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）  

Materials that are good electrical conductors are not in general optically transparent, yet a combination of high conductivity and transparency is desirable for many emerging opto-electronic applications. To this end, various transparent oxides composed of transition or post-transition metals (such as indium tin oxide) are rendered electrically conducting by ion doping. But such an approach does not work for the abundant transparent oxides of the main-group metals. Here we demonstrate a process by which the transparent insulating oxide 12CaO·7Al₂O₃ (refs 7-13) can be converted into an electrical conductor. H^- ions are incorporated into the subnanometre-sized cages of the oxide by a thermal treatment in a hydrogen atmosphere; subsequent irradiation of the material with ultraviolet light results in a conductive state that persists after irradiation ceases. The photo-activated material exhibits moderate electrical conductivity (∼0.3 S cm^-1) at room temperature, with visible light absorption losses of only one per cent for 200-nm-thick films. We suggest that this concept can be applied to other main-group metal oxides, for the direct optical writing of conducting wires in insulating transparent media and the formation of a high-density optical memory.

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）  

The positive temperature coefficient of resistivity (PTCR) effect is directly measured in single grain boundaries in 0.1-mol%-Nb-doped BaTiO₃ with 1 mm coarse grains. The PTCR effect largely depends on grain boundary structure. Random grain boundaries exhibit the PTCR effect as in polycrystalline samples, but the PTCR effect does not appear in highly coherent boundaries such as small-angle boundaries, twin boundaries, and coincidence site lattice (CSL) boundaries with low ∑ values. For ∑= 3 boundaries, the resistance increase above the Curie temperature is a function of deviation angle. A small PTCR effect is observed in ∑ = 3 boundaries with a deviation angle of about 9° in contrast with ideal ∑ = 3 boundaries and boundaries with a deviation of about 4°.

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

出版者・発行元：npj Computational Materials  

Wurtzite-type ferroelectrics are highly promising for next-generation microelectronic devices due to their ferroelectric properties and integration with exiting semiconductors. However, their high coercive fields, which are close to breakdown electric fields, need to be lowered. To deal with this issue and secure device reliability, much effort has been devoted to exploring novel wurtzite compounds with lower polarization switching barriers and implementing doping strategies. Here, we report first-principles calculations on polarization switching in cation-vacancy ordered wurtzite α-Al2S3, unveiling its uniaxial quadruple-well ferroelectricity and moderate switching barrier, 51 meV/cation, which is much lower than that of conventional wurtzite ferroelectrics. There are three important features relevant to the Al vacancies leading to the uncommon quadruple-well ferroelectricity and the moderate switching barrier: mitigation of cation-cation repulsion, structural flexibility that alleviates an in-plane lattice expansion, and formation of σ-like bonding states consisting of Al 3pz and S 3pz orbitals. Biaxial compressive strain and Ga doping lower the switching barriers by up to 40%. This study encourages experimental investigation of the ferroelectric properties for defective wurtzite α-Al2S3 as a new promising material with unconventional and intriguing ferroelectricity and suggests a potential strategy for reducing switching barriers in wurtzite ferroelectrics: introducing cation vacancies.

DOI： 10.1038/s41524-025-01519-3

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出版者・発行元：ACS Materials Letters  

The Na3SbS4 solid electrolyte has achieved high ionic conductivity (σion) exceeding 10 mS/cm through aliovalent doping. While σion is enhanced through aliovalent doping, a rigorous atomic-scale mechanistic explanation is needed. Doping also affects σion by modifying ion mobility-an effect that is not well understood and often overlooked. We use first-principles defect calculations to mechanistically explain and quantify the increase/decrease in Na vacancy concentration due to aliovalent doping of Na3SbS4. By focusing on isovalent doping, we reveal local and global structural effects of doping on the migration barrier and, therefore, ion mobility. In conjunction with experiments, we demonstrate the interplay between the local and global effects. Doping with heavier anions to achieve more polarizable frameworks is a common approach to enhancing σion. Our findings present a unique approach to enhancing σion by doping with smaller and lighter cations that soften the parent framework.

DOI： 10.1021/acsmaterialslett.4c01619

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

A-site cation ordering in double perovskites is crucially important for their physical properties. In this study, polycrystalline samples of Zr-based double perovskite NaLaZr2O6 were synthesized via high-temperature solid-state reactions, and the influence of the heating temperature and cooling rate on their crystal structures was investigated using synchrotron X-ray diffractometry and optical second harmonic generation. The samples prepared at 1200 °C, followed by slow cooling to room temperature, crystallize in a polar P21am structure, exhibiting partial A-site cation ordering, with Na- and La-rich A-site layers alternately stacked along the c axis. Remarkably, this structure transforms to a previously reported nonpolar Pnam phase with a disordered A-site cation arrangement when the slow-cooled samples are reheated at 1300 °C or higher and then rapidly quenched to room temperature. Theoretical analyses reveal that in the P21am phase, the a-a-c+ octahedral rotations trigger antiparallel displacements of the A-site cations in the Na- and La-rich A-site layers to induce spontaneous polarization. This is in contrast to the case of the Pnam phase, in which the rotation-induced antiparallel displacements of the equivalent A-site cations are antipolar. This work represents a rare example of AA′B2O6 perovskites exhibiting layered A-site ordering and polarity and also demonstrates a novel mechanism for reversible thermal switching from polar to nonpolar states in perovskites.

