Intense atomic oxygen emission from incandescent zirconia

Particle emissions from an oxide-ion conducting solid electrolyte (tetragonal zirconia polycrystal, 3% Y ₂O ₃-doped ZrO ₂) have been examined using a high vacuum evaluation system. Oxygen gas with a pressure range from 10 to 3 × 10 ³ Pa was fed into a 2 mm outer diameter zirconia tube, whose central region of 10 mm length was heated to 1400-1800 °C by direct Joule heating. The emission species were identified by appearance potential spectroscopy using a quadrupole mass spectrometer. Atomic oxygen (AO) is the dominant species that is radiantly emitted from the high-temperature region. Temperature dependence of the AO emission intensity exhibits far less activation energy (̃0.3-1.0 and 0.7 eV, on average) than electric field-assisted thermal O ^- ion (̃2 eV) and electron (̃6 eV) emission from zirconia reported before. High AO emission flux (in the order of 10 ¹⁷ atoms.cm ^-2.s ^-1) is promising for use as practical AO sources.