Purple Tungsten Oxide

Purple tungsten oxide, also known as tungsten purple oxide, is a typical tungsten oxide and an inorganic compound composed of 18 tungsten atoms and 49 oxygen atoms. It is an oxygen-vacancy tungsten oxide, appearing as a purple or blue-purple fine crystalline powder. Its English name is Purple Tungsten Oxide or Violet Tungsten Oxide (abbreviated as VTO or TVO), with a chemical formula of W₁₈O₄₉ or WO₂.₇₂ and a molecular weight of 227.36. Note: The oxidation state of tungsten in W₁₈O₄₉ is +5 or +6.

Structure: Purple tungsten oxide has a unique crystal structure, with each large particle consisting of loose aggregates of needle-like or rod-like grains. These aggregates contain numerous internal cracks, contributing to its exceptional physicochemical properties.

Physicochemical Properties: Purple tungsten oxide appears as a purple or blue-purple powder, with a density of 7.724-7.989 g/cm³ and an X-ray density of 7.78 g/cm³. It is soluble in ammonia and alkaline solutions but insoluble in water, alcohol, and most acids. It features a large specific surface area, high chemical reactivity, low bulk density, strong reducibility, weak oxidizing ability, excellent electrochromic properties, thermal insulation, and absorption of ultraviolet and near-infrared light.

Production Methods: The main methods for preparing purple tungsten oxide include the sealed calcination of tungsten trioxide (WO₃), hydrogen reduction of ammonium paratungstate (APT), and direct synthesis.

WO₃ Sealed Calcination: Tungsten powder and WO₃ are mixed in a specific ratio and calcined in a sealed environment.

APT Hydrogen Reduction: Under specific conditions, APT is calcined, and the decomposition of ammonia produces hydrogen, creating a reducing atmosphere that converts APT into purple tungsten oxide.

Direct Synthesis: Under controlled conditions, tungsten powder reacts with oxygen to produce purple tungsten oxide.

Applications: Purple tungsten oxide is used in manufacturing tungsten products, as a negative electrode material for lithium batteries, in the production of dimming glass, near-infrared photothermal therapeutic drugs, photocatalysts, shielding materials, fuel cell carriers, and resistive components.

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