DOI： 10.1021/acs.inorgchem.4c04267

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PubMed

出版者・発行元：Journal of Materials Chemistry A  

Oxide-based all-solid-state sodium-ion batteries present a safer, more robust and more sustainable alternative to lithium-ion batteries, though fabrication challenges persist, particularly during co-sintering. In this study, we demonstrate that by adding sodium borate-based sintering aids to highly conductive Na3Zr2(SiO4)2(PO4) (NZSP)-based materials, both a lower sintering temperature and high ionic conductivity can be achieved. Specifically, the mixture of Na2CO3 and B2O3 as a sintering aid is crucial, and samples sintered at 900 °C with a Na3.4Zr1.95Al0.05(SiO4)2.35(PO4)0.65 composition exhibits a Na+ ion conductivity exceeding 4 × 10−3 S cm−1 at room temperature. These materials are also compatible with co-sintering alongside hard carbon anode materials. The all-solid-state cell, featuring a composite electrode of spherical hard carbon particles and optimized NZSP-based electrolytes, demonstrated stable charge-discharge performance at room temperature, retaining a capacity of 140-220 mA h g−1 across 80 cycles.

DOI： 10.1039/d4ta07954j

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出版者・発行元：Journal of Alloys and Compounds  

The electrical conductivity of NaxLa(1−x)/3NbO3 ceramics has been studied over a composition range of 0.15 ≤ x ≤ 0.45 to identify optimal conductivity conditions and to elucidate the structural and chemical factors affecting the Na+ ion conductivity. The composition with x = 0.25 achieves the highest total conductivity of 7.0 × 10−4 S cm−1 at 350 °C, with Na+ ion transference number of unity. The random distribution of Na, La and vacancy in the two crystallographically independent A sites in perovskite structures significantly impacts the conductivity. In addition, NaxLa(1−x)/3NbO3 perovskite ceramics exhibit high dielectric constants (εr = 220−470) and suppressed electronic conductivity, making them potentially beneficial as an interfacial material to mitigate chemical potential differences between electrolytes and electrode active materials.

DOI： 10.1016/j.jallcom.2024.177335

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出版者・発行元：Advanced Energy Materials  

Compared to Li+ and Na+ ion-conducting sulfides with conductivities of ≈10⁻2 S cm⁻1 at room temperature, oxide ceramics typically exhibit conductivities an order of magnitude lower, rendering them less attractive as electrolytes for all-solid-state batteries (ASSBs). This study presents NASICON-based electrolyte, achieving a remarkable conductivity of 6.0 × 10⁻3 S cm⁻1 at room temperature, rivaling that of sulfide-based electrolytes. This is accomplished by optimizing the composition in the range Na3+x+yZr2−yAlySi2+xP1−xO12 (0.10 ≤ x ≤ 0.50, 0 ≤ y ≤ 0.1). Despite the issue of reduced sinterability with increasing Si/P ratio due to the formation of a viscous SiO2-rich grain boundary interphase, the addition of Al2O3 effectively reduces the viscosity and improves the sinterability. In other words, a strategy of engineering the liquid phase that is in situ generated from the host phase is viable. The enhanced conductivity is attributed not only to the lowered grain boundary resistivity but also to lattice expansion from modified Na occupations in the crystal structure. Furthermore, this material demonstrates a wide electrochemical window, suppressed partial electronic conductivity, low polarization voltage in direct contact with a Na anode, and charge-discharge cycles with minimal polarization when directly interfaced with a NASICON-type cathode, repositioning it as a promising electrolyte for ceramic ASSBs.

DOI： 10.1002/aenm.202402891

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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   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  

CsNdNb2O7 is a hybrid improper ferroelectric (HIF) where oxygen octahedral rotation modes induce spontaneous polarization. While CsLaNb2O7 is also believed to be an HIF, its polar structure and ferroelectric properties remain poorly understood. This study investigates their solid solution, CsLa1-xNdxNb2O7, by constructing a temperature-composition phase diagram using synchrotron X-ray diffractometry, first-principles calculations, and dielectric measurements. Upon cooling, the Nd-rich compositions (x = 0.5, 0.75, and 1) undergo phase transitions from a P4/mmm to a C2/m and then to a polar P21am phase. Both transition temperatures decrease as x decreases. The polar P21am phase, accompanied by ferroelectric polarization switching, is stabilized at room temperature only when x = 0.75 and 1. For La-rich compositions, the nonpolar C2/m phase remains down to room temperature without exhibiting any indication of transformation into the polar P21am phase. Theoretical calculations suggest that a symmetry trapping effect hinders the nonpolar (C2/m)-to-polar (P21am) phase transition.

DOI： 10.1021/acs.inorgchem.4c04245

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記述言語：日本語   掲載種別：論文集(書籍)内論文   出版者・発行元：(公社)電気化学会 電池技術委員会, 第422回電池技術委員会資料  

Na3Zr2(SiO4)2(PO4)系電解質の高性能化とナトリウム革新電池への展開

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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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：英語   掲載種別：研究論文（学術雑誌）  

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   出版者・発行元：AIP Publishing  

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：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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出版者・発行元：Ceramics International  

Glass-ceramic processes to prepare NASICON-type NaxTi2(PO4)3, which is an anode candidate for sodium-ion batteries, from 30Na2O–40TiO2–30P2O5 glass have been investigated with varied atmospheric conditions. By annealing in the inert (N2) atmosphere, the glass started crystalizing into NASICON-type NaTi2(PO4)3 with rhombohedral symmetry at ∼600 °C followed by crystallization of other phases to be multiphase mixtures at higher temperatures. In contrast, in the reducing (5% H2/Ar) atmosphere, NASICON-type Na3Ti2(PO4)3 with triclinic symmetry is crystallized at >∼800 °C. The formation of Na3Ti2(PO4)3 is associated with a loss of excess oxygens in the initial glass composition and a reduction of Ti from Ti4+ to Ti3+. The reduction process upon the glass-to-ceramic conversion was traced by in-situ observation during the thermogravimetric analysis. It is also revealed that the electrochemical Na + -storage capabilities of the glass-ceramic electrodes are correlated with the Na-ion occupancy between these two phases, and their phase fractions affect the charge-discharge properties of Na-ion cells. Finer glass-ceramic powders could improve the electrochemical properties and achieve almost 80% of its theoretical capacity.

