Synthesis of a Room Temperature Stable 12CaO·7Al2O3 Electride from the Melt and Its Application as an Electron Field Emitter
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- 作者：Sung Wng Kim ; Yoshitake Toda ; Katsuro Hayashi ; Masahiro Hirano ; and Hideo Hosono
- 刊名：Chemistry of Materials
- 出版年：2006
- 出版时间：April 4, 2006
- 年：2006
- 卷：18
- 期：7
- 页码：1938 - 1944
- 全文大小：422K
- 年卷期：v.18,no.7(April 4, 2006)
- ISSN：1520-5002
文摘
A room temperature (RT) stable electride was realized by thermally annealing an insulating 12CaO·7Al2O3 (C12A7) single crystal in a calcium metal vapor. Here we report a simple and direct method forsynthesizing polycrystalline C12A7 electride (C12A7:e-); the solidification of a "melt" in a reducingatmosphere and the crystallization of a "glass" with an oxygen-deficient composition in a vacuum. Thecarbon-related anion (C22-) presumably serves as the template for the formation of the C12A7 phase inthe solidification process and may be spontaneously released from the lattice during the cooling process,leaving mobile electrons in the lattice. Also the C22- ions accommodated in the glass may play a significantrole in the formation of C12A7:e- during the crystallization. The polycrystalline C12A7:e- exhibits anelectrical conductivity up to 5 S·cm-1 at 300 K, which corresponds to an electron concentration of ~3× 1019 cm-3 and a nearly equal mobility of ~0.1 cm2·V-1·s-1 to that of the single crystalline C12A7:e-.A large current density of ~12 
A·cm-2 is obtained in the electron field emission from a flat surface ofthe polycrystalline C12A7:e- with a work function of ~0.6 eV for an applied electric field of 2.4 × 105V·cm-1. These simple synthetic methods make it possible to produce efficiently the electride in largevolume, which will facilitate the C12A7:e- research, paving a way for various applications includingcold electron emission.
A·cm-2 is obtained in the electron field emission from a flat surface ofthe polycrystalline C12A7:e- with a work function of ~0.6 eV for an applied electric field of 2.4 × 105V·cm-1. These simple synthetic methods make it possible to produce efficiently the electride in largevolume, which will facilitate the C12A7:e- research, paving a way for various applications includingcold electron emission.