JP7363059B2 - Manufacturing method of thermoelectric conversion material - Google Patents
Manufacturing method of thermoelectric conversion material Download PDFInfo
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Description
本発明は、スクッデルダイト系熱電変換材料である焼結体を、容易にして且つ高密度に作製できる、熱電変換材料の製造方法に関する。 The present invention relates to a method for producing a thermoelectric conversion material, which allows a sintered body of a Scudderudite thermoelectric conversion material to be easily produced with high density.
熱電変換モジュールに用いられる熱電変換材料として、スクッデルダイト系熱電変換材料が知られている。スクッデルダイト系熱電変換材料は焼結法にて作製することができ、具体的には、ホットプレス焼結や放電プラズマ焼結等の、加圧焼結法にて作製することができる。（例えば、特許文献１、特許文献２） Scudderudite-based thermoelectric conversion materials are known as thermoelectric conversion materials used in thermoelectric conversion modules. The Scudderudite thermoelectric conversion material can be produced by a sintering method, and specifically, by a pressure sintering method such as hot press sintering or discharge plasma sintering. (For example, Patent Document 1, Patent Document 2)
特許文献１や特許文献２の製造方法では、高圧の加圧焼結により、高密度の焼結体を作製している。しかし、加圧焼結は、大量の焼結体作製には不向きであり、スクッデルダイト系熱電変換材料の焼結体を、雰囲気下焼結にて高密度に作製可能な製造方法が望まれていた。 In the manufacturing methods of Patent Document 1 and Patent Document 2, a high-density sintered body is produced by high-pressure sintering. However, pressure sintering is not suitable for producing large quantities of sintered bodies, and a manufacturing method that can produce high-density sintered bodies of skudderudite thermoelectric conversion materials by sintering in an atmosphere is desired. was.
そこで本発明では、スクッデルダイト系熱電変換材料の焼結体を、雰囲気下焼結にて高密度に作製可能な、熱電変換材料の製造方法を提供する。 Therefore, the present invention provides a method for producing a thermoelectric conversion material, which allows a sintered body of a Scudderudite-based thermoelectric conversion material to be produced at high density by sintering in an atmosphere.
本発明の熱電変換材料の製造方法は、スクッデルダイト系熱電変換材料の粉砕粉を成型して成型体とする成型工程と、前記成型体を水素雰囲気中にて６２０～６５０℃に保持して熱処理する熱処理工程と、前記熱処理後の成型体を真空雰囲気中にて８００～８７０℃に保持し、加圧焼結でない雰囲気下で焼結する焼結工程とを有する。
The method for producing a thermoelectric conversion material of the present invention includes a molding step of molding pulverized powder of a Scudderdite thermoelectric conversion material into a molded body, and a molding step in which the molded body is placed in a hydrogen atmosphere.Maintain at 620-650℃A heat treatment step and a molded body after the heat treatment in a vacuum atmosphere.Maintained at 800-870°C in an atmosphere that does not involve pressure sintering.and a sintering step of sintering.
また、本発明の熱電変換材料の製造方法では、前記熱処理工程と前記焼結工程とを、同じチャンバー内にて行い、前記熱処理工程後のチャンバー内を前記水素雰囲気から直に前記真空雰囲気にすることが好ましい。 Further, in the method for producing a thermoelectric conversion material of the present invention, the heat treatment step and the sintering step are performed in the same chamber, and the inside of the chamber after the heat treatment step is changed from the hydrogen atmosphere to the vacuum atmosphere directly. It is preferable.
本発明によれば、スクッデルダイト系熱変換材料の焼結体を、雰囲気下焼結により作製可能な、熱電変換材料の製造方法を提供することができる。 According to the present invention, it is possible to provide a method for producing a thermoelectric conversion material in which a sintered body of a Scudderudite-based heat conversion material can be produced by sintering in an atmosphere.
