JP2010027895A - Thermoelectric conversion element - Google Patents

Thermoelectric conversion element Download PDF

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JP2010027895A
JP2010027895A JP2008188342A JP2008188342A JP2010027895A JP 2010027895 A JP2010027895 A JP 2010027895A JP 2008188342 A JP2008188342 A JP 2008188342A JP 2008188342 A JP2008188342 A JP 2008188342A JP 2010027895 A JP2010027895 A JP 2010027895A
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thermoelectric conversion
conversion element
metal
semiconductor
metal part
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Hiroaki Ando
浩明 安藤
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Konica Minolta Inc
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Abstract

<P>PROBLEM TO BE SOLVED: To provide a thermoelectric conversion element having flexibility and a high thermoelectric conversion capability by suppressing poor performance caused by stress damage, specifically, a thermoelectric conversion element which can suppress defects caused inside the element due to stress by providing the thermoelectric conversion element itself with a stress reducing capability. <P>SOLUTION: The thermoelectric conversion element includes a thermoelectric conversion semiconductor 13 and a metal portion 14 having a void ratio not less than 40 vol.% and not more than 99 vol.%. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

本発明は、ゼーベック効果等の熱電効果を用いた熱電変換素子に関するものである。   The present invention relates to a thermoelectric conversion element using a thermoelectric effect such as the Seebeck effect.

従来、デバイス内の温度差を利用した発電装置、デバイス内の局所冷却装置等として、熱電効果を利用した熱電変換素子が用いられている。熱電変換素子は、例えば、半導体等の熱電変換半導体の一方の端を加熱し、他方の端を冷却することによって、熱電変換半導体内に温度勾配を生じさせ、熱電効果によって熱電変換半導体の低温端と高温端との間に得られる電位差により、熱起電力を発生させるものである。   Conventionally, a thermoelectric conversion element using a thermoelectric effect has been used as a power generation device using a temperature difference in a device, a local cooling device in a device, or the like. The thermoelectric conversion element, for example, heats one end of a thermoelectric conversion semiconductor such as a semiconductor and cools the other end, thereby generating a temperature gradient in the thermoelectric conversion semiconductor, and the thermoelectric effect causes a low temperature end of the thermoelectric conversion semiconductor. The thermoelectromotive force is generated by the potential difference obtained between the high temperature end and the high temperature end.

このような熱電変換素子は、高温側の基板と低温側の基板との間に熱電素子が配置された構造、いわゆるπ型構造を採るのが一般的である。熱電変換素子は、大きな起電力を得るために、高温側と低温側に大きな温度差を与えることが必要なため、片側でのみ熱膨張が起き、大きな内部応力が発生しやすい。高温側からの熱供給が止まり温度差がなくなると内部応力もなくなるが、この繰り返しは熱電変換素子に機械的ダメージを与え、起電力低下の原因になる。さらに、熱電変換素子を曲げる必要のある使用条件下では、ダメージがより発生し易く、それに十分に耐えるような技術は、現時点では存在しない。特に、素子と電極の接合部、あるいは素子自体がダメージを受けやすい。電極と熱電変換半導体間にバネや応力緩和層を設ける方法が開示されている(例えば、特許文献1、2参照。)。これら開示されている方法は、上記課題に対してある程度の効果を発揮するものの、例えば、曲げに対してその緩和層だけでダメージを回避することは実際には困難で、ダメージを受けにくく十分な性能を発揮する熱電変換素子を得ることはできなかった。
特開平10−111368号公報 特開2007−116087号公報
Such a thermoelectric conversion element generally adopts a so-called π-type structure in which a thermoelectric element is arranged between a high temperature side substrate and a low temperature side substrate. In order to obtain a large electromotive force, the thermoelectric conversion element needs to give a large temperature difference between the high temperature side and the low temperature side. Therefore, thermal expansion occurs only on one side, and large internal stress tends to occur. When the supply of heat from the high temperature side stops and the temperature difference disappears, the internal stress also disappears, but this repetition causes mechanical damage to the thermoelectric conversion element and causes a reduction in electromotive force. Furthermore, there is currently no technology that can easily damage and sufficiently withstand the use conditions in which the thermoelectric conversion element needs to be bent. In particular, the junction between the element and the electrode or the element itself is easily damaged. A method of providing a spring or a stress relaxation layer between an electrode and a thermoelectric conversion semiconductor is disclosed (for example, refer to Patent Documents 1 and 2). Although these disclosed methods exhibit a certain degree of effect on the above-mentioned problems, for example, it is actually difficult to avoid damage with only the relaxation layer against bending, and it is difficult to receive damage and is sufficient. A thermoelectric conversion element exhibiting performance could not be obtained.
Japanese Patent Laid-Open No. 10-111368 JP 2007-116087 A

本発明は、上記課題に鑑みなされたものであり、その目的は、応力ダメージによって生ずる性能不良を抑制し、可撓性(フレキシビリティ)と高い熱電変換能力を有する熱電変換素子を提供することを目的とする。特に、熱電変換素子自体に応力緩和能を付与することによって、応力によって素子内に生ずる不良を抑制することが可能な熱電変換素子を提供することにある。   This invention is made | formed in view of the said subject, The objective is suppressing the performance defect which arises by stress damage, and providing the thermoelectric conversion element which has flexibility (flexibility) and high thermoelectric conversion capability. Objective. In particular, it is an object of the present invention to provide a thermoelectric conversion element that can suppress defects caused in the element due to stress by imparting stress relaxation capability to the thermoelectric conversion element itself.

本発明の上記目的は、以下の構成により達成される。   The above object of the present invention is achieved by the following configurations.

1.熱電変換半導体及び、40体積%以上99体積%以下の空隙率を有する金属部が含有されていることを特徴とする熱電変換素子。   1. A thermoelectric conversion element comprising a thermoelectric conversion semiconductor and a metal part having a porosity of 40% by volume to 99% by volume.

2.前記熱電変換半導体及び前記空隙率を有する金属部が、一対の電極に挟持されていることを特徴とする前記1に記載の熱電変換素子。   2. 2. The thermoelectric conversion element according to 1 above, wherein the thermoelectric conversion semiconductor and the metal portion having the porosity are sandwiched between a pair of electrodes.

3.前記空隙率を有する金属部が、100W/m・K以上の熱伝導率を有する金属からなることを特徴とする前記1または2に記載の熱電変換素子。   3. 3. The thermoelectric conversion element according to 1 or 2, wherein the metal part having the porosity is made of a metal having a thermal conductivity of 100 W / m · K or more.

4.金属部が、アスペクト比が5.0以上である金属粒子の集合体であることを特徴とする前記1〜3のいずれか1項に記載の熱電変換素子。   4). 4. The thermoelectric conversion element according to any one of 1 to 3, wherein the metal part is an aggregate of metal particles having an aspect ratio of 5.0 or more.

5.前記空隙率を有する金属部が、層状の熱電変換半導体に積層された構造であることを特徴とする前記1〜4のいずれか1項に記載の熱電変換素子。   5. 5. The thermoelectric conversion element according to any one of 1 to 4, wherein the metal portion having the porosity is a structure laminated on a layered thermoelectric conversion semiconductor.

本発明により、応力ダメージによって生ずる性能不良を抑制し、可撓性(フレキシビリティー)と高い熱電変換能力を有し、特に、熱電変換素子自体に応力緩和能を付与することによって、応力によって素子内に生ずる不良を抑制することが可能な熱電変換素子を提供することができた。   According to the present invention, poor performance caused by stress damage can be suppressed, and flexibility and flexibility can be obtained. In particular, by providing stress relaxation capability to the thermoelectric conversion element itself, the element can be controlled by stress. The thermoelectric conversion element which can suppress the defect which arises inside was able to be provided.

以下、本発明を実施するための最良の形態について詳細に説明する。   Hereinafter, the best mode for carrying out the present invention will be described in detail.

本発明者は、上記課題に鑑み鋭意検討を行った結果、熱電変換半導体及び、40体積%以上99体積%以下の空隙率を有する金属部が含有されている特徴とする熱電変換素子により、応力ダメージによって生ずる性能不良を抑制し、可撓性(フレキシビリティー)と高い熱電変換能力を有する熱電変換素子を実現できることを見出し、本発明に至った次第である。   As a result of intensive studies in view of the above problems, the present inventor has found that a thermoelectric conversion semiconductor and a thermoelectric conversion element including a metal part having a porosity of 40% by volume or more and 99% by volume or less contain stress. As soon as the present invention has been found, it has been found that a thermoelectric conversion element that suppresses poor performance caused by damage and has flexibility (flexibility) and high thermoelectric conversion capability can be realized.

以下、本発明の熱電変換素子の詳細について説明する。   Hereinafter, the details of the thermoelectric conversion element of the present invention will be described.

〔熱電変換素子の構成〕
本発明の熱電変化素子の構成について図を用いて説明する。なお、以下の図に示す熱電変換素子は、本発明の熱電変化素子の一例を示すものであり、本発明はここで例示する構成にのみ限定されるものではない。
[Configuration of thermoelectric conversion element]
The structure of the thermoelectric change element of this invention is demonstrated using figures. In addition, the thermoelectric conversion element shown in the following figures shows an example of the thermoelectric change element of this invention, and this invention is not limited only to the structure illustrated here.

図1は、本発明の熱電変換素子の構成の一例を示す概略断面図である。   FIG. 1 is a schematic cross-sectional view showing an example of the configuration of the thermoelectric conversion element of the present invention.

