WO2009154019A1 - アルミニウム含有酸化亜鉛系ｎ型熱電変換材料 - Google Patents

アルミニウム含有酸化亜鉛系ｎ型熱電変換材料 Download PDF

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WO2009154019A1
WO2009154019A1 PCT/JP2009/052684 JP2009052684W WO2009154019A1 WO 2009154019 A1 WO2009154019 A1 WO 2009154019A1 JP 2009052684 W JP2009052684 W JP 2009052684W WO 2009154019 A1 WO2009154019 A1 WO 2009154019A1
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thermoelectric conversion
conversion material
aluminum
zinc oxide
type thermoelectric
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PCT/JP2009/052684
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French (fr)
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倫卓 大瀧
和彦 荒木
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独立行政法人科学技術振興機構
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Priority to US12/992,175 priority Critical patent/US8454860B2/en
Publication of WO2009154019A1 publication Critical patent/WO2009154019A1/ja

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    • B—PERFORMING OPERATIONS; TRANSPORTING
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Definitions

  • the present invention relates to a zinc oxide-based thermoelectric conversion material, and particularly to an aluminum-containing zinc oxide-based n-type thermoelectric conversion material.
  • ZnAlO Aluminum doped zinc oxide
  • ZnAlO has a large conductivity (approximately 1000 S / cm) and a large Seebeck coefficient (absolute value of 100 to 200 ⁇ V / ° C; the n-type material displays the Seebeck coefficient as a minus value) over a wide temperature range (0 to 1000 ° C). Therefore, the obtained output factor is 5 to 10 times that of the iron silicide thermoelectric conversion material.
  • ZnAlO does not contain expensive rare elements and can be manufactured at a low cost, has low harmfulness to the human body, and has a higher output factor than other n-type thermoelectric conversion materials.
  • the thermal conductivity is extremely large compared to other n-type thermoelectric conversion materials. Therefore, there is a problem that the figure of merit Z cannot be sufficiently increased despite having a large output factor.
  • ZnAlO is obtained by sintering the raw material powder at about 1200 to 1400 ° C., but many efforts have been made to reduce the large thermal conductivity by devising the manufacturing method, and the average particle size is about 300 nm.
  • a method of obtaining a ZnAlO sintered body having a crystal grain size of 40 ⁇ m or less using fine particles as a raw material Patent Document 3
  • a method of dissolving lanthanum or nickel in ZnAlO Patent Document 4
  • a conductive oxide having crystal anisotropy Patent Document 5
  • Patent Document 6 a method of substituting a part of Zn sites of ZnAlO with Fe
  • Patent Document 5 Patent Document 5
  • Patent Document 6 a method of producing ZnAlO by discharge plasma sintering
  • the oxide thermoelectric conversion material is generally manufactured by a sintering method, but a ZnO-based film material is manufactured using a film forming method such as a sputtering method, a vacuum evaporation method, a CVD method, or a laser ablation method. (Patent Document 9).
  • Japanese Patent Laid-Open No. 62-132380 Japanese Patent Laid-Open No. 08-186293 JP 2001-044520 A JP 2001-284661 A JP 2002-016297 A JP 2007-059491 A JP 2007-246294 A WO2005 / 091393A1 JP 2004-146586 A M. Ohtaki et al. J. Appl. Phys., 79, 1816 (1996) M.Ohtaki et al.Proc.25thInt.Conf.Thermoelectrics, pp.276-279 (2006)
  • thermoelectric conversion materials p-type and n-type are known as thermoelectric conversion materials.
  • a thermoelectric conversion material is a functional material that can extract electricity based on an electromotive force generated by giving a temperature difference to the material, and its performance is generally indicated by a figure of merit Z.
  • the performance index Z is represented by the following formula (1).
  • Z S 2 ⁇ ⁇ / ⁇ (1) (Where S is the Seebeck coefficient [VK ⁇ 1 ], ⁇ is the conductivity [Scm ⁇ 1 ], and ⁇ is the thermal conductivity [Wm ⁇ 1 K ⁇ 1 ].)
  • thermoelectric performance of the thermoelectric conversion material increase Z
  • ZT the dimensionless figure of merit
  • Oxide thermoelectric conversion materials are generally expected to be thermoelectric conversion materials with excellent environmental compatibility that can be used at temperatures as high as 600 to 1000 ° C because they are generally excellent in heat resistance and mechanical strength, safe and inexpensive. The conversion performance is greatly inferior to existing materials at present.
  • the present inventor can greatly reduce the thermal conductivity ⁇ while maintaining a large conductivity ⁇ , and greatly improve the thermoelectric performance. I found out.
  • the present invention relates to a general composition formula: Zn 1-xy Al x Ga y O (where 0.01 ⁇ x ⁇ 0.04, 0.01 ⁇ y ⁇ 0.03, 0.9 ⁇ x / An n-type thermoelectric conversion material comprising aluminum-containing zinc oxide represented by y ⁇ 2.0).
  • the present invention can provide an n-type thermoelectric conversion material having a dimensionless figure of merit (ZT) of 0.2 or more at 600 ° C.
  • ZT dimensionless figure of merit
  • thermoelectric conversion material of the present invention is preferably manufactured by a method of sintering raw material powder, and a sintered body in which fine particles derived from Ga are dispersed while ZnO is simultaneously doped with Al and Ga and dissolved therein. Obtained by.
