JP7054925B2 - Thermoelectric conversion material - Google Patents

Thermoelectric conversion material Download PDF

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JP7054925B2
JP7054925B2 JP2018535729A JP2018535729A JP7054925B2 JP 7054925 B2 JP7054925 B2 JP 7054925B2 JP 2018535729 A JP2018535729 A JP 2018535729A JP 2018535729 A JP2018535729 A JP 2018535729A JP 7054925 B2 JP7054925 B2 JP 7054925B2
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良次 舟橋
コンベ・エマニュエル
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National Institute of Advanced Industrial Science and Technology AIST
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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
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    • B22F3/14—Both compacting and sintering simultaneously
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    • 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
    • H10N10/853—Thermoelectric active materials comprising inorganic compositions comprising arsenic, antimony or bismuth

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Description

本発明は、合金、当該合金の製造方法、当該合金からなる熱電変換材料、当該熱電変換材料を用いた熱電変換モジュールに関する。 The present invention relates to an alloy, a method for producing the alloy, a thermoelectric conversion material made of the alloy, and a thermoelectric conversion module using the thermoelectric conversion material.

我が国では、一次供給エネルギーからの有効なエネルギーの得率は３０％程度に過ぎず、約７０％ものエネルギーを最終的には熱として大気中に廃棄されている。また、工場やごみ焼却場などにおいて、燃焼により生じる熱も、他のエネルギーに変換されることなく大気中に廃棄されている。このように、我々人類は非常に多くの熱エネルギーを無駄に廃棄しており、化石エネルギーの燃焼等の行為から僅かなエネルギーしか獲得していない。 In Japan, the rate of obtaining effective energy from the primary supply energy is only about 30%, and about 70% of the energy is finally discarded as heat in the atmosphere. In addition, heat generated by combustion in factories and waste incinerators is also discarded in the atmosphere without being converted into other energy. In this way, we human beings waste a great deal of heat energy and obtain only a small amount of energy from actions such as burning fossil energy.

エネルギーの得率を向上させるためには、大気中に廃棄されている熱エネルギーを利用できるようにすることが有効である。一般的に、廃熱は、工場や自動車など高温の排気ガスとして放出されるが、液化天然ガスを熱交換により気化させるときに発生する低温の廃熱も存在する。この冷廃熱を直接電気に変換する熱電発電は、有望な技術である。 In order to improve the energy acquisition rate, it is effective to make available the thermal energy that is wasted in the atmosphere. Generally, waste heat is released as high-temperature exhaust gas in factories and automobiles, but there is also low-temperature waste heat generated when liquefied natural gas is vaporized by heat exchange. Thermoelectric power generation, which directly converts this cold waste heat into electricity, is a promising technology.

熱電発電とは、ゼーベック効果を利用したものであり、熱電変換材料の両端で温度差をつけることで電位差を生じさせて、発電を行うエネルギー変換法である。この方法では、熱電変換材料の一端を液化天然ガスの気化により生じた低温部に配置し、もう一端を常温の大気中または水槽に接するように配置して、それぞれの両端に導線を接続するだけで電気が得られ、一般の発電に必要なモーターやタービン等の可動装置は全く必要ない。このためコストも安く、排出ガスも無く、熱電変換材料が劣化するまで継続的に発電を行うことができる。 Thermoelectric power generation utilizes the Zeebeck effect, and is an energy conversion method in which a potential difference is generated by creating a temperature difference between both ends of a thermoelectric conversion material to generate electricity. In this method, one end of the thermoelectric conversion material is placed in the low temperature part generated by the vaporization of liquefied natural gas, the other end is placed in the atmosphere at room temperature or in contact with the water tank, and the conductors are connected to both ends of each. Electricity can be obtained with, and there is no need for moving devices such as motors and turbines required for general power generation. Therefore, the cost is low, there is no exhaust gas, and power can be continuously generated until the thermoelectric conversion material deteriorates.

熱電変換のもう一つの利用方法として、熱電変換材料に電流を流すことで、その両端に温度差を作ることが挙げられる。例えば、熱電変換材料の低温側を用いれば、冷却素子として利用できる。この冷却方式をペルチェ冷却と呼ぶ。超伝導素子や赤外線センサー素子は、冷却が必須である。特に、超伝導素子は、材料が超伝導状態になるまで冷却が必要である。そのためには、液体窒素を用いる必要があるが、液体を冷媒で用いることは取り扱いや供給が煩雑であり、安全性にも問題が生じる。そこで、様々なセンサーの使用において、１００Ｋ程度まで冷却が可能な固体冷却素子は不可欠であり、熱電変換効果によるペルチェ冷却素子が、最も有望である。 Another method of using thermoelectric conversion is to create a temperature difference between both ends of the thermoelectric conversion material by passing an electric current through it. For example, if the low temperature side of the thermoelectric conversion material is used, it can be used as a cooling element. This cooling method is called Pelche cooling. Cooling is essential for superconducting elements and infrared sensor elements. In particular, superconducting devices need to be cooled until the material is in a superconducting state. For that purpose, it is necessary to use liquid nitrogen, but using liquid as a refrigerant is complicated to handle and supply, and causes a problem in safety. Therefore, in the use of various sensors, a solid cooling element capable of cooling up to about 100 K is indispensable, and a Pelche cooling element due to a thermoelectric conversion effect is the most promising.

このように、熱電変換は、エネルギー問題の解決の一端とインターネット・オブ・シングス（ＩｏＴ）社会に必要なセンサーの普及に大きく貢献する技術である。そのためには、高い熱電変換効率を有し、耐久性の高い熱電変換材料が必要となる。 In this way, thermoelectric conversion is a technology that greatly contributes to the solution of energy problems and the spread of sensors necessary for the Internet of Things (IoT) society. For that purpose, a thermoelectric conversion material having high thermoelectric conversion efficiency and high durability is required.

これまでに、低温で優れた熱電変換性能を示す物質として、例えば、Ｂｉ2Ｔｅ3合金が報告されている（下記非特許文献１参照）。Ｂｉ2Ｔｅ3は、ペルチェ素子として既に市販されているが、性能の高い温度は、２５０Ｋから室温付近であり、１５０Ｋ以下程度での冷却や発電には、効率が低い。So far, for example, Bi 2 Te 3 alloy has been reported as a substance exhibiting excellent thermoelectric conversion performance at low temperature (see Non-Patent Document 1 below). Bi 2 Te 3 is already on the market as a Pelche element, but its high performance temperature is around 250K to room temperature, and its efficiency is low for cooling and power generation at about 150K or less.

さらに、熱電変換材料の性能は、熱電変換性能に関する無次元性能指数ＺＴ（＝Ｓ2Ｔ／（ρκ）、ここで、Ｓ、Ｔ、ρ、κは、それぞれゼーベック係数、絶対温度、電気抵抗率、熱伝導度）を示す）によって評価され、熱電変換材料の実用化には、例えば３００Ｋ程度におけるＺＴ値を高める必要がある。そして、このＺＴ値を高めるためには、３００Ｋ程度における熱伝導度を減少させることが必要である。Furthermore, the performance of the thermoelectric conversion material is the dimensionless performance index ZT (= S 2 T / (ρκ)) with respect to the thermoelectric conversion performance, where S, T, ρ, and κ are the Seebeck coefficient, absolute temperature, and electrical resistivity, respectively. , Thermal conductivity)), and in order to put the thermoelectric conversion material into practical use, it is necessary to increase the ZT value at, for example, about 300K. Then, in order to increase this ZT value, it is necessary to reduce the thermal conductivity at about 300 K.

Ｃ． Ｊ． Ｌｉｕら、Ｊｏｕｒｎａｌ ｏｆ Ｍａｔｅｒｉａｌｓ Ｃｈｅｍｉｓｔｒｙ， Ｖｏｌ． ２２， ｐｐ． ４８２５－４８３１ （２０１２）C. J. Liu et al., Journal of Materials Chemistry, Vol. 22, pp. 4825-4831 (2012)

このような状況下、本発明は、温度３００Ｋ程度の環境での熱伝導度が低く、かつ、８０Ｋ程度の低温下での電気抵抗率が低い、優れた熱電変換特性を示す新規な合金を提供することを主な目的とする。さらに、本発明は、当該合金の製造方法、当該合金からなる熱電変換材料、当該熱電変換材料を用いた熱電変換モジュールを提供することも目的とする。 Under such circumstances, the present invention provides a novel alloy exhibiting excellent thermoelectric conversion characteristics, which has low thermal conductivity in an environment of about 300 K and low electrical resistivity at a low temperature of about 80 K. The main purpose is to do. Further, it is also an object of the present invention to provide a method for manufacturing the alloy, a thermoelectric conversion material made of the alloy, and a thermoelectric conversion module using the thermoelectric conversion material.

本発明者らは、上記のような課題を解決すべく鋭意検討を行った。その結果、組成式：Ｂｉ1-x-yＳｂxＭy （式中、Ｍは、Ｔｉ、Ｖ、Ｃｒ、Ｍｎ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ｓｅ、Ｔｅ、Ｇｅ、Ｓｎ、Ｐｂ、及びＩｎからなる群から選ばれる少なくとも一種の元素であり、０．０３≦ｘ≦０．９５、０．００≦ｙ≦０．２０である）で表され、結晶内に、複数の転位及び複数の双晶の少なくとも一方を有する合金は、温度３００Ｋ程度の環境での熱伝導度が低く、かつ、８０Ｋ程度の低温下での電気抵抗率が低い、優れた熱電変換特性を示すことを見出した。The present inventors have made diligent studies to solve the above problems. As a result, the composition formula: Bi 1-xy Sb x My ( in the formula, M is from Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Se, Te, Ge, Sn, Pb, and In. It is at least one element selected from the group consisting of 0.03 ≦ x ≦ 0.95 and 0.00 ≦ y ≦ 0.20), and has a plurality of rearrangements and a plurality of twin crystals in the crystal. It has been found that the alloy having at least one of the above has excellent thermal conductivity in an environment of about 300 K and low electrical resistivity in a low temperature of about 80 K, and exhibits excellent thermoelectric conversion characteristics.