図1に示す熱電変換素子10においては、説明の便宜上、電極と金属部、半導体の部分のみ図示し、絶縁性の基板を省略している。なお、文中の熱電変換半導体は、後述するとおり、温度差が与えられたとき、大きな起電力を生じる半導体(例えば、Bi−Te系化合物など)を指す。   In the thermoelectric conversion element 10 shown in FIG. 1, for convenience of explanation, only the electrode, metal part, and semiconductor part are shown, and the insulating substrate is omitted. In addition, the thermoelectric conversion semiconductor in a sentence points out the semiconductor (for example, Bi-Te type compound etc.) which produces a big electromotive force when a temperature difference is given so that it may mention later.

図1のa)に示す熱電変換素子10では、対向する電極11、12の間に狭持された熱電変換半導体(以下、単に熱電半導体、半導体ともいう)13中に、空隙を有する金属部14が非連続的に存在している。空隙を有する金属部14は、熱電変換素子に掛かる応力を軽減、分散する働きを有する。空隙が存在しないと、金属部と半導体部に掛かる応力の分散や軽減がなされないため、最も弱い部分、例えば電極と半導体の接合部分などに破壊が生じ、電気、熱抵抗の上昇、起電力低下の原因になる。   In the thermoelectric conversion element 10 shown in FIG. 1 a), a metal part 14 having a gap in a thermoelectric conversion semiconductor 13 (hereinafter also simply referred to as a thermoelectric semiconductor or semiconductor) sandwiched between opposing electrodes 11 and 12. Exist discontinuously. The metal part 14 having a void has a function of reducing and dispersing stress applied to the thermoelectric conversion element. If there are no air gaps, the stress applied to the metal part and the semiconductor part will not be distributed or reduced, so the weakest part, for example, the joint part of the electrode and semiconductor, will break down, increasing the electrical and thermal resistance, reducing the electromotive force Cause.

空隙を有する金属部の含有量は、可撓性向上には多いほど好ましいが、多すぎると空隙を有する金属部が熱電変換素子内に連続的に電気伝導路を形成するように存在することになり、電極間に短絡回路が生じるため起電力が得られない。すなわち、電気伝導路を形成しない程度に、素子に加わった応力を緩和する量の空隙を有するように変換素子内に分布、存在していることが好ましい。この場合、空隙を有する金属部の含有量の最適値は、電極間の電気抵抗値を測定することで決定され、金属部の含有量増加で抵抗値が急激に低下すなわちパーコレーションによる導電性発現量より若干少ない量が最も好ましい。   The content of the metal part having voids is preferably as much as possible for improving flexibility. However, if the content is too large, the metal part having voids is present so as to continuously form an electric conduction path in the thermoelectric conversion element. Therefore, since a short circuit occurs between the electrodes, no electromotive force can be obtained. That is, it is preferably distributed and present in the conversion element so as to have a void of an amount that relaxes the stress applied to the element to such an extent that an electric conduction path is not formed. In this case, the optimum value of the content of the metal part having voids is determined by measuring the electrical resistance value between the electrodes, and the resistance value rapidly decreases as the content of the metal part increases, that is, the amount of conductivity developed by percolation. A slightly smaller amount is most preferred.

図1のb)に示す熱電変換素子20においては、対向する電極にそれぞれ接して離間した位置にある一対の熱電変換半導体13、13′の層間に空隙を有する金属部14が含有され、3層の構成を採った例を示してある。図1のb)に示す例では、電極間11、12を短絡しないよう、半導体層中に空隙を有する金属部14の層を形成することで、可撓性を付与するための金属層14をより多く導入することができる。金属部14の含有量は多いほど好ましいが、空隙による熱伝導、電気伝導に悪影響の出るレベル以下が好ましい。実際には、空隙を有する金属層の厚みを変化させながら、熱電変換素子の熱電変換効率を評価し、悪影響が出るより若干少なくすることが好ましい。   The thermoelectric conversion element 20 shown in FIG. 1 b includes a metal part 14 having a gap between a pair of thermoelectric conversion semiconductors 13, 13 ′ that are in contact with and spaced apart from opposing electrodes, and includes three layers. The example which took the structure of is shown. In the example shown in FIG. 1 b), the metal layer 14 for imparting flexibility is formed by forming a layer of the metal part 14 having a gap in the semiconductor layer so as not to short-circuit the electrodes 11 and 12. More can be introduced. Although the content of the metal part 14 is preferably as high as possible, it is preferably below a level that adversely affects the heat conduction and electrical conduction by the air gap. Actually, the thermoelectric conversion efficiency of the thermoelectric conversion element is evaluated while changing the thickness of the metal layer having voids, and it is preferable to reduce the thickness slightly to avoid adverse effects.

図1のc)に示す熱電変換素子10では、熱電変換半導体13、13′からなる層間だけでなく、電極11、12と熱電変換半導体13、13′の層間にも空隙を有する金属部14が含有されている5層積層した例を示してある。そのため基板(不図示)が曲がったときの応力が直接熱電変換半導体に伝わることが無いので、応力起因のダメージ抑制効果がより高まる。各層の厚みは図1のb)の例と同様に、その量を変化させながら熱電変換素子の熱電変換能を測定し、厚みが大きすぎることによる悪影響が出始める厚みより若干薄くすることが好ましい。これらの例で、悪影響の出始める金属層の厚みは、半導体の材料、金属材料により異なるため一概に判断することはできないが、実験的に求めることは容易である。   In the thermoelectric conversion element 10 shown in FIG. 1 c), the metal part 14 having a gap not only between the layers made of the thermoelectric conversion semiconductors 13 and 13 ′ but also between the electrodes 11 and 12 and the thermoelectric conversion semiconductors 13 and 13 ′ An example in which five layers contained are laminated is shown. Therefore, since the stress when the substrate (not shown) is bent is not directly transmitted to the thermoelectric conversion semiconductor, the effect of suppressing the stress-induced damage is further increased. As in the example of b) of FIG. 1, the thickness of each layer is preferably slightly smaller than the thickness at which the thermoelectric conversion ability of the thermoelectric conversion element is measured while changing the amount thereof and the adverse effect due to the thickness being too large starts to appear. . In these examples, the thickness of the metal layer that starts to have an adverse effect differs depending on the semiconductor material and the metal material, and thus cannot be determined unconditionally, but it is easy to obtain experimentally.

〔空隙を有する金属部の作製〕
空隙を有する金属部は、金属中に十分な量で形状変動可能な大きな空隙を、空隙率として40体積%以上、99体積%以下有することを特徴とする。空隙は、いわゆる結晶中のポア(結晶粒界の欠損部)とは異なり、電子顕微鏡等で容易に観察可能な10nm以上の金属非存在部である。金属部中の空隙量は、見かけ体積と実質量から容易に計算可能である。熱電変換半導体と複合化されている場合でも、半導体の体積、質量を含めた上記計算により、空隙率を容易に算出することができる。
[Production of metal part having voids]
The metal part having voids is characterized by having a large void that can change its shape in a sufficient amount in the metal as a porosity of 40% by volume to 99% by volume. Unlike so-called pores (defects at grain boundaries), the voids are 10 nm or more metal nonexistent portions that can be easily observed with an electron microscope or the like. The void amount in the metal part can be easily calculated from the apparent volume and the substantial amount. Even when it is combined with a thermoelectric conversion semiconductor, the porosity can be easily calculated by the above calculation including the volume and mass of the semiconductor.

本発明に係る空隙を有する金属部は、それぞれ適当な空隙を有することにより可撓性を有すると共に、十分な熱伝導性、電気伝導性を有することが必要である。空隙中には空気が充満されていても良いし、不活性ガスが充填されていても良い。また、真空であっても良い。あるいは、可撓性の高い樹脂が含浸されていることも好ましい。なお樹脂は変換素子の電気伝導、熱伝導に大きな寄与を及ぼさないので、その充填体積は空隙として扱う。   The metal part having voids according to the present invention needs to have sufficient thermal conductivity and electrical conductivity as well as flexibility by having appropriate voids. The gap may be filled with air or may be filled with an inert gas. Moreover, a vacuum may be sufficient. Or it is also preferable that highly flexible resin is impregnated. Since resin does not greatly contribute to the electrical conduction and heat conduction of the conversion element, the filling volume is treated as a void.

本発明においては、空隙は金属部の40体積%以上、99体積%以下が必要である。より好ましくは、60体積%以上、90体積%以下である。金属部の空隙量が少ないと、金属部の可撓性が下がるため、熱電変換素子への応力緩和機能が低下し、空隙量が多すぎると、応力緩和能があっても電気伝導性が下がり、熱伝導性も下がり、熱電変換効率の低下が著しくなるためである。   In the present invention, the gap needs to be 40 volume% or more and 99 volume% or less of the metal part. More preferably, they are 60 volume% or more and 90 volume% or less. If the amount of voids in the metal part is small, the flexibility of the metal part is lowered, so the stress relaxation function to the thermoelectric conversion element is reduced. If the amount of voids is too large, the electrical conductivity is lowered even if there is stress relaxation capability. This is because the thermal conductivity is lowered and the thermoelectric conversion efficiency is remarkably lowered.

