The Experts below are selected from a list of 1428 Experts worldwide ranked by ideXlab platform
Hideo Hosono - One of the best experts on this subject based on the ideXlab platform.
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ferromagnetic quasi atomic electrons in two dimensional Electride
Nature Communications, 2020Co-Authors: Joonho Bang, Yunwei Zhang, Jongho Park, Jaeyeol Hwang, Chandani Nandadasa, Hideo HosonoAbstract:An Electride, a generalized form of cavity-trapped interstitial anionic electrons (IAEs) in a positively charged lattice framework, shows exotic properties according to the size and geometry of the cavities. Here, we report that the IAEs in layer structured [Gd2C]2+·2e− Electride behave as ferromagnetic elements in two-dimensional interlayer space and possess their own magnetic moments of ~0.52 μB per quasi-atomic IAE, which facilitate the exchange interactions between interlayer gadolinium atoms across IAEs, inducing the ferromagnetism in [Gd2C]2+·2e− Electride. The substitution of paramagnetic chlorine atoms for IAEs proves the magnetic nature of quasi-atomic IAEs through a transition from ferromagnetic [Gd2C]2+·2e− to antiferromagnetic Gd2CCl caused by attenuating interatomic exchange interactions, consistent with theoretical calculations. These results confirm that quasi-atomic IAEs act as ferromagnetic elements and trigger ferromagnetic spin alignments within the antiferromagnetic [Gd2C]2+ lattice framework. These results present a broad opportunity to tailor intriguing ferromagnetism originating from quasi-atomic interstitial electrons in low-dimensional materials. Ferromagnetic quasi-atomic behavior of interstitial anionic electrons (IAEs) in practical Electrides is yet to be discovered experimentally. Here, the authors reveal that IAEs in two-dimensional Electride [Gd2C]²+⋅2e- behave as magnetic elements with their own magnetic moment.
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Ternary Inorganic Electrides with Mixed Bonding
Physical Review B, 2019Co-Authors: Jun-jie Wang, Zhenhai Wang, Hideo HosonoAbstract:A high-throughput screening based on first-principles calculations was performed to search for new ternary inorganic Electrides. From the available materials database, we identified three new thermodynamically stable materials (Li$_{12}$Mg$_3$Si$_4$, NaBa$_2$O and Ca$_5$Ga$_2$N$_4$) as potential Electrides made by main group elements, in addition to the well known mayenite based Electride (C12A7:$e^-$). Different from those conventional inorganic Electrides in which the excess electrons play only the role of anions, the three new materials, resembling the Electrides found in simple metals under high pressure, possess mixed ionic and metallic bonding. The interplay between two competing mechanisms, together with the different crystal packing motifs, gives rise to a variety of geometries in anionic electrons, and rich physical phenomena such as ferromagnetism, superconductivity and metal-insulator transition. Our finding here bridges the gap between Electrides found at ambient and high pressure conditions.
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intermetallic Electride catalyst as a platform for ammonia synthesis
Angewandte Chemie, 2018Co-Authors: Jiazhen Wu, Jiang Li, Yutong Gong, Masaaki Kitano, Takeshi Inoshita, Hideo HosonoAbstract:: Electrides loaded with transition-metal (TM) nanoparticles have recently attracted attention as emerging materials for catalytic NH3 synthesis. However, they suffer from disadvantages associated with the growth and aggregation of nanoparticles. TM-containing intermetallic Electrides appear to be promising catalysts with the advantages of both Electrides and transition metals in a single phase. LaRuSi is reported here to be an intermetallic Electride with superior activity for NH3 synthesis, and direct evidence is provided supporting its Electride-character-induced catalytic performance. The discussion is made mainly based on the contrasting synthesis rates over the isostructural compounds LaRuSi, CaRuSi, and LaRu2 Si2 , and the N2 isotope-exchange reactions over these compounds. Lattice hydride ions, which can reversibly exchange with anionic electrons, are shown to be indispensable in the promotion of NHx formation. The mechanism derived from the present findings provides new guidelines for NH3 synthesis.
