A thermionic process is one that involves electrically charged particles being emitted by an incandescent material. Thermionic emission is the spontaneous emission of electrons from metal or oxide-coated metal surfaces at temperatures between 1,000 K and 3,000 K. It supplies the electrons in electron tubes and cathode-ray tubes.

 

Richardson, Owen Willans (1879–1959)

Owen Richardson was a British physicist awarded the 1928 Nobel Prize in Physics for his pioneering work on thermionic (a term he coined) emission. In 1911 Richardson showed that electrons are emitted from hot metals, disproving the theory that they arose from the surrounding air. Also in 1911, he formulated an equation, known as Richardson's law which relates the rate of thermionic emission to the absolute temperature of the heated metal. This was of fundamental importance in the development of the electron tube, and in the electron gun of a cathode-ray tube.