An experimental method to identify various oxygen species transported in oxides

Oxygen transport in oxides can take place in molecular, atomic and ionic form. An experimental method is described which separates the contributions of molecules, atoms and ions to the overall oxygen transport in oxides. The method comprises gas phase analysis and the use of oxygen isotopes 16O and 18O. In the general case, exposure to non-equilibrated O2 containing 60–70% 18O is optimal to obtain the highest accuracy in the measurement. The method is exemplified by distinguishing non-ionic (molecular and atomic) oxygen transport from ionic oxygen transport in a commercial yttria-stabilized zirconia (YSZ) sample in the temperature range of 600–900 °C. There is approximately 35% molecular, 20% atomic transport and 45% ionic oxygen transport in YSZ at 600 °C. It is found that the fraction percent of non-ionic oxygen transport decreases with increasing temperature, and ionic oxygen transport increases sharply with increasing temperature.