These compounds consisted of inter-growths of the Aurivillius phase, Bi4Ti3O12, and of brownmillerite-like layers of BaMO2.5. The O ion conductivities were measured by using complex impedance methods, and it was found that the above compounds 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. In the case of the Sc-containing compound, the phase transition exhibited hysteresis. The conductivity was equal to 2.5 x 102S/cm at 900C. The conductivities of the In-containing and Ga-containing compounds at this temperature were equal to 4.9 x 10-2 and 4.5 x 10-2S/cm, respectively.

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