上記の組成を有しており、かつ、温度３００Ｋにおいて、４．００Ｗ／ｍ・Ｋ以下の熱伝導度を有する合金は、従来知られていない新規な化合物である。 An alloy having the above composition and having a thermal conductivity of 4.00 W / m · K or less at a temperature of 300 K is a novel compound which has not been known conventionally.

本発明は、これらの知見に基づいて、さらに検討を重ねることにより完成された発明である。 The present invention is an invention completed by further studies based on these findings.

すなわち、本発明は、下記に掲げる態様の発明を提供する。
項１． 組成式：Ｂｉ1-x-yＳｂxＭy（式中、Ｍは、Ｔｉ、Ｖ、Ｃｒ、Ｍｎ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ｓｅ、Ｔｅ、Ｇｅ、Ｓｎ、Ｐｂ、及びＩｎからなる群から選ばれる少なくとも一種の元素であり、０．０３≦ｘ≦０．９５、０．００≦ｙ≦０．２０である）で表され、結晶内に、複数の転位及び複数の双晶の少なくとも一方を有する、合金。
項２． 温度３００Ｋにおいて、４．００Ｗ／ｍ・Ｋ以下の熱伝導度を有する、項１に記載の合金。
項３． 組成式：Ｂｉ1-x-yＳｂxＭy（式中、Ｍは、Ｔｉ、Ｖ、Ｃｒ、Ｍｎ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ｓｅ、Ｔｅ、Ｇｅ、Ｓｎ、Ｐｂ、及びＩｎからなる群から選ばれる少なくとも一種の元素であり、０．０３≦ｘ≦０．９５、０．００≦ｙ≦０．２０である）で表され、
温度３００Ｋにおいて、４．００Ｗ／ｍ・Ｋ以下の熱伝導度を有する、合金。
項４． 温度８０Ｋにおいて、５．００ｍΩｃｍ以下の電気抵抗率を有する、項１～３のいずれかに記載の合金。
項５． 項１～４のいずれかに記載の合金からなる、熱電変換材料。
項６． 項５に記載の熱電変換材料を含む、熱電変換モジュール。
項７． Ｂｉ、Ｓｂ、及びＭ（ただし、Ｍは、Ｔｉ、Ｖ、Ｃｒ、Ｍｎ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ｓｅ、Ｔｅ、Ｇｅ、Ｓｎ、Ｐｂ、及びＩｎからなる群から選ばれる少なくとも一種の元素である）のモル比が、１－ｘ－ｙ：ｘ：ｙの混合比（但し、０．０３≦ｘ≦０．９５、０．００≦ｙ≦０．２０である）となるように、Ｂｉ金属単体、Ｓｂ金属単体、Ｍ金属単体、またはこれらの金属のうち少なくとも２種の金属からなる、合金、金属間化合物、もしくは固溶体を混合した、金属組成物を得る工程１と、
前記金属組成物を加圧して、合金前駆体を得る工程２と、
前記合金前駆体を、温度３５３Ｋ～５７３Ｋ、及び圧力５ＭＰａ～１００ＭＰａの条件で加熱及び加圧して、合金を得る、第１の加熱加圧工程３と、
前記合金を、前記第１の加熱加圧工程よりも低い温度及び低い圧力下におく工程４と、
工程４の後、前記合金を、温度３５３Ｋ～５７３Ｋ、及び圧力５ＭＰａ～１００ＭＰａの条件で加熱及び加圧する、第２の加熱加圧工程と、
を備える、合金の製造方法。That is, the present invention provides the inventions of the following aspects.
Item 1. Composition formula: Bi 1-xy Sb x My ( In the formula, M is from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Se, Te, Ge, Sn, Pb, and In. At least one element of choice, represented by 0.03 ≤ x ≤ 0.95, 0.00 ≤ y ≤ 0.20), with at least one of a plurality of dislocations and a plurality of twins in the crystal. Has an alloy.
Item 2. Item 2. The alloy according to Item 1, which has a thermal conductivity of 4.00 W / m · K or less at a temperature of 300 K.
Item 3. Composition formula: Bi 1-xy Sb x My ( In the formula, M is from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Se, Te, Ge, Sn, Pb, and In. It is at least one element selected, and is represented by 0.03 ≦ x ≦ 0.95, 0.00 ≦ y ≦ 0.20).
An alloy having a thermal conductivity of 4.00 W / m · K or less at a temperature of 300 K.
Item 4. Item 2. The alloy according to any one of Items 1 to 3, which has an electrical resistivity of 5.00 mΩcm or less at a temperature of 80 K.
Item 5. A thermoelectric conversion material comprising the alloy according to any one of Items 1 to 4.
Item 6. A thermoelectric conversion module comprising the thermoelectric conversion material according to Item 5.
Item 7. Bi, Sb, and M (where M is at least one element selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Se, Te, Ge, Sn, Pb, and In. The molar ratio of 1) is 1-x-y: x: y (however, 0.03 ≦ x ≦ 0.95 and 0.00 ≦ y ≦ 0.20). Step 1 to obtain a metal composition obtained by mixing an alloy, an intermetal compound, or a solid solution composed of a simple substance of Bi metal, a simple substance of Sb metal, a simple substance of M metal, or at least two kinds of metals among these metals.
Step 2 of pressurizing the metal composition to obtain an alloy precursor, and
The first heating and pressurizing step 3 in which the alloy precursor is heated and pressurized under the conditions of a temperature of 353K to 573K and a pressure of 5MPa to 100MPa to obtain an alloy,
Step 4 of placing the alloy under a temperature and pressure lower than that of the first heating and pressurizing step, and
After the step 4, the second heating and pressurizing step of heating and pressurizing the alloy under the conditions of a temperature of 353K to 573K and a pressure of 5MPa to 100MPa,
A method of manufacturing an alloy.

本発明によれば、組成式：Ｂｉ1-x-yＳｂxＭy（式中、Ｍは、Ｔｉ、Ｖ、Ｃｒ、Ｍｎ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ｓｅ、Ｔｅ、Ｇｅ、Ｓｎ、Ｐｂ、及びＩｎからなる群から選ばれる少なくとも一種の元素であり、０．０３≦ｘ≦０．９５、０．００≦ｙ≦０．２０である）で表され、結晶内に、複数の転位及び双晶の少なくとも一方を有していることから、温度３００Ｋ程度の環境での熱伝導度が低く、かつ、８０Ｋ程度の低温下での電気抵抗率が低い、優れた熱電変換特性を示す、新規な合金を提供することができる。According to the present invention, the composition formula: Bi 1-xy Sb x My ( in the formula, M is Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Se, Te, Ge, Sn, Pb, It is at least one element selected from the group consisting of and In, and is represented by 0.03 ≦ x ≦ 0.95, 0.00 ≦ y ≦ 0.20), and has a plurality of rearrangements and twins in the crystal. Since it has at least one of the crystals, it has low thermal conductivity in an environment with a temperature of about 300 K and low electrical resistivity at a low temperature of about 80 K, and exhibits excellent thermoelectric conversion characteristics. Alloys can be provided.

また、本発明によれば、組成式：Ｂｉ1-x-yＳｂxＭy（式中、Ｍは、Ｔｉ、Ｖ、Ｃｒ、Ｍｎ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ｓｅ、Ｔｅ、Ｇｅ、Ｓｎ、Ｐｂ、及びＩｎからなる群から選ばれる少なくとも一種の元素であり、０．０３≦ｘ≦０．９５、０．００≦ｙ≦０．２０である）で表され、温度３００Ｋにおいて、４．００Ｗ／ｍ・Ｋ以下の熱伝導度を有する新規な合金を提供することもできる。Further, according to the present invention, the composition formula: Bi 1-xy Sb x My ( in the formula, M is Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Se, Te, Ge, Sn, It is at least one element selected from the group consisting of Pb and In, and is represented by 0.03 ≦ x ≦ 0.95 and 0.00 ≦ y ≦ 0.20), and is 4.00 W at a temperature of 300 K. It is also possible to provide a novel alloy having a thermal conductivity of / m · K or less.

