Microstructure Of Mayenite 12cao Center Dot 7al(2)O(3) And Electron Emission Characteristics

Electron emission characteristic, electrical conductivity of polycrystalline mayenite (12CaO center dot 7Al(2)O(3)) electride, formation of [Ca24Al28O64](4+)(e(-))(4) framework as a function of phase content, and microstructure have been investigated. The mayenite microstructure was investigated using high-resolution transmission microscopy which revealed the type cage structure of 12CaO center dot 7Al(2)O(3) partially filled by extra-framework oxygen ions. Incorporation of electrons by means of carbon C 2 2 - ion template 12CaO center dot 7Al(2)O(3) produces complex structure, and an incomplete C 2 2 - ion template 12CaO center dot 7Al(2)O(3) structure consisting of mixture of a [Ca24Al28O64](4+)(e(-))(4) and [Ca24Al28O64](4+)(O2-)(2) framework had a direct effect on the electron emission. Surface chemistry and stability of the 12CaO center dot 7Al(2)O(3) electride have been studied using x-ray photoelectron spectroscopy. The work function of phase pure 12CaO center dot 7Al(2)O(3) electride was determined from direct thermionic emission data and compared to the measurement from ultraviolet photoelectron spectroscopy (UPS). Depending on the extent of C 2 2 - ion template of 12CaO center dot 7Al(2)O(3) structure, a work function of 0.9-1.2 eV and 2.1-2.4 eV has been measured and thermionic emission initiating at 600 degrees C.