Defect Chemistry of the Mixed Conducting Cage Compound Ca12Al14O33

다국어 초록 (Multilingual Abstract)

The electrical transport properties of mayenite (Ca12Al14O33 or 12CaO·7Al2O3; mostly abbreviated as C12A7) can be controlled in a wide range by varying the oxygen deficiency: At high temperatures mayenite becomes either an oxygen solid electrolyte, a mixed ionic/electronic conductor or an inorganic electride with metal-like properties upon chemical reduction (removing oxygen). The underlying defect chemistry can be understood on the basis of a relatively simple model – despite the complex cage structure: A point defect model based on the assumption that the framework [Ca12Al14O32]2+ acts as a pseudo-donor describes well the high temperature transport properties. It accounts for the observed conductivity plateau at higher oxygen activities and also describes the experimentally observed oxygen activity dependence of the electronic conductivity with −1/4 slope at temperatures between 800 and 1000oC. Doping effects in mayenite are still not well explored, and we review briefly the existing data on doping by different elements. Hydration of mayenite plays a crucial role, as Mayenite is hygroscopic, which may be a major obstacle for technical applications.

참고문헌 (Reference)

1 J. T. S. Irvine, 19 : 410-412, 1989

2 H. B. Bartl, 35 : 547-552, 1970

3 K. Kajihara, "Vibrational Dynamics and Oxygen Diffusion in a Nanoporous Oxide Ion Conductor 12CaO·7Al2O3 Studied by 18O Labeling and Micro-Raman Spectroscopy" 111 : 14855-14861, 2007

4 K. Hayashi, "Thermodynamics and Kinetics of Hydroxide Ion Formation in 12CaO ·7Al2O3" 109 : 11900-11906, 2005

5 S. W. Kim, "Thermal Conductivity and Seebeck Coefficient of 12CaO·7Al2O3 Electride with a Cage Structure" 80 : 075201-, 2009

6 H. Boysen, "Structure and Oxygen Mobility in Mayenite (Ca12Al14O33): A High- Temperature Neutron Powder Diffraction Study" B63 : 675-682, 2007

7 L. Palacios, "Structure and Electrons in Mayenite Electrides" 47 : 2661-2667, 2008

8 P. V. Sushko, "Role of Hydrogen Atoms in the Photoinduced Formation of Stable Electron Centers in H-doped 12CaO·7Al2O3" 73 : 045120-, 2006

9 M. Mogensen, "Physical Properties of Mixed Conductor Solid Oxide Fuel Cell Anodes of Doped CeO2" 141 : 2122-2128, 1994

10 J. T. S. Irvine, "Oxide Ion Conductivity in Ca12Al14O33" 23 : 1033-1038, 1988

11 H. Hosono, "Occurrence of Superoxide Radical Ion in Crystalline Calcium Aluminate 12CaO·7Al2O3 Prepared via Solid-State Reactions" 26 : 1192-1195, 1987

12 K. Hayashi, "Microporous Crystal 12CaO· 7Al2O3 Encaging Abundant O- Radicals" 124 : 738-739, 2002

13 S. W. Kim, "Metallic State in a Lime−Alumina Compound with Nanoporous Structure" 7 : 1138-1143, 2007

14 P. V. Sushko, "Mechanisms of Oxygen Ion Diffusion in a Nanoporous Complex Oxide 12CaO·7Al2O3" 73 : 014101-, 2006

15 S. Matsuishi, "Localized and Delocalized Electrons in Room-Temperature Stable Electride [Ca24Al28O64]4+(O2-)2-x(e-)2x: Analysis of Optical Reflectance Spectra" 112 : 4753-4760, 2008

16 K. Hayashi, "Light-Induced Conversion of an Insulating Refractory Oxide into a Persistent Electronic Conductor" 419 : 462-465, 2002

17 Z. Li, "Is Mayenite without Clathrated Oxygen an Inorganic Electride?" 43 : 6479-6482, 2004

18 K. Hayashi, "Hydride Ion as a Two-Electron Donor in a Nanoporous Crystalline Semiconductor 12CaO·7Al2O3" 109 : 23836-23842, 2005

19 J. E. Medvedeva, "Hopping versus Bulk Conductivity in Transparent Oxides: 12CaO· 7Al2O3" 85 : 955-957, 2004

20 K. L. Scrivener, "Historical and Present Day Applications of Calcium Aluminate Cements in Calcium Alu-minate Cements" IOM communications Ltd 3-23, 2001

21 R. Strandbakke, "High-Temperature Hydration and Conductivity of Mayenite, Ca12Al14O33" 113 : 8938-8944, 2009

22 S. Matsuishi, "High-Density Electron Anions in a Nanoporous Single Crystal: [Ca24Al28O64]4+(4e-)" 301 : 626-629, 2003

23 M. Lacerda, "High Oxide Ion Conductivity in Ca12Al14O33" 332 : 525-526, 1988

24 P. V. Sushko, "From Insulator to Electride: A Theoretical Model of Nanoporous Oxide 12CaO·7Al2O3" 129 : 942-951, 2007

25 K. Hayashi, "Formation of Oxygen Radicals in 12CaO· 7Al2O3: Instability of Extraframework Oxide Ions and Uptake of Oxygen Gas" 108 : 8920-8925, 2004

26 J. A. Imlach, "Excess Oxygen and the Stability of 12CaO·7A12O3" 1 : 57-61, 1971

27 O. Trofymluk, "Energetics of Formation and Oxidation of Microporous Calcium Aluminates: A New Class of Electrides and Ionic Conductors" 17 : 5574-5579, 2005

28 J.-H. Park, "Electronic Transport in 8 Mole Percent Y2O3-ZrO2" 136 : 2867-2876, 1989

29 J. E. Medvedeva, "Electronic Structure and Light-Induced Conductivity of a Transparent Refractory Oxide" 93 : 016408-, 2004

30 P. V. Sushko, "Electron Localization and a Confined Electron Gas in Nanoporous Inorganic Electrides" 91 : 126401-, 2003

31 S.-W. Kim, "Electron Carrier Generation in a Refractory Oxide 12CaO· 7Al2O3 by Heating in Reducing Atmosphere: Conversion from an Insulator to a Persistent Conductor" 89 : 3294-3298, 2006

32 M. Lacerda, "Electrical Properties of Ca12Al14O33: Effect of Hydrogen Reduction" 59 : 257-262, 1993

33 D.-K. Lee, "Defect Chemistry of the Cage Compound, Ca12Al14O33-δ - Understanding the Route from a Solid Electrolyte to a Semiconductor and Electride" 11 : 3105-3114, 2009

34 J. Jeevaratnam, "Anion Substitution and Structure of 12CaO·7Al2O3" 47 : 105-106, 1964