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Electride and superconductivity behaviors in Mn_5Si_3-type intermetallics
npj Quantum Materials, 2017Co-Authors: Yaoqing Zhang, Bosen Wang, Zewen Xiao, Yangfan Lu, Toshio Kamiya, Yoshiya Uwatoko, Hiroshi Kageyama, Hideo HosonoAbstract:Electrides are unique in the sense that they contain localized anionic electrons in the interstitial regions. Yet they exist with a diversity of chemical compositions, especially under extreme conditions, implying generalized underlying principles for their existence. What is rarely observed is the combination of Electride state and superconductivity within the same material, but such behavior would open up a new category of superconductors. Here, we report a hexagonal Nb_5Ir_3 phase of Mn_5Si_3-type structure that falls into this category and extends the Electride concept into intermetallics. The confined electrons in the one-dimensional cavities are reflected by the characteristic channel bands in the electronic structure. Filling these free spaces with foreign oxygen atoms serves to engineer the band topology and increase the superconducting transition temperature to 10.5 K in Nb_5Ir_3O. Specific heat analysis indicates the appearance of low-lying phonons and two-gap s -wave superconductivity. Strong electron–phonon coupling is revealed to be the pairing glue with an anomalously large ratio between the superconducting gap Δ _0 and T _c, 2 Δ _0/ k _B T _c = 6.12. The general rule governing the formation of Electrides concerns the structural stability against the cation filling/extraction in the channel site. Coexistence of Electride behavior and superconductivity is observed in a hexagonal phase of a Nb_5Ir_3 intermetallic with tunable electronic properties by introducing foreign atoms. A team led by Yaoqing Zhang and Hideo Hosono from Japan Science and Technology Agency and Tokyo Institute of Technology report a new hexagonal phase in the phase diagram of Nb–Ir binary intermetallics with interesting interplay of superconductivity and Electride state. The Electride state is formed by electrons detaching from the atoms but localizing in a one-dimensional channel space. This Electride becomes a superconductor below a transition temperature of about 9.4 K, which could be enhanced to 10.5 K upon filling interstitial cavities with foreign oxygens. The results suggest a general rule governing the formation of Electrides and form the basis for novel stable functional Electrides.
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Electride and superconductivity behaviors in mn 5 si 3 type intermetallics
npj Quantum Materials, 2017Co-Authors: Yaoqing Zhang, Bosen Wang, Zewen Xiao, Yangfan Lu, Toshio Kamiya, Yoshiya Uwatoko, Hiroshi Kageyama, Hideo HosonoAbstract:Electrides are unique in the sense that they contain localized anionic electrons in the interstitial regions. Yet they exist with a diversity of chemical compositions, especially under extreme conditions, implying generalized underlying principles for their existence. What is rarely observed is the combination of Electride state and superconductivity within the same material, but such behavior would open up a new category of superconductors. Here, we report a hexagonal Nb5Ir3 phase of Mn5Si3-type structure that falls into this category and extends the Electride concept into intermetallics. The confined electrons in the one-dimensional cavities are reflected by the characteristic channel bands in the electronic structure. Filling these free spaces with foreign oxygen atoms serves to engineer the band topology and increase the superconducting transition temperature to 10.5 K in Nb5Ir3O. Specific heat analysis indicates the appearance of low-lying phonons and two-gap s-wave superconductivity. Strong electron–phonon coupling is revealed to be the pairing glue with an anomalously large ratio between the superconducting gap Δ 0 and T c, 2Δ 0/k B T c = 6.12. The general rule governing the formation of Electrides concerns the structural stability against the cation filling/extraction in the channel site. Coexistence of Electride behavior and superconductivity is observed in a hexagonal phase of a Nb5Ir3 intermetallic with tunable electronic properties by introducing foreign atoms. A team led by Yaoqing Zhang and Hideo Hosono from Japan Science and Technology Agency and Tokyo Institute of Technology report a new hexagonal phase in the phase diagram of Nb–Ir binary intermetallics with interesting interplay of superconductivity and Electride state. The Electride state is formed by electrons detaching from the atoms but localizing in a one-dimensional channel space. This Electride becomes a superconductor below a transition temperature of about 9.4 K, which could be enhanced to 10.5 K upon filling interstitial cavities with foreign oxygens. The results suggest a general rule governing the formation of Electrides and form the basis for novel stable functional Electrides.