以下、本発明の一実施形態について、図１のフローに従って説明する。本実施形態の熱電変換材料の製造方法は、秤量工程Ｓ１、混合工程Ｓ２、リボン作製工程Ｓ３、熱処理工程Ｓ４、粉砕工程Ｓ５、プレス成型工程Ｓ６、水素雰囲気熱処理工程Ｓ７、焼結工程Ｓ８を有している。 Hereinafter, one embodiment of the present invention will be described according to the flow shown in FIG. The method for manufacturing a thermoelectric conversion material of this embodiment includes a weighing step S1, a mixing step S2, a ribbon manufacturing step S3, a heat treatment step S4, a crushing step S5, a press molding step S6, a hydrogen atmosphere heat treatment step S7, and a sintering step S8. are doing.
（Ｓ１：秤量工程）
まず、秤量工程Ｓ１では、例えば、一般的な秤量装置を用いて、Ｙｂ、Ｃｏ、Ｓｂそれぞれを含む素原料を秤量する。上記秤量には、高純度に精製された素原料を用いるのが好ましく、秤量の際には、これら素原料中に含まれる、Ｙｂ、Ｃｏ、Ｓｂの含有率を、予め調べておき、それら含有率を基に、秤量後の素原料全体に含まれる、Ｙｂ、Ｃｏ、Ｓｂの元素比が、Ｙｂ：Ｃｏ：Ｓｂ＝ｘ：４：１２（ここで、０＜ｘ≦０．３）になるように秤量するのが好ましい。
(S1: Weighing process)
First, in the weighing step S1, raw materials containing each of Yb, Co, and Sb are weighed using, for example, a general weighing device. It is preferable to use highly purified raw materials for the above weighing, and when weighing, check in advance the content of Yb, Co, and Sb contained in these raw materials. Based on the ratio, the elemental ratio of Yb, Co, and Sb contained in the entire raw material after weighing is Yb:Co:Sb=x:4:12 (here, 0<x≦0.3) It is preferable to weigh as follows.
また、上記秤量は、外気と遮断された環境下、例えば、窒素やアルゴンなどの不活性ガスを供給し、内部の酸素濃度を０．１～１００容積ｐｐｍにした密閉作業装置内で行うのが好ましい。このようにすることで、素原料の酸化を抑制することができる。 In addition, the above weighing is preferably carried out in an environment isolated from the outside air, for example, in a closed work device that is supplied with an inert gas such as nitrogen or argon and has an internal oxygen concentration of 0.1 to 100 ppm by volume. preferable. By doing so, oxidation of the raw material can be suppressed.
（Ｓ２：混合工程）
次に、混合工程Ｓ２では、秤量工程Ｓ１で秤量した素原料を、黒鉛坩堝などの耐熱性容器内にて溶融・混合する。
混合工程Ｓ２では、例えば、素原料を装填した耐熱性容器を、高周波溶解炉内にて加熱溶融し、素原料に含まれるＹｂ、Ｃｏ、Ｓｂ成分を混合する。素原料を加熱溶融する温度は、１０００℃以上にするが好ましく、より好ましくは１０５０℃以上、さらに好ましくは１１８０℃以上にするのが良い。また、Ｓｂの蒸発などを考慮して１３００℃以下が好ましい。
(S2: Mixing step)
Next, in the mixing step S2, the raw materials weighed in the weighing step S1 are melted and mixed in a heat-resistant container such as a graphite crucible.
In the mixing step S2, for example, a heat-resistant container loaded with raw materials is heated and melted in a high-frequency melting furnace to mix Yb, Co, and Sb components contained in the raw materials. The temperature at which the raw materials are heated and melted is preferably 1000°C or higher, more preferably 1050°C or higher, and even more preferably 1180°C or higher. Further, in consideration of evaporation of Sb, etc., the temperature is preferably 1300° C. or lower.
なお、素原料を加熱溶融する際には、溶融状態の保持時間は１時間程度にすることが好ましい。このようにすることで、Ｓｂの蒸発を抑制しつつ、Ｙｂ、Ｃｏ、Ｓｂの成分を十分に混合することができる。混合した素原料は、別に用意した坩堝中に注いで冷却し、Ｙｂ、Ｃｏ、Ｓｂの成分を含むインゴットにする。 In addition, when heating and melting the raw material, it is preferable that the holding time in the molten state is about 1 hour. By doing so, the components of Yb, Co, and Sb can be sufficiently mixed while suppressing the evaporation of Sb. The mixed raw materials are poured into a separately prepared crucible and cooled to form an ingot containing components of Yb, Co, and Sb.
