記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1126/science.1083842

記述言語：英語   掲載種別：研究論文（学術雑誌）  

The effects of oxygen partial pressure (p_O2<sub/>) up to 400 atm on the generation of active oxygen radicals in 12CaO·7Al₂O₃ (C12A7) was examined using a hot isostatic pressing technique. Concentrations of superoxide (O₂
^-) and oxygen anion radicals (O^-), which were analyzed from a combination of electron paramagnetic spin resonance (EPR) and Raman spectroscopy, increased with p_O2<sub/>. The total concentration of the radicals reached 1.7 × 10²¹ cm³, which is comparable to the theoretical maximum, confirmed that dominant radical incorporation process is O^2- (cage) + O₂ (atmosphere) → O^- (cage) + O₂
^- (cage). The radical incorporated C12A7 has a large magnetic susceptibility that obeys Curie's law down to 2.5 K without magnetic ordering, although a weak exchange interaction was suggested by the line narrowing of the EPR signal.

DOI： 10.1021/cm020959g

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1038/nature01053

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Extremely high concentrations (>10²⁰ cm^-3) of active oxygenic radicals, O^- and O₂
^-, have been created in the zeolitic crystal, 12CaO·7Al₂O₃ (C12A7), which can accommodate anions in its cavities. An increase in oxygen pressure and a decrease in water vapor pressure at high temperature enhance the formation of the radicals. The oxidation of Pt is observed on the surface of the material as a result of reaction with the active oxygens.

DOI： 10.1021/ja016112n

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1111/j.1151-2916.1996.tb08780.x

出版者・発行元：Japanese Journal of Applied Physics, Part 1: Regular Papers and Short Notes and Review Papers  

Wurtzite-type ferroelectrics have attracted much attention as next-generation ferroelectric materials due to their high spontaneous polarizations since the first experimental demonstration of polarization switching for Sc-doped AlN. However, wurtzite-type ferroelectrics require high electric fields to switch their polarization direction, resulting in small margins with breakdown electric fields. To address this issue, considerable efforts have been made to explore wurtzite ferroelectrics with moderate switching barriers. In this study, our first-principles calculations have predicted the ferroelectricity of defective wurtzite α-Ga2S3. The calculated polarization is 60 μC cm−2, which is comparable to or smaller than those of conventional wurtzite ferroelectrics. The minimum energy pathway associated with polarization switching reveals a moderate switching barrier of 67 meV/atom. The energy landscape for α-Ga2S3 is quite different from that for its isostructural Al-based counterpart α-Al2S3, which our recent theoretical study has predicted to have quadruple-well ferroelectricity. The difference in chemical bonding between cations and sulfide ions accounts for their different energy landscapes for polarization switching.

DOI： 10.35848/1347-4065/ad6c59

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Scopus

出版者・発行元：ACS Materials Letters  

Highly conductive solid electrolytes (SEs) are a prerequisite for developing all-solid-state batteries. Recently, Li-ion conducting halide-based SEs have attracted enormous attention owing to their electrochemical, mechanical, and transport properties. Despite the success of Li-ion conducting halides, the research on the Na analogue remains sparse, and the reported ionic conductivities are limited. In this study, we demonstrate the significantly improved ionic conductivity in NaM5+Cl6 (M5+ = Nb, Ta) by extending the existing structural framework of the Na-ion conducting halides Na3M3+Cl6 (M3+ = Y, Er) and Na2ZrCl6. Transport analysis reveals that the cation M rules the activation energies of the resulting phases. Given that M is pivotal, a further fine-tuning of M in NaMCl6 leads to a high ionic conductivity of 0.1 mS cm-1 at 30 °C, owing to a beneficial inductive effect and enhanced migration entropy. These discoveries will provide more design strategies for Na-ion conducting halide-based SEs.

DOI： 10.1021/acsmaterialslett.4c00315

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： https://pubs.acs.org/doi/full/10.1021/acsmaterialslett.4c00315

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： https://doi.org/10.1021/acs.chemmater.3c01150

記述言語：英語  

On the background of the urgent demand to realize a decarbonized society, energy storage technology plays a key role in shifting from social activities founded on the combustion of fossil fuels to those based on renewable energy resources. Toward this end, global deployment of large-scale rechargeable batteries supplying electricity to power grids is imperative, which requires widespread commercialization of high-performance and safe batteries at a low price relying on abundant and ubiquitous source materials and a cost-efficient manufacturing process. Along this line, the trend of the battery research field is currently located at a turning point: “from Li–ion to Na–ion” and “from liquid to solid electrolyte.” From the viewpoints of the distinguished oxide solid electrolyte, Na superionic conductor (NASICON), and the long-standing progress in ceramic processing, Na–ion all-solid-state batteries (Na-ASSBs) based on NASICON and its derivatives show great promise to realize an innovative and sustainable society in the future. At this moment, however, Na-ASSBs face multifaceted and formidable challenges to overcome for practical usage, mostly relating to interfacial matters in terms of interparticle and interlayer contacts. Here, we overview the recent research progress in NASICON-based solid electrolytes (SEs) from the aspects of synthetic techniques and sintering aids, particularly focusing on the tape-casting process and glass additive. We also provide insights into how to prepare electrode layers and incorporate them with an SE layer into an ASSB cell via tape casting, with the prospect of a high-capacity multilayer-stacked ASSB analogous to the multilayer ceramic capacitors (MLCCs). In addition, the feasibility of a Na metal anode in conjunction with the NASICON-type SEs and the tape-casting process toward an MLCC-type cell configuration is discussed. In the last section, we propose our ideas about future research directions in relevant fields to achieve a breakthrough for Na-ASSBs based on NASICON.

CiNii Research

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： https://doi.org/10.1016/j.jssc.2023.124026

出版者・発行元：Journal of Solid State Chemistry  

The bonding nature of hydroxide ions in two proton-conducting oxy-hydroxides, perovskite-type Ba(Zn0.4Ta0.6)O2.9−y(OH)2y (BZT) and double perovskite-type Ba(Zn0.55W0.45)O2.9−y(OH)2y (BZW), has been studied by Fourier transform infrared spectroscopy (FT-IR) at temperatures of 40–600 ​°C. A broad absorption peak at 2500−4000 ​cm−1 attributable to O–H stretching vibration was analyzed by deconvolution into four components, assigned as two symmetric (SC) and two asymmetric (AC) proton sites in the crystal lattice. The temperature variations of peak intensities revealed a difference in proton site preference between BZT and BZW, suggesting a crucial role of B-site cationic order in the proton distribution and, thereby, the proton conductive property.

DOI： 10.1016/j.jssc.2023.124026

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出版者・発行元：ACS Applied Energy Materials  

Impacts of an electrode active material with 1 μm scale thickness on the performance of an oxide-based all-solid-state battery (ASSB) have been investigated by metallic Na | Na3Zr2(SiO4)2(PO4) (NZSP) | Na3Ti2(PO4)3 (NTP) cells. Dense crystalline NTP layer is formed on NZSP ceramic electrolyte using spin coating of glass powder suspension and subsequent crystallization (glass-ceramic process). A sample with 0.6 μm thick NTP layer exhibits 0.1 C charge/discharge cycling with very small polarization (<0.03 V), and its initial capacity of ∼60 mA h g-1 is retained >80% after 60 cycles. Fast cathode kinetics also realized the 0.1 C capacity at −20 °C to be ∼80% retention. Furthermore, a facile control over the thickness of cathode films without any conductive additives in the 1 μm range demonstrated in this work enables the assessment of cathode kinetics. Electrochemical impedance spectroscopy revealed that Warburg resistance originates from an ambipolar diffusion of an electron and Na+ ion. The methodology presented here paves a way for rapid examinations of electrode material compatibility and electrode design for next-generation oxide-based ASSBs.

