Rare Earth Tungsten Electrode Applies to High Intensity Discharge Lamps

Comparing the luminescent properties of rare earth tungsten electrode and thoriated tungsten electrode in different power lighting metal halide lamp and car halide found rare earth tungsten electrodes has similar properties with thoriated tungsten electrode , which can replace radioactive thoriated tungsten electrodes using in high intensity discharge lamps, not only environmental and having good performance.

Tungsten electrode is an important component of high-intensity discharge lamps. According to the functions can be divided into cathode and an anode. The cathode is to emit electrons at a certain temperature, so that the electrodes can move to the anode, and the anode receives electrons. In alternative current, the tungsten electrode is not only as the cathode, but as the anode. In the positive half cycle it is anode and in the negative half cycle it is cathode, so in the exchange discharge lamp the electrode will be referred as cathode. Rare earth tungsten electrode used in high-intensity discharge lamps, its performance is closely related to the discharge lamp life. So rare earth tungsten electrode as cathode material can meet the following requirements: 

1. Having low work function,
2. Having good arcing performance and arcing stability;
3. Having low evaporation rate, when meets the requirement of cathode material;
4. Having stable structure, small high-temperature creep strength, electron resistance and ion bombardment resistance;
5. Having stable chemical property, the electrode will not react with filler material of lamp;
6. High intensity discharge lamps operate at temperatures above 2000K, so the electrodes so have good high temperatures property.

Rare earth tungsten electrodes production processes are as following: mixing rare earth nitrate solution with tungsten oxide by solid-liquid doping method, after reduction to obtain mixed powder. After pressed, sintered the mixed powder can obtain the blank. Then to process a series of machining can obtain rare earth tungsten electrodes. There are two ways for rare-earth doping. One is the traditional solid-liquid doping method, which is to mix rare earth nitrate solution with tungsten oxide. The second is liquid-liquid doping method, which is more effective.

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