空隙を有する金属部の形態として、内部に無数の微小な空孔を有する多孔性の金属体、金属箔あるいは繊維のランダムな集合物、あるいは配向した集合物を用いることが可能である。多孔質の金属体は、溶融金属中にガスを導入しながら冷却する方法、微小な金属粒子を焼成する方法等で得ることができる。この時、空隙の形状は一定ではなく、金属部の原料部材によって異なる。   As the form of the metal part having voids, it is possible to use a porous metal body having countless minute pores inside, a random aggregate of metal foils or fibers, or an aligned aggregate. The porous metal body can be obtained by a method of cooling while introducing a gas into the molten metal, a method of firing minute metal particles, or the like. At this time, the shape of the gap is not constant and varies depending on the raw material member of the metal part.

金属箔あるいは繊維を金属部の原料として用いる場合、箔ないし繊維のアスペクト比(本発明でいうアスペクト比とは、個々の粒子の長軸と短軸の長さ比の平均値)が5以上の粒子を用い、それらを空隙を残したまま一体化し、金属部を形成すると、好ましい特性の得られる。特に、アスペクト比が10以上である金属粒子を用いることが好ましく、更にアスペクト比が30以上であることが好ましい。   When a metal foil or fiber is used as a raw material for the metal part, the aspect ratio of the foil or fiber (the aspect ratio in the present invention is the average value of the length ratio between the major axis and the minor axis of each particle) is 5 or more. When particles are used and they are integrated while leaving voids to form a metal part, favorable characteristics can be obtained. In particular, it is preferable to use metal particles having an aspect ratio of 10 or more, and it is more preferable that the aspect ratio is 30 or more.

粒子形状は、直線的な結晶であるウィスカー、曲線的な形状を有するワイヤー状、カールを有するあるいは有さない薄片状、箔(フォイル)状などどのような形状でもよい。アスペクト比の大きい粒子を用いて金属部を構成すると、粒子同士の接点の数が少ないため、可撓性を保てると同時に、応力が加わっても高い電気、熱伝導性を維持し易く、好ましい特性が得られると考えられる。   The particle shape may be any shape such as whisker that is a linear crystal, a wire shape having a curvilinear shape, a flake shape with or without a curl, and a foil shape. When the metal part is composed of particles having a large aspect ratio, the number of contact points between the particles is small, so that flexibility can be maintained, and at the same time, high electrical and thermal conductivity can be easily maintained even when stress is applied, which is a desirable characteristic. Can be obtained.

短軸の長さ(厚み)は1μm以下であることが好ましい。更に好ましくは500nm以下である。この理由は、短軸の長さ(厚み)の小さな粒子は、比表面積が大きいと共に、個々の粒子間の相互作用(一種の凝集力)が強いため、高い温度で焼成しなくても一体化でき、金属部に可撓性と電気伝導性、熱伝導性を付与できるためである。さらに、アスペクト比が大きく厚みが薄い粒子は個々の粒子が変形しやすいと同時に、電極や半導体との接点にかかる応力が弱く、破壊が進みにくい。そのため、短軸の長さ(厚み)の小さいことが好ましい。長さ(厚み)が極端に小さい(1nm以下)の場合は、金属部の熱抵抗が急激に増大するため好ましくないが、その下限は金属の材質により異なるので、実験的に悪影響が無いよう定める。   The length (thickness) of the short axis is preferably 1 μm or less. More preferably, it is 500 nm or less. This is because particles with a short minor axis length (thickness) have a large specific surface area and strong interaction between individual particles (a kind of cohesive force), so they can be integrated without firing at high temperatures. This is because flexibility, electrical conductivity, and thermal conductivity can be imparted to the metal portion. Further, particles having a large aspect ratio and a small thickness are likely to be deformed individually, and at the same time, the stress applied to the contact point with the electrode or the semiconductor is weak, and the breakage does not easily proceed. Therefore, it is preferable that the length (thickness) of the short axis is small. When the length (thickness) is extremely small (1 nm or less), the thermal resistance of the metal part increases rapidly, which is not preferable. .

図2は、高アスペクト比の金属粒子を含有した空隙を有する金属部を有する熱電変換素子の一例を示す概略断面図である。   FIG. 2 is a schematic cross-sectional view showing an example of a thermoelectric conversion element having a metal part having a void containing metal particles having a high aspect ratio.

図2は、先に説明した図1のb)に示した3層積層構造の熱電変換素子の金属部14に高アスペクト比粒子を存在させた例を示してある。   FIG. 2 shows an example in which high aspect ratio particles are present in the metal portion 14 of the thermoelectric conversion element having the three-layer structure shown in FIG.

図2のa)は、金属部14中に、金属粒子の長軸を金属部の層に垂直に配向させた高アスペクト比のウィスカー状金属粒子15を存在させた一例である。   FIG. 2A shows an example in which whisker-like metal particles 15 having a high aspect ratio in which the major axis of the metal particles is oriented perpendicularly to the layer of the metal part are present in the metal part 14.

図2のb)は、金属部14中に、金属粒子の長軸を金属部の層に平行に配向させた高アスペクト比のワイヤー状金属粒子16を存在させた一例である。   FIG. 2 b) is an example in which high-aspect-ratio wire-like metal particles 16 in which the long axes of the metal particles are oriented parallel to the metal part layer are present in the metal part 14.

図2のc)は、金属部14中に、金属粒子の長軸を金属部の層に垂直に配向させた高アスペクト比の薄片状金属粒子17を存在させた一例で、この様な構成とすることにより、効率よく伝熱することが可能である。   FIG. 2 c) is an example in which the high-aspect-ratio flaky metal particles 17 in which the long axes of the metal particles are oriented perpendicularly to the metal part layer are present in the metal part 14. By doing so, it is possible to conduct heat efficiently.

図2のd)は、金属部14中に、金属粒子の長軸を金属部の層に平行に配向させた高アスペクト比の箔(フォイル)状金属粒子18を存在させた一例である。   FIG. 2 d) shows an example in which high aspect ratio foil-shaped metal particles 18 in which the long axes of the metal particles are oriented parallel to the metal portion layer are present in the metal portion 14.

この様な高アスペクト比粒子を含有する金属部を有することにより、効率よく伝熱することが可能で、これらの粒子は電気伝導性、熱伝導性が半導体に比して十分大きいので、金属部が可撓性を維持し、必要な応力に耐えられるような構造となっている限りは、図2のa)〜d)に示すいずれの構造をとることも可能である。   By having such a metal part containing high aspect ratio particles, it is possible to transfer heat efficiently. Since these particles have sufficiently large electric conductivity and heat conductivity as compared with semiconductors, the metal part Any of the structures shown in a) to d) of FIG. 2 can be adopted as long as the structure maintains flexibility and can withstand necessary stress.

金属部に適当な割合で空隙を含有させたまま一体化する方法として、金属粒子のプレスが挙げられる。アスペクト比の大きな粒子を用いる場合には、単にプレスだけで金属粒子の一体化が可能である。その観点より、特にワイヤー状の粒子は好適である。また、プレスだけでは一体化しにくい場合、焼成することも好ましい。焼成においては、樹脂等に混練した後に焼成し、空隙を残したまま金属のみをとり出す方法、金属の原料となる金属塩を含有する有機物中で還元反応により細線状の金属を作製した後、無機物を洗浄除去して焼成する方法など、各種の方法をとることができる。これらのうち、適当な方法を選択、組み合わせることも可能であると共に、その他の作製方法も適用可能である。   An example of a method of integrating the metal part with voids contained in an appropriate ratio is a press of metal particles. When particles having a large aspect ratio are used, the metal particles can be integrated simply by pressing. From this point of view, wire-like particles are particularly suitable. Moreover, when it is difficult to integrate only with a press, baking is also preferable. In firing, after kneading into a resin or the like, firing, a method of taking out only the metal leaving a void, after producing a thin wire metal by a reduction reaction in an organic substance containing a metal salt as a metal raw material, Various methods such as a method of washing and removing inorganic substances can be employed. Among these, appropriate methods can be selected and combined, and other manufacturing methods are also applicable.

〔金属部と半導体の界面〕
金属部と熱電変換半導体との界面は、電気抵抗や熱抵抗が生じないように接合している必要がある。そのため、一体化後にある程度加熱して焼成することが好ましい。また金属層の半導体との界面には、若干量のNiやCr、Moなど、接着性を向上するような金属を存在させることも好ましい。これらの金属原子は、無電解めっきや蒸着などで金属部に含有させる方法、同様に半導体に含有させる方法、両方を併用することも可能である。
[Interface between metal part and semiconductor]
The interface between the metal part and the thermoelectric conversion semiconductor needs to be joined so that electric resistance and thermal resistance do not occur. For this reason, it is preferable to perform baking after heating to some extent after integration. It is also preferable that a slight amount of metal, such as Ni, Cr, or Mo, that improves adhesion is present at the interface of the metal layer with the semiconductor. These metal atoms can be used in combination with a method for containing them in the metal part by electroless plating or vapor deposition, or a method for containing them in the semiconductor as well.

熱電変換素子内で、電気抵抗や熱抵抗が存在すると、熱電変換効率が低下する。例えば電気抵抗や熱抵抗による熱電変換能は、下記の式(1)、(2)のように変動する。   If electric resistance or thermal resistance exists in the thermoelectric conversion element, the thermoelectric conversion efficiency is lowered. For example, the thermoelectric conversion ability due to electric resistance or thermal resistance varies as in the following formulas (1) and (2).