（Ｓ３：リボン作製工程）
次に、リボン作製工程Ｓ３では、混合工程Ｓ２で作製したインゴットから、非晶質金属のリボンを作製する。
リボン作製工程Ｓ３では、まず、混合工程Ｓ２にて作製したインゴットを、黒鉛坩堝などの耐熱性容器内に装填した後、高周波加熱等により再溶融して溶湯にする。そして、上記溶湯を、回転する金属ロール上にて冷却して、非晶質金属のリボンを作製する。なお、リボンは、リボン内の組織が均一になるよう、厚さ５～５０μｍに作製するのが好ましい。また、これより後の熱が加わる工程において組成の均一化が進むため、この工程において得られるリボンは部分的に定比及び不定比組成の合金であってもよい。
(S3: Ribbon production process)
Next, in the ribbon production step S3, an amorphous metal ribbon is produced from the ingot produced in the mixing step S2.
In the ribbon production step S3, first, the ingot produced in the mixing step S2 is loaded into a heat-resistant container such as a graphite crucible, and then remelted by high frequency heating or the like to form a molten metal. Then, the molten metal is cooled on a rotating metal roll to produce an amorphous metal ribbon. Note that the ribbon is preferably manufactured to have a thickness of 5 to 50 μm so that the structure within the ribbon is uniform. Further, since the composition becomes more uniform in the subsequent step of applying heat, the ribbon obtained in this step may be partially an alloy of stoichiometric and non-stoichiometric compositions.
（Ｓ４：熱処理工程）
次に、熱処理工程Ｓ４では、リボン作製工程Ｓ３で作製したリボンを、不活性ガス雰囲気中にて熱処理する。
熱処理工程Ｓ４では、まず、リボン作製工程Ｓ３にて作製したリボンを、黒鉛坩堝などの耐熱性容器に装填し、耐熱性容器内を不活性雰囲気にしたのち容器に蓋をする。
不活性ガスとしては、例えば、窒素ガス、アルゴンガス等を用いることができ、他にも、水素とアルゴンあるいは水素と窒素の混合気体、あるいは水素の単独ガス、を用いることもできる。
(S4: Heat treatment step)
Next, in a heat treatment step S4, the ribbon produced in the ribbon production step S3 is heat treated in an inert gas atmosphere.
In the heat treatment step S4, first, the ribbon produced in the ribbon production step S3 is loaded into a heat-resistant container such as a graphite crucible, and after creating an inert atmosphere inside the heat-resistant container, the container is covered.
As the inert gas, for example, nitrogen gas, argon gas, etc. can be used, and in addition, a mixed gas of hydrogen and argon, hydrogen and nitrogen, or a single gas of hydrogen can also be used.
ここで、不活性ガス雰囲気とした耐熱性容器内の酸素濃度は、１０容積ｐｐｍ以下にするのが好ましく、５容積ｐｐｍ以下にするのがより好ましい。また、酸素濃度をより低減させるために、耐熱容器内に金属Ｔｉなどのゲッター材を装荷しても良い。 Here, the oxygen concentration in the heat-resistant container with an inert gas atmosphere is preferably 10 volume ppm or less, more preferably 5 volume ppm or less. Further, in order to further reduce the oxygen concentration, a getter material such as metal Ti may be loaded into the heat-resistant container.
また、熱処理温度は、５００～８００℃の温度範囲で行うことが好ましく、熱処理時間は、熱処理温度を７００℃にした場合には、３時間以上１６８時間未満にすることができる。 Further, the heat treatment temperature is preferably performed in a temperature range of 500 to 800°C, and the heat treatment time can be 3 hours or more and less than 168 hours when the heat treatment temperature is 700°C.
熱処理工程Ｓ４では、リボンを低酸素濃度雰囲気下で熱処理することで、リボンの表面や粒界に存在する酸素を低減させることができる。これにより、後で説明する水素雰囲気熱処理工程Ｓ７にて、より確実に酸素を還元除去することができる。 In the heat treatment step S4, the ribbon is heat treated in a low oxygen concentration atmosphere to reduce oxygen present on the surface and grain boundaries of the ribbon. Thereby, oxygen can be reduced and removed more reliably in the hydrogen atmosphere heat treatment step S7, which will be described later.
