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. A large 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. The X-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. The measured 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 frac(1, 2) O2 + VO• • + 2NdCe' = OO× + 2NdCe×.
- B-site doping
- Oxygen nonstoichiometry
- Proton conductive perovskite-type oxides