4.5 μm）を製造し、ナノインデンテーション法（Nanoindentation）により硬度の測定を行った。また、比較のため、Bi2Te3薄膜（厚み；9.5 μm）についても、同様にして硬度を測定した。測定の結果、Ｐｔナノ粒子の含有量が0.9 wt％の試料は、硬度が0.67～0.73 GPaとなり、ビッカース硬度ＨＶに換算すると 39.2～42.0であった。また、Bi2Te3薄膜は、硬度が0.39 GPaとなり、ビッカース硬度ＨＶに換算すると 25.4であった。この結果から、単層カーボンナノチューブとＰｔナノ粒子とを加えることにより、熱電材料が硬くなることが確認された。 Similar to each sample in Table 1, a thermoelectric material sample (thickness; 4.5 μm) having a Pt nanoparticle content of 0.9 wt% and a single-walled carbon nanotube (SWCNT) content of 6.8 to 8.5 wt% was produced. Then, the hardness was measured by the nanoindentation method. For comparison, the hardness of the Bi 2 Te 3 thin film (thickness: 9.5 μm) was measured in the same manner. As a result of the measurement, the content of Pt nanoparticles 0.9 wt% of the samples, the hardness was from 39.2 to 42.0 in terms 0.67 ~ 0.73 GPa, and the Vickers hardness H V. Further, Bi 2 Te 3 thin film hardness was 25.4 in terms 0.39 GPa, and the Vickers hardness H V. From this result, it was confirmed that the thermoelectric material was hardened by adding the single-walled carbon nanotubes and Pt nanoparticles.
［比較例：Ｂｉ２Ｔｅ３にカーボンブラックを分散させた熱電材料、および、Ｂｉ２Ｔｅ３にカーボンナノチューブを分散させた熱電材料］
　熱電変換材料としてＢｉ２Ｔｅ３、炭素ナノ材料としてカーボンブラック粉末を用いて、表１の各試料と同様にして熱電材料を製造した。製造された熱電材料には、金属ナノ粒子は含まれていない。なお、カーボンブラックは、多孔質のケッチェンブラック（ライオン・スペシャリティ・ケミカルズ株式会社製「EC600JD」；多孔度　１３．７）を用いた。また、カーボンブラックは、ＰＤＤＡ（ポリジアリルジメチルアンモニウムクロライド）でコーティングしてから使用した。 Comparative Example: thermoelectric material in which carbon black is dispersed in the Bi 2 Te 3, and, thermoelectric material obtained by dispersing carbon nanotubes in Bi 2 Te 3]
Using Bi 2 Te 3 as the thermoelectric conversion material and carbon black powder as the carbon nanomaterial, the thermoelectric material was produced in the same manner as each sample in Table 1. The thermoelectric material produced does not contain metal nanoparticles. As the carbon black, porous Ketjen Black (“EC600JD” manufactured by Lion Specialty Chemicals Co., Ltd .; Porousness 13.7) was used. In addition, carbon black was used after being coated with PDDA (polydiallyldimethylammonium chloride).
　表２に示すように、熱電材料の熱電特性を測定するために、炭素（Ｃ）の含有量を変えた、３種類の試料（CB/Bi2Te3-I, II, III）を製造した。各試料は、それぞれ炭素の含有量が 3.4 wt％、3.7 wt％、4.3 wt％である。また、参考のため、表１のBi2Te3薄膜も、表２に示す。 As shown in Table 2, in order to measure the thermoelectric properties of the thermoelectric material, three types of samples (CB / Bi 2 Te 3- I, II, III) with different carbon (C) contents were prepared. .. Each sample has a carbon content of 3.4 wt%, 3.7 wt% and 4.3 wt%, respectively. For reference, the Bi 2 Te 3 thin films in Table 1 are also shown in Table 2.
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
　次に、熱電変換材料としてＢｉ２Ｔｅ３、炭素ナノ材料として単層カーボンナノチューブ（ＳＷＣＮＴ）または多層カーボンナノチューブ（ＭＷＣＮＴ）を用いて、表１の各試料と同様にして熱電材料を製造した。製造された熱電材料には、金属ナノ粒子は含まれていない。 Next, using Bi 2 Te 3 as the thermoelectric conversion material and single-walled carbon nanotubes (SWCNTs) or multi-walled carbon nanotubes (MWCNTs) as the carbon nanomaterials, thermoelectric materials were produced in the same manner as in each sample in Table 1. The thermoelectric material produced does not contain metal nanoparticles.
