Strontium- and titanium-doped lanthanum scandates (La1-xSrxSc1-yTiyO3-delta) have been prepared and their electrical properties studied over the temperature range 170-1000 degreesC and in varied oxygen partial pressures. The electrical conductivity was measured by four-point de technique in atmospheres of N-2/H-2/H2O or N-2/O-2/H2O. For all compounds, an ionic regime is seen and, at high oxygen partial pressures, a mixed ionic/p-type regime is observed. At low oxygen partial pressures, a slight increase in conductivity is observed, which may be due to n-type or increased protonic conduction. In air with similar to1% H2O at 800 degreesC, the highest total conductivity achieved was for (La0.8Sr0.2)(0.99)Sc0.9Ti0.1O3-d of 23 mS cm(-1) of which 6 nS cm(-1) was ionic. The A-site deficiency led to increