Definition of thermion in English:



  • An ion or electron emitted by a substance at high temperature.

    • ‘He discovered the Schottky effect, an irregularity in the emission of thermions in a vacuum tube and invented the screen-grid tetrode tube.’
    • ‘Alloyed thorium enhances the emission of thermions by lowering the work function barriers.’
    • ‘Another theory is that, since energy is required to extract electrons from the heated material, there should be cooling when thermions are emitted.’
    • ‘When the main power supply of the X-ray tube is on, the cathode emits thermions as it is heated by a heater.’
    • ‘If the ionization electrode is located at an appropriate position in the vicinity of the evaporation source and a positive voltage with respect to that of the evaporation source is applied to the electrode, thermions and secondary electrons from the evaporation source migrate toward the ionization electrode.’


Early 20th century: from thermo- ‘of heat’ + ion.