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Complex mixed conductor containing Pr-doped cerium oxide and spinel-type ferrite and its preparation method

外国特許コード F110003169
整理番号 A151-02US2
掲載日 2011年6月17日
出願国 アメリカ合衆国
出願番号 78394607
公報番号 20070252114
公報番号 7479242
出願日 平成19年4月13日(2007.4.13)
公報発行日 平成19年11月1日(2007.11.1)
公報発行日 平成21年1月20日(2009.1.20)
国際出願番号 JP2003004435
国際公開番号 WO2003084894
国際出願日 平成15年4月8日(2003.4.8)
国際公開日 平成15年10月16日(2003.10.16)
優先権データ
  • 特願2002-108504 (2002.4.10) JP
  • 10/510,343 (2004.10.5) US
  • 2003JP004435 (2003.4.8) WO
発明の名称 (英語) Complex mixed conductor containing Pr-doped cerium oxide and spinel-type ferrite and its preparation method
発明の概要(英語) It is a composite-type mixed oxygen ion and electronic conductor, in which an oxygen ion conductive phase consists of gadolinium-doped cerium oxide (GDC), an electronic conductive phase consists of spinel-type ferrite (CFO), the particle diameters of both phases are 1 mum or less, respectively, both phases are uniformly mixed mutually, and both phases form respective conductive networks.
Both phases have low solid solubility mutually, chemical reactions are not easily caused between both phases, and even if chemical reactions are caused between both phases, different phase to disturb mixed conductivity is not formed.
And it has high oxygen permeability, and does not easily cause aged deterioration.
従来技術、競合技術の概要(英語) BACKGROUND ART
A composite-type mixed oxygen ion and electronic conductor having mixed electrical conductivity arising from oxygen ions and electrons has simultaneously high oxygen ion conductivity and electronic conductivity.
In order to apply this substance to the above-mentioned fields, such properties are required as that high mixed electrical conductivity must be maintained in the range from high partial oxygen pressure such as air to extremely low partial oxygen pressure such as hydrogen gas or methane gas, and also chemically and mechanically stable in temperature range of 500-1000 deg. C. where it is generally used.
The mixed conductor having mixed electrical conductivity arising from oxygen ions and electrons (the mixed conductor) has two types as shown below in wide classification.
(1) Single-Phase Mixed Conductor
This is the type that the substance itself has mixed conductivity, and as examples, Perovskite-type oxides in La -- Sr -- Co -- Fe, and La -- Sr -- Ga -- Fe systems are well known (See Ref.: Chem. Lett., 1985, 1743, Am.
Ceram. Soc. Bull., 74, 1995, 71, Catal.
Today, 36, 1997, 265, Solid State Ionics, 129, 2000, 285, Solid State Ionics, 135, 2000, 631.).
(2) Composite-Type Mixed Conductor
This is the type in which mixed conductivity is realized by making a composite from two substances one of which shows, as a single component, oxygen ion conductivity, and the other of which shows, as a single component, electronic conductivity, and for examples, the composite of an ionic conductor such as yttria-stabilized zirconia (YSZ) and an electronic conductor such as metal Pd, or the composite of gadolinium-doped cerium oxide and Perovskite-type oxides in La -- Sr -- Mn system are known.
In case of a single-phase mixed conductor, the substances are extremely limited to obtain high mixed conductivity, while for a composite-type mixed conductor wide varieties of substances are applicable.
Also in case of composite-type mixed conductors, since several other species of substances are able to be included, it is possible to impart secondary functions, such as catalytic function.
However, composite-type mixed conductors have their own problems.
For example, in YSZ-Pd composite, since one component is a ceramics while the other is a metal, it is difficult to obtain densified sintered product, and even if it is obtained, in case of the thermal expansion coefficients widely different in the two phases, cracking may be caused by thermal cycles or other like phenomena.
Further, it is necessary to form conductive networks of oxygen ion conductive phase and electronic conductive phase, respectively, in order to realize mixed conductivity, so that it is required to take into consideration the problem of percolation based on the volume ratio of the phases.
Here, percolation is such a phenomenon that, for example, when metal powders are mixed into insulation matrix to obtain electrical conductivity, if the volume ratio of metal powders to insulation matrix exceeds a certain value (critical volume ratio), the network of metal powder is formed in the insulator, and the conductivity increases suddenly.
It is also pointed out for the composite of gadolinium-doped cerium oxide and Perovskite-type oxides in La -- Sr -- Mn system that, even when high mixed conductivity is attained, the two phases cause chemical reaction upon using at high temperature, and a different phase is formed to disturb mixed conductivity at interface (See Ref.: Solid State Ionics 146, 2002, 163, and J. Eur. Ceram. Soc. 21, 2001, 1763.).
