Solid-state synthesis in the system Na_0.8Nb_yW_1−yO₃ with 0y0.4: A new phase, Na_0.5NbO_2.75, with perovskite-type structure

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• 作者：Tapas Debnath ; Claus H. Rü ; scher ; Thorsten M. Gesing ; Jü ; rgen Koepke ; Altaf Hussain
• 关键词：Tungsten bronze ; Perovskite
• 刊名：Journal of Solid State Chemistry
• 出版年：2008
• 出版时间：April 2008
• 年：2008
• 卷：181
• 期：4
• 页码：783-788
• 全文大小：615 K

文摘

Series of compounds in the system Na_xNb_yW_1−yO₃ were prepared according to the appropriate molar ratio of Na₂WO₄, WO₃, WO₂ and Nb₂O₅ with x=0.80 and 0.0y0.4 at 600 °C in evacuated silica glass tubes. These compounds were investigated by X-ray powder diffraction, optical microscopy, microprobe analysis, Raman and optical microspectroscopy. A y-dependent separation into three distinct coloured crystallites with cubic perovskite-type structures is observed: (i) red-orange crystallites with composition Na_xWO₃ with slightly decreasing x (i.e. 0.8–0.72) with increasing nominal y, (ii) bluish solid solution of composition Na_xNb_yW_1−yO₃ and (iii) white crystallites of a new phase having defect perovskite-type structure with composition Na_0.5NbO_2.75.