  • thermoelectric conversion material of the present invention The reason why the dimensionless figure of merit (ZT) of the thermoelectric conversion material of the present invention is greatly increased is that the solid solution amount of Al replacing Zn sites is increased by simultaneously doping aluminum and gallium into zinc oxide, and at the same time, Al Since a fine structure is formed in which fine particles with an estimated particle size of about 100 to 500 nm are dispersed in the matrix, the strain field and grain boundary increase due to irregularities in the matrix crystal lattice Therefore, it is estimated that the thermal conductivity is significantly reduced.
  • ZT dimensionless figure of merit
  • thermoelectric performance Compared to conventional ZnAlO-based thermoelectric conversion materials, ZT has improved thermoelectric performance by more than twice. At the same time, this is the world's highest value for thermoelectric performance of bulk n-type oxide thermoelectric conversion materials.
  • FIG. 3 is a drawing-substituting SEM photograph of a fracture surface of the sintered body obtained in Example 1.
  • FIG. 4 is a graph showing XRD of a sintered body obtained in Comparative Example 1.
  • 6 is a graph showing thermoelectric characteristics of a sintered body obtained in Comparative Example 1.
  • the ZnAlO-based thermoelectric conversion material of the present invention has a general composition formula: Zn 1-xy Al x Ga y O (where 0.01 ⁇ x ⁇ 0.04, 0.01 ⁇ y ⁇ 0.03, 0. 9 ⁇ x / y ⁇ 2.0).
  • Aluminum usually forms a substitutional solid solution in which a part of zinc atoms of zinc oxide is substituted or an interstitial solid solution that enters between crystal lattices of zinc oxide.
  • x indicating the aluminum content is preferably 0.01 ⁇ x ⁇ 0.04, and more preferably 0.015 ⁇ x ⁇ 0.025.
  • x is less than 0.01, the conductivity is low, and a large dimensionless figure of merit (ZT) cannot be obtained.
  • ZT dimensionless figure of merit
  • Gallium is a group 13 element of the periodic table like aluminum, and forms a substitutional solid solution or an interstitial solid solution by doping zinc oxide.
  • zinc oxide is simultaneously doped with aluminum and gallium, the solid solubility limit of aluminum with respect to zinc oxide is expanded, and the production of ZnAl 2 O 4 is suppressed even when the amount of aluminum doped is increased. For this reason, a higher concentration of Al doping is possible than in the case of aluminum alone.
  • Y representing the Ga content is preferably 0.01 ⁇ y ⁇ 0.03, and more preferably 0.015 ⁇ y ⁇ 0.025. If y is less than 0.01, the effect of Ga doping is small.
  • the molar ratio of the content of aluminum and gallium is set to 0.9 ⁇ x / y ⁇ 2.0. When x / y is less than 0.9, the effect of increasing the conductivity by Al doping is insufficient, and when x / y is more than 2.0, formation of ZnAl 2 O 4 cannot be suppressed, which is not preferable. More preferably, 1 ⁇ x / y ⁇ 1.5.
  • the thermoelectric conversion material of the present invention can be produced using a general sintering method using inexpensive raw materials.
  • the Zn source is a ZnO powder raw material having an average particle diameter of 2 ⁇ m or less, preferably about 100 to 500 nm
  • the Al source is an alumina powder having an average particle diameter of 1 ⁇ m or less, preferably about 20 nm to 0.5 ⁇ m
  • the Ga source is an average particle Ga 2 O 3 powder having a diameter of about 20 nm to 2 ⁇ m can be used.
  • Various types of alumina can be used. Among them, ⁇ -type alumina is preferable because ⁇ -type alumina is easily dissolved in zinc oxide.
  • a ZnO powder raw material doped with Al, a ZnO powder raw material mixed with Ga doped powder, or a ZnO powder raw material simultaneously doped with Al and Ga can be used.
  • the sintering temperature is preferably 1000 ° C. to 1420 ° C., more preferably 1300 to 1400 ° C. If the temperature is lower than 1000 ° C., the density of the sintered body does not increase sufficiently, so that the electrical conductivity decreases, which is not preferable. If it exceeds 1420 ° C., zinc oxide begins to sublime during sintering, which is not preferable.
  • the powder is press-molded before sintering, press-molded to a compact density of about 3.5 to 4.5 g / cm 3 and then sintered.
  • the molded body may be sintered after solidifying the slurry containing the raw material powder to produce the molded body.
  • Sintering may be performed in the air, in a vacuum, or in an inert atmosphere, and the sintering time may be one hour or longer, but is preferably about 3 to 7 hours.
  • a sintered body having a relative density of 93 to 98% can be obtained by ordinary normal pressure sintering.
  • hot press sintering method hot isostatic pressing method, discharge plasma sintering method, electric current sintering method, etc.
  • a sintering method may be used.
  • the relative density in this specification is a density calculated by the following formula. That is, the measured density of the bulk material including pores and defects is defined as the bulk density (actual density), the theoretically calculated density not including the pores and defects is defined as the theoretical density, and both densities are expressed as [bulk density / theoretical density ⁇ 100 (%)] is a density calculated by substitution.
  • the average crystal particle size of the thermoelectric conversion material of the present invention is not limited, but is preferably 2 ⁇ m or less, more preferably 500 nm or less and 100 nm or more. This value is the arithmetic average of the measured diameter values obtained by the intercept method or the image analysis method for 100 or more crystal particles randomly selected by observation with an electron microscope.