DOI： 10.1021/acsaem.2c03022

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   出版者・発行元：Inorganic Chemistry  

A novel perovskite fluoride, LixCoF3, which has an exceptionally low tolerance factor (0.81), has been synthesized via low-temperature lithium intercalation into a distorted ReO3-type fluoride CoF3using organolithium reagents. Interestingly, this reaction is completed within 15 min at room temperature. Synchrotron X-ray diffractometry and optical second harmonic generation at room temperature have revealed that this compound shows a high-temperature LiNbO3-type structure (space group: R3¯ c) involving Li-Co antisite defects and A-site splitting along the c direction. A-site splitting is consistent with the prediction based on hybrid Hartree-Fock density functional theory calculations. Co-L2,3edge X-ray absorption spectroscopy, as well as bond valence sum analysis, has verified the divalent oxidation state of Co ions in the lithiated phase, suggesting that its composition is close to LiCoF3(x ≈ 1). This compound exhibits a paramagnetic-to-antiferromagnetic transition at 36 K on cooling, accompanied by weak ferromagnetic ordering. The synthetic route based on low-temperature lithiation of metal fluorides host paves the way for obtaining a new LiNbO3-type fluoride family.

DOI： 10.1021/acs.inorgchem.2c01439

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PubMed

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： https://doi.org/10.1021/acs.inorgchem.2c01439

出版者・発行元：Chemistry of Materials  

The ability to reproducibly synthesize highly conductive solid electrolytes (SEs) is a prerequisite for the widespread usage of solid-state batteries. However, reported ionic conductivities of SEs exhibit significant variation even in materials with the same nominal composition. In this study, the thermodynamic origin of such sample-dependent variations is discussed using sodium-ion conducting Na3SbS4 as a model SE. The impact of uncontrolled variations in elemental chemical potentials on the ionic conductivity is investigated with theory and experiments. The elemental chemical potentials are uniquely defined when the system is constrained to have zero thermodynamic degrees of freedom. First, we establish the relationship between the chemical potentials and sodium-ion conductivity in Na3SbS4 by computing the phase diagram and native defect formation energies. From these calculations, we identify two distinct three-phase equilibrium regions (zero degrees of freedom) with the highest ratio of sodium-ion conductivity, which are then experimentally probed. Transport measurements reveal an abrupt change in the bulk ion transport of the phase-pure samples, with a room-temperature ionic conductivity of 0.16-1.2 mS cm-1 with a standard deviation of 50% when the elemental chemical potentials are not controlled, that is, not uniquely defined. In contrast, we show that by controlling the chemical potentials and therefore, the defect formation energies through the experimental concept of phase boundary mapping, the sample-dependent variation is reduced to 15% with a high average ionic conductivity of 0.94 mS cm-1. This study highlights the existence of "hidden"thermodynamic states defined by their chemical potentials and the need to precisely control these states to achieve reproducibly high ionic conductivity.

DOI： 10.1021/acs.chemmater.2c00944

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： https://doi.org/10.1021/acs.chemmater.2c00944

記述言語：英語   出版者・発行元：Inorganic Chemistry  

Narrow-gap semiconductors with visible light absorption capability have attracted attention as photofunctional materials. H--doped BaSn0.7Y0.3O3-δcontaining Sn(II) species was recently reported to absorb visible light up to 600 nm, which represents the first demonstration of oxyhydride-based visible-light-absorbers. In the present study, a more detailed investigation was made to obtain information on the synthesis and properties of H--doped perovskite-type stannate with respect to the A-site cation of the material and the preparation conditions. H--doped ASn0.7Y0.3O3-δ(A = Ba, Ba0.5Sr0.5, and Sr) obtained by the reaction of ASn0.7Y0.3O3-δprecursors with CaH2at 773 K under vacuum conditions was shown to have almost the same bandgap (ca. 2.1 eV), regardless of the A-site cation. Physicochemical measurements and theoretical calculations revealed that the identical bandgaps of H--doped ASn0.7Y0.3O3-δare due to the simultaneous shift of the midgap states composed of Sn2+with the conduction band minimum. Experimental results also indicated that the appropriate preparation conditions with respect to Y3+-substitution and the temperature for the synthesis of the ASn0.7Y0.3O3-δprecursors were essential to obtain H--doped products that have a low density of defects.

DOI： 10.1021/acs.inorgchem.2c00398

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PubMed

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： https://doi.org/10.1007/s10971-022-05843-8

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： https://doi.org/10.1016/j.ceramint.2022.05.125

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： https://doi.org/10.1021/acs.inorgchem.2c00398

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： https://doi.org/10.1016/j.scriptamat.2021.113887

出版者・発行元：Journal of Solid State Chemistry  

Proton-conductive behaviors of oxy-hydroxide perovskites Ba(ZnxNb1−x)O3−δ−y(OH)2y (BZN) were investigated by Fourier transform infrared spectroscopy (FT-IR) at 40–600 ​°C. The in-situ FT-IR analysis upon heating in flowing N2 gas revealed a broad IR peak at about 2500–3700 ​cm−1, attributed to O–H stretching vibration modes. The broadened IR peak was deconvoluted with four Gaussian components, and their relative intensities are dependent on temperature, indicating the presence of site preference of protons in the BZN crystal lattice. The proton site preference in BZN was discussed based on the comparison of spectral features between BZN and Ba(Zr0.9Y0.1)O2.95 as a reference.

DOI： 10.1016/j.jssc.2022.122913

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： https://doi.org/10.1016/j.jssc.2022.122913

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： https://doi.org/10.1016/j.jssc.2022.122913

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： https://doi.org/10.1103/PhysRevLett.127.215701

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1021/acs.chemmater.1c00460

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1007/s10971-020-05236-9

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.electacta.2019.03.057

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.nanoen.2018.04.074

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.electacta.2018.05.020

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.nanoen.2018.04.074

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1021/acs.inorgchem.8b00381

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： DOI: 10.1016/j.electacta.2017.05.100

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： DOI: 10.1039/C7CE01123G

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： doi.org/10.1016/j.ultsonch.2016.04.033

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： DOI: 10.1016/j.apt.2016.12.014

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.matlet.2016.10.054

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

DOI： http://doi.org/10.4164/sptj.53.804

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.electacta.2016.09.113

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： DOI: 10.1039/C6CP00515B

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： doi:10.1016/j.electacta.2015.09.153

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： doi:10.1016/j.ceramint.2014.12.137

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： DOI: 10.1016/j.ssi.2014.09.003

記述言語：日本語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

The concentration of peroxide (O₂^2-) ions in the cage structures of the mayenite (12CaO·7Al₂O₃ or C ₁₂A₇) crystal lattice has been determined quantitatively by Raman spectroscopy combined with volumetry and electron paramagnetic spin resonance. The formation process of the O₂^2- ion was also investigated using in situ Raman spectroscopy under controlled atmospheres. Although room temperature Raman spectroscopy showed that the equilibrium concentration of O₂^2- ions in the cage structures increased with increased annealing temperatures (especially below 800 °C), no O₂^2- signal was observed at very high temperatures (1350 °C) during the in situ measurements. We explain this apparent inconsistency by hypothesizing that transient atomic oxygen, possibly originating from the thermal dissociation of atmospheric O₂, is formed at interstitial or cage sites within C₁₂A₇ at high temperatures and subsequently combines with O^2- ions in the cages to form O₂^2- during the cooling process.

DOI： 10.1039/c3ra42521e

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.7567/APEX.6.015802

記述言語：英語   掲載種別：研究論文（学術雑誌）  

An extended volumetric method, combined with quadrupole mass spectroscopy (QMS), is proposed. This method enables us to distinguish and simultaneously quantify hydride (H ^-) ions and electrons (e ^-) incorporated in cages of 12CaO·7Al ₂O ₃ (C12A7), which is accomplished upon annealing with CaH ₂. When a sample is dissolved in a deuterium chloride solution, most of the H ^- ions and electrons released from cages react to form HD and D ₂ molecules, respectively. These isotope-labeled molecules are then detected by QMS. We have used this method to follow the concentrations of H ^- ions and electrons in C12A7-treated CaH ₂ over the thermal treatment time. We found that during the initial seven days of treatment, both concentrations increased. Thereafter, the electron concentration begins to decrease, while the H ^- ion concentration continues to increase toward the theoretical maximum. This diverging behavior is due to differences in their diffusion ratios and thermodynamic stabilities.

DOI： 10.1021/jp2106742

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1038/nmat3302

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1063/1.3683571

記述言語：英語   掲載種別：研究論文（学術雑誌）  

12CaO·7Al₂O₃ (C12A7, mayenite), which has a nanoscale porous structure that can accommodate extraframework species such as hydride (H^-), oxide (O^2-), hydroxide (OH^-) ions, and electrons, has been doped with H^- ions to investigate its effects as dominant extraframework species. Chemical doping with CaH₂ enables the concentration of H^- ions to reach almost the theoretical maximum. The concentration of H^- ions is characterized by optical absorption intensity ascribed to photoionization of H^- ions, and ¹H magic angle spinning nuclear magnetic resonance (MAS-NMR) spectroscopy. Persistent electron generation, which is accompanied by the formation of an F absorption band and electrical conductivity, by irradiation with ultraviolet light at room temperature increases as the H^- ion doping increases until it reaches half the theoretical maximum and then decreases as the H^- ion concentration increases further. This dependence indicates that both H^- and O^2- ions are necessary for the generation of persistent electrons.

DOI： 10.1016/j.jssc.2011.04.008

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1088/1468-6996/12/3/034303

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1021/jp202428s

記述言語：英語   掲載種別：研究論文（学術雑誌）  

The accurate determination of the concentration of electrons incorporated into cages in 12CaO·7Al₂O₃ (C12A7) has been examined using iodometry. Preliminary experiments confirmed that iodine is reduced in preference to protons by electron-enriched C12A7, even in aqueous solution. The electron concentrations in several C12A7 samples are measured using a procedure where the iodine molecules in an I₂-HCl solution are partially reduced by electrons released from the samples, followed by titration of the residual iodine molecules. The accuracy of this procedure is confirmed by the excellent agreement of the results with those from thermogravimetric analysis. The reevaluated maximum electron mobility is nearly twice as high as that reported previously, and the critical electron concentration for the metal-insulator transition is revised slightly because of the accuracy of the iodometry results.

DOI： 10.1021/jp1054364

記述言語：英語   掲載種別：研究論文（学術雑誌）  

We examined the electric field-assisted thermionic emission of atomic oxygen radical anion (O^-) in a vacuum from fluorine-substituted derivatives of 12CaO·7Al₂O₃ (C12A7) with a composition of (12 - x)CaO·7Al₂O₃·xCaF₂ (0 ≤ x ≤ 0.8). Unsubstituted C12A7 easily decomposed into 5CaO{bullet operator}3Al₂O₃ (C5A3) and 3CaO{bullet operator}Al₂O₃ (C3A) above 830 °C during the emission experiment in a vacuum. The decomposition temperature range became narrower as the amount of F^- ion substitution increased, e.g. the sample with x = 0.4 kept a single phase after the emission experiment at 900 °C. The emitted anionic species from the x = 0.4 sample were dominated by O^- ions (∼ 92%) together with a small amount of O₂^- ions (∼ 4%) and F^- ions (∼ 4%). The absence of an O₂ gas supply to the opposite side of the emission surface led to a nearly steady co-emission of O^- ions and electrons with a ratio of < 1/1. The O₂ gas supply markedly enhanced the O^- ion emission, and suppressed the electron emission. A sustainable and high-purity O^- ion emission with a current density of 11 nA cm^{- 2} was achieved at 830 °C with the supply of 40 Pa O₂ gas. The similarity in these emission features to the unsubstituted C12A7, together with the improved thermal stability demonstrates that the F^- ion-substituted C12A7 is a promising material for higher intensity O^- ion emission at higher temperatures.

DOI： 10.1016/j.ssi.2009.04.018

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1021/jp902159p

記述言語：英語   掲載種別：研究論文（学術雑誌）  

12CaO·7Al₂O₃ (C12A7) with a unique nano-porous structure and free O^2- ions entrapped in sub-nanometer-sized cages is a fast oxygen-ion-conducting material. These free O^2- may be replaced by various oxygen-related species, OH^-, O^2- and O^-, by tuning the atmosphere during the heat treatment. We examined the conduction mechanism for stoichiometric C12A7 (C12A7:O^2-), in which O^2- ions exist as counter anions in sub-nanometer-sized cages, by Raman measurement of C12A7:O^2- annealed in a dry ¹⁸O₂ atmosphere. It was revealed that the primary ion conducting species is an O^2- ion which diffuses via exchange with O^2- in the cage wall. An experimental result on the sample containing O^- ions implied that O^- is more mobile than O^2- in C12A7. Ab initio calculations on the diffusion paths of O^2- and O^- ions in C12A7 supported the above experimental results.

DOI： 10.1016/j.ssi.2008.10.015

記述言語：英語   掲載種別：研究論文（学術雑誌）  

The effect of humidity on the electrical conductivity in porous and dense ceramics of Ca12 Al14-x Six O32 Cl2+x (x=0, 1.7, 3.4) with a mayenite structure was examined at room temperature. Surface ionic conductivity was enhanced by increasing the humidity. The sample with x=3.4, which had a porosity of 30%, exhibited the largest conductivity change of about 4 orders of magnitude over the relative humidity range of 10-90% at 25°C. The presence of Cl- ions on the surface most likely enhances the formation of hydronium ions which are responsible for proton transfer in physisorbed water layers.