さらに、本発明によれば、上記新規な合金の製造方法、当該合金からなる熱電変換材料、当該熱電変換材料を用いた熱電変換モジュールを提供することもできる。本発明の合金からなる熱電変換材料は、組成及び温度に応じて、ｎ型またはｐ型の熱電変換材料として使用することができる。具体的には、本発明の合金は、上記のような低い電気抵抗率と熱伝導度を有しているため、例えば８０Ｋ～３００Ｋ程度の温度域において、優れた発電性能及び冷却性能を発揮するｎ型またはｐ型熱電変換材料とすることができる。さらに、ｎ型またはｐ型熱電変換材料を、熱電変換モジュールにおいて、ｎ型またはｐ型熱電変換素子として、システム中に組み込むことにより、これまで海水などに熱交換によって廃棄されていた、液化天然ガスからの冷熱エネルギーを有効に利用することが可能となり、モジュールに通電することで１００Ｋ付近まで冷却が可能な固体冷却デバイスとして利用することが可能となる。 Further, according to the present invention, it is also possible to provide a method for producing the above-mentioned novel alloy, a thermoelectric conversion material made of the alloy, and a thermoelectric conversion module using the thermoelectric conversion material. The thermoelectric conversion material made of the alloy of the present invention can be used as an n-type or p-type thermoelectric conversion material depending on the composition and temperature. Specifically, since the alloy of the present invention has the low electrical resistivity and thermal conductivity as described above, it exhibits excellent power generation performance and cooling performance in a temperature range of, for example, about 80K to 300K. It can be an n-type or p-type thermoelectric conversion material. Further, by incorporating an n-type or p-type thermoelectric conversion material into a system as an n-type or p-type thermoelectric conversion element in a thermoelectric conversion module, liquefied natural gas that has been wasted by heat exchange with seawater or the like until now. It becomes possible to effectively utilize the cold energy from the above, and it becomes possible to use it as a solid cooling device capable of cooling to around 100 K by energizing the module.

本発明の合金をｐ型及びｎ型熱電変換材料として用いた熱電変換モジュールの模式図の一例である。This is an example of a schematic diagram of a thermoelectric conversion module using the alloy of the present invention as a p-type and n-type thermoelectric conversion material. 実施例１で得られた合金（焼結体）について、室温で測定した粉末Ｘ線回折パターンを示すグラフである。It is a graph which shows the powder X-ray diffraction pattern measured at room temperature about the alloy (sintered body) obtained in Example 1. FIG. ゼーベック係数、電気抵抗率、及び熱伝導度を計測する試料ホルダーと配線の概略を示す模式図の一例である。It is an example of a schematic diagram showing the outline of a sample holder and wiring for measuring Seebeck coefficient, electrical resistivity, and thermal conductivity. 図４の（ａ）は、実施例１（ｉ）と比較例１（ｉｉ）で得られた合金（焼結体）について、図４の（ｂ）は、実施例４５（ｉｉｉ）と比較例２（ｉｖ）で得られた合金（焼結体）について、それぞれ、温度８０Ｋ～３００Ｋにおけるゼーベック係数の温度依存性を示すグラフである。FIG. 4A shows an alloy (sintered body) obtained in Example 1 (i) and Comparative Example 1 (ii), and FIG. 4B shows a comparative example with Example 45 (iii). 2 is a graph showing the temperature dependence of the Seebeck coefficient at temperatures of 80K to 300K for each of the alloys (sintered bodies) obtained in 2 (iv). 図５の（ａ）は、実施例１（ｉ）と比較例１（ｉｉ）で得られた合金（焼結体）について、図５の（ｂ）は、実施例４５（ｉｉｉ）と比較例２（ｉｖ）で得られた合金（焼結体）について、温度８０Ｋ～３００Ｋにおける電気抵抗率の温度依存性を示すグラフである。FIG. 5A shows an alloy (sintered body) obtained in Example 1 (i) and Comparative Example 1 (ii), and FIG. 5B shows a comparative example with Example 45 (iii). It is a graph which shows the temperature dependence of the electrical resistivity in the temperature 80K-300K about the alloy (sintered body) obtained in 2 (iv). 図６の（ａ）は、実施例１（ｉ）と比較例１（ｉｉ）で得られた合金（焼結体）について、図６の（ｂ）は、実施例４５（ｉｉｉ）と比較例２（ｉｖ）で得られた合金（焼結体）について、それぞれ、温度８０Ｋ～３００Ｋにおける熱伝導度の温度依存性を示すグラフである。FIG. 6A shows an alloy (sintered body) obtained in Example 1 (i) and Comparative Example 1 (ii), and FIG. 6B shows a comparative example with Example 45 (iii). 2 is a graph showing the temperature dependence of thermal conductivity at temperatures of 80K to 300K for each of the alloys (sintered bodies) obtained in 2 (iv). 実施例１（ｉ）と比較例１（ｉｉ）で得られた合金（焼結体）の透過型電子顕微鏡写真である（図７の写真（ｉ）において、（ａ）は転位の箇所を示し、（ｂ）は双晶の箇所を示す）。It is a transmission electron micrograph of the alloy (sintered body) obtained in Example 1 (i) and Comparative Example 1 (ii) (in the photograph (i) of FIG. 7, (a) shows the dislocation location. , (B) indicate the location of twins).

本発明の第１の合金は、組成式：Ｂｉ1-x-yＳｂxＭy（式中、Ｍは、Ｔｉ、Ｖ、Ｃｒ、Ｍｎ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ｓｅ、Ｔｅ、Ｇｅ、Ｓｎ、Ｐｂ、及びＩｎからなる群から選ばれる少なくとも一種の元素であり、０．０３≦ｘ≦０．９５、０．００≦ｙ≦０．２０である）で表され、かつ、結晶内に、複数の転位及び複数の双晶の少なくとも一方を有することを特徴としている。The first alloy of the present invention has a composition formula: Bi 1-xy Sb x My ( in the formula, M is Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Se, Te, Ge, Sn. , Pb, and In, at least one element selected from the group, 0.03 ≦ x ≦ 0.95, 0.00 ≦ y ≦ 0.20), and in the crystal. It is characterized by having at least one of a plurality of dislocations and a plurality of twins.

さらに、本発明の第２の合金は、組成式：Ｂｉ1-x-yＳｂxＭy（式中、Ｍは、Ｔｉ、Ｖ、Ｃｒ、Ｍｎ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ｓｅ、Ｔｅ、Ｇｅ、Ｓｎ、Ｐｂ、及びＩｎからなる群から選ばれる少なくとも一種の元素であり、０．０３≦ｘ≦０．９５、０．００≦ｙ≦０．２０である）で表され、かつ、温度３００Ｋにおいて、４．００Ｗ／ｍ・Ｋ以下の熱伝導度を有することを特徴としている。Further, the second alloy of the present invention has a composition formula: Bi 1-xy Sb x My ( where M is Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Se, Te, Ge). , Sn, Pb, and In, at least one element selected from the group, 0.03 ≦ x ≦ 0.95, 0.00 ≦ y ≦ 0.20), and a temperature of 300K. Is characterized by having a thermal conductivity of 4.00 W / m · K or less.

以下、本発明の合金について、詳述する。 Hereinafter, the alloy of the present invention will be described in detail.

本発明の合金は、組成式：Ｂｉ1-x-yＳｂxＭyで表される組成を有している。組成式中において、Ｍは、Ｔｉ、Ｖ、Ｃｒ、Ｍｎ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ｓｅ、Ｔｅ、Ｇｅ、Ｓｎ、Ｐｂ、及びＩｎからなる群から選ばれる少なくとも一種の元素である。本発明の合金は、Ｍを有していなくてもよい（すなわち、ｙ＝０）。また、合金中に含まれる金属Ｍの種類としては、０～５種類であることが好ましく、０～３種類であることがより好ましく、０～１種類であることが更に好ましい。The alloy of the present invention has a composition represented by the composition formula : Bi 1-xy Sb x My. In the composition formula, M is at least one element selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Se, Te, Ge, Sn, Pb, and In. The alloy of the present invention may not have M (ie, y = 0). The type of the metal M contained in the alloy is preferably 0 to 5, more preferably 0 to 3, and even more preferably 0 to 1.

Ｍとしては、上記のものであれば特に制限されないが、好ましくはＰｂ、Ｓｎ、Ｉｎ、Ｇｅなどが挙げられる。 The M is not particularly limited as long as it is the above, but preferably Pb, Sn, In, Ge and the like can be mentioned.

本発明の合金は、母物質であるＢｉの元素位置に必須元素であるＳｂ、さらに任意元素であるＭが置換された状態であり、Ｂｉと同様の菱面晶（三方晶）系（空間群Ｒ＿３ｍ）の結晶構造を有する金属化合物（金属材料）である。後述の通り、当該合金は、金属単体などを加熱、加圧して製造されるため、焼結体ともいえる。 The alloy of the present invention is in a state in which Sb, which is an essential element, and M, which is an optional element, are substituted at the element positions of Bi, which is the parent material, and is a rhombic crystal (trigonal) system (spatial group) similar to Bi. It is a metal compound (metal material) having a crystal structure of R_3m). As will be described later, the alloy can be said to be a sintered body because it is manufactured by heating and pressurizing a simple substance of metal or the like.

本発明の合金は、組成（すなわち、Ｂｉ結晶に対するＳｂ及びＭの置換量や、Ｍの種類）、さらに、使用温度条件に調整することにより、負のゼーベック係数を有したり、正のゼーベック係数を有する。すなわち、組成と温度条件を適宜調整することにより、ゼーベック係数の正負を制御することができる。例えば、合金の両端に温度差を生じさせた場合に、負のゼーベック係数を示す場合、熱起電力により生じる電位は、高温側の方が低温側に比べて高くなり、ｎ型熱電変換材料としての特性を示す。一方、正のゼーベック係数を示す場合、熱起電力により生じる電位は、低温側の方が高温側に比べて高くなり、ｐ型熱電変換材料としての特性を示す。 The alloy of the present invention has a negative Seebeck coefficient or a positive Seebeck coefficient by adjusting the composition (that is, the amount of substitution of Sb and M with respect to the Bi crystal and the type of M) and the operating temperature condition. Have. That is, the positive or negative of the Seebeck coefficient can be controlled by appropriately adjusting the composition and the temperature conditions. For example, when a negative Seebeck coefficient is exhibited when a temperature difference is generated at both ends of the alloy, the potential generated by the thermoelectromotive force is higher on the high temperature side than on the low temperature side, and as an n-type thermoelectric conversion material. Shows the characteristics of. On the other hand, when the positive Seebeck coefficient is shown, the potential generated by the thermoelectromotive force is higher on the low temperature side than on the high temperature side, and exhibits the characteristics as a p-type thermoelectric conversion material.

