Features and mechanism of atomic oxygen radical anion emission from yttria-stabilized zirconia electrolyte

Anion and electron emissions from Y2O3-stabilized ZrO2 (YSZ) electrolyte were investigated by time of flight (TOF) spectroscopy. The atomic oxygen radical anion (O−) is the only anion species emitted from the YSZ surface. The emission branch ratio between O– and electrons is close to one. The Arrehenius plots for both O– and electron emission, derived from the temperature dependences, exhibit double linear behavior. The apparent activation energies in the low-temperature region (<620 °C) are significantly higher than those in the high-temperature region (>620 °C). It was also found that the extraction field can enhance the O– emission. The maximum emission current density for O– is 3.5 nA/cm2 in our investigated range. The observed O– and electron emissions are attributed to the dissociation of the intermediate anions, O2–, present on the YSZ anode surface. The rate-determining step for the O– emission is believed to be the desorption process in the low-temperature region, and the electron desorption or the electrochemical reaction in the high-temperature region.