DOI： 10.1149/1.3032908

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1149/1.2999055

記述言語：英語   掲載種別：研究論文（学術雑誌）  

A new synthetic route via a solid-state reaction, the crystal structure of 12SrO·Al₂O₃ (S₁₂A₇) incorporated with OH^- ions, and the formation of oxygen radical anions in S₁₂A₇ have been examined. Investigations using X-ray powder diffraction and thermogravimetric and evolved gas combined analyses demonstrate that homogenization promoted by molten Sr(OH)₂ hydrates and the presence of Sr-hydrogarnet precursors play crucial roles in the formation of S₁₂A₇. Rietveld analyses confirm the lattice framework of S₁₂A₇ has a structure identical to that of the nanoporous crystal 12CaO·7Al₂O₃ (C ₁₂A₇, a mayenite structure) and demonstrate that two Sr²⁺ ions (pole Sr²⁺ ions) on the S₄ axis of a cage displace toward the cage center owing to the accommodation of an OH ^- ion. An electron paramagnetic resonance study demonstrates that oxygen radical anions, O₂ ^- and O^-, are generated in the cages with concentrations on the order of 10²⁰ cm^-3 each by oxygen annealing. From the g-values observed at 77 K, the oxygen radical anions are interpreted as being sandwiched between the two pole Sr²⁺ ions rather than adsorbed on one side.

DOI： 10.1021/cm800666p

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Electron-doped 12CaO · 7Al ₂O ₃ (C12A7) nanowires (NWs) were fabricated by two approaches. First, spatially selective electron doping of C12A7 films was examined by using a chemical method specific to C12A7. However, the conductive NW was not formed due to diffusion of oxygen in the C12A7 films to the conductive area. Secondly, a combination of dry etching and electron doping was examined. NWs with conductivities ∼6 S/cm at 300 K were successfully fabricated by this method. The temperature dependence of the conductivity in the NWs exhibited almost degenerated conduction down to 5 K.

DOI： 10.1002/pssa.200778901

記述言語：英語   掲載種別：研究論文（学術雑誌）  

12CaO · 7Al ₂O ₃ (C12A7) electride, which is synthesized by replacing free oxygen ions in cages with electron anions, has distinct advantages over electrides reported so far in respect of thermal and chemical stability and flexible preparation of various sample forms including single crystal, thin film, polycrystalline bulk and powder. These advantages, together with the fact that the concentration of the electron anions is controlled in a wide range according to a synthetic process, make the C12A7 electride attract growing attentions from both scientific and practical points of views. This paper reviews several chemical and physical synthetic processes of the C12A7 electride including thermal treatment of C12A7 under metal vapor and reducing gas atmospheres, hot Ar ⁺ ion implantation, solidification of the strongly reduced C12A7 melt, and crystallization of the reduced glass in vacuum. Each process, having its own suitability for a specific form of the electride, has unique advantages such as a completeness of anion replacement, mass production capability and controllability of the electron-doped area. Electronic and optical properties of the resulting electrides prepared by the different process are briefly discussed in terms of the feature of the processes.

DOI： 10.1007/s10854-007-9183-y

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Nanoporous oxide 12CaO·7Al₂O₃ (C12A7) is a fast oxide-ion conductor that may encage various types of anionic oxygen species such as O^2-, O₂ ^-, O₂ ^2-, and O^- in its crystallographic cages. The C12A7 single crystals thermally annealed in ¹⁸O₂ were examined by micro-Raman spectroscopy. The symmetric properties and the origin of Raman bands were analyzed by the isotope shift and the depolarization on the bases of the crystal symmetry of C12A7, and the Raman band due to the stretching mode of extraframework O₂ ^2- was identified. Spatially resolved measurements of the isotope shift of the Raman bands in a partially ¹⁸O-substituted sample indicated that the local fraction of ¹⁸O is equal between the framework and extraframework sites, demonstrating that the substitution of O^2- ions in the C12A7 framework is as fast as the formation of extraframework oxygen species by thermal oxygen loading. It strongly suggests that the extraframework oxygen species diffuse by replacing oxygens in the framework sites, rather than simply permeating through intercage openings.

DOI： 10.1021/jp074248n

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Effects of O ^2- or OH ^- ion incorporation on the cage geometry in 12CaO·7Al ₂O ₃ (C12A7) crystals are examined by the maximum entropy method (MEM)/Rietveld analyses of synchrotron powder X-ray diffraction data. Presence of an extraframework anion in a cage causes inward displacements of two Ca ²⁺ ions axially coordinating to the anion. The OHion locates at the cage center and induces smaller symmetric displacements of the two Ca ²⁺ ions, while the O ^2- ion likely locates on off-axis positions and induces larger asymmetric Ca ²⁺ ion displacements.

DOI： 10.1246/cl.2007.902

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1021/nl062717b

記述言語：英語   掲載種別：研究論文（学術雑誌）  

This article reviews our approach to render 12CaO·7Al ₂O₃ (C12A7) electronically active using a new concept of 'active anion manipulation', where nanostructures embedded within the C12A7 crystal lattice are intentionally utilized to generate chemically unstable ('water-free active') anions. Anionic active oxygen radicals, O^- and O ₂ ^- , are formed efficiently in C12A7 cages under high oxygen activity conditions. The configuration and dynamics of O ₂ ^- in cages are revealed by a combination of continuous-wave and pulsed electron paramagnetic resonance (EPR). It is demonstrated that metal-loaded C12A7 is a promising oxidation catalyst for syngas (CO + H ₂) formation from methane. Furthermore, the O^- ion, the strongest oxidant among active oxygen species, can be extracted from the cage into an external vacuum by applying an electric field with thermal assistance, generating a high-density O^- beam in the order of μA cm ^-2. In contrast, heat treatment of C12A7 in a hydrogen atmosphere forms H^- ions in the cages. The resultant C12A7:H^- exhibits a persistent insulator-conductor conversion upon ultraviolet-light or electron-beam irradiation. The irradiation-induced conversion mechanism is examined by first-principle theoretical calculations. Furthermore, the presence of a severely reducing environment causes the complete substitution of electrons for anions in the cages. The resulting C12A7:e^-, which exhibits excellent stability and an electrical conductivity greater than 100 S cm ^-1, is regarded as an 'electride', an ionic compound in which electrons serve as anions. The C12A7 electride exhibits a high potential for applications involving cold cathode and thermal field electron emissions due to its small work function. Electride fabrication methods suitable for large-scale production via melt processing are described. It is also demonstrated that proton or inert gas ion implantations into C12A7 thin films at elevated temperatures are effective for both H^- and electron doping.

DOI： 10.1007/s10853-006-1316-9

記述言語：英語   掲載種別：研究論文（学術雑誌）  

A cage structure formed in a positively charged lattice framework of 12CaO-7Al₂O₃ (C12A7) is utilized to incorporate and release chemically unstable anions, imparting chemical and electronic activities to this material. High concentrations of oxygen radical anions, i.e. O ^- and O₂
^-, are formed efficiently in these cages under a high oxygen activity condition. The O^-ion, which is the strongest oxidant among all the reactive oxygen species, can be extracted from the cages into an external vacuum by applying an electric field with thermal assistance. In contrast, hydrogen-reduction processes allow the formation of hydride (H^-) ions in the cage. H^- ion-incorporated C12A7 exhibits a persistent insulator-conductor conversion upon irradiation with ultraviolet-light or electron-beam. The irradiation-induced conversion mechanism and electronic transport characteristics are discussed on the basis of experimental evidence and first-principle theoretical calculations. Electrons released from the H^- ions are trapped by the cages and subsequent inter-cage hopping of the electrons is responsible for the electrical conduction. Furthermore, a severe reducing environment enables us to substitute electrons almost completely for anions in the cages, forming a stable inorganic electride. Finally, the formation of these active anions in this material is examined in terms of electronic structures, thermodynamics, and structural features of the cage.