本発明の第１の合金は、結晶内に、複数の転位及び複数の双晶の少なくとも一方を有する。ここで、本発明において、結晶内の転位とは、結晶面のずれによる線状の格子欠陥を意味する。また、本発明において、結晶内の双晶とは、異なる結晶が、結晶軸方位で接合したものを意味する。本発明の第１の合金においては、結晶内に転位や双晶を有することにより、熱を伝達するフォノンを効果的に散乱するため、例えば３００Ｋにおける熱伝導度が効果的に低下され、４．００Ｗ／ｍ・Ｋ以下である。また、結晶内の転位や双晶は、電気抵抗率に対する影響が小さいため、本発明の第１の合金は、例えば８０Ｋという低温下における電気抵抗率についても、５．００ｍΩｃｍ以下という低い値を示している。 The first alloy of the present invention has at least one of a plurality of dislocations and a plurality of twins in the crystal. Here, in the present invention, the dislocation in the crystal means a linear lattice defect due to the displacement of the crystal plane. Further, in the present invention, the twin crystal in the crystal means a crystal in which different crystals are joined in the crystal axis orientation. In the first alloy of the present invention, by having dislocations and twins in the crystal, phonons that transfer heat are effectively scattered, so that the thermal conductivity at, for example, 300K is effectively reduced. It is 00 W / m · K or less. Further, since dislocations and twins in the crystal have a small effect on the electrical resistivity, the first alloy of the present invention shows a low value of 5.00 mΩcm or less even at a low temperature of 80 K, for example. ing.

合金の熱電変換特性をより一層高める観点からは、本発明の合金の温度３００Ｋにおける熱伝導度としては、好ましくは４．００Ｗ／ｍ・Ｋ以下、より好ましくは３．００Ｗ／ｍ・Ｋ以下、さらに好ましくは２．５０Ｗ／ｍ・Ｋ以下が挙げられる。 From the viewpoint of further enhancing the thermoelectric conversion characteristics of the alloy, the thermal conductivity of the alloy of the present invention at a temperature of 300 K is preferably 4.00 W / m · K or less, more preferably 3.00 W / m · K or less. More preferably, it is 2.50 W / m · K or less.

また、同様の観点から、本発明の合金の温度８０Ｋにおける熱伝導度としては、好ましくは３．５０Ｗ／ｍ・Ｋ以下、より好ましくは２．５０Ｗ／ｍ・Ｋ以下、さらに好ましくは１．９５Ｗ／ｍ・Ｋ以下が挙げられる。 From the same viewpoint, the thermal conductivity of the alloy of the present invention at a temperature of 80 K is preferably 3.50 W / m · K or less, more preferably 2.50 W / m · K or less, still more preferably 1.95 W. / M · K or less can be mentioned.

さらに、同様の観点から、本発明の合金の温度８０Ｋにおける電気抵抗率としては、好ましくは５．００ｍΩｃｍ以下、より好ましくは１．００ｍΩｃｍ以下、さらに好ましくは０．６０ｍΩｃｍ以下が挙げられる。 Further, from the same viewpoint, the electrical resistivity of the alloy of the present invention at a temperature of 80 K is preferably 5.00 mΩcm or less, more preferably 1.00 mΩcm or less, still more preferably 0.60 mΩcm or less.

また、同様の観点から、本発明の合金の３００Ｋにおける電気抵抗率としては、好ましくは２．５０ｍΩｃｍ以下、より好ましくは１．００ｍΩｃｍ以下、さらに好ましくは０．５０ｍΩｃｍ以下が挙げられる。 From the same viewpoint, the electrical resistivity of the alloy of the present invention at 300K is preferably 2.50 mΩcm or less, more preferably 1.00 mΩcm or less, still more preferably 0.50 mΩcm or less.

本発明の合金は、熱電変換材料として好適に使用することができる。前述の通り、本発明の合金は、組成や、使用環境における温度条件を調整することにより、ｎ型熱電変換材料とすることも、ｐ型熱電変換材料とすることもできる。 The alloy of the present invention can be suitably used as a thermoelectric conversion material. As described above, the alloy of the present invention can be an n-type thermoelectric conversion material or a p-type thermoelectric conversion material by adjusting the composition and the temperature conditions in the usage environment.

さらに、本発明の合金からなる熱電変換材料を複数組み合わせることによって、熱電変換材料をｎ型またはｐ型熱電変換素子とし、これらを用いて熱電変換モジュールとすることができる。このような熱電変換モジュールの模式図の一例を図１に示す。図１に示される熱電変換モジュールの構造は、公知の熱電変換モジュールの構造と同様であり、基板材料、ｐ型熱電変換材料、ｎ型熱電変換材料、電極等により構成されている。 Further, by combining a plurality of thermoelectric conversion materials made of the alloy of the present invention, the thermoelectric conversion material can be an n-type or p-type thermoelectric conversion element, and these can be used to form a thermoelectric conversion module. An example of a schematic diagram of such a thermoelectric conversion module is shown in FIG. The structure of the thermoelectric conversion module shown in FIG. 1 is the same as that of a known thermoelectric conversion module, and is composed of a substrate material, a p-type thermoelectric conversion material, an n-type thermoelectric conversion material, electrodes, and the like.

より具体的には、本発明の合金は、上記のような低い電気抵抗率と熱伝導度を有しているため、例えば８０Ｋ～３００Ｋ程度の温度域において、優れた発電性能及び冷却性能を発揮するｎ型またはｐ型熱電変換材料とすることができる。さらに、ｎ型またはｐ型熱電変換材料を、熱電変換モジュールにおいて、ｎ型またはｐ型熱電変換素子として、システム中に組み込むことにより、例えば、これまで海水などに熱交換によって廃棄されていた、液化天然ガスからの冷熱エネルギーを有効に利用することが可能となり、モジュールに通電することで１００Ｋ付近まで冷却が可能な固体冷却デバイスとして利用することが可能となる。 More specifically, since the alloy of the present invention has the low electrical resistivity and thermal conductivity as described above, it exhibits excellent power generation performance and cooling performance in a temperature range of, for example, about 80K to 300K. It can be an n-type or p-type thermoelectric conversion material. Further, by incorporating the n-type or p-type thermoelectric conversion material into the system as an n-type or p-type thermoelectric conversion element in the thermoelectric conversion module, for example, liquefaction that has been previously discarded by heat exchange in seawater or the like. It is possible to effectively use the cold energy from natural gas, and it is possible to use it as a solid cooling device that can cool down to around 100K by energizing the module.

本発明の合金の製造方法は、特に制限されず、例えば、以下の工程１～５を備える方法によって、好適に製造することができる。 The method for producing the alloy of the present invention is not particularly limited, and for example, it can be suitably produced by a method including the following steps 1 to 5.

工程１：Ｂｉ、Ｓｂ、及びＭ（ただし、Ｍは、Ｔｉ、Ｖ、Ｃｒ、Ｍｎ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ｓｅ、Ｔｅ、Ｇｅ、Ｓｎ、Ｐｂ、及びＩｎからなる群から選ばれる少なくとも一種の元素である）のモル比が、１－ｘ－ｙ：ｘ：ｙの混合比（但し、０．０３≦ｘ≦０．９５、０．００≦ｙ≦０．２０である）となるように、Ｂｉ金属単体、Ｓｂ金属単体、Ｍ金属単体、またはこれらの金属のうち少なくとも２種の金属からなる、合金、金属間化合物、もしくは固溶体を混合した、金属組成物を得る工程
工程２：工程１で得られた金属組成物を加圧して、合金前駆体を得る工程
工程３：工程２で得た合金前駆体を、温度３５３Ｋ～５７３Ｋ、及び圧力５ＭＰａ～１００ＭＰａの条件で加熱及び加圧して、合金を得る、第１の加熱加圧工程
工程４：工程３で得られた合金を、第１の加熱加圧工程よりも低い温度及び低い圧力下におく工程
工程５：工程４の後、合金を、温度３５３Ｋ～５７３Ｋ、及び圧力５ＭＰａ～１００ＭＰａの条件で加熱及び加圧する、第２の加熱加圧工程Step 1: Bi, Sb, and M (where M is at least selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Se, Te, Ge, Sn, Pb, and In. The molar ratio of (a kind of element) is a mixture ratio of 1-xy: x: y (provided that 0.03 ≦ x ≦ 0.95 and 0.00 ≦ y ≦ 0.20). Step 2: Obtaining a metal composition obtained by mixing an alloy, an intermetal compound, or a solid solution composed of a single Bi metal, a single Sb metal, a single M metal, or at least two of these metals. Step 3: The alloy precursor obtained in Step 2 is heated and pressurized under the conditions of a temperature of 353K to 573K and a pressure of 5MPa to 100MPa. First heating and pressurizing step to obtain an alloy Step 4: The alloy obtained in Step 3 is placed at a lower temperature and lower pressure than in the first heating and pressurizing step Step 5: After Step 4. , A second heating and pressurizing step of heating and pressurizing the alloy under the conditions of a temperature of 353K to 573K and a pressure of 5MPa to 100MPa.

