Phrase of the Week: Thermionic Emission

July 20, 2012

If you heat materials to a high enough temperature, some of their electrons will gain enough kinetic energy to literally boil off the surface and into the air or vacuum beyond.  Since net motion of electrons constitutes an electrical current, this phenomenon, called thermionic emission, is one of the seven basic methods for producing electricity.

Thermionic emission is at the heart of a new approach to solar energy harvesting pioneered by Stanford Institute of Materials and Energy Sciences researchers that promises unprecedented efficiency by taking advantage of the improved performances of thermionic and thermal processes at high temperatures.

While the SIMES combination is new, scientific evidence of thermionic emission goes back more than 130 years. In 1873, British scientist Frederick Guthrie was first to describe the thermionic phenomenon. Thomas Edison also explored it while trying to improve the lifetime of his new electric light bulbs. In 1904, John Ambrose Fleming invented an early vacuum tube that would become known as the "thermionic valve," which led to tubes that enabled modern radio technologies.

British physicist Owen Willans Richardson christened the hot-electron emission as “thermionic” and ultimately received the 1928 Nobel Prize in Physics “for his work on the thermionic phenomenon and especially for the discovery of the law named after him" that described it precisely.