  • the thermal conductivity ⁇ decreases as the relative density decreases. This is an effect based on porosity due to a decrease in relative density, and such correlation substantially matches the correlation curve theoretically specified by the maxwell equation.
  • the thermal conductivity ⁇ decreases as the measured temperature of the sintered body increases. Therefore, the thermal conductivity ⁇ is reduced as the material is operated in a high temperature environment.
  • thermoelectric conversion material of the present invention is a thin film material using a film forming method as shown in Patent Document 9, for example. It can also be manufactured.
  • a thick film material may be manufactured using a spraying method using a ZnO powder, Al 2 O 3 powder, a mixture of Ga 2 O 3 powder, a molded body, a sintered body, a doctor blade method, a slurry coating method, or the like. it can.
  • a Zn 0.98 Al 0.02 O sintered body was used as a comparative control example.
  • FIG. 1 shows a comparative example and XRD of Zn 0.98-y Al 0.02 Ga y O.
  • An unknown peak corresponding to the amount added was observed at around 35 °. This suggests that the solubility limit of Al is expanded by co-doping Ga with Al.
  • the conductivity of the sintered bodies of the mixed powders A to C showed a metallic behavior as in the comparative example, whereas the sintered bodies of the mixed powders D and E were 5 digits at room temperature. Also exhibited a semiconducting behavior in which the conductivity increased with increasing temperature. Compared with the comparative example, the conductivity of each of the sintered bodies of the mixed powders A to C was slightly reduced. However, as shown in FIG. 3, since the absolute value of the Seebeck coefficient was significantly larger than that of the comparative example, the output factor shown in FIG. 4 greatly exceeded the comparative example.
  • the thermal conductivity reduction rate for ZnAlO by co-doping is not as great as room temperature at high temperatures of about 600 to 1000 ° C., but is still significant in the entire temperature range from room temperature to about 1000 ° C. Reduction is seen.
  • FIG. 7 the SEM photograph of the fracture surface of the sintered compact of mixed powder B and E is shown. While the sintered body of the mixed powder B shown in the upper diagram of FIG. 7 has a dense matrix, the sintered body of the mixed powder E shown in the lower diagram of FIG. It can be seen that the sinterability is poor.
  • the sintered body of the mixed powder B a structure in which dark fine particles having a particle diameter of about 50 to 150 nm are dispersed in a dense ZnO matrix is observed on the entire surface. Since the amount of the fine particles corresponds to the Ga doping amount, it is considered to be a phase derived from Ga, which is considered to be a cause of greatly reducing the thermal conductivity while maintaining a high conductivity.
  • FIG. 2 to 6 show the thermoelectric characteristics of the obtained sintered bodies together with the results of Example 1.
  • FIG. 2 the electrical conductivity of the sintered bodies of the mixed powders F to I all showed a metallic behavior as in the comparative example.
  • the absolute value of the Seebeck coefficient shown in FIG. 3 was slightly smaller in the sintered bodies of the mixed powders F to I.
  • Example 2 instead of the Ga 2 O 3 powder of Example 1, the same group 13 element indium oxide, In 2 O 3 powder, was used, so that Zn 0.97 Al 0.02 In 0.01 O was obtained. A Zn 0.97 Al 0.02 In 0.01 sintered body was produced under the same conditions as in Example 1 except for weighing.
  • FIG. 8 shows XRD of the obtained sintered body together with a comparative control example, Zn 0.97 Al 0.02 Ga 0.01 sintered body.
  • the comparative control example contains a small amount of ZnAl 2 O 4 peak, but the Zn 0.97 Al 0.02 In 0.01 sintered body does not show a peak derived from the ZnAl 2 O 4 peak. It is presumed that the solid solution limit of Al is expanding in the bonded body.
  • Table 2 shows the bulk density, thermal conductivity, and thermal diffusivity of the obtained ZnAlInO sintered body in comparison with a comparative example, Zn 0.98 Al 0.02 Ga 0.01 O.
  • ZnAlO was co-doped with In
  • the thermal conductivity and thermal diffusivity were significantly reduced.
  • FIG. 9 shows the thermoelectric properties of the obtained sintered body in comparison with a comparative example, Zn 0.98 Al 0.02 Ga 0.01 O.
  • Zn 0.98 Al 0.02 In 0.01 O the thermal conductivity was significantly reduced, but at the same time, the conductivity was reduced and no increase in Seebeck coefficient was observed. Therefore, the power factor, the figure of merit, and the dimensionless figure of merit were all below Zn 0.98 Al 0.02 O. From this, it can be seen that even with the same group 13 element, the improvement in thermoelectric performance by co-doping with Al is specifically recognized only in Ga.
  • thermoelectric conversion material of the present invention has a large dimensionless figure of merit ZT, and is particularly useful as an n-type thermoelectric conversion material in applications in a high temperature range of about 600 to 1000 ° C. such as waste heat power generation, geothermal power generation, and solar thermal power generation. Moreover, it can be simply and inexpensively manufactured by a sintering method, a film forming method, or the like using a mixture of oxide powders, a molded body or the like as a raw material.

