JP4303924B2

JP4303924B2 - Method for manufacturing thermoelectric semiconductor member

Info

Publication number: JP4303924B2
Application number: JP2002231432A
Authority: JP
Inventors: 智久新井; 貴史六反田; 正己岡村
Original assignee: Toshiba Corp
Current assignee: Toshiba Corp
Priority date: 2002-08-08
Filing date: 2002-08-08
Publication date: 2009-07-29
Anticipated expiration: 2022-08-08
Also published as: JP2004071953A

Description

【０００１】
【発明の属する技術分野】
本発明は、Ｂｉ−Ｔｅ系などの熱電半導体部材の製造方法に関する。
【０００２】
【従来の技術】
ビスマス（Ｂｉ）−テルル（Ｔｅ）系、鉄（Ｆｅ）−シリサイド（Ｓｉ）系、コバルト（Ｃｏ）−アンチモン（Ｓｂ）系などの熱電半導体を使用し、そのペルチェ効果もしくはゼーベック効果を利用した熱電素子は、冷却もしくは加熱装置や発電素子などとして利用されている。例えば、熱電素子は小型・薄型で、かつ液体や気体などの熱媒体（冷媒など）を使用することなく、冷却もしくは加熱を実施することが可能であることから、冷温蔵庫や半導体製造装置の温度制御などを始めとして、各種の分野で冷却装置や加熱装置として使用されており、また最近ではパソコンのＣＰＵの冷却装置としても注目され始めている。さらに、熱電素子は熱電半導体の温度差による発電素子、すなわちゼーベック効果を用いた発電素子としても利用されている。
【０００３】
このような熱電素子は、例えば複数個のＮ型熱電半導体とＰ型熱電半導体とを交互に配置し、これら複数個の熱電半導体を一方の端部側に配置される吸熱側電極と他方の端部側に配置される放熱側電極とで直列に接続した構造を有している。このような熱電素子において、交互に配列されたＮ型熱電半導体とＰ型熱電半導体に直流電流を流すと、Ｎ型熱電半導体からＰ型熱電半導体に向けて電流が流れる電極（吸熱側電極）側ではペルチェ効果により吸熱が起こり、Ｐ型熱電半導体からＮ型熱電半導体に向けて電流が流れる電極（放熱側電極）側では放熱（発熱）が起こるため、吸熱側に被冷却部材や装置などを配置することで冷却を実施することができる。
【０００４】
上述したような熱電素子に使用される熱電半導体の特性は、そのゼーベック係数αと熱伝導率κと比抵抗ρから、［式：α²／κ・ρ］に基づいて評価することができ、この式の値が大きいほど熱電材料としての特性（熱電特性／熱電素子を構成した場合の吸熱量）に優れている。このような特性値に基づく熱電特性は熱電半導体の結晶方位により異なり、例えば結晶構造が六方晶系と見なされるＢｉ−Ｔｅ系熱電半導体では、六方晶のｃ軸方向に比べてｃ面方向（ｃ軸方向に対して直交する方向）の熱電特性が高い。このため、Ｂｉ−Ｔｅ系熱電半導体を熱電素子などに適用する場合には結晶方位を揃えることが重要となる。
【０００５】
このようなことから、熱電素子には例えばＢｉ−Ｔｅ系合金の一方向凝固材（ゾーンメルティング法などによる）が用いられており、結晶方位を揃えた一方向凝固材（Ｂｉ−Ｔｅ系熱電半導体）のｃ面方向に電流を流すように熱電素子を組み立てている。しかしながら、一方向凝固材は結晶配向性に優れているものの、製造コストが高いことに加えて、熱電特性を低下させる熱伝導率が高く、また脆い（機械的強度が低い／へき開破壊しやすい）という難点を有している。
【０００６】
また、特開平11-233836号公報や特開2000-277817公報などに記載されているように、熱間押出で結晶方位を揃えたＢｉ−Ｔｅ系熱電半導体部材を熱電素子に利用することも行われている。上記した各公報には一方向凝固材や単結晶材を熱間押出することが記載されているが、これでは熱電半導体部材の製造コストがさらに上昇してしまう。さらに、特開平11-233836号公報にはＢｉ−Ｔｅ系熱電半導体の溶湯を、空冷もしくは強制空冷のような気体を熱媒体とする方法、油冷または水冷のような液体を熱媒体とする方法、Ｃｕ製やＡｌ製のヒートシンクのような固体を熱媒体とする方法で急速に凝固させ、このような凝固素材を熱間押出して熱電半導体部材を作製することも記載されている。
【０００７】
【発明が解決しようとする課題】
上述したように、熱電半導体の熱電特性はその結晶方位により異なることから、結晶方位が揃った一方向凝固材や熱間押出材を適用することが検討されており、これによって熱電素子の特性を高めることが行われている。しかしながら、熱電半導体の一方向凝固材は製造コストが高いことに加えて、熱伝導率が高いと共に、脆い（機械的強度が低い）というような難点を有している。
【０００８】
また、熱電半導体の熱間押出材に関しては、例えば一方向凝固材や単結晶材、あるいは空冷、油冷、水冷、固体の熱伝導を利用した放冷などにより凝固させた素材を熱間押出することが検討されているものの、一方向凝固材や単結晶材を熱間押出した熱電半導体部材は機械的強度の向上、再結晶組織の微細化による熱伝導率の低減などの効果を有するものの、その製造コストはさらに上昇してしまうという問題がある。一方、上記したような方法で熱電半導体の溶湯を急冷凝固させた素材を熱間押出した熱電半導体部材については、製造コストの低減や均質性の向上による熱電特性の改善などを図ることができるものの、急冷凝固させた素材を単に熱間押出しただけでは熱電特性に影響を及ぼす結晶配向性を必ずしも再現性よく高めることができないというような難点がある。
【０００９】
本発明はこのような課題に対処するためになされたもので、熱電素子などに適用する熱電半導体の製造コストの低減を図った上で、その結晶配向性や機械的特性などを良好にかつ再現性よく高めることを可能にした熱電半導体部材の製造方法を提供することを目的としている。
【００１２】
【課題を解決するための手段】
本発明の熱電半導体部材の製造方法は、Ｂｉ−Ｔｅ系熱電半導体の溶湯を単ロール法または双ロール法により急冷し、柱状晶を体積比で５０％以上含むと共に、平均結晶粒径が５００μｍ以下であるフレーク状の溶湯急冷材を作製する工程と、前記熱電半導体の溶湯急冷材を４００℃以上で前記熱電半導体の融点より３０℃低い温度以下の範囲の温度に加熱した後に、前記熱電半導体の溶湯急冷材と同様な温度に予熱された金型コンテナ内に挿入して熱間押出成形し、前記熱間押出時の押出方向の寸法Ａと前記押出方向に直交する方向の寸法Ｂの比で表される平均アスペクト比（Ａ／Ｂ）が１．５以上の結晶粒を有する熱間押出成形材を作製する工程と、前記熱間押出成形材を所望の部材形状に加工する工程と、前記熱間押出成形材に２５０〜５５０℃の範囲の温度で熱処理を施す工程とを具備することを特徴としている。
【００１５】
本発明の熱電半導体部材の製造方法においては、Ｂｉ−Ｔｅ系熱電半導体の溶湯急冷材を熱間押出成形している。単ロール法または双ロール法（溶湯急冷法）により作製した急冷素材（熱電半導体の溶湯急冷材）は、柱状晶を主体（柱状晶を体積比で５０％以上含む）とし、かつ均質で微細な結晶を有することから、このような溶湯急冷材を熱間押出成形することによって、結晶配向性や機械的強度に優れる熱間押出成形材を安価に得ることができる。特に、本発明では熱間押出成形材を構成する結晶粒の形状を、熱間押出時の押出方向の寸法Ａと押出方向に直交する方向の寸法Ｂの比で表される平均アスペクト比（Ａ／Ｂ）が１．５以上となるように制御しているため、優れた結晶配向性を有する熱電半導体を再現性よく得ることが可能となる。
【００１６】
【発明の実施の形態】
以下、本発明を実施するための形態について説明する。
図１は本発明の一実施形態による熱電半導体部材１を示している。この熱電半導体部材１は熱電半導体の溶湯急冷材を熱間押出してなる熱間押出成形材１ａを具備しており、図中Ｘが熱間押出成形時の押出方向である。このような熱電半導体部材１を熱電素子などに適用する場合には、熱間押出方向Ｘに対して略平行する方向が電流方向となるように、熱間押出成形材１ａを所望の部材形状に加工して使用する。なお図１において、二点鎖線で示す部分は加工後の熱間押出成形材１ａの一例を示すものである。
【００１７】
熱電半導体部材１にはＢｉ−Ｔｅ系熱電半導体が使用される。Ｂｉ−Ｔｅ系熱電半導体としては、ＢｉおよびＳｂから選ばれる少なくとも１種の元素と、ＴｅおよびＳｅから選ばれる少なくとも１種の元素を必須元素として含み、さらに必要に応じてＩ、Ｃｌ、Ｂｒ、Ｈｇ、Ａｕ、Ｃｕなどの添加元素を含む合金が用いられる。Ｂｉ−Ｔｅ系熱電半導体の化学量論組成は、
一般式：（Ｂｉ，Ｓｂ）_２（Ｔｅ，Ｓｅ）_３
で表わされるが、Ｂｉ−Ｔｅ系熱電半導体の合金組成は化学量論組成に限られるものではなく、化学量論組成からずれた合金組成であっても使用可能である。
【００１８】
このようなＢｉ−Ｔｅ系熱電半導体は、結晶構造的には六方晶系と見なすことができ、前述したように六方晶のｃ軸方向に比べてｃ面方向（ｃ軸方向に対して直交する方向）の熱電特性が高い材料である。
【００１９】
図１に示す熱電半導体部材１を構成する熱間押出成形材１ａは、熱電半導体の溶湯急冷材を熱間押出により成形したものである。熱間押出を施す熱電半導体素材には、単ロール法（ストリップキャスト法を含む）または双ロール法を適用した溶湯急冷法により作製した急冷素材（熱電半導体の溶湯急冷材）が用いられる。熱電半導体の溶湯急冷材は微細な柱状晶を主体とすることが好ましい。均質で微細な結晶を有する溶湯急冷材は熱間押出性やそれに基づく結晶の配向性（回転性）に優れている。
【００２０】
単ロール法や双ロール法により作製したフレーク状の急冷素材（溶湯急冷材）は、その厚さ方向に伸びる柱状晶を主体とし、かつフレーク材を押出成形用の金型内に挿入した際に厚さ方向に重なり合うことから、フレーク材中の柱状晶の結晶成長方向と押出方向とをおおよそ一致させることができる。後述するように、熱電半導体部材１は結晶粒を熱間押出方向に伸びた状態とし、この結晶粒形状に基づいて結晶配向性を高めているものであるが、上記したように予め柱状晶の結晶成長方向と押出方向とをおおよそ一致させることによって、熱間押出による結晶粒の配向状態をより一層高めることが可能となる。
【００２１】
熱間押出を施す熱電半導体の溶湯急冷材は、上記したように柱状晶を主体とするものであり、具体的には柱状晶を体積比で５０％以上含んでいる。柱状晶を体積比で５０％以上含む溶湯急冷材を使用することによって、熱間押出による熱電半導体部材１の結晶配向性を再現性よく高めることが可能となる。柱状晶の体積比は７０％以上であることがより好ましい。また、熱電半導体の溶湯急冷材の平均結晶粒径は５００μｍ以下であることが好ましい。このような平均結晶粒径を有する溶湯急冷材を使用することによって、熱間押出性やそれに基づく結晶の配向性（回転性）を高めることができる。溶湯急冷材の平均結晶粒径は１００μｍ以下であることがさらに好ましい。
