JP3515478B2 - Thermoelectric conversion material, thermoelectric conversion element, thermal battery and cooler - Google Patents
Thermoelectric conversion material, thermoelectric conversion element, thermal battery and coolerInfo
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- JP3515478B2 JP3515478B2 JP2000095176A JP2000095176A JP3515478B2 JP 3515478 B2 JP3515478 B2 JP 3515478B2 JP 2000095176 A JP2000095176 A JP 2000095176A JP 2000095176 A JP2000095176 A JP 2000095176A JP 3515478 B2 JP3515478 B2 JP 3515478B2
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- thermoelectric conversion
- conversion material
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- thermoelectric
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Description
【０００１】[0001]
【発明の属する技術分野】本発明は、熱電冷却素子や熱
電発電素子に好適な酸化物系熱電変換材料と、前記熱電
変換材料を具備した熱電変換素子と、前記熱電変換素子
を具備した熱電池及び冷却器に関するものである。TECHNICAL FIELD The present invention relates to an oxide-based thermoelectric conversion material suitable for a thermoelectric cooling element or a thermoelectric power generation element, a thermoelectric conversion element including the thermoelectric conversion material, and a thermoelectric cell including the thermoelectric conversion element. And a cooler.
【０００２】[0002]
【従来の技術】近年、地球環境問題に対する意識の高揚
から、フロンを使用した冷却機器の代替品として、ペル
チェ効果を利用した熱電冷却材料に関する関心が高まっ
ている。また、二酸化炭素排出量を削減するために、こ
れまで利用されていなかった廃熱エネルギーを使った発
電システムに対する関心が高まっている。室温付近で利
用されている熱電冷却材料並びに熱電発電材料は、効率
の高さから、Ｂｉ−Ｔｅ系の単結晶または多結晶体を使
用したものが多い。この材料を用いて熱電素子化するた
めには、ｐ型、ｎ型両材料が必要となる。このうちｎ型
材料にはＳｅが含有されている。また室温より高温で使
用される熱電材料には、やはり効率の高さから、Ｐｂ−
Ｔｅ系が用いられている。2. Description of the Related Art In recent years, attention is being paid to a thermoelectric cooling material utilizing the Peltier effect as a substitute for a cooling device using CFCs due to the heightened awareness of global environmental problems. Moreover, in order to reduce carbon dioxide emissions, there is an increasing interest in power generation systems that use waste heat energy that has not been used until now. Most of thermoelectric cooling materials and thermoelectric power generating materials used near room temperature use Bi-Te based single crystals or polycrystals because of their high efficiency. Both p-type and n-type materials are required to form a thermoelectric element using this material. Of these, the n-type material contains Se. Also, for thermoelectric materials used at temperatures higher than room temperature, Pb-
Te system is used.
【０００３】これら素子に含有されている、Ｓｅ（セレ
ン）、Ｐｂ（鉛）、Ｔｅ（テルル）などは人体にとって
有毒有害であり、また地球環境問題の観点からも好まし
くない。このため、これまでＢｉ−Ｔｅ系、Ｐｂ−Ｔｅ
系より高効率で、かつ無害な材料の検討がなされてい
る。Se (selenium), Pb (lead), Te (tellurium), etc. contained in these elements are toxic and harmful to the human body and are not preferable from the viewpoint of global environmental problems. Therefore, so far, Bi-Te system, Pb-Te system
Materials that are more efficient than the system and harmless are being studied.
【０００４】元素組成式ＮａＣｏ2Ｏ4-Yで表される物質
はJansenらによって、Z.Anorg.Allg.Chem. 408, 104(19
74)に報告されている。この化合物は、図６に示すよう
に、ブロンズ型の層状構造を有し、稜を共有するＣｏＯ
6八面体からなるＣｏＯ2シート２１がｃ軸方向に積み重
なり、Ｎａイオン２２がＣｏＯ2シート面間に占有率５
０％で存在している。なお、図６において、付番２３は
Ｃｏ原子を示し、付番２４はＯ原子を示す。A substance represented by the elemental composition formula NaCo 2 O 4-Y is described by Jansen et al. In Z. Anorg. Allg. Chem. 408, 104 (19).
74). As shown in FIG. 6, this compound has CoO having a bronze type layered structure and sharing edges.
6 octahedral CoO 2 sheets 21 are stacked in the c-axis direction, and Na ions 22 occupy 5 between the CoO 2 sheet surfaces.
It is present at 0%. In addition, in FIG. 6, number 23 indicates a Co atom and number 24 indicates an O atom.
【０００５】一方、特開平１０−２５６６１２号公開公
報には、元素組成式Ｎａ（ＣｏzＡ1 -z）xＯyで表される
物質からなる熱電変換材料が開示されている。但し、ｘ
は１≦ｘ≦２、ｙは２≦ｙ≦４、ｚは０＜ｚ＜１であ
り、ＡはＭｎ、ＦｅまたはＣｕである。On the other hand, Japanese Unexamined Patent Publication No. 10-256612 discloses a thermoelectric conversion material composed of a substance represented by the elemental composition formula Na (Co z A 1 -z ) x O y . However, x
Is 1 ≦ x ≦ 2, y is 2 ≦ y ≦ 4, z is 0 <z <1, and A is Mn, Fe or Cu.
【０００６】また、特開平９−３２１３４６号公開公報
には、Ｆｅ、Ｃｏ及びＮｉからなる群から選ばれた３ｄ
遷移金属元素を含む複合酸化物（但し、複合酸化物を構
成する他の元素はＬｉ、Ｎａ、Ｋからなる群から選ばれ
た元素、またはＬｉ、Ｎａ、Ｋからなる群から選ばれた
元素及びＭｇ、Ｃａ、Ｓｒ、Ｂａ、Ｓｃ、Ｙ、Ｂｉ及び
Ｔｅからなる群から選ばれた元素である）からなる熱電
変換材料が記載されている。この熱電変換材料では、特
許請求の範囲、段落｛００２２｝、｛００２７｝及び
｛００４０｝に記載されているように、３ｄ遷移金属と
混合する他の元素であるＬｉ、Ｎａ及びＫをそれぞれ単
独で用いている。Further, Japanese Patent Laid-Open No. 9-321346 discloses 3d selected from the group consisting of Fe, Co and Ni.
A complex oxide containing a transition metal element (provided that the other elements constituting the complex oxide are elements selected from the group consisting of Li, Na and K, or elements selected from the group consisting of Li, Na and K, and Thermoelectric conversion material composed of Mg, Ca, Sr, Ba, Sc, Y, Bi, and Te). In this thermoelectric conversion material, as described in the claims and the paragraphs {0022}, {0027} and {0040}, Li, Na and K, which are other elements mixed with the 3d transition metal, are used alone. Used in.
【０００７】ところで、熱電材料の性能指数Ｚは下記式
（２）で表される。By the way, the figure of merit Z of the thermoelectric material is expressed by the following equation (2).
【０００８】Ｚ＝α2σ／κ …（２）
ここで、αは熱電材料のゼーベック係数、σは熱電材料
の導電率、κは熱電材料の熱伝導率である。Ｚは温度の
逆数の次元であり、このＺと熱電材料の熱電変換効率は
相関する。従って、性能指数Ｚが大きいほど、熱電材料
としての特性に優れている。これまで報告されている熱
電材料には、Ｚが室温で３．３×１０-3を越えるものは
なかった。この（２）式から、ゼーベック係数αが同じ
であっても、導電率σが大きく、かつ熱伝導率κが小さ
い方が性能指数Ｚが大きくなることがわかる。Z = α 2 σ / κ (2) where α is the Seebeck coefficient of the thermoelectric material, σ is the electrical conductivity of the thermoelectric material, and κ is the thermal conductivity of the thermoelectric material. Z is the dimension of the reciprocal of temperature, and this Z correlates with the thermoelectric conversion efficiency of the thermoelectric material. Therefore, the larger the figure of merit Z, the better the characteristics as a thermoelectric material. None of the thermoelectric materials reported so far has Z exceeding 3.3 × 10 −3 at room temperature. From this equation (2), it can be seen that even if the Seebeck coefficient α is the same, the figure of merit Z becomes larger as the electrical conductivity σ is larger and the thermal conductivity κ is smaller.
