Differences in cage deformation and extra-framework anion distribution between O²⁻ and OH⁻-incorporated 12CaO7Al₂O₃ crystals

Abstract

Effects of O²⁻ or OH⁻-ion incorporation on the cage geometry in 12CaO7Al₂O₃ (C12A7) crystals are investigated by the Maximum Entropy Method (MEM)/Rietveld analyses of synchrotron powder X-ray diffraction data measured in SPring-8. The OH⁻ ion is located at the cage center and symmetrically attracts two axially-coordinated Ca ions, while, the O²⁻ ion is likely located at off-center positions and induces larger asymmetric Ca ion displacement.