【００２２】
また、溶湯急冷材の熱間押出は、熱電半導体の溶湯を急冷して作製したフレークに直接施してもよいし、また必要に応じて適当な大きさに粉砕した後に実施してもよい。溶湯急冷材の粉砕には例えば水素粉砕を適用することが好ましく、これによって熱電半導体の特性劣化などを抑制することが可能となる。
【００２３】
上述したような熱電半導体の溶湯急冷材に熱間押出成形を施すと、その際の圧力（径方向および押出方向）により塑性変形し、熱電半導体の結晶粒が押出方向に伸びた状態となる。図２は熱電半導体の熱間押出成形材１ａの微細構造を拡大して示す模式図である。図２において、Ｇは熱電半導体の結晶粒を示しており、また矢印Ｘは熱間押出成形時の押出方向を示している。図２に示すように、熱間押出成形材１ａを構成する結晶粒Ｇは押出方向Ｘに伸びた状態となる。このように、熱電半導体が塑性変形して結晶粒Ｇが押出方向Ｘに伸びる際に、結晶が回転して押出方向Ｘに結晶方位が揃った状態、すなわち結晶方位が押出方向Ｘに配向した状態となる。例えば、Ｂｉ−Ｔｅ系熱電半導体では押出方向Ｘに六方晶と見なされる結晶のc面方向が配向した状態となる。
【００２４】
そして、熱電半導体の結晶粒Ｇの伸び具合やそのばらつきなどは、熱間押出成形材１ａを具備する熱電半導体部材１の特性に影響を及ぼすため、本発明では結晶粒Ｇの押出方向Ｘの寸法をＡ、この押出方向Ｘに直交する方向の寸法をＢとしたとき、これらの比で表されるアスペクト比（Ａ／Ｂ比）を熱電半導体部材１（熱間押出成形材１ａ）全体の平均値として1.5以上とすることが重要である。すなわち、熱間押出成形による結晶粒Ｇの伸びが不十分であったり、また一部の結晶粒Ｇしか伸びていないような状態では、部材全体として結晶方位を良好かつ均一に配向させることができず、よって熱電半導体部材１の熱電特性を十分に高めることができない。
【００２５】
具体的には、熱電半導体の結晶粒Ｇの平均アスペクト比が1.5未満であるということは、部材全体としての結晶粒Ｇの伸びが不足していたり、また部分的に結晶粒Ｇが伸びて部材全体としてはばらつきが大きいことを意味している。これに対して、結晶粒Ｇの平均アスペクト比が1.5以上の場合には、熱電半導体部材１全体として結晶方位を良好かつ均一に配向させた状態が得られるため、結晶方位に依存する熱電特性を十分に高めることが可能となる。結晶粒Ｇの平均アスペクト比は2以上に制御することがより好ましく、さらには5以上に制御することが望ましい。
【００２６】
なお、熱間押出成形材１ａを構成する結晶粒Ｇの平均アスペクト比は、熱間押出成形材１ａの断面観察を行い、観察視野内から20個以上の結晶粒の寸法Ａと寸法Ｂをそれぞれ測定して、個々の結晶粒Ｇのアスペクト比（Ａ／Ｂ比）を求め、これらアスペクト比の平均値を示すものとする。熱間押出成形材１ａの断面観察は3箇所以上について実施し、各観察範囲内の平均アスペクト比をさらに平均して、熱間押出成形材１ａを構成する結晶粒Ｇの平均アスペクト比（平均Ａ／Ｂ比）を求めることが好ましい。
【００２７】
上述したような結晶粒形状を有する熱間押出成形材１ａを得るためには、まず熱間押出を施す熱電半導体素材として溶湯急冷材を使用することが重要であるが、それ以外に熱間押出条件を適切に制御することも重要となる。図３は熱間押出成形工程の一例を示す図である。図３に示すように、熱間押出成形にあたっては、適度な内径ｄ₀を有し、かつこの内径ｄ₀に対して所定の押出比が得られるように設定された孔径ｄ₁を有する押出孔１１を備える金型コンテナ１２と、パンチ１３とを具備する成形装置が用いられる。
【００２８】
金型コンテナ１２やパンチ１３などの成形装置部品には高温での強度が求められるため、セラミックス材料、タングステン、超鋼などの材質からなるものが好ましく、また熱間押出を施す素材（熱電半導体素材）１５と各部品との反応抑制や円滑な押出を実現するために、潤滑材の選択も重要である。潤滑材としては窒化硼素、黒鉛などを使用することが好ましい。潤滑性の確保と微小領域での応力集中を分散させるために、熱電半導体素材１５を薄い銅板でキャニングし、これを加熱した後にキャンごと押出成形してもよい。キャニング材には熱電半導体素材１５と反応しにくく、かつ適度に加工硬化する軟質の金属であれば種々の材料を使用することができる。
【００２９】
上述した成形装置の金型コンテナ１２に熱電半導体素材（溶湯急冷材）１５を挿入して熱間押出成形を行うに際して、熱電半導体は脆性材料であるため、熱電半導体素材１５を予め加熱して十分に軟化させ、かつ前述したような集合組織を得るために適度な粘度で押出すことが重要である。このようなことから、熱電半導体素材１５は予め400℃以上の温度に加熱した後に、同様な温度に予熱された金型コンテナ１２内に挿入することが好ましい。熱電半導体素材１５の加熱温度が400℃未満であると、押出成形時にクラックや割れなどが生じやすいと共に、結晶の回転に基づく結晶配向性が低下する。熱電半導体素材１５の加熱温度は480℃以上であることがより好ましい。加熱温度の上限は熱電半導体の融点より30℃低い温度、より好ましくは50℃低い温度である。
【００３０】
また、熱電半導体素材（溶湯急冷材）１５の熱間押出成形は、それ単独で実施してもよいが、溶湯急冷材１５に炭素や窒化硼素などを潤滑材として添加し、これらの混合物に対して熱間押出を実施してもよい。潤滑材を混合して熱間押出することによって、熱電半導体素材１５の熱間押出性を高めることができる。これによって、例えば熱間押出温度を低下させることが可能となる。潤滑材の添加量は5体積％以下とすることが好ましい。潤滑材の添加量が5体積％を超えると、相対的に熱電半導体量が減少することによって、熱電半導体部材１の熱電特性が低下する。
【００３１】
金型コンテナ１２内に挿入した熱電半導体素材１５をパンチ１３で熱間押出するにあたって、押出圧力や押出速度などは温度条件、素材１５の大きさや組成、また金型コンテナ１２の形状や押出比に応じて適宜に設定する。熱間押出時の塑性変形により熱電半導体の結晶が回転することで、熱間押出成形材１ａ中の結晶の方位が押出方向に配向する。この際、良好な結晶配向性を得るためには押出比が重要な要因となる。例えば、図３に示した熱間押出成形工程の場合には、押出比を2以上とすることが好ましく、さらに好ましくは3以上である。押出比が上記した値未満であると、熱間押出成形材１ａの外周部と中心部との間で結晶粒の形状や配向性にばらつきが生じ、良好な結晶配向性並びにそれに基づく良好な熱電特性を得ることができないおそれがある。
【００３２】
ここで規定する押出比とは、熱間押出成形材１ａの断面が円形の場合には以下に示す(1)式で表される値である。
押出比＝ｄ₀ ²／ｄ₁ ² …(1)
また、押出成形材の断面が円形以外の場合には以下に示す(2)式で表される。
押出比＝Ｓ₀／Ｓ₁ …(2)
（式中、Ｓ₀は素材の押出方向に直角な断面積、Ｓ₁は熱間押出を施した成形材の押出方向に直角な断面積を示す）
【００３３】
上述したような条件下で熱電半導体の溶湯急冷材を熱間押出成形することにより得られる熱間押出成形材１ａは、図２に示したように、結晶粒Ｇが押出方向Ｘに伸びた状態となり、平均アスペクト比（Ａ／Ｂ比）を再現性よく1.5以上とすることができる。そして、このような熱間押出成形材１ａを具備する熱電半導体部材１によれば、結晶粒Ｇの平均アスペクト比などに基づく結晶配向性によって、良好な熱電特性を再現性よく得ることができると共に、機械的強度の向上や熱伝導率の低下などを図ることが可能となる。
【００３４】
熱電半導体の熱間押出成形材１ａは、歪取りなどのための熱処理を施し、さらに所望の部材形状に加工した後に、熱電半導体部材１として実用に供される。この際の熱処理温度は250〜550℃の範囲とすることが好ましく、また熱処理雰囲気は真空中または不活性雰囲気中とすることが好ましい。このような温度で熱間押出成形材１ａを熱処理することによって、熱間押出時に生じた歪が除去されて抵抗率などが低下する。これは熱電特性の向上に寄与するものである。Ｂｉ−Ｔｅ系熱電半導体に対する熱処理温度が250℃未満であると長時間の熱処理が必要となり、また熱処理温度が550℃を超えると異相の生成が原因と考えられる特性劣化が生じる。熱処理温度は400〜550℃の範囲とすることがより好ましい。熱処理後の熱間押出成形材１ａの平均結晶粒径は100μm以下であることが好ましい。平均結晶粒径が100μmを超えると比抵抗が高くなって熱電特性が劣化する。熱処理後の熱間押出成形材１ａの平均結晶粒径は30μm以下であることがより好ましい。
【００３５】
また、熱電半導体部材１の加工は、例えば熱間押出成形材１ａを構成する結晶粒の長手方向（押出方向Ｘ）に対して略平行する方向が電流方向となるように実施することが好ましい。Ｂｉ−Ｔｅ系熱電半導体を適用した熱電半導体部材１においては、前述したように押出方向Ｘに結晶のc面方向が配向した状態となるため、結晶粒の長手方向（押出方向Ｘ）に対して略平行する方向がｃ面方向となる。従って、この方向（押出方向Ｘ＝ｃ面方向）に電流を流すことによって、熱電半導体部材１の熱電特性を向上させることができる。
【００３６】
上述した実施形態の熱電半導体部材１は、熱電半導体のペルチェ効果もしくはゼーベック効果を利用した熱電素子、例えば熱電半導体のペルチェ効果を利用した冷却素子やゼーベック効果を利用した発電素子に好適に用いられるものである。図４は本発明の熱電半導体部材１を利用した熱電素子の一構成例を示す断面図である。同図に示す熱電素子２１は上下に支持部材２２、２３を有しており、これら下部支持部材２２と上部支持部材２３とは対向配置されている。
【００３７】
この実施形態の熱電素子２１は下部支持部材２２側が放熱面、上部支持部材２３側が吸熱面とされている。下部支持部材（放熱側支持部材）２２は熱電素子２１の構造支持体として機能するものであり、例えばアルミナ基板、窒化アルミニウム基板、窒化珪素基板などの絶縁性のセラミックス基板を用いることが好ましい。上部支持部材２３（吸熱側支持部材）には下部支持部材２２と同様に絶縁性基板であるセラミックス基板を用いてもよいし、下部支持部材２２で素子構造全体を支持可能であれば、上部支持部材２３は絶縁性樹脂基板や絶縁性樹脂フィルムなどで構成してもよい。
【００３８】
上述した下部支持部材２２と上部支持部材２３との間には、複数のＮ型熱電半導体２４とＰ型熱電半導体２５とが交互に配列されており、これらは素子全体としてはマトリックス状に配置されて熱電半導体群を構成している。言い換えると、熱電半導体群は下部支持部材２の一主面に沿って交互に配列されている。そして、これらＮ型およびＰ型熱電半導体２４、２５には上述した熱電半導体部材、すなわち熱電半導体の溶湯急冷材を熱間押出してなる熱間押出成形材１ａを具備する熱電半導体部材１が用いられる。
【００３９】