【０００９】前述した特開平９−３２１３４６号公報に
記載された熱電変換材料は、液体窒素温度から４００℃
以上の広い温度範囲で使用可能で、毒性がないものの、
単結晶および多結晶いずれの形態においても熱電特性に
優れない。すなわち、段落｛００３４｝に記載されてい
るように、ＮａＣｏ2Ｏｙ（ｙはほぼ４）で表される多
結晶体からなる熱電変換材料の場合、ゼーベック係数α
は１００μＶ／Ｋと大きく、熱伝導率κは１．５〜２Ｗ
／ｍＫと低いものの、抵抗率は２ｍΩｃｍと大きくなる
ため、熱電材料としての特性に優れない。一方、単結晶
体については、本発明者らが特開平９−３２１３４６号
公報の実施例3に記載された方法と同様にしてＮａxＣｏ
2Ｏ4-Y単結晶を作製し、抵抗率及び熱伝導率を調査した
ところ、抵抗率は多結晶体より低くなるものの、熱伝導
率が多結晶体に比較して１０倍以上の値を示したため、
優れた熱電特性が得られなかった。これは、単結晶が多
結晶体に比較して結晶粒界が無いために抵抗率を低くす
ることができるものの、結晶粒界による熱抵抗が無くな
るために熱伝導率が増加したためであるものと考えられ
る。The thermoelectric conversion material described in the above-mentioned Japanese Patent Laid-Open No. 9-321346 has a liquid nitrogen temperature of 400 ° C.
Although it can be used in the wide temperature range above and is not toxic,
Thermoelectric properties are not excellent in both single crystal and polycrystal forms. That is, as described in paragraph {0034}, in the case of a thermoelectric conversion material composed of a polycrystalline body represented by NaCo 2 O y (y is approximately 4), the Seebeck coefficient α
Is as large as 100 μV / K, and the thermal conductivity κ is 1.5-2 W
Although it is as low as / mK, the resistivity is as high as 2 mΩcm, and thus the characteristics as a thermoelectric material are not excellent. On the other hand, regarding the single crystal body, the present inventors conducted Na x Co in the same manner as the method described in Example 3 of JP-A-9-321346.
When 2 O 4-Y single crystal was produced and the resistivity and thermal conductivity were investigated, the resistivity was lower than that of the polycrystalline body, but the thermal conductivity was 10 times or more that of the polycrystalline body. For showing,
Excellent thermoelectric properties could not be obtained. This is because the single crystal has a lower resistance because it has no crystal grain boundary than a polycrystal, but the thermal conductivity is increased because the thermal resistance due to the crystal grain boundary disappears. Conceivable.
【００１０】[0010]
【発明が解決しようとする課題】本発明は、熱伝導率が
低く、熱電変換効率が高く、かつ毒性の低い熱電変換材
料を提供することを目的とする。SUMMARY OF THE INVENTION An object of the present invention is to provide a thermoelectric conversion material having low thermal conductivity, high thermoelectric conversion efficiency and low toxicity.
【００１１】また、本発明は、熱電変換特性に優れる熱
電変換素子、熱電池及び冷却器を提供することを目的と
する。Another object of the present invention is to provide a thermoelectric conversion element, a thermal battery and a cooler which are excellent in thermoelectric conversion characteristics.
【００１２】[0012]
【課題を解決するための手段】本発明に係る熱電変換材
料は、下記（１）の化学式で表される組成を有すること
を特徴とするものである。The thermoelectric conversion material according to the present invention is characterized by having a composition represented by the following chemical formula (1).
【００１３】
ＮａαＭXＡYＯ4-Z …（１）
但し、前記Ｍは、Ｋ、Ｒｂ及びＣｓよりなる群から選ば
れる１種類以上のアルカリ金属元素からなり、前記Ａ
は、Ｃｏ、Ｆｅ、ＮｉおよびＣｕよりなる群から選ばれ
る１種類以上の元素からなり、モル比α、Ｘ、Ｙ及びＺ
は、０＜α＜１．２、０．１≦Ｘ≦１、０．７≦α＋Ｘ
≦１．２、０＜Ｙ、０≦Ｚを示す。Na α M X A Y O 4-Z (1) where M is one or more kinds of alkali metal elements selected from the group consisting of K, Rb and Cs,
Is composed of one or more elements selected from the group consisting of Co, Fe, Ni and Cu, and has a molar ratio α, X, Y and Z.
Is 0 <α <1.2, 0.1 ≦ X ≦ 1, 0.7 ≦ α + X
≦ 1.2, 0 <Y, and 0 ≦ Z are shown.
【００１４】本発明に係る熱電変換素子は、前記（１）
の化学式で表される組成を有する熱電変換材料の本体
と、前記本体に接続され、電力を取り出すための電極対
とを含むことを特徴とするものである。The thermoelectric conversion element according to the present invention has the above (1).
The thermoelectric conversion material has a main body having a composition represented by the following chemical formula, and an electrode pair connected to the main body for taking out electric power.
【００１５】本発明に係る熱電池は、前記（１）の化学
式で表される組成を有する熱電変換材料の本体と、前記
本体に接続され、電力を取り出すための電極対とを含む
熱電変換素子を具備したことを特徴とするものである。The thermal battery according to the present invention comprises a thermoelectric conversion element including a main body of a thermoelectric conversion material having a composition represented by the chemical formula (1) above and an electrode pair connected to the main body for taking out electric power. It is characterized by having.
【００１６】本発明に係る冷却器は、前記（１）の化学
式で表される組成を有する熱電変換材料の本体と、前記
本体に接続され、電力を印加するための電極対とを含む
熱電変換素子を具備したことを特徴とするものである。The cooler according to the present invention includes a body of thermoelectric conversion material having a composition represented by the chemical formula (1) and a pair of electrodes connected to the body for applying electric power. It is characterized by including an element.
【００１７】[0017]
【発明の実施の形態】まず、本発明に係る熱電変換材料
について説明する。First, the thermoelectric conversion material according to the present invention will be described.
【００１８】＜熱電変換材料＞この熱電変換材料は、下
記（１）の化学式で表される組成を有する。<Thermoelectric Conversion Material> This thermoelectric conversion material has a composition represented by the chemical formula (1) below.
【００１９】
ＮａαＭXＡYＯ4-Z …（１）
但し、前記Ｍは、Ｋ、Ｒｂ及びＣｓよりなる群から選ば
れる１種類以上のアルカリ金属元素からなり、前記Ａ
は、Ｃｏ、Ｆｅ、ＮｉおよびＣｕよりなる群から選ばれ
る１種類以上の元素からなり、モル比α、Ｘ、Ｙ及びＺ
は、０＜α＜１．２、０．１≦Ｘ≦１、０．７≦α＋Ｘ
≦１．２、０＜Ｙ、０≦Ｚを示す。Na α M X A Y O 4-Z (1) where M is one or more kinds of alkali metal elements selected from the group consisting of K, Rb and Cs,
Is composed of one or more elements selected from the group consisting of Co, Fe, Ni and Cu, and has a molar ratio α, X, Y and Z.
Is 0 <α <1.2, 0.1 ≦ X ≦ 1, 0.7 ≦ α + X
≦ 1.2, 0 <Y, and 0 ≦ Z are shown.
【００２０】Ｍのモル比Ｘを前記範囲に規定するのは次
のような理由によるものである。モル比Ｘを０．１未満
にすると、熱電変換材料の熱伝導率を低くすることが困
難になる。一方、モル比Ｘが１．０を超えると、熱電変
換材料の抵抗率が高くなって熱電変換効率が低下する。
モル比Ｘのより好ましい範囲は、０．２≦Ｘ≦０．８で
ある。また、元素Ｍのうち、Ｒｂや、Ｃｓは、Ｋに比べ
て熱伝導率を下げる効果が高い。The reason for defining the molar ratio X of M within the above range is as follows. When the molar ratio X is less than 0.1, it becomes difficult to reduce the thermal conductivity of the thermoelectric conversion material. On the other hand, when the molar ratio X exceeds 1.0, the resistivity of the thermoelectric conversion material increases and the thermoelectric conversion efficiency decreases.
A more preferable range of the molar ratio X is 0.2 ≦ X ≦ 0.8. Further, among the elements M, Rb and Cs have a higher effect of lowering the thermal conductivity than K.
【００２１】Ｎａ及びＭの合計モル比（α＋Ｘ）を前記
範囲に規定するのは次のような理由によるものである。
合計モル比（α＋Ｘ）を０．７未満にすると、フォノン
を散乱させるＡＯ2層間原子が少なくなるため、熱伝導
率が大きくなり、熱電特性が劣化する。一方、合計モル
比（α＋Ｘ）が１．２を超えると、層間原子間の斥力が
強く働くようになるため、層間が押し広げられて結晶構
造が不安定になり、高抵抗による熱電特性の劣化を生じ
る。合計モル比（α＋Ｘ）のより好ましい範囲は、０．
８≦α＋Ｘ≦１．１である。さらに好ましくは、１に近
い値である。The reason for defining the total molar ratio (α + X) of Na and M within the above range is as follows.
