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Cathode material

In the electric light source industry, the direct light source is called a filament. For example, the direct light source in an incandescent bulb is made of metal tungsten processed into a filament. When the current passes through the tungsten filament, it consumes a certain amount of electrical power and converts it into heat energy, so that the tungsten filament is heated to an incandescent state and emits strong light. In gas discharge lamps, although some tungsten materials are also processed into filament shapes, they are not used as the light source of the lamp, but as base metal to support, store and heat the electron emission material, so they are called electrodes, such as low-pressure fluorescent lamps, low-pressure sodium lamps, high-pressure mercury lamps, high-pressure sodium lamps, and electrodes in metal halide lamps. In the gas discharge lamp series, some electrodes are made of tungsten doped with other impurity materials. They are not processed into filament shapes, but into cylinders or cylindrical cones, and are still not directly used as light sources; such as electrodes of Xenon Lamps and other types.

The necessary condition for gas discharge lamps is that there must be corresponding electrodes. In gas discharge lamps, the electrode that emits electrons is often called the cathode, and the electrode that receives electrons is called the anode. Most discharge lamps work under alternating current, and the two electrodes alternately act as cathodes and anodes, so they are generally called cathodes. Only gas discharge lamps working under direct current are designed with cathodes and anodes of different shapes.

The cathode is a very important component in gas discharge lamps. Its characteristics and lifespan largely determine the main characteristics and lifespan of gas discharge lamps. The failure of many gas discharge lamps is often caused by the damage and end of life of the cathode. The cathode characteristics mainly depend on the electron emission material it uses. Therefore, when selecting the electrode material for gas discharge lamps, the physical and chemical properties of the selected materials, such as thermal electron emission performance, anti-poisoning ability, and ion bombardment resistance, should be fully understood to find suitable electrode materials and the best decomposition and activation process to increase the life of the discharge lamp.

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