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Engineering Polar Oxynitrides: Hexagonal Perovskite BaWON 2
Author(s) -
OróSolé Judith,
Fina Ignasi,
Frontera Carlos,
Gàzquez Jaume,
Ritter Clemens,
Cunquero Marina,
LozaAlvarez Pablo,
Conejeros Sergio,
Alemany Pere,
Canadell Enric,
Fontcuberta Josep,
Fuertes Amparo
Publication year - 2020
Publication title -
angewandte chemie international edition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 1433-7851
DOI - 10.1002/anie.202006519
Subject(s) - perovskite (structure) , materials science , octahedron , crystallography , nitride , dipole , polar , neutron diffraction , condensed matter physics , crystal structure , chemistry , nanotechnology , physics , organic chemistry , layer (electronics) , astronomy
Non‐centrosymmetric polar compounds have important technological properties. Reported perovskite oxynitrides show centrosymmetric structures, and for some of them high permittivities have been observed and ascribed to local dipoles induced by partial order of nitride and oxide. Reported here is the first hexagonal perovskite oxynitride BaWON 2 , which shows a polar 6H polytype. Synchrotron X‐ray and neutron powder diffraction, and annular bright‐field in scanning transmission electron microscopy indicate that it crystalizes in the non‐centrosymmetric space group P6 3 mc, with a total order of nitride and oxide at two distinct coordination environments in cubic and hexagonal packed BaX 3 layers. A synergetic second‐order Jahn–Teller effect, supported by first principle calculations, anion order, and electrostatic repulsions between W 6+ cations, induce large distortions at two inequivalent face‐sharing octahedra that lead to long‐range ordered dipoles and spontaneous polarization along the c axis. The new oxynitride is a semiconductor with a band gap of 1.1 eV and a large permittivity.