When the total molar ratio (α + X) is less than 0.7, the number of AO 2 interlayer atoms that scatter phonons decreases, so that the thermal conductivity increases and the thermoelectric characteristics deteriorate. On the other hand, when the total molar ratio (α + X) exceeds 1.2, the repulsive force between the interatomic atoms becomes strong, so that the interlaminar layers are spread and the crystal structure becomes unstable, and the thermoelectric properties deteriorate due to high resistance. Cause A more preferable range of the total molar ratio (α + X) is 0.
8 ≦ α + X ≦ 1.1. More preferably, the value is close to 1.
【００２２】元素Ａとしては、Ｃｏを用いることが好ま
しい。また、元素Ａのモル比Ｙは２にすることが好まし
い。As the element A, it is preferable to use Co. Further, the molar ratio Y of the element A is preferably 2.
【００２３】モル比Ｚは、０≦Ｚ≦１の範囲内にするこ
とが好ましく、さらに０に近い値であることがより好ま
しい。The molar ratio Z is preferably in the range of 0≤Z≤1, and more preferably close to 0.
【００２４】この熱電変換材料は、稜を共有するＡＯ6
八面体からなるＡＯ2層がｃ軸方向に積層され、前記Ｎ
ａ元素及び前記Ｍ元素がＡＯ2層間に占有率（５０×
（α＋Ｘ））％で存在している結晶構造を有する。但
し、（α＋Ｘ）は前記Ｎａ元素及び前記Ｍ元素のモル比
の合計値を表わす。元素ＡがＣｏである場合を図１に示
す。図１に示すように、稜を共有するＣｏＯ6八面体か
らなるＣｏＯ2層１がｃ軸方向に積層されている。な
お、ＣｏＯ2層１中のＣｏ原子を２、Ｏ原子を３とす
る。Ｋ、Ｒｂ及びＣｓよりなる群から選ばれる１種類以
上からなるアルカリ金属イオン４及びＮａイオン５は、
前記ＣｏＯ2層間に占有率（５０×（α＋Ｘ））％で存
在している。This thermoelectric conversion material is made of AO 6 which shares a ridge.
An AO 2 layer composed of octahedra is laminated in the c-axis direction,
The a element and the M element have an occupation ratio (50 ×) between the AO 2 layers.
It has a crystal structure present at (α + X))%. However, (α + X) represents the total value of the molar ratio of the Na element and the M element. The case where the element A is Co is shown in FIG. As shown in FIG. 1, a CoO 2 layer 1 composed of a CoO 6 octahedron sharing a ridge is laminated in the c-axis direction. The Co atoms in the CoO 2 layer 1 are 2 and the O atoms are 3. Alkali metal ion 4 and Na ion 5 consisting of one or more selected from the group consisting of K, Rb and Cs,
Occupancy (50 × (α + X))% exists between the CoO 2 layers.
【００２５】本発明に係る熱電変換材料には、単結晶
と、多結晶体がある。このうち、元素ＡとしてＣｏを含
む単結晶は、以下に説明するフラックス法で作製される
ことが望ましい。The thermoelectric conversion material according to the present invention includes a single crystal and a polycrystal. Among these, the single crystal containing Co as the element A is preferably produced by the flux method described below.
【００２６】すなわち、原料粉のうちナトリウム成分と
しては、Ｎａ2Ｏ、Ｎａ2Ｏ2、ＮａＨＣＯ3、ＮａＨＮＨ
4、Ｎａ2Ｃｏ3などが好ましい。カリウム成分として
は、Ｋ 2Ｏ、Ｋ2Ｏ2、ＫＨＣＯ3、ＫＨＮＨ4、Ｋ2ＣＯ3
などが好ましい。ルビジウム成分としては、Ｒｂ2Ｏ、
Ｒｂ2Ｏ2、ＲｂＨＣＯ3、ＲｂＨＮＨ4、Ｒｂ2ＣＯ3など
が好ましい。セシウム成分としては、Ｃｓ2Ｏ、ＣｓＨ
ＣＯ3、ＣｓＨＮＨ4、Ｃｓ2Ｃｏ3などが好ましい。ただ
し、アルカリ金属の過酸化物は爆発性があるために危険
性が高く、原料としてはあまり好ましくない。That is, the sodium component of the raw material powder
And then Na2O, Na2O2, NaHCO3, NaHNH
Four, Na2Co3Are preferred. As a potassium component
Is K 2O, K2O2, KHCO3, KHNHFour, K2CO3
Are preferred. As a rubidium component, Rb2O,
Rb2O2, RbHCO3, RbHNHFour, Rb2CO3Such
Is preferred. As the cesium component, Cs2O, CsH
CO3, CsHNHFour, Cs2Co3Are preferred. However
However, alkali metal peroxides are dangerous because they are explosive.
It is highly unpreferable as a raw material.
【００２７】コバルト成分としてはＣｏＯ、ＣＯ3Ｏ4を
使用するのが好ましい。アルカリ金属元素Ｍ成分及びＮ
ａ成分を含む原料とコバルト成分を含む原料との混合比
は、コバルト２に対して元素Ｍ及びＮａを１．２〜１．
７の範囲で混合するのが好ましい。定比の１．０よりも
過剰にするのは、反応中にアルカリ金属成分が消失する
ためである。前述したアルカリ金属元素Ｍ成分を含む原
料とＮａ成分を含む原料は、いずれも吸湿性に富む化合
物である。したがって、混合前に１００℃以上で乾燥し
ておくことが好ましい。また、取り扱いも乾燥空気中で
行うのが好ましい。CoO and CO 3 O 4 are preferably used as the cobalt component. Alkali metal element M component and N
The mixing ratio of the raw material containing the a component and the raw material containing the cobalt component is 1.2 to 1.
Mixing in the range of 7 is preferred. Excessive stoichiometry of 1.0 is because the alkali metal component disappears during the reaction. The above-mentioned raw material containing the alkali metal element M component and the raw material containing the Na component are both highly hygroscopic compounds. Therefore, it is preferable to dry at 100 ° C. or higher before mixing. It is also preferable to handle in dry air.
【００２８】使用するフラックスには、アルカリ金属の
塩化物並びにフッ化物のいずれか、または両者を混合し
たものが好ましい。フラックス成分も吸湿性に富むた
め、１００℃以上で乾燥しておくことが好ましい。アル
カリ金属原料、コバルト原料及びフラックスを混合した
後、純度９５％以上のアルミナ坩堝に入れる。低純度の
坩堝は、坩堝中の焼結助剤成分がフラックスで腐食され
るため好ましくない。The flux to be used is preferably either a chloride of an alkali metal or a fluoride, or a mixture of both. Since the flux component is also highly hygroscopic, it is preferably dried at 100 ° C or higher. After mixing the alkali metal raw material, the cobalt raw material and the flux, the mixture is put into an alumina crucible having a purity of 95% or more. A low-purity crucible is not preferable because the sintering aid component in the crucible is corroded by the flux.
【００２９】原料としてアルカリ金属の炭酸塩を用いた
場合、Ｎａ0.5Ｍ0.5Ｃｏ2Ｏ4の生成反応は次式（３）で
表される。When an alkali metal carbonate is used as a raw material, the reaction for producing Na 0.5 M 0.5 Co 2 O 4 is represented by the following equation (3).
【００３０】
(1/2)Ｎａ2ＣＯ3＋(1/2)Ｍ2ＣＯ3＋(4/3)Ｃｏ3Ｏ4＋(5/6)Ｏ2→
２Ｎａ0.5Ｍ0.5Ｃｏ2Ｏ4＋ＣＯ2↑ …（３）
上記（３）式から明らかなように、Ｎａ0.5Ｍ0.5Ｃｏ2
Ｏ4の生成反応には酸素が必要である。従って、反応は
空気または酸素雰囲気中で行うことが好ましい。(1/2) Na 2 CO 3 + (1/2) M 2 CO 3 + (4/3) Co 3 O 4 + (5/6) O 2 → 2Na 0.5 M 0.5 Co 2 O 4 + CO 2 ↑ (3) As is clear from the above formula (3), Na 0.5 M 0.5 Co 2
Oxygen is required for the O 4 formation reaction. Therefore, the reaction is preferably performed in an air or oxygen atmosphere.
【００３１】反応は、少なくともフラックスの融点以上
で一定時間保持することが必須であり、融点より１００
〜３００℃高い温度で行うことが好ましい。この温度範
囲より低いと、ナトリウム成分及びコバルト成分がフラ
ックスに充分溶解しないため、反応が遅くて大きな単結
晶を得ることが困難になる恐れがある。一方、この温度
範囲より高くなると、ＮａαＭXＡYＯ4-Z結晶が分解を
始め、そのうえフラックス成分の分解消失が生じる。大
きな結晶を得るためには、保持の後に徐冷する事が必須
である。冷却速度は、フラックスの融点温度まで、２０
℃／分以下にすることが好ましい。融点温度以下では、
急冷しても問題はない。It is essential that the reaction is maintained at a temperature above the melting point of the flux for a certain period of time, and the reaction temperature is 100% above the melting point.