複数のＮ型熱電半導体２４およびＰ型熱電半導体２５は、Ｎ型熱電半導体２４からＰ型熱電半導体２５の方向に、すなわちＮ型熱電半導体２４、Ｐ型熱電半導体２５、Ｎ型熱電半導体２４、Ｐ型熱電半導体２５…の順に直流電流が流れるように、下部支持部材２２側に設けられた放熱側電極２６と上部支持部材２３側に設けられた吸熱側電極２７により電気的に直列に接続されている。これら放熱側電極２６および吸熱側電極２７はそれぞれ複数個で電極群を構成している。
【００４０】
すなわち、下部支持部材２２の表面には放熱側電極２６が複数設けられている。一方、上部支持部材２３側には吸熱側電極２７が複数配置されている。吸熱側電極２７は、隣り合うＮ型熱電半導体２４とＰ型熱電半導体２５とをこの順で電気的に接続する形状を有しており、この熱電半導体２４、２５の接続順序に基づいて、吸熱側電極２７では吸熱が生じる。一方、放熱側電極２６は両端部の電極（リード引出し電極）を除いて、隣り合うＰ型熱電半導体２５とＮ型熱電半導体２４とをこの順で電気的に接続する形状を有しており、この熱電半導体２５、２４の接続順序に基づいて、放熱側電極２６では放熱（発熱）が生じる。
【００４１】
Ｎ型熱電半導体２４およびＰ型熱電半導体２５の下側端部（放熱側端部）は、それぞれ半田層２８を介して放熱側電極２６に接合されている。また、Ｎ型熱電半導体２４およびＰ型熱電半導体２５の上側端部（吸熱側端部／冷却面）は、同様に半田層２９を介して吸熱側電極２７に接合されている。このように、隣り合うＮ型熱電半導体２４とＰ型熱電半導体２５とを、それぞれ放熱側電極２６と吸熱側電極２７とで順に接続することによって、熱電素子２１全体として見た場合に、複数のＮ型熱電半導体２４と複数のＰ型熱電半導体２５とが交互に直列接続された構造を形成している。
【００４２】
上記したπ型構造の熱電素子２１に直流電源３０から熱電半導体２４、２５に直流電流を流すと、ペルチェ効果によって熱電半導体２４、２５の上端部側では吸熱が起こり、下端部側では放熱が起こる。すなわち、隣り合うＮ型熱電半導体２４からＰ型熱電半導体２５に向けて直流電流が流れる吸熱側電極２７では吸熱が生じ、Ｐ型熱電半導体２５からＮ型熱電半導体２４に向けて直流電流が流れる放熱側電極２６では放熱が生じる。従って、熱電素子２１の吸熱側に相当する上部支持部材２３に被冷却体（冷却する部材、部品、装置など）を当接させることによって、被冷却体から熱を奪って冷却が行われる。被冷却体から奪った熱は熱電素子２１の放熱側に相当する下部支持部材２２側から放熱される。
【００４３】
このような構造を有する熱電素子２１においては、Ｎ型およびＰ型熱電半導体２４、２５に上述した熱電半導体の溶湯急冷材を熱間押出してなる熱間押出成形材１ａを具備する熱電半導体部材１が適用されている。従って、熱電半導体部材１の熱電特性や機械的強度などに基づいて、熱電素子２１の特性（冷却特性など）や信頼性を大幅に高めることが可能となる。熱電素子２１は冷温蔵庫や半導体製造装置の温度制御装置、さらにコンピュータのＣＰＵのような超高集積回路素子やレーザ素子などの高発熱半導体部品の冷却装置など、各種分野における冷却装置に好適に用いられるものである。
【００４４】
なお、上述した実施形態では熱電素子２１の支持部材２２、２３を熱電半導体２４、２５の上下両面に配置した構造について説明したが、本発明はこのような構造に限られるものではなく、素子構造を保持する構造用支持部材（図１の下部支持部材２が相当）をＮ型熱電半導体およびＰ型熱電半導体の中間位置に配置した熱電素子１に適用することも可能である。また、上述した実施形態は本発明の熱電半導体部材１を、ペルチェ効果を利用した熱電素子（冷却素子）に適用した場合について説明したが、本発明の熱電半導体部材１はゼーベック効果を利用した熱電素子（発電素子）に適用することも可能であり、その場合においても素子特性や信頼性の向上を図ることができる。
【００４５】
【実施例】
次に、本発明の具体的な実施例について述べる。
【００４６】
実施例１
まず、Ｂｉ_0.4Ｓｂ_1.6Ｔｅ₃組成の合金インゴットを溶解し、この合金溶湯を単ロール法で急冷することによって、平均厚さが約90μmで平均結晶粒径が35μmの合金薄帯を作製した。得られた合金薄帯はほとんどの結晶粒が厚さ方向に伸びる柱状晶（柱状晶の体積比は90％）からなっていた。この合金薄帯を32メッシュ以下となるように粉砕してフレーク状合金片とした。
【００４７】
次に、上記したフレーク状合金片をＡｒガス雰囲気中で500℃まで加熱した後、500℃に予熱した内径30mmの金型コンテナに挿入した。直ちに同じく500℃に予熱したパンチで直径8mmの孔より押出成形することによって、直径8mmの棒状の熱間押出成形材を作製した。この際の押出比は14である。なお、金型コンテナおよびパンチには予め窒化硼素粉末を塗付した。
【００４８】
この後、上記した棒状の熱間押出成形材に、Ａｒガス雰囲気中にて400℃×2時間の条件で熱処理を施し、さらに1.5×1.5×2mmの形状（押出方向が高さ2mmの方向）に加工することによって、目的とするＢｉ_0.4Ｓｂ_1.6Ｔｅ₃合金の熱間押出成形材からなる熱電半導体部材を得た。この熱電半導体部材は高さ2mmの方向（押出方向）を電流方向として使用するものである。また、この熱電半導体部材の結晶組織を観察したところ、組織全体に押出方向に伸びた結晶粒が見られ、結晶粒の平均アスペクト比（Ａ／Ｂ比）は1.8であった。また、熱処理後の平均結晶粒径は13μmであった。このような熱電半導体部材のゼーベック係数と抵抗値を測定したところ、それぞれ221μV/K、1.11×10^-5Ω・mであった。なお、これら特性評価時の電流方向は熱電半導体部材の高さ2mmの方向（押出方向）とした。
【００４９】
実施例２
上記した実施例１において、熱間押出時の押出比を25に変更する以外は実施例１と同様にして、Ｂｉ_0.4Ｓｂ_1.6Ｔｅ₃合金の熱間押出成形材からなる熱電半導体部材を得た。この熱電半導体部材の結晶組織を観察したところ、組織全体に押出方向に伸びた結晶粒が見られ、結晶粒の平均アスペクト比（Ａ／Ｂ比）は4.3であった。また、熱処理後の平均結晶粒径は9μmであった。このような熱電半導体部材のゼーベック係数と抵抗値を実施例１と同様にして測定したところ、それぞれ228μV/K、1.15×10^-5Ω・mであった。
【００５０】
実施例３
上記した実施例２において、熱間押出成形材に対する熱処理条件を300℃×20時間に変更する以外は実施例２と同様にして、Ｂｉ_0.4Ｓｂ_1.6Ｔｅ₃合金の熱間押出成形材からなる熱電半導体部材を得た。この熱電半導体部材の熱処理後の平均結晶粒径は83μmであった。このような熱電半導体部材のゼーベック係数と抵抗値を実施例１と同様にして測定したところ、それぞれ213μV/K、1.21×10^-5Ω・mであった。
【００５１】
比較例１
上記した実施例１において、熱間押出時の押出比を6.3に変更する以外は実施例１と同様にして、Ｂｉ_0.4Ｓｂ_1.6Ｔｅ₃合金の熱間押出成形材からなる熱電半導体部材を得た。この熱電半導体部材の結晶組織を観察したところ、結晶粒が部分的に押出方向に伸びている状態が認められたが、結晶粒の平均アスペクト比（Ａ／Ｂ比）は1.4であった。また、熱処理後の平均結晶粒径は35μmであった。このような熱電半導体部材のゼーベック係数と抵抗値を実施例１と同様にして測定したところ、それぞれ202μV/K、2.01×10^-5Ω・mであった。
【００５２】
比較例２
上記した実施例１において、熱間押出成形材に対する熱処理条件を300℃×100時間に変更する以外は実施例１と同様にして、Ｂｉ_0.4Ｓｂ_1.6Ｔｅ₃合金の熱間押出成形材からなる熱電半導体部材を得た。この熱電半導体部材の熱処理後の平均結晶粒径は115μmであった。このような熱電半導体部材のゼーベック係数と抵抗値を実施例１と同様にして測定したところ、それぞれ201μV/K、1.42×10^-5Ω・mであった。
【００５３】
実施例４
実施例１と同一組成の合金インゴットを溶解し、この合金溶湯を双ロール法で急冷することによって、平均厚さが約250μmで平均結晶粒径が40μmの合金薄帯を作製した。得られた合金薄帯は厚さ方向に伸びる柱状晶を主体とし、柱状晶の体積比は55％であった。この合金薄帯を32メッシュ以下となるように粉砕してフレーク状合金片とした。次いで、このフレーク状合金片を実施例１と同一条件で熱間押出成形することによって、直径8mmの棒状の熱間押出成形材を作製した。
【００５４】
この後、上記した棒状の熱間押出成形材に、Ａｒガス雰囲気中にて300℃×2時間の条件で熱処理を施し、さらに実施例１と同一形状に加工することによって、目的とするＢｉ_0.4Ｓｂ_1.6Ｔｅ₃合金の熱間押出成形材からなる熱電半導体部材を得た。この熱電半導体部材の結晶組織を観察したところ、組織全体に押出方向に伸びた結晶粒が見られ、結晶粒の平均アスペクト比（Ａ／Ｂ比）は1.6であった。また、熱処理後の平均結晶粒径は15μmであった。この熱電半導体部材のゼーベック係数と抵抗値を実施例１と同様にして測定したところ、それぞれ212μV/K、1.09×10^-5Ω・mであった。
【００５５】
比較例３
上記した実施例３において、柱状晶の体積比が45％の合金薄帯（急冷薄帯）を原料として用いる以外は実施例３と同様にして、Ｂｉ_0.4Ｓｂ_1.6Ｔｅ₃合金の熱間押出成形材からなる熱電半導体部材を得た。この熱電半導体部材の結晶組織を観察したところ、押出方向に伸びた結晶粒が見られたが、結晶粒の平均アスペクト比（Ａ／Ｂ比）は1.4であった。また、熱処理後の平均結晶粒径は15μmであった。この熱電半導体部材のゼーベック係数と抵抗値を実施例１と同様にして測定したところ、それぞれ198μV/K、1.09×10^-5Ω・mであった。
【００５６】
実施例５
実施例１と同一組成の合金インゴットを溶解し、この合金溶湯をストリップキャスト法で急冷することによって、平均厚さが約300μmで平均結晶粒径が195μmの合金薄帯を作製した。得られた合金薄帯は厚さ方向に伸びる柱状晶を主体とし、柱状晶の体積比は95％であった。この合金薄帯を32メッシュ以下となるように粉砕してフレーク状合金片とした。次いで、このフレーク状合金片を実施例１と同一条件で熱間押出成形することによって、直径8mmの棒状の熱間押出成形材を作製した。
【００５７】
この後、上記した棒状の熱間押出成形材に、Ａｒガス雰囲気中にて300℃×2時間の条件で熱処理を施し、さらに実施例１と同一形状に加工することによって、目的とするＢｉ_0.4Ｓｂ_1.6Ｔｅ₃合金の熱間押出成形材からなる熱電半導体部材を得た。この熱電半導体部材の結晶組織を観察したところ、組織全体に押出方向に伸びた結晶粒が見られ、結晶粒の平均アスペクト比（Ａ／Ｂ比）は1.8であった。また、熱処理後の平均結晶粒径は14μmであった。この熱電半導体部材のゼーベック係数と抵抗値を実施例１と同様にして測定したところ、それぞれ209μV/K、1.08×10^-5Ω・mであった。
【００５８】
参考例１