DOI： 10.1246/bcsj.80.872

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Electron carriers were generated in refractory oxide 12CaO·7Al ₂O₃ (C12A7) through a thermal treatment in a reducing CO/CO₂ atmosphere, and the reduction process was thermodynamically analyzed. Electrical-conductive C12A7, which had an electron concentration of ∼8 × 10¹⁹ cm^-3 and an electrical conductivity of ∼4 S/cm at 300 K, was obtained by extracting free O^2- ions in sub-nanometer-sized cages in the C12A7 lattice and leaving electrons behind. The enthalpy for this substitutive reaction is +425 kJ/mol, suggesting that stoichiometric C12A7 is more stable in air than the C12A7 electride.

DOI： 10.1111/j.1551-2916.2006.01213.x

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Single crystals of nanoporous 12CaO·7Al₂O₃ (C12A7) as large as 27 mm in diameter, 120 mm in length, and 207 g in weight have been successfully grown by the Czochralski method. We found that a 2.0% oxygen-containing nitrogen atmosphere and an iridium crucible are the critical factors for success. The crystal ingot exhibited an orange color resulting from the incorporation of Ir⁴⁺ ions of ca. 5 × 10¹⁷ cm^-3, which presumably occupy Ca²⁺ sites. X-ray diffraction analysis indicated that the ingot obtatined was a single crystal with few domains.

DOI： 10.1021/cg0600290

記述言語：英語   掲載種別：研究論文（学術雑誌）  

A room temperature (RT) stable electride was realized by thermally annealing an insulating 12CaO·TAl₂O₃ (C12A7) single crystal in a calcium metal vapor. Here we report a simple and direct method for synthesizing polycrystalline C12A7 electride (C12A7:e^-); the solidification of a "melt" in a reducing atmosphere and the crystallization of a "glass" with an oxygen-deficient composition in a vacuum. The carbon-related anion (C₂
^2-) presumably serves as the template for the formation of the C12A7 phase in the solidification process and may be spontaneously released from the lattice during the cooling process, leaving mobile electrons in the lattice. Also the C₂ ² ions accommodated in the glass may play a significant role in the formation of C12A7:e^- during the crystallization. The polycrystalline C12A7:e^- exhibits an electrical conductivity up to 5 S·cm^-1 at 300 K, which corresponds to an electron concentration of ∼3 × 10¹⁹ cm^-3 and a nearly equal mobility of ∼0.1 cm²·W^-1·s ^-1 to that of the single crystalline C12A7:e^-. A large current density of ∼12 μA·cm^-2 is obtained in the electron field emission from a flat surface of the polycrystalline C12A7:e ^- with a work function of ∼0.6 eV for an applied electric field of 2.4 × 105 V·cm^-1. These simple synthetic methods make it possible to produce efficiently the electride in large volume, which will facilitate the C12A7:e^- research, paving a way for various applications including cold electron emission.

DOI： 10.1021/cm052367e

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1103/PhysRevB.73.014101

記述言語：英語   掲載種別：研究論文（学術雑誌）  

In this work we investigate a variety of chemical and photoinduced processes in which different hydrogenous species including H2 molecules, H- ions, and H0 atoms interact with the bulk of a complex nanoporous oxide 12CaO·7 Al2 O3. Our results provide a detailed and consistent explanation of the recently observed phenomenon of photoinduced conversion of the insulating H-doped 12CaO·7 Al2 O3 to a conductor [K. Hayashi, Nature (London) 419, 462 (2002)]. The formation of a large and thermally stable concentration of electron centers in this process is facilitated by a large concentration (up to 1020 cm-3) of extraframework O2- naturally present in this material and homogeneously distributed in its bulk. We show that these species are able to split H2 molecules into pairs of H+ and H- ions and convert H0 atoms into H+ and e- promoting the photoinduced conversion process. The similarity of the mechanisms described in this work to those known for low-coordinated sites at MgO surfaces indicates that the formation of electronic centers in oxides interacting with hydrogenous species could be a generic feature.

DOI： 10.1103/PhysRevB.73.045120

記述言語：英語   掲載種別：研究論文（学術雑誌）  

12CaO·Al₂O₃ (C12A7) has a unique crystal structure composed of positively charged cages ∼0.4 nm in inner diameter and a free oxygen ion (O^2-) clathrated in one-sixth of the cages. C12A7 can be converted to inorganic electride by replacing the clathrated oxygen ions with electrons, and the electride exhibits degenerate-type conduction with room-temperature conductivities >100 S cm^-1. In intermediate states, semiconductive C12A7 can be obtained by controlling electron density. In this study, we examined effects of electric field on carrier transport properties of the semiconductive C12A7 using a field-effect transistor (FET) structure targeted for future mesoscopic devices and electrochemical devices that will utilize the quantum-dot-like cage structures and chemically active clathrated anions in C12A7. FETs were fabricated using two types of samples, (i) single-crystalline bulk and (ii) polycrystalline thin films, for channels. First, conditions to form good contacts for source and drain electrodes were examined because the semiconductive C12A7 has a small work function, and it was difficult to form good electrical contacts with metals. It was found that Pt was the best metal with the lowest contact resistance to C12A7, and thermal annealing at ≥300 °C improved its non-ohmic characteristics. Electrical conductivity was modulated by 1-2 orders of magnitude by applying gate voltage. Apparent field-effect mobilities were 0.02-0.08 cm² (V s) ^-1, which were comparable with the drift mobilities of the semiconductive C12A7. This is the first demonstration of a semiconductor device using an electride.

DOI： 10.1021/cm051904s

記述言語：英語   掲載種別：研究論文（学術雑誌）  

The crystalline framework of a complex oxide 12CaO•7Al ₂O ₃ (C12A7) is built from positively charged sub-nanometer cages able to trap electrons. An embedded cluster approach is used to study the electronic structure and optical properties of electron-containing C12A7 for different concentration of extra-framework electrons. Our results suggest that the conduction band of the C12A7 consists of a relatively narrow band of empty cage states (cage conduction band) with one-electron energies between 5.5 and 6.1 eV above the top of the valence band (VB), and a framework conduction band at about 6.7 - 7.0 eV above the to of the VB. The gap between the cage conduction band and the framework conduction band is estimated to be about 1 - 1.5 eV. The energies of the lowest optical transitions from the top of the valence band to the cage conduction band are predicted to be at 5.2 - 5.5 eV. The extra-electrons occupy cage states, which split from the cage conduction band to about 4 eV above the top of the VB. The extra-framework electrons introduce two absorption bands with the experimental peaks at 0.4 eV and 2.8 eV. These bands are assigned to the inter-cage charge transfer and the intra-cage s-p transitions respectively. The changes in the optical absorption spectra as a function of the extra-electrons concentration are also discussed.