It is preferable to carry out at a temperature higher by ˜300 ° C. If the temperature is lower than this temperature range, the sodium component and the cobalt component are not sufficiently dissolved in the flux, so that the reaction is slow and it may be difficult to obtain a large single crystal. On the other hand, when the temperature is higher than this temperature range, the Na α M X A Y O 4-Z crystal starts to decompose, and the flux component is decomposed and disappears. In order to obtain large crystals, it is essential to slowly cool after holding. The cooling rate is 20 up to the melting point temperature of the flux.
C./minute or less is preferable. Below the melting temperature,
There is no problem with quenching.
【００３２】このような方法によると、坩堝内には１ｍ
ｍ以下の大きさを有する薄片状のＮａαＭXＡYＯ4-Z結
晶が成長する。ただし、坩堝内にはフラックス成分、未
反応のアルカリ金属成分及びコバルト成分が存在してい
る。このうち、フラックス成分及びアルカリ金属成分は
水に可溶であるため、水洗することで除去できる。また
コバルト成分は粒成長せず微粉のまま残るため、水洗し
た後残渣を乾燥し篩分する事により除去することができ
る。その結果、本発明の熱電変換材料を得ることができ
る。According to such a method, the inside of the crucible is 1 m.
Flake-shaped Na α M X A Y O 4-Z crystals having a size of m or less grow. However, a flux component, an unreacted alkali metal component and a cobalt component are present in the crucible. Of these, the flux component and the alkali metal component are soluble in water and can be removed by washing with water. Further, since the cobalt component does not grow grains and remains as fine powder, it can be removed by washing with water, drying the residue and sieving. As a result, the thermoelectric conversion material of the present invention can be obtained.
【００３３】以上説明した本発明に係る熱電変換材料
は、前述した化学式（１）で表わされる組成を有する。
このような熱電変換材料によれば、熱伝導率を低下させ
ることができるため、熱電変換効率を高くすることがで
きる。また、有害な元素を含有しないため、安全性を向
上することができると共に、製造コストを低くすること
ができる。本発明によると熱電変換効率が向上されるの
は、以下に説明する作用によるものと推測される。The thermoelectric conversion material according to the present invention described above has the composition represented by the above chemical formula (1).
With such a thermoelectric conversion material, the thermal conductivity can be reduced, and thus the thermoelectric conversion efficiency can be increased. Further, since no harmful element is contained, the safety can be improved and the manufacturing cost can be reduced. The reason why the thermoelectric conversion efficiency is improved according to the present invention is presumed to be due to the operation described below.
【００３４】すなわち、前述した元素組成式ＮａＣｏ2
Ｏ4-Yで表される物質は、前述した図６に示すような層
状の結晶構造を有する。このため、特性には結晶方向異
方性が存在する。具体的には、稜を共有するＣｏＯ6八
面体からなるＣｏＯ2シート２１の面内、つまりａ軸方
向には良好な導電性を示すのに対し、ｃ軸方向の導電性
が乏しい。よって、この物質を熱電変換素子として用い
る際、前述した図６に示すように、ａ軸方向に沿って温
度差を設けることが望ましい。ところが、導電性が高い
とき、熱伝導性も高くなるため、前述したＮａＣｏ2Ｏ
4-Yで表される物質にａ軸方向に沿って温度差を設ける
と、高い導電性が得られるものの、熱伝導率も高く、結
果として高い性能指数Ｚを得られなくなる。That is, the above-mentioned elemental composition formula NaCo 2
The substance represented by O 4-Y has a layered crystal structure as shown in FIG. For this reason, the crystal orientation anisotropy exists in the characteristics. Specifically, while good conductivity is exhibited in the plane of the CoO 2 sheet 21 composed of CoO 6 octahedrons sharing a ridge, that is, in the a-axis direction, conductivity in the c-axis direction is poor. Therefore, when using this substance as a thermoelectric conversion element, it is desirable to provide a temperature difference along the a-axis direction as shown in FIG. 6 described above. However, when the conductivity is high, the thermal conductivity is also high, and therefore the above-mentioned NaCo 2 O is used.
When a substance represented by 4-Y is provided with a temperature difference along the a-axis direction, high conductivity is obtained, but thermal conductivity is also high, and as a result, a high figure of merit Z cannot be obtained.
【００３５】本発明の前述した化学式（１）で表わされ
る熱電変換材料は、稜を共有するＡＯ6八面体からなる
ＡＯ2層がｃ軸方向に積層され、前記Ｎａ元素及び前記
Ｍ元素がＡＯ2層間に占有率（５０×（α＋Ｘ））％で
存在している結晶構造を有する。このような熱電変換材
料によると、ＡＯ2層の厚さがフォノンの平均自由行程
よりも薄く、またＡＯ2層間に存在するＮａイオンによ
ってフォノンを散乱させることができる他に、特定のモ
ル比で含有されたＫ、Ｒｂ及びＣｓよりなる群から選ば
れる１種類以上のアルカリ金属元素Ｍによりフォノンを
散乱させることができる。アルカリ金属元素Ｍは、Ｎａ
よりもイオン半径が大きいため、Ｎａに比べて大きなフ
ォノン散乱効果を得ることができる。その結果、熱伝導
性を低下させることができるため、性能指数Ｚの大きな
熱電変換材料を実現することができる。In the thermoelectric conversion material represented by the above chemical formula (1) of the present invention, an AO 2 layer composed of AO 6 octahedra sharing a ridge is laminated in the c-axis direction, and the Na element and the M element are AO. It has a crystal structure that exists between two layers at an occupancy rate (50 × (α + X))%. According to such a thermoelectric conversion material, the thickness of the AO 2 layer is smaller than the mean free path of the phonons, and the phonons can be scattered by the Na ions existing between the AO 2 layers. Phonons can be scattered by the contained one or more kinds of alkali metal elements M selected from the group consisting of K, Rb and Cs. The alkali metal element M is Na
Since the ionic radius is larger than that of Na, a larger phonon scattering effect can be obtained as compared with Na. As a result, since the thermal conductivity can be reduced, a thermoelectric conversion material having a large figure of merit Z can be realized.
【００３６】次いで、本発明に係る熱電変換素子につい
て説明する。Next, the thermoelectric conversion element according to the present invention will be described.
【００３７】＜熱電変換素子＞この熱電変換素子は、ｐ
型の熱電変換材料の本体と、ｎ型の熱電変換材料の本体
と、これら本体に接続され、電力を取り出すための電極
対とを具備する。前記ｐ型の熱電変換材料として本発明
に係る熱電変換材料が使用される。<Thermoelectric conversion element> This thermoelectric conversion element has p
A thermoelectric conversion material main body, an n-type thermoelectric conversion material main body, and an electrode pair connected to these main bodies for extracting electric power. The thermoelectric conversion material according to the present invention is used as the p-type thermoelectric conversion material.
【００３８】例えば前述したフラックス法により本発明
に係る熱電変換材料を製造すると、結晶粒界が存在しな
い単結晶を得ることができる。この単結晶は、抵抗率が
低く、ｃ軸方向の向きが厚さ方向と平行で、かつ厚さが
１ｍｍ以下の薄片形状を有する。よって、この熱電変換
材料は、厚さ方向に垂直なａ、ｂ軸方向の熱電変換特性
に優れている。このような熱電変換材料を用いて熱電変
換素子を作製する場合、熱電変換材料をｃ軸が実質的に
同一の向きに配向するように複数個積層して集合体を形
成することが好ましい。この熱電変換材料集合体は、例
えば、以下に説明する方法で得られる。For example, when the thermoelectric conversion material according to the present invention is manufactured by the above-mentioned flux method, a single crystal having no crystal grain boundary can be obtained. This single crystal has a low resistivity, the c-axis direction is parallel to the thickness direction, and has a thin piece shape with a thickness of 1 mm or less. Therefore, this thermoelectric conversion material has excellent thermoelectric conversion characteristics in the a and b axis directions perpendicular to the thickness direction. When a thermoelectric conversion element is manufactured using such a thermoelectric conversion material, it is preferable to stack a plurality of thermoelectric conversion materials so that the c-axes are oriented in substantially the same direction to form an aggregate. This thermoelectric conversion material aggregate is obtained, for example, by the method described below.
【００３９】まず、複数個の単結晶を金型に入れ成形す
る。圧力は１００ＭＰａ以上であることが好ましい。ま
た、より配向性を向上させるためには、金型内に単結晶
を並べてから成形すると良い。First, a plurality of single crystals are put into a mold and molded. The pressure is preferably 100 MPa or more. Further, in order to further improve the orientation, it is advisable to arrange the single crystals in a mold and then form the crystals.
