Tungsten Electrode Preparation with Rare Earth Doped Tungsten Powder

Tungsten is one of the widely used electrode materials. However, due to the low emission efficiency of pure metal tungsten electrode, and Recrystallization at high temperature to form equiaxed grain structure, the tungsten wire sags and breaks. Therefore, tungsten electrode can be widely used in various kinds of small and medium vacuum electronic devices, but it can not meet the requirements of high power microwave devices with high current density and long life.

A method for preparing rare earth doped tungsten powders is proposed, which can be used to fabricate rare earth tungsten electrodes. The method includes the following steps:

(1)The mixture of 10mL 200g/L lanthanum nitrate solution and 129mL 250g/L ammonium metatungstate solution (approximate to 94% of tungsten trioxide in metatungstic amine) was evenly mixed, and then stirred at a speed of 500 rpm/min. During the stirring process, 22mL 100g/L oxalic acid solution was added. The ratio of rare earth salt to oxalic acid was 1:4. ;

(2)The pH value of the mixed solution in step (1) was adjusted to 0.8 with HNO₃, and then placed in a high-pressure reactor for 16 hours at 10 MPa and 180 ℃ for hydrothermal reaction, filtration, washing and drying to obtain the composite powders of rare earth oxides and tungsten oxide.

(3)The composite powders in step (2) are placed in hydrogen atmosphere for reduction reaction. The reduction reaction is divided into two stages: the first stage, the reduction temperature is 550 ℃, the reaction time is 2.0 hours, the second stage, the reduction temperature is 800 C, and the reaction time is 2.5 hours. The rare earth doped tungsten powders are obtained.

For the prepared rare earth doped tungsten powder, the grain size of the alloy is obviously refined and the density can reach 99.2%. The rare earth oxide is dispersed at the grain boundary of the material, which hinders the migration of W interface, and makes it have good mechanical properties with bending strength up to 540 MPa. As an electrolyte, it has low ablative property, good surface work escape and low electronic capacitance. Easy to escape from the surface, good welding and burning resistance.

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