In view of the above-mentioned problems, it is the first object of the present invention to provide a composite-type mixed oxygen ion and electronic conductor, in which oxygen ion conductive phase and electronic conductive phase are uniformly mixed, thereby cracking due to the difference of thermal expansion coefficient does not occur, oxygen ion conductive phase and electronic conductive phase respectively form conductive networks, and a different phase to disturb mixed conductivity is not formed by the reaction of both phases, consequently oxygen permeability is high, and aged deterioration does not easily occur.
In addition, it is the second object to provide the method to manufacture said composite-type mixed oxygen ion and electronic conductor.

特許請求の範囲(英語) [claim1]
1. A composite-type mixed oxygen ion and electronic conductor, characterized in that its oxygen ion conductive phase consists of praseodymium-doped cerium oxide (composition formula: Ce1-xPrxO2-x/2, where 0<x<0.5) and its electronic conductive phase consists of spinel-type ferrite (composition formula: MFe2O4, where M=Mn, Fe, Co, or Ni).
[claim2]
2. A composite-type mixed oxygen ion and electronic conductor as set forth in claim 1, characterized in that said oxygen ion conductive phase contains a catalyst or catalysts to accelerate conversion of oxygen gas to oxygen ion or oxygen ion to oxygen, or is coated with said catalysts, or contains said catalysts and coated with said catalysts on the surface.
[claim3]
3. A composite-type mixed oxygen ion and electronic conductor as set forth in claim 1, characterized in that said oxygen ion conductive phase contains a catalyst or catalysts to accelerate conversion of oxygen gas to oxygen ion or oxygen ion to oxygen, or is coated with said catalysts, or contains said catalysts and coated with said catalysts on the surface.
[claim4]
4. A composite-type mixed oxygen ion and electronic conductor as set forth in claim 3, characterized in that said catalyst is Ru or Ni, or their combination.
[claim5]
5. A composite-type mixed oxygen ion and electronic conductor as set forth in claim 1, characterized in that volume composition ratio of said electronic conductive phase to oxygen ion conductive phase is in the range of 5 to 40%.
[claim6]
6. A method of manufacturing a composite-type mixed oxygen ion and electronic conductor, characterized in that it comprises the steps of: polymerizing by mixing metal salts of metals constituting praseodymium-doped cerium oxide, metal salts of metals constituting spinel-type ferrite, a catalyst or catalysts to accelerate conversion of oxygen gas to oxygen ion and oxygen ion to oxygen, a chelate complex, and a chelate polymerization initiator;
carbonizing said polymerized mixed phase;dissociating carbons of said carbonized mixed phase by oxidation to obtain oxides of said metals;grinding said metal oxides to powders;
and
sintering said powders after isostatic pressing.
[claim7]
7. A method of manufacturing a composite-type mixed oxygen ion and electronic conductor as set forth in claim 6, characterized in that said metal salts constituting praseodymium-doped cerium oxide are Ce(NO3)3.6H2O and Pr(NO3)3.6H2O, or Ce(NO3)3.6H2O and Pr(OH)3.6H2O,and said metal salts constituting spinel-type ferrite is one or more salts selected from the group which consists of Fe(NO3)3.9H2O, Co(NO3)2.6H2O, Ni(NO3)2.6H2O, and Mn(NO3)2.6H2O,and said catalyst or catalysts is one or more elements selected from the group which consists of Ru and Ni,and said chelate complex is anhydrous citric acid,and said chelate polymerization initiator is ethylene glycol.
[claim8]
8. A method of manufacturing a composite-type mixed oxygen ion and electronic conductor, characterized in that it comprises the steps of: polymerizing by mixing metal salts of metals constituting praseodymium-doped cerium oxide, metal salts of metals constituting spinel-type ferrite, a chelate complex, and a chelate polymerization initiator;carbonizing said polymerized mixed phase;dissociating carbons of said carbonized mixed phase by oxidation to obtain oxides of said metals;grinding said metal oxides to powders;
and
sintering said powders after isostatic pressing.
[claim9]
9. A method of manufacturing a composite-type mixed oxygen ion and electronic conductor as set forth in claim 8, characterized in that said metal salts constituting praseodymium-doped cerium oxide are Ce(NO3)3.6H2O and Pr(NO3)3.6H2O, or Ce(NO3)3.6H2O and Pr(OH)3.6H2O,and said metal salts constituting spinel-type ferrite is one or more salts selected from the group which consists of Fe(NO3)3.9H2O, Co(NO3)2.6H2O, Ni(NO3)2.6H2O, and Mn(NO3)2.6H2O,and said catalyst or catalysts is one or more elements selected from the group which consists of Ru and Ni,and said chelate complex is anhydrous citric acid,and said chelate polymerization initiator is ethylene glycol.
  • 発明者/出願人(英語)
  • TAKAMURA HITOSHI
  • OKADA MASUO
  • JAPAN SCIENCE AND TECHNOLOGY AGENCY
国際特許分類(IPC)
米国特許分類/主・副
  • 252/521.1
  • 423/593.1
参考情報 (研究プロジェクト等) CREST Research and Development of System Technologies for Resource Recycling and Minimum Energy Requirement AREA
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