Thermally induced flow of charge carriers from a surface
"Thermion" redirects here. Not to be confused with fermion.
Closeup of the filament in a low pressure mercury gas-discharge lamp showing white thermionic emission mix coating on the central portion of the coil. Typically made of a mixture of barium, strontium and calcium oxides, the coating is sputtered away through normal use, eventually resulting in lamp failure.One of the bulbs with which Edison discovered thermionic emission. It consists of an evacuated glass light bulb containing a carbon filament (hairpin shape), with an additional metal plate attached to wires emerging from the base. Electrons released by the filament were attracted to the plate when it had a positive voltage.
Thermionic emission (also known as thermal electron emission or the Edison effect) is the liberation of electrons from an electrode by virtue of its temperature (releasing of electrons supplied by heat). This occurs because the thermal energy given to the charge carrier overcomes the work function of the material. The charge carriers can be electrons or ions, and in older literature are sometimes referred to as thermions. After emission, a charge that is equal in magnitude and opposite in sign to the total charge emitted is initially left behind in the emitting region. But if the emitter is connected to a battery, the charge left behind is neutralized by charge supplied by the battery as the emitted charge carriers move away from the emitter, and finally the emitter will be in the same state as it was before emission.
The classical example of thermionic emission is that of electrons from a hot cathode into a vacuum in a vacuum tube. The hot cathode can be a metal filament, a coated metal filament, or a separate structure of metal or carbides or borides of transition metals. Vacuum emission from metals tends to become significant only for temperatures over 1,000 K (730 °C; 1,340 °F).
This process is crucially important in the operation of a variety of electronic devices and can be used for electricity generation (such as thermionic converters and electrodynamic tethers) or cooling. The magnitude of the charge flow increases dramatically with increasing temperature.
The term 'thermionic emission' is now also used to refer to any thermally-excited charge emission process, even when the charge is emitted from one solid-state region into another.
and 30 Related for: Thermionic emission information
Thermionicemission (also known as thermal electron emission or the Edison effect) is the liberation of electrons from an electrode by virtue of its temperature...
difference has been applied. The type known as a thermionic tube or thermionic valve utilizes thermionicemission of electrons from a hot cathode for fundamental...
or field enhanced thermionicemission is a phenomenon in condensed matter physics named after Walter H. Schottky. In electron emission devices, especially...
radius of about 100 nm, or of the Schottky type,: 1–28 in which thermionicemission is enhanced by barrier lowering in the presence of a high electric...
as a form of field emission. The terminology is historical because related phenomena of surface photoeffect, thermionicemission (or Richardson–Dushman...
in the vacuum are excluded in defining the work function. Thermionicemission In thermionic electron guns, the work function and temperature of the hot...
tubes, a hot cathode or thermionic cathode is a cathode electrode which is heated to make it emit electrons due to thermionicemission. This is in contrast...
experiment Emission theory (vision), the proposal that visual perception is accomplished by rays of light emitted by the eyes Thermionicemission, the flow...
discharge is initiated either by thermionicemission or by field emission. After initiation, the arc relies on thermionicemission of electrons from the electrodes...
the surface, an effect called thermionicemission. This technique is used in most vacuum tubes. Field electron emission: A strong electric field can be...
due to the: Schottky effect or field enhanced thermionicemission Field electron emission, emission of electrons induced by an electrostatic field An...
electron gun is large enough. In this case, the emission current is regulated by the thermionicemission process, given by the Richardson Dushman equation...
but are not hot enough for significant thermionicemission. Because cold cathode lamps have no thermionicemission coating to wear out, they can have much...
emission or thermionicemission. Thermionicemission occurs when the thermal energy exceeds the metal's work function, while field electron emission occurs...
physicist who won the Nobel Prize in Physics in 1928 for his work on thermionicemission, which led to Richardson's law. Richardson was born in Dewsbury,...
causes it to release electrons into the vacuum, a process called thermionicemission. The cathode is coated with oxides of alkaline earth metals, such...
electronic viewpoint, thermionic energy conversion is the direct production of electric power from heat by thermionic electron emission. From a thermodynamic...
flowing through the barrier is essentially governed by the laws of thermionicemission, combined with the fact that the Schottky barrier is fixed relative...
thermionicemission or use thin barriers and transport carriers via tunneling. Carrier lifetime for escape is determined by tunneling and thermionic emission...
considered "cold" if it emits more electrons than can be supplied by thermionicemission alone. It is used in gas-discharge lamps, such as neon lamps, discharge...
cover certain apparent exceptions. In 1853, Becquerel discovered thermionicemission. In 1867 and 1868 Becquerel published La lumière, ses causes et ses...
electrons either through heating (thermionicemission) or in an electric field that is sufficient to cause field electron emission. Once initiated, a vacuum arc...
The Diode equation includes the emission coefficient (which is not related to the one discussed here) Thermionicemission Incorporated, SynLube. "Spectroscopy...
rather than as free electrons across a vacuum (typically liberated by thermionicemission) or as free electrons and ions through an ionized gas. Semiconductor...
Nordheim, assisted by Ralph Fowler, published a paper which discussed thermionicemission and reflection of electrons from metals. He assumed a surface potential...
resembles a vacuum tube in appearance, its operation does not depend on thermionicemission of electrons from a heated cathode. It is hence a cold-cathode tube...
broadcast medium. The type of device known as a thermionic tube or thermionic valve uses thermionicemission of electrons from a heated cathode for a number...
electrostatic thermionic electron gun is formed from several parts: a hot cathode, which is heated to create a stream of electrons via thermionicemission; electrodes...
large underground areas at or near the surface of the Earth. Thermionicemission — the emission of electrons from a heated electrode, usually the cathode...
mechanics to solid-state problems, such as thermionicemission, work function of metals, field electron emission, rectification in metal-semiconductor contacts...
Global Information
