Phase Relationships in the BaO鈥揋a2O3鈥揟a2O5 System and the Structure of Ba6Ga21TaO40

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• 作者：Jiang Cao ; Xiaodi Yu ; Xiaojun Kuang ; Qiang Su
• 刊名：Inorganic Chemistry
• 出版年：2012
• 出版时间：July 16, 2012
• 年：2012
• 卷：51
• 期：14
• 页码：7788-7793
• 全文大小：337K
• 年卷期：v.51,no.14(July 16, 2012)
• ISSN：1520-510X

文摘

Phase relationships in the BaO鈥揋a₂O₃鈥揟a₂O₅ ternary system at 1200 掳C were determined. The A₆B₁₀O₃₀ tetragonal tungsten bronze (TTB) related solution in the BaO鈥揟a₂O₅ subsystem dissolved up to 11 mol % Ga₂O₃, forming a ternary trapezoid-shaped TTB-related solid solution region defined by the BaTa₂O₆, Ba_1.1Ta₅O_13.6, Ba_1.58Ga_0.92Ta_4.08O_13.16, and Ba₆GaTa₉O₃₀ compositions in the BaO鈥揋a₂O₃鈥揟a₂O₅ system. Two ternary phases Ba₆Ga₂₁TaO₄₀ and eight-layer twinned hexagonal perovskite solid solution Ba₈Ga_4鈥?i>xTa_4+0.6xO₂₄ were confirmed in the BaO鈥揋a₂O₃鈥揟a₂O₅ system. Ba₆Ga₂₁TaO₄₀ crystallized in a monoclinic cell of a = 15.9130(2) 脜, b = 11.7309(1) 脜, c = 5.13593(6) 脜, 尾 = 107.7893(9)掳, and Z = 1 in space group C2/m. The structure of Ba₆Ga₂₁TaO₄₀ was solved by the charge flipping method, and it represents a three-dimensional (3D) mixed GaO₄ tetrahedral and GaO₆/TaO₆ octahedral framework, forming mixed 1D 5/6-fold tunnels that accommodate the Ba cations along the c axis. The electrical property of Ba₆Ga₂₁TaO₄₀ was characterized by using ac impedance spectroscopy.