Satoru Matsuishi - One of the best experts on this subject based on the ideXlab platform.
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Hydride-Based Electride Material, LnH2 (Ln = La, Ce, or Y)
Inorganic Chemistry, 2016Co-Authors: Hiroshi Mizoguchi, Satoru Matsuishi, Masaaki Kitano, Masaaki Okunaka, Toshiharu Yokoyama, Hideo HosonoAbstract:In view of the strong electron-donating nature of H– and extensive vacancy formation in metals by hydrogen insertion, a series of LnH2+x (Ln = La, Ce, or Y) compounds with fluorite-type structures were verified to be the first hydride-based Electride, where itinerant electrons populating the cage are surrounded by H– anions. The electron transfer into the cage probably originates from Ln–cage covalent interaction. To the best of our knowledge, anion-rich Electrides are extremely rare, and a key requirement for their formation is that the cage site is not occupied by lone pair electrons of the adjacent ions. In the case of LnH2, the cage site is surrounded by eight H– anions with isotopic electronic character caused by the lack of mixing of H p-orbital character. Notably, Ru-loaded LnH2+x Electride powders synthesized by hydrogen embrittlement (Ln = La or Ce) were found to work as efficient catalysts for ammonia synthesis at ambient pressure, without showing serious signs of hydrogen poisoning. There are s...
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hydride based Electride material lnh2 ln la ce or y
Inorganic Chemistry, 2016Co-Authors: Hiroshi Mizoguchi, Satoru Matsuishi, Masaaki Kitano, Masaaki Okunaka, Toshiharu Yokoyama, Hideo HosonoAbstract:In view of the strong electron-donating nature of H– and extensive vacancy formation in metals by hydrogen insertion, a series of LnH2+x (Ln = La, Ce, or Y) compounds with fluorite-type structures were verified to be the first hydride-based Electride, where itinerant electrons populating the cage are surrounded by H– anions. The electron transfer into the cage probably originates from Ln–cage covalent interaction. To the best of our knowledge, anion-rich Electrides are extremely rare, and a key requirement for their formation is that the cage site is not occupied by lone pair electrons of the adjacent ions. In the case of LnH2, the cage site is surrounded by eight H– anions with isotopic electronic character caused by the lack of mixing of H p-orbital character. Notably, Ru-loaded LnH2+x Electride powders synthesized by hydrogen embrittlement (Ln = La or Ce) were found to work as efficient catalysts for ammonia synthesis at ambient pressure, without showing serious signs of hydrogen poisoning. There are s...
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two dimensional transition metal Electride y2c
Chemistry of Materials, 2014Co-Authors: Xiao Zhang, Satoru Matsuishi, Zewen Xiao, Toshio Kamiya, Yoshitake Toda, Shigenori Ueda, Hideo HosonoAbstract:Electrides are ionic crystals in which the anionic electrons are confined to interstitial subnanometer-sized spaces. At present, the reported Electrides only consist of main-group elements. Here, we report a layered-structure transition-metal hypocarbide Electride, Y2C, with quasi-two-dimensional (quasi-2D) anionic electrons confined in the interlayer space. Physical properties measurements reveal polycrystalline Y2C exhibits semimetallic behavior, and paramagnetism with an effective magnetic moment of ∼0.6 μB/Y, because of the existence of localized d-electrons. Photoelectron spectroscopy measurements illustrate the work function of polycrystalline Y2C is 2.9 eV, lower than Y metal, revealing the loosely bound nature of the anionic electrons. Density functional theory calculations indicate the density of states at the Fermi level originates from the states at interstitial sites and the Y 4d-orbitals, supporting the confinement of anionic electrons within the interlayer space. These results demonstrate th...