DOI： 10.1016/j.ceramint.2022.05.125

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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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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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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）  

A composite thermionic cathode consisting of 12CaO·7Al ₂O₃ (C12A7) electride and metallic Ti (70 : 30 vol %) was fabricated as an electron emitter, and the thermionic electron emission properties were evaluated. A high emission current density of ∼1:4mAcm ^-2 was achieved at 700 °C with an electric field of 4:0 × 10⁴ Vcm^-1. The work function evaluated from the Richardson-Dushman equation was 2:1 ± 0:3 eV, which coincides with the value for pure C12A7 electride and is lower than that for LaB₆. Unlike the pure material, the composite has ohmic contact with metallic materials, and can be heated directly by electrical current.

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）  

An atomic oxygen (AO) source has been redesigned to coordinate with a pulsed laser deposition system and used to grow nitrogen-doped TiO₂ films by deposition of TiN and simultaneous irradiation of the substrate with AO. The AO source uses an incandescently heated thin tube of zirconia as an oxygen permeation media to generate pure AO of low kinetic energy. The emission flux is calibrated using a silver-coated quartz crystal microbalance. The thin shape of the probe and transverse emission geometry of this emission device allow the emission area to be positioned close to the substrate surface, enhancing the irradiation flux at the substrate. AO irradiation is crucial for formation of TiO₂ phases via oxidation of the deposited TiN laser plume, and is effective for decrease of the substrate temperature for crystallization of anatase phase to as low as around 200 C.

DOI： 10.1063/1.3683571

記述言語：英語   掲載種別：研究論文（学術雑誌）  

In oxides, the substitution of non-oxide anions (F ^-S ^2-N ^3- and so on) for oxide introduces many properties, but the least commonly encountered substitution is where the hydride anion (H-) replaces oxygen to form an oxyhydride. Only a handful of oxyhydrides have been reported, mainly with electropositive main group elements or as layered cobalt oxides with unusually low oxidation states. Here, we present an oxyhydride of the perhaps most well-known perovskite, BaTiO₃, as an O ^2-/H-solid solution with hydride concentrations up to 20% of the anion sites. BaTiO_3-x H_x is electronically conducting, and stable in air and water at ambient conditions. Furthermore, the hydride species is exchangeable with hydrogen gas at 400°C. Such an exchange implies diffusion of hydride, and interesting diffusion mechanisms specific to hydrogen may be at play. Moreover, such a labile anion in an oxide framework should be useful in further expanding the mixed-anion chemistry of the solid state.

DOI： 10.1038/nmat3302

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）  

While most ceramics are composed of ubiquitous elements (the ten most abundant elements within the Earth's crust), many advanced materials are based on rare elements. A 'rare-element crisis' is approaching owing to the imbalance between the limited supply of rare elements and the increasing demand. Therefore, we propose a 'ubiquitous element strategy' for materials research, which aims to apply abundant elements in a variety of innovative applications. Creation of innovative oxide materials and devices based on conventional ceramics is one specific challenge. This review describes the concept of ubiquitous element strategy and gives some highlights of our recent research on the synthesis of electronic, thermionic and structural materials using ubiquitous elements.

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）  

Persistent electrons are generated in hydride (H^-) ion-doped 12CaO·7Al₂O₃ (C12A7) by UV irradiation at room temperature. The kinetics of thermal electron decay is examined using experimental data collected at 200-295 °C. The observed reaction order together with activation energy shifts approximately from one-half to first depending on the electron concentration and temperature. The data is explained by a two-electron transfer reaction (H^- + O^2- ↔ OH^- + 2e^-) with H⁰ and H⁺ as reaction intermediates and diffusion of these hydrogen species. The observed one-half-order kinetics originates from a zero-order reaction influenced by inhomogeneity of the electron concentration. The electron decay rate is principally determined by the supply of H⁺ ions liberated from OH^- ions. The large activation energy (1.9 ± 0.3 eV) of this process is responsible for the persistence of electrons at room temperature. As the residual electron concentration decreases, the contribution of electron trapping by the intermediate hydrogen species becomes dominant for the rate-determination, shifting the reaction order and activation energy.

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）  

Particle emissions from an oxide-ion conducting solid electrolyte (tetragonal zirconia polycrystal, 3% Y ₂O ₃-doped ZrO ₂) have been examined using a high vacuum evaluation system. Oxygen gas with a pressure range from 10 to 3 × 10 ³ Pa was fed into a 2 mm outer diameter zirconia tube, whose central region of 10 mm length was heated to 1400-1800 °C by direct Joule heating. The emission species were identified by appearance potential spectroscopy using a quadrupole mass spectrometer. Atomic oxygen (AO) is the dominant species that is radiantly emitted from the high-temperature region. Temperature dependence of the AO emission intensity exhibits far less activation energy (̃0.3-1.0 and 0.7 eV, on average) than electric field-assisted thermal O ^- ion (̃2 eV) and electron (̃6 eV) emission from zirconia reported before. High AO emission flux (in the order of 10 ¹⁷ atoms.cm ^-2.s ^-1) is promising for use as practical AO sources.

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）  

We have examined electric field-assisted thermionic emission of oxygen radical anion (O-) and electron from a stoichiometric 12CaO7 Al ₂O₃ (C12A7). Lattice framework of C12A7 is composed of subnanometer-sized cages that can accommodate extra- framework species with negative charge, such as O-, O2- ions, and electrons. Absence of oxygen gas supply leads to a steady coemission of O- ion and electron with a ratio of ∼3:7. However, the oxygen gas supply markedly enhances the O- ion emission and suppresses the electron emission, realizing a sustainable and high-purity O- ion emission with a current density up to 11 nA cm-2 at 825°C. The O- ion emission accompanies a weak O2- ion emission, which is smaller by ∼130. TheO₂ pressure at the rear side controls the concentrations of O- ion and electron on the emission surface as well as their concentrations in the bulk, and in turn, determines their emission intensities.