（Ｓ５：粉砕工程）
次に、粉砕工程Ｓ５では、熱処理工程Ｓ４で熱処理したリボンを粉砕する。粉砕には、例えば、乳鉢および乳棒、ボールミル、ロッドミル、高圧粉砕ロール、縦軸インパクタミル、ジェットミル、ハンマーミル等を用いることができる。
また、粉砕は、酸素濃度を０．１～１００ｐｐｍに制御した密閉作業装置内にて行うのが好ましく、焼結性を良くするために、メディアン径（ｄ５０）が、５～１００μｍの粉砕粉にするのが好ましい。このようにすることで、後工程の成型密度を高め、焼結性の良い粉砕粉にすることができる。
(S5: Grinding process)
Next, in the crushing step S5, the ribbon heat-treated in the heat treatment step S4 is crushed. For the grinding, for example, a mortar and pestle, a ball mill, a rod mill, a high-pressure grinding roll, a vertical axis impact mill, a jet mill, a hammer mill, etc. can be used.
In addition, it is preferable that the pulverization be carried out in a closed working device in which the oxygen concentration is controlled at 0.1 to 100 ppm, and in order to improve sinterability, the pulverized powder has a median diameter (d 50 ) of 5 to 100 μm. It is preferable to By doing so, it is possible to increase the molding density in the subsequent process and to obtain a pulverized powder with good sinterability.
（Ｓ６：プレス成型工程）
次に、プレス成型工程Ｓ６では、粉砕工程Ｓ５で得られた粉砕粉をプレス成型し、成型体を作製する。
プレス成型には、ダイスとパンチの一軸プレスを用いることができるが、低酸素濃度雰囲気にした密閉作業装置内にて、粉砕粉の酸素濃度増加を抑制しながら成型するのが好ましい。
(S6: Press molding process)
Next, in the press molding step S6, the pulverized powder obtained in the crushing step S5 is press molded to produce a molded body.
For press molding, a uniaxial press with a die and a punch can be used, but it is preferable to perform the molding in a closed working device with a low oxygen concentration atmosphere while suppressing an increase in the oxygen concentration of the pulverized powder.
（Ｓ７：水素雰囲気熱処理工程）
次に、水素雰囲気熱処理工程Ｓ７では、プレス成型工程Ｓ６で作製した成型体を熱処理する。
水素雰囲気熱処理工程Ｓ７では、例えば、成型体を、水素雰囲気にしたチャンバー内にて、６００℃以上の温度で熱処理する。前の粉砕工程Ｓ５において得られた粉砕粉は、粉砕前より酸素が吸着しやすくなっている。そのためこの工程を経ることで、粉砕粉の表面あるいは粒界に存在する酸素を還元除去することができ、成型体を構成する粉砕粉の表面を、より焼結しやすい状態にすることができる。これにより、好ましい粒径で、かつ焼結性を高めた成型体を実現できる。
(S7: Hydrogen atmosphere heat treatment step)
Next, in a hydrogen atmosphere heat treatment step S7, the molded body produced in the press molding step S6 is heat treated.
In the hydrogen atmosphere heat treatment step S7, for example, the molded body is heat treated at a temperature of 600° C. or higher in a hydrogen atmosphere chamber. The pulverized powder obtained in the previous pulverization step S5 adsorbs oxygen more easily than before pulverization. Therefore, by going through this step, oxygen present on the surface or grain boundaries of the pulverized powder can be reduced and removed, and the surface of the pulverized powder constituting the molded body can be brought into a state where it is easier to sinter. Thereby, it is possible to realize a molded body having a preferable particle size and improved sinterability.
