Nano tungsten oxide, which may be applied for producing heat insulation coating, is an n-type semiconductor material and a "d0" oxide. Such two features make tungsten oxide have many advantages at the same time. Although tungsten oxide is often present in various structures such as amorphous structure, monoclinic structure, and hexagonal structure, while its main structure is composed of tungsten-oxygen octahedron connected end to end.
Depending on the crystal structures and surrounding environment, the octahedral unit will be distorted in different ways such as tilting and rotating. And it is accompanied by phenomenon that tungsten deviates from the body-centered octahedron. The existence of oxygen vacancies will have different effects on unit cell, bond length and electronic structure, resulting in changes in charge distribution, energy gap and stoichiometry. In addition, in its space skeleton, pores surrounded by tungsten-oxygen octahedron can be embedded in smaller cations to form tungsten bronze. In addition to the enhancement of electrical conductivity, this process also causes some crystal forms to undergo structural changes such as "monoclinic→tetragonal→cubic". The symmetry of tungsten oxide is rising in this process.
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