Localisation assisted by the lattice relaxation and the optical absorption of extra-framework electrons in 12CaO·Al2O3

Sushko, Peter V.; Shluger, Alexander L.; Hayashi, Katsuro; Hirano, Masahiro; Hosono, Hideo

doi:10.1016/j.msec.2005.06.047

Cited by 15 publications

(16 citation statements)

References 20 publications

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“…The excitation spectrum of 4.5 eV emission supports this assumption-holes in framework valence band can be created if hν exc > 6.5 eV. According to [9] the distance of occupied cage level from the top of the valence band depends on the concentration of trapped electrons, which is also in compliance with our results regarding treatment of samples in oxygen gas flow, strongly affecting the possibility for capturing of electrons in cages (see Fig. 1).…”

supporting

confidence: 88%

Luminescence of nanoporous C12A7 compound

Feldbach

Kirm

Liblik

et al. 2007

Phys. Status Solidi (c)

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A comparison of excitation spectra of photostimulated and ordinary luminescence enabled us for the first time to determine experimentally the framework energy gap value E g = 6.5 eV of 12CaO · 7 Al 2 O 3 (C12A7). The most short-wavelength luminescence band (peaked at ~4.5 eV) detected at 10 K can be interpreted either as luminescence of intrinsic excitations or as recombination of electrons, captured in subnanometer sized cages of C12A7 crystal structure, with holes of valence band. The main peak of thermostimulated luminescence (134-137 K) is composed of two emission bands peaked at 2.8 and 4.5 eV. The calculated activation energy 0.44 eV of spectrally resolved (at 4.5 eV) thermally stimulated luminescence peak at 137 K is close to the value (0.4 eV) needed to initiate the inter-cage charge transfer of electrons (polaron hopping) between cages.

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supporting

confidence: 88%

Luminescence of nanoporous C12A7 compound

Feldbach

Kirm

Liblik

et al. 2007

Phys. Status Solidi (c)

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“…Sushko et al have performed a theoretical calculation based on the density functional theory and the embedded cluster approach, which fully account for the lattice relaxation around a defect, [37][38][39] to clarify electronic states of H À or electron in cages (F þ -like center) and mechanism of the irradiation-induced insulator-conductor conversion. Results of the calculation are summarized in Fig.…”

Section: Incorporation Of Hmentioning

confidence: 99%

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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“…The oxidization of the C12A7 surface and formation of a thin semiconductive surface layer is responsible for the dramatic decrease in the value of the apparent work function via the band bending effect, which is beneficial in order to improve the efficiency of cold emission [15]. Additionally, the chemical stability of C12A7 in air or a humid environment at room temperature as well as considerably higher emission current makes it superior to organic electrides [17], [18].…”

Section: A C12a7 Electron Emitter In Field Emission Displaymentioning

confidence: 99%

12CaO.7Al Ceramic: A Review of the Electronic and Optoelectronic Applications in Display Devices

Feizi

Ray

2016

J. Display Technol.

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The alumina-based compound, 12CaO.7Al O , is a ceramic material with a unique cage-like lattice. Such a structure has enabled scientists to extract various new characteristics from this compound, most of which were unknown until quite recently. This compound has the ability to incorporate different anionic species and even electrons to the empty space inside its cages, thereby changing from an insulator into a conductive oxide. The cage walls can also incorporate different rare earth phosphor elements producing an oxide-based phosphor. All these characteristics are obtained without a significant change in the structure of the lattice. It is, therefore, reasonable to expect that this compound will receive attention as a potential material for display applications. This review article presents recent investigations into the application of 12CaO.7Al O ceramic in various display devices, the challenges, opportunities and possible areas of future investigation into the development of this naturally abundant and environmental friendly material in the field of display.

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Localisation assisted by the lattice relaxation and the optical absorption of extra-framework electrons in 12CaO·Al2O3

Cited by 15 publications

References 20 publications

Luminescence of nanoporous C12A7 compound

Luminescence of nanoporous C12A7 compound

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

12CaO.7Al Ceramic: A Review of the Electronic and Optoelectronic Applications in Display Devices

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