式(1)
ΔTeff=ΔT/(1+4・Rth(κ/L))
式(2)
P=(S・ΔTeff/4・A/(ρ+4ρ
式(1)において、Rthは界面熱抵抗を表し、Lは熱電変換素子の長さ(膜厚)を表す。式(2)において、ρは抵抗率を表し、ρはコンタクト抵抗を表す。
Formula (1)
ΔT eff = ΔT / (1 + 4 · R th (κ / L))
Formula (2)
P = (S · ΔT eff) 2/4 · A / (ρ B + 4ρ C)
In Formula (1), Rth represents interfacial thermal resistance, and L represents the length (film thickness) of the thermoelectric conversion element. In equation (2), ρ B represents resistivity and ρ C represents contact resistance.

上記式(1)、(2)から分かるように、電気抵抗や界面熱抵抗は、変換効率を低くする。金属部の熱抵抗が大きいと、特に、熱電変換素子が図1のa)、b)に示す構造を有する場合には、半導体の有効温度差が小さくなるため変換効率が低下する。これに対し、比表面積の大きな粒子を用いた金属部は、半導体部との接触面積を大きくし、上記のような電気抵抗、界面熱抵抗を低減するのにも有効である。   As can be seen from the above formulas (1) and (2), the electrical resistance and the interfacial thermal resistance lower the conversion efficiency. When the thermal resistance of the metal part is large, particularly when the thermoelectric conversion element has the structure shown in FIGS. 1A and 1B, the effective temperature difference of the semiconductor becomes small, so that the conversion efficiency is lowered. On the other hand, the metal part using particles having a large specific surface area is effective in increasing the contact area with the semiconductor part and reducing the electrical resistance and interfacial thermal resistance as described above.

〔金属部をなす金属種の選択〕
金属部には高熱伝導材料を用いることで、熱電変換効率の向上が期待できるため、100W/m・K以上の熱伝導率を有する金属に空隙を付与して用いることが好ましい。例えば、Bi−Te系の半導体では、熱伝導率が2W/m・Kであるため、このような高い熱伝導率を有する金属であれば、ある程度空隙を有していても半導体に比して十分に高い熱伝導率を有することができる。
[Selection of metal species to form the metal part]
Since the use of a high thermal conductive material for the metal portion can improve the thermoelectric conversion efficiency, it is preferable to use a metal having a thermal conductivity of 100 W / m · K or more with voids. For example, a Bi-Te-based semiconductor has a thermal conductivity of 2 W / m · K. Therefore, a metal having such a high thermal conductivity has a certain amount of voids compared to a semiconductor. It can have a sufficiently high thermal conductivity.

100W/m・kの熱伝導率を有する金属は、例えば、2007理科年表に記載のデータから選択することができる。使用温度領域により熱伝導率は異なるが、亜鉛、アルミニウム、イリジウム、カリウム、金、銀、タングステン、銅、ベリリウム、マグネシウム、モリブデン等およびこれらを含有する合金は、通常100W/m・Kの熱伝導率を有するため好ましい。更には、200W/m・Kの熱伝導率を有する、アルミニウム、金、銀、銅、ベリリウム等およびこれらを含有する合金が好ましい。合金化で熱伝導率が低下する場合があるが、長期使用において問題になるマイグレーションの抑制や、耐腐食性、加工性の向上には、合金化は有利である。銀であれば若干のパラジウムと合金化し、銅であれば若干量のTeやCdと合金化することがこれにあたる。   The metal having a thermal conductivity of 100 W / m · k can be selected from, for example, data described in the 2007 science chronology. Although the thermal conductivity varies depending on the operating temperature range, zinc, aluminum, iridium, potassium, gold, silver, tungsten, copper, beryllium, magnesium, molybdenum, and alloys containing these are usually 100 W / m · K in thermal conductivity. It is preferable because it has a ratio. Furthermore, aluminum, gold | metal | money, silver, copper, beryllium etc. which have a thermal conductivity of 200 W / m * K, and an alloy containing these are preferable. Although the thermal conductivity may decrease due to alloying, alloying is advantageous for suppressing migration, which is a problem in long-term use, and for improving corrosion resistance and workability. In the case of silver, it is alloyed with a little palladium, and in the case of copper, it is alloyed with a little amount of Te or Cd.

金属ではないが、いわゆる金属性の単層カーボンナノチューブ(SWCNT)は、金属同等の導電性有し、本発明で使用可能である。金属性のSWCNTはアームチェア型単層カーボンナノチューブを主成分とするSWCNTである。   Although it is not a metal, so-called metallic single-walled carbon nanotubes (SWCNT) have conductivity equivalent to that of metal and can be used in the present invention. The metallic SWCNT is SWCNT mainly composed of an armchair type single-walled carbon nanotube.

〔熱電変換半導体の選択〕
金属部と共に変換素子をなす熱電変換半導体の種類としては、ビスマス−テルル系の半導体のほか、Si−Ge系の半導体、Pb−Te系の半導体などが適用可能である。その他、充填スクッテルダイト化合物、ホウ素化合物、亜鉛アンチモン、クラスレート、擬ギャップ系ホイスラー花化合物などがある。これら半導体の詳細については、例えば、「熱電変換システムの高効率化・高信頼化技術」(2006年、技術情報協会)等の記載を参考にできる。
[Selection of thermoelectric conversion semiconductor]
As the type of thermoelectric conversion semiconductor that forms the conversion element together with the metal part, in addition to a bismuth-tellurium-based semiconductor, a Si-Ge-based semiconductor, a Pb-Te-based semiconductor, or the like is applicable. In addition, there are filled skutterudite compounds, boron compounds, zinc antimony, clathrates, pseudogap-type Heusler flower compounds, and the like. Details of these semiconductors can be referred to, for example, the description of “Technology for improving efficiency and reliability of thermoelectric conversion systems” (2006, Technical Information Association).

これら半導体は、元の材料に、p型、n型半導体としての性質を付与するためのドーパントが添加されている。ドーパントを添加した後に、強熱、焼成を行うと、ドーパントの含有状態が半導体内部で不均一化し、周囲の不純物の悪影響を受ける原因になるため、必要以上の加熱は好ましくない。金属部との接合あるいは一体化において、ある程度の焼成が必要な場合、比表面積の大きな高アスペクト比粒子からなる金属部は、その焼成温度を下げられるため、この観点からも好ましい。   In these semiconductors, a dopant for imparting properties as p-type and n-type semiconductors is added to the original material. If high heat and baking are performed after the dopant is added, the content of the dopant becomes non-uniform inside the semiconductor and is adversely affected by surrounding impurities. In a case where a certain degree of firing is required for joining or integration with the metal part, a metal part made of high aspect ratio particles having a large specific surface area is preferable from this viewpoint because the firing temperature can be lowered.

〔熱電変換素子の作製方法〕
本発明の熱電変換素子の具体的な作製における半導体膜の作製方法としては、下記に示す方法を一例として挙げられる。
[Method for producing thermoelectric conversion element]
As a method for manufacturing a semiconductor film in the specific manufacturing of the thermoelectric conversion element of the present invention, the following method can be given as an example.

1)グリーンシートを用いた半導体前駆体のパターニング、焼成(有機物の除去、半導体の結晶化)
2)蒸着、スパッタ(マスクパターニング、半導体の蒸着膜を作成と金属層設置の複層化)
3)Bi−Te系材料では、急冷薄片の焼結結晶化、ないし結晶成長により作成した結晶からの切り出し
その後に焼成が必要な場合には、遠心焼成、擬HIP等の焼成方法を用いることもでき、これらにより、半導体結晶を緻密にし、高性能とすることができる。
1) Patterning and firing of semiconductor precursor using green sheet (removal of organic substances, crystallization of semiconductor)
2) Vapor deposition, sputtering (mask patterning, creation of a semiconductor vapor deposition film and multiple layers of metal layers)
3) For Bi-Te-based materials, a sintered method such as centrifugal firing or pseudo-HIP may be used if firing is necessary after sintering and crystallization of rapidly cooled flakes or from crystal growth. Thus, the semiconductor crystal can be made dense and have high performance.

電極は、一般的な金属電極が使用可能である。アルミニウムや銅、金、銀、などのほか、半田、グラファイトなども適用可能である。半導体層を空隙を有する金属部で挟む構造をとる場合は、その金属部を電極として用いることが可能なので、必ずしも別に電極を設ける必要は無い。   As the electrode, a general metal electrode can be used. In addition to aluminum, copper, gold, silver, etc., solder, graphite, etc. are also applicable. In the case where the semiconductor layer is sandwiched between metal portions having voids, the metal portion can be used as an electrode, and thus it is not always necessary to provide another electrode.

発電用のモジュール化には、p型とn型の半導体を含んだ素子を直列に接続した、いわゆる「π型素子」とすることが望ましい。π型素子では、吸熱側と放熱側をそれぞれ熱源、冷却源に対して有効に配置でき、発電効率を高め易いためである。また、本発明ではp型、n型半導体の少なくとも1つに半導体層と空隙を有する金属部が含有されていれば良いが、可撓性をより高めるためにp型、n型半導体両方に半導体層と空隙を有する金属部が含有されていることがより好ましい。   For power generation modularization, it is desirable to use a so-called “π-type element” in which elements including p-type and n-type semiconductors are connected in series. This is because in the π-type element, the heat absorption side and the heat dissipation side can be effectively arranged with respect to the heat source and the cooling source, respectively, and the power generation efficiency is easily improved. In the present invention, at least one of the p-type and n-type semiconductors only needs to contain a semiconductor layer and a metal part having a void. However, in order to increase flexibility, both the p-type and n-type semiconductors are made of semiconductor. It is more preferable that the metal part which has a layer and a space | gap is contained.