なお、水素雰囲気熱処理工程Ｓ７では、より確実な還元作用が得られるよう、濃度１００容量％の水素雰囲気にするのが好ましく、また、水素ガス圧を大気圧よりも高めた雰囲気にすることもできる。さらに、水素雰囲気に水蒸気を導入し、化学平衡を利用して水素の活量を上げても良い。 In addition, in the hydrogen atmosphere heat treatment step S7, it is preferable to use a hydrogen atmosphere with a concentration of 100% by volume in order to obtain a more reliable reduction effect, and it is also possible to create an atmosphere in which the hydrogen gas pressure is higher than atmospheric pressure. . Furthermore, water vapor may be introduced into the hydrogen atmosphere and the activity of hydrogen may be increased using chemical equilibrium.
（Ｓ８：焼結工程）
次に、焼結工程Ｓ８では、水素雰囲気熱処理工程Ｓ７で熱処理した成型体を、真空雰囲気にて加熱焼結する。
(S8: Sintering process)
Next, in a sintering step S8, the molded body heat-treated in the hydrogen atmosphere heat treatment step S7 is heated and sintered in a vacuum atmosphere.
焼結工程Ｓ８は、水素雰囲気熱処理工程Ｓ７後の成型体を別の焼結チャンバーに移して行っても良いが、焼結工程Ｓ８と水素雰囲気熱処理工程Ｓ７とを、同じチャンバー内にて行うのが好ましい。このようにすることで、成型体の酸素濃度増加を抑制し、成型体を高密度に焼結しやすくすることができる。 The sintering step S8 may be performed by moving the molded body after the hydrogen atmosphere heat treatment step S7 to another sintering chamber, but the sintering step S8 and the hydrogen atmosphere heat treatment step S7 may be performed in the same chamber. is preferred. By doing so, it is possible to suppress an increase in the oxygen concentration of the molded body and to easily sinter the molded body to a high density.
また、焼結工程Ｓ８と水素雰囲気熱処理工程Ｓ７とを、同じチャンバー内にて行う場合には、水素雰囲気熱処理工程Ｓ７後のチャンバーを大気解放せずに、直に真空雰囲気にすることが好ましい。すなわち、水素雰囲気熱処理工程Ｓ７後のチャンバー内の水素雰囲気を直に真空雰囲気にすることが好ましい。このようにすることで、成型体の酸素濃度増加が抑制され、成型体を高密度に焼結しやすくすることができ、雰囲気下焼結でも、成型体を高密度に焼結できるようになる。 Further, when the sintering step S8 and the hydrogen atmosphere heat treatment step S7 are performed in the same chamber, it is preferable that the chamber after the hydrogen atmosphere heat treatment step S7 is not exposed to the atmosphere and is immediately placed in a vacuum atmosphere. That is, it is preferable to immediately change the hydrogen atmosphere in the chamber to a vacuum atmosphere after the hydrogen atmosphere heat treatment step S7. By doing this, the increase in oxygen concentration in the molded body is suppressed, making it easier to sinter the molded body to a high density, and even when sintering in an atmosphere, the molded body can be sintered to a high density. .
なお、チャンバー内の水素雰囲気を真空雰囲気にする際には、水素雰囲気をまず不活性雰囲気に置換し、水素などの還元ガスを十分排出した後、チャンバー内を真空排気するのが好ましい。具体的には、チャンバー内の水素雰囲気を、１０Ｐａ程度まで真空排気した後、一旦、窒素、アルゴン等の不活性雰囲気に置換してから、１０Ｐａ以下まで真空排気するのが好ましい。 Note that when the hydrogen atmosphere in the chamber is made into a vacuum atmosphere, it is preferable to first replace the hydrogen atmosphere with an inert atmosphere, sufficiently exhaust reducing gas such as hydrogen, and then evacuate the chamber. Specifically, it is preferable that the hydrogen atmosphere in the chamber is evacuated to about 10 Pa, then replaced with an inert atmosphere such as nitrogen or argon, and then evacuated to 10 Pa or less.