まず、工程１においては、目的とする合金組成と同一の組成となるようにして、Ｂｉ、Ｓｂ、及びＭの原料を用意し、これらの原料を混合して金属組成物を得る。原料としては、Ｂｉ金属単体、Ｓｂ金属単体、Ｍ金属単体の他、これらの金属のうち少なくとも２種の金属からなる、合金、金属間化合物、もしくは固溶体が挙げられる。原料の形態としては、特に制限されないが、粉末の形態であることが好ましい。 First, in step 1, raw materials of Bi, Sb, and M are prepared so as to have the same composition as the target alloy composition, and these raw materials are mixed to obtain a metal composition. Examples of the raw material include a simple substance of Bi metal, a simple substance of Sb metal, a simple substance of M metal, and an alloy, an intermetal compound, or a solid solution composed of at least two kinds of these metals. The form of the raw material is not particularly limited, but is preferably in the form of powder.

次に、工程２においては、工程１で得られた金属組成物を加圧して、合金前駆体を得る。金属組成物の加圧方法としては、特に制限されず、メカニカルアロイング法や、熔融または固相反応させる方法が挙げられる。メカニカルアロイング法は、例えば、金属組成物を瑪瑙やステンレス製の容器内に入れ、容器と同材質でできた、任意の直径（例えば、２ｍｍ～２ｃｍ程度）を有する球体を適宜の個数入れ、容器を回転、振幅させることで、球体と金属組成物（好ましくは粉末）との間や、球体同士の衝突エネルギーを利用して合金化する方法である。また、熔融または固相反応させる方法においては、金属組成物として、粉末状、粒状、板状など形態のものを用いることができる。工程２は、真空中や、アルゴンなどの不活性ガス下で行うことが好ましい。 Next, in step 2, the metal composition obtained in step 1 is pressurized to obtain an alloy precursor. The pressurizing method of the metal composition is not particularly limited, and examples thereof include a mechanical alloying method and a method of melting or solid-phase reaction. In the mechanical alloying method, for example, a metal composition is placed in a container made of amber or stainless steel, and an appropriate number of spheres made of the same material as the container and having an arbitrary diameter (for example, about 2 mm to 2 cm) are placed. This is a method of alloying a container between a sphere and a metal composition (preferably powder) by rotating and oscillating the container, or by utilizing the collision energy between the spheres. Further, in the method of melting or solid-phase reaction, the metal composition may be in the form of powder, granule, plate or the like. The step 2 is preferably performed in vacuum or under an inert gas such as argon.

次に、工程３においては、工程２で得られた合金前駆体を、温度３５３Ｋ～５７３Ｋ、及び圧力５ＭＰａ～１００ＭＰａの条件で加熱及び加圧して、合金を得る、第１の加熱加圧工程を行う。このとき、工程３に供する合金前駆体は、粉末状であることが好ましい。加熱及び加圧は、例えば、粉末状の合金前駆体を、一軸加圧により板状（例えば円板状）に成型した後、当該板をカーボン製の鋳型に入れ、板の面に加圧軸が垂直になるよう、圧力５ＭＰａ～１００ＭＰａの条件で加圧し、その状態で温度３５３Ｋ～５７３Ｋで加熱し、合金前駆体を焼結して合金化させる方法が挙げられる。 Next, in step 3, the first heating and pressurizing step of heating and pressurizing the alloy precursor obtained in step 2 under the conditions of a temperature of 353K to 573K and a pressure of 5MPa to 100MPa to obtain an alloy is performed. conduct. At this time, the alloy precursor used in step 3 is preferably in the form of powder. For heating and pressurization, for example, a powdery alloy precursor is molded into a plate shape (for example, a disk shape) by uniaxial pressurization, the plate is placed in a carbon mold, and a pressurizing shaft is applied to the surface of the plate. A method of pressurizing under the condition of a pressure of 5 MPa to 100 MPa and heating at a temperature of 353 K to 573 K in that state to sinter the alloy precursor and alloying the alloy precursor can be mentioned.

工程３における加熱、加圧の方法としては、特に制限されないが、例えば、発熱体からの伝熱により加熱するホットプレス法、カーボン製の鋳型に通電し、電気抵抗による発熱で加熱する通電焼結法などが挙げられる。 The method of heating and pressurizing in step 3 is not particularly limited, but for example, a hot press method of heating by heat transfer from a heating element, an energization sintering method in which a carbon mold is energized and heated by heat generated by electric resistance. The law etc. can be mentioned.

工程３における加熱温度としては、好ましくは４４３Ｋ～５０３Ｋ程度が挙げられる。また、圧力としては、好ましくは１０ＭＰａ～８０ＭＰａ程度が挙げられる。さらに、加熱加圧する時間としては、特に制限されないが、好ましくは５分間～６０分間程度、より好ましくは１０分間～３０分間程度が挙げられる。 The heating temperature in the step 3 is preferably about 443K to 503K. The pressure is preferably about 10 MPa to 80 MPa. Further, the time for heating and pressurizing is not particularly limited, but is preferably about 5 to 60 minutes, and more preferably about 10 to 30 minutes.

工程３は、アルゴンなどの不活性ガス下で行うことが好ましい。 Step 3 is preferably carried out under an inert gas such as argon.

次に、工程４においては、工程３で得られた合金を、工程３の第１の加熱加圧工程よりも低い温度及び低い圧力下におく。このときの温度としては、特に制限されないが、好ましくは２８３Ｋ～３５３Ｋ程度、より好ましくは２９３Ｋ～３１３Ｋ程度が挙げられる。また、このときの圧力としては、好ましくは大気圧（０．１ＭＰａ程度）～１ＭＰａ程度、より好ましくは大気圧～０．２ＭＰａ程度が挙げられる。また、工程３の第１の加熱加圧工程よりも低い温度及び低い圧力下におく期間としては、特に制限されないが、好ましくは１時間～７２時間程度、より好ましくは１時間～２４時間程度が挙げられる。なお、典型的には、工程３で得られた合金を、常温（２５℃程度）、常圧下におき、合金が常温になるまで自然冷却させて、後述の工程５の第２の加熱加圧工程を行うことができる。 Next, in step 4, the alloy obtained in step 3 is placed at a lower temperature and lower pressure than in the first heating and pressurizing step of step 3. The temperature at this time is not particularly limited, but is preferably about 283K to 353K, and more preferably about 293K to 313K. The pressure at this time is preferably about atmospheric pressure (about 0.1 MPa) to about 1 MPa, and more preferably about atmospheric pressure to about 0.2 MPa. The period of keeping the temperature and pressure lower than that of the first heating and pressurizing step of the step 3 is not particularly limited, but is preferably about 1 hour to 72 hours, more preferably about 1 hour to 24 hours. Can be mentioned. Typically, the alloy obtained in step 3 is placed at room temperature (about 25 ° C.) under normal pressure and naturally cooled until the alloy reaches room temperature, and then the second heating and pressurizing in step 5 described later is performed. The process can be performed.

次に、工程５においては、工程４の後、合金を、温度３５３Ｋ～５７３Ｋ、及び圧力５ＭＰａ～１００ＭＰａの条件で加熱及び加圧する、第２の加熱加圧工程を行う。当該工程５を行うことにより、本発明の合金を好適に製造することができる。 Next, in step 5, after step 4, a second heating and pressurizing step of heating and pressurizing the alloy under the conditions of a temperature of 353K to 573K and a pressure of 5MPa to 100MPa is performed. By performing the step 5, the alloy of the present invention can be suitably produced.

工程５の第２の加熱加圧工程においては、工程４で冷却された合金を、温度３５３Ｋ～５７３Ｋ、及び圧力５ＭＰａ～１００ＭＰａの条件で、再び加熱及び加圧する。第２の加熱加圧工程は、工程３で得られた合金を粉砕せず、合金の直径よりも１．１～２倍程度大きな物質の焼結が可能な鋳型にいれて加熱、加圧を行うことが好ましい。これにより、合金が塑性変形しやすく、直径が大きくなり、厚さは薄くなり、結晶内に複数の転位及び複数の双晶の少なくとも一方を有する合金が好適に得られる。 In the second heating and pressurizing step of the step 5, the alloy cooled in the step 4 is heated and pressurized again under the conditions of a temperature of 353K to 573K and a pressure of 5MPa to 100MPa. In the second heating and pressurizing step, the alloy obtained in step 3 is not crushed, but is placed in a mold capable of sintering a substance 1.1 to 2 times larger than the diameter of the alloy and heated and pressurized. It is preferable to do so. As a result, an alloy in which the alloy is easily plastically deformed, has a large diameter, is thin in thickness, and has a plurality of dislocations and at least one of a plurality of twins in the crystal is preferably obtained.

第２の加熱加圧工程における加熱温度としては、好ましくは４４３Ｋ～５０３Ｋ程度が挙げられる。また、圧力としては、好ましくは１０ＭＰａ～８０ＭＰａ程度が挙げられる。さらに、加熱加圧する時間としては、特に制限されないが、好ましくは５分間～６０分間程度、より好ましくは１０分間～３０分間程度が挙げられる。なお、第２の加熱加圧工程における加熱温度及び圧力は、それぞれ、工程３の第１の加熱加圧工程と同じであってもよいし、異なっていてもよい。 The heating temperature in the second heating and pressurizing step is preferably about 443K to 503K. The pressure is preferably about 10 MPa to 80 MPa. Further, the time for heating and pressurizing is not particularly limited, but is preferably about 5 to 60 minutes, and more preferably about 10 to 30 minutes. The heating temperature and pressure in the second heating and pressurizing step may be the same as or different from those in the first heating and pressurizing step of step 3, respectively.

