Tungsten bronze (TB) is a typical non-stoichiometric compound, usually in the form of cubic or tetragonal crystal, insoluble in water and all acids except hydrofluoric acid, but soluble in an alkaline reagent. Its chemical formula can be written as MxWO3(x=0~1), wherein M is a common first and second main group elements and rare earth elements tungsten bronze. Variety of M and changing the value of x, TB will get conductor or semiconductor property. Crystal chemistry studies have shown that tungsten bronze is essentially an alkali metal atom inserted WO3 lattice to form a solid solution. When all the vacancies are filled, the resulting compound is MWO3. The formation of tungsten bronzes is related with tungsten variable valence, if the vacancy is partly replaced by the alkali metal atoms, then portion of the pentavalent tungsten will change into valence of six.
Tungsten bronze has a special tunnel space structure, according to the crystal structure, usually can be divided into perovskite tungsten bronzes (PTB), tetragonal tungsten bronze (TTB), hexagonal tungsten bronze (HTB) and symbiotic structure tungsten bronze (ITB).
The preparation methods of tungsten bronze are wet chemical, thermal reduction, electrochemical and other methods; wherein wet chemical method is the earliest used, and because of its relatively low synthesis temperature, the better product crystallized state and other advantages to become hot in the synthesis studying, but industrial production is still rare.