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）  

We report a metallic state in a nanostructured porous crystal 12CaO-7Al₂O₃ by incorporating electrons in the inherent subnanometer-sized cages, in which a three-dimensionally closely packed cage structure acts as an electronic conduction path. High-density electron doping (∼2 x 10²¹ cm^-3), which was achieved by a thermal treatment in Ti metal vapor at ∼1100 °C, induces homogenization of the cage geometry to a symmetric state, resulting in an insulator-metal transition with a sharp enhancement of the electron drift mobility from ∼0.1 to 4 cm² V^-1 s^-1. The results provide an approach for the realization of electroactive functions in materials composed only of environmentally benign elements by utilizing the appropriate nanostructures.

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）  

We performed a theoretical analysis of O2- diffusion mechanisms in a nanoporous complex oxide 12CaO7 Al2 O3 (C12A7). This material can be viewed as a positively charged framework, arranged in subnanometer sized cages, hosting extra-framework O2- ions occupying one in six cages. Using both classical molecular-dynamics simulations and ab initio calculations we demonstrate that the diffusion of O2- species is dominated by the exchange of framework and extra-framework O2- ions rather than by an interstitial diffusion mechanism. The results allow us to rationalize the origins of the experimentally observed high oxide ion conductivity of C12A7 and the stability of its lattice under positive ion-beam irradiation.

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）  

Thermal field emission (TFE) from a flat surface of 12CaO·7 Al2 O3 (C12A7) electride was examined at temperatures up to 900 °C and applied external voltages of 0-6 kV in a 10-5 Pa vacuum. TFE started to occur at ∼650 °C and steeply increased at ∼900 °C to reach ∼80 μA (∼1.5 A cm-2) when an extraction field of 105 V cm-1 (an extraction voltage of 6 kV) was applied. The work function estimated from the Richardson-Dushman equation was ∼2.1 eV, which is rather smaller than that of La B6 (∼2.7 eV). It is experimentally confirmed that the emission with a current of ∼50 μA (from a 80 μm diameter area) was stably sustained for more than 90 h. The efficient and stable emission at relatively low temperature in a moderate vacuum atmosphere strongly suggests that the C12A7 electride has high potential for TFE applications.

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）  

Atomic hydrogen (H⁰) and trapped electrons generated by UV illumination (λ _∼ 330 nm) at 4 K were observed using electron paramagnetic resonance (EPR) in a 12CaO·7Al₂O₃ (C12A7) crystal heated in a hydrogen atmosphere. The concentration ratio of generated H⁰ to the electrons encaged in the subnanometer-sized cages of C12A7 (F⁺ centers) is almost 1:1, providing direct evidence that a hydride ion, H^-, accommodated in the cage by the heat treatment was dissociated to a pair of an H⁰ and an electron by a UV photon: H^- → H⁰ + e^- (F⁺). After annealing at 300 K, H⁰ was completely annihilated, while _∼60% of the trapped electrons survived. The remaining electrons can hop between neighboring cages and give electrical conductivity to C12A7. The hyperfine splitting of the EPR spectrum of H⁰ in C12A7 (48.6 mT) is 4% smaller than that of the neutral hydrogen atom (50.6 mT), implying that H⁰ is trapped at the interstitial sites among the cages.

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）  

In some electroceramic materials, their unique electrical properties are due to potential barriers, i.e., double Schottky barriers (DSBs), formed at grain boundaries. So far, some researchers have revealed that the electrical properties of DSB are closely related to grain boundary characters, especially grain boundary coherency. For example, highly coherent boundary does not give PTCR or varistic property, while random types exhibit clear resistivity jump or abrupt current increment. Therefore, a concept of grain boundary design will be required for future device manufacturing, even in bulk materials. But it has not been clarified yet why the electron transport behaviors depend on them. In order to address this question, it is necessary to carry out a systematic experiment focusing on single grain boundaries using well-defined bicrystals. In the present study, we have summarized our studies with a special interest in electron transport behavior across single grain boundaries for n-type BaTiO ₃, SrTiO₃ and ZnO.

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）  

Electrides are ionic compounds in which electrons act as anions. These compounds are expected to have interesting properties arising from their exotic structure. The fatal drawbacks of the thermal and chemical instability of organic electrides were resolved by the synthesis of a room temperature (RT) stable electride using single crystalline 12CaO·7Al₂O₃ (C12A7) with a nanoporous structure and the chemical treatments for a long duration. However, an innovative fabrication method is obviously required for practical applications such as cold electron-emitter and thermionic devices. Herein we report a simple synthesis for polycrystalline C12A7 electrides with a moderate electronic conductivity via a strongly reducing C12A7 "melt", i.e., direct solidification of the melt or crystallization of the transparent glass. Generation of carrier electrons and precipitation of the C12A7 phase from the strongly reducing melt and glass are likely associated with the incorporation of carbon-related anions for stabilizing the C12A7 phase and keeping the mobile electrons in C12A7. These findings will be broadly utilized for applications by mass production in a desired shape and dimension, facilitating the research of electrides.

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）  

Inert gas ion implantation (acceleration voltage 300 kV) into polycrystalline 12CaO·7 Al2 O3 (C12A7) films was investigated with fluences from 1× 1016 to 1× 1017 cm-2 at elevated temperatures. Upon hot implantation at 600 °C with fluences greater than 1× 1017 cm-2, the obtained films were colored and exhibited high electrical conductivity in the as-implanted state. The extrusion of O2- ions encaged in the crystallographic cages of C12A7 crystal, which leaves electrons in the cages at concentrations up to ~1.4× 1021 cm-3, may cause the high electrical conductivity. On the other hand, when the fluence is less than 1× 1017 cm-2, the as-implanted films are optically transparent and electrically insulating. The conductivity is enhanced and the films become colored by irradiating with ultraviolet light due to the formation of F+ -like centers. The electrons forming the F+ -like centers are photo released from the encaged H- ions, which are presumably derived from the preexisting OH- groups. The induced electron concentration is proportional to the calculated displacements per atom, which suggests that nuclear collision effects of the implanted ions play a dominant role in forming the electron and H- ion in the films. The hot ion implantation technique provides a nonchemical process for preparing electronic conductive C12A7 films.

