Microstructure of mayenite 12CaO·7Al2O3 and electron emission characteristics

Electron emission characteristic, electrical conductivity of polycrystalline mayenite (12CaO·7Al2O3) 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 tr...

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Bibliographic Details
Published in:Journal of the American Ceramic Society 2021-11, Vol.104 (11), p.5750-5763
Main Authors: Sayir, Ali, Berger, Marie‐Hélène, Back, Tyson C., Mackey, Jonathan
Format: Article
Language:English
Subjects:
Calcium aluminate
cathode materials
electrical properties
Electrical resistivity
Electron emission
electron microscopy
Electrons
Microstructure
Oxygen ions
Photoelectron spectroscopy
Photoelectrons
Surface stability
Thermionic emission
Work functions
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Summary:Electron emission characteristic, electrical conductivity of polycrystalline mayenite (12CaO·7Al2O3) 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·7Al2O3 partially filled by extra‐framework oxygen ions. Incorporation of electrons by means of carbon C22‐ ion template 12CaO·7Al2O3 produces complex structure, and an incomplete C22‐ ion template 12CaO·7Al2O3 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·7Al2O3 electride have been studied using x‐ray photoelectron spectroscopy. The work function of phase pure 12CaO·7Al2O3 electride was determined from direct thermionic emission data and compared to the measurement from ultraviolet photoelectron spectroscopy (UPS). Depending on the extent of C22‐ ion template of 12CaO·7Al2O3 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°C.
ISSN:0002-7820
1551-2916
DOI:10.1111/jace.17925