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Abstract

ＺｎＡｌＯ系熱電変換材料は、熱伝導率κが室温で約４０Ｗ／ｍＫと大きいため、無次元熱電性能指数ＺＴは、１０００°Cで０．３程度と、実用水準の１／３に留まっている。　 一般組成式：Ｚｎ１－ｘ－ｙＡｌｘＧａｙＯ（ただし、０．０１≦ｘ≦０．０４、０．０１≦ｙ≦０．０３、０．９≦ｘ／ｙ≦２．０）で示されるアルミニウム含有酸化亜鉛からなることを特徴とするｎ型熱電変換材料。ＺＴが、１０００°Cにおいて０．６以上が得られる。ＺｎＯにＡｌとＧａを同時ドープ（ｃｏ－ｄｏｐｅ）することにより、大きい導電率σを保持したまま熱伝導率κを大幅に小さくでき、熱電性能が大幅に向上する。

Description

アルミニウム含有酸化亜鉛系ｎ型熱電変換材料
本発明は、酸化亜鉛系熱電変換材料、特に、アルミニウム含有酸化亜鉛系ｎ型熱電変換材料に関する。
亜鉛の一部をアルミニウムに置換した式Ｚｎ１－ｘＡｌｘＯ（０．０１≦ｘ≦０．０５）で示されるアルミニウムドープ酸化亜鉛（以下、「ＺｎＡｌＯ」）は、ｎ型熱電変換材料として知られている（特許文献１、２、非特許文献１）。
ＺｎＡｌＯは、広い温度範囲（０～1000℃）で大きい導電率（約1000Ｓ／ｃｍ）、大きいゼーベック係数（絶対値で100 ～200μＶ／℃；ｎ型材料ではゼーベック係数をマイナスで表示する）を示すため、得られる出力因子も鉄ケイ化物系熱電変換材料の５～１０倍にもなる。
ＺｎＡｌＯは、高価な希少元素を含まず、安価に製造できる、人体に対する有害性が低い、出力因子が他のｎ型熱電変換材料よりも大きい、などの特徴を有する。他方、熱伝導率が他のｎ型熱電変換材料に比して極端に大きい。そのため、大きな出力因子を有するにもかかわらず、性能指数Ｚを十分に大きくすることができないという問題がある。
ＺｎＡｌＯは、原料粉末を１２００～１４００℃程度で焼結することにより得られるが、製造方法を工夫することによって、大きい熱伝導率を小さくする多くの努力がなされており、平均粒径３００ｎｍ程度の微粒子を原料として結晶粒径が４０μｍ以下のＺｎＡｌＯ焼結体を得る方法（特許文献３）、ランタン又はニッケルをＺｎＡｌＯに固溶させる方法（特許文献４）、結晶異方性のある導電性酸化物を生成する物質をＺｎＡｌＯに混合し結晶配向化させる方法（特許文献５）、ＺｎＡｌＯのＺｎサイトの一部をＦｅで置換する方法（特許文献６）、放電プラズマ焼結によりＺｎＡｌＯを製造する方法（特許文献７）などが開発されている。本発明者らは、緻密なＺｎＡｌＯ焼結体にナノ空孔を導入することにより１２５０ＫでのＺＴ＝０．６５が得られることを報告した（特許文献８、非特許文献２）。
なお、酸化物熱電変換材料は一般的には焼結法により製造されるが、ＺｎＯ系膜材料をスパッタリング法、真空蒸着法、ＣＶＤ法、レーザーアブレーション法などの成膜法を用いて製造することもできる（特許文献９）。
特開昭６２－１３２３８０号公報 特開平０８－１８６２９３号公報 特開２００１－０４４５２０号公報 特開２００１－２８４６６１号公報 特開２００２－０１６２９７号公報 特開２００７－０５９４９１号公報 特開２００７－２４６２９４号公報 ＷＯ２００５／０９１３９３Ａ１ 特開２００４－１４６５８６号公報 M.Ohtaki et al.J.Appl.Phys.,79,1816(1996) M.Ohtaki et al.Proc.25thInt.Conf.Thermoelectrics,pp.276-279(2006)
従来、熱電変換材料としては、ｐ型とｎ型とが知られている。熱電変換材料は、材料に温度差を与えて生ずる起電力に基づいて電気を取り出すことができる機能材料であり、その性能は、一般に性能指数Ｚによって示される。具体的には、性能指数Ｚは、下記式（１）によって示される。
Ｚ＝Ｓ２×σ／κ・・・ （１）
（但し、Ｓはゼーベック係数［ＶＫ－１］、σは導電率［Ｓｃｍ－１］、κは熱伝導率［Ｗｍ－１Ｋ－１］を示す。）
ここで、式中の（Ｓ２×σ）は、特に「出力因子」と呼ばれる。熱電変換材料の熱電性能を高める（Ｚを大きくする）ためには、式（１）から考察すると、出力因子を大きくするとともに、熱伝導率κを小さくすることが重要となる。また、動作温度での性能を示す無次元性能指数ＺＴ（Ｔは絶対温度Ｋ）が大きいほど熱電性能が良いといえる。
酸化物熱電変換材料は、一般に耐熱性や機械的強度に優れ、安全、安価なため、６００～１０００℃程度の高温まで利用できる環境適合性に優れた熱電変換材料として期待されるが、その熱電変換性能は現状では既存材料に比べて大きく劣る。