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high throughput ab initio screening for two dimensional Electride materials
Inorganic Chemistry, 2014Co-Authors: Tomofumi Tada, Satoru Matsuishi, Seiji Takemoto, Hideo HosonoAbstract:High-throughput ab initio screening of approximately 34000 materials in the Materials Project was conducted to identify two-dimensional (2D) Electride materials, which are composed of cationic layers and anionic electrons confined in a 2D empty space. The screening was based on three indicators: (1) a positive total formal charge per formula unit; (2) layered structures for two-dimensionality; (3) empty spaces between the layer units. Three nitrides, Ca2N, Sr2N, and Ba2N, and the carbide Y2C were identified as 2D Electrides, where Ca2N is the only experimentally confirmed 2D Electride (Lee, K.; et al. Nature 2013, 494, 336–341). Electron density analysis using ionic radii revealed a smaller number of anionic electrons in Y2C than those in the three nitrides as a result of the partial occupation of the anionic electrons in the d orbitals of Y. In addition, no candidates were identified from the p-block elements, and thus the ab initio screening indicates that the s-block elements (i.e., alkali or alkaline-...
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Dicalcium nitride as a two-dimensional Electride with an anionic electron layer
Nature, 2013Co-Authors: Yoshitake Toda, Satoru Matsuishi, Hideo HosonoAbstract:The physical properties of Electrides — ionic crystals in which electrons behave as anions — significantly depend on the topology of the confining cavity for anionic electrons. Thus, an essential step towards practical Electride applications is to discover new confinement spaces with unique topologies. Confined two-dimensional electron layers have previously been achieved by artificially fabricating hetero-interface structures usually of semiconducting materials. Here the authors extend the range of materials demonstrating such behaviour to an Electride, dicalcium nitride (Ca_2N). This compound has ideal properties for electron confinement: a layered structure with appropriate interlayer spacing and a chemistry that allows for loosely bound electron layers without electron trapping. By providing a new material image for Electrides, this work should lead to a series of two-dimensional Electrides with unique physical properties. Recent studies suggest that Electrides—ionic crystals in which electrons serve as anions—are not exceptional materials but rather a generalized form, particularly under high pressure^ 1 , 2 , 3 . The topology of the cavities confining anionic electrons determines their physical properties^ 4 . At present, reported confining sites consist only of zero-dimensional cavities or weakly linked channels^ 4 . Here we report a layered-structure Electride of dicalcium nitride, Ca_2N, which possesses two-dimensionally confined anionic electrons whose concentration agrees well with that for the chemical formula of [Ca_2N]^+·e^−. Two-dimensional transport characteristics are demonstrated by a high electron mobility (520 cm^2 V^−1 s^−1) and long mean scattering time (0.6 picoseconds) with a mean free path of 0.12 micrometres. The quadratic temperature dependence of the resistivity up to 120 Kelvin indicates the presence of an electron–electron interaction. A striking anisotropic magnetoresistance behaviour with respect to the direction of magnetic field (negative for the field perpendicular to the conducting plane and positive for the field parallel to it) is observed, confirming diffusive two-dimensional transport in dense electron layers. Additionally, band calculations support confinement of anionic electrons within the interlayer space, and photoemission measurements confirm anisotropic low work functions of 3.5 and 2.6 electronvolts, revealing the loosely bound nature of the anionic electrons. We conclude that Ca_2N is a two-dimensional Electride in terms of [Ca_2N]^+·e^−. The ionic crystal Ca_2N is shown to be an Electride in terms of [Ca_2N]^+·e^−, with diffusive two-dimensional transport in dense electron layers.
Masahiro Hirano - One of the best experts on this subject based on the ideXlab platform.
