Lone-Pair-Induced Intra- and Interlayer Polarizations in Sillén-Aurivillius Layered Perovskite Bi4NbO8Br

Chengchao Zhong; Yui Ishii; Cédric Tassel; Tong Zhu; Daichi Kato; Kosuke Kurushima; Yukihiro Fujibayashi; Takashi Saito; Takafumi Ogawa; Akihide Kuwabara; Shigeo Mori; Hiroshi Kageyama

doi:10.1021/acs.inorgchem.2c01358

Lone-Pair-Induced Intra- and Interlayer Polarizations in Sillén-Aurivillius Layered Perovskite Bi₄NbO₈Br

Inorg Chem. 2022 Jun 27;61(25):9816-9822. doi: 10.1021/acs.inorgchem.2c01358. Epub 2022 Jun 15.

Authors

Affiliations

¹ Graduate School of Life Sciences, Ritsumeikan University, Kusatsu, Shiga 525-8577, Japan.
² Department of Materials Science, Osaka Prefecture University, Sakai, Osaka 599-8531, Japan.
³ Department of Energy and Hydrocarbon Chemistry, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto 615-8510, Japan.
⁴ Toray Research Center, Inc., Otsu, Shiga 520-8567, Japan.
⁵ Institute of Materials Structure Science, High Energy Accelerator Research Organization (KEK), Tokai, Ibaraki 319-1106, Japan.
⁶ Materials and Life Science Division, J-PARC Center, Tokai, Ibaraki 319-1195, Japan.
⁷ SOKENDAI (School of High Energy Accelerator Science, The Graduate University for Advanced Studies), Tokai, Ibaraki 319-1195, Japan.
⁸ Nanostructures Research Laboratory, Japan Fine Ceramics Center, Atsuta-ku, Nagoya 456-8587, Japan.

PMID: 35704753
DOI: 10.1021/acs.inorgchem.2c01358

Abstract

Sillén-Aurivillius layered perovskite oxyhalides Bi₄MO₈X (M = Nb, Ta; X = Cl, Br) are of great interest because of their potential as lead-free ferroelectrics in addition to their function as visible-light-responsive photocatalysts. In this work, we revisited the crystal structure of Bi₄NbO₈Br (space group: P2₁cn), revealing that the intralayer polarization is not based on the reported NbO₆ octahedral tilting but is derived from the stereochemically active Bi³⁺ lone pair electrons (LPEs) and the octahedral off-centering of Nb⁵⁺ cations. The revised structure (space group: Ic) has additional interlayer polarizations (calculated: 0.6 μC/cm²), in agreement with recent experiments on Bi₄NbO₈Br. The occurrence of polarization due to stereochemically active LPEs and Nb-site off-centering is similar to Aurivillius-type ferroelectrics (e.g., Bi₂WO₆), with comparable spontaneous polarizations in the in-plane direction (calculated: 43.5 μC/cm²). This, together with the out-of-plane polarization, indicates that Sillén-Aurivillius compounds have great potential as ferroelectric materials.