　表３に示すように、熱電材料の熱電特性を測定するために、炭素の含有量を変えた、それぞれ３種類の試料（SWCNTs/Bi2Te3-I, II, III、および、MWCNTs/Bi2Te3-I, II, III）を製造した。各試料は、それぞれ炭素の含有量が 3.8 wt％、4.1 wt％、4.4 wt％、3.6 wt％、4.1 wt％、4.8 wt％である。また、参考のため、表１のBi2Te3薄膜も、表３に示す。 As shown in Table 3, three types of samples (SWCNTs / Bi 2 Te 3- I, II, III, and MWCNTs / Bi) with different carbon contents were used to measure the thermoelectric properties of thermoelectric materials. 2 Te 3- I, II, III) was manufactured. Each sample has a carbon content of 3.8 wt%, 4.1 wt%, 4.4 wt%, 3.6 wt%, 4.1 wt% and 4.8 wt%, respectively. For reference, the Bi 2 Te 3 thin films in Table 1 are also shown in Table 3.
Figure JPOXMLDOC01-appb-T000003
Figure JPOXMLDOC01-appb-T000003
　製造した試料CB/Bi2Te3-I、および、Bi2Te3薄膜の走査型電子顕微鏡（ＳＥＭ）写真を、図４に示す。図４（ｂ）に示すように、カーボンブラックを加えた試料CB/Bi2Te3-Iは、図４（ａ）のBi2Te3薄膜と比べて、Bi2Te3の結晶が微細化していることが確認された。また、塊状のカーボンブラックは確認できないため、目視はできないが、Bi2Te3中にカーボンブラックが分散していると考えられる。 Scanning electron microscope (SEM) photographs of the produced samples CB / Bi 2 Te 3- I and Bi 2 Te 3 thin films are shown in FIG. As shown in FIG. 4 (b), in the sample CB / Bi 2 Te 3 -I to which carbon black was added, the crystals of Bi 2 Te 3 were finer than those in the Bi 2 Te 3 thin film of FIG. 4 (a). It was confirmed that In addition, since the lumpy carbon black cannot be confirmed, it cannot be visually observed, but it is considered that the carbon black is dispersed in Bi 2 Te 3 .
　製造した各試料のゼーベック係数（Seebeck coefficient）Ｓ、および、電気伝導度（Electrical conductivity）σを測定し、表２、表３、図５（ａ）および（ｂ）に示す。また、その測定結果から、各試料の出力因子（Power Factor；ＰＦ＝Ｓ２σ）を求め、表２、表３および図５（ｃ）に示す。また、いくつかの試料の熱伝導率（Thermal Conductivity）κを測定して、無次元性能指数ＺＴ（＝Ｓ２σＴ／κ）を求め、表２および表３に示す。 The Seebeck coefficient S and the electrical conductivity σ of each of the produced samples were measured and shown in Tables 2 and 3, FIGS. 5 (a) and 5 (b). Further, the power factor (PF = S 2 σ) of each sample was obtained from the measurement results, and is shown in Tables 2, 3 and 5 (c). In addition, the thermal conductivity κ of some samples was measured to obtain the dimensionless figure of merit ZT (= S 2 σT / κ), which are shown in Tables 2 and 3.
　表２、表３および図５（ｃ）に示すように、出力因子ＰＦは、カーボンブラックを加えた試料で約790～950 μW/m・K2であり、カーボンナノチューブを加えた試料よりも大きくなっていることが確認された。また、表２に示すように、無次元性能指数ＺＴは、カーボンブラックを加えた試料で 0.64であり、Bi2Te3薄膜よりも大きくなっていることが確認された。 As shown in Tables 2, 3 and 5 (c), the output factor PF is about 790 to 950 μW / m · K 2 in the sample to which carbon black is added, which is larger than that in the sample to which carbon nanotubes are added. It was confirmed that it was. Further, as shown in Table 2, it was confirmed that the dimensionless figure of merit ZT was 0.64 in the sample to which carbon black was added, which was larger than that of the Bi 2 Te 3 thin film.
　以上の結果から、Ｂｉ２Ｔｅ３にカーボンナノチューブとＰｔナノ粒子とを分散させた熱電材料（例えば、図２、図３参照）と、Ｂｉ２Ｔｅ３にカーボンブラックまたはカーボンナノチューブを分散させた熱電材料（例えば、図５参照）とを比べると、カーボンナノチューブとＰｔナノ粒子の両方を分散させた熱電材料は、それらの含有量を調整することにより、出力因子ＰＦが 1000 μW/m・K2以上、無次元性能指数ＺＴが 0.65以上となり、カーボンブラックおよびカーボンナノチューブのいずれか一方のみを加えた熱電材料よりも優れた熱電特性を得ることができるといえる。 From the above results, a thermoelectric material in which carbon nanotubes and Pt nanoparticles are dispersed in Bi 2 Te 3 (see, for example, FIGS. 2 and 3) and a thermoelectric material in which carbon black or carbon nanotubes are dispersed in Bi 2 Te 3 Compared with the materials (see, for example, FIG. 5), the thermoelectric material in which both carbon nanotubes and Pt nanoparticles are dispersed has an output factor PF of 1000 μW / m · K 2 by adjusting their contents. As described above, the dimensionless performance index ZT is 0.65 or more, and it can be said that excellent thermoelectric characteristics can be obtained as compared with the thermoelectric material to which only one of carbon black and carbon nanotube is added.