実施例１と同一組成の合金インゴットを溶解し、この合金溶湯をガスアトマイズ法で急冷することによって、平均粒子径が１０５μｍで平均結晶粒径が５μｍの合金急冷球粉を作製した。得られた合金急冷球粉はほとんどの結晶粒が中心から伸びる柱状晶からなっていた。柱状晶の体積比は９０％であった。この合金急冷球粉を用いる以外は実施例１と同一条件で熱間押出成形して、直径８ｍｍの棒状の熱間押出成形材を作製した。
【００５９】
この後、上記した棒状の熱間押出成形材に、Ａｒガス雰囲気中にて300℃×2時間の条件で熱処理を施し、さらに実施例１と同一形状に加工することによって、目的とするＢｉ_0.4Ｓｂ_1.6Ｔｅ₃合金の熱間押出成形材からなる熱電半導体部材を得た。この熱電半導体部材の結晶組織を観察したところ、組織全体に押出方向に伸びた結晶粒が見られ、結晶粒の平均アスペクト比（Ａ／Ｂ比）は1.7であった。また、熱処理後の平均結晶粒径は19μmであった。この熱電半導体部材のゼーベック係数と抵抗値を実施例１と同様にして測定したところ、それぞれ210μV/K、1.02×10^-5Ω・mであった。
【００６０】
実施例６
実施例１と同一条件で作製した合金薄帯を真空炉に入れ、炉内を真空排気した後に昇温し、３８０℃で水素を大気圧まで導入して１０分間保持した後、真空排気を行った。この操作を１０回繰り返すことによって、平均粒子径が４２μｍの合金粉末を得た。この合金粉末を用いる以外は実施例１と同一条件で熱間押出成形することによって、直径８ｍｍの棒状の熱間押出成形材を作製した。
【００６１】
この後、上記した棒状の熱間押出成形材に、Ａｒガス雰囲気中にて300℃×2時間の条件で熱処理を施し、さらに実施例１と同一形状に加工することによって、目的とするＢｉ_0.4Ｓｂ_1.6Ｔｅ₃合金の熱間押出成形材からなる熱電半導体部材を得た。この熱電半導体部材の結晶組織を観察したところ、組織全体に押出方向に伸びた結晶粒が見られ、結晶粒の平均アスペクト比（Ａ／Ｂ比）は1.8であった。また、熱処理後の平均結晶粒径は13μmであった。この熱電半導体部材のゼーベック係数と抵抗値を実施例１と同様にして測定したところ、それぞれ224μV/K、1.10×10^-5Ω・mであった。
【００６２】
実施例７
実施例１と同一条件で作製したフレーク状合金片と炭素粉末とを、体積比で９４：６の割合で混合した。この混合物を用いる以外は実施例１と同一条件で熱間押出成形することによって、直径８ｍｍの棒状の熱間押出成形材を作製した。この後、上記した棒状の熱間押出成形材に、Ａｒガス雰囲気中にて３００℃×２時間の条件で熱処理を施し、さらに実施例１と同一形状に加工することによって、目的とするＢｉ_０．４Ｓｂ_１．６Ｔｅ_３合金の熱間押出成形材からなる熱電半導体部材を得た。
【００６３】
このようにして得た熱電半導体部材の結晶組織を観察したところ、組織全体に押出方向に伸びた結晶粒が見られ、結晶粒の平均アスペクト比（Ａ／Ｂ比）は1.9であった。また、熱処理後の平均結晶粒径は15μmであった。この熱電半導体部材のゼーベック係数と抵抗値を実施例１と同様にして測定したところ、それぞれ220μV/K、1.05×10^-5Ω・mであった。なお、炭素粉末に代えて窒化硼素粉末を混合した場合の熱電半導体部材のゼーベック係数と抵抗値は、それぞれ217μV/K、1.12×10^-5Ω・mであった。
【００６４】
上述したように、潤滑材として炭素粉末や窒化硼素粉末を混合することによって、押出成形性が向上することを確認した。具体的には、熱間押出温度を50℃低くした場合においても良好に押出成形を実施することができ、熱電半導体部材のゼーベック係数や抵抗値もほとんど変わらないことを確認した。なお、潤滑材を添加しない場合に熱間押出温度を50℃低くすると、押出成形時に割れが生じやすく、また特性値も低下した。
【００６５】
比較例４
実施例１と同一組成の合金インゴットを鋳造法で作製し、この合金インゴットを平均粒子径が106μm以下となるように粉砕した。この合金粉末をＡｒガス雰囲気中で500℃まで加熱した後、ホットプレス用金型内に挿入して2ton/cm²の圧力でホットプレス成形した。この熱電半導体部材の結晶組織は等方的であり、結晶粒の平均アスペクト比（Ａ／Ｂ比）は1.1であった。このような熱電半導体部材のゼーベック係数と抵抗値を測定したところ、それぞれ172μV/K、1.07×10^-5Ω・mであった。さらに、得られた熱電半導体部材は実施例の各部材に比べて機械的強度が低く、また熱伝導率も劣るものであった。
【００６６】
実施例８
上記した各実施例の熱電半導体部材と同様にして、Ｂｉ２８ａｔ．％−Ｔｅ５７ａｔ．％−Ｓｂ１２ａｔ．％−Ｓｅ３ａｔ．％組成のＮ型熱電半導体部材と、Ｂｉ１０ａｔ．％−Ｔｅ５７ａｔ．％−Ｓｂ１０ａｔ．％−Ｓｅ３ａｔ．％組成のＰ型熱電半導体部材を作製し、図４に示した熱電素子をそれぞれ作製した。なお、Ｎ型およびＰ型熱電半導体部材は、それぞれ熱間押出成形材の押出方向が部材長手方向（電流方向）となるように加工し、この部材長手方向を素子の厚さ方向（電流方向）に合わせて吸熱側電極と放熱側電極との間に配置した。このようにして得た各熱電素子に通電して熱電特性と信頼性を評価したところ、それぞれ良好な結果を示すことが確認された。
【００６７】
【発明の効果】
以上説明したように、本発明の熱電半導体部材によれば、熱電素子などに適用する熱電半導体の製造コストの低減を図った上で、その結晶配向性や機械的特性などを良好にかつ再現性よく高めることが可能となる。従って、そのような熱電半導体部材を適用した熱電素子によれば、熱電特性と信頼性の向上を図ることができる。すなわち、熱電特性と信頼性に優れた熱電素子を再現性よく提供することが可能となる。
【図面の簡単な説明】
【図１】本発明の一実施形態による熱電半導体部材の外観を示す斜視図である。
【図２】図１に示す熱電半導体部材（熱間押出成形材）の微細構造を拡大して示す模式図である。
【図３】図１に示す熱電半導体部材の熱間押出状態および熱間押出条件を説明するための図である。
【図４】本発明の一実施形態による熱電素子の概略構造を示す断面図である。
【符号の説明】
１……熱電半導体部材、１ａ……熱間押出成形材、２１……熱電素子、２２……下部支持部材、２３……上部支持部材、２４……Ｎ型熱電半導体、２５……Ｐ型熱電半導体、２６……放電側電極、２７……吸熱側電極、３０……直流電源[0001]
BACKGROUND OF THE INVENTION
  The present invention relates to a thermoelectric semiconductor member such as Bi-Te.ofManufacturing methodTo the lawRelated.
[0002]
[Prior art]
Thermoelectrics using thermoelectric semiconductors such as bismuth (Bi) -tellurium (Te), iron (Fe) -silicide (Si), cobalt (Co) -antimony (Sb), etc., and utilizing the Peltier effect or Seebeck effect The element is used as a cooling or heating device or a power generation element. For example, thermoelectric elements are small and thin, and can be cooled or heated without using a heat medium (such as a refrigerant) such as liquid or gas. It is used as a cooling device and a heating device in various fields including temperature control, and recently it has begun to attract attention as a cooling device for a CPU of a personal computer. Furthermore, thermoelectric elements are also used as power generation elements based on temperature differences of thermoelectric semiconductors, that is, power generation elements using the Seebeck effect.
[0003]
Such a thermoelectric element includes, for example, a plurality of N-type thermoelectric semiconductors and P-type thermoelectric semiconductors alternately arranged, and the plurality of thermoelectric semiconductors disposed on one end side and the other end. It has a structure in which it is connected in series with a heat-dissipating electrode arranged on the part side. In such a thermoelectric element, when a direct current is passed through alternately arranged N-type thermoelectric semiconductors and P-type thermoelectric semiconductors, an electrode (heat absorption side electrode) side through which current flows from the N-type thermoelectric semiconductor toward the P-type thermoelectric semiconductor In the Peltier effect, heat absorption occurs, and heat dissipation (heat generation) occurs on the electrode (heat dissipation side electrode) side where current flows from the P-type thermoelectric semiconductor to the N-type thermoelectric semiconductor. By doing so, cooling can be carried out.
