Orthorhombic Phase Tungsten Trioxide
Ideal crystalline structure of tungsten trioxide belongs to ReOM3, it is similar to perovskite ABO3, but W atom takes part of B, A is empty. According to simple chemical stoichiometric ratio, W:O is 1:3, its ideal crystalline structure can be seen as W atom in the center and the other six surrounded by it. Tungsten oxide octahedron (WO6) is joined by the same dome, there are many vacancies between octahedron and forms many paths. With the temperature going up, W atom in octahedron will diverge from center and cause partial deformed, and forms into many crystalline phase such as tetragonal phase, orchorhombic phase, monoclinic phase and triclinic phase.
Orthorhombic phase tungsten trioxide producing method:
1.Disolve 3.5g sodium tungstate into 20ml distilled water and mix as solution, then exchange the solution by ion exchange resin into tungstic acid hydrate solution.
2.Use 70ml glass to contain the dropped sol gel and keep stirring. When ion exchange process is nearly completed, use 30ml distilled water to clean resin.
3. Adding 4.84g citric acid into the obtained solution and mix it evenly.
4.Put glass drum into high pressure tank, seal and heat to 453k, keep the constant temperature for 24h with magnetic stirring, and finally we get orthorhombic phase tungsten trioxide.
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