DOI： 10.1016/j.msec.2005.06.047

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1063/1.2149989

記述言語：英語   掲載種別：研究論文（学術雑誌）  

The 12CaO·7Al₂0₃ (C12A7) crystal with a nanoporous lattice framework exhibits high electrical conductivity with an activation energy of ∼ 1.5 eV when equilibrated in a hydrogen atmosphere above ∼800°C. The high conductivity is preserved in a quenched state below ∼600°C with a reduced activation energy of ∼0.8 eV, Such complex behavior in electrical conductivity is associated with incorporation of hydride ions (H^-) in cages of the lattice framework. Electromotive force measurements reveal that the major carrier for the conductivity is electron with a small contribution by proton (H⁺), ruling out the possibility of direct intercage migration of the H^- ion. A combination of these observations with the ab initio calculations leads to the conclusion that the electrons are thermally generated from the H^- ion by the dissociation into two electrons and an proton, which is further converted to an OH^- ion via reaction with an extraframework oxide ion (0^2-). The energy difference between the initial (H^- + O^2-) and the final (2e^- + OH^-) states as evaluated by the theoretical calculation is as small as ∼1 eV, which agrees well with an experimentally obtained enthalpy change, ∼1.4 eV. Thus, internal equilibration between the extraframework hydrogen and the oxygen species is responsible for the thermal generation of the carrier electron. It is also suggested that the same conductive (2e^- + OH^-) state is reached by the photoirradiation of H^--containing C12A7. In this case the photoionization of H^- forms an electron and an H ^o atom, which then forms an OH^- ion and another electron with thermal assistance. The persistence of photoinduced conductivity is explained by the slow kinetics of the reverse process at room temperature.

DOI： 10.1021/jp053990p

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1021/ja053568m

記述言語：英語   掲載種別：研究論文（学術雑誌）  

We have examined the thermodynamics and kinetics of hydroxide (OH) ions that formed in cages of 12CaO·7Al ₂O ₃ (C12A7) with nanoporous structures. It is confirmed using thermogravimetric-evolved gas analyses (TG-EGA) that hydration in C12A7 is mediated by a reaction between an oxide (O ^2-) ion in the cage and an H ₂O molecule in the atmosphere to form two OH ^- ions in the cages. To simply and exactly quantify the OH ^- content from infrared absorption measurements of OH-stretching band, we propose a method combined with a thermodynamic analysis, allowing the simultaneous determination of the molar extinction coefficient of the OH-band, enthalpy, and entropy for the hydration. Hydration enthalpy in C12A7 is extremely high compared with other oxides and was enhanced by the marked instability of O ^2- ion in the cage. Consequently, high solubility of OH ^- ion is retained up to unusually high temperatures. Furthermore, we determined diffusion coefficients of species relevant to the hydration process and demonstrated that inward diffusion of OH ^- ions is the rate-determining process.

DOI： 10.1021/jp050807j

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Oxygen radial (O2^-, O^-)-accommodated 12CaO·7Al₂O₃ (CI2A7) releases oxygen molecules at about 800 C when heated in helium. The corresponding weight loss nearly accords with that calculated from an amount of the accommodated radicals, providing solid evidence that they are formed by an oxygen gas uptake from the atmosphere. Small difference between the observed and calculated losses suggests the presence of peroxide ion, O₂
^2-, which is confirmed by the enhancement of 770 cm^-1 band in Raman spectra of the radical-accommodated samples.

DOI： 10.1246/cl.2005.586

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1007/s10853-005-6505-4

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1021/ja043990n

記述言語：英語   掲載種別：研究論文（学術雑誌）  

We suggest, on the basis of detailed ab initio calculations of both ground and photoexcited states of H-doped 12CaO·7 Al2 O3 (C12A7:H), that stable high-conductivity regions can be optically generated in this insulating system. Each H- ion in C12A7:H can, under photoirradiation at 3.8-4.5 eV, produce up to two electrons and a proton that binds to the lattice network and forms OH-. Mobile electrons play a role of anions in this system. They move over subnanosized cages of the C12A7 lattice via polaron hopping. The insulating state is reversibly restored upon heating to 300 °C.

DOI： 10.1063/1.1871359

記述言語：英語   掲載種別：研究論文（学術雑誌）  

We report formation of persistent carrier electrons in hydride ion (H-) -incorporated 12CaO·7Al2O3 (C12A7) by electron-beam irradiation. The electrical conductivity of H- -doped C12A7 single crystals increases with the electron-beam irradiation dose, accompanied with a green coloration attributable to a carrier electron formation. A 25 keV electron beam with a dose of ~500 μC cm-2 fully converts the conductivity in surface layers to the depth of ~4 μm. Carrier electron formation is most likely due to electron-hole pairs generated in the electron excitation volume and subsequent energy transfer to the H- ions. The estimated carrier formation yield per an incident electron is ~30. These findings may enable a fine patterning of the conductive area without photomasks and photoresists.

DOI： 10.1063/1.1852723

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1063/1.1829151

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.apcata.2004.09.030

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1021/jp046963s

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.ssi.2004.07.057

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.jphotochem.2004.04.033

記述言語：英語   掲載種別：研究論文（学術雑誌）  

The thermodynamics and kinetics of oxygen radical formation in cages of a nanoporous crystal, 12CaO·7Al₂O₃, were examined during isothermal annealing in a dry oxygen atmosphere. The formation of oxygen radicals, O₂
^- and O^-, involves the outward diffusion of extraframework oxide ions, their oxidation by absorbed oxygen molecules to form O^- and O₂
^- at the surface, and subsequent inward diffusion of the oxygen radicals. The instability of the extraframework oxide ions provides the driving force for this process. Evaluating the radical formation enthalpy and entropy enabled us to determine the temperature and oxygen partial pressure dependences of equilibrium oxygen radical concentration. The rate-limiting process for the radical formation is not the surface reaction, but the total ionic diffusion process, in which the smaller diffusivity of O₂
^- likely dominates the process.

DOI： 10.1021/jp037916n

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.mee.2004.03.003

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1111/j.1551-2916.2004.01153.x

記述言語：英語   掲載種別：研究論文（学術雑誌）  

A new method to convert 12CaO·7Al₂O₃ (C12A7) thin films to electronic conductor by hot Ar⁺ ion implantation has been developed and its mechanism is discussed. It was found that hot Ar ⁺ ion implantation extruded free O^2- ions in C12A7 films by kick-out effects at fluences higher than 1×10¹⁷ cm ^-2, which left electrons in the cages embedded in C12A7 crystal and produced high concentration F⁺-like centers (∼1.4×10 ²¹ cm^-3). The resulting films show coloration and persistent electronic conduction with conductivities up to ∼1 Scm ^-1. On the other hand, fluences less than 1×10¹⁷ cm^-2 kept the films transparent and insulating.

