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首页> 外文期刊>Dalton transactions: An international journal of inorganic chemistry >Effect of isothermal holding time on hydrogen-induced structural transitions of WO3
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Effect of isothermal holding time on hydrogen-induced structural transitions of WO3

机译：等温控时间对WO3氢诱导结构转变的影响

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摘要

Tungsten trioxide (WO3) has the ability to transform oxygen-deficient structures (WO3-x; 0 <= x <= 1) at high temperatures under hydrogen. Because the band gap of WO3-x depends on the amount of W5+ species resulting from oxygen vacancies, this material is expected to have unique applications. Herein, to elucidate the WO3 reduction mechanism, we investigated the crystallographic changes of monoclinic WO3 powder samples using X-ray and neutron diffraction measurements under different reduction conditions, namely, under hydrogen at 500 or 800 degrees C for isothermal holding times of 30 min or 22 h. During heating, the yellow color of WO3 changed to various other colors, suggesting that WO3 underwent different reactions with hydrogen depending on the temperature and isothermal holding time. The X-ray powder diffraction results indicated that the hydrogen-treated WO3 crystals formed various oxygen-deficient structures, including stoichiometric WO3-x, non-stoichiometric WO3-x, and W metal. However, the formation of a single WO3-x phase was extremely difficult. For the blue WO3 sample obtained at short isothermal holding times, the total scattering analysis suggested that the oxygen vacancies in WO3 gradually formed at local positions. Furthermore, the neutron powder diffraction measurements revealed that the reduction of WO3 under hydrogen occurred on the surface. These results obtained by diffraction measurements enhance the knowledge in the chemical and physical properties of WO3-x.
机译：三氧化钨（WO3）具有在高温下氢下转化缺氧结构（WO3-x；0<=x<=1）的能力。由于WO3-x的带隙取决于氧空位产生的W5+物种的数量，因此这种材料有望有独特的应用。在此，为了阐明WO3还原机理，我们研究了单斜WO3粉末样品在不同还原条件下的晶体学变化，即在500或800摄氏度的氢气下等温30分钟或22小时。在加热过程中，WO3的黄色变为各种其他颜色，这表明WO3与氢发生了不同的反应，这取决于温度和等温时间。X射线粉末衍射结果表明，氢处理后的WO3晶体形成了各种缺氧结构，包括化学计量比WO3-X、非化学计量比WO3-X和钨金属。然而，单一WO3-x相的形成极其困难。对于在较短等温时间下获得的蓝色WO3样品，总散射分析表明WO3中的氧空位在局部位置逐渐形成。此外，中子粉末衍射测量表明，WO3在氢下的还原发生在表面。通过衍射测量获得的这些结果增强了对WO3-x的化学和物理性质的了解。

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