本発明では、π型素子を電気的に直列に接続したモジュールの可撓性が向上するため、曲面上の発熱体に貼り付けるといった、これまでに無い使用法が可能になる。例えば、蒸気配管、焼却炉、衣類といったこれまで単に廃熱として捨てられていた熱エネルギーを電力として利用する、いわゆるユビキタス発電を実現できると考えられる。   In the present invention, since the flexibility of the module in which the π-type elements are electrically connected in series is improved, an unprecedented usage such as pasting to a heating element on a curved surface becomes possible. For example, it is considered that so-called ubiquitous power generation that uses heat energy such as steam pipes, incinerators, and clothing that has been discarded as waste heat until now as electric power can be realized.

また、大面積の素子が安価に製造できるため、太陽電池のように光電変換された残りのエネルギーが熱に変換されるような装置と組み合わせて使用することも好ましい。   In addition, since a large-area element can be manufactured at low cost, it is also preferable to use it in combination with a device that converts the remaining energy photoelectrically converted into heat, such as a solar cell.

以下、実施例を挙げて本発明を具体的に説明するが、本発明はこれらに限定されるものではない。なお、実施例において「部」あるいは「%」の表示を用いるが、特に断りがない限り「質量部」あるいは「質量%」を表す。   EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "part by mass" or "mass%" is represented.

実施例1
《熱電変換素子の作製》
〔金属層用の金属箔の作製〕
(銅箔1〜4の作製)
〈銅箔1の作製〉
厚さ20μmのポリプロピレンフィルム上に、加熱蒸着法により、厚さ300nmの銅蒸着膜を形成した。次いで、ポリプロピレンフィルム上より銅蒸着膜を隔離し、銅蒸着膜をスタンプミル粉砕して、厚さ300nm、平均アスペクト比が70、熱伝導率が400W/m・Kの銅箔1を得た。
Example 1
<Production of thermoelectric conversion element>
[Production of metal foil for metal layer]
(Preparation of copper foils 1-4)
<Preparation of copper foil 1>
A copper vapor deposition film having a thickness of 300 nm was formed on a polypropylene film having a thickness of 20 μm by a heat vapor deposition method. Next, the copper vapor-deposited film was isolated from the polypropylene film, and the copper vapor-deposited film was stamp mill pulverized to obtain a copper foil 1 having a thickness of 300 nm, an average aspect ratio of 70, and a thermal conductivity of 400 W / m · K.

〈銅箔2の作製〉
上記銅箔1の作製において、スタンプミル粉砕条件を調整し、平均アスペクト比を10とした以外は同様にして、厚さ300nm、平均アスペクト比が10、熱伝導率が400W/m・Kの銅箔2を得た。
<Preparation of copper foil 2>
In the production of the copper foil 1, copper having a thickness of 300 nm, an average aspect ratio of 10, and a thermal conductivity of 400 W / m · K was similarly obtained except that the stamp mill grinding conditions were adjusted and the average aspect ratio was set to 10. A foil 2 was obtained.

〈銅箔3の作製〉
上記銅箔1の作製において、加熱蒸着法の蒸着時間を変更して厚さを800nmとし、かつスタンプミル粉砕条件を調整し、平均アスペクト比を10とした以外は同様にして、厚さ800nm、平均アスペクト比が10、熱伝導率が400W/m・Kの銅箔3を得た。
<Preparation of copper foil 3>
In the production of the copper foil 1, the thickness was set to 800 nm by changing the vapor deposition time of the heat vapor deposition method, and the stamp mill pulverization conditions were adjusted to obtain an average aspect ratio of 10. A copper foil 3 having an average aspect ratio of 10 and a thermal conductivity of 400 W / m · K was obtained.

〈銅箔4の作製〉
上記銅箔1の作製において、加熱蒸着法の蒸着時間を変更して厚さを1500nmとし、かつスタンプミル粉砕条件を調整し、平均アスペクト比を5とした以外は同様にして、厚さ1500nm、平均アスペクト比が5、熱伝導率が400W/m・Kの銅箔4を得た。
<Preparation of copper foil 4>
In the production of the copper foil 1, the thickness is 1500 nm, except that the deposition time of the heat deposition method is changed to 1500 nm, the stamp mill grinding conditions are adjusted, and the average aspect ratio is 5. A copper foil 4 having an average aspect ratio of 5 and a thermal conductivity of 400 W / m · K was obtained.

(金箔1の作製)
上記銅箔1の作製において、蒸発源の用いる化合物を銅化合物に代えて金化合物を用い、加熱蒸着法の蒸着時間及びスタンプミル粉砕条件を適宜調整した以外は同様にして、厚さ300nm、平均アスペクト比が70、熱伝導率が320W/m・Kの金箔1を得た。
(Preparation of gold leaf 1)
In the production of the copper foil 1, a thickness of 300 nm, an average was obtained in the same manner except that the compound used for the evaporation source was replaced with a copper compound and a gold compound was used, and the deposition time and stamp mill grinding conditions of the heating deposition method were appropriately adjusted. A gold foil 1 having an aspect ratio of 70 and a thermal conductivity of 320 W / m · K was obtained.

(白金箔1の作製)
上記銅箔1の作製において、蒸発源の用いる化合物を銅化合物に代えて白金化合物を用い、加熱蒸着法の蒸着時間及びスタンプミル粉砕条件を適宜調整した以外は同様にして、厚さ800nm、平均アスペクト比が10、熱伝導率が70W/m・Kの白金箔1を得た。
(Production of platinum foil 1)
In the production of the copper foil 1, a thickness of 800 nm, an average was obtained in the same manner except that the compound used for the evaporation source was replaced with a copper compound and a platinum compound was used, and the deposition time and stamp mill grinding conditions of the heating deposition method were appropriately adjusted. A platinum foil 1 having an aspect ratio of 10 and a thermal conductivity of 70 W / m · K was obtained.

(窒化アルミニウム箔1の作製)
特開2007−110281号公報の実施例に記載の方法に従って、厚さ300nm、平均アスペクト比が10、熱伝導率が400W/m・Kの非金属である窒化アルミニウム箔1を得た。
(Preparation of aluminum nitride foil 1)
According to the method described in Examples of Japanese Patent Application Laid-Open No. 2007-110281, a non-metal aluminum nitride foil 1 having a thickness of 300 nm, an average aspect ratio of 10, and a thermal conductivity of 400 W / m · K was obtained.

〔熱電変換素子1の作製〕
上記作製した銅箔1を用いて、下記の方法に従って熱電変換素子1を作製した。
[Production of Thermoelectric Conversion Element 1]
The thermoelectric conversion element 1 was produced according to the following method using the produced copper foil 1.

〈半導体層の作製〉
15μmの高純度アルミ箔上に、別途単ロール急冷法で作製した急冷薄片状のp型のBi−Te半導体、n型のBi−Te半導体を仮プレス(200℃、10MPa)した後、図3のa)に示すように配置した。仮プレス物は、それぞれ10mm角で、膜厚は10μmとなるようにした。素子間の間隙は1mmとした。
<Fabrication of semiconductor layer>
After temporary pressing (200 ° C., 10 MPa) of a rapidly cooled flaky p-type Bi-Te semiconductor and n-type Bi—Te semiconductor separately produced by a single roll quenching method on a 15 μm high-purity aluminum foil, FIG. It was arranged as shown in a). The temporary press products were each 10 mm square and the film thickness was 10 μm. The gap between the elements was 1 mm.

〈金属部の形成〉
ポリエチレンテレフタレート(PET)フィルム上に、上記作製した銅箔1を、適当な割合でポリビニルブチラール樹脂(結着材)、フタル酸ジブチル(可塑剤)、エーテル型非イオン界面活性剤(フォスフォノール 東邦化学社製)、溶剤としてエタノール及びトルエンを加えてスラリー化し、ドクターブレードで塗布、製膜した。次いで、塗布膜をPETフィルムごとアルミナボートに載せ、400℃で脱脂後、500℃で1時間行い、アルミナボート上に空隙率が40%の金属層1(10mm角)を得た。なお、空隙率は、電子顕微鏡を用いて、その断面を観察して求めた。
<Formation of metal part>
On the polyethylene terephthalate (PET) film, the prepared copper foil 1 is coated with polyvinyl butyral resin (binder), dibutyl phthalate (plasticizer), ether type nonionic surfactant (phosphonol Toho) at an appropriate ratio. Chemical Co., Ltd.), ethanol and toluene as a solvent were added to form a slurry, which was then applied with a doctor blade to form a film. Next, the coating film was placed on an alumina boat together with the PET film, degreased at 400 ° C., and then performed at 500 ° C. for 1 hour to obtain a metal layer 1 (10 mm square) having a porosity of 40% on the alumina boat. The porosity was determined by observing the cross section using an electron microscope.

