It was noted that the cubic -phase of Bi3BaO5.5 exhibited a half an order of magnitude higher conductivity than that of the distorted monoclinic  phase. Solid solutions of the monoclinic isomorphs were prepared by solid-state reaction. An increased ionic conductivity of these substituted phases was attributed to the combined effect of a decreasing activation energy and an increasing pre-exponential factor.

J.Yan, M.Greenblatt: Solid State Ionics, 1995, 82[3-4], 209-14