[0004]
The characteristics of the thermoelectric semiconductors used in the thermoelectric elements as described above are expressed by the following equation: [Expression: α²/ Κ · ρ], and the larger the value of this equation, the better the characteristics as a thermoelectric material (thermoelectric characteristics / heat absorption when a thermoelectric element is configured). The thermoelectric characteristics based on such characteristic values vary depending on the crystal orientation of the thermoelectric semiconductor. For example, in a Bi-Te thermoelectric semiconductor in which the crystal structure is considered to be hexagonal, the c-plane direction (c The thermoelectric properties in the direction perpendicular to the axial direction are high. For this reason, it is important to align the crystal orientation when the Bi-Te based thermoelectric semiconductor is applied to a thermoelectric element or the like.
[0005]
For this reason, for example, a unidirectional solidified material (by a zone melting method or the like) of a Bi-Te alloy is used for the thermoelectric element, and a unidirectional solidified material (Bi-Te thermoelectric material) with a uniform crystal orientation is used. The thermoelectric element is assembled so that a current flows in the c-plane direction of the semiconductor. However, although the unidirectionally solidified material is excellent in crystal orientation, in addition to high manufacturing cost, it has high thermal conductivity that reduces thermoelectric properties and is brittle (low mechanical strength / easy to cleave) Has the disadvantages.
[0006]
In addition, as described in JP-A-11-233836, JP-A-2000-277817, and the like, a Bi-Te thermoelectric semiconductor member having a crystal orientation aligned by hot extrusion may be used for a thermoelectric element. It has been broken. Each of the above publications describes hot extruding a unidirectionally solidified material or single crystal material, but this further increases the manufacturing cost of the thermoelectric semiconductor member. Furthermore, Japanese Patent Application Laid-Open No. 11-233836 discloses a method using a molten Bi-Te-based thermoelectric semiconductor as a heat medium such as air cooling or forced air cooling, and a method using a liquid such as oil cooling or water cooling as a heat medium. It also describes that a thermoelectric semiconductor member is produced by rapidly solidifying by a method using a solid such as a heat sink made of Cu or Al as a heat medium, and extruding such a solidified material hot.
[0007]
[Problems to be solved by the invention]
As described above, since the thermoelectric characteristics of thermoelectric semiconductors differ depending on the crystal orientation, it has been studied to apply a unidirectional solidified material or a hot extruded material having a uniform crystal orientation, thereby improving the characteristics of the thermoelectric element. It has been done to raise. However, the unidirectionally solidified material of the thermoelectric semiconductor has the disadvantages of high manufacturing cost, high thermal conductivity, and brittleness (low mechanical strength).
[0008]
As for hot extruded materials of thermoelectric semiconductors, for example, a unidirectionally solidified material, a single crystal material, or a material solidified by air cooling, oil cooling, water cooling, or cooling using solid heat conduction is hot extruded. However, although thermoelectric semiconductor members obtained by hot extrusion of unidirectionally solidified materials and single crystal materials have effects such as improvement of mechanical strength and reduction of thermal conductivity by recrystallization structure refinement, There is a problem that the manufacturing cost further increases. On the other hand, for thermoelectric semiconductor members obtained by hot-extrusion of a material obtained by rapidly solidifying a molten thermoelectric semiconductor by the method described above, it is possible to improve the thermoelectric characteristics by reducing the manufacturing cost and improving the homogeneity. However, there is a problem that crystal orientation that affects thermoelectric properties cannot always be improved with high reproducibility simply by hot extrusion of a rapidly solidified material.
[0009]
  The present invention has been made in order to cope with such a problem. The production cost of a thermoelectric semiconductor applied to a thermoelectric element or the like is reduced, and the crystal orientation and mechanical characteristics thereof are reproduced well. Thermoelectric semiconductor member that can be improved with good performanceofManufacturing methodThe lawIt is intended to provide.
[0012]
[Means for Solving the Problems]
  The manufacturing method of the thermoelectric semiconductor member of the present invention is as follows:Bi-Te systemSingle roll method of molten thermoelectric semiconductorOrTwin rollTo the lawCool more rapidly and contain 50% or more of columnar crystals by volumeIn addition, the flaky shape with an average crystal grain size of 500 μm or lessA step of producing a molten metal quenching material, and a molten metal quenching material of the thermoelectric semiconductor at 400 ° C. or higher.In a range below 30 ° C. below the melting point of the thermoelectric semiconductorAfter heating to the temperature ofSimilar to the thermoelectric semiconductor melt quenching materialInserted into a mold container preheated to a temperature and subjected to hot extrusion molding, an average aspect ratio represented by the ratio of the dimension A in the extrusion direction during the hot extrusion and the dimension B in the direction perpendicular to the extrusion direction (A / B) producing a hot extruded material having crystal grains of 1.5 or more, and processing the hot extruded material into a desired member shape;Applying a heat treatment to the hot extruded material at a temperature in the range of 250 to 550 ° C.It is characterized by comprising.
[0015]
  In the manufacturing method of the thermoelectric semiconductor member of the present invention,Bi-Te systemThermoelectric semiconductor melt quenching material is hot-extruded.singleRoll methodOrTwin rollLaw (Melt quenching method)Since the quenching material (melting quenching material for thermoelectric semiconductors) produced by the above method is mainly composed of columnar crystals (including columnar crystals of 50% or more by volume) and has homogeneous and fine crystals, such a quenching material for molten metal By hot extrusion molding, a hot extrusion molding material having excellent crystal orientation and mechanical strength can be obtained at a low cost. In particular, in the present invention, the shape of the crystal grains constituting the hot-extruded material is expressed by the average aspect ratio (A) expressed by the ratio of the dimension A in the extrusion direction during hot extrusion and the dimension B in the direction orthogonal to the extrusion direction. Since / B) is controlled to be 1.5 or more, a thermoelectric semiconductor having excellent crystal orientation can be obtained with good reproducibility.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, modes for carrying out the present invention will be described.
FIG. 1 shows a thermoelectric semiconductor member 1 according to an embodiment of the present invention. The thermoelectric semiconductor member 1 includes a hot extrusion molding material 1a obtained by hot extruding a molten quenching material of a thermoelectric semiconductor, and X in the figure is an extrusion direction at the time of hot extrusion molding. When such a thermoelectric semiconductor member 1 is applied to a thermoelectric element or the like, the hot extrusion molding material 1a is formed into a desired member shape so that the direction substantially parallel to the hot extrusion direction X is the current direction. Process and use. In addition, in FIG. 1, the part shown with a dashed-two dotted line shows an example of the hot extrusion molding material 1a after a process.
[0017]
  For thermoelectric semiconductor member 1IsBi-Te based thermoelectric semiconductorused. As the Bi—Te based thermoelectric semiconductor, at least one element selected from Bi and Sb and at least one element selected from Te and Se are included as essential elements, and I, Cl, Br, An alloy containing an additive element such as Hg, Au, or Cu is used. The stoichiometric composition of Bi-Te thermoelectric semiconductor is
  General formula: (Bi, Sb)₂(Te, Se)₃
  However, the alloy composition of the Bi-Te-based thermoelectric semiconductor is not limited to the stoichiometric composition, and an alloy composition deviating from the stoichiometric composition can be used.
[0018]
  Such Bi—Te thermoelectric semiconductors can be regarded as hexagonal in terms of crystal structure, and as described above, the c-plane direction (perpendicular to the c-axis direction) compared to the hexagonal c-axis direction. Direction) material with high thermoelectric properties.
[0019]
  A hot extrusion molding material 1a constituting the thermoelectric semiconductor member 1 shown in FIG. 1 is formed by hot extrusion of a molten metal quenching material of a thermoelectric semiconductor. For thermoelectric semiconductor materials subjected to hot extrusion, single roll method (including strip cast method)OrTwin roll methodAppliedA quenching material (thermoelectric semiconductor melt quenching material) produced by a melt quenching method is used. The molten metal quenching material of the thermoelectric semiconductor is preferably mainly composed of fine columnar crystals. The molten metal quenching material having homogeneous and fine crystals is excellent in hot extrudability and crystal orientation (rotation) based thereon.
[0020]
  singleFlake-like quenching material (molten quenching material) produced by the roll method or twin-roll method is mainly composed of columnar crystals extending in the thickness direction, and is thick when the flake material is inserted into an extrusion mold. Since they overlap in the vertical direction, the crystal growth direction of the columnar crystals in the flake material and the extrusion direction can be approximately matched. As will be described later, the thermoelectric semiconductor member 1 has crystal grains extending in the hot extrusion direction and has improved crystal orientation based on the crystal grain shape. By making the crystal growth direction and the extrusion direction approximately coincide with each other, it is possible to further enhance the orientation state of the crystal grains by hot extrusion.
[0021]
  As described above, the thermoelectric semiconductor melt quenching material subjected to hot extrusion is mainly composed of columnar crystals.Is a thingSpecifically, it contains columnar crystals in a volume ratio of 50% or more.I am. By using a molten metal quenching material containing columnar crystals in a volume ratio of 50% or more, the crystal orientation of the thermoelectric semiconductor member 1 by hot extrusion can be improved with good reproducibility. The volume ratio of the columnar crystals is more preferably 70% or more. The average crystal grain size of the thermoelectric semiconductor melt quenching material is preferably 500 μm or less. By using a molten metal quenching material having such an average crystal grain size, hot extrudability and crystal orientation (rotation) based thereon can be enhanced. The average crystal grain size of the molten metal quenching material is more preferably 100 μm or less.
[0022]
  Also, hot extrusion of molten metal quenching material is made by quenching molten metal of thermoelectric semiconductor.TheflakeInIt may be applied directly, or may be carried out after pulverizing to an appropriate size as required. For example, hydrogen pulverization is preferably applied to pulverize the molten metal quenching material, which makes it possible to suppress deterioration of thermoelectric semiconductor characteristics..
[0023]
When hot extrusion molding is performed on the molten metal quenching material of the thermoelectric semiconductor as described above, it is plastically deformed by the pressure (radial direction and extrusion direction) at that time, and the crystal grains of the thermoelectric semiconductor extend in the extrusion direction. FIG. 2 is an enlarged schematic view showing the microstructure of the thermoelectric semiconductor hot extrusion molding material 1a. In FIG. 2, G indicates the crystal grains of the thermoelectric semiconductor, and the arrow X indicates the extrusion direction during hot extrusion molding. As shown in FIG. 2, the crystal grains G constituting the hot extrusion molding material 1 a are in a state of extending in the extrusion direction X. Thus, when the thermoelectric semiconductor is plastically deformed and the crystal grains G extend in the extrusion direction X, the crystal rotates and the crystal orientation is aligned in the extrusion direction X, that is, the crystal orientation is oriented in the extrusion direction X. It becomes. For example, in a Bi-Te-based thermoelectric semiconductor, the c-plane direction of a crystal that is regarded as a hexagonal crystal is oriented in the extrusion direction X.