【００４０】次いで、得られた成形体を六方晶窒化ほう
素製モールドに入れ、加圧焼結を行う。焼成雰囲気は空
気、または酸素中であることが好ましい。Next, the obtained compact is put into a hexagonal boron nitride mold and pressure-sintered. The firing atmosphere is preferably air or oxygen.
【００４１】加圧焼結は７００〜１０００℃の温度範囲
で行うことが好ましい。加圧焼結温度を７００℃未満に
すると、充分に緻密化しなくなる恐れがある。一方、加
圧焼結温度が１０００℃を超えると、前記成形体が融解
する恐れがある。また、六方晶窒化ほう素製モールドが
酸化性雰囲気中で酸化される恐れがある。加圧は１０Ｍ
Ｐａ以上であることが好ましい。加圧を１０ＭＰａ未満
にすると、十分に緻密化した積層焼結体を得ることが困
難になる恐れがある。The pressure sintering is preferably performed in the temperature range of 700 to 1000 ° C. If the pressure sintering temperature is less than 700 ° C., there is a possibility that densification will not be sufficient. On the other hand, if the pressure sintering temperature exceeds 1000 ° C., the molded body may melt. Further, the hexagonal boron nitride mold may be oxidized in an oxidizing atmosphere. Pressurization is 10M
It is preferably Pa or more. If the pressure is less than 10 MPa, it may be difficult to obtain a sufficiently densified laminated sintered body.
【００４２】このようにして作製された結晶配向積層焼
結体は、結晶方位がそろっているため、積層方向並びに
平行方向の導電率とゼーベック係数を大きくすることが
できると共に、熱伝導率を小さくすることができる。そ
の結果、優れた熱電特性を発揮することができる。Since the crystallographically-oriented laminated sinter thus produced has the same crystal orientation, it is possible to increase the electric conductivity and Seebeck coefficient in the laminating direction and the parallel direction and to reduce the thermal conductivity. can do. As a result, excellent thermoelectric properties can be exhibited.
【００４３】得られた焼結体は、所望の寸法に切断後、
熱電変換素子に組み込まれる。The obtained sintered body was cut into desired dimensions,
It is incorporated into a thermoelectric conversion element.
【００４４】本発明に係る熱電変換素子の一態様を図２
に示す。FIG. 2 shows one embodiment of the thermoelectric conversion element according to the present invention.
Shown in.
【００４５】ｐ型半導体である本発明に係る熱電変換材
料から形成された熱電変換材料集合体６（ｐ型の熱電変
換材料の本体)と、ｎ型半導体の熱電変換材料７（ｎ型
の熱電変換材料の本体)は、並列に置かれ、終端電極
８1、終端電極８2及び共通電極８3で直列に接続されて
いる。共通電極８3の外側には下部絶縁性基板９1が接合
されている。一方、終端電極８1と終端電極８2の外側に
は上部絶縁性基板９2が接合されている。A thermoelectric conversion material assembly 6 (main body of p-type thermoelectric conversion material) formed of the thermoelectric conversion material according to the present invention which is a p-type semiconductor, and a thermoelectric conversion material 7 (n-type thermoelectric conversion material) of n-type semiconductor. The bodies of conversion material) are placed in parallel and are connected in series by the termination electrode 8 1 , the termination electrode 8 2 and the common electrode 8 3 . A lower insulating substrate 9 1 is joined to the outside of the common electrode 8 3 . On the other hand, an upper insulating substrate 9 2 is joined to the outside of the termination electrodes 8 1 and 8 2 .
【００４６】上部絶縁性基板９2を低温度（Ｌ）にし、
かつ下部絶縁性基板９1を高温度（Ｈ）にして上下絶縁
性基板９1、９2に温度差を与えると、ｐ型半導体である
熱電変換材料集合体６においては、正の電荷を持ったホ
ール１０が低温度Ｌ側に、ｎ型半導体である熱電変換材
料７においては、負の電荷を持った電子１１が低温度側
Ｌに移動する。その結果、終端電極８1と終端電極８2の
間に電位差が生じる。図２のように温度差を与えた場
合、終端電極８1は正、終端電極８2は負となる。なお、
より高い電圧を得るためには、図３に示すように、ｐ型
熱電変換材料集合体６とｎ型熱電変換材料７を交互に直
列に接続すると良い。[0046] the upper insulating substrate 9 2 at a low temperature (L),
Moreover, when the lower insulating substrate 9 1 is set to a high temperature (H) and a temperature difference is given to the upper and lower insulating substrates 9 1 and 9 2 , the thermoelectric conversion material assembly 6 which is a p-type semiconductor has a positive charge. In the thermoelectric conversion material 7 which is an n-type semiconductor, the holes 10 move to the low temperature side L, and the electrons 11 having a negative charge move to the low temperature side L. As a result, a potential difference is generated between the terminal electrode 8 1 and the terminal electrode 8 2 . When a temperature difference is applied as shown in FIG. 2, the terminal electrode 8 1 becomes positive and the terminal electrode 8 2 becomes negative. In addition,
In order to obtain a higher voltage, it is preferable to alternately connect the p-type thermoelectric conversion material assembly 6 and the n-type thermoelectric conversion material 7 in series as shown in FIG.
【００４７】以上説明した本発明に係る熱電変換素子に
よれば、前述した化学式（1）で表わされる熱電変換材
料の本体と、前記本体に接続され、電力を取り出すため
の電極対とを備えるため、高い電圧を得ることができ
る。According to the thermoelectric conversion element of the present invention described above, the thermoelectric conversion material main body represented by the chemical formula (1) described above and the electrode pair connected to the main body for extracting electric power are provided. , High voltage can be obtained.
【００４８】＜熱電池＞本発明に係る熱電池は、ｐ型の
熱電変換材料の本体と、ｎ型の熱電変換材料の本体と、
これら本体に接続され、電力を取り出すための電極対と
を有する熱電変換素子を具備する。前記ｐ型の熱電変換
材料として本発明に係る熱電変換材料が使用される。<Thermal Battery> The thermal battery according to the present invention comprises a main body of p-type thermoelectric conversion material, a main body of n-type thermoelectric conversion material, and
It comprises a thermoelectric conversion element connected to these main bodies and having an electrode pair for extracting electric power. The thermoelectric conversion material according to the present invention is used as the p-type thermoelectric conversion material.
【００４９】本発明に係る熱電池の一態様を図４に示
す。但し、前述した図２及び図３で説明したのと同様な
部材に関しては、この図２及び図３と同様な符号を付し
て説明を省略する。熱電変換素子１２の上部絶縁性基板
９2を低温度にし、かつ下部絶縁性基板９1を高温度にす
ると、熱電変換素子１２の終端電極８1と終端電極８2間
に電位差が生じる。終端電極８1と終端電極８2に負荷１
３を接続すると、電流Ｉが流れ、熱電池となる。An embodiment of the thermal battery according to the present invention is shown in FIG. However, the same members as those described in FIGS. 2 and 3 described above are denoted by the same reference numerals as those in FIGS. 2 and 3, and description thereof is omitted. When the upper insulating substrate 9 2 of the thermoelectric conversion element 12 is made to have a low temperature and the lower insulating substrate 9 1 is made to have a high temperature, a potential difference is generated between the terminal electrode 8 1 and the terminal electrode 8 2 of the thermoelectric conversion element 12. Load 1 on terminal electrode 8 1 and terminal electrode 8 2
When 3 is connected, the electric current I flows and it becomes a thermal battery.
【００５０】以上説明した本発明に係る熱電池によれ
ば、前述した化学式（1）で表わされる熱電変換材料の
本体と、前記本体に接続され、電力を取り出すための電
極対とを有する熱電変換素子を備えるため、大きな電流
を得ることができる。According to the thermal battery of the present invention described above, the thermoelectric conversion having the main body of the thermoelectric conversion material represented by the chemical formula (1) described above and the electrode pair connected to the main body for taking out electric power. Since the device is provided, a large current can be obtained.
【００５１】＜冷却器＞本発明に係る冷却器は、ｐ型の
熱電変換材料の本体と、ｎ型の熱電変換材料の本体と、
これら本体に接続され、電力を印加するための電極対と
を有する熱電変換素子を具備する。前記ｐ型の熱電変換
材料として本発明に係る熱電変換材料が使用される。<Cooler> A cooler according to the present invention comprises a body of p-type thermoelectric conversion material, a body of n-type thermoelectric conversion material, and
It comprises a thermoelectric conversion element connected to these main bodies and having an electrode pair for applying electric power. The thermoelectric conversion material according to the present invention is used as the p-type thermoelectric conversion material.