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thermal conductivity and seebeck coefficient of 12 cao 7 al 2 o 3 Electride with a cage structure
Physical Review B, 2009Co-Authors: Ryuichi Tarumi, Masahiro Hirano, Hideo Iwasaki, Hiromichi Ohta, Hideo HosonoAbstract:Thermal conductivity $(\ensuremath{\kappa})$ and Seebeck coefficient $(\ensuremath{\alpha})$ of electron-doped light-metal oxide $12\text{CaO}\ensuremath{\cdot}7{\text{Al}}_{2}{\text{O}}_{3}$ (C12A7 Electride) with a subnanometer-sized cage structure are reported on single crystals with various electron concentrations $({N}_{\text{e}})$. The semiconducting C12A7 Electride exhibits $n$-type conduction with the highest $\ensuremath{\alpha}$ value of $\ensuremath{-}100\text{ }\ensuremath{\mu}\text{V}\text{ }{\text{K}}^{\ensuremath{-}1}$ at 300 K. The $\ensuremath{\kappa}$ exhibits an amorphouslike ${T}^{2}$ dependence at low temperatures and varies between 2.3 and $4.5\text{ }{\text{Wm}}^{\ensuremath{-}1}\text{ }{\text{K}}^{\ensuremath{-}1}$ at 300 K. This is an order-of-magnitude lower than that of the constituents, CaO $(15\text{ }{\text{Wm}}^{\ensuremath{-}1}\text{ }{\text{K}}^{\ensuremath{-}1})$ and ${\text{Al}}_{2}{\text{O}}_{3}$ $(30\text{ }{\text{Wm}}^{\ensuremath{-}1}\text{ }{\text{K}}^{\ensuremath{-}1})$. These properties are attributed to the cage structure, suggesting that the semiconducting Electride should be regarded as a phonon glass and electron crystal material. The thermoelectric performance of Electrides evaluated by a dimensionless figure of merit $(ZT)$ shows an optimized value of $2\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$ at 300 K for the semiconducting Electride with ${N}_{\text{e}}$ of $5\ifmmode\times\else\texttimes\fi{}{10}^{20}\text{ }{\text{cm}}^{\ensuremath{-}3}$.
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Direct Synthesis of Powdery Inorganic Electride [Ca 24 Al 28 O 64 ] 4+ (e - ) 4 and Determination of Oxygen Stoichiometry
Chem. Mater, 2009Co-Authors: Satoru Matsuishi, Shin-ichi Shamoto, Takatoshi. Nomura, Katsuaki Kodama, Masahiro Hirano, Hideo HosonoAbstract:Electrides 1 are quasi-ionic crystals in which electrons serve as anions. The anionic electrons are spatially sepa-rated from molecular cations by cavity and/or channel structures formed by organic complexants or crystallo-graphic cages or channel walls in zeolitic crystals. In 2003, we succeeded in the synthesis of an inorganic Electride using a Ca 12 Al 14 O 33 crystal (C12A7), which is an air-and room-temperature-stable material in the category of the Electride. 2 C12A7 has a mayenite-type crystal structure, whose chemical formula of the unit cell is expressed by [Ca 24 Al 28 O 64 ] 4+ (O 2-) 2 . The " free oxygen ions " (O 2-) are trapped as counteranions in the cages embedded in the positively charged framework ([Ca 24 Al 28 O 64 ] 4+). The free oxygen ions can be selectively removed via appro-priate reduction treatments or knock-on processes by energetic ions. 3 The removal results in the electron injec-tion to the cage, which in turn imparts persistent electro-nic conductivity to C12A7. The electron-encaging C12A7 exhibits a metal-insulator transition at the critical elec-tron concentration of ∼1 Â 10 21 cm -3 , and the C12A7 Electride with the theoretical maximum electrons (2.3 Â 10 21 cm -3), i.e., [Ca 24 Al 28 O 64 ] 4+ (e -) 4 , undergoes super-conducting transition at ∼0.4 K. 4 Moreover, the skeleton structure of the Electride provides an unique playground for various anionic chemical species stabilized by strong Madelung potential of the cages, which hardly exist under usual conditions. Typical examples are O 2 -, O -, H -, and Au -. 5-7 Furthermore, several applications have been found for the C12A7 Electride. Among them, one expects the Electride usable for vacuum electronics as electron source materials for cold and thermo-field emissions by utilizing an small work function (2.4 eV). 