High-intensity atomic oxygen radical anion emission mechanism from 12CaO·7Al2O3 crystal surface

Li, Quanxin; Hosono, Hideo; Hirano, Masahiro; Hayashi, Katsuro; Nishioka, Makihito; Kashiwagi, H.; Torimoto, Youshifumi; Sadakata, Masayoshi

doi:10.1016/s0039-6028(02)02575-x

Cited by 69 publications

(85 citation statements)

References 40 publications

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“…Nearly pure O À ion emission from the surface was confirmed by mass spectroscopy. [30][31][32][33] This result is in clear contrast from the YSZ, which emits equimolar O À ions and electrons. When the sample was heated to %800 C and the applied field was increased to %1 kV cm À1 , the O À current density exceeded %1 mA cm À2 , which is three orders of magnitude higher than that obtained in the YSZ emitter.…”

Section: Formation In Cagesmentioning

confidence: 88%

Functionalities of a Nanoporous Crystal 12CaO·7Al2O3 Originating from the Incorporation of Active Anions

Hayashi¹,

Hirano²,

Hosono³

2007

Bulletin of the Chemical Society of Japan

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A cage structure formed in a positively charged lattice framework of 12CaO Á 7Al 2 O 3 (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 À and O 2 À , are formed efficiently in these cages under a high oxygen activity condition. The O À 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 À ) ions in the cage. H À 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 À 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.

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Section: Formation In Cagesmentioning

confidence: 88%

Functionalities of a Nanoporous Crystal 12CaO·7Al2O3 Originating from the Incorporation of Active Anions

Hayashi¹,

Hirano²,

Hosono³

2007

Bulletin of the Chemical Society of Japan

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“…We fabricated a high performance of field effect transistor [7] employing single-crystalline thin films of InGaO 3 (ZnO) 5 [8] as the active layer. The resulting transistors exhibit a field mobility of , 80 cm 2 (Vs) 21 , which is comparable to that in polycrystalline Is-FET. Furthermore, an amorphous p-type oxide semiconductor was found and an amorphous oxide pin-diode with good rectifying properties was fabricated just by depositing on glass substrates at room temperature [9].…”

Section: Introductionmentioning

confidence: 76%

“…Simultaneously, a drastic increase in the conductivity was observed along with the coloration. The conductivity increased from , 10 10 S cm 21 to 0.5 S cm 21 . The Seebeck coefficient of the conductive sample is negative (2 360 mVK 21 ), indicating n-type conduction.…”

Section: Active Oxygen Manipulation: C12a7:omentioning

confidence: 92%

“…4). The beam of O 2 is monochromatic and the current density (, 2 mA/cm 2 ) is higher by three orders of magnitude than the maximum value recorded for Y-stabilized ZrO 2 (YSZ) [20,21]. A surface metal electrode, essential for the YSZ to dissociate a drifted O 2 2 in the bulk into an O 2 and an electron on the surface, is not needed for the C12A7.…”

Section: Active Oxygen Manipulation: C12a7:omentioning

confidence: 99%

“…H 2 ions are incorporated into the sub-nanometer-sized cages of the oxides by a thermal treatment in a hydrogen atmosphere at 1300 8C; subsequent illumination of the C12A7:H 2 with ultraviolet light results in a conductive state that persists after irradiation ceases. The photo-activated material exhibits moderate electrical conductivity (, 0.5 S cm 21 The C12A7: H 2 looks white in the polycrystalline powder or colorless and transparent for single crystals and is insulating (conductivity , 10 210 S cm 21 ). However, upon irradiating with ultraviolet light, two absorption bands centered at 2.8 and 0.4 eV are induced as shown in Fig.…”

Section: Active Oxygen Manipulation: C12a7:omentioning

confidence: 99%

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Functioning of traditional ceramics 12CaO·7Al₂O₃utilizing built-in nano-porous structure

