The syntheses of La0.95Sr0.05GaO3-delta (LSG), La0.95Sr0.05AlO3-delta (LSA) and Y0.95Sr0.05AlO3-delta (YSA), and their electrical properties using constant frequency (10 kHz) a.c. conductivity measurements as a function of oxygen partial pressure (P-O2 ranging from air to 10(-15) Pa) and temperature (800-1000 degrees C) are described. Ion-blocking measurements were also performed on:some compositions. All materials showed dominant ionic conductivity within limited ranges of working conditions, although their ionic domains differed considerably in magnitude. LSG samples had the highest ionic conductivity, with only a minor p-type contribution in air. LSA had intermediate conductivity, with p-type conductivity dominant in air. YSA samples had the lowest conductivity of all those measured, again with dominant p-type conductivity in air. All materials were stable within large P-O2 domains, and exhibited negligible n-type conductivities even under reducing conditions typical of fuel-rich atmospheres.