8 Another promising application field is organic syntheses. It has been reported recently that the C12A7 Electride acts as a selective reducing agent in organic reactions in water media, for instance, pinacol coupling of aromatic alde-hydes. 9 These reactions are conventionally performed in nonaqueous solutions with an aid of reducing agents such as alkali and alkali-earth metal compounds. The C12A7 Electrides have been synthesized by redu-cing bulk C12A7 single crystals grown by Czochralski method and the Electride powders have been prepared by grinding the bulk Electride crystals. Thus, alternative mass productive methods for the powder, such as a direct synthesis from powder mixtures, are highly required to realize the chemical applications of the Electride. Here we report a direct synthesis method for the preparation of the C12A7 Electride powder with the electron density up to the theoretical maximum of 2.33 Â 10 21 cm -3 . Further-more, we demonstrate a comprehensive technique for the precise determination of the oxygen stoichiometry of the C12A7 Electride powders. The technique involves X-ray fluorescence (XRF), powder X-ray diffraction (XRD), neutron powder diffraction (NPD), thermo-gravimetric/ differential thermal analyses (TG/DTA), and diffuse reflectance spectroscopy. C12A7 Electride powder was synthesized by a reaction of C12A7, CaO 3 Al 2 O 3 (CA), and Ca metal at 700-1100 °C: 0.8Ca 12 Al 14 O 33 + 1.4CaAl 2 O 4 + Ca f Ca 12 Al 14 O 32 . More specifically, it was synthesized by the following seven-step procedure. First, a mixture of C12A7 and CaO 3 Al 2 O 3 (CA) was prepared by a reaction of CaCO 3 (99.99%, particle size of ∼10 μm, Kojundo Chemical) and R-Al 2 O 3 (99.99%, ∼10 μm, Kojundo) with a molar ratio of 11:7 at 1300 °C for 6 h in an ambient air: 11CaCO 3 + 7Al 2 O 3 f 0.8Ca 12 Al 14 O 33 + 1.4CaAl 2 O 4 + 11CO 2 v (i). The sintered mixture (C12A7+CA) was
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Fabrication of room temperature-stable 12CaO · 7Al_2O_3 Electride: a review
Journal of Materials Science: Materials in Electronics, 2007Co-Authors: Satoru Matsuishi, Katsuro Hayashi, Masahiro Hirano, Masashi Miyakawa, Hideo HosonoAbstract: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.
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Superconductivity in an Inorganic Electride 12CaO·7Al2O3:e-
Journal of the American Chemical Society, 2007Co-Authors: Masashi Miyakawa, Yoshimitsu Kohama, Hiroki Ikegami, Hitoshi Kawaji, Tooru Atake, Masahiro Hirano, Kimitoshi Kono, Hideo HosonoAbstract:An inorganic Electride, 12CaO·7Al2O3:e-, synthesized by exclusively replacing oxygen ions in the sub-nanometer-sized cages of 12CaO·7Al2O3 crystal with electrons exhibits a superconducting transition at a temperature (Tc) of ∼0.4 K. Tc varies in the range of 0.14−0.4 K with the concentration of anionic electrons, which are primarily distributed over crystallographic spaces without occupying any particular framework ions. The precursor of Electride is composed of representative metal oxides, which are electrical insulators. Thus, the exotic crystal structure of Electrides provides an insight for a material platform to realize a new superconductor.
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fabrication of room temperature stable 12cao 7al 2 o 3 Electride a review
Journal of Materials Science: Materials in Electronics, 2007Co-Authors: Satoru Matsuishi, Katsuro Hayashi, Masahiro Hirano, Masashi Miyakawa, Hideo HosonoAbstract:12CaO · 7Al2O3 (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.
Masashi Miyakawa - One of the best experts on this subject based on the ideXlab platform.
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Fabrication of room temperature-stable 12CaO · 7Al_2O_3 Electride: a review
Journal of Materials Science: Materials in Electronics, 2007Co-Authors: Satoru Matsuishi, Katsuro Hayashi, Masahiro Hirano, Masashi Miyakawa, Hideo HosonoAbstract: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.
