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Introduction to Tungsten Oxide

wallpapers News 2021-02-05
Tungsten oxide is also called tungsten, and its chemical formula is WO3. Light yellow orthorhombic crystals, the color darkens when heated, and returns to light yellow after cooling. It is stable in air, with a melting point of 1473°C, a boiling point higher than 1750°C, and a relative density of 7.16. It is insoluble in water and inorganic acids other than hydrofluoric acid, but soluble in hot concentrated sodium hydroxide solution and ammonia. Tungsten oxide is not only an n-type semiconductor material but also a "d0" oxide. This dual identity makes it possess many characteristics at the same time. Although it usually exists in various forms such as amorphous, monoclinic and hexagonal, its mainframe is composed of tungsten oxide octahedrons connected end to end.
Structural changes of tungsten oxide
Depending on the type of crystal and the surrounding environment, the octahedral unit will be twisted in different ways (such as tilt and rotation), and there will also be a phenomenon where tungsten deviates from the center of the octahedron. The presence of oxygen vacancies will affect the unit cell, bond length and electronic structure to varying degrees, resulting in changes in charge distribution, energy gap and stoichiometric ratio. In addition, in its space frame, holes surrounded by tungsten oxide octahedrons can be inserted into smaller cations to form tungsten bronze. In addition to increasing electrical conductivity, this process will also cause certain crystal forms to undergo configuration transformations with higher and higher symmetry, such as "monoclinic, tetragonal and cubic crystals."
Features of tungsten oxide
These special properties make tungsten oxide possess catalytic, optical and electrical properties at the same time, and it can be expected to be used in many fields, such as hydrogenolysis, secondary lithium batteries, gas sensors, etc. It is worth noting that the transformation process of reversible tungsten oxide and tungsten bronze is always accompanied by the transfer of internal electrons and the change of tungsten valence, thereby triggering a color reaction and achieving controllable adjustment of transmitted light. This function was first discovered in 1969 and has since been widely used in electrochromic fields, such as smart car windows, car rearview mirrors and large-area information displays.
 
Colored tungsten oxide has a deep blue color and is suitable for daily household use due to its softer color and better shade. In addition, crystalline tungsten oxide has high reflectivity to infrared rays after discoloration and can achieve a heat insulation effect similar to that of Low-E glass, thereby helping to reduce indoor energy consumption. As a new type of functional material, tungsten oxide has the characteristics of low production cost, easy synthesis, low energy consumption, wide viewing angle, high coloring efficiency, strong color difference, long life and good stability. An electrochromic. Research hotspots in this field.

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