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 language | English |
|---|---|
| Pages (from-to) | 1113-1117 |
| Number of pages | 5 |
| Journal | Solid State Ionics |
| Volume | 180 |
| Issue number | 17-19 |
| DOIs | |
| Publication status | Published - Jul 16 2009 |
| Externally published | Yes |
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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 journal › Article
}
TY - JOUR
T1 - Field-assisted sustainable O- ion emission from fluorine-substituted 12CaO·7Al2O3 with improved thermal stability
AU - Li, Jiang
AU - Hayashi, Katsuro
AU - Hirano, Masahiro
AU - Hosono, Hideo
PY - 2009/7/16
Y1 - 2009/7/16
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.
UR - http://www.scopus.com/inward/record.url?scp=67649289934&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=67649289934&partnerID=8YFLogxK
U2 - 10.1016/j.ssi.2009.04.018
DO - 10.1016/j.ssi.2009.04.018
M3 - Article
AN - SCOPUS:67649289934
VL - 180
SP - 1113
EP - 1117
JO - Solid State Ionics
JF - Solid State Ionics
SN - 0167-2738
IS - 17-19
ER -