そして、真空雰囲気にしたチャンバー内を、例えば、３００～６００℃／ｈの速度で昇温し、雰囲気を８００～９００℃で１時間保持することで成型体を焼結することができる。チャンバー内の昇温は、例えば、チャンバーにカーボンヒーターを配置し、カーボンヒーターの通電発熱により行うことができる。
加熱により作製された焼結体は、例えば、チャンバー内にて自然冷却しても良いし、２００℃以下でチャンバー内にアルゴンガスを導入して効果的に冷却しても良い。
Then, the molded body can be sintered by raising the temperature in the vacuum atmosphere chamber at a rate of, for example, 300 to 600° C./h and maintaining the atmosphere at 800 to 900° C. for one hour. The temperature in the chamber can be raised, for example, by disposing a carbon heater in the chamber and generating heat by energizing the carbon heater.
The sintered body produced by heating may be naturally cooled in a chamber, or may be effectively cooled by introducing argon gas into the chamber at 200° C. or lower, for example.
（実施例）
次に、本発明の実施例について説明する。本実施例では、秤量工程Ｓ１、混合工程Ｓ２で、組成が、Ｙｂ０．３Ｃ０４Ｓｂ１２のインゴットを作製し、リボン作製工程Ｓ３、熱処理工程Ｓ４、粉砕工程Ｓ５、を経て、メディアン径（ｄ５０）が、約３０μｍの粉砕粉を作製して、以降の工程に供するようにした。
(Example)
Next, examples of the present invention will be described. In this example, an ingot having a composition of Yb 0.3 C0 4 Sb 12 is produced in a weighing step S1 and a mixing step S2, and then subjected to a ribbon production step S3, a heat treatment step S4, and a crushing step S5 to have a median diameter ( A pulverized powder having a d 50 ) of about 30 μm was prepared and used in the subsequent steps.
次に、上記粉砕粉を、プレス成型工程Ｓ６にて、成型圧４００ＭＰａの条件で一軸成形し、寸法がφ１０ｍｍ×３ｍｍｔの成型体を作製した。そして、上記成型体を、水素雰囲気熱処理工程Ｓ７と焼結工程Ｓ８とを連続して処理可能なチャンバー内に配置し、表１に示す条件にて、熱処理と焼結を連続して行った。なお、本条件では、焼結工程Ｓ９で２段昇温を行っており、チャンバー内の温度は、昇温１速度にて昇温した後、保持１温度で保持１時間保持し、その後、昇温２速度で昇温した後、保持１温度（焼結温度）で保持１時間保持するようにした。 Next, the above-mentioned pulverized powder was uniaxially molded at a molding pressure of 400 MPa in a press molding step S6 to produce a molded body having dimensions of φ10 mm×3 mm t . Then, the molded body was placed in a chamber capable of successively performing the hydrogen atmosphere heat treatment step S7 and the sintering step S8, and the heat treatment and sintering were performed continuously under the conditions shown in Table 1. Note that under these conditions, the temperature is raised in two stages in the sintering process S9, and the temperature inside the chamber is raised at the rate of 1 temperature increase, then held at the 1 temperature for 1 hour, and then increased. After increasing the temperature at a rate of 2, the temperature was maintained at a holding temperature of 1 (sintering temperature) for 1 hour.
また、水素雰囲気熱処理工程Ｓ７から焼結工程Ｓ８では、チャンバー内を大気に晒すことなく、チャンバー内雰囲気を変更するようにし、水素雰囲気から直にチャンバー内を真空引きすることで、真空雰囲気を形成した。 In addition, from the hydrogen atmosphere heat treatment step S7 to the sintering step S8, the atmosphere inside the chamber is changed without exposing the inside of the chamber to the atmosphere, and a vacuum atmosphere is created by evacuating the inside of the chamber directly from the hydrogen atmosphere. did.
図２は、本実施例により作製したサンプルの断面写真である。空孔が少なく高密度の焼結体になっていて、加圧焼結でない雰囲気下焼結でも、高密度の焼結体を作製することができた。 FIG. 2 is a cross-sectional photograph of the sample produced according to this example. The sintered body has few pores and has a high density, and it was possible to produce a high-density sintered body even by sintering in an atmosphere rather than by pressure sintering.
