Functioning of traditional ceramics 12CaO·7Al2O3 utilizing built-in nano-porous structure
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- 作者：Hosono ; Hideo
- 关键词：Nanostructure ; Ceramics ; Transparent conductor ; Calcium aluminate ; Active oxygen species ; Photo-induced change ; Electride
- 刊名：Science and Technology of Advanced Materials
- 出版年：2004
- 出版时间：July, 2004
- 年：2004
- 卷：5
- 期：4
- 页码：409-416
- 全文大小：479 K
文摘
This paper briefly reviews our approach to render active functions to micro porous crystal 12CaO·7Al2O3 (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 O2− 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−, H−, and electron, aiming at emergence of novel function. C12A7:O− exhibited strong oxidation power enough to oxide Pt, and field-assisted thermionic O− emission to several μA levels, while conversion of insulator to persistent electronic conductor by illumination with ultraviolet radiation was discovered in C12A7:H− sample. Further, almost all of the free O2− ions in the cages were successfully replaced by electrons by a chemical treatment using metallic Ca. The resulting material, which has a composition [Ca24Al28O64]4+(4e−) and a high conductivity, 
100Scm−1 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.
100Scm−1 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.