Oxygen nonstoichiometry of the perovskite-type oxides BaCe0.9M0.1O3 − δ (MY, Yb, Sm, Tb, and Nd)

The oxygen nonstoichiometry, δ, of B-site doped BaCeO3 − δ under dry condition was determined as a function of oxygen partial pressures, PO2, between 1 bar and 10− 4 bar and temperatures between 773 K and 1373 K. The variation of δ in BaCe0.9Y0.1O3 − δ, BaCe0.9Yb0.1O3 − δ, BaCe0.9Sm0.1O3 − δ and BaCe0.9Tb0.1O3 − δ was very small through the experimental conditions. This indicates that charge imbalance due to the trivalent dopants is compensated essentially by the oxygen vacancy formation. e variation was found for δ of BaCe0.9Nd0.1O3 − δ by PO2 and temperature. This result indicates that the valence of the metal elements change under the experimental conditions. ray absorption spectroscopy (XAS) measurement was carried out to examine the valence of the B-site elements of BaCe0.9Nd0.1O3 − δ. The samples of different δ were prepared. From the XANES spectra of Ce and Nd, no spectra change for Ce L3-edge was observed, while spectra change was observed for Nd L3-edge and L2-edge. This indicates that the valence of Ce stay unchanged, while the valence of Nd may be changed by the different δ conditions. asured δ of BaCe0.9Nd0.1O3 − δ was analyzed by considering the valence change of neodymium. By considering the defect equilibrium among Nd′Ce, Nd×Ce, VO••, and OO×, the change of δ against PO2 was well explained by assuming the defect equilibrium 1 2 O 2 + V O • • + 2Nd Ce ʹ = O O × + 2Nd Ce × .