【００５２】本発明に係る冷却器の一態様を図５に示
す。但し、前述した図２〜図４で説明したのと同様な部
材に関しては、この図２〜図４と同様な符号を付して説
明を省略する。熱電変換素子１２の終端電極８1と終端
電極８2間に直流電源１４を用いて直流電流Ｃを流す。
その結果、熱電変換素子１２の上部絶縁性基板９2側は
高温に、下部絶縁性基板９1側は低温になる。これによ
り、冷却器になる。An embodiment of the cooler according to the present invention is shown in FIG. However, the same members as those described in FIGS. 2 to 4 described above are denoted by the same reference numerals as those in FIGS. 2 to 4, and description thereof will be omitted. A direct current C is passed between the terminal electrode 8 1 and the terminal electrode 8 2 of the thermoelectric conversion element 12 by using the DC power supply 14.
As a result, the upper insulating substrate 9 2 side of the thermoelectric conversion element 12 has a high temperature, and the lower insulating substrate 9 1 side has a low temperature. This becomes a cooler.
【００５３】以上説明した本発明に係る冷却器によれ
ば、前述した化学式（1）で表わされる熱電変換材料の
本体と、前記本体に接続され、電力を印加するための電
極対とを有する熱電変換素子を備えるため、高い冷却効
率が得られる。According to the cooler of the present invention described above, a thermoelectric device having a main body of the thermoelectric conversion material represented by the above chemical formula (1) and an electrode pair connected to the main body for applying electric power. Since the conversion element is provided, high cooling efficiency can be obtained.
【００５４】[0054]
【実施例】以下、本発明の好ましい実施例を詳細に説明
する。The preferred embodiments of the present invention will be described in detail below.
【００５５】（実施例１）熱電変換材料
原料粉として、Ｎａ2ＣＯ3、Ｋ2ＣＯ3及びＣｏ3Ｏ4を使
用した。これらをモル比Ｎａ：Ｋ：Ｃｏが１：１：３に
なるように混合した。この混合物にフラックスとしてＮ
ａＣｌをモル比（Ｋ2ＣＯ3＋Ｎａ2ＣＯ3）：ＮａＣｌが
１：５になるように混合し、これを純度９９％以上のア
ルミナ坩堝に入れた。後の熱処理中におけるＮａＣ１フ
ラックスの蒸発を防ぐため、坩堝には純度９９％以上の
アルミナ製の蓋をした。Example 1 As raw material powders for thermoelectric conversion materials, Na 2 CO 3 , K 2 CO 3 and Co 3 O 4 were used. These were mixed so that the molar ratio Na: K: Co was 1: 1: 3. N as a flux in this mixture
aCl was mixed so that the molar ratio (K 2 CO 3 + Na 2 CO 3 ): NaCl was 1: 5, and the mixture was placed in an alumina crucible having a purity of 99% or more. In order to prevent evaporation of the NaC1 flux during the subsequent heat treatment, the crucible was covered with an alumina lid having a purity of 99% or more.
【００５６】この坩堝を電気炉に入れ、炉内に酸素ガス
を流した。１０５０℃まで１００℃／時間で昇温し、１
０５０℃で２０時間保持、その後、８５０℃まで２℃／
時間で温度を下げ、さらに室温まで炉内で冷却させた。
坩堝から内容物を出し、ＮａＣ１、未反応のＫ2ＣＯ3、
Ｎａ2ＣＯ3を水洗処理して除去した。残渣を１２０℃で
乾燥させた後、目開き０．５ｍｍの篩で篩分し、平均径
が約５ｍｍで、平均厚さが２０μｍ程度のＮａ0.5Ｋ0.5
ＣＯ2Ｏ4結晶を得た。This crucible was placed in an electric furnace and oxygen gas was flown into the furnace. Increase the temperature to 1050 ° C at 100 ° C / hour, and
Hold at 050 ° C for 20 hours, then 2 ° C / 850 ° C
The temperature was lowered with time, and further cooled to room temperature in the furnace.
Remove the contents from the crucible, and remove NaC1, unreacted K 2 CO 3 ,
Na 2 CO 3 was removed by washing with water. The residue is dried at 120 ° C. and then sieved with a sieve having a mesh size of 0.5 mm to obtain Na 0.5 K 0.5 having an average diameter of about 5 mm and an average thickness of about 20 μm.
CO 2 O 4 crystals were obtained.
【００５７】得られた単結晶を以下の方法で評価した。The obtained single crystal was evaluated by the following methods.
【００５８】（１）導電率
単結晶を４×４×０．０２ｍｍに切断した後、４角に電
極を形成し、ファンデアポア法により測定した。(1) Conductivity A single crystal was cut into a size of 4 × 4 × 0.02 mm, electrodes were formed in the four corners, and measurement was performed by the Van der Pore method.
【００５９】（２）ゼーベック係数
単結晶を４×１×０．０２ｍｍに切断し、この両端に温
度差を付け起電力を測定し、ゼーベック係数を求めた。(2) Seebeck coefficient The single crystal was cut into 4 × 1 × 0.02 mm, a temperature difference was applied to both ends of the single crystal, and the electromotive force was measured to obtain the Seebeck coefficient.
【００６０】（３）熱伝導率
光交流法により熱拡散率を測定した。これとは別にＤＳ
Ｃ測定により比熱を求めた。これらより熱伝導率を求め
た。(3) Thermal conductivity The thermal diffusivity was measured by the photo-acoustic method. Apart from this, DS
Specific heat was determined by C measurement. The thermal conductivity was determined from these.
【００６１】以上の評価を行った結果、得られた熱電変
換材料は、抵抗率が２．３×１０-4Ωｃｍで、ゼーベッ
ク係数が１００μＶ／Ｋで、熱伝導率が２．０Ｗ／ｍＫ
であった。以上の値より性能指数Ｚは２．２×１０-3で
あった。As a result of the above evaluation, the thermoelectric conversion material obtained had a resistivity of 2.3 × 10 −4 Ωcm, a Seebeck coefficient of 100 μV / K, and a thermal conductivity of 2.0 W / mK.
Met. From the above values, the figure of merit Z was 2.2 × 10 −3 .
【００６２】（実施例２〜１２）熱電変換材料
アルカリ金属の組成を下記表1に示すように変更するこ
と以外は、前述した実施例1と同様にして熱電変換材料
を作製した。得られた熱電変換材料について、前述した
のと同様にして導電率、ゼーベック係数および熱伝導率
を測定し、これらから性能指数Ｚを算出した。これらの
結果を下記表1に示す。(Examples 2 to 12) Thermoelectric conversion materials Thermoelectric conversion materials were prepared in the same manner as in Example 1 except that the composition of the alkali metal was changed as shown in Table 1 below. Regarding the obtained thermoelectric conversion material, the electrical conductivity, Seebeck coefficient and thermal conductivity were measured in the same manner as described above, and the figure of merit Z was calculated from these. The results are shown in Table 1 below.
【００６３】得られた実施例１〜１２の熱電変換材料に
ついて、透過型電子顕微鏡を用いて格子像を観察し、ま
た電子線回折パターンを解析した結果、各材料は、稜を
共有するＣｏＯ6八面体からなるＣｏＯ2層がｃ軸方向に
積層され、かつＮａ元素及びＭ元素がＣｏＯ2層間に占
有率５０％で存在している結晶構造を有していた。Regarding the obtained thermoelectric conversion materials of Examples 1 to 12, a lattice image was observed using a transmission electron microscope and an electron beam diffraction pattern was analyzed. As a result, each material had CoO 6 sharing a ridge. It had a crystal structure in which CoO 2 layers composed of octahedra were laminated in the c-axis direction, and Na element and M element were present between the CoO 2 layers at an occupation rate of 50%.
【００６４】（比較例１）熱電変換材料
原料粉として、Ｎａ2ＣＯ3及びＣｏ3Ｏ4を使用した。こ
れらをモル比Ｎａ：Ｃｏが２：３になるように混合し
た。この混合物にフラックスになるＮａＣｌをモル比Ｎ
ａ2ＣＯ3：ＮａＣｌが１：５になるように混合し、これ
を純度９９％以上のアルミナ坩堝に入れた。後の熱処理
中におけるＮａＣ１フラックスの蒸発を防ぐため、坩堝
には純度９９％以上のアルミナ製の蓋をした。Comparative Example 1 Na 2 CO 3 and Co 3 O 4 were used as the raw material powder for thermoelectric conversion material. These were mixed so that the molar ratio Na: Co was 2: 3. NaCl as a flux is added to this mixture in a molar ratio N
a 2 CO 3 : NaCl was mixed at a ratio of 1: 5, and the mixture was put into an alumina crucible having a purity of 99% or more. In order to prevent evaporation of the NaC1 flux during the subsequent heat treatment, the crucible was covered with an alumina lid having a purity of 99% or more.
