You searched for: “thermionic emission
thermionic emission
1. The emission of electrons or ions by substances that are highly heated, the charged particles being called thermions.
2. The discharge of electrons or ions from a solid or liquid as a result of its thermal energy.
3. The release of electrons when a material is heated; for example, electron emission when the tungsten cathode filament of a radiographic tube is heated to incandescence (emission of light by an object as a result of its being heated to a high temperature) by means of its low-voltage heating circuit.