Tungsten trioxide powder for liquid electrochromic device is a transition metal oxide with many special physical properties. This is because WO3 has a multi-phase transition and exhibits ferroelectricity. However, why is the chemical formula of tungsten trioxide usually written in the form of WO3-x rather than the form of WO3? The following are the answers from experts.
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The crystal structure of the tungsten trioxide which strictly satisfies the stoichiometric ratio should be a distorted perovskite structure, that is, the absence of the A cation in the perovskite structure of the ABO3 form. The oxygen atom constitutes a regular octahedron, and a tungsten atom is located in the center of this regular octahedron. Since there is always a certain degree of oxygen vacancies in the WO3 material in practice, the chemical formula of tungsten trioxide is generally written in the form of WO3-x, but not in the form of WO3.