工程５における加熱、加圧の方法としては、工程３と同様の方法が挙げられる。また、工程５の後、さらに工程４及び工程５を２回以上繰り返し行ってもよい。 Examples of the heating and pressurizing methods in step 5 include the same methods as in step 3. Further, after the step 5, the steps 4 and 5 may be repeated twice or more.

工程５は、アルゴンなどの不活性ガス下で行うことが好ましい。 Step 5 is preferably carried out under an inert gas such as argon.

以下に、実施例及び比較例を示して本発明を詳細に説明する。ただし、本発明は、実施例に限定されない。 Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples. However, the present invention is not limited to the examples.

実施例１及び比較例１
Ｂｉ源、Ｓｂ源としてそれぞれビスマス金属粉末とアンチモン金属粉末（粒径１００メッシュ）を用い、Ｂｉ：Ｓｂ（元素比）＝０．８８：０．１２となるように秤量した。この粉末を容量が２５０ｃｍ3の円筒型のジルコニア（二酸化ジルコニウム）製の容器に入れた。そこへ、直径５ｍｍと１０ｍｍのジルコニア製球を原料粉末の重量に対し約１０倍重量となるよう入れた。この時、二種類の球の個数は同じであった。原料粉末と球が入った容器を、アルゴンガスを充満させたグローブボックスに入れ、密閉できる蓋を用い、容器内をアルゴン封止した。この容器を、回転機構を有する装置（フリッチュ製・Ｐｕｌｖｅｒｉｓｅｔｔｅ ６）に取り付け、毎分５００回転の回転数で混合を行った。球と容器の衝突による温度上昇を抑えるため、混合は３０分間行い、その後２０分間停止させ、さらに３０分間の混合を繰り返した。合計で１０時間３０分間混合した。この混合により、ビスマスとアンチモンの合金（本発明では合金前駆体）が作製された。なお、一般的に、この合金製造方法はメカニカルアロイング法と呼ばれている。 Example 1 and Comparative Example 1
Bismuth metal powder and antimony metal powder (particle size 100 mesh) were used as Bi source and Sb source, respectively, and weighed so that Bi: Sb (element ratio) = 0.88: 0.12. The powder was placed in a cylindrical zirconia (zirconium dioxide) container with a capacity of 250 cm 3 . Zirconia balls having diameters of 5 mm and 10 mm were placed therein so as to be about 10 times the weight of the raw material powder. At this time, the number of the two types of balls was the same. The container containing the raw material powder and the sphere was placed in a glove box filled with argon gas, and the inside of the container was sealed with argon using a sealable lid. This container was attached to a device having a rotation mechanism (Pulveristte 6 manufactured by Fritsch), and mixing was performed at a rotation speed of 500 rotations per minute. In order to suppress the temperature rise due to the collision between the sphere and the container, the mixing was carried out for 30 minutes, then stopped for 20 minutes, and the mixing was repeated for another 30 minutes. A total of 10 hours and 30 minutes was mixed. This mixing produced an alloy of bismuth and antimony (alloy precursor in the present invention). Generally, this alloy manufacturing method is called a mechanical alloying method.

次に、得られた合金粉末を、直径１０ｍｍの円板型試料を焼成できるカーボン製の鋳型に入れ、真空中、３０ＭＰａの一軸加圧を加えながら、直流電流をカーボン製の鋳型に通電し加熱した（通電焼結法）。焼成温度と時間は２００℃、５分であった。ここで得られた合金（焼結体）を、比較例１の合金とした。 Next, the obtained alloy powder was placed in a carbon mold capable of firing a disk-shaped sample having a diameter of 10 mm, and a direct current was applied to the carbon mold while applying a uniaxial pressurization of 30 MPa in a vacuum to heat the carbon mold. (Current current sintering method). The firing temperature and time were 200 ° C. and 5 minutes. The alloy (sintered body) obtained here was used as the alloy of Comparative Example 1.

次に、得られた合金を室温（約２５℃）、常圧下（約１気圧）に置き、室温程度まで自然冷却した。次に、この合金を粉砕することなく、直径１５ｍｍの円板型焼結体が作製できるカーボン製の鋳型に入れ、加圧、焼成温度、時間は先の条件と同じく、真空中、３０ＭＰａ、２００℃、５分として再度焼成した。これにより、焼結体が塑性変形し、直径が１５ｍｍまで拡大した。ここで作製された合金（焼結体）を実施例１の合金とした。 Next, the obtained alloy was placed at room temperature (about 25 ° C.) and under normal pressure (about 1 atm), and naturally cooled to about room temperature. Next, the alloy was placed in a carbon mold capable of producing a disk-shaped sintered body having a diameter of 15 mm without crushing, and the pressure, firing temperature, and time were the same as in the previous conditions, 30 MPa, 200 in vacuum. It was fired again at ° C for 5 minutes. As a result, the sintered body was plastically deformed and the diameter was expanded to 15 mm. The alloy (sintered body) produced here was used as the alloy of Example 1.

実施例１で得られた合金を、粉砕により粉末化し、Ｘ線発生源のターゲットとして銅を用いて、室温においてＸ線回折測定を行った。得られたＸ線回折パターンを図２に示す。各回折ピークのミラー指数付けにより、実施例１で得られた合金は、金属のビスマス単体と同じ菱面晶（三方晶）系の結晶系を有しており、ビスマス元素の一部がアンチモンにより置換された合金であることが確認できた。 The alloy obtained in Example 1 was pulverized by pulverization, and X-ray diffraction measurement was performed at room temperature using copper as a target of an X-ray generation source. The obtained X-ray diffraction pattern is shown in FIG. The alloy obtained in Example 1 by mirror indexing of each diffraction peak has the same rhombic crystal (trigonal) crystal system as the simple substance of metal bismuth, and a part of the bismuth element is made of antimony. It was confirmed that it was a substituted alloy.

また、実施例１及び比較例１で得られた合金についての透過型電子顕微鏡写真を図７（ｉ）及び図７（ｉｉ）に示す。図７（ｉ）において、（ａ）は結晶内の転位、（ｂ）は双晶の箇所を示している。実施例２～９２の合金についても、結晶内に同様の転位、双晶が確認された。また、実施例１～９２において、これらの転位及び双晶は、それぞれ、複数の箇所で観察された。一方、比較例１及び２では転位及び双晶はいずれも観察されなかった。 Further, transmission electron micrographs of the alloys obtained in Example 1 and Comparative Example 1 are shown in FIGS. 7 (i) and 7 (ii). In FIG. 7 (i), (a) shows dislocations in the crystal, and (b) shows twins. Similar dislocations and twins were confirmed in the crystals of the alloys of Examples 2 to 92. Further, in Examples 1 to 92, these dislocations and twins were observed at a plurality of places, respectively. On the other hand, in Comparative Examples 1 and 2, neither dislocations nor twins were observed.

実施例２～９２
表１の組成となるようにして、金属源として各金属単体の粉末を用いたこと以外は、実施例１と同様にして、合金を得た。なお、通電焼結時には、温度４５３Ｋ～５２３Ｋの範囲で熔解が起こらないよう、組成に応じて焼成温度を適宜調整した。 Examples 2-92
An alloy was obtained in the same manner as in Example 1 except that the powder of each metal alone was used as the metal source so as to have the composition shown in Table 1. At the time of energization sintering, the firing temperature was appropriately adjusted according to the composition so that melting did not occur in the temperature range of 453K to 523K.

実施例２～９２で得られた各合金についても、実施例１と同様にしてＸ線回折分析を行った。その結果、いずれも、金属のビスマス単体と同じ菱面晶（三方晶）系の結晶系を有しており、ビスマス元素の一部がアンチモン及び各添加元素により置換された合金であることが確認できた。 The alloys obtained in Examples 2 to 92 were also subjected to X-ray diffraction analysis in the same manner as in Example 1. As a result, it was confirmed that all of them have the same rhombic crystal (trigonal) crystal system as the simple substance of metal bismuth, and that some of the bismuth elements are substituted with antimony and each additive element. did it.