DOI： 10.1063/1.1829151

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Partial oxidation of methane into syngas (CO and H₂) was investigated over 12CaO·7Al₂O₃ (Cl2A7) promoted by metals such as Ni, Co, Pt, Pd and Ru. The effect of space velocity and metal loading was studied, and the catalytic behavior of Ni/Cl2A7 was compared with nickel catalysts supported on CaO, α-Al₂O₃ and other calcium aluminates with high CaO/Al₂O₃ ratio. On Ni, Pt and Pd/Cl2A7, this reaction readily happened at temperatures as low as 500 °C and attained thermodynamic equilibrium. Five samples were investigated at 800 °C and at a space velocity of 240,000 ml g^-1 h^-1. Their activity values decreased in the following order: 1% Pt/Cl2A7 > 5% Co/C12A7 > 5% Ni/C12A7 > 1% Ru/C12A7 > 1% Pd/Cl2A7. The activity and selectivity of Ni/Cl2A7 and Pt/Cl2A7 increased with metal loading, and the activity of 10% Ni/C12A7 has been comparable to that of 1% Pt/C12A7. Ni/C12A7 exhibitedlow coke formation rate and the material was more active than nickel supported on CaO, α-Al₂O₃, 3CaO·Al₂O3 (C3A) or CaO·Al₂O₃ (CA), owing to the good dispersion of NiO on C12A7 and the existence of active oxygen ions incorporated in its nanocages.

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）  

Continuous wave and pulsed electron paramagnetic resonance studies were performed on the Superoxide ion, O₂-, encaged in the nanoporous crystal 12CaO'7Al₂O₃ (C12A7). Hyperfine splitting due to ¹⁷O in O₂- was observed in C12A7 heated in 40% ¹⁷O-enriched O₂ gas at 550 °C, providing solid evidence that encaged O₂derives from gaseous O₂ in the atmosphere via reactions with free oxygen ions in the cage. Angular variations of g values, ¹⁷O hyperfine splitting in the single crystal at 20 K, and ²⁷Al electron spin-echo envelope modulation pattern for the powder at 4 K clarified that an O₂- is encaged in a subnanometer-sized cage of C12A7 and adsorbed on a Ca^2- ion forming a part of the cage wall. Further, two oxygen atoms in the O₂ion are equivalent in the cage, indicating that the O₂- ion takes a "side-on" configuration. Then, the O-O bond is perpendicular to the 2-fold rotation axis (C₂ \\ (100)) across the center of the cage and directed to two oxygen ions forming the cage wall. Variation in the g values with temperature indicates that the O₂- may be regarded as solidlike below ∼20 K and above this temperature the rocking motion of the O-O bond about the C₂ axis is activated with an increase in temperature, but the anisotropy in the motion remains even at 400 K. This result may be explained by a view that Coulombic interaction of the Ca^2- with the fully occupied π orbital in the O₂ ^- is stronger than that with the semioccupied π orbital, controlling the dynamics.

DOI： 10.1021/jp046963s

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 process in a nanoporous crystal, 12CaO-7Al₂O₃, were examined by isothermal annealing experiments in dry atmospheres. It is clarified that the formation of oxygen radicals, O^-₂ and O^-, in the crystal occurs in the following three steps; outward diffusion of extra-framework oxide ions, its oxidation by absorbed oxygen molecules to form O^- and O^-₂ at the surface, and subsequent inward diffusion of the oxygen radicals. The instability of the extra-framework oxide ions is essentially the driving force for the process. Further, the analyses allow to predict the total oxygen radical content for a given annealing condition.

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）  

We report distinct optical/electrical properties inherent to build-in nanostructures in transparent oxide based materials, oxychalcogenides LaCuOS and LaCuOSe having naturally formed multi-quantum well structures and 12CaO·7Al₂ O₃ (C12A7) with a unique nanoporous structure. LaCuOSe doped with Mg ions exhibit degenerative p-type conduction presumable due to "modulation doping mechanism" with a high mobility of 4.0 cm² V^-1 s^-1 even at high hole concentration (∼2×10²⁰ cm^-3). The room temperature exciton, having a large binding energy (∼50 meV) due to the confinement effect of carriers in the CuS or CuSe layer, induces a large optical nonlinearity at room temperature (RT) (χ⁽³⁾ = 2-4×10^-9 esu) near the absorption band. The H^- ion entrapped in nanosize cages in C12A7 lattice causes an persistent conversion at RT from an electric insulator (<10^-10 S cm^-1) to a semiconductor (0.3-100 S cm^-1) by capturing electrons photo-ionized from H^- ions in the cages. This is a first electronic conductor based on main group light metal oxides.

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）  

Nanostructures naturally formed in oxide semiconductor crystals are discussed in relation to their electronic structure and properties. Three different crystals are studied: (i) layered oxychalcogenides LnCuOCh (Ln = lanthanide, Ch = chalcogen), (ii) homologous series layered oxides RMO ₃(ZnO)_m (R = In, Lu etc., M = In, Ga etc., m = integer), and (iii) nanoporous crystal 12CaO7 · Al₂O₃ (C12A7). Coexistence of moderately large mobility, intense photoluminescence arising from room-temperature exciton and high-density hole is explained by a natural modulation doping structure in LnCuOCh. C12A7 exhibits different properties by replacing free O^2- ions anions clathrated in its subnanometer-sized cages with O^-, H^-, and electron. The electronic structures of the clathrated anions were investigated by ab initio calculations and discussed in terms of possible quantum structures and applications.

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）  

[Ca₂₄Al₂₈O₆₄]⁴⁺(4e^-) is a new inorganic electride, which is air-stable even at ∼ 300°C. Its electron field-emission properties originate from electron anions encaged in subnanometer-sized cages embedded in its crystal structure. und the emission current is controlled by Fowler-Nordheim field emission at high electric fields (see Figure). Field-emission display devices demonstrate bright light emission clearly visible under ambient light (inset).