なお、上記条件について、水素雰囲気熱処理工程Ｓ７の保持１温度を、６２０℃～６５０℃、焼結工程Ｓ８の保持２温度を８００℃～８７０℃の間で変えてみても、上記条件と同様に、空孔が少なく高密度の焼結体を作製できた。また、焼結工程Ｓ８の保持２温度が、８００℃を下回る条件では、空孔の多い焼結体になったものの、以下に説明する比較例よりも、高密度の焼結体を作製できた。 Regarding the above conditions, even if the holding 1 temperature in the hydrogen atmosphere heat treatment step S7 is changed from 620°C to 650°C and the holding 2 temperature in the sintering step S8 is changed between 800°C to 870°C, the same condition as above is obtained. , we were able to produce a high-density sintered body with few pores. In addition, when the holding temperature in the sintering step S8 was lower than 800°C, the sintered body had many pores, but it was possible to produce a sintered body with higher density than the comparative example described below. .
（比較例）
図３は、本実施例の比較例により作製したサンプルの断面写真である。本比較例は、上記実施例の水素雰囲気熱処理工程Ｓ７を省略したプロセスである。水素雰囲気熱処理工程Ｓ７を省略したために、成型体の粉砕粉表面に存在する酸素の還元除去が不十分であり、ほとんど焼結していない低密度の圧粉体のままであった。
(Comparative example)
FIG. 3 is a photograph of a cross section of a sample prepared according to a comparative example of this example. This comparative example is a process in which the hydrogen atmosphere heat treatment step S7 of the above example is omitted. Since the hydrogen atmosphere heat treatment step S7 was omitted, the reduction and removal of oxygen present on the surface of the pulverized powder of the compact was insufficient, and the compact remained as a low-density green compact that was hardly sintered.
また、上記条件について、焼結工程Ｓ８の保持２温度を変えてみたところ、保持２温度が、８６０℃を下回る条件では、上記条件と同様に、ほとんど焼結していない低密度の圧粉体のままであった。また、保持２温度が、８６０℃を上回る条件では、焼結に代わって一部に溶融が発生し、組成不均一な組織となってしまった。すなわち、水素雰囲気処理工程Ｓ７を省略したプロセスでは、焼結温度である保持２温度を変えても、高密度の焼結体を作製することができなかった。 Regarding the above conditions, when the holding temperature 2 in the sintering process S8 was changed, it was found that when the holding temperature 2 was lower than 860°C, a low-density green compact with almost no sintering was produced, similar to the above conditions. It remained as it was. Furthermore, under conditions where the holding temperature 2 exceeds 860° C., melting occurred in some parts instead of sintering, resulting in a compositionally non-uniform structure. That is, in the process in which the hydrogen atmosphere treatment step S7 was omitted, a high-density sintered body could not be produced even if the holding 2 temperature, which was the sintering temperature, was changed.
以上、本発明の熱電材料の製造方法について、上記実施形態を用いて詳細に説明してきたが、本発明は上記実施形態に限定されるものではない。特許請求の範囲に記載されている技術範囲において内容を変更することが可能である。 Although the method for manufacturing a thermoelectric material of the present invention has been described above in detail using the above embodiments, the present invention is not limited to the above embodiments. It is possible to change the contents within the technical scope described in the claims.
Ｓ１：秤量工程
Ｓ２：混合工程
Ｓ３：リボン作製工程
Ｓ４：熱処理工程
Ｓ５：粉砕工程
Ｓ６：プレス成型工程
Ｓ７：水素雰囲気熱処理工程
Ｓ８：焼結工程
S1: Weighing process S2: Mixing process S3: Ribbon production process S4: Heat treatment process S5: Grinding process S6: Press molding process S7: Hydrogen atmosphere heat treatment process S8: Sintering process
Claims (2)
The thermoelectric device according to claim 1, wherein the heat treatment step and the sintering step are performed in the same chamber, and the inside of the chamber after the heat treatment step is changed from the hydrogen atmosphere to the vacuum atmosphere directly. Method of manufacturing conversion materials.
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| JPH1084138A (en) * | 1996-09-05 | 1998-03-31 | Sumitomo Special Metals Co Ltd | R-fe-b sintered thermoelectric conversion element and manufacture thereof |
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| JP2000252526A (en) | 1998-06-30 | 2000-09-14 | Matsushita Electric Ind Co Ltd | Skutterudite thermoelectric material, thermocouple and manufacture thereof |
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