[0024]
In addition, in the present invention, the size of the crystal grains G in the extrusion direction X is determined because the degree of elongation of the crystal grains G of the thermoelectric semiconductor and the variation thereof affect the characteristics of the thermoelectric semiconductor member 1 including the hot extrusion molding material 1a. Is the average of the thermoelectric semiconductor member 1 (hot extrusion molding material 1a) as the aspect ratio (A / B ratio) expressed by these ratios, where B is the dimension perpendicular to the extrusion direction X. It is important that the value is 1.5 or more. That is, in the state where the elongation of the crystal grains G by hot extrusion molding is insufficient or only a part of the crystal grains G is elongated, the crystal orientation can be oriented well and uniformly as a whole member. Therefore, the thermoelectric characteristics of the thermoelectric semiconductor member 1 cannot be sufficiently improved.
[0025]
Specifically, the fact that the average aspect ratio of the crystal grains G of the thermoelectric semiconductor is less than 1.5 means that the elongation of the crystal grains G as a whole member is insufficient or the crystal grains G are partially elongated. It means that the variation is large as a whole. On the other hand, when the average aspect ratio of the crystal grains G is 1.5 or more, since the thermoelectric semiconductor member 1 as a whole has a good and uniform crystal orientation, thermoelectric characteristics depending on the crystal orientation are obtained. It can be sufficiently increased. The average aspect ratio of the crystal grains G is more preferably controlled to 2 or more, and more preferably 5 or more.
[0026]
The average aspect ratio of the crystal grains G constituting the hot extrusion molding material 1a is obtained by observing the cross section of the hot extrusion molding material 1a and measuring the dimension A and the dimension B of 20 or more crystal grains from the observation field. The aspect ratio (A / B ratio) of each crystal grain G is obtained by measurement, and the average value of these aspect ratios is shown. The cross-section observation of the hot extrusion molding material 1a is carried out at three or more locations, and the average aspect ratio within each observation range is further averaged to obtain the average aspect ratio of the crystal grains G constituting the hot extrusion molding material 1a (average A / B ratio) is preferably obtained.
[0027]
In order to obtain the hot extrusion molding material 1a having the crystal grain shape as described above, it is important to first use a molten metal quenching material as a thermoelectric semiconductor material to be subjected to hot extrusion. It is also important to control the conditions appropriately. FIG. 3 is a diagram illustrating an example of a hot extrusion molding process. As shown in FIG. 3, in hot extrusion molding, an appropriate inner diameter d₀And this inner diameter d₀Pore diameter d set so as to obtain a predetermined extrusion ratio with respect to₁A molding apparatus including a mold container 12 having an extrusion hole 11 having a punch 13 and a punch 13 is used.
[0028]
Since molding device parts such as the mold container 12 and the punch 13 are required to have high strength at high temperatures, materials made of ceramic materials, tungsten, super steel, etc. are preferable, and materials for hot extrusion (thermoelectric semiconductor materials) ) Selection of a lubricant is also important in order to suppress reaction between 15 and each part and to realize smooth extrusion. As the lubricant, boron nitride, graphite or the like is preferably used. In order to ensure lubricity and disperse the stress concentration in a minute region, the thermoelectric semiconductor material 15 may be canned with a thin copper plate, and heated and then extruded together with the can. Various materials can be used for the canning material as long as it is a soft metal that does not easily react with the thermoelectric semiconductor material 15 and is appropriately work-hardened.
[0029]
When the thermoelectric semiconductor material (molten quench material) 15 is inserted into the mold container 12 of the molding apparatus described above and hot extrusion molding is performed, since the thermoelectric semiconductor is a brittle material, the thermoelectric semiconductor material 15 is sufficiently heated in advance. It is important to extrude at an appropriate viscosity in order to soften and to obtain a texture as described above. For this reason, it is preferable that the thermoelectric semiconductor material 15 is inserted into the mold container 12 preheated to a similar temperature after being heated to a temperature of 400 ° C. or higher in advance. When the heating temperature of the thermoelectric semiconductor material 15 is less than 400 ° C., cracks and cracks are likely to occur during extrusion molding, and crystal orientation based on crystal rotation is reduced. The heating temperature of the thermoelectric semiconductor material 15 is more preferably 480 ° C. or higher. The upper limit of the heating temperature is a temperature 30 ° C. lower than the melting point of the thermoelectric semiconductor, more preferably a temperature lower by 50 ° C.
[0030]
Further, the hot extrusion molding of the thermoelectric semiconductor material (molten quench material) 15 may be performed alone, but carbon or boron nitride or the like is added to the melt quench material 15 as a lubricant, Hot extrusion may be performed. The hot extrudability of the thermoelectric semiconductor material 15 can be improved by mixing the lubricant and extruding it hot. Thereby, for example, the hot extrusion temperature can be lowered. The amount of lubricant added is preferably 5% by volume or less. When the addition amount of the lubricant exceeds 5% by volume, the thermoelectric semiconductor amount of the thermoelectric semiconductor member 1 is deteriorated due to a relative decrease in the amount of the thermoelectric semiconductor.
[0031]
When the thermoelectric semiconductor material 15 inserted into the mold container 12 is hot-extruded by the punch 13, the extrusion pressure and the extrusion speed depend on the temperature conditions, the size and composition of the material 15, and the shape and extrusion ratio of the mold container 12. Set accordingly. The crystal of the thermoelectric semiconductor is rotated by plastic deformation during hot extrusion, so that the orientation of the crystal in the hot extruded material 1a is oriented in the extrusion direction. At this time, the extrusion ratio is an important factor for obtaining good crystal orientation. For example, in the case of the hot extrusion molding step shown in FIG. 3, the extrusion ratio is preferably 2 or more, more preferably 3 or more. When the extrusion ratio is less than the above-described value, the shape and orientation of the crystal grains vary between the outer peripheral portion and the central portion of the hot extrusion molding material 1a, and good crystal orientation and good thermoelectric power based on the crystal orientation are obtained. There is a possibility that characteristics cannot be obtained.
[0032]
The extrusion ratio specified here is a value represented by the following formula (1) when the cross section of the hot extrusion molded material 1a is circular.
Extrusion ratio = d₀ ²/ D₁ ²  … (1)
In addition, when the cross section of the extruded material is other than circular, it is expressed by the following equation (2).
Extrusion ratio = S₀/ S₁    … (2)
(Where S₀Is the cross-sectional area perpendicular to the extrusion direction of the material, S₁Indicates a cross-sectional area perpendicular to the extrusion direction of a hot-extrusion molding material)
[0033]
As shown in FIG. 2, the hot extrusion molding material 1 a obtained by hot extrusion molding the molten metal quenching material of the thermoelectric semiconductor under the conditions as described above is in a state where the crystal grains G extend in the extrusion direction X. Thus, the average aspect ratio (A / B ratio) can be 1.5 or more with good reproducibility. And according to the thermoelectric semiconductor member 1 which comprises such a hot extrusion molding material 1a, while being able to obtain a favorable thermoelectric characteristic with sufficient reproducibility by the crystal orientation based on the average aspect ratio of the crystal grain G, etc. It is possible to improve the mechanical strength and reduce the thermal conductivity.
[0034]
The thermoelectric semiconductor hot-extrusion molding material 1a is subjected to heat treatment for removing strain and processed into a desired member shape, and is then put to practical use as the thermoelectric semiconductor member 1. In this case, the heat treatment temperature is preferably in the range of 250 to 550 ° C., and the heat treatment atmosphere is preferably in a vacuum or in an inert atmosphere. By heat-treating the hot extrusion molding material 1a at such a temperature, the strain generated during the hot extrusion is removed and the resistivity and the like are lowered. This contributes to improvement of thermoelectric characteristics. When the heat treatment temperature for the Bi-Te-based thermoelectric semiconductor is less than 250 ° C., a long-time heat treatment is required, and when the heat treatment temperature exceeds 550 ° C., characteristic deterioration that is considered to be caused by generation of a different phase occurs. The heat treatment temperature is more preferably in the range of 400 to 550 ° C. The average crystal grain size of the hot extruded material 1a after the heat treatment is preferably 100 μm or less. When the average crystal grain size exceeds 100 μm, the specific resistance increases and the thermoelectric characteristics deteriorate. The average crystal grain size of the hot extruded material 1a after the heat treatment is more preferably 30 μm or less.
[0035]
Moreover, it is preferable to implement the processing of the thermoelectric semiconductor member 1 so that the direction substantially parallel to the longitudinal direction (extrusion direction X) of the crystal grains constituting the hot extrusion molding material 1a is the current direction, for example. In the thermoelectric semiconductor member 1 to which the Bi—Te based thermoelectric semiconductor is applied, since the c-plane direction of the crystal is oriented in the extrusion direction X as described above, the longitudinal direction of the crystal grains (extrusion direction X). The substantially parallel direction is the c-plane direction. Therefore, the thermoelectric characteristics of the thermoelectric semiconductor member 1 can be improved by passing a current in this direction (extrusion direction X = c-plane direction).
[0036]
The thermoelectric semiconductor member 1 of the above-described embodiment is suitably used for a thermoelectric element using the Peltier effect or Seebeck effect of a thermoelectric semiconductor, for example, a cooling element using the Peltier effect of a thermoelectric semiconductor or a power generation element using the Seebeck effect. It is. FIG. 4 is a cross-sectional view showing a structural example of a thermoelectric element using the thermoelectric semiconductor member 1 of the present invention. The thermoelectric element 21 shown in the figure has support members 22 and 23 at the top and bottom, and the lower support member 22 and the upper support member 23 are arranged to face each other.
[0037]
In the thermoelectric element 21 of this embodiment, the lower support member 22 side is a heat dissipation surface, and the upper support member 23 side is a heat absorption surface. The lower support member (heat radiation side support member) 22 functions as a structural support for the thermoelectric element 21. For example, an insulating ceramic substrate such as an alumina substrate, an aluminum nitride substrate, or a silicon nitride substrate is preferably used. As the upper support member 23 (heat absorption side support member), a ceramic substrate which is an insulating substrate may be used similarly to the lower support member 22, and if the entire element structure can be supported by the lower support member 22, the upper support is supported. The member 23 may be composed of an insulating resin substrate or an insulating resin film.
[0038]
A plurality of N-type thermoelectric semiconductors 24 and P-type thermoelectric semiconductors 25 are alternately arranged between the lower support member 22 and the upper support member 23 described above, and these are arranged in a matrix as the entire element. This constitutes a thermoelectric semiconductor group. In other words, the thermoelectric semiconductor groups are alternately arranged along one main surface of the lower support member 2. The N-type and P-type thermoelectric semiconductors 24 and 25 use the thermoelectric semiconductor member 1 including the above-described thermoelectric semiconductor member, that is, the hot extrusion molding material 1a obtained by hot extrusion of the molten metal quenching material of the thermoelectric semiconductor. .