比較例２
Ｂｉ源、Ｓｂ源、Ｐｂ源としてそれぞれビスマス金属粉末、アンチモン金属粉末、及び鉛金属粉末（粒径１００メッシュ）を用い、Ｂｉ：Ｐｂ：Ｓｂ（元素比）＝０．７７：０．０５：０．１８となるように秤量した。これらの粉末を、容量が２５０ｃｍ3の円筒型のジルコニア（二酸化ジルコニウム）製の容器に入れた。そこへ、直径５ｍｍと１０ｍｍのジルコニア製球を原料粉末の重量に対し約１０倍重量となるよう入れた。この時、二種類の球の個数は同じであった。原料粉末と球が入った容器を、アルゴンガスを充満させたグローブボックスに入れ、密閉できる蓋を用い、容器内をアルゴン封止した。この容器を、回転機構を有する装置（フリッチュ製・Ｐｕｌｖｅｒｉｓｅｔｔｅ ６）に取り付け、毎分５００回転の回転数で混合を行った。球と容器の衝突による温度上昇を抑えるため、混合は３０分間行い、その後２０分間停止させ、さらに３０分間の混合を繰り返した。合計で１０時間３０分間混合した。この混合（メカニカルアロイング法）により、ビスマスとアンチモンの合金が作製できた。合金粉末を直径１０ｍｍの円板型試料を焼成できるカーボン製の鋳型に入れ、真空中、３０ＭＰａの一軸加圧を加えながら、直流電流をカーボン製の鋳型に通電し加熱した（通電焼結法）。焼成温度と時間は２００℃、５分であった。得られた合金（焼結体）を比較例２の合金とした。 Comparative Example 2
Bismuth metal powder, antimony metal powder, and lead metal powder (particle size 100 mesh) are used as Bi source, Sb source, and Pb source, respectively, and Bi: Pb: Sb (element ratio) = 0.77: 0.05: 0. Weighed to be .18. These powders were placed in a cylindrical zirconia (zirconium dioxide) container with a capacity of 250 cm 3 . Zirconia balls having diameters of 5 mm and 10 mm were placed therein so as to be about 10 times the weight of the raw material powder. At this time, the number of the two types of balls was the same. The container containing the raw material powder and the sphere was placed in a glove box filled with argon gas, and the inside of the container was sealed with argon using a sealable lid. This container was attached to a device having a rotation mechanism (Pulveristte 6 manufactured by Fritsch), and mixing was performed at a rotation speed of 500 rotations per minute. In order to suppress the temperature rise due to the collision between the sphere and the container, the mixing was carried out for 30 minutes, then stopped for 20 minutes, and the mixing was repeated for another 30 minutes. A total of 10 hours and 30 minutes was mixed. By this mixing (mechanical alloying method), an alloy of bismuth and antimony could be produced. The alloy powder was placed in a carbon mold capable of firing a disk-shaped sample having a diameter of 10 mm, and a direct current was applied to the carbon mold while applying a uniaxial pressurization of 30 MPa in a vacuum (current sintering method). .. The firing temperature and time were 200 ° C. and 5 minutes. The obtained alloy (sintered body) was used as the alloy of Comparative Example 2.

熱電変換特性の計測
実施例１～９２及び比較例１，２で得られた各合金（試料）について、それぞれ、下記の方法でゼーベック係数、電気抵抗率、及び熱伝導度を測定した。いずれも低温計測であるため、Ｑｕａｎｔｕｍ Ｄｅｓｉｇｎ社製の物理特性測定装置（ＰＰＭＳ）のサーマルトランスポートオプション（ＴＴＯ）により、液体ヘリウムを用い測定した。結果を表１～４及び図４～６に示す。 Measurement of Thermoelectric Conversion Characteristics For each of the alloys (samples) obtained in Examples 1 to 92 and Comparative Examples 1 and 2, the Seebeck coefficient, electrical resistivity, and thermal conductivity were measured by the following methods, respectively. Since all of them are low temperature measurements, they were measured using liquid helium by the thermal transport option (TTO) of the physical characteristic measuring device (PPMS) manufactured by Quantum Design. The results are shown in Tables 1 to 4 and FIGS. 4 to 6.

・ゼーベック係数
試料を断面が約３．５ｍｍ角、長さが約８ｍｍの直方体（図３（ａ））に成形し、長さ方向の両端を試料ホルダーに導電性エポキシ系接着剤を用い固定した（同（ｂ））。一方のホルダー部には加熱用ヒーター（抵抗体）（同（ｃ））がついており、試料の両端に温度差をつけることができる。試料の両端間の二箇所（同（ｄ））に測温抵抗体（同（ｅ））と電圧計測端子（同（ｆ））を導電性エポキシ系接着剤で接続した。加熱による二点間の温度差と熱起電力を測温抵抗体と電圧計測端子で測定しゼーベック係数を得る。試料を装着した試料ホルダーは液体ヘリウムと電気ヒーターにより温度調整が可能な試料室へ入れ、８０～３００Ｋの範囲で測定を行った。表１～４には、８０Ｋ及び３００Ｋでのゼーベック係数の値を示す。-Seebeck coefficient A sample was formed into a rectangular parallelepiped (Fig. 3 (a)) with a cross section of about 3.5 mm square and a length of about 8 mm, and both ends in the length direction were fixed to the sample holder using a conductive epoxy adhesive. (Same as (b)). A heating heater (resistor) (same as (c)) is attached to one of the holder portions, and a temperature difference can be created at both ends of the sample. A resistance temperature detector (same (e)) and a voltage measuring terminal (same (f)) were connected to two places (same (d)) between both ends of the sample with a conductive epoxy adhesive. The temperature difference between two points due to heating and the thermoelectromotive force are measured with a resistance temperature detector and a voltage measurement terminal to obtain the Seebeck coefficient. The sample holder on which the sample was mounted was placed in a sample chamber whose temperature could be adjusted by liquid helium and an electric heater, and measurement was performed in the range of 80 to 300 K. Tables 1 to 4 show the values of the Seebeck coefficient at 80K and 300K.

・電気抵抗率
試料を断面が約３．５ｍｍ角、長さが約８ｍｍの直方体に成形し、上記のゼーベック係数測定と同様にサンプルホルダーに固定する。両端のホルダー部は交流電源の電流端子となる（同（ｇ））。交流電流を通電し、試料の両端間の二箇所に導電性エポキシ系接着剤で接続した電圧計測端子で電圧を計測し、位相敏感検波器（ｐｈａｓｅ－ｓｅｎｓｉｔｉｖｅ ｄｅｔｅｃｔｏｒ）を用い、微弱な電圧信号から正確な電気抵抗Ｒを計測し、さらに試料寸法（断面積Ａ、端子間距離Ｌ）から電気抵抗率ρ＝Ｒ×Ａ／Ｌを得た。表１～４には、８０Ｋ及び３００Ｋでの電気抵抗率（ｍΩｃｍ）を示す。-Electrical resistivity A sample is formed into a rectangular parallelepiped with a cross section of about 3.5 mm square and a length of about 8 mm, and fixed to the sample holder in the same manner as in the above Seebeck coefficient measurement. The holders at both ends serve as current terminals for AC power (same as (g)). An alternating current is applied, the voltage is measured at two voltage measurement terminals connected to both ends of the sample with a conductive epoxy adhesive, and a phase-sensitive detector is used to detect a weak voltage signal. The accurate electric resistance R was measured, and the electrical resistivity ρ = R × A / L was obtained from the sample dimensions (cross-sectional area A, distance between terminals L). Tables 1 to 4 show electrical resistivity (mΩcm) at 80K and 300K.

・熱伝導度
試料を断面が約３．５ｍｍ角、長さが約８ｍｍの直方体に成形し、上記のゼーベック係数測定と同様にサンプルホルダーに固定する。サンプルホルダーについた加熱用ヒーターから一定の熱量で試料を加熱し、試料の両端の間の二箇所に導電性エポキシ系接着剤で接続した測温抵抗体で温度差の経時変化を計測することで熱伝導Ｋを計算し、さらに試料寸法から熱伝導度κ＝Ｋ×Ｌ／Ａを得た。表１～４には、８０Ｋ及び３００Ｋでの熱伝導度（Ｗ／ｍ・Ｋ）を示す。-Thermal conductivity The sample is formed into a rectangular parallelepiped with a cross section of about 3.5 mm square and a length of about 8 mm, and fixed to the sample holder in the same manner as the above Seebeck coefficient measurement. By heating the sample with a constant amount of heat from the heating heater attached to the sample holder, and measuring the change over time of the temperature difference with a temperature measuring resistor connected to two places between both ends of the sample with a conductive epoxy adhesive. The thermal conductivity K was calculated, and the thermal conductivity κ = K × L / A was obtained from the sample dimensions. Tables 1 to 4 show the thermal conductivity (W / m · K) at 80K and 300K.

Figure 0007054925000001
Figure 0007054925000001

Figure 0007054925000002
Figure 0007054925000002

Figure 0007054925000003
Figure 0007054925000003

Figure 0007054925000004
Figure 0007054925000004

図４～図６に示されるように、実施例１では、ｎ型の熱電特性、実施例４５ではｐ型の熱電特性を示しており、本発明においては、合金の組成などを調整することにより、ｎ型及びｐ型のいずれの熱電変換材料にもなることが分かる。 As shown in FIGS. 4 to 6, Example 1 shows an n-type thermoelectric characteristic, and Example 45 shows a p-type thermoelectric characteristic. In the present invention, the composition of the alloy and the like are adjusted. , N-type and p-type thermoelectric conversion materials.

また、実施例１，４５においては、金属組成物を所定の温度及び圧力で加熱・加圧する第１の加熱加圧工程を行った後、合金を、第１の加熱加圧工程よりも低い温度及び低い圧力下におき、さらに、所定の温度及び圧力で加熱・加圧する第２の加熱加圧工程を行った。これに対して、実施例１，４５と同じ組成である比較例１，４５においては、第１の加熱加圧工程のみを行っている。従って、実施例１、４５の合金の方が、比較例１，２の合金よりも、密度が高められているといえる。 Further, in Examples 1 and 45, after the first heating and pressurizing step of heating and pressurizing the metal composition at a predetermined temperature and pressure is performed, the temperature of the alloy is lower than that of the first heating and pressurizing step. A second heating and pressurizing step of heating and pressurizing at a predetermined temperature and pressure was performed. On the other hand, in Comparative Examples 1 and 45 having the same composition as Examples 1 and 45, only the first heating and pressurizing step is performed. Therefore, it can be said that the alloys of Examples 1 and 45 have a higher density than the alloys of Comparative Examples 1 and 2.