ＺｎＡｌＯ系熱電変換材料は、ＺｎとＡｌのモル含有比をα：β（ただし、α＋β＝１）としたときに、β＝０．０２付近で最も大きな無次元性能指数ＺＴを示すが、熱伝導率κが室温で約４０Ｗ／ｍＫと大きいため、ＺＴは、１０００℃で０．３程度と、実用水準の１／３の大きさに留まっている。また、バルクｎ型酸化物熱電変換材料の過去最高性能は、ＳｒＴｉＯ３系のＺＴ＝０．３７＠１０００Ｋであり、最近の国際学会で、（Ｉｎ,Ｇｅ）2Ｏ3系でＺＴ＝０．４５＠１０００℃の口頭発表がなされたところである。
本発明者は、酸化亜鉛にアルミニウムとガリウムを同時ドープ（ｃｏ－ｄｏｐｅ；共ドープ）することにより、大きい導電率σを保持したまま熱伝導率κを大幅に小さくでき、熱電性能が大幅に向上することを見出した。
すなわち、本発明は、一般組成式：Ｚｎ１－ｘ－ｙＡｌｘＧａｙＯ（ただし、０．０１≦ｘ≦０．０４、０．０１≦ｙ≦０．０３、０．９≦ｘ／ｙ≦２．０）で示されるアルミニウム含有酸化亜鉛からなるｎ型熱電変換材料、である。
本発明は、無次元性能指数(ＺＴ)が、６００℃において０．２以上であるｎ型熱電変換材料を提供することができる。
本発明の熱電変換材料は、好ましくは、原料粉末を焼結する方法で製造し、ＺｎＯにＡｌとＧａを同時ドープし固溶させるとともにＧａに由来する微粒子が分散した焼結体を製造することによって得られる。
本発明の熱電変換材料の無次元性能指数（ＺＴ）が大幅に大きくなる理由は、アルミニウムとガリウムを酸化亜鉛に同時ドープすることによりＺｎサイトを置換するＡｌの固溶量が増加し、同時にＡｌとＧａの複合酸化物と推定される粒径が１００ｎｍ～５００ｎｍ程度の微粒子がマトリックス内に分散した微細組織が形成されるため、マトリックスの結晶格子の不規則性による歪場や結晶粒界の増加によって熱伝導率が大幅に小さくなるものと推測される。
従来のＺｎＡｌＯ系熱電変換材料に比べてＺＴが２倍以上の熱電性能の向上を達成した。同時に、これはバルクｎ型酸化物熱電変換材料の熱電性能として世界最高の値である。
実施例１で得られた焼結体のＸＲＤを示すグラフである。 実施例１及び２で得られた焼結体の熱電特性（導電率の温度依存性）を示すグラフである。 実施例１及び２で得られた焼結体の熱電特性（ゼーベック係数の温度依存性）を示すグラフである。 実施例１及び２で得られた焼結体の熱電特性（出力因子の温度依存性）を示すグラフである。 実施例１及び２で得られた焼結体の熱電特性（熱伝導率の温度依存性）を示すグラフである。 実施例１及び２で得られた焼結体の熱電特性（無次元性能指数の温度依存性）を示すグラフである。 実施例１で得られた焼結体の破断面の図面代用ＳＥＭ写真である。 比較例１で得られた焼結体のＸＲＤを示すグラフである。 比較例１で得られた焼結体の熱電特性を示すグラフである。
以下、本発明のＺｎＡｌＯ系熱電変換材料及びその製造方法について説明する。
本発明のＺｎＡｌＯ系熱電変換材料は、一般組成式：Ｚｎ１－ｘ－ｙＡｌｘＧａｙＯ（ただし、０．０１≦ｘ≦０．０４、０．０１≦ｙ≦０．０３、０．９≦ｘ／ｙ≦２．０）で示される。アルミニウムは、通常、酸化亜鉛の亜鉛原子の一部を置換した置換型固溶体又は酸化亜鉛の結晶格子の間に入り込んだ侵入型固溶体を形成する。
固溶体を形成するには、アルミニウムの含有量を示すｘは、０．０１≦ｘ≦０．０４が好ましく、０．０１５≦ｘ≦０．０２５がより好ましい。ｘが０．０１未満では導電率が低く、大きな無次元性能指数（ＺＴ）を得ることができない。酸化亜鉛にアルミニウムのみを添加した場合（ｙ＝０）には、ｘが０．０３を超えると絶縁体であるＺｎＡｌ2Ｏ4が多量に生成し、ＺＴが小さくなる。
ガリウムは、アルミニウムと同様に周期表の１３族元素であり、酸化亜鉛にドープすることにより、置換型固溶体又は侵入型固溶体を形成する。酸化亜鉛にアルミニウムとガリウムを同時ドープすると、酸化亜鉛に対するアルミニウムの固溶限界が拡大し、アルミニウムのドープ量が増えてもＺｎＡｌ2Ｏ4の生成が抑制される。このため、アルミニウム単独の場合よりも高濃度のＡｌドープが可能になる。
Ｇａの含有量を示すｙは、０．０１≦ｙ≦０．０３が好ましく、０．０１５≦ｙ≦０．０２５がより好ましい。ｙが０．０１未満ではＧａドープの効果が小さく、０．０３を超えると焼結性が悪くなり導電率が小さくなる。アルミニウムとガリウムとの含有量のモル比は、０．９≦ｘ／ｙ≦２．０とする。ｘ／ｙが０．９より小さいとＡｌドープによる導電率を大きくする作用が不足し、また、２．０より大きいとＺｎＡｌ2Ｏ4の生成が抑制できず、好ましくない。より好ましくは１≦ｘ／ｙ≦１．５である。
