Structure characteristics and crystal synthesis of sodium tungsten bronze with different W structure oxidation degrees
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P578.91

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    Abstract:

    NaxWO3 (0 ≤ x ≤ 1) has received increasing attention from experts due to its special physicochemical properties. It is a non-stoichiometric W-containing compound with the tunnel structure, and Na+ filled in the secondary structural tunnels produced by the connection of octahedron. With the increase of x, the average oxidation degree of W decreases gradually, NaxWO3 undergoes monoclinic-orthogonal-tetragonal Ⅰ (space group I4/nmm)-hexagonal-tetragonal Ⅱ (space group P4/mbm)-cubic crystal structure transformation. Structural symmetry gradually increases except for the tetragonal Ⅱ type. In this paper, the structural characteristics of sodium tungsten bronze with di-fferent W oxidation degrees were systematically studied from the perspective of crystal chemistry. The tetragonal and cubic phase sodium tungsten bronze was obtained by solid phase synthesis, and the hexagonal tungsten bronze was obtained by hydrothermal synthesis. Experimental results show that, in the solid phase synthesis process, the more the reducing agent NaBH4, the more the reduction of W to a lower valence state, and the easier the conversion of the NaxWO3 from the tetragonal to cubic structure. At the same reduction dose, the higher the synthesis temperature, the higher the symmetry of the obtained sodium tungsten bronze. The temperature of synthetic cubic sodium tungsten bronze is 700~850℃, which is higher than the synthesis temperature of tetragonal sodium tungsten bronze (600~700℃); the synthesis reaction requires appropriate pH value, the pH value is controlled at around 6 when tetragonal and cubic sodium tungsten is synthesized, and the pH value of the hydrothermally synthesized hexagonal sodium tungsten bronze is preferably around 2. The result obtained by the authors provides a reference for sodium tungsten bronze series compounds and the synthesis of different structures of sodium tungsten bronze.

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李灵慧,李艳,黎晏彰,鲁安怀,丁竑瑞,2020,不同W氧化度钠钨青铜的结构特征与合成方法探究[J].岩石矿物学杂志,39(2):195~202. LI Ling-hui, LI Yan, LI Yan-zhang, LU An-huai, DING Hong-rui,2020,Structure characteristics and crystal synthesis of sodium tungsten bronze with different W structure oxidation degrees[J]. Acta Petrologica et Mineralogica,39(2):195~202.

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History
  • Received:September 07,2019
  • Revised:November 26,2019
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  • Online: March 10,2020
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