[0039]
The plurality of N-type thermoelectric semiconductors 24 and P-type thermoelectric semiconductors 25 are arranged in the direction from the N-type thermoelectric semiconductor 24 to the P-type thermoelectric semiconductor 25, that is, the N-type thermoelectric semiconductor 24, the P-type thermoelectric semiconductor 25, the N-type thermoelectric semiconductor 24, P Are connected in series by a heat radiation side electrode 26 provided on the lower support member 22 side and a heat absorption side electrode 27 provided on the upper support member side side so that a direct current flows in the order of the type thermoelectric semiconductors 25. Yes. A plurality of these heat radiation side electrodes 26 and heat absorption side electrodes 27 constitute an electrode group.
[0040]
That is, a plurality of heat radiation side electrodes 26 are provided on the surface of the lower support member 22. On the other hand, a plurality of heat absorption side electrodes 27 are arranged on the upper support member 23 side. The heat absorption side electrode 27 has a shape in which adjacent N-type thermoelectric semiconductors 24 and P-type thermoelectric semiconductors 25 are electrically connected in this order, and based on the connection order of the thermoelectric semiconductors 24, 25, heat absorption The side electrode 27 absorbs heat. On the other hand, the heat-dissipation side electrode 26 has a shape that electrically connects the adjacent P-type thermoelectric semiconductor 25 and N-type thermoelectric semiconductor 24 in this order except for the electrodes (lead lead electrodes) at both ends. Based on the connection order of the thermoelectric semiconductors 25, 24, heat dissipation (heat generation) occurs in the heat dissipation side electrode 26.
[0041]
Lower end portions (radiation side end portions) of the N-type thermoelectric semiconductor 24 and the P-type thermoelectric semiconductor 25 are respectively joined to the heat radiation side electrode 26 via the solder layer 28. Similarly, the upper end portions (heat absorption side end portions / cooling surfaces) of the N-type thermoelectric semiconductor 24 and the P-type thermoelectric semiconductor 25 are joined to the heat absorption side electrode 27 via the solder layer 29. In this way, when the adjacent N-type thermoelectric semiconductor 24 and P-type thermoelectric semiconductor 25 are connected in order by the heat radiation side electrode 26 and the heat absorption side electrode 27, respectively, A structure in which N-type thermoelectric semiconductors 24 and a plurality of P-type thermoelectric semiconductors 25 are alternately connected in series is formed.
[0042]
When a direct current is passed from the DC power supply 30 to the thermoelectric semiconductors 24 and 25 through the π-type thermoelectric element 21, heat absorption occurs at the upper end side of the thermoelectric semiconductors 24 and 25 due to the Peltier effect, and heat dissipation occurs at the lower end side. . That is, heat absorption occurs in the heat absorption side electrode 27 in which a direct current flows from the adjacent N-type thermoelectric semiconductor 24 toward the P-type thermoelectric semiconductor 25, and heat dissipation in which a direct current flows from the P-type thermoelectric semiconductor 25 toward the N-type thermoelectric semiconductor 24. The side electrode 26 generates heat. Accordingly, by bringing a body to be cooled (a member to be cooled, a component, a device, or the like) into contact with the upper support member 23 corresponding to the heat absorption side of the thermoelectric element 21, cooling is performed by removing heat from the body to be cooled. The heat taken from the object to be cooled is radiated from the lower support member 22 side corresponding to the heat radiating side of the thermoelectric element 21.
[0043]
In the thermoelectric element 21 having such a structure, a thermoelectric semiconductor member 1 including a hot extrusion molding material 1a obtained by hot extruding the above-described molten quenching material of a thermoelectric semiconductor to N-type and P-type thermoelectric semiconductors 24 and 25. Has been applied. Therefore, based on the thermoelectric characteristics and mechanical strength of the thermoelectric semiconductor member 1, the characteristics (cooling characteristics, etc.) and reliability of the thermoelectric element 21 can be greatly improved. The thermoelectric element 21 is suitable for a cooling device in various fields such as a temperature control device for a cold storage room or a semiconductor manufacturing apparatus, a cooling device for a highly heat-generating semiconductor component such as an ultra-high integrated circuit element such as a CPU of a computer, or a laser element. It is used.
[0044]
In the above-described embodiment, the structure in which the support members 22 and 23 of the thermoelectric element 21 are arranged on the upper and lower surfaces of the thermoelectric semiconductors 24 and 25 has been described. However, the present invention is not limited to such a structure, and the element structure It is also possible to apply the structural support member (corresponding to the lower support member 2 in FIG. 1) for holding the thermoelectric element 1 disposed at an intermediate position between the N-type thermoelectric semiconductor and the P-type thermoelectric semiconductor. Moreover, although embodiment mentioned above demonstrated the case where the thermoelectric-semiconductor member 1 of this invention was applied to the thermoelectric element (cooling element) using the Peltier effect, the thermoelectric-semiconductor member 1 of this invention is a thermoelectric using the Seebeck effect. It is also possible to apply to an element (power generation element), and even in that case, improvement in element characteristics and reliability can be achieved.
[0045]
【Example】
Next, specific examples of the present invention will be described.
[0046]
Example 1
First, Bi_0.4Sb_1.6Te_ThreeAn alloy ingot having a composition was melted and the molten alloy was rapidly cooled by a single roll method to produce an alloy ribbon having an average thickness of about 90 μm and an average crystal grain size of 35 μm. The obtained alloy ribbon was composed of columnar crystals (the volume ratio of the columnar crystals was 90%) in which most crystal grains extend in the thickness direction. The alloy ribbon was pulverized to 32 mesh or less to obtain a flaky alloy piece.
[0047]
Next, the flake-shaped alloy piece was heated to 500 ° C. in an Ar gas atmosphere, and then inserted into a mold container having an inner diameter of 30 mm preheated to 500 ° C. A rod-shaped hot extruded material having a diameter of 8 mm was produced by immediately extruding from a hole having a diameter of 8 mm with a punch preheated to 500 ° C. The extrusion ratio at this time is 14. Note that boron nitride powder was previously applied to the mold container and the punch.
[0048]
After this, the rod-shaped hot extruded material was heat-treated in an Ar gas atmosphere at 400 ° C. for 2 hours, and further shaped to 1.5 × 1.5 × 2 mm (extrusion direction is 2 mm height) The desired Bi by processing into_0.4Sb_1.6Te_ThreeA thermoelectric semiconductor member made of a hot extruded material of the alloy was obtained. This thermoelectric semiconductor member uses a direction of 2 mm height (extrusion direction) as a current direction. Further, when the crystal structure of the thermoelectric semiconductor member was observed, crystal grains extending in the extrusion direction were observed throughout the structure, and the average aspect ratio (A / B ratio) of the crystal grains was 1.8. The average crystal grain size after the heat treatment was 13 μm. When the Seebeck coefficient and resistance value of such a thermoelectric semiconductor member were measured, 221 μV / K, 1.11 × 10 respectively^-FiveIt was Ω · m. In addition, the current direction at the time of these characteristic evaluations was the direction (extrusion direction) 2 mm in height of the thermoelectric semiconductor member.
[0049]
Example 2
In Example 1 described above, Bi was changed in the same manner as in Example 1 except that the extrusion ratio during hot extrusion was changed to 25._0.4Sb_1.6Te_ThreeA thermoelectric semiconductor member made of a hot extruded material of the alloy was obtained. When the crystal structure of this thermoelectric semiconductor member was observed, crystal grains extending in the extrusion direction were observed throughout the structure, and the average aspect ratio (A / B ratio) of the crystal grains was 4.3. The average crystal grain size after the heat treatment was 9 μm. When the Seebeck coefficient and resistance value of such a thermoelectric semiconductor member were measured in the same manner as in Example 1, they were 228 μV / K and 1.15 × 10 respectively.^-FiveIt was Ω · m.
[0050]
Example 3
In Example 2 described above, Bi was changed in the same manner as in Example 2 except that the heat treatment condition for the hot-extruded material was changed to 300 ° C. × 20 hours._0.4Sb_1.6Te_ThreeA thermoelectric semiconductor member made of a hot extruded material of the alloy was obtained. The average crystal grain size after heat treatment of this thermoelectric semiconductor member was 83 μm. When the Seebeck coefficient and resistance value of such a thermoelectric semiconductor member were measured in the same manner as in Example 1, they were 213 μV / K and 1.21 × 10 6 respectively.^-FiveIt was Ω · m.
[0051]
Comparative Example 1
In Example 1 described above, Bi was changed in the same manner as in Example 1 except that the extrusion ratio during hot extrusion was changed to 6.3._0.4Sb_1.6Te_ThreeA thermoelectric semiconductor member made of a hot extruded material of the alloy was obtained. When the crystal structure of this thermoelectric semiconductor member was observed, the crystal grains were found to partially extend in the extrusion direction, but the average aspect ratio (A / B ratio) of the crystal grains was 1.4. The average crystal grain size after the heat treatment was 35 μm. When the Seebeck coefficient and the resistance value of such a thermoelectric semiconductor member were measured in the same manner as in Example 1, they were 202 μV / K and 2.01 × 10 respectively.^-FiveIt was Ω · m.
[0052]
Comparative Example 2
In Example 1 described above, Bi was changed in the same manner as in Example 1 except that the heat treatment condition for the hot-extruded material was changed to 300 ° C. × 100 hours._0.4Sb_1.6Te_ThreeA thermoelectric semiconductor member made of a hot extruded material of the alloy was obtained. The average crystal grain size of this thermoelectric semiconductor member after heat treatment was 115 μm. When the Seebeck coefficient and the resistance value of such a thermoelectric semiconductor member were measured in the same manner as in Example 1, they were 201 μV / K and 1.42 × 10 respectively.^-FiveIt was Ω · m.
[0053]
Example 4
An alloy ingot having the same composition as in Example 1 was melted and the molten alloy was rapidly cooled by a twin roll method to produce an alloy ribbon having an average thickness of about 250 μm and an average crystal grain size of 40 μm. The obtained alloy ribbon was mainly composed of columnar crystals extending in the thickness direction, and the volume ratio of the columnar crystals was 55%. The alloy ribbon was pulverized to 32 mesh or less to obtain a flaky alloy piece. Next, this flaky alloy piece was hot-extruded under the same conditions as in Example 1 to produce a rod-shaped hot-extruded material having a diameter of 8 mm.
[0054]
Thereafter, the above-described rod-like hot extruded material is heat-treated in an Ar gas atmosphere at 300 ° C. for 2 hours, and further processed into the same shape as in Example 1, thereby obtaining the target Bi._0.4Sb_1.6Te_ThreeA thermoelectric semiconductor member made of a hot extruded material of the alloy was obtained. When the crystal structure of this thermoelectric semiconductor member was observed, crystal grains extending in the extrusion direction were observed throughout the structure, and the average aspect ratio (A / B ratio) of the crystal grains was 1.6. The average crystal grain size after the heat treatment was 15 μm. When the Seebeck coefficient and resistance value of this thermoelectric semiconductor member were measured in the same manner as in Example 1, they were 212 μV / K and 1.09 × 10 respectively.^-FiveIt was Ω · m.