【００６５】この坩堝を電気炉に入れ、炉内に酸素ガス
を流した。１０５０℃まで１００℃／時間で昇温し、１
０５０℃で２０時間保持、その後、８５０℃まで２℃／
時間で温度を下げ、さらに室温まで炉内で冷却させた。
坦堀から内容物を出し、ＮａＣｌ、未反応のＮａ2ＣＯ3
を水洗処理して除去した。残渣を１２０℃で乾燥させた
後、目開き０．５ｍｍの篩で篩分し、平均径が約５ｍ
ｍ、平均厚さが２０μｍ程度のＮａＣｏ2Ｏ4結晶を得
た。This crucible was placed in an electric furnace, and oxygen gas was flown into the furnace. Increase the temperature to 1050 ° C at 100 ° C / hour, and
Hold at 050 ° C for 20 hours, then 2 ° C / 850 ° C
The temperature was lowered with time, and further cooled to room temperature in the furnace.
The contents are taken out from the carrier moat, NaCl, unreacted Na 2 CO 3
Was removed by washing with water. After drying the residue at 120 ° C, it is sieved with a sieve having an opening of 0.5 mm and the average diameter is about 5 m.
m, and an average thickness of about 20 μm was obtained as a NaCo 2 O 4 crystal.
【００６６】前述したのと同様にして焼結体の評価を行
った。その結果、抵抗率が１．８×１０-4Ωｃｍで、ゼ
ーベック係数が９０μＶ／Ｋで、熱伝導率が１０Ｗ／ｍ
Ｋであった。以上の値より性能指数Ｚは０．４５×１０
-3であった。熱伝導率が実施例１に比較して大きいた
め、性能指数Ｚは実施例１の約１／４と小さくなった。The sintered body was evaluated in the same manner as described above. As a result, the resistivity was 1.8 × 10 −4 Ωcm, the Seebeck coefficient was 90 μV / K, and the thermal conductivity was 10 W / m.
It was K. From the above values, the figure of merit Z is 0.45 × 10
It was -3 . Since the thermal conductivity was higher than that in Example 1, the figure of merit Z was as small as about 1/4 of Example 1.
【００６７】[0067]
【表１】 [Table 1]
【００６８】表1から明らかなように、前述した化学式
（１）で表わされる組成を有する実施例１〜１２の熱電
変換材料は、組成がＮａＣｏ2Ｏ4で表わされる比較例の
熱電変換材料に比べて、熱伝導率が低く、性能指数Ｚが
大きいことがわかる。As is apparent from Table 1, the thermoelectric conversion materials of Examples 1 to 12 having the composition represented by the chemical formula (1) described above are the thermoelectric conversion materials of the comparative examples represented by the composition of NaCo 2 O 4. In comparison, it can be seen that the thermal conductivity is low and the figure of merit Z is large.
【００６９】（実施例１３）熱電変換素子
実施例１の熱電変換材料（単結晶）０．３５ｇを直径１
０ｍｍの金型に入れ、圧力１００ＭＰａで成形した。得
られた成形体を内径１０ｍｍの六方晶窒化ほう素製モー
ルドに入れ、圧力２０ＭＰａ、温度８５０℃、空気雰囲
気中で加圧焼結を行うことで、直径１０ｍｍ、厚さ１ｍ
ｍの結晶配向積層焼結体を得た。この焼結体を切断して
１×１×１ｍｍとし、ｐ型の熱電変換材料集合体を得
た。(Example 13) Thermoelectric conversion element 0.35 g of the thermoelectric conversion material (single crystal) of Example 1 was used for a diameter of 1
It was placed in a 0 mm mold and molded at a pressure of 100 MPa. The obtained compact is put into a hexagonal boron nitride mold having an inner diameter of 10 mm, and pressure sintering is performed in an air atmosphere at a pressure of 20 MPa and a temperature of 850 ° C. to obtain a diameter of 10 mm and a thickness of 1 m.
A crystallographically-oriented laminated sintered body of m was obtained. This sintered body was cut into 1 × 1 × 1 mm to obtain a p-type thermoelectric conversion material aggregate.
【００７０】一方、ｎ型としてＢｉＴｅ系熱電変換材料
（サイズが１×１×１ｍｍ）を用意した。On the other hand, a BiTe-based thermoelectric conversion material (size: 1 × 1 × 1 mm) was prepared as an n-type.
【００７１】次いで、前記ｐ型半導体熱電変換材料から
作製されたｐ型ピース３２個と、前記ｎ型半導体熱電変
換材料から作製されたｎ型ピース３２個を並列に置き、
電極で直列に接続させた。さらに、この電極の外側に、
高純度窒化アルミニウム焼結体からなる絶縁性基板（１
７×１７×０．３ｍｍ）を接合した。直列に接続した熱
電変換材料の終端に電極リード線をつけ、前述した図３
に示す構成を有する熱電変換素子を作製した。Next, 32 p-type pieces made of the p-type semiconductor thermoelectric conversion material and 32 n-type pieces made of the n-type semiconductor thermoelectric conversion material are placed in parallel,
The electrodes were connected in series. Furthermore, on the outside of this electrode,
Insulating substrate made of high-purity aluminum nitride sintered body (1
7 × 17 × 0.3 mm) were joined. The electrode lead wire is attached to the end of the thermoelectric conversion material connected in series, and the
A thermoelectric conversion element having the structure shown in was produced.
【００７２】得られた熱電変換素子は、温度差１℃あた
り１００μＶの電圧を発生させることができた。The obtained thermoelectric conversion element was able to generate a voltage of 100 μV per 1 ° C. of temperature difference.
【００７３】（実施例１４）熱電池
実施例１３の熱電変換素子の片側にアルミニウム製放熱
フィンを設け、熱電池を製造した。この熱電池における
放熱フィンを接合した反対側を廃熱源（例えば、自動車
の廃棄ガスパイプ）に接合させることによって、直流電
流及び電力が得られた。また、冷却手段として放熱フィ
ンの代わりに、冷却水循環パイプを設けて水冷しても熱
電池として有効に作動できることを確認した。(Example 14) Thermal Battery A thermal battery was manufactured by disposing an aluminum radiation fin on one side of the thermoelectric conversion element of Example 13. Direct current and electric power were obtained by joining the side opposite to the joining of the radiation fins in this thermal battery to a waste heat source (for example, a waste gas pipe of an automobile). Further, it was confirmed that a cooling water circulation pipe was provided as a cooling means instead of the heat radiation fins, and that the thermal battery could operate effectively even if water cooling was performed.
【００７４】（実施例１５）冷却器
実施例１３の熱電変換素子に電動ファンを接合した。熱
電変換素子に直流電源を接続し、電力を印加した。その
結果、ファンを設けた側は冷却され、冷気が発生し、冷
却器として機能したことを確認した。(Example 15) Cooler An electric fan was joined to the thermoelectric conversion element of Example 13. A direct current power supply was connected to the thermoelectric conversion element and electric power was applied. As a result, it was confirmed that the side provided with the fan was cooled, cool air was generated, and it functioned as a cooler.
【００７５】[0075]
【発明の効果】以上詳述したように本発明によれば、強
い毒性を有する元素を含有せず、安全性が高く、安価
で、かつ熱伝導率が低く、熱電変換効率が高い熱電変換
材料を提供することができる。また、本発明によれば、
熱電変換特性に優れた熱電変換素子、熱電池及び冷却器
を提供することができる。As described in detail above, according to the present invention, a thermoelectric conversion material that does not contain an element having strong toxicity, is highly safe, is inexpensive, has low thermal conductivity, and has high thermoelectric conversion efficiency. Can be provided. Further, according to the present invention,
A thermoelectric conversion element, a thermal battery, and a cooler having excellent thermoelectric conversion characteristics can be provided.
【図１】本発明に係る熱電変換材料の結晶構造を説明す
るための模式図。FIG. 1 is a schematic diagram for explaining a crystal structure of a thermoelectric conversion material according to the present invention.
【図２】本発明に係る熱電変換素子の一例を示す模式
図。FIG. 2 is a schematic diagram showing an example of a thermoelectric conversion element according to the present invention.
【図３】本発明に係る熱電変換素子の別な例を示す模式
図。FIG. 3 is a schematic view showing another example of the thermoelectric conversion element according to the present invention.
【図４】本発明に係る熱電池の一例を示す模式図。FIG. 4 is a schematic diagram showing an example of a thermal battery according to the present invention.
【図５】本発明に係る冷却器の一例を示す模式図。FIG. 5 is a schematic view showing an example of a cooler according to the present invention.
