posted on 2017-09-19, 14:08authored byDong Jiang, Zeyu Zhao, Shenglong Mu, Vincent Phaneuf, Jianhua Tong
Mayenite (12CaO·7Al2O3, C12A7) electride with an anti-zeolite nanoporous
structure has attracted intense attention due to its versatile promising
application potentials. However, the synthesis difficulty because
of extremely harsh conditions (e.g., reduction in sealed calcium or
titanium vapor) significantly obstructs its realistic applications.
In this work, we employed a simple, efficient, and cost-effective
route for synthesizing mayenite electrides (C12A7:e–) in both powder and dense ceramic. C12A7:e– powders
with efficient electron doping (3.5 × 1020 cm–3) were obtained via simple graphite reduction of a
novel mixture precursor of CaAl2O4 (CA) and
Ca3Al2O6 (C3A) derived from a modified
Pechini method. The structural evolution during the electride formation
was investigated, and it was found that reduction below 1300 °C
induced the formation of Ca5Al6O14 (C5A3), while reduction above 1400 °C helped retain the mayenite
structure. Fully dense C12A7:e– ceramics were also
fabricated via graphite reduction of presintered pellets with a relative
density of 97.9% starting from the CA+C3A mixture. Careful studies
improved the mechanism cognition of graphite treatment that the electrons
injection was probably initiated by surface reduction with involatile
C species (e.g., C22–) rather than previously
proposed CO, during which the mixed conduction of oxygen ions and
electrons played an important role. Furthermore, the stability of
C12A7:e– in water as well as in the presence of
moisture was discussed. These results not only suggest a novel precursor
for fabricating high-quality mayenite electrides but also provide
in-depth insights into the stability of the mayenite structure toward
practical applications.