記述言語：英語   掲載種別：研究論文（学術雑誌）  

The formation and desorption mechanisms of oxygen species in nanoporous crystal 12CaO· 7Al₂O₃ (C₁₂A ₇) are studied by temperature-programmed desorption (TPD), electron-spin resonance (ESR), and Raman spectroscopy. Various oxygen ion species, including O^-, O₂^-, and O ₂^2-, are observed to exist in C₁₂A₇ at high concentrations (∼10²⁰ cm^-3). The desorption of these oxygen species in C₁₂A₇ is proposed to proceed in three steps: (1) diffusion of oxygen species from bulk to the surface (rate-limiting step), (2) decomposition of oxygen species into oxygen molecules, and (3) release of molecular oxygen into the gas phase. Oxygen species in C₁₂A₇ can be regenerated by heating in an O₂ atmosphere at higher than 400 °C, and the concentrations of O^- and O₂^- increase with temperature. More O₂ ^- is formed than O^- at low activation temperatures, whereas nearly equal amounts of O^- and O₂^- are formed at high temperatures around 1350 °C. At 400-700 °C, a considerable amount of molecular oxygen, O₂, is suggested to be present together with other oxygen species. The formation of oxygen ion species occurs in a manner reverse to the desorption processes, with the first step involving diffusion of oxygen from the atmosphere into nanocages of C ₁₂A₇.

DOI： 10.1021/cm034755r

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Recently it has been discovered that a nano-porous main group oxide 12CaO·7Al₂O₃ (C12A7) can be converted from a wide-gap insulator to a good transparent conductor. Using ab initio modelling we explain good conductivity of this material by very small barriers for hopping of localised electrons between neighbouring positive cages. We show that optical absorption of C12A7 in infrared region and at energies higher than 2.7 eV is due to inter-cage and intra-cage electron transitions, respectively. The proposed mechanisms can be useful in further search for conducting transparent media.

DOI： 10.1016/S0040-6090(03)01156-8

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Thin film fabrication of crystalline 12CaO·7Al₂O ₃ (C12A7) with zeolitic structure was examined, and their electrical and optical properties were measured. Polycrystalline thin films were prepared by post-annealing of amorphous films in oxygen atmosphere at temperatures above 800 °C. Choice of substrates was crucial for obtaining single-phase thin films. Although various oxide substrates (single crystals of Al ₂O₃, Y-stabilized ZrO₂, MgO and silica glass) were examined, single-phase films were obtained only for MgO substrates and the other substrates reacted with the CaO component in the films during post-annealing. The optical band gap of C12A7 was evaluated to be 5.9 eV. Hydride ions were incorporated into the film by a thermal treatment in a hydrogen atmosphere at 1200 °C. The resulting transparent thin films were converted into transparent persistent electronic conductors exhibiting an electrical conductivity 6.2×10^-1 Scm^-1 at 300 K by ultraviolet light illumination. This is the first example of transparent conductive thin film in which conductive areas can be patterned directly by light.

DOI： 10.1016/S0040-6090(03)01170-2

記述言語：英語   掲載種別：研究論文（学術雑誌）  

A method to obtain a polycrystalline thin film, where an amorphous C12A7 film was first deposited was developed. The effects of hydrogenation using thermal treatment in H₂ atmosphere or proton implantation were investigated. The results indicated that the H-loaded C12A7 films provide a unique capability to realize semi-transparent electric circuits directly patterned by UV-light irradiation.

DOI： 10.1002/adma.200304925

記述言語：英語   掲載種別：研究論文（学術雑誌）  

12CaO·7Al₂O₃ (C12A7) crystal is an interesting material where a large amount of O^-(c) and O₂^-(c) can be formed and trapped in the cages when it is sintered in dry oxygen. The emissive features of this material including the emission species, temperature dependence, field dependence, emission branch ratio, emission stability, the effects of water on the emission intensity, have been investigated. The temperature and oxygen pressure dependences of the electrical conductivity have also been measured. The mechanisms of the O^- emission have been discussed based on the investigations of the emission and electrical conductivity features.

DOI： 10.1016/S0039-6028(02)02575-X

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1103/PhysRevLett.91.126401

記述言語：英語   掲載種別：研究論文（学術雑誌）  

We report the first electronic conduction in main group metal oxides (MGOs) or light-metal oxides, which are represented by alkaline-earth oxides, alumina, and silica. They are believed to be never converted to an electronic conductor. One of the MGOs, 12CaO·7Al₂O₃ (C12A7), has optical transparency, but electrical insulation limits intrinsic form. It is characterized by sub-nanometer sized cages in the lattice framework. Hydride ion, H^- was incorporated into the cage by a thermal treatment of C12A7 single crystals or ceramics in hydrogen atmosphere. The product, C12A7:H, was colorless, transparent and a good insulator having electronic conductivity less than 10^-10 S·cm^-1. We found that the C12A7:H exhibits a coloration of yellowish green corresponding to optical absorptions at 2.8 and 0.4 eV with simultaneous conversion into an electronic conductor with 0.3 S·cm^-1 at 300 K upon a irradiation of ultraviolet light, The conductive state continued even after the irradiation was stopped. Inversion to the insulator occurred when heated more than ∼320°C accompanying with rapid decay of the optical absorptions. When temperature rose above 550°C, H₂ gas was released from the sample and the photosensitivity was lost. We consider that high concentration of F ⁺-like centers are created by photo-released electrons from the H^- anions being captured by empty cages. Further, a migration of the electrons at the F⁺-like centers may be responsible for the conduction. The visible light absorption loss is estimated to be only 1% for a 200 nm thick conductive C12A7:H films. The present properties provides novel applications such as direct optical writing of conducting wires on insulating transparent media.

記述言語：英語   掲載種別：研究論文（学術雑誌）  

We succeeded in extracting intense O^- ion beam by applying dc voltage to a microporous crystal 12CaO·7Al₂O₃ (C12A7) engineered to incorporate extremely large amounts of O^- (1.3 × 10²⁰ cm^-3) and O₂^- (2.7 × 10²⁰ cm^-3) in crystallographic cages. The O^- ion beam is monochromatic and the current density (∼2 μA/cm²) is higher by three orders of magnitude than the maximum value recorded for yttrium-stabilized ZrO₂ (YSZ). A surface metal electrode, essential for the YSZ to dissociate a drifted O^2- in the bulk into an O^- and an electron on the surface, is not needed for the C12A7. The presence of extremely large concentrations of O^- and O₂^- ions and fast oxygen-ion-conductive nature of C12A7 allow extraction of O^- ions directly from the surface.

DOI： 10.1149/1.1498970

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1063/1.1476958

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/S0022-0248(01)02038-3

記述言語：英語   掲載種別：研究論文（学術雑誌）  

We examined the densification of 12CaO · 7Al₂O₃ (C12A7), which has a microporous lattice framework with a cavity of approximately 0.4 nm. Fully densified translucent ceramics are obtained when hydrated C12A7 powders prepared as precursors are sintered in a dry oxygen atmosphere at 1300°C. The average transmittance between 400-800 nm for 1-mm-thick samples is improved up to approximately 70% with a 48-h increase in the sintering time. Dissociation of water molecules at the grain-pore interface into grains which entraps hydroxide ions in the crystallographic cage, and the release of the hydroxide ions into the atmosphere during the sintering procedure are considered to play crucial roles in the pore-annihilation processes.

