Browsing by Author "Nagao, M"

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    Growth of LiCoO2 single crystals by the TSFZ method
    (American Chemical Society, 2018-11-08) Nakamura, S; Maljuk, A; Maruyama, Y; Nagao, M; Watauchi, S; Hayashi, T; Anzai, Y; Furukawa, Y; Ling, CD; Deng, G; Avdeev, M; Büchner, B; Tanaka, I
    We have grown LiCoO2 single crystals by the traveling solvent floating zone (TSFZ) growth with Li-rich solvent, having observed the incongruent melting behavior of LiCoO2 between 1100 and 1300 °C. The optimum growth conditions in terms of atmosphere and solvent composition were determined to be Ar flow and an atomic ratio Li/Co 85:15, respectively. The crystals grown using a conventional-mirror-type furnace contained periodic inclusions of a Co–O phase due to the influence of Co–O phase segregation on the stability of the molten zone during growth. By using a tilted-mirror FZ furnace, inclusion-free LiCoO2 crystals of about 5 mm in diameter and 70 mm long were obtained at a tilting angle θ = 10°. The grown crystals were confirmed to be single-domain by neutron Laue diffraction. © 2018 American Chemical Society
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    Nitrogen-rich molybdenum nitride synthesized in a crucible under air
    (American Chemical Society, 2024-03-05) Demura, M; Nagao, M; Lee, CH; Goto, Y; Nambu, Y; Avdeev, M; Masubuchi, Y; Mitsudome, T; Sun, W; Tadanaga, K; Miura, A
    The triple bond in N2 is significantly stronger than the double bond in O2, meaning that synthesizing nitrogen-rich nitrides typically requires activated nitrogen precursors, such as ammonia, plasma-cracked atomic nitrogen, or high-pressure N2. Here, we report a synthesis of nitrogen-rich nitrides under ambient pressure and atmosphere. Using Na2MoO4 and dicyandiamide precursors, we synthesized nitrogen-rich γ-Mo2N3 in an alumina crucible under an ambient atmosphere, heated in a box furnace between 500 and 600 °C. Byproducts of this metathesis reaction include volatile gases and solid Na(OCN), which can be washed away with water. X-ray diffraction and neutron diffraction showed Mo2N3 with a rock salt structure having cation vacancies, with no oxygen incorporation, in contrast to the more common nitrogen-poor rock salt Mo2N with anion vacancies. Moreover, an increase in temperature to 700 °C resulted in molybdenum oxynitride, Mo0.84N0.72O0.27. This work illustrates the potential for dicyandiamide as an ambient-temperature metathesis precursor for an increased effective nitrogen chemical potential under ambient conditions. The classical experimental setting often used for solid-state oxide synthesis, therefore, has the potential to expand the nitride chemistry. © 2024 American Chemical Society.