Ammonium Paratungstate Preparing Lanthanum Doped Tungsten Wire 1/2

At present, production of tungsten wire is usually using ammonium paratungstate (APT) as raw material, and tungsten wire used in the bulb almost contained with potassium, aluminum, and silicon. Different impurity elements play their own roles, which are as follows:
1. Potassium (K) will hinder the lateral growth of the crystal and generate the structure of coarse long lap joint, thus significantly reduce the low temperature brittleness and splitting, and then tungsten wire with excellent anti-seismic is obtained.
2 Aluminum (Al) can greatly improve the content of K in the reduction process, thus to obtain high-quality anti-seismic tungsten wire;
3. Silicon (Si) exists at the tungsten powder surface in the form of silicate, thus to keep the sponginess of oxide coating and permeability of water in reducing process, therefore benefit for uniform doping, as well as obtaining K which is necessary.



Lanthanum (La), the number 57 atomic, which the weight of atomic is 138.9055, belongs to the lanthanides, is the most active metal in the rare earth metal. It is easily to oxidized in the air, and can be used in producing alloy, as well as the catalyst. La has two natural isotopes: NO.139 and 138 with radioactivity. A small amount of lanthanum added in tungsten production can change the components and the grain size in doped tungsten wire, thereby improving the physical properties that cold and heating resistance of tungsten wire. A method to produce micro lanthanum doped tungsten wire from ammonium paratungstate is proposed in this paper, the steps show as follows:
1. Ammonium paratungstate (APT) pre-reduced into blue tungsten oxide in the atmosphere of high purity hydrogen in a furnace;
2. Use wet-process and stirring to dope potassium, silicon, aluminum in blue tungsten oxide, then dried to generate doped blue tungsten oxide;