Preparation and Analysis of New Phase of Calcium Aluminate Prepared by Solution Plasma Processing

Abstract

12CaO·7Al₂O₃ (so called C12A7) has been known as mayenite, which is a component of alumina cement. As the crystal is composed of positively charged nano-cages, it can clathrate several different anion species and show different outstanding properties, e.g., high oxidizing ability, high conductivity maintaining its optical transparency, catalytic reactivity for producing ammonia from nitrogen and hydrogen gases, etc., depending on the chemical species clathrated in the cates. In the present study, we focus on the newly obtained C12A7 prepared by solution plasma process and examined its phase stability and crystal structures of the unknown C12A7. TEM, XRD, TG-DTA analyses revealed the unknown C12A7 phase has large lattice parameters and small crystallite size compared to the standard (normal) C12A7 phase and is unstable in O₂ containing atmosphere, whereas is stable in H₂ atmosphere.