The Aurivillius ceramics Bi(2-y)PbySr2Nb2TiO(12-delta) and Bi2Sr2Nb2Ti(1-x)MxO(12-delta) (M=Fe, Cr, Mn) were successfully prepared and the solid solubility limits were determined to be y=0.2 and x=0.2. The solubility limits for the phases are limited by the oxygen vacancy concentration. The electrical conductivity was measured as a function of temperature and oxygen activity, and showed that undoped Bi2Sr2Nb2TiO12 is an electronic conductor at high oxygen activity, while acceptor doping with Pb or Fe results in ionic conduction. The total conductivity increases with dopant concentration to a maximum at the solubility limits of 7.5 x 10(-4) to 10 X 10(-4) S/cm at 800 degrees C for Pb, Fe, and Mn dopants. (c) 2007 Elsevier B.V. All rights reserved.