This O ion conductivity of this compound, which consisted of inter-grown Aurivillius phase, Bi4Ti3O12, and brownmillerite-like layers of BaMO2.5, was measured by using complex impedance methods. It was found that the compound exhibited a discontinuity in the Arrhenius plot. The occurrence of a phase transition at this discontinuity was confirmed, and was consistent with an O vacancy order-disorder transition. The conductivity at 900C was equal to 4.9 x 10-2S/cm.

J.K.Thomas, K.R.Kendall, H.C.Zur Loye: Solid State Ionics, 1994, 70-71, 225-8