Topochemical nitridation with anion vacancy-assisted N3-/O2- exchange

Year: 2016 DOI: 10.1021/jacs.6b00088

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Riho Mikita, Tomoko Aharen, Takafumi Yamamoto, Fumitaka Takeiri, Ya Tang, Wataru Yoshimune, Koji Fujita, Suguru Yoshida, Katsuhisa Tanaka, Dmitry Batuk, Artem M. Abakumov, Craig M. Brown, Yoji Kobayashi, Hiroshi Kageyama.   Journal of the American Chemical Society, 2016, 138, 3211-3217.


We present how the introduction of anion vacancies in oxyhydrides enables a route to access new oxynitrides, by conducting ammonolysis of perovskite oxyhydride EuTiO3-xHx (x ∼ 0.18). At 400 °C, similar to our studies on BaTiO3-xHx, hydride lability enables a low temperature direct ammonolysis of EuTi(3.82+)O2.82H0.18, leading to the N3–/H-exchanged product EuTi4+O2.82N0.120.06. When the ammonolysis temperature was increased up to 800 °C, we observed a further nitridation involving N3–/O2– exchange, yielding a fully oxidized Eu3+Ti4+O2N with the GdFeO3-type distortion (Pnma) as a metastable phase, instead of pyrochlore structure. Interestingly, the same reactions using the oxide EuTiO3 proceeded through a 1:1 exchange of N3– with O2– only above 600 °C and resulted in incomplete nitridation to EuTiO2.25N0.75, indicating that anion vacancies created during the initial nitridation process of EuTiO2.82H0.18 play a crucial role in promoting anion (N3–/O2–) exchange at high temperatures. Hence, by using (hydride-induced) anion-deficient precursors, we should be able to expand the accessible anion composition of perovskite oxynitrides.