The oxide-ion conductivity and crystal structure of the perovskite-type (Ba1-x-ySrxLay)2In2O5+y solid-solution system, which was derived from Ba2In2O5 with a brownmillerite-type structure, were investigated as a function of temperature and O partial pressure. The oxide-ion conductivity was considered from the viewpoint of the unit-cell free-volume. The oxide-ion transport number approached unity with increasing La content and the ion conductivity increased with the La or Sr content. The oxide-ion conductivity (1073K) of (Ba0.3Sr0.2La0.5)2In2O5.5 exhibited a maximum value of 0.12S/cm, which exceeded that of yttria-stabilized zirconia. It was found that the oxide-ion conductivity of the present system was dominated by both the unit-cell free-volume and the amount of mobile oxide ion.

Oxide-Ion Conductivity of the Perovskite-Type Solid-Solution System, (Ba1-x-ySrxLay)2In2O5+y. K.Kakinuma, H.Yamamura, H.Haneda, T.Atake: Solid State Ionics, 2002, 154-155, 571-6