[0055]
Comparative Example 3
In Example 3 described above, Bi was used in the same manner as Example 3 except that an alloy ribbon (quenched ribbon) having a volume ratio of columnar crystals of 45% was used as a raw material._0.4Sb_1.6Te_ThreeA thermoelectric semiconductor member made of a hot extruded material of the alloy was obtained. When the crystal structure of the thermoelectric semiconductor member was observed, crystal grains extending in the extrusion direction were observed, but the average aspect ratio (A / B ratio) of the crystal grains was 1.4. The average crystal grain size after the heat treatment was 15 μm. When the Seebeck coefficient and resistance value of this thermoelectric semiconductor member were measured in the same manner as in Example 1, they were 198 μV / K and 1.09 × 10 6 respectively.^-FiveIt was Ω · m.
[0056]
Example 5
An alloy ingot having the same composition as in Example 1 was melted, and the molten alloy was quenched by a strip casting method to produce an alloy ribbon having an average thickness of about 300 μm and an average crystal grain size of 195 μm. The obtained alloy ribbon was mainly composed of columnar crystals extending in the thickness direction, and the volume ratio of the columnar crystals was 95%. The alloy ribbon was pulverized to 32 mesh or less to obtain a flaky alloy piece. Next, this flaky alloy piece was hot-extruded under the same conditions as in Example 1 to produce a rod-shaped hot-extruded material having a diameter of 8 mm.
[0057]
Thereafter, the above-described rod-like hot extruded material is heat-treated in an Ar gas atmosphere at 300 ° C. for 2 hours, and further processed into the same shape as in Example 1, thereby obtaining the target Bi._0.4Sb_1.6Te_ThreeA thermoelectric semiconductor member made of a hot extruded material of the alloy was obtained. When the crystal structure of this thermoelectric semiconductor member was observed, crystal grains extending in the extrusion direction were observed throughout the structure, and the average aspect ratio (A / B ratio) of the crystal grains was 1.8. The average crystal grain size after the heat treatment was 14 μm. When the Seebeck coefficient and resistance value of this thermoelectric semiconductor member were measured in the same manner as in Example 1, they were 209 μV / K and 1.08 × 10 respectively.^-FiveIt was Ω · m.
[0058]
referenceExample1
  An alloy ingot having the same composition as in Example 1 was melted, and the molten alloy was quenched by a gas atomization method, thereby producing an alloy quenched ball powder having an average particle size of 105 μm and an average crystal grain size of 5 μm. The obtained alloy quenched ball powder consisted of columnar crystals with most crystal grains extending from the center. The volume ratio of the columnar crystals was 90%. Except using this alloy quenching ball powder, it hot-extruded on the same conditions as Example 1, and produced the rod-shaped hot extrusion molding material of diameter 8mm.
[0059]
Thereafter, the above-described rod-like hot extruded material is heat-treated in an Ar gas atmosphere at 300 ° C. for 2 hours, and further processed into the same shape as in Example 1, thereby obtaining the target Bi._0.4Sb_1.6Te_ThreeA thermoelectric semiconductor member made of a hot extruded material of the alloy was obtained. When the crystal structure of this thermoelectric semiconductor member was observed, crystal grains extending in the extrusion direction were observed throughout the structure, and the average aspect ratio (A / B ratio) of the crystal grains was 1.7. The average crystal grain size after the heat treatment was 19 μm. When the Seebeck coefficient and resistance value of this thermoelectric semiconductor member were measured in the same manner as in Example 1, they were 210 μV / K and 1.02 × 10 respectively.^-FiveIt was Ω · m.
[0060]
Example6
  An alloy ribbon manufactured under the same conditions as in Example 1 was placed in a vacuum furnace, the furnace was evacuated and then heated, and hydrogen was introduced to atmospheric pressure at 380 ° C. and held for 10 minutes, and then evacuated It was. By repeating this operation 10 times, an alloy powder having an average particle size of 42 μm was obtained. Except for using this alloy powder, hot extrusion molding was performed under the same conditions as in Example 1 to prepare a rod-shaped hot extrusion molding material having a diameter of 8 mm.
[0061]
Thereafter, the above-described rod-like hot extruded material is heat-treated in an Ar gas atmosphere at 300 ° C. for 2 hours, and further processed into the same shape as in Example 1, thereby obtaining the target Bi._0.4Sb_1.6Te_ThreeA thermoelectric semiconductor member made of a hot extruded material of the alloy was obtained. When the crystal structure of this thermoelectric semiconductor member was observed, crystal grains extending in the extrusion direction were observed throughout the structure, and the average aspect ratio (A / B ratio) of the crystal grains was 1.8. The average crystal grain size after the heat treatment was 13 μm. When the Seebeck coefficient and resistance value of this thermoelectric semiconductor member were measured in the same manner as in Example 1, they were 224 μV / K and 1.10 × 10 respectively.^-FiveIt was Ω · m.
[0062]
Example7
  The flake-like alloy piece produced under the same conditions as in Example 1 and carbon powder were mixed at a volume ratio of 94: 6. Except for using this mixture, hot extrusion molding was performed under the same conditions as in Example 1 to produce a rod-shaped hot extrusion molding material having a diameter of 8 mm. Thereafter, the above-described rod-shaped hot extrusion molded material is heat-treated in an Ar gas atmosphere at 300 ° C. for 2 hours, and further processed into the same shape as in Example 1, thereby achieving the target Bi._0.4Sb_1.6Te₃A thermoelectric semiconductor member made of a hot extruded material of the alloy was obtained.
[0063]
When the crystal structure of the thermoelectric semiconductor member thus obtained was observed, crystal grains extending in the extrusion direction were observed throughout the structure, and the average aspect ratio (A / B ratio) of the crystal grains was 1.9. The average crystal grain size after the heat treatment was 15 μm. When the Seebeck coefficient and resistance value of this thermoelectric semiconductor member were measured in the same manner as in Example 1, they were 220 μV / K and 1.05 × 10 respectively.^-FiveIt was Ω · m. The Seebeck coefficient and resistance value of the thermoelectric semiconductor member when boron nitride powder is mixed instead of carbon powder are 217 μV / K and 1.12 × 10, respectively.^-FiveIt was Ω · m.
[0064]
As described above, it was confirmed that extrudability was improved by mixing carbon powder or boron nitride powder as a lubricant. Specifically, it was confirmed that even when the hot extrusion temperature was lowered by 50 ° C., extrusion could be carried out satisfactorily and the Seebeck coefficient and resistance value of the thermoelectric semiconductor member were hardly changed. If the hot extrusion temperature was lowered by 50 ° C. when no lubricant was added, cracks were likely to occur during extrusion molding, and the characteristic values also decreased.
[0065]
Comparative Example 4
An alloy ingot having the same composition as in Example 1 was produced by a casting method, and the alloy ingot was pulverized so that the average particle size was 106 μm or less. After heating this alloy powder to 500 ° C in an Ar gas atmosphere, it is inserted into a hot press mold and 2 ton / cm.²Hot press molding was performed at a pressure of. The crystal structure of this thermoelectric semiconductor member was isotropic, and the average aspect ratio (A / B ratio) of the crystal grains was 1.1. When the Seebeck coefficient and resistance value of such a thermoelectric semiconductor member were measured, 172 μV / K, 1.07 × 10 respectively^-FiveIt was Ω · m. Furthermore, the obtained thermoelectric semiconductor member had a lower mechanical strength and a lower thermal conductivity than the members of the examples.
[0066]
Example8
  In the same manner as the thermoelectric semiconductor member of each example described above, Bi28at. % -Te57at. % -Sb12at. % -Se3at. % Composition N-type thermoelectric semiconductor member, Bi10 at. % -Te57at. % -Sb10 at. % -Se3at. % P-type thermoelectric semiconductor members were produced, and the thermoelectric elements shown in FIG. 4 were produced. The N-type and P-type thermoelectric semiconductor members are processed so that the extrusion direction of the hot extrusion molding material is the member longitudinal direction (current direction). It arrange | positioned between the heat absorption side electrode and the heat radiation side electrode according to. When each thermoelectric element thus obtained was energized and its thermoelectric characteristics and reliability were evaluated, it was confirmed that good results were obtained.
[0067]
【The invention's effect】
As described above, according to the thermoelectric semiconductor member of the present invention, the manufacturing cost of the thermoelectric semiconductor applied to a thermoelectric element or the like is reduced, and the crystal orientation and mechanical characteristics thereof are excellent and reproducible. It becomes possible to raise well. Therefore, according to the thermoelectric element to which such a thermoelectric semiconductor member is applied, thermoelectric characteristics and reliability can be improved. That is, it becomes possible to provide a thermoelectric element having excellent thermoelectric characteristics and reliability with high reproducibility.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an appearance of a thermoelectric semiconductor member according to an embodiment of the present invention.
2 is an enlarged schematic view showing the microstructure of the thermoelectric semiconductor member (hot extruded material) shown in FIG. 1. FIG.
FIG. 3 is a diagram for explaining a hot extrusion state and hot extrusion conditions of the thermoelectric semiconductor member shown in FIG. 1;
FIG. 4 is a cross-sectional view showing a schematic structure of a thermoelectric element according to an embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Thermoelectric semiconductor member, 1a ... Hot extrusion molding material, 21 ... Thermoelectric element, 22 ... Lower support member, 23 ... Upper support member, 24 ... N type thermoelectric semiconductor, 25 ... P type thermoelectric Semiconductor, 26 ... Discharge side electrode, 27 ... Endothermic side electrode, 30 ... DC power supply

Claims

The Bi-Te based thermoelectric semiconductor of the molten metal more rapidly cooled to a single roll method or a double roll method, along with containing 50% or more columnar crystals by volume, producing a flaky melt-quenching material average crystal grain size of 500μm or less And a process of
A mold container preheated to a temperature similar to that of the thermoelectric semiconductor melt quenching material after heating the thermoelectric semiconductor melt quenching material to a temperature in the range of 400 ° C or higher and 30 ° C lower than the melting point of the thermoelectric semiconductor The average aspect ratio (A / B) expressed by the ratio of the dimension A in the extrusion direction during hot extrusion and the dimension B in the direction perpendicular to the extrusion direction is 1. Producing a hot extrusion molding material having 5 or more crystal grains;
Processing the hot extruded material into a desired member shape ;
And a step of heat-treating the hot-extruded material at a temperature in the range of 250 to 550 ° C.

In the manufacturing method of the thermoelectric-semiconductor member of Claim 1 ,
The hot-electric-extruded material is processed into the member shape so that the direction substantially parallel to the longitudinal direction of the crystal grains constituting the hot-extruded material is the current direction. Manufacturing method of member.

In the manufacturing method of the thermoelectric-semiconductor member of Claim 1 or Claim 2 ,
A method for producing a thermoelectric semiconductor member, comprising: mixing the molten metal quenching material of the thermoelectric semiconductor with 5% by volume or less of a lubricant, and then performing the hot extrusion molding.