The compound consisted of inter-grown Bi4Ti3O12 and layers of BaMO2.5. The O ion conductivity was measured by using complex impedance methods, and it was found that there was 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 phase transition exhibited hysteresis. The conductivity was equal to 2.5 x 102S/cm at 900C.

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