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Simultaneous measurements of remote electron beam induced current (REBIC) and orientation imaging microscopy (OIM) in a scanning electron microscope (SEM) have been applied to a polycrystalline (Ba_0.6Sr_0.4)TiO₃ with a positive temperature coefficient of resistivity (PTCR) to elucidate a grain-boundary character dependence of the potential barrier formation. The absence of electrical activity in a coherent Σ3 twin boundary is clearly imaged. The resistivity of individual grain boundaries estimated from a resistive contrast image is interpreted in terms of geometrical coherency, which is defined by the degree of coincidence in the reciprocal lattice points.

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）  

The nanoporous main group oxide [Formula presented] (C12A7) can be transformed from a wide-gap insulator to an electride where electrons substitute anions in cages constituting a positive frame. Our ab initio calculations of the electronic structure of this novel material give a consistent explanation of its high conductivity and optical properties. They show that the electrons confined in the inert positive frame are localized in cages and undergo hopping between neighboring cages. The results are useful for the understanding of behavior of confined electron gas of different topology and electron-phonon coupling, and for designing new transparent conductors, electron emitters, and electrides.

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）  

Strong and high purity O^- negative ion emission has been observed from a synthesized crystal 12CaO7Al₂O₃ surface. A μA/cm²-level O^- emission from this material has been achieved at the surface temperature of 800°C and the extraction field over 1000 V/cm, which is about three orders of magnitude higher than the current density emitted from the Y₂O₃-stabilized ZrO₂ electrolyte surface. The strong emissivity of this material, as well as easy and economical fabrication, may provide a useful tool to generate the O^- negative ion, which is expected to be one of the most important radicals for chemical syntheses and material modifications.

DOI： 10.1063/1.1476958

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Reproducibility, stability and oxygen-pressure dependence of O^- negative ion emission from a synthesized crystal 12CaO · 7Al₂O₃ (C12A7) surface have been investigated. We found the continuous O^- implantation into the C12A7 crystal can be simply realized by supplying electron and oxygen on the Au-deposited C12A7 surface via electrocatalytic reactions. The O^- emission from the consumed C12A7 surface was recovered after the implantation operation (O₂:0.13 Pa; 770°C) for 30 minutes. In contrast, the implantation influence on electron emission is negligible. The O^- emission intensity is nearly constant in the O₂ pressure lower than 1 × 10^-3 Pa. The O^- implantation mechanism will be addressed.

記述言語：英語   掲載種別：研究論文（学術雑誌）  

We have grown single crystals of Ca₁₂Al₁₄O₃₃ (C12A7), a congruently melting compound, by the floating zone method. With the conventional method, the shape of the solid-liquid interface was concave, and many bubbles and cracks remained in the grown crystal. To reduce them, the crystal growth at a lower growth rate and the control of the shape of the solid-liquid interface were examined. For the growth rate <0.3 mm/h, the amount of bubbles was reduced considerably. However, in such a condition, a significantly large bubble was often formed in the molten zone, which disturbed the stability of the molten zone. Introducing an alumina tube as a heat reservoir at a suitable position in the heated area, the shape of the solid-liquid interface could be changed from concave to a convex one. This may suggest that the effect of the concave interface could be eliminated and crystals with high quality may be grown at a higher growth rate.

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）  

A near-UV emitting diode was fabricated by successive heteroepitaxial growth of In₂O₃:Sn(ITO), n-electrode, n-ZnO, and p-SrCu₂O₂ (SCO) on an extremely flat surface of yttria-stabilized ZrO₂ single crystalline substrate using a pulsed-laser deposition technique. Upon current injection at room temperature, the resulting diode emitted near-UV light with a peak at 382 nm. The threshold voltage for emission was ∼ 3 V, which is in agreement with the energy difference between the ZnO donor level and the SCO acceptor level. The epitaxial relationship between SCO and ZnO depends on the deposition temperature of SCO on ZnO. The inhomogeneity of the SCO crystal was improved by raising the deposition temperature from 350°C to 600°C. The threshold current for near-UV emission from the diode fabricated by deposition of the SCO film at 600°C was reduced to ∼ 1/5 of that at 350°C. A reason why this heteroepitaxial growth occurs for oxides with large lattice misfit is explained in terms of the high ionicity of chemical bonds in oxides.

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）  

Resistance-temperature (R-T) characteristics were measured directly at single-grain boundaries in 0.1-mol%-niobium-doped barium titanate bicrystals that had been fabricated from polycrystalline sinters, to determine a geometrical grain-boundary character dependence of the positive temperature coefficient of resistivity (PTCR) effect. Both random boundaries and low-Σ boundaries exhibit a similar grain-boundary character dependence of the PTCR effect through a simple geometrical analysis, using the coincidence of reciprocal lattice points. Differences of the R-T characteristics in individual boundaries have been explained in terms of the formation of a potential barrier that is associated with the oxidation of grain boundaries during cooling, after sintering or annealing. The grain-boundary character is likely to affect the diffusivity of O^2- ions and, hence, is crucial to the formation of the potential barrier.

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）  

The influence of orientation of grain boundary plane as well as misorientation of grain boundary on positive temperature coefficient of resistivity (PTCR) was examined in 0.1mol%Nb-doped barium titanate. The magnitude of the PTCR effect mainly depends on tilt component of misorientation as compared to twist one. This dependence is considered to be related to the fact that grain boundary with low-index plane has low grain boundary energy, and hence hinders the formation of potential barrier.

