cm9b01968_si_001.pdf (3.33 MB)
Hydride Conductivity in an Anion-Ordered Fluorite Structure LnHO with an Enlarged Bottleneck
journal contribution
posted on 2019-08-23, 14:43 authored by Hiroki Ubukata, Thibault Broux, Fumitaka Takeiri, Kazuki Shitara, Hiroki Yamashita, Akihide Kuwabara, Genki Kobayashi, Hiroshi KageyamaWe report on the
hydride (H–) conductivity in fluorite-type LnHO
oxyhydrides (Ln = lanthanide) using samples prepared under high pressure.
It is found that, despite its “stoichiometric” composition,
the anion-ordered phase (Ln = La, Nd) exhibits hydride conductivity
(e.g., 2.3 × 10–5 S cm–1 for
NdHO at 300 °C), while the anion-disordered one (Ln = Gd, Er)
is an ionic insulator. The systematic structural analysis combined
with computational calculations has revealed the indirect interstitial
mechanism, where H– anions migrate between the tetrahedral
and octahedral sites through a triangular Ln3 bottleneck
expanded by the anion order, with a critical bottleneck radius of
1.18 Å. This study may offer a general guide for the design and
control of suitable anion diffusion pathways for oxyhydrides and more
generally mixed-anion compounds.