Total electrical conductivity of (Ba0.5+xLa0.5−x)2(In1−xMx)2O5.5 (M = Zr and Ce) and (Ba0.5−xLa0.5+x)2(In1−xMx′)2O5.5 (M′ = Mg, Ca and Sr) solid-solution systems was measured as functions of temperature and O partial pressure. The oxide-ion conductivity of all the solid-solution systems increased at first with an increase in the unit cell free volume. However, it exhibited a maximum value at a unit cell free volume and then decreased. All the solid-solution systems exhibited a similar dependence of the oxide-ion conductivity on the unit cell free volume, even if they have different average ionic valences in the A- and B-sites. From the results of the Raman spectra measurement, the decrease of conductivity in the larger unit cell free volume range was presumed to arise from the local distortion of O octahedra.

Electrical Conductivity and Local Distortion of (Ba0.5La0.5)2In2O5.5 Doped with Divalent or Tetravalent Cation in In-Site. K.Kakinuma, N.Takahashi, H.Yamamura, K.Nomura, T.Atake: Solid State Ionics, 2004, 168[1-2], 69-74