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Superconductivity in an Inorganic Electride 12CaO·7Al2O3:e-
Journal of the American Chemical Society, 2007Co-Authors: Masashi Miyakawa, Yoshimitsu Kohama, Hiroki Ikegami, Hitoshi Kawaji, Tooru Atake, Masahiro Hirano, Kimitoshi Kono, Hideo HosonoAbstract:An inorganic Electride, 12CaO·7Al2O3:e-, synthesized by exclusively replacing oxygen ions in the sub-nanometer-sized cages of 12CaO·7Al2O3 crystal with electrons exhibits a superconducting transition at a temperature (Tc) of ∼0.4 K. Tc varies in the range of 0.14−0.4 K with the concentration of anionic electrons, which are primarily distributed over crystallographic spaces without occupying any particular framework ions. The precursor of Electride is composed of representative metal oxides, which are electrical insulators. Thus, the exotic crystal structure of Electrides provides an insight for a material platform to realize a new superconductor.
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fabrication of room temperature stable 12cao 7al 2 o 3 Electride a review
Journal of Materials Science: Materials in Electronics, 2007Co-Authors: Satoru Matsuishi, Katsuro Hayashi, Masahiro Hirano, Masashi Miyakawa, Hideo HosonoAbstract:12CaO · 7Al2O3 (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.
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Fabrication of room temperature-stable 12CaO · 7Al 2 O 3 Electride: a review
Journal of Materials Science: Materials in Electronics, 2007Co-Authors: Satoru Matsuishi, Katsuro Hayashi, Masahiro Hirano, Masashi Miyakawa, Hideo HosonoAbstract:12CaO · 7Al2O3 (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.
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Superconductivity in an inorganic Electride 12CaO x 7Al2O3:e-.
Journal of the American Chemical Society, 2007Co-Authors: Masashi Miyakawa, Yoshimitsu Kohama, Hiroki Ikegami, Sung Wng Kim, Hitoshi Kawaji, Tooru Atake, Masahiro Hirano, Kimitoshi Kono, Hideo HosonoAbstract:An inorganic Electride, 12CaO·7Al2O3:e-, synthesized by exclusively replacing oxygen ions in the sub-nanometer-sized cages of 12CaO·7Al2O3 crystal with electrons exhibits a superconducting transition at a temperature (Tc) of ∼0.4 K. Tc varies in the range of 0.14−0.4 K with the concentration of anionic electrons, which are primarily distributed over crystallographic spaces without occupying any particular framework ions. The precursor of Electride is composed of representative metal oxides, which are electrical insulators. Thus, the exotic crystal structure of Electrides provides an insight for a material platform to realize a new superconductor.
Katsuro Hayashi - One of the best experts on this subject based on the ideXlab platform.
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Fabrication of room temperature-stable 12CaO · 7Al_2O_3 Electride: a review
Journal of Materials Science: Materials in Electronics, 2007Co-Authors: Satoru Matsuishi, Katsuro Hayashi, Masahiro Hirano, Masashi Miyakawa, Hideo HosonoAbstract: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.
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fabrication of room temperature stable 12cao 7al 2 o 3 Electride a review
Journal of Materials Science: Materials in Electronics, 2007Co-Authors: Satoru Matsuishi, Katsuro Hayashi, Masahiro Hirano, Masashi Miyakawa, Hideo HosonoAbstract:12CaO · 7Al2O3 (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.
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Fabrication of room temperature-stable 12CaO · 7Al 2 O 3 Electride: a review
Journal of Materials Science: Materials in Electronics, 2007Co-Authors: Satoru Matsuishi, Katsuro Hayashi, Masahiro Hirano, Masashi Miyakawa, Hideo HosonoAbstract:12CaO · 7Al2O3 (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.
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simple and efficient fabrication of room temperature stable Electride melt solidification and glass ceramics
Journal of the American Chemical Society, 2005Co-Authors: Masashi Miyakawa, Katsuro Hayashi, Masahiro Hirano, Takashi Sakai, Hideo HosonoAbstract: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 ...
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Electron localization and a confined electron gas in nanoporous inorganic Electrides
Physical Review Letters, 2003Co-Authors: Peter V. Sushko, Katsuro Hayashi, Masahiro Hirano, Alexander L Shluger, Hideo HosonoAbstract:The nanoporous main group oxide 12CaO.7Al(2)O3 (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.