本発明の熱電変換材料は、安価な原料を用いて一般的な焼結法を用いて製造することができる。Ｚｎ源としては、平均粒径２μｍ以下、好ましくは１００～５００ｎｍ程度のＺｎＯ粉末原料、Ａｌ源としては平均粒径1μｍ以下、好ましくは２０ｎｍ～０．５μｍ程度のアルミナ粉末、Ｇａ源としては平均粒径２０ｎｍ～２μｍ程度のＧａ2Ｏ3粉末を使用することができる。アルミナには各種タイプのものを使うことができるが、中でもγ型のアルミナは酸化亜鉛に固溶しやすいことからγアルミナを用いることが好ましい。また、ＺｎＯ粉末原料にＡｌをドープした粉末、ＺｎＯ粉末原料にＧａをドープした粉末を混合して用いるか、ＺｎＯ粉末原料にＡｌとＧａを同時ドープした粉末を用いることもできる。
焼結温度は１０００℃～１４２０℃が好ましく、より好ましくは１３００～１４００℃とする。１０００℃未満では、焼結体の密度が十分大きくならないので導電率が小さくなり好ましくない。１４２０℃を越えると、焼結中に酸化亜鉛が昇華し始めるようになるので好ましくない。焼結前に粉末をプレス成型し圧粉密度３．５～４．５ｇ/ｃｍ3程度にプレス成型した後焼結することが好ましい。また、原料粉末を含むスラリーを固化して成型体を作製した後、該成型体を焼結してもよい。焼結は、大気中、真空中、不活性雰囲気中いずれでもよく、焼結時間は１時間以上であればよいが、好ましくは３～７時間程度とする。通常の常圧焼結で相対密度が９３～９８％の焼結体が得られるが、ホットプレス焼結法、熱間等方圧焼結法、放電プラズマ焼結法、通電焼結法などの焼結方法を用いてもよい。
なお、本明細書における相対密度は、次式により算出される密度である。即ち、気孔や欠陥を含むバルク体の実測密度を嵩密度（実密度）とし、気孔や欠陥を含まないとして理論的に算出される密度を理論密度とし、両密度を［嵩密度／理論密度×１００（％）］に代入することによって算出される密度である。
本発明の熱電変換材料の平均結晶粒子径は限定的ではないが、２μｍ以下が好ましく、５００ｎｍ以下１００ｎｍ以上がより好ましい。なお、この値は、電子顕微鏡による観察により無作為に選択した１００個以上の結晶粒子についてインターセプト法又は画像解析法により求めた直径の測定値の算術平均である。
本発明の熱電変換材料は、相対密度の低下に伴って、熱伝導率κは小さくなる。これは、相対密度の低下によって多孔化することに基づく効果であり、かかる相関関係はｍａｘｗｅｌｌの式により理論的に特定される相関曲線と実質的に一致する。また、相対密度を固定した場合には、焼結体の測定温度が高くなるに従って熱伝導率κは小さくなるため、高温環境下で動作させる材料として用いる場合ほど、熱伝導率κを小さくした状態で使用できる。
以上、原料粉末の成型体を用いてバルク焼結体を製造する場合について説明したが、本発明の熱電変換材料は、例えば、特許文献９に示されるような成膜方法を用いて薄膜材料を製造することもできる。また、ＺｎＯ粉末、Ａｌ2Ｏ3粉末、Ｇａ2Ｏ3粉末の混合物、成形体、焼結体等を用いる溶射法、ドクターブレード法、スラリーコーティング法などを用いて厚膜材料を製造することもできる。
キシダ化学（株）製ＺｎＯ（純度99.5%）粉末、キシダ化学（株）製アルミニウムイソプ
ロポキシドを加水分解し焼成して得たγ―Ａｌ2 Ｏ3 粉末、ならびにキシダ化学（株）製Ｇａ２Ｏ３（純度99.99%）粉末をＺｎ０．９８－yＡｌ０．０２Ｇａy（ｙ＝０．０１，０．０２，０．０３，０．０４，０．０５）となるように夫々秤量し、ボールミルで２４時間の粉砕混合を行ない、混合粉末Ａ（ｙ＝０．０１）、Ｂ（ｙ＝０．０２）、Ｃ（ｙ＝０．０３）、Ｄ（ｙ＝０．０４）、Ｅ（ｙ＝０．０５）を調製した。この混合粉末Ａ～Ｅをそれぞれ乳鉢粉砕し、５１ｋｇｆ／ｃｍ２で一軸加圧成型、１１３０ｋｇｆ／ｃｍ２で等方静水圧成型し窒素雰囲気下で１４００℃、５時間の焼結を行なった。なお、Ｚｎ０．９８Ａｌ０．０２Ｏ焼結体を比較対照例とした。
図１に、比較対照例及びＺｎ０．９８－ｙＡｌ０．０２ＧａｙＯのＸＲＤを示す。ＺｎＡｌＯ及び混合粉末Ａ（ｙ＝０．０１）の焼結体で見られたＺｎＡｌ２Ｏ４に帰属されるピークは混合粉末、Ｂ（ｙ＝０．０２），Ｅ（ｙ＝０．０５）の焼結体では見られず、３５°付近に添加量に応じたunknownピークが見られた。このことから、ＧａをＡｌと同時ドープすることによりＡｌの固溶限の拡大が示唆される。
図２～図６に、得られた各焼結体の熱電特性を示す。図２に示すとおり、混合粉末Ａ～Ｃの焼結体の導電率が比較対照例と同様に金属的挙動を示したのに対して、混合粉末ＤとＥの焼結体は室温で５桁も小さい導電率となり、昇温と共に導電率が大きくなる半導体的挙動を示した。比較対照例と比較すると、混合粉末Ａ～Ｃの焼結体のいずれも導電率はやや小さくなった。しかし、図３に示すように、ゼーベック係数の絶対値は比較対照例よりも大幅に大きくなったため、図４に示す出力因子は比較対照例を大きく上回るものとなった。
