Ammonium paratungstate (or APT) is a white crystalline salt of ammonium and tungsten, with the chemical formula (NH4)10(H2W12O42)·4H2O.

 

Ammonium paratungstate is produced by separating tungsten from its ore. Once the ammonium paratungstate is prepared, it is heated to its decomposition temperature, 600 °C. Left over is WO3, tungsten(VI) oxide. From there, the oxide is heated in an atmosphere of hydrogen, reducing the tungsten to elemental powder, leaving behind water vapor. From there, the tungsten powder can be fused into any number of things, from wire to bars to other shapes.

 

Coarse and spherical tungsten powders were prepared by wet hydrogen reduction. Ammonium tungstate solutions with the additives of Li, Na and K alkali metal salts were used as raw materials. The effects of the type and content of the alkali metal salts as well as reduction time on the microstructure, chemical composition, phase composition, and particle size of ammonium paratungstate (APT) and coarse tungsten powders were investigated by scanning electronic microscopy, energy dispersive spectroscopy, X-ray diffraction, and test sieves. It is shown that ideal tungsten powders with good fluidity, sphericity, integrity and even distribution can be obtained by using the ammonium tungstate solution with 3 g·L-1 NaCl, KC1 and Li2CO3 and reducing at 1000°C for 180 min in wet hydrogen atmosphere. The average particle size of the obtained tungsten powders is 67 μm, the maximum particle size is 150 μm, the biggest loose density is 13.41 g·cm-3, and the best powder flowability is 9 s for 50 g tungsten powders.