As an important intermediate product of tungsten deep-processing products, tungsten oxide is a transition metal oxide composed of tungsten and oxygen elements. It has excellent thermal, mechanical, chemical and electrical properties and is widely used in energy storage batteries. , catalysts, coatings and other fields. According to the number of oxygen atoms or the valence of metal tungsten, it can be divided into tungsten trioxide and tungsten dioxide. They have certain differences in physical and chemical properties, production process and application.
Tungsten Dioxide (WO2) Is Different From Tungsten Trioxide (WO3)
Tungsten trioxide is an oxide composed of 1 tungsten atom and 3 oxygen atoms. It is a yellow or bright green powder, so it is also called yellow tungsten oxide. The English name is Tungsten Trioxide. The molecular formula is WO3 and the molecular weight is 231.85. The valence of tungsten is +6.
Tungsten dioxide is an oxide composed of 1 tungsten atom and 2 oxygen atoms. It is a brown powder, so it is also called brown tungsten oxide. The English name is Tungsten Dioxide. The molecular formula is WO2 and the molecular weight is 215.84. has a valence of +4.
Tungsten Dioxide (WO2) and Tungsten Trioxide (WO3) Have Different Structures
The crystal structure of WO3 is similar to the octahedral structure of the perovskite structure, and the tungsten atom is located at the geometric center of the octahedron. Its temperature from zero to melting point is 1700K, and there are four crystal forms: monoclinic phase, triclinic phase, orthorhombic phase, and tetragonal phase.
The crystal structure of WO2 is rutile structure (monoclinic system), which exhibits distorted WO6 octahedral centers, interphase short W–W bonds at 248pm, and space group P21/c.
Physical and Chemical Properties of Tungsten Dioxide (WO2) and Tungsten Trioxide (WO3) Are Different
The appearance of WO3 is yellow or bright green powder, the melting point is 1473°C, the boiling point is higher than 1750°C, the density is 7.16g/cm3, the bulk specific gravity is 2.3~2.8g/cm3, it is insoluble in water and inorganic substances except hydrofluoric acid Acid, soluble in alkaline solution, has high oxidation, good electrochromic, photochromic and gas-sensitivity advantages.
The appearance of WO2 is tan powder, with a melting point of about 1600°C, a boiling point of about 1730°C, a density of about 11g/cm³, a heat of formation of 134 kcal/mol, volatile at 1050°C, an electronic conductivity of about 3.5×102S/cm, and insoluble in water , Alkaline solution, hydrochloric acid and dilute sulfuric acid, has good conductivity, reduction and oxidation.
Production Process of Tungsten Dioxide (WO2) And Tungsten Trioxide (WO3) Is Different
The production methods of tungsten trioxide include hydrochloric acid decomposition of tungstate, thermal decomposition of ammonium paratungstate, hydrothermal synthesis, precipitation, sol-gel method, microemulsion, gas-liquid reaction method, template method, etc.
Production of tungsten dioxide: under vacuum conditions, heat the mixed tungsten powder and tungsten trioxide to 950°C.
Tungsten Dioxide (WO2) and Tungsten Trioxide (WO3) Have Different Uses
Both WO3 and WO2 can be used to produce other tungsten products such as metal tungsten powder and tungsten alloy, as well as negative electrode materials for lithium batteries. It is worth mentioning that WO3 can also be used to make gas sensors, thermal insulation coatings, catalysts and invisible materials.
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