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Grain boundary structure and electrical properties were examined for Nb-doped SrTiO₃ bicrystals. Bicrystals with Σ1, cobalt-segregated Σ1, and small angle boundaries were prepared by hot joining technique. High-resolution transmission electron microscopy (HRTEM) study revealed that two single crystals were perfectly joined without any secondary phases in all kinds of bicrystals. Σ1 boundary exhibited linear I-V characteristic while non-linear I-V behavior appeared in cobalt-segregated Σ1 boundary in spite of the similar coherent boundary. On the other hand, it was found that non-linearity became remarkable by reduction of cooling-rate after joining even in a small angle boundary, whose dislocation structure is stable against annealing treatment. This result suggests that negative-charged point defects must play an important role on the formation of potential barriers.

記述言語：英語   掲載種別：研究論文（学術雑誌）  

The chemical bonding state at grain boundaries was examined with electron- energy-loss spectroscopy in BaTiO₃doped with a small amount of cations at a level of 0.001. In contrast with A-site excess compounds, the oxygen K-edge electron energy-loss near-edge structure spectra were different for grain interiors and for grain boundaries in B-site excess compounds. The difference is explained in terms of the linkage of TiO₆octahedra at grain boundaries in the B-site excess BaTiO₃.

DOI： 10.1080/095008399177165

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Grain boundary structure was examined with HRTEM and EELS for BaTiO₃ doped with a small amount of cations with a special interest in chemical bonding state. It was found that the grain boundary structure was sensitive to a small excess of Ti-site dopant. The grain boundaries arc facetted with {210} habits and an ordered structure is formed. HRETM and EELS examination combined with molecular orbital calculation clearly revealed that TiO₆ octahedral linkage changes from corner-sharing in the grain interior to edge-sharing at the grain boundary.

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Positive temperature coefficient of resistivity (PTCR) effect is directly measured in bicrystal specimens of Nb-doped BaTiO₃ to examine its grain boundary character dependence and to clarify the nature of the potential barrier formed at grain boundaries. The coherency of grain boundaries is evaluated from a geometric method based on the coincidence of reciprocal lattice points (CRLP). Larger PTCR effects were obtained for random grain boundaries rather than coherent boundaries. The formation of the potential barrier is discussed from an analysis of the resistance-temperature characteristics.

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Grain boundary structure in BaTiO₃ doped with a small amount of dopants was examined. It was found that grain growth behavior was very sensitive to the substituting sites of dopants, i.e., A- or B-site in a perovskite structure ABO₃. Abnormal grain growth takes place in B-site type dopant excess BaTiO₃ while normal grain growth occurs in A-site type dopant excess BaTiO₃. High-resolution electron microscopy (HRTEM) study associated with electron energy-loss spectroscopy (EELS) revealed that the grain boundaries were facetted with {210} type habits and extra Ti-O₂ bonds were formed along the facetted grain boundaries in the compounds doped with B-site type dopants. Controlling the doping ratio of A- and B-site type dopants severely, coarse-grained sinters whose grain size was about 1 mm could be obtained.

記述言語：英語   掲載種別：研究論文（学術雑誌）  

A numerical calculation based on a drift-diffusion model was made to explain the experimental current-voltage (J-V) characteristics at a single grain boundary in Nb-doped BaTiO₃. The temperature dependence of breakdown voltage in J-V characteristics can be reasonably explained by taking into account the change in occupation of interface states. The nonlinearity coefficients in J-V characteristics are interpreted in terms of energetic distribution of interface states and spatial distribution of the states near the grain boundary.

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Both current-voltage (I-V) and capacitance-voltage (C-V) characteristics were studied in Nb-doped BaTiO₃ bicrystals to verify the potential barrier model. The potential barrier of n-i-n structure can reasonably describe the observed data in comparison with that of double Schottky barrier (DSB) model. The difference in the I-V characteristics between the two models is characterized by the appearance of the sub-ohmic behavior with α<1. In the DSB model, the barrier height is kept almost the same because the acceptor states are strongly pinned by the Fermi level. When the acceptor states are completely occupied, the potential barrier will collapse and then the current will increase steeply.

DOI： 10.1063/1.371140

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Charge-collection (CC) current was measured at a single grain boundary, which exhibited positive temperature coefficient of resistivity (PTCR) effects, in 0.1-mol%-Nb-doped BaTiO ₃. The CC current systematically reversed across the grain boundary above the Curie point, which indicated the presence of a double Schottky barrier (DSB) at the grain boundary. In contrast, the CC current was constant across the grain boundary below the Curie temperature. The result obtained from the CC current measurement agrees with the classical DSB model in donordoped BaTiO ₃, indicating the PTCR effects.

記述言語：英語   掲載種別：研究論文（学術雑誌）  

Grain boundary structure was examined in 0.1 mol% TiO₂-excess BaTiO₃ by high-resolution electron microscopy (HRTEM) and electron energy loss spectroscopy (EELS). Their grain boundaries were mostly faceted with {210} type habit. The faceted boundaries were characterized to be associated with an extra Ti-O₂ bond with the rutile-like structure. The grain growth behavior in a small TiO₂-excess BaTiO₃ is discussed from the viewpoint of grain boundary structure.

DOI： 10.1557/JMR.1998.0469

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開催地：タワーホール船堀（東京都江戸川区）   国名：日本国  

