ZnTaO2N: Stabilized high-temperature LiNbO3-type structure

Year: 2016 DOI: 10.1021/jacs.6b08635

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Yoshinori Kuno, Cédric Tassel, Koji Fujita, Dmitry Batuk, Artem M. Abakumov, Kazuki Shitara, Akihide Kuwabara, Hiroki Moriwake, Daichi Watabe, Clemens Ritter, Craig M. Brown, Takafumi Yamamoto, Fumitaka Takeiri, Ryu Abe, Yoji Kobayashi, Katsuhisa Tanaka, Hiroshi Kageyama.   Journal of the American Chemical Society, 2016, 138, 15950-15955.


By using a high-pressure reaction, we prepared a new oxynitride ZnTaO2N that crystallizes in a centrosymmetric (R3̅c) high-temperature LiNbO3-type structure (HTLN-type). The stabilization of the HTLN-type structure down to low temperatures (at least 20 K) makes it possible to investigate not only the stability of this phase, but also the phase transition to a noncentrosymmetric (R3c) LiNbO3-type structure (LN-type) which is yet to be clarified. Synchrotron and neutron diffraction studies in combination with transmission electron microscopy show that Zn is located at a disordered 12c site instead of 6a, implying an order–disorder mechanism of the phase transition. It is found that the closed d-shell of Zn2+, as well as the high-valent Ta5+ ion, is responsible for the stabilization of the HTLN-type structure, affording a novel quasitriangular ZnO2N coordination. Interestingly, only 3% Zn substitution for MnTaO2N induces a phase transition from LN- to HTLN-type structure, implying the proximity in energy bet...