DOI： 10.1557/JMR.2002.0185

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/S0022-0248(01)01951-0

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Current-voltage (I-V) characteristics across Σ1 boundaries of Nb-doped SrTiO₃ bicrystals were investigated with a special interest in the effect of an impurity ion, cobalt. The Σ1 boundary with cobalt ions was fabricated by hot-joining technique after evaporating metallic cobalt onto the (001) plane used for a contact plane. High-resolution transmission electron microscopy (HREM) study associated with X-ray energy dispersive spectroscopy (EDS) revealed that cobalt solved and distributed around the Σ1 boundary which was perfectly joined without any second films. It was found that the Σ1 boundary with cobalt ions exhibited a nonlinear I-V relationship while the Σ1 boundary without cobalt ions showed a linear I-V relationship. This result indicates that the presence of cobalt itself at the boundary can form a potential barrier irrespective of grain boundary coherency.

DOI： 10.1111/j.1151-2916.2000.tb01423.x

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1080/095008399177165

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1063/1.371140

記述言語：英語   掲載種別：研究論文（学術雑誌）  

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1557/JMR.1998.0469

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記述言語：日本語   会議種別：口頭発表（一般）  

国名：日本国  

耐火酸化物には厳しい熱化学環境下に耐えるという際立った「機能」から、新しい機能材料として展開が期待できる。当初は典型的な耐火物として取り扱われたきた酸化物材料に関連する、講演者が近年取り組んだ二つの研究について紹介する。 （１）12CaO・7Al2O3(C12A7) 化合物中の水素 C12A7は、結晶格子中の籠構造に種々の陰イオンを取り込むことを特徴としており、付随して様々な機能性が示されてきた。元来アルミナセメントの一構成成分として知られていた。例えば、強還元処理によって水素化物(H-)イオンを取り込んだC12A7は、紫外光照射による電子伝導性を発現する。H-イオンの汎用的な評価法はなかなか得難かったが、最近になって、講演者らは一般的な固体NMRに基づく有効な検出評価法を確立することができた。実際この方法論を適用して、アパタイト中に生成させたH-イオンを初めて証明することができた。ゆえに本手法は新材料中のH-イオンを検出法として有効である。 （２）高速ナトリウムイオン伝導性セラミックスによる新型電池 Na-S電池は350℃程度で運転される、高エネルギー密度・高耐久性を特徴とするの定置型蓄電池である。ここでは元来耐火物として認識されていたβ-アルミナを、Na+イオンを透過する電解質として用いている。近年、リチウム-空気電池が次世代蓄電池の候補として注目を浴びている。講演者らはリチウム-空気電池の抱えるいくつかの問題を、β-アルミナのような固体電解質を用いることで解決できると考え、セラミックス保護型の「ナトリウム-空気電池」を提案し検討を行っている。その意義と取り組みについて紹介する。

開催地：秋田市  

開催地：ウェルとばた 福岡県北九州市戸畑区  

開催地：ウェルとばた 福岡県北九州市戸畑区  

開催地：国立京都国際会館  

開催地：京都テルサ  

開催地：京都テルサ  

国名：日本国  

開催地：京都テルサ  

開催地：岡山大学  

開催地：岡山大学  

開催地：関西大学千里山キャンパス100周年記念会館  

開催地：北陸先端科学技術大学院大学  

開催地：北陸先端科学技術大学院大学  

開催地：名古屋工業大学  

開催地：名古屋工業大学  

開催地：名古屋工業大学  

開催地：名古屋工業大学  

開催地：名古屋工業大学  

開催地：名古屋工業大学  

開催地：北九州国際会議場  

開催地：関西セミナーハウス  

開催地：関西セミナーハウス  

開催地：工学院大学新宿キャンパス  

開催地：工学院大学新宿キャンパス  

開催地：北海道大学フロンティア応用科学研究棟  

開催地：北海道大学フロンティア応用科学研究棟  

開催地：北海道大学フロンティア応用科学研究棟  

開催地：北海道大学フロンティア応用科学研究棟  

記述言語：英語  

国名：日本国  

開催地：東京理科大学　葛飾キャンパス　図書館ホール  

開催地：JR 博多シティ会議室 9F 会議室 2  

記述言語：英語  

国名：日本国  

開催地：物質・材料研究機構 並木地区  

開催地：物質・材料研究機構 並木地区  

開催地：物質・材料研究機構 並木地区  

開催地：明治大学 駿河台キャンパス  

開催地：明治大学 駿河台キャンパス  

開催地：明治大学 駿河台キャンパス  

開催地：明治大学 駿河台キャンパス  

開催地：中止(みなし発表)  

開催地：web  

記述言語：日本語  

開催地：web  

開催地：web  

開催地：web  

開催地：web  

開催地：web  

開催地：web  

開催地：web  

記述言語：日本語  

記述言語：日本語   掲載種別：記事・総説・解説・論説等（学術雑誌）  

<p>Recently mixed-anion compounds such as metal oxynitrides have attracted considerable attention in physics, chemistry and materials science. In the present brief review, we describe the structural analyses of the mixed-anion compounds. X-ray and neutron diffractometry is able to refine the crystallographic parameters of the crystalline mixed-anion compounds. Electron-density from X-ray data and neutron-scattering-length-densities from neutron data can give the information on the chemical bonding and structural disordering. Scanning transmission electron microscopy and electron energy-loss spectroscopy allow us to characterize local crystal structures with high spatial resolution. Combination of the information about local structures by X-ray absorption near edge structure and magic angle spinning-nuclear magnetic resonance with those available by the diffraction techniques is effective to tackle the problems peculiar to the mixed anion systems: discrimination of N^3－, O^2－, and F^－, and H^－ and OH^－.</p>

DOI： 10.5940/jcrsj.60.254

記述言語：日本語  

記述言語：日本語   掲載種別：記事・総説・解説・論説等（学術雑誌）  

記述言語：日本語   掲載種別：記事・総説・解説・論説等（学術雑誌）  

記述言語：日本語   掲載種別：記事・総説・解説・論説等（学術雑誌）  

記述言語：日本語   掲載種別：記事・総説・解説・論説等（学術雑誌）  

記述言語：日本語  

種別：大会・シンポジウム等 

種別：大会・シンポジウム等 

参加者数：1,500

種別：大会・シンポジウム等 

参加者数：100

種別：査読等 

外国語雑誌　査読論文数：22

種別：大会・シンポジウム等 

参加者数：150

種別：査読等 

外国語雑誌　査読論文数：13

種別：査読等 

外国語雑誌　査読論文数：25

種別：大会・シンポジウム等 

種別：大会・シンポジウム等 

参加者数：1,200

種別：大会・シンポジウム等 

種別：査読等 

外国語雑誌　査読論文数：13

種別：査読等 

外国語雑誌　査読論文数：12

種別：審査・学術的助言 

種別：大会・シンポジウム等 

種別：大会・シンポジウム等 

参加者数：90

種別：審査・学術的助言 

種別：大会・シンポジウム等 

種別：大会・シンポジウム等 

参加者数：60

種別：大会・シンポジウム等 

参加者数：274

種別：大会・シンポジウム等 

種別：査読等 

外国語雑誌　査読論文数：10

種別：大会・シンポジウム等 

参加者数：25

種別：審査・学術的助言 

種別：審査・学術的助言 

種別：大会・シンポジウム等 

種別：大会・シンポジウム等 

種別：大会・シンポジウム等 

参加者数：400

種別：大会・シンポジウム等 

参加者数：800

種別：審査・学術的助言 

種別：大会・シンポジウム等 

参加者数：1,000