開催年月日： 2016年11月

記述言語：日本語  

開催地：長崎大学中部講堂（長崎県長崎市）   国名：日本国  

開催年月日： 2016年11月

記述言語：日本語  

開催地：長崎大学文教キャンパススカイホール（長崎県長崎市）   国名：日本国  

開催年月日： 2016年9月

記述言語：日本語  

開催地：広島大学東広島キャンパス（広島県東広島市）   国名：日本国  

開催年月日： 2016年9月

記述言語：日本語  

開催地：広島大学東広島キャンパス（広島県東広島市）   国名：日本国  

開催年月日： 2016年8月

記述言語：日本語  

開催地：京都大学桂キャンパス　ローム記念館大ホール（京都府京都市）   国名：日本国  

開催年月日： 2016年8月 - 2016年10月

記述言語：日本語  

開催地：ルートイングランティア大宰府（福岡県大宰府市）   国名：日本国  

開催年月日： 2016年8月

記述言語：日本語  

開催地：ルートイングランティア大宰府（福岡県大宰府市）   国名：日本国  

開催年月日： 2016年7月

記述言語：日本語  

開催地：埼玉大学工学部（埼玉県さいたま市）   国名：日本国  

開催年月日： 2016年6月 - 2016年7月

記述言語：英語  

開催地：Toronto Marriot Downtown Eaton Centre Hotel   国名：カナダ  

開催年月日： 2016年6月 - 2016年7月

記述言語：英語  

開催地：Toronto Marriot Downtown Eaton Centre Hotel   国名：カナダ  

開催年月日： 2016年5月

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：京都リサーチパーク（京都府）   国名：日本国  

開催年月日： 2016年3月

記述言語：日本語  

開催地：早稲田大学西早稲田キャンパス（東京都）   国名：日本国  

開催年月日： 2016年3月

記述言語：日本語  

開催地：早稲田大学西早稲田キャンパス（東京都）   国名：日本国  

開催年月日： 2016年1月

記述言語：日本語  

開催地：アバンセ（佐賀県立男女共同参画センター・佐賀県立生涯学習センター）（佐賀市）   国名：日本国  

開催年月日： 2016年1月

記述言語：日本語  

開催地：アバンセ（佐賀県立男女共同参画センター・佐賀県立生涯学習センター）（佐賀市）   国名：日本国  

開催年月日： 2015年12月

記述言語：日本語  

開催地：波止場会館（神奈川県横浜市）   国名：日本国  

開催年月日： 2015年11月

記述言語：英語  

開催地：Kunming University of Science and Technology   国名：中華人民共和国  

開催年月日： 2015年11月

記述言語：日本語  

開催地：アバンセ（佐賀県立男女共同参画センター・佐賀県立生涯学習センター）（佐賀市）   国名：日本国  

開催年月日： 2015年11月

記述言語：日本語  

開催地：アバンセ（佐賀県立男女共同参画センター・佐賀県立生涯学習センター）（佐賀市）   国名：日本国  

開催年月日： 2015年10月

記述言語：日本語  

開催地：Jeju International Convention Center   国名：大韓民国  

開催年月日： 2015年9月

記述言語：日本語  

開催地：九州大学   国名：日本国  

開催年月日： 2015年9月

記述言語：日本語  

開催地：富山大学（富山市）   国名：日本国  

開催年月日： 2015年9月

記述言語：日本語  

開催地：富山大学（富山市）   国名：日本国  

開催年月日： 2015年9月

記述言語：日本語  

開催地：富山大学（富山市）   国名：日本国  

開催年月日： 2015年9月

記述言語：日本語  

開催地：富山大学（富山市）   国名：日本国  

開催年月日： 2015年9月

記述言語：日本語  

開催地：富山大学（富山市）   国名：日本国  

開催年月日： 2015年9月

記述言語：日本語  

開催地：豊田中央研究所（愛知県長久手町）   国名：日本国  

開催年月日： 2015年9月

記述言語：日本語  

開催地：通潤山荘（熊本県上益城郡山都町）   国名：日本国  

開催年月日： 2015年7月

記述言語：英語  

開催地：西の雅　常盤（山口県山口市）   国名：日本国  

開催年月日： 2015年6月

記述言語：英語  

開催地：九州大学・カーボンニュートラル・エネルギー国際研究所　1F　ロビー   国名：日本国  

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   会議種別：口頭発表（一般）  

開催地：東北大学   国名：日本国  

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：神奈川大学横浜キャンパス   国名：日本国  

開催地：鹿児島(鹿児島大学)  

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：鹿児島大学(鹿児島市)   国名：日本国  

開催地：鹿児島(鹿児島大学)  

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：鹿児島大学(鹿児島市)   国名：日本国  

記述言語：日本語   会議種別：口頭発表（一般）  

開催地：鹿児島大学(鹿児島市)   国名：日本国  

開催地：鹿児島(鹿児島大学)  

開催地：長崎  

開催地：長崎  

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  

開催地：Orlando, USA   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：福岡西新プラザ  

開催地：福岡西新プラザ  

開催地：福岡西新プラザ  

開催地：名古屋工業大学  

開催地：京都大学吉田キャンパス  

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：スペイン・シッチェス Meliá Sitges Hotel Congress Centre  

開催地：スペイン・シッチェス Meliá Sitges Hotel Congress Centre  

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：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  

開催地：Congress & Exhibition Centre Acropolis  

開催地：Congress & Exhibition Centre Acropolis  

記述言語：英語  

開催地：Toronto Marriott Downtown at CF Eaton Centre Hotel   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  

開催地：沖縄コンベンションセンター  

開催地：沖縄コンベンションセンター  

開催地：沖縄コンベンションセンター  

開催地：沖縄コンベンションセンター  

開催地：沖縄コンベンションセンター  

開催地：沖縄コンベンションセンター  

開催地：沖縄コンベンションセンター  

開催地：沖縄コンベンションセンター  

開催地：沖縄コンベンションセンター  

記述言語：英語  

開催地：沖縄コンベンションセンター   国名：日本国  

開催地：沖縄コンベンションセンター  

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  

会議種別：ポスター発表  

開催地：北九州市  

会議種別：口頭発表（一般）  

開催地：名古屋大学  

会議種別：口頭発表（一般）  

開催地：名古屋大学  

会議種別：口頭発表（一般）  

開催地：福岡  

会議種別：口頭発表（一般）  

開催地：大阪  

会議種別：口頭発表（一般）  

開催地：大阪  

会議種別：口頭発表（一般）  

開催地：大阪  

会議種別：口頭発表（一般）  

開催地：大阪  

会議種別：口頭発表（一般）  

開催地：新潟  

会議種別：口頭発表（一般）  

開催地：新潟  

会議種別：口頭発表（招待・特別）  

国名：中華人民共和国  

会議種別：口頭発表（一般）  

国名：イタリア共和国  

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