Nonstoichiometry of Ce1−XYXO2−0.5X−δ (X=0.1, 0.2)

Nonstoichiometry of the fluorite-type oxide solid solutions Ce1−XYXO2−0.5X−δ (X=0.1, 0.2) was measured as a function of temperature (T=973–1373 K) and oxygen partial pressure (P(O2)=10−2–10−24 atm) by means of thermogravimetry. The result shows that the nonstoichiometry of Ce1−XYXO2−0.5X−δ (X=0.1, 0.2) is not explained by a simple point defect model, therefore, defect association models are suggested. From the calculation, it is found that (CeCe′VOCeCe′)x is the major defect association not only in Ce1−XYXO2−0.5X−δ (X=0.1, 0.2), but also in pure CeO2 for nonstoichiometries less than 0.10. It is also found that the defect association (CeCe′VOCeCe′)x is dominating at lower temperature and smaller X composition.