Field-assisted sustainable O- ion emission from fluorine-substituted 12CaO·7Al2O3 with improved thermal stability

Jiang Li, Katsuro Hayashi, Masahiro Hirano, Hideo Hosono

Research output: Contribution to journalArticle

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Abstract

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.

Original languageEnglish
Pages (from-to)1113-1117
Number of pages5
JournalSolid State Ionics
Volume180
Issue number17-19
DOIs
Publication statusPublished - Jul 16 2009
Externally publishedYes

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ion emission
Fluorine
fluorine
Thermodynamic stability
thermal stability
Ions
ions
Gas supply
gases
operators
vacuum
thermionic emission
Vacuum
electron emission
Thermionic emission
purity
Electron emission
substitutes
current density
anions

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics

Cite this

Field-assisted sustainable O- ion emission from fluorine-substituted 12CaO·7Al2O3 with improved thermal stability. / Li, Jiang; Hayashi, Katsuro; Hirano, Masahiro; Hosono, Hideo.

In: Solid State Ionics, Vol. 180, No. 17-19, 16.07.2009, p. 1113-1117.

Research output: Contribution to journalArticle

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abstract = "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.",
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AU - Hosono, Hideo

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N2 - 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.

AB - 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.

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