This compound consisted of inter-growths of the Aurivillius phase, Bi4Ti3O12, and of brownmillerite-like layers of BaMO2.5. The O ion conductivity was measured by using complex impedance methods, and it was found that the compound exhibited a discontinuity in the Arrhenius plot. The occurrence of a phase transition at this discontinuity was confirmed by means of differential thermal analysis, and was consistent with an O vacancy order-disorder transition. The conductivity at 900C was equal to 4.5 x 10-2S/cm.

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