TUNGSTEN METAL POWDER PRODUCTION - Reduction of Doped Tungsten Oxides- 1

5. Reduction of Doped Tungsten Oxides

Powder properties can be significantly influenced by the addition of a third element. This can be used industrially for the production of special W grades, as mentioned below.

Tungsten blue oxide is treated with aqueous solutions of the respective element compounds.

Sodium Doping. Addition of sodium compounds (concentrations equal to 50-200µ g/g Na) is a usual practice in producing coarse tungsten powder. At 1000℃ and wet conditions, average grain sizes of 10-25µm (depending on the layer height) can be attained. The high temperature guarantees the extensive evaporation of sodium at the end of the reduction process. Only for special purposes must a subsequent acid or water leach be applied to decrease the residual sodium concentration.