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Microstructure of mayenite 12CaO·7Al 2 O 3 and electron emission characteristics
Author(s) -
Sayir Ali,
Berger MarieHélène,
Back Tyson C.,
Mackey Jonathan
Publication year - 2021
Publication title -
journal of the american ceramic society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.9
H-Index - 196
eISSN - 1551-2916
pISSN - 0002-7820
DOI - 10.1111/jace.17925
Subject(s) - x ray photoelectron spectroscopy , microstructure , chemistry , thermionic emission , work function , analytical chemistry (journal) , ion , crystallite , spectroscopy , transmission electron microscopy , crystallography , materials science , electron , nanotechnology , chemical engineering , electrode , physics , organic chemistry , quantum mechanics , chromatography , engineering
Electron emission characteristic, electrical conductivity of polycrystalline mayenite (12CaO·7Al 2 O 3 ) electride, formation of [Ca 24 Al 28 O 64 ] 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·7Al 2 O 3 partially filled by extra‐framework oxygen ions. Incorporation of electrons by means of carbon C 2 2 ‐ion template 12CaO·7Al 2 O 3 produces complex structure, and an incomplete C 2 2 ‐ion template 12CaO·7Al 2 O 3 structure consisting of mixture of a [Ca 24 Al 28 O 64 ] 4+ (e − ) 4 and [Ca 24 Al 28 O 64 ] 4+ (O 2− ) 2 framework had a direct effect on the electron emission. Surface chemistry and stability of the 12CaO·7Al 2 O 3 electride have been studied using x‐ray photoelectron spectroscopy. The work function of phase pure 12CaO·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·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°C.