cm4014656_si_002.cif (970.2 kB)
Long-Range-Ordered Coexistence of 4‑, 5‑, and 6‑Coordinate Niobium in the Mixed Ionic-Electronic Conductor γ‑Ba4Nb2O9
dataset
posted on 2013-08-13, 00:00 authored by Matthew T. Dunstan, Frédéric Blanc, Maxim Avdeev, Garry
J. McIntyre, Clare P. Grey, Chris D. LingIn a study combining high-resolution
single-crystal neutron diffraction
and solid-state nuclear magnetic resonance, the mixed ionic-electronic
conductor γ-Ba4Nb2O9 is shown
to have a unique structure type, incorporating niobium in 4-, 5-,
and 6-coordinate environments. The 4- and 5-coordinate niobium tetrahedra
and trigonal bipyrimids exist in discrete layers, within and among
which their orientations vary systematically to form a complex superstructure.
Through analysis and comparison of data obtained from hydrated versus
dehydrated samples, a mechanism is proposed for the ready hydration
of the material by atmospheric water. This mechanism, and the resulting
hydrated structure, help explain the high protonic and oxide ionic
conductivity of γ-Ba4Nb2O9.