Hosono

2004

Science and Technology of Advanced Materials

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This paper briefly reviews our approach to render active functions to micro porous crystal 12CaO·7Al 2 O 3 (C12A7), which is known as a constituent of alumina cement, utilizing nano-space and topology of sub-nanometer-sized cages inherent to the crystal structure. Each cage with a positive charge is coordinated by 12 cages to form a three-dimensional structure. This structure is a similar to a close packing of sphere except that each opening wall of a cage is shared with a neighboring cage. Free oxygen ion O 22 accommodates in 1/6 of the cages to reserve electro neutrality in the stoichiometric state. We replaced this free oxygen ion by other active anions such as O 2 , H 2 , and electron, aiming at emergence of novel function. C12A7:O 2 exhibited strong oxidation power enough to oxide Pt, and field-assisted thermionic O 2 emission to several mA levels, while conversion of insulator to persistent electronic conductor by illumination with ultraviolet radiation was discovered in C12A7:H 2 sample. Further, almost all of the free O 22 ions in the cages were successfully replaced by electrons by a chemical treatment using metallic Ca. The resulting material, which has a composition [Ca 24 Al 28 O 64 ] 4þ (4e 2 ) and a high conductivity, , 100 S cm 21 at 300 K, is a first room-temperature stable electride, in which electrons work as anions. The present approach to novel function emergence by solely employing abundant oxide materials and fully utilizing nanostructure provides a way for material research for future to be done under severe circumstance of environment and resource. q

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Palm‐Sized Ag⁺ Ion Emission Gun Operated at Room Temperature in Non‐Vacuum Atmosphere

Daiko

Segawa

Machida³

et al. 2018

Adv Eng Mater

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Ion implantation is an effective method for changing surface properties and inducing various functionalities. However, a high vacuum is generally necessary for ion implantation, which limits the range of applications. Here, we describe a palm‐sized Ag+ ion emission gun produced using a solid electrolyte. AgI–Ag2O–B2O3 glass, known as a super‐ion‐conducting glass, has a Ag+ ion conductivity higher than 5 × 10−3 S cm−1 at room temperature. In addition, the melted glass has suitable viscous flow, and a sharp glass‐fiber emitter with a pyramid‐like apex can be obtained. Ag+ ion emission is observed from the tip of the glass fiber at accelerating voltages corresponding to electric fields above 20 kV cm−1, even at room temperature in a non‐vacuum atmosphere. Ag nanoparticles of size 50–350 nm are precipitated on a Si target substrate. Other glass components such as boron and iodine are not detected. Electrochemical quartz crystal microbalance (EQCM) measurements show that the mass of Ag nanoparticles estimated from the emission current using Faraday's law of electrolysis is in good agreement with that estimated from the QCM frequency shift.

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High-intensity atomic oxygen radical anion emission mechanism from 12CaO·7Al2O3 crystal surface

Cited by 69 publications

References 40 publications

Functionalities of a Nanoporous Crystal 12CaO·7Al2O3 Originating from the Incorporation of Active Anions

Functionalities of a Nanoporous Crystal 12CaO·7Al2O3 Originating from the Incorporation of Active Anions

Functioning of traditional ceramics 12CaO·7Al₂O₃utilizing built-in nano-porous structure

Palm‐Sized Ag⁺ Ion Emission Gun Operated at Room Temperature in Non‐Vacuum Atmosphere

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High-intensity atomic oxygen radical anion emission mechanism from 12CaO·7Al2O3 crystal surface

Cited by 69 publications

References 40 publications

Functionalities of a Nanoporous Crystal 12CaO·7Al2O3 Originating from the Incorporation of Active Anions

Functionalities of a Nanoporous Crystal 12CaO·7Al2O3 Originating from the Incorporation of Active Anions

Functioning of traditional ceramics 12CaO·7Al2O3utilizing built-in nano-porous structure

Palm‐Sized Ag+ Ion Emission Gun Operated at Room Temperature in Non‐Vacuum Atmosphere

Contact Info

Product

Resources

About

Functioning of traditional ceramics 12CaO·7Al₂O₃utilizing built-in nano-porous structure

Palm‐Sized Ag⁺ Ion Emission Gun Operated at Room Temperature in Non‐Vacuum Atmosphere