〈積層型熱電変換素子の形成〉
上記作製した図3のa)に示す構成のBi−Teをパターニングした半導体層上に上記空隙を有する金属層1を載せた後、図3のb)に示すように中央部を切断し、更にもう一枚用意した図3のa)に示すp型のBi−Te半導体とn型のBi−Te半導体をパターニングしたアルミを載せ、黒鉛中で36MPaの加圧下で、270℃まで真空中で加熱、本プレスし、図3のc)(図1のb))に示すような、電極間の総膜厚(図1、2、3に示す「A」)に占める金属部の膜厚が60体積%である3層積層型の熱電変換素子1を得た。
<Formation of laminated thermoelectric conversion element>
After placing the metal layer 1 having the voids on the semiconductor layer patterned with Bi-Te having the structure shown in FIG. 3A, the central portion is cut as shown in FIG. Another prepared aluminum plate patterned with p-type Bi-Te semiconductor and n-type Bi-Te semiconductor shown in a) of FIG. 3 is placed and heated in graphite to 270 ° C. under a pressure of 36 MPa. The film thickness of the metal part occupying the total film thickness between electrodes ("A" shown in FIGS. 1, 2, and 3) as shown in FIG. A three-layer laminated thermoelectric conversion element 1 having a volume% was obtained.

〔熱電変換素子2〜13の作製〕
上記熱電変換素子1の作製において、金属部を構成する金属箔の種類(金属種、アスペクト比)、電極間の総膜厚に占める金属部の膜厚(体積%)及び金属部の空隙率を、表1に記載のように変更した以外は同様にして、熱電変換素子2〜13を作製した。
[Production of Thermoelectric Conversion Elements 2 to 13]
In the production of the thermoelectric conversion element 1, the type of metal foil constituting the metal part (metal type, aspect ratio), the film thickness (volume%) of the metal part in the total film thickness between the electrodes, and the porosity of the metal part Thermoelectric conversion elements 2 to 13 were produced in the same manner except that the changes were made as shown in Table 1.

〔熱電変換素子14の作製〕
上記熱電変換素子6の作製において、アルミ箔上に金属部を敷設した後、仮プレスした急冷薄片状のp型のBi−Te半導体、n型のBi−Te半導体を乗せた試料を2セット準備し、一方の試料に更に空隙層を有する金属部を形成した後、両者を図1のc)に示す構成となるように積層した後、黒鉛中で36MPaの加圧下で、270℃まで真空中で加熱、本プレスして、5層を積層した熱電変換素子14を作製した。
[Production of Thermoelectric Conversion Element 14]
In preparation of the thermoelectric conversion element 6, two sets of samples on which a rapidly cooled thin-flaked p-type Bi-Te semiconductor and n-type Bi-Te semiconductor were placed after laying a metal part on an aluminum foil were prepared. Then, after forming a metal part further having a void layer in one sample, both were laminated so as to have the structure shown in FIG. 1 c), and then in a vacuum up to 270 ° C. under a pressure of 36 MPa in graphite. Then, the thermoelectric conversion element 14 in which five layers were laminated was produced.

〔熱電変換素子15の作製〕
上記熱電変換素子10の作製において、金属層構成材料とp型のBi−Te半導体、n型のBi−Te半導体の急冷薄片とをボールミルを用いて混合し、アルミ箔で挟み同様に加熱、加圧した以外は同様にして、図1のa)で示す非積層型の熱電変換素子15を作製した。この熱電変換素子15の電極間の総膜厚(図1、2、3に示す「A」)は20体積%、空隙率は70体積%であった。なお、体積率は、金属層を有さない素子を同様に作製したときの膜厚の差から膜中の金属部の比率を求め、さらに膜全体を硝酸で溶解し元素分析することで素子に対する金属含有量を求め、金属部の空隙率を計算した。
[Preparation of Thermoelectric Conversion Element 15]
In the production of the thermoelectric conversion element 10, the metal layer constituent material, the p-type Bi-Te semiconductor, and the n-type Bi-Te semiconductor quenching flakes are mixed using a ball mill, sandwiched between aluminum foils, and heated and heated in the same manner. A non-stacked thermoelectric conversion element 15 shown in FIG. 1 a was produced in the same manner except that the pressure was applied. The total film thickness between the electrodes of this thermoelectric conversion element 15 ("A" shown in FIGS. 1, 2, and 3) was 20% by volume, and the porosity was 70% by volume. In addition, the volume ratio is obtained for the element by obtaining the ratio of the metal part in the film from the difference in film thickness when the element having no metal layer is similarly produced, and further dissolving the entire film with nitric acid and performing elemental analysis. The metal content was determined and the porosity of the metal part was calculated.

〔熱電変換素子16の作製〕
上記熱電変換素子15の作製において、金属層を構成する材料として金属箔を除いた以外は同様にして、熱電変換素子16を作製した。
[Production of Thermoelectric Conversion Element 16]
In the production of the thermoelectric conversion element 15, a thermoelectric conversion element 16 was produced in the same manner except that the metal foil was removed as a material constituting the metal layer.

《熱電変換素子の評価》
〔熱電変換効率の評価〕
上記作製した各熱電変換素子を、120度の平板ホットプレート上に設置し、他面を20度の水を通した金属ブロックで冷却した。その状態で、下部電極から得られた起電力値Aを測定し、熱電変換素子6の起電力値Aを100とした相対値を求めた。得られる相対電力値が大きいほど、熱電変換能の高い素子と考えられる。
<< Evaluation of thermoelectric conversion element >>
[Evaluation of thermoelectric conversion efficiency]
Each of the produced thermoelectric conversion elements was placed on a 120 ° flat plate hot plate, and the other surface was cooled with a metal block through which 20 ° water was passed. In this state, the electromotive force value A obtained from the lower electrode was measured, and the relative value with the electromotive force value A of the thermoelectric conversion element 6 as 100 was obtained. The larger the relative power value obtained, the higher the thermoelectric conversion capability.

〔折り曲げ耐性の評価〕
上記作製した各熱電変換素子を、φ20mmの円筒に長手方向が円周になるように巻きつける操作と、平面上に広げる操作を各5回繰り返した後、上記熱電変換効率の評価と同様の方法で起電力値Bを測定し、熱電変換効率の評価で求めた初期の起電力値Aに対する起電力値Bの劣化巾(%)を求めた。劣化巾が大きいと、マイナスの数値が大きくなり、その値が小さいほど可撓性が高いと考えられる。
[Evaluation of bending resistance]
The same method as the evaluation of the thermoelectric conversion efficiency after repeating the operation of winding each of the produced thermoelectric conversion elements around a φ20 mm cylinder so that the longitudinal direction is a circumference and the operation of spreading on a plane five times each. Then, the electromotive force value B was measured, and the deterioration width (%) of the electromotive force value B with respect to the initial electromotive force value A obtained by evaluating the thermoelectric conversion efficiency was obtained. If the deterioration width is large, the negative numerical value becomes large, and the smaller the value, the higher the flexibility.

以上により得られた結果を、表1に示す。   The results obtained as described above are shown in Table 1.

Figure 2010027895
Figure 2010027895

表1に記載の結果より明らかなように、本発明で規定する構成からなる熱電変換素子は、優れた熱電変換効率を有すると共に、比較例に対し高い折り曲げ耐性を備えていることが分かる。   As is apparent from the results shown in Table 1, it can be seen that the thermoelectric conversion element having the configuration defined in the present invention has excellent thermoelectric conversion efficiency and high bending resistance with respect to the comparative example.

実施例2
《ワイヤー状金属粒子の作製》
〔ワイヤー状金粒子の作製〕
(ワイヤー状金粒子1の作製)
400ミリモルのヘキサデシルトリメチルアンモニウムブロミド水溶液1000mlに、10ミリモルの硝酸銅水溶液60ml(600μmol)を添加した。この溶液に、24ミリモルの塩化金酸水溶液を84ml(2016μmol)添加して良く攪拌した。次いで、この溶液に第一の還元剤として10ミリモルのジメチルアミンボランを用い、ジメチルアミンボランの添加量が60ml(600μmol)となるよう10回に分けて添加(6ml×10回)した。次いで、この溶液に、第二の還元剤としてトリエチルアミン2.5ml(180mmol)を添加して30秒間攪拌し、その後30℃で48時間静置して、直径(短軸)が30nm、長さ(長軸)が2.1μm、アスペクト比が70、熱伝導率が320W/m・Kのワイヤー状金粒子1を得た。
Example 2
<< Production of wire-like metal particles >>
[Production of wire-like gold particles]
(Preparation of wire-like gold particles 1)
To 1000 ml of 400 mmol hexadecyltrimethylammonium bromide aqueous solution, 60 ml (600 μmol) of 10 mmol aqueous copper nitrate solution was added. To this solution, 84 ml (2016 μmol) of a 24 mmol aqueous solution of chloroauric acid was added and stirred well. Next, 10 mmol of dimethylamine borane was used as the first reducing agent in this solution, and dimethylamine borane was added in 10 portions (6 ml × 10 times) so that the addition amount of dimethylamine borane was 60 ml (600 μmol). Next, 2.5 ml (180 mmol) of triethylamine as a second reducing agent was added to this solution and stirred for 30 seconds, and then allowed to stand at 30 ° C. for 48 hours. The diameter (short axis) was 30 nm and the length ( Wire-like gold particles 1 having a major axis (2.1 μm), an aspect ratio of 70, and a thermal conductivity of 320 W / m · K were obtained.

