Structure and electrons in mayenite electrides

Single-crystal low-temperature synchrotron X-ray diffraction is used for providing an accurate structural study for three members of the series [[Ca.sub.12][Al.sub.14][O.sub.32]][O.sub.1-[delta]][e.sub.2[delta]] ([delta] = 0, 0.15, and 0.45). The studies have indicated that the final electron density map for [delta] = 0.45 black mayenite has shown electron density localized into the center of the cages, which is the first experimental proof of their electride nature.