Reflection Analysis of Inorganic Electride Ca_(24)Al_(28)O_(64)~(4+)(e~-)_4 : Investigation of Electron Localization

摘要

Thermally stable inorganic electride [Ca_(24)Al_(28)O_(64)]~(4+) (e~-)_4 (C12A7:e~-) was prepared by removing oxygen ions accommodated in an anion encaging crystal C12A7 ( [Ca_(24)Al_(28)O_(64)]~(4+)(O~(2-))_2). Due to iteration nature of the encaged electron, C12A7:e~- has a high electrical conductivity ranged up to approx 140 S centre dot cm~(-1) at room temperature. The conduction mechanism of C12A7:e~- was studied by reflection analysis at room temperature in the spectral region of 0.05 - 6 eV. In addition to Lorentz-type optical responses corresponding to the transitions of electron almost localized in the sub-nanometer-sized cages of C12A7, Drude-type response due to itinerant carrier was observed This result indicates the formation of percolation path consists of cages trapping electron throughout the crystal.