【図６】組成がＮａＣｏ2Ｏ4-Yで表わされる熱電変換材
料の結晶構造を示す模式図。FIG. 6 is a schematic diagram showing a crystal structure of a thermoelectric conversion material whose composition is represented by NaCo 2 O 4-Y .
１…ＣｏＯ2層、 ２…Ｃｏ原子、 ３…Ｏ原子、 ４…アルカリ金属Ｍのイオン、 ５…Ｎａイオン。1 ... CoO 2 layer, 2 ... Co atom, 3 ... O atom, 4 ... Alkali metal M ion, 5 ... Na ion.
───────────────────────────────────────────────────── フロントページの続き (72)発明者 立部 哲也 神奈川県川崎市幸区小向東芝町１番地 株式会社東芝研究開発センター内 (58)調査した分野(Int.Cl.7，ＤＢ名) H01L 35/22 H01L 35/16 H01L 35/32 H01L 35/34 H02N 11/00 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Tetsuya Tatebe 1 Komukai Toshiba Town, Komukai-shi, Kawasaki City, Kanagawa Prefecture Toshiba Research & Development Center Co., Ltd. (58) Fields investigated (Int.Cl. 7 , DB name) H01L 35/22 H01L 35/16 H01L 35/32 H01L 35/34 H02N 11/00
Claims (5)
することを特徴とする熱電変換材料。 ＮａαＭXＡYＯ4-Z …（１） 但し、前記Ｍは、Ｋ、Ｒｂ及びＣｓよりなる群から選ば
れる１種類以上のアルカリ金属元素からなり、前記Ａ
は、Ｃｏ、Ｆｅ、ＮｉおよびＣｕよりなる群から選ばれ
る１種類以上の元素からなり、モル比α、Ｘ、Ｙ及びＺ
は、０＜α＜１．２、０．１≦Ｘ≦１、０．７≦α＋Ｘ
≦１．２、０＜Ｙ、０≦Ｚを示す。1. A thermoelectric conversion material having a composition represented by the following chemical formula (1). Na α M X A Y O 4-Z (1) wherein M is one or more kinds of alkali metal elements selected from the group consisting of K, Rb and Cs, and A
Is composed of one or more elements selected from the group consisting of Co, Fe, Ni and Cu, and has a molar ratio α, X, Y and Z.
Is 0 <α <1.2, 0.1 ≦ X ≦ 1, 0.7 ≦ α + X
≦ 1.2, 0 <Y, and 0 ≦ Z are shown.
層がｃ軸方向に積層され、前記Ｎａ元素及び前記Ｍ元素
がＡＯ2層間に占有率（５０×（α＋Ｘ））％で存在し
ている結晶構造を有することを特徴とする請求項１記載
の熱電変換材料。2. AO 2 comprising an AO 6 octahedron sharing a ridge
2. The layer structure according to claim 1, wherein the layers are stacked in the c-axis direction, and the Na element and the M element have a crystal structure in which the occupancy rate (50 × (α + X))% exists between the AO 2 layers. Thermoelectric conversion material.
する熱電変換材料の本体と、前記本体に接続され、電力
を取り出すための電極対とを含むことを特徴とする熱電
変換素子。 ＮａαＭXＡYＯ4-Z …（１） 但し、前記Ｍは、Ｋ、Ｒｂ及びＣｓよりなる群から選ば
れる１種類以上のアルカリ金属元素からなり、前記Ａ
は、Ｃｏ、Ｆｅ、ＮｉおよびＣｕよりなる群から選ばれ
る１種類以上の元素からなり、モル比α、Ｘ、Ｙ及びＺ
は、０＜α＜１．２、０．１≦Ｘ≦１、０．７≦α＋Ｘ
≦１．２、０＜Ｙ、０≦Ｚを示す。3. A thermoelectric conversion element comprising a main body of a thermoelectric conversion material having a composition represented by the chemical formula (1) below, and an electrode pair connected to the main body for taking out electric power. Na α M X A Y O 4-Z (1) wherein M is one or more kinds of alkali metal elements selected from the group consisting of K, Rb and Cs, and A
Is composed of one or more elements selected from the group consisting of Co, Fe, Ni and Cu, and has a molar ratio α, X, Y and Z.
Is 0 <α <1.2, 0.1 ≦ X ≦ 1, 0.7 ≦ α + X
≦ 1.2, 0 <Y, and 0 ≦ Z are shown.
する熱電変換材料の本体と、前記本体に接続され、電力
を取り出すための電極対とを含む熱電変換素子を具備し
たことを特徴とする熱電池。 ＮａαＭXＡYＯ4-Z …（１） 但し、前記Ｍは、Ｋ、Ｒｂ及びＣｓよりなる群から選ば
れる１種類以上のアルカリ金属元素からなり、前記Ａ
は、Ｃｏ、Ｆｅ、ＮｉおよびＣｕよりなる群から選ばれ
る１種類以上の元素からなり、モル比α、Ｘ、Ｙ及びＺ
は、０＜α＜１．２、０．１≦Ｘ≦１、０．７≦α＋Ｘ
≦１．２、０＜Ｙ、０≦Ｚを示す。4. A thermoelectric conversion element comprising a main body of a thermoelectric conversion material having a composition represented by the following chemical formula (1), and an electrode pair connected to the main body for extracting electric power. And thermal battery. Na α M X A Y O 4-Z (1) wherein M is one or more kinds of alkali metal elements selected from the group consisting of K, Rb and Cs, and A
Is composed of one or more elements selected from the group consisting of Co, Fe, Ni and Cu, and has a molar ratio α, X, Y and Z.
Is 0 <α <1.2, 0.1 ≦ X ≦ 1, 0.7 ≦ α + X
≦ 1.2, 0 <Y, and 0 ≦ Z are shown.
する熱電変換材料の本体と、前記本体に接続され、電力
を印加するための電極対とを含む熱電変換素子を具備し
たことを特徴とする冷却器。 ＮａαＭXＡYＯ4-Z …（１） 但し、前記Ｍは、Ｋ、Ｒｂ及びＣｓよりなる群から選ば
れる１種類以上のアルカリ金属元素からなり、前記Ａ
は、Ｃｏ、Ｆｅ、ＮｉおよびＣｕよりなる群から選ばれ
る１種類以上の元素からなり、モル比α、Ｘ、Ｙ及びＺ
は、０＜α＜１．２、０．１≦Ｘ≦１、０．７≦α＋Ｘ
≦１．２、０＜Ｙ、０≦Ｚを示す。5. A thermoelectric conversion element comprising a main body of a thermoelectric conversion material having a composition represented by the following chemical formula (1), and an electrode pair connected to the main body for applying electric power. Characteristic cooler. Na α M X A Y O 4-Z (1) wherein M is one or more kinds of alkali metal elements selected from the group consisting of K, Rb and Cs, and A
Is composed of one or more elements selected from the group consisting of Co, Fe, Ni and Cu, and has a molar ratio α, X, Y and Z.
Is 0 <α <1.2, 0.1 ≦ X ≦ 1, 0.7 ≦ α + X
≦ 1.2, 0 <Y, and 0 ≦ Z are shown.
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| JP2000095176A JP3515478B2 (en) | 2000-03-30 | 2000-03-30 | Thermoelectric conversion material, thermoelectric conversion element, thermal battery and cooler |
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| JP2000095176A JP3515478B2 (en) | 2000-03-30 | 2000-03-30 | Thermoelectric conversion material, thermoelectric conversion element, thermal battery and cooler |
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| Publication Number | Publication Date |
|---|---|
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| JP3515478B2 true JP3515478B2 (en) | 2004-04-05 |
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| AU2003227243A1 (en) * | 2002-04-09 | 2003-10-20 | Matsushita Electric Industrial Co., Ltd. | Thermo-electric conversion material and method for preparation thereof |
| JP3874365B2 (en) | 2004-03-01 | 2007-01-31 | 松下電器産業株式会社 | Thermoelectric conversion device, cooling method and power generation method using the same |
| WO2007020775A1 (en) * | 2005-08-16 | 2007-02-22 | Matsushita Electric Industrial Co., Ltd. | Thermoelectric conversion device and cooling method and power generating method using same |
| JP5176610B2 (en) * | 2008-03-10 | 2013-04-03 | パナソニック株式会社 | Thermoelectric device element |
| CN102540099B (en) * | 2012-02-06 | 2014-05-07 | 天津大学 | System and method for testing thermoelectric conversion efficiency of miniature temperature-difference battery |
| US20180026170A1 (en) * | 2016-07-25 | 2018-01-25 | Tohoku University | Thermoelectric material and method for producing thermoelectric material |
| JP7125044B2 (en) * | 2018-03-30 | 2022-08-24 | 学校法人東京理科大学 | BATTERY DEVICE, FAILURE MONITORING SYSTEM, AND BATTERY VOLTAGE OUTPUT METHOD |
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