Tungsten Bronze

Tungsten bronze is a tungsten-containing nonstoichiometric compound, the outside looks like copper and has chemically inert. Tungsten bronzes is typically cubic crystal or tetragonal crystal. Insoluble in water and all acids except hydrofluoric acid, but soluble in an alkaline reagent. It can be used as a catalyst for oxidation of carbon monoxide and fuel cells getter.

A nonstoichiometric compound that empirical formula is MxWO3, and the M is typically an alkali metal, an alkaline earth metal, a rare earth metal ions, ammonium ions and so on. x is between 0 and 1. Tungsten bronzes typically have a metallic sheen and a special color. Species of M and change of the value x make it to have the properties of conductor or semiconductor. Crystal chemistry studies proved that tungsten bronze is essentially a solid solution formed after the alkali metal atoms inserted WO3 lattice. When all the vacancies are filled, the resulting compound is MWO3. The formation of tungsten bronzes is related to the tungsten’s variable atomic value, and if the space is only partially replaced by alkali metal atoms, some tungsten atoms will change from hexavalent to pentavalent.

Rare earth tungsten bronze M0.1WO3 is blue-violet powder, M is a rare earth element with a cubic crystal structure. Yttrium tungsten bronze YxWO3 has two structures of the tetragonal crystal and cubic crystal. Lithium and sodium, lithium and potassium may also form a mixed tungsten bronzes, such as NaxLiyWO3 and KxLiyWO3, where the x can be as small as 0.13, x + y can be up to 0.51. The former is usually a cubic crystal, the latter is hexagonal crystal.