Currently, the barium-tungsten which is widely used in the magnetron is limited, due to the strong electronic back in the device which makes the consumption of BaO is too fast and thus to result in the decrease of the device’s life; moreover, the secondary electron emission ability of it is difficult to meet the requirement of high power microwave device. Furthermore, due to the radioactive problem of Th, it is already suitable for some of the high power magnetron ThO₂ cathode. Study found that even through the rare earth - molybdenum metal ceramic cathode materials has a stable secondary electron emission performance, but its thermal emission performance is poor, and requires a higher temperature in magnetron start up, and thus to limit its using in the magnetron. 

For this, an invention has developed a method which takes ammonium metatungstate (AMT) as raw material, rare earth element yttrium, lanthanum as additives, taken Y₂O₃ - La₂O₃ binary system composite barium-tungsten cathode, the steps are as follows: 

1. Weight a certain amount of ammonium metatungstate as raw materials to dissolve in deionized water to form AMT solution; 

2. Add the yttrium nitrate, lanthanum nitrate, barium nitrate, aluminum nitrate and calcium nitrate solution into AMT aqueous solution, wherein, the mass of rare earth oxide composite of Y₂O₃ and La₂O₃ is taking 5-20% wt of the total mass of cathode materials, total weight of ternary nitrate is taking 5 ~ 15% wt of the total weight of cathode materials; 

3. Add the citric acid solution, then put it in a water bath of 70 ~ 90°C until the sol is formed, and followed with a dry under the temperature of 100 ~ 150°C until the gel is formed; 

4. Decompose the gel obtained in step 3 under 500 ~ 600°C in the atmosphere for 2 ~ 4 hours; 

5. reduce the decomposed powder under a hydrogen atmosphere, which is divided into two steps, the first step in the reduction temperature of 450 ~ 550°C, insulation for2 ~ 4 hours; The second step is under 750 ~ 950°C, insulation for 1 ~ 2 hours, then the reduced powder is suppressed under the pressing pressure of 1 ~ 3 t/cm2, with the sintering temperature of 1450 ~ 1650°C, and insulation for 1 ~ 5 min, to finally be sintered into cathode, which is the barium-tungsten cathode. 

 

This kind of tungsten based of electron emission material which contains rare earth oxide and active salt (barium calcium aluminate) concentrates the advantages of both barium-tungsten cathode and rare earth - molybdenum ceramic cathode; moreover, in the case of thermal emission does not decrease, Y₂O₃-La₂O₃ system compound-pressed barium-tungsten cathode has the better secondary electron emission property.