(ワイヤー状金粒子2〜4の作製)
上記ワイヤー状金粒子1の作製において、還元剤の種類、添加量を適宜変更して、直径(短軸)が30nm、長さ(長軸)が300nm、アスペクト比が10のワイヤー状金粒子2、直径(短軸)が14nm、長さ(長軸)が210nm、アスペクト比が15のワイヤー状金粒子3、直径(短軸)が20nm、長さ(長軸)が32nm、アスペクト比が1.6のワイヤー状金粒子4を作製した。
(Preparation of wire-like gold particles 2 to 4)
In the production of the wire-like gold particles 1, the type and amount of the reducing agent are appropriately changed so that the wire-like gold particles 2 having a diameter (short axis) of 30 nm, a length (major axis) of 300 nm, and an aspect ratio of 10 are used. Wire-shaped gold particles 3 having a diameter (minor axis) of 14 nm, a length (major axis) of 210 nm, and an aspect ratio of 15, a diameter (minor axis) of 20 nm, a length (major axis) of 32 nm, and an aspect ratio of 1 .6 wire-like gold particles 4 were produced.

〔ワイヤー状銀粒子1の作製〕
Adv.Mater.2002,14,833〜837に記載の方法を参考に、還元剤としてエチレングリコール(EG)を、保護コロイド剤兼形態制御剤としてポリビニルピロリドン(PVP)を使用し、かつ核形成工程と粒子成長工程1を分離して、以下のような方法でワイヤー状銀粒子1を作製した。
[Preparation of wire-like silver particles 1]
Adv. Mater. Reference is made to the method described in 2002, 14, 833 to 837, ethylene glycol (EG) is used as a reducing agent, polyvinylpyrrolidone (PVP) is used as a protective colloid agent and form control agent, and a nucleation step and a particle growth step 1 was separated, and wire-like silver particles 1 were produced by the following method.

(核形成工程)
反応容器内で170℃に保持したEG液100mlを攪拌しながら、硝酸銀のEG溶液(硝酸銀濃度:1.5×10−4モル/L)10mlを、一定の流量で10秒間で添加した。その後、170℃で10分間熟成を施し、銀の核粒子を形成した。熟成終了後の反応液は、銀ナノ粒子の表面プラズモン吸収に由来した黄色を呈しており、銀イオンが還元されて、銀ナノ粒子が形成されたことが確認された。
(Nucleation process)
While stirring 100 ml of EG solution maintained at 170 ° C. in the reaction vessel, 10 ml of EG solution of silver nitrate (silver nitrate concentration: 1.5 × 10 −4 mol / L) was added at a constant flow rate for 10 seconds. Thereafter, aging was carried out at 170 ° C. for 10 minutes to form silver core particles. The reaction solution after completion of ripening exhibited a yellow color derived from surface plasmon absorption of silver nanoparticles, and it was confirmed that silver ions were reduced and silver nanoparticles were formed.

(粒子成長工程)
上記の熟成を終了した核粒子を含む反応液を攪拌しながら170℃に保持し、硝酸銀のEG溶液(硝酸銀濃度:1.0×10−1モル/L)100mlと、PVPのEG溶液(PVP濃度:5.0×10−1モル/L)100mlを、ダブルジェット法を用いて一定の流量で100分間で添加した。粒子成長工程において20分毎に反応液を採取して電子顕微鏡で確認したところ、核形成工程で形成された銀ナノ粒子が時間経過に伴って、主にナノワイヤの長軸方向に成長しており、粒子成長工程における新たな核粒子の生成は認められなかった。
(Particle growth process)
The reaction solution containing the core particles after ripening is maintained at 170 ° C. with stirring, and 100 ml of an EG solution of silver nitrate (silver nitrate concentration: 1.0 × 10 −1 mol / L) and an EG solution of PVP (PVP) 100 ml of a concentration: 5.0 × 10 −1 mol / L) was added at a constant flow rate for 100 minutes using a double jet method. When the reaction solution was sampled every 20 minutes in the particle growth process and confirmed with an electron microscope, the silver nanoparticles formed in the nucleation process grew mainly in the long axis direction of the nanowires over time. No new core particles were observed in the grain growth process.

(水洗工程)
粒子成長工程終了後、反応液を室温まで冷却した後、フィルターを用いて濾過し、濾別された銀ナノワイヤをエタノール中に再分散した。フィルターによる銀ナノワイヤの濾過とエタノール中への再分散を5回繰り返し、最終的に銀ナノワイヤのエタノール分散液を調製して、ワイヤー状銀粒子1を作製した。
(Washing process)
After completion of the particle growth step, the reaction solution was cooled to room temperature, filtered using a filter, and the silver nanowires separated by filtration were redispersed in ethanol. Filtration of silver nanowires with a filter and redispersion in ethanol were repeated 5 times. Finally, an ethanol dispersion of silver nanowires was prepared to produce wire-like silver particles 1.

得られた分散液を微量採取し電子顕微鏡で確認したところ、平均直径が40nm、平均長さ2.0μm、アスペクト比が50、熱伝導率が420W/m・Kのワイヤ状銀粒子が形成されたことが確認できた。   When a small amount of the obtained dispersion was collected and confirmed with an electron microscope, wire-like silver particles having an average diameter of 40 nm, an average length of 2.0 μm, an aspect ratio of 50, and a thermal conductivity of 420 W / m · K were formed. I was able to confirm.

〔ワイヤー状酸化マグネシウム粒子1の作製〕
J.Phys.Chem.B2002,106,7449−7452に記載の方法に従って、直径(短軸)が20nm、長さ(長軸)が800nm、アスペクト比が40のワイヤー状酸化マグネシウム粒子1を作製した。
[Preparation of wire-like magnesium oxide particles 1]
J. et al. Phys. Chem. In accordance with the method described in B2002, 106, 7449-7492, wire-shaped magnesium oxide particles 1 having a diameter (short axis) of 20 nm, a length (long axis) of 800 nm, and an aspect ratio of 40 were produced.

〔熱電変換素子17の作製〕
上記作製したワイヤー状銀粒子1を用いて、下記の方法に従って熱電変換素子17を作製した。
[Preparation of Thermoelectric Conversion Element 17]
The thermoelectric conversion element 17 was produced according to the following method using the produced wire-like silver particles 1.

〈半導体層の作製〉
15μmの高純度アルミ箔上に、別途単ロール急冷法で作製した急冷薄片状のp型のBi−Te半導体、n型のBi−Te半導体を仮プレス(200℃、10MPa)した後、図3のa)に示すように配置した。仮プレス物は、それぞれ10mm角で、膜厚は10μmとなるようにした。素子間の間隙は1mmとした。
<Fabrication of semiconductor layer>
After temporary pressing (200 ° C., 10 MPa) of a rapidly cooled flaky p-type Bi-Te semiconductor and n-type Bi—Te semiconductor separately produced by a single roll quenching method on a 15 μm high-purity aluminum foil, FIG. It was arranged as shown in a). The temporary press products were each 10 mm square and the film thickness was 10 μm. The gap between the elements was 1 mm.

〈金属部の形成〉
ポリエチレンテレフタレート(PET)フィルム上に、上記作製したワイヤー状銀粒子1を、適当な割合でポリビニルブチラール樹脂(結着材)、フタル酸ジブチル(可塑剤)、エーテル型非イオン界面活性剤(フォスフォノール 東邦化学社製)、溶剤としてエタノール及びトルエンを加えてスラリー化し、ドクターブレードで塗布、製膜した。次いで、塗布膜をPETフィルムごとアルミナボートに載せ、400℃で脱脂後、500℃で1時間行い、アルミナボート上に空隙率が40%の金属層17(10mm角)を得た。なお、空隙率は、電子顕微鏡を用いて、その断面を観察して求めた。
<Formation of metal part>
On a polyethylene terephthalate (PET) film, the wire-like silver particles 1 prepared above are polyvinyl butyral resin (binder), dibutyl phthalate (plasticizer), ether type nonionic surfactant (phosphor) in an appropriate ratio. Nord, manufactured by Toho Chemical Co., Ltd.), ethanol and toluene as a solvent were added to form a slurry, which was coated with a doctor blade to form a film. Next, the coating film was placed on an alumina boat together with the PET film, degreased at 400 ° C., and then performed at 500 ° C. for 1 hour to obtain a metal layer 17 (10 mm square) having a porosity of 40% on the alumina boat. The porosity was determined by observing the cross section using an electron microscope.

〈積層型熱電変換素子の形成〉
上記作製した図3のa)に示す構成のBi−Teをパターニングした半導体層上に上記空隙を有する金属層17を載せた後、図3のb)に示すように中央部を切断し、更にもう一枚用意した図3のa)に示すp型のBi−Te半導体とn型のBi−Te半導体をパターニングしたアルミを載せ、黒鉛中で36MPaの加圧下で、270℃まで真空中で加熱、本プレスし、図3のc)(図2のb))に示すような、電極間の総膜厚(図1、2、3に示す「A」)に占める金属部の膜厚が60体積%である3層積層型の熱電変換素子17を得た。
<Formation of laminated thermoelectric conversion element>
After the metal layer 17 having the voids is placed on the semiconductor layer patterned with Bi-Te having the structure shown in FIG. 3A, the central portion is cut as shown in FIG. Another prepared aluminum plate patterned with p-type Bi-Te semiconductor and n-type Bi-Te semiconductor shown in a) of FIG. 3 is placed and heated in graphite to 270 ° C. under a pressure of 36 MPa. The thickness of the metal part in the total thickness between the electrodes ("A" shown in FIGS. 1, 2, and 3) as shown in FIG. 3c) (FIG. 2b)) is 60%. A three-layered thermoelectric conversion element 17 having a volume% was obtained.