Claims (13)

  1. 　熱電変換材料と、１または複数の孔を有する炭素ナノ材料と、金属ナノ粒子とを含む複合材料から成ることを特徴とする熱電材料。 A thermoelectric material characterized by being composed of a thermoelectric conversion material, a carbon nanomaterial having one or more pores, and a composite material containing metal nanoparticles.
  2. 　前記炭素ナノ材料は、多孔質の炭素粒子および／またはカーボンナノチューブであることを特徴とする請求項１記載の熱電材料。 The thermoelectric material according to claim 1, wherein the carbon nanomaterial is a porous carbon particle and / or a carbon nanotube.
  3. 　前記炭素ナノ材料は、直径が２０ｎｍ以下の単層カーボンナノチューブから成ることを特徴とする請求項１または２記載の熱電材料。 The thermoelectric material according to claim 1 or 2, wherein the carbon nanomaterial is composed of single-walled carbon nanotubes having a diameter of 20 nm or less.
  4. 　前記炭素ナノ材料は、多孔度が８以上の多孔質の炭素粒子から成ることを特徴とする請求項１乃至３のいずれか１項に記載の熱電材料。 The thermoelectric material according to any one of claims 1 to 3, wherein the carbon nanomaterial is composed of porous carbon particles having a porosity of 8 or more.
  5. 　前記炭素ナノ材料は、粒子径が１００ｎｍ以下の多孔質のカーボンブラックから成ることを特徴とする請求項１乃至４のいずれか１項に記載の熱電材料。 The thermoelectric material according to any one of claims 1 to 4, wherein the carbon nanomaterial is made of a porous carbon black having a particle diameter of 100 nm or less.
  6. 　前記金属ナノ粒子は、Ｎｉ、Ｐｔ、Ａｇ、Ａｕ、Ｃｏ、Ｆｅ、ＣｕおよびＰｄのうちの少なくとも１つを含む粒子から成ることを特徴とする請求項１乃至５のいずれか１項に記載の熱電材料。 The method according to any one of claims 1 to 5, wherein the metal nanoparticles are composed of particles containing at least one of Ni, Pt, Ag, Au, Co, Fe, Cu and Pd. Thermoelectric material.
  7. 　前記金属ナノ粒子は、粒子径が５０ｎｍ以下であることを特徴とする請求項１乃至６のいずれか１項に記載の熱電材料。 The thermoelectric material according to any one of claims 1 to 6, wherein the metal nanoparticles have a particle diameter of 50 nm or less.
  8. 　前記炭素ナノ材料を６ｗｔ％乃至９ｗｔ％含み、前記金属ナノ粒子を０．５ｗｔ％乃至１ｗｔ％含むことを特徴とする請求項１乃至７のいずれか１項に記載の熱電材料。 The thermoelectric material according to any one of claims 1 to 7, wherein the carbon nanomaterial is contained in an amount of 6 wt% to 9 wt%, and the metal nanoparticles are contained in an amount of 0.5 wt% to 1 wt%.
  9. 　前記熱電変換材料は、被処理物の表面にメッキ処理可能な物質から成ることを特徴とする請求項１乃至８のいずれか１項に記載の熱電材料。 The thermoelectric material according to any one of claims 1 to 8, wherein the thermoelectric conversion material is made of a substance that can be plated on the surface of the object to be treated.
  10. 　前記熱電変換材料は、Ｂｉ、ＴｅおよびＳｂのうちの少なくとも２種類以上を含む物質であることを特徴とする請求項１乃至９のいずれか１項に記載の熱電材料。 The thermoelectric material according to any one of claims 1 to 9, wherein the thermoelectric conversion material is a substance containing at least two or more of Bi, Te and Sb.
  11. 　薄膜状であることを特徴とする請求項１乃至１０のいずれか１項に記載の熱電材料。 The thermoelectric material according to any one of claims 1 to 10, which is characterized in that it is in the form of a thin film.
  12. 　出力因子Ｓ２σ（ここで、Ｓはゼーベック係数、σは電気伝導度である）が１０００μＷ／ｍ・Ｋ２以上であることを特徴とする請求項１乃至１１のいずれか１項に記載の熱電材料。 The invention according to any one of claims 1 to 11, wherein the output factor S 2 σ (where S is a Seebeck coefficient and σ is an electrical conductivity) is 1000 μW / m · K 2 or more. Thermoelectric material.
  13. 　無次元性能指数ＺＴ（ここで、Ｚは性能指数、Ｔは絶対温度である）が０．６５以上であることを特徴とする請求項１乃至１２のいずれか１項に記載の熱電材料。
          The thermoelectric material according to any one of claims 1 to 12, wherein the dimensionless figure of merit ZT (where Z is a figure of merit and T is an absolute temperature) is 0.65 or more.
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