Microstructure of mayenite 12CaO·7Al2O3 and electron emission characteristics. Issue 11 (29th June 2021)

• Record Type: Journal Article
• Authors: Sayir, Ali; Berger, Marie‐Hélène; Back, Tyson C.; Mackey, Jonathan
• Is Part Of: Journal of the American Ceramic Society. Volume 104:Issue 11(2021)
• Page Start: 5750
• Page End: 5763
• Publication Date: 2021-06-29
• Subjects: cathode materials -- electrical properties -- electron microscopy; Ceramics -- Periodicals; 620.1405
• DOI: 10.1111/jace.17925
• Languages: English
• ISSNs: 0002-7820

Abstract

Abstract: Electron emission characteristic, electrical conductivity of polycrystalline mayenite (12CaO·7Al2 O3 ) electride, formation of [Ca24 Al28 O64 ] 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·7Al2 O3 partially filled by extra‐framework oxygen ions. Incorporation of electrons by means of carbon C 2 2 ‐ ion template 12CaO·7Al2 O3 produces complex structure, and an incomplete C 2 2 ‐ ion template 12CaO·7Al2 O3 structure consisting of mixture of a [Ca24 Al28 O64 ] 4+ (e − )4 and [Ca24 Al28 O64 ] 4+ (O 2− )2 framework had a direct effect on the electron emission. Surface chemistry and stability of the 12CaO·7Al2 O3 electride have been studied using x‐ray photoelectron spectroscopy. The work function of phase pure 12CaO·7Al2 O3 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·7Al2 O3 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.