〔熱電変換素子18〜28の作製〕
上記熱電変換素子17の作製において、金属部を構成するワイヤー状粒子の種類(金属種、アスペクト比)、電極間の総膜厚に占める金属部の膜厚(体積%)及び金属部の空隙率を、表2に記載のように変更した以外は同様にして、熱電変換素子18〜28を作製した。
[Production of thermoelectric conversion elements 18 to 28]
In the production of the thermoelectric conversion element 17, the type of the wire-like particles (metal type, aspect ratio) constituting the metal part, the film thickness (volume%) of the metal part in the total film thickness between the electrodes, and the porosity of the metal part Were changed in the same manner as described in Table 2, and thermoelectric conversion elements 18 to 28 were produced.

〔熱電変換素子29の作製〕
上記熱電変換素子22の作製において、アルミ箔上に金属部を敷設した後、仮プレスした急冷薄片状のp型のBi−Te半導体、n型のBi−Te半導体を乗せた試料を2セット準備し、一方の試料に更に空隙層を有する金属部を形成した後、両者を図1のc)に示す構成となるように積層した後、黒鉛中で36MPaの加圧下で、270℃まで真空中で加熱、本プレスして、5層を積層した熱電変換素子29を作製した。
[Production of Thermoelectric Conversion Element 29]
In preparation of the thermoelectric conversion element 22, two sets of samples were prepared by placing a metal part on an aluminum foil and then placing a pre-pressed quenched thin-flaked p-type Bi-Te semiconductor and n-type Bi-Te semiconductor. Then, after forming a metal part further having a void layer in one sample, both were laminated so as to have the structure shown in FIG. 1 c), and then in a vacuum up to 270 ° C. under a pressure of 36 MPa in graphite. Then, the thermoelectric conversion element 29 was prepared by laminating five layers.

〔熱電変換素子30の作製〕
上記熱電変換素子26の作製において、金属層構成材料とp型のBi−Te半導体、n型のBi−Te半導体の急冷薄片とをボールミルを用いて混合し、アルミ箔で挟み同様に加熱、加圧した以外は同様にして、図1のa)で示す非積層型の熱電変換素子30を作製した。この熱電変換素子30の電極間の総膜厚(図1、2、3に示す「A」)は10体積%、空隙率は70体積%であった。なお、体積率は、金属層を有さない素子を同様に作製したときの膜厚の差から膜中の金属部の比率を求め、さらに膜全体を硝酸で溶解し元素分析することで素子に対する金属含有量を求め、金属部の空隙率を計算した。
[Production of Thermoelectric Conversion Element 30]
In the production of the thermoelectric conversion element 26, the metal layer constituent material, the p-type Bi-Te semiconductor, and the n-type Bi-Te semiconductor quenching flakes are mixed using a ball mill, sandwiched between aluminum foils, and heated and heated in the same manner. A non-stacked thermoelectric conversion element 30 shown in FIG. 1 a was produced in the same manner except that the pressure was applied. The total film thickness ("A" shown in FIGS. 1, 2, and 3) between the electrodes of the thermoelectric conversion element 30 was 10% by volume, and the porosity was 70% by volume. In addition, the volume ratio is obtained for the element by obtaining the ratio of the metal part in the film from the difference in film thickness when the element having no metal layer is similarly produced, and further dissolving the entire film with nitric acid and performing elemental analysis. The metal content was determined and the porosity of the metal part was calculated.

〔熱電変換素子31の作製〕
上記熱電変換素子30の作製において、金属層を構成する材料としてワイヤー状金粒子1を除いた以外は同様にして、熱電変換素子31を作製した。
[Production of Thermoelectric Conversion Element 31]
In the production of the thermoelectric conversion element 30, a thermoelectric conversion element 31 was produced in the same manner except that the wire-like gold particles 1 were excluded as a material constituting the metal layer.

《熱電変換素子の評価》
〔熱電変換効率の評価〕
上記作製した各熱電変換素子を、120度の平板ホットプレート上に設置し、他面を20度の水を通した金属ブロックで冷却した。その状態で、下部電極から得られた起電力値Aを測定し、実施例1で作製した熱電変換素子6の起電力値Aを100とした相対値を求めた。得られる相対電力値が大きいほど、熱電変換能の高い素子と考えられる。
<< Evaluation of thermoelectric conversion element >>
[Evaluation of thermoelectric conversion efficiency]
Each of the produced thermoelectric conversion elements was placed on a 120 ° flat plate hot plate, and the other surface was cooled with a metal block through which 20 ° water was passed. In this state, the electromotive force value A obtained from the lower electrode was measured, and a relative value was obtained with the electromotive force value A of the thermoelectric conversion element 6 produced in Example 1 being 100. The larger the relative power value obtained, the higher the thermoelectric conversion capability.

〔折り曲げ耐性の評価〕
上記作製した各熱電変換素子を、φ20mmの円筒に長手方向が円周になるように巻きつける操作と、平面上に広げる操作を各5回繰り返した後、上記熱電変換効率の評価と同様の方法で起電力値Bを測定し、熱電変換効率の評価で求めた初期の起電力値Aに対する起電力値Bの劣化巾(%)を求めた。劣化巾が大きいと、マイナスの数値が大きくなり、その値が小さいほど可撓性が高いと考えられる。
[Evaluation of bending resistance]
The same method as the evaluation of the thermoelectric conversion efficiency after repeating the operation of winding each of the produced thermoelectric conversion elements around a φ20 mm cylinder so that the longitudinal direction is a circumference and the operation of spreading on a plane five times each. Then, the electromotive force value B was measured, and the deterioration width (%) of the electromotive force value B with respect to the initial electromotive force value A obtained by the evaluation of the thermoelectric conversion efficiency was obtained. If the deterioration width is large, the negative numerical value becomes large, and the smaller the value, the higher the flexibility.

以上により得られた結果を、表2に示す。   The results obtained as described above are shown in Table 2.

Figure 2010027895
Figure 2010027895

表2に記載の結果より明らかなように、本発明で規定する構成で、かつ金属層にワイヤー状粒子を含む熱電変換素子は、更に優れた熱電変換効率を有すると共に、比較例に対し高い折り曲げ耐性を備えていることが分かる。   As is apparent from the results shown in Table 2, the thermoelectric conversion element having the configuration defined in the present invention and including the wire-like particles in the metal layer has a further excellent thermoelectric conversion efficiency, and is higher in bending than the comparative example. It turns out that it has tolerance.

本発明の熱電変換素子の構成の一例を示す概略断面図である。It is a schematic sectional drawing which shows an example of a structure of the thermoelectric conversion element of this invention. 高アスペクト比の金属粒子を含有した空隙を有する金属部を有する熱電変換素子の一例を示す概略断面図である。It is a schematic sectional drawing which shows an example of the thermoelectric conversion element which has a metal part which has the space | gap containing the metal particle of a high aspect ratio. 本発明の熱電変換素子の作製方法に一例を示す概略断面図である。It is a schematic sectional drawing which shows an example in the manufacturing method of the thermoelectric conversion element of this invention.

符号の説明Explanation of symbols

10 熱電変換素子
11、12 電極
13、13′ 熱電変換半導体
14 金属層
15 ウィスカー状金属粒子
16 ワイヤー状金属粒子
17 薄片状金属粒子
18 箔(フォイル)状金属粒子
DESCRIPTION OF SYMBOLS 10 Thermoelectric conversion element 11, 12 Electrode 13, 13 'Thermoelectric conversion semiconductor 14 Metal layer 15 Whisker-like metal particle 16 Wire-like metal particle 17 Flake-like metal particle 18 Foil-like metal particle

Claims (5)

熱電変換半導体及び、40体積%以上99体積%以下の空隙率を有する金属部が含有されていることを特徴とする熱電変換素子。 A thermoelectric conversion element comprising a thermoelectric conversion semiconductor and a metal part having a porosity of 40% by volume to 99% by volume. 前記熱電変換半導体及び前記空隙率を有する金属部が、一対の電極に挟持されていることを特徴とする請求項1に記載の熱電変換素子。 The thermoelectric conversion element according to claim 1, wherein the thermoelectric conversion semiconductor and the metal part having the porosity are sandwiched between a pair of electrodes. 前記空隙率を有する金属部が、100W/m・K以上の熱伝導率を有する金属からなることを特徴とする請求項1または2に記載の熱電変換素子。 The thermoelectric conversion element according to claim 1, wherein the metal part having the porosity is made of a metal having a thermal conductivity of 100 W / m · K or more. 金属部が、アスペクト比が5.0以上である金属粒子の集合体であることを特徴とする請求項1〜3のいずれか1項に記載の熱電変換素子。 The thermoelectric conversion element according to any one of claims 1 to 3, wherein the metal part is an aggregate of metal particles having an aspect ratio of 5.0 or more. 前記空隙率を有する金属部が、層状の熱電変換半導体に積層された構造であることを特徴とする請求項1〜4のいずれか1項に記載の熱電変換素子。 The thermoelectric conversion element according to any one of claims 1 to 4, wherein the metal portion having the porosity is a structure laminated on a layered thermoelectric conversion semiconductor.
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US8940995B2 (en) 2009-07-06 2015-01-27 Electronics And Telecommunications Research Institute Thermoelectric device and method for fabricating the same
KR20110017957A (en) * 2009-08-17 2011-02-23 한국전자통신연구원 The thermoelectric-generator
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