A labile hydride strategy for the synthesis of heavily nitridized BaTiO3

Year: 2015 DOI: 10.1038/nchem.2370

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Takeshi Yajima, Fumitaka Takeiri, Kohei Aidzu, Hirofumi Akamatsu, Koji Fujita, Wataru Yoshimune, Masatoshi Ohkura, Shiming Lei, Venkatraman Gopalan, Katsuhisa Tanaka, Craig M. Brown, Mark A. Green, Takafumi Yamamoto, Yoji Kobayashi, Hiroshi Kageyama.   Nature Chemistry, 2015, 7, 1017-1023.


Oxynitrides have been explored extensively in the past decade because of their interesting properties, such as visible-light absorption, photocatalytic activity and high dielectric permittivity. Their synthesis typically requires high-temperature NH3 treatment (800–1,300 °C) of precursors, such as oxides, but the highly reducing conditions and the low mobility of N3− species in the lattice place significant constraints on the composition and structure—and hence the properties—of the resulting oxynitrides. Here we show a topochemical route that enables the preparation of an oxynitride at low temperatures (<500 °C), using a perovskite oxyhydride as a host. The lability of H in BaTiO3−xHx (x ≤ 0.6) allows H/N3− exchange to occur, and yields a room-temperature ferroelectric BaTiO3−xN2x/3. This anion exchange is accompanied by a metal-to-insulator crossover via mixed O–H–N intermediates. These findings suggest that this ‘labile hydride’ strategy can be used to explore various oxynitrides, and perhaps other mixed anionic compounds.