title: EXAFS study of crystal structures of (Ba1-xLax)2In2O5+x and their oxide ion conductivity.
abstract: Crystal structures of(Ba1-xLax)2In2O5+x (x=0.00, 0.20, 0.30, 0.40, 0.50) were analyzed by EXAFS and the powder X-ray Rietveld method. A Fourier transform of In K-edge EXAFS data from (Ba1-xLax)2In2O5+x showed a peak between 1.2 and 2.0 A attributed to the nearest oxide ions around In3+ cation. The peak as back-Fourier transformed, and the structural parameters were refined by the least square fitting. The coordination number of In3+ cation increases with increasing La3+ cation) content. This means oxygen is introduced at interstitial site by keeping an electroneutrality. As a result of the oxygen distribution, the oxide ion vacancies distribute randomly. The electrical conductivities of (Ba1-xLax)2In2O5 rapidly increased above 1203 K due to the order-disorder transition of oxygen vacancy. On the other hand, the electrical conductivities of (Ba1-xLax)2In2O5+x (x=0.20, 0.30, 0.35. 0.40, 0.45, 0.50) did not show the sharp discontinuity in the conductivity because the disorder phase of defective perovskite type structure was stabilized by doping La3+ cations at A-site even at low temperature.
authors.affiliation: Department of Fundamental Energy Science, Graduate School of Energy Science, Kyoto University, Japan. yuchimot@o.cc.titech.ac.jp
authors.forename: Y
authors.initials: Y
authors.lastname: Uchimoto
authors.forename: H
authors.initials: H
authors.lastname: Takagi
authors.forename: T
authors.initials: T
authors.lastname: Yao
authors.forename: N
authors.initials: N
authors.lastname: Ozawa
authors.forename: T
authors.initials: T
authors.lastname: Inagaki
authors.forename: H
authors.initials: H
authors.lastname: Yoshida