すなわち、実施例１～９２においては、２回目の加熱加圧工程において、密度が高められるため、熱伝導度も高められると考える。ところが、実施例１～９２においては、３００Ｋにおける熱伝導度については、比較例１，２よりも顕著に低下している。これは、実施例１～９２においては、第１の加熱加圧工程に加えて、さらに、冷却・減圧を行った後に、第２の加熱加圧工程を行っているため、合金の結晶内に複数の転位及び双晶の少なくとも一方が形成され（図７参照）、結果として、熱伝導度が顕著に低下したと理解することができる（表１～４）。実際、比較例１、２の合金においては、結晶内に複数の転位及び双晶は観察されなかった（図７を参照）。また、例えば、図６に示されるように、実施例１、４５の合金は、それぞれ、ｎ型、ｐ型のいずれにおいても、同じ組成である比較例１，２よりも、８０Ｋ～３００Ｋにおける熱伝導度が顕著に低かった。 That is, in Examples 1 to 92, since the density is increased in the second heating and pressurizing step, it is considered that the thermal conductivity is also increased. However, in Examples 1 to 92, the thermal conductivity at 300K is significantly lower than that in Comparative Examples 1 and 2. This is because in Examples 1 to 92, in addition to the first heating and pressurizing step, the second heating and pressurizing step is performed after further cooling and depressurizing, so that the inside of the alloy crystal is contained. It can be understood that at least one of the plurality of dislocations and twins was formed (see FIG. 7), and as a result, the thermal conductivity was significantly reduced (Tables 1 to 4). In fact, in the alloys of Comparative Examples 1 and 2, a plurality of dislocations and twins were not observed in the crystals (see FIG. 7). Further, for example, as shown in FIG. 6, the alloys of Examples 1 and 45 have the same composition in both n-type and p-type, respectively, and the heat at 80K to 300K is higher than that of Comparative Examples 1 and 2. The conductivity was significantly lower.

このように、組成式：Ｂｉ1-x-yＳｂxＭy（式中、Ｍは、Ｔｉ、Ｖ、Ｃｒ、Ｍｎ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ｓｅ、Ｔｅ、Ｇｅ、Ｓｎ、Ｐｂ、及びＩｎからなる群から選ばれる少なくとも一種の元素であり、０．０３≦ｘ≦０．９５、０≦ｙ０．００≦ｙ≦０．２０である）で表され、結晶内に、複数の転位及び複数の双晶の少なくとも一方を有する合金は、温度３００Ｋの環境での熱伝導度が低く、かつ、８０Ｋの低温下での電気抵抗率が低い、優れた熱電変換特性を示すことが分かる。一方、当該組成を有しているものの、結晶内に複数の転位または双晶を有していない比較例１においては、８０Ｋの低温下での電気抵抗率が高く、温度３００Ｋの環境での熱伝導度も高く、実施例１～９２の合金に比して、熱電変換性能に劣ることが明らかとなった。また、結晶内に複数の転位または双晶を有していない比較例２の合金については、８０Ｋの低温下での電気抵抗率は低いものの、温度３００Ｋの環境での熱伝導度が高く、実施例１～９２の合金に比して、熱電変換性能に劣ることが明らかとなった。Thus, the composition formula: Bi 1-xy Sb x My ( in the formula, M is Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Se, Te, Ge, Sn, Pb, and In. It is at least one element selected from the group consisting of 0.03 ≦ x ≦ 0.95, 0 ≦ y0.00 ≦ y ≦ 0.20), and has a plurality of rearrangements and a plurality of rearrangements in the crystal. It can be seen that the alloy having at least one of the twin crystals has excellent thermal conductivity in an environment of 300 K and low electrical resistivity in a low temperature of 80 K, and exhibits excellent thermoelectric conversion characteristics. On the other hand, in Comparative Example 1 which has the composition but does not have a plurality of dislocations or twins in the crystal, the electrical resistivity at a low temperature of 80 K is high, and the heat in an environment of a temperature of 300 K is high. It was clarified that the conductivity was high and the thermoelectric conversion performance was inferior to that of the alloys of Examples 1 to 92. Further, for the alloy of Comparative Example 2 which does not have a plurality of dislocations or twins in the crystal, the electrical resistivity at a low temperature of 80 K is low, but the thermal conductivity is high in an environment of a temperature of 300 K. It was clarified that the thermoelectric conversion performance was inferior to that of the alloys of Examples 1 to 92.

Claims (4)

組成式：Ｂｉ1 -x -yＳｂxＭy（式中、Ｍは、Ｔｉ、Ｖ、Ｃｒ、Ｍｎ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ｓｅ、及びＴｅからなる群から選ばれる少なくとも一種の元素であり、０．０３≦ｘ≦０．９５、０．００≦ｙ≦０．２０である）で表され、結晶内に、複数の転位及び複数の双晶の少なくとも一方を有し、
温度３００Ｋにおいて、４．００Ｗ／ｍ・Ｋ以下の熱伝導度を有し、
温度８０Ｋにおいて、５．００ｍΩｃｍ以下の電気抵抗率を有する、焼結体。 Composition formula: Bi 1 -x -y Sb x My ( In the formula, M is at least one selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Se, and Te. It is an element of 0.03 ≦ x ≦ 0.95, 0.00 ≦ y ≦ 0.20), and has a plurality of dislocations and at least one of a plurality of twins in the crystal.
It has a thermal conductivity of 4.00 W / m · K or less at a temperature of 300 K.
A sintered body having an electrical resistivity of 5.00 mΩcm or less at a temperature of 80 K. 請求項１に記載の焼結体からなる、熱電変換材料。 A thermoelectric conversion material comprising the sintered body according to claim 1. 請求項２に記載の熱電変換材料を含む、熱電変換モジュール。 A thermoelectric conversion module comprising the thermoelectric conversion material according to claim 2. 焼結体の製造方法であって、
前記焼結体は、組成式：Ｂｉ 1 -x -y Ｓｂ x Ｍ y （式中、Ｍは、Ｔｉ、Ｖ、Ｃｒ、Ｍｎ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ｓｅ、Ｔｅ、Ｇｅ、Ｓｎ、Ｐｂ、及びＩｎからなる群から選ばれる少なくとも一種の元素であり、０．０３≦ｘ≦０．９５、０．００≦ｙ≦０．２０である）で表され、結晶内に、複数の転位及び複数の双晶の少なくとも一方を有し、温度３００Ｋにおいて、４．００Ｗ／ｍ・Ｋ以下の熱伝導度を有し、温度８０Ｋにおいて、５．００ｍΩｃｍ以下の電気抵抗率を有する焼結体であり、
Ｂｉ、Ｓｂ、及びＭ（ただし、Ｍは、Ｔｉ、Ｖ、Ｃｒ、Ｍｎ、Ｆｅ、Ｃｏ、Ｎｉ、Ｃｕ、Ｓｅ、Ｔｅ、Ｇｅ、Ｓｎ、Ｐｂ、及びＩｎからなる群から選ばれる少なくとも一種の元素である）のモル比が、１－ｘ－ｙ：ｘ：ｙの混合比（但し、０．０３≦ｘ≦０．９５、０．００≦ｙ≦０．２０である）となるように、Ｂｉ金属単体、Ｓｂ金属単体、Ｍ金属単体、またはこれらの金属のうち少なくとも２種の金属からなる、合金、金属間化合物、もしくは固溶体を混合した、金属組成物を得る工程１と、
前記金属組成物を加圧して、焼結体前駆体を得る工程２と、
前記焼結体前駆体を、温度３５３Ｋ～５７３Ｋ、及び圧力５ＭＰａ～１００ＭＰａの条件で加熱及び加圧して、焼結体を得る、第１の加熱加圧工程３と、
前記焼結体を、前記第１の加熱加圧工程よりも低い温度及び低い圧力下におく工程４と、
工程４の後、前記焼結体を、温度３５３Ｋ～５０３Ｋ、及び圧力５ＭＰａ～１００ＭＰａの条件で加熱及び加圧する、第２の加熱加圧工程と、
を備える、焼結体の製造方法。 It is a manufacturing method of a sintered body.
The sintered body has a composition formula: Bi 1 -x -y Sb x My ( in the formula, M is Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Se, Te, Ge, Sn, It is at least one element selected from the group consisting of Pb and In, and is represented by 0.03 ≦ x ≦ 0.95, 0.00 ≦ y ≦ 0.20), and a plurality of rearrangements in the crystal. And a sintered body having at least one of a plurality of twin crystals, having a thermal conductivity of 4.00 W / m · K or less at a temperature of 300 K, and an electrical resistivity of 5.00 mΩ cm or less at a temperature of 80 K. can be,
Bi, Sb, and M (where M is at least one element selected from the group consisting of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Se, Te, Ge, Sn, Pb, and In. The molar ratio of 1) is 1-x-y: x: y (however, 0.03 ≦ x ≦ 0.95 and 0.00 ≦ y ≦ 0.20). Step 1 to obtain a metal composition obtained by mixing an alloy, an intermetal compound, or a solid solution composed of a simple substance of Bi metal, a simple substance of Sb metal, a simple substance of M metal, or at least two kinds of metals among these metals.
Step 2 of pressurizing the metal composition to obtain a sintered precursor,
The first heating and pressurizing step 3 of heating and pressurizing the sintered body precursor under the conditions of a temperature of 353 K to 573 K and a pressure of 5 MPa to 100 MPa to obtain a sintered body,
Step 4 of placing the sintered body under a temperature and pressure lower than that of the first heating and pressurizing step, and
After the step 4, the second heating and pressurizing step of heating and pressurizing the sintered body under the conditions of a temperature of 353K to 503K and a pressure of 5MPa to 100MPa, and a second heating and pressurizing step.
A method for manufacturing a sintered body.
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