Hidden chemical order in disordered Ba 7 Nb 4 MoO 20 revealed by resonant X-ray diffraction and solid-state NMR

• Published in: Nature communications 2023-04, Vol.14 (1), p.2337
• Main Authors: Yasui, Yuta, Tansho, Masataka, Fujii, Kotaro, Sakuda, Yuichi, Goto, Atsushi, Ohki, Shinobu, Mogami, Yuuki, Iijima, Takahiro, Kobayashi, Shintaro, Kawaguchi, Shogo, Osaka, Keiichi, Ikeda, Kazutaka, Otomo, Toshiya, Yashima, Masatomo
• Format: Article
• Language: English
• ISSN: 2041-1723

The chemical order and disorder of solids have a decisive influence on the material properties. There are numerous materials exhibiting chemical order/disorder of atoms with similar X-ray atomic scattering factors and similar neutron scattering lengths. It is difficult to investigate such order/disorder hidden in the data obtained from conventional diffraction methods. Herein, we quantitatively determined the Mo/Nb order in the high ion conductor Ba Nb MoO by a technique combining resonant X-ray diffraction, solid-state nuclear magnetic resonance (NMR) and first-principle calculations. NMR provided direct evidence that Mo atoms occupy only the M2 site near the intrinsically oxygen-deficient ion-conducting layer. Resonant X-ray diffraction determined the occupancy factors of Mo atoms at the M2 and other sites to be 0.50 and 0.00, respectively. These findings provide a basis for the development of ion conductors. This combined technique would open a new avenue for in-depth investigation of the hidden chemical order/disorder in materials.