図５に示すとおり、同時ドープによるＺｎＡｌＯに対する熱伝導率の低減率は、６００～１０００℃程度の高温では室温ほどの大きな低減率ではないが、それでも室温から１０００℃程度までの全温度領域で有意な低減が見られる。図６に示す無次元性能指数ＺＴは比較対照例に比べて大幅に大きくなり、Ｚｎ０．９７Ａｌ０．０２Ｇａ０．０１Ｏにおいて、ＺＴ＝０．６１（＠１０００℃）、Ｚｎ０．９６Ａｌ０．０２Ｇａ０．０２Ｏにおいて、ＺＴ＝０．６５（＠１０００℃）と従来の２倍の熱電性能が得られた。図６では、６００℃において０．２未満の場合もあるが、これらの組成でも焼結方法の選択、焼結条件等を工夫することにより０．２以上とすることは可能である。表１に、得られた焼結体のかさ密度、熱伝導率、熱拡散率を示す。
Figure JPOXMLDOC01-appb-T000001
図７に、混合粉末Ｂ、Ｅの焼結体の破断面のＳＥＭ写真を示す。図７の上図に示す混合粉末Ｂの焼結体は緻密なマトリックスを持っているのに対して、図７の下図に示す混合粉末Ｅの焼結体は粗大な空孔が見られ、非常に焼結性が悪いことが分かる。また、混合粉末Ｂの焼結体には、ＺｎＯの緻密なマトリックス中に粒径５０～１５０ｎｍ程度の暗色の微粒子が分散した組織が全面に認められる。この微粒子の量はＧａのドープ量に対応するため、Ｇａ由来の相であると考えられ、大きい導電率を保ったまま熱伝導率が大幅に小さくなる一因と考えられる。
実施例１と同様に、原料酸化物粉末をＺｎ1－ｘ－ｙＡｌｘＧａｙ（ｘ＝０．０３，０．０４；ｙ＝０．０１，０．０２，０．０３）となるように夫々秤量し、ボールミルで２４時間の粉砕混合を行ない混合粉末Ｆ（ｘ＝０．０３，ｙ＝０．０１）、Ｇ（ｘ＝０．０３，ｙ＝０．０２）、Ｈ（ｘ＝０．０３，ｙ＝０．０３）、Ｉ（ｘ＝０．０４，ｙ＝０．０２）を調製した。これらの混合粉末について、実施例１と同じ条件で焼結体を製造した。
図２～図６に、得られた各焼結体の熱電特性を実施例１の結果と合わせて示す。図２に示すとおり、混合粉末Ｆ～Ｉの焼結体の導電率は、全て、比較対照例と同様に金属的挙動を示した。同じＧａ量の試料を比較すると、Ａｌ量ｘ＝０．０３である混合粉末Ｆ～Ｉの焼結体の方がＡｌ量ｘ＝０．０２である混合粉末Ａ～Ｃの焼結体に比べて大きい導電率を示した。このことから、Ｇａの同時ドープによりＡｌの固溶限界が拡大し、高濃度のＡｌドープによってキャリアが有効に生成していることが分かる。
これに伴って、図３に示すゼーベック係数の絶対値は混合粉末Ｆ～Ｉの焼結体の方がやや小さくなった。図４に示す出力因子は、混合粉末Ｈ（ｘ＝０．０３，ｙ＝０．０３）の焼結体を除けばほぼ全温度領域で比較対照例を上回るものとなった。
図５に示すとおり、Ｇａ量ｙが大きいほど熱伝導率は小さくなるため、図６に示すとおり、無次元性能指数ＺＴは混合粉末Ｄ、Ｅの焼結体を除く全ての試料で比較対照例に比べて大きくなり、特に、６００～７００℃の中温域ではＧａ量ｙ＝０．０３の試料で約２倍、ｙ＝０．０２の試料では約３倍の熱電性能の向上が得られた。
［比較例１］
実施例１のＧａ２Ｏ３粉末に代えて、同じ１３族元素のインジウムの酸化物であるＩｎ２Ｏ３粉末を用いてＺｎ０．９７Ａｌ０．０２Ｉｎ０．０１Ｏとなるように夫々秤量した他は実施例１と同じ条件でＺｎ０．９７Ａｌ０．０２Ｉｎ０．０１焼結体を製造した。
図８に、得られた焼結体のＸＲＤを、比較対照例、Ｚｎ０．９７Ａｌ０．０２Ｇａ０．０１焼結体と共に示す。比較対照例は少量のＺｎＡｌ２Ｏ４ピークを含むが、Ｚｎ０．９７Ａｌ０．０２Ｉｎ０．０１焼結体ではＺｎＡｌ２Ｏ４ピークに由来するピークは見られず、このことからＺｎＡｌＩｎＯ焼結体ではＡｌの固溶限が拡大している可能性が推測される。
表２に、得られたＺｎＡｌＩｎＯ焼結体のかさ密度、熱伝導率、熱拡散率を比較対照例、Ｚｎ０．９８Ａｌ０．０２Ｇａ０．０１Ｏと比較して示す。ＺｎＡｌＯにＩｎを同時ドープした焼結体ではかさ密度が増大したにも係わらず、熱伝導率、熱拡散率が大幅に小さくなった。
Figure JPOXMLDOC01-appb-T000002
図９に、得られた焼結体の熱電特性を比較対照例、Ｚｎ０．９８Ａｌ０．０２Ｇａ０．０１Ｏと比較して示す。Ｚｎ０．９８Ａｌ０．０２Ｉｎ０．０１Ｏでは熱伝導率が大幅に小さくなったものの、同時に導電率も小さくなり、ゼーベック係数の増大も見られなかった。そのため、出力因子、性能指数、無次元性能指数共にＺｎ０．９８Ａｌ０．０２Ｏを下回るものとなった。このことから、同じ１３族元素であっても、Ａｌとの同時ドープによる熱電性能の向上はＧａのみに特異的に認められることが分かる。
本発明の熱電変換材料は、無次元性能指数ＺＴが大きく、ｎ型熱電変換材料として廃熱発電、地熱発電、太陽熱発電等の６００～１０００℃程度の高温域での用途に特に有用である。また、原料として酸化物粉末の混合物、成型体等を用いる焼結法、成膜法等によって簡便に安価に製造できる。

