A new Aurivillius phase with intrinsic O vacancies was synthesized. Its average structure was very close to that of the parent phase, (Bi2O2)(Nb2CaO7). The new phase exhibited a discontinuous change in the Arrhenius plot of the ionic conductivity. Differential thermal analysis data confirmed the existence of a reversible phase transition at 860C. At 900C, the conductivity of (Bi2O2)(Nb2NaO6.5) was 0 01S/cm. At 1000C, the Aurivillius phase slowly decomposed into a mixture of phases with a lower total conductivity.

A.Q.Pham, M.Puri, J.F.DiCarlo, A.J.Jacobson: Solid State Ionics, 1994, 72, 309-13