Claims (3)

  1. 一般組成式：Ｚｎ１－ｘ－ｙＡｌｘＧａｙＯ（ただし、０．０１≦ｘ≦０．０４、０．０１≦ｙ≦０．０３、０．９≦ｘ／ｙ≦２．０）で示されるアルミニウム含有酸化亜鉛からなることを特徴とするｎ型熱電変換材料。
  2. 無次元性能指数(ＺＴ)が、６００℃において０．２以上であることを特徴とする請求項１に記載のｎ型熱電変換材料。
  3. 原料粉末を焼結することによってＺｎＯにＡｌとＧａを同時ドープし固溶させるとともにＧａに由来する微粒子が分散した微細組織を形成することを特徴とする請求項１又は２に記載のｎ型熱電変換材料の製造方法。
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Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2361887A1 (en) * 2010-02-25 2011-08-31 Corning Incorporated A process for manufacturing a doped or non-doped zno material and said material
FR2956924A1 (fr) * 2010-03-01 2011-09-02 Saint Gobain Cellule photovoltaique incorporant une nouvelle couche tco
CN106747403A (zh) * 2016-11-30 2017-05-31 大连交通大学 铝掺杂氧化锌粉体及其陶瓷制备方法

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP5729679B2 (ja) * 2010-07-07 2015-06-03 Toto株式会社 熱電変換材料およびその製造方法
CN112216783B (zh) * 2020-09-30 2022-11-25 西安理工大学 一种Ga-Ti掺杂ZnO块体热电材料的制备方法

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH01262678A (ja) * 1988-04-14 1989-10-19 Murata Mfg Co Ltd 積層熱電素子およびその製造方法
WO2005093864A1 (ja) * 2004-03-25 2005-10-06 National Institute Of Advanced Industrial Science And Technology 熱電変換素子及び熱電変換モジュール
JP2007059491A (ja) * 2005-08-22 2007-03-08 Murata Mfg Co Ltd ｎ型熱電変換材料および熱電変換素子
WO2007108147A1 (ja) * 2006-03-22 2007-09-27 Murata Manufacturing Co., Ltd. 熱電半導体、熱電変換素子および熱電変換モジュール

Family Cites Families (10)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS62132380A (ja) 1985-12-05 1987-06-15 Toshiba Corp Ｎ型熱電素子
JPH08186293A (ja) 1994-12-28 1996-07-16 Seibu Gas Kk 熱発電材料
JP2001044520A (ja) 1999-08-03 2001-02-16 Unitika Ltd 熱電半導体およびその製造方法
JP2001284661A (ja) 2000-03-30 2001-10-12 Unitika Ltd 高温用ｎ型熱電素子組成物
JP4592209B2 (ja) 2000-04-28 2010-12-01 株式会社豊田中央研究所 結晶配向バルクＺｎＯ系焼結体材料の製造方法およびそれにより製造された熱電変換デバイス
US20030163946A1 (en) * 2002-03-01 2003-09-04 Berlowitz Paul Joseph Low emissions fuel emulsion
JP4277506B2 (ja) 2002-10-24 2009-06-10 株式会社村田製作所 熱電変換素子の熱電材料用のＺｎＯ系薄膜、該ＺｎＯ系薄膜を用いた熱電変換素子、及び赤外線センサ
WO2005091393A1 (ja) 2004-03-22 2005-09-29 Japan Science And Technology Agency 多孔質熱電材料及びその製造方法
JP4900569B2 (ja) 2006-03-13 2012-03-21 国立大学法人東北大学 アルミニウム含有酸化亜鉛焼結体の製造方法
JP2010512664A (ja) * 2006-12-11 2010-04-22 ルーメンツ リミテッド ライアビリティ カンパニー 酸化亜鉛多接合光電池及び光電子装置

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPH01262678A (ja) * 1988-04-14 1989-10-19 Murata Mfg Co Ltd 積層熱電素子およびその製造方法
WO2005093864A1 (ja) * 2004-03-25 2005-10-06 National Institute Of Advanced Industrial Science And Technology 熱電変換素子及び熱電変換モジュール
JP2007059491A (ja) * 2005-08-22 2007-03-08 Murata Mfg Co Ltd ｎ型熱電変換材料および熱電変換素子
WO2007108147A1 (ja) * 2006-03-22 2007-09-27 Murata Manufacturing Co., Ltd. 熱電半導体、熱電変換素子および熱電変換モジュール

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP2361887A1 (en) * 2010-02-25 2011-08-31 Corning Incorporated A process for manufacturing a doped or non-doped zno material and said material
WO2011106347A1 (en) * 2010-02-25 2011-09-01 Corning Incorporated A process for manufacturing a doped or non-doped zno material and said material
FR2956924A1 (fr) * 2010-03-01 2011-09-02 Saint Gobain Cellule photovoltaique incorporant une nouvelle couche tco
WO2011107701A1 (fr) * 2010-03-01 2011-09-09 Saint-Gobain Glass France Cellule photovoltaïque incorporant une nouvelle couche tco
CN106747403A (zh) * 2016-11-30 2017-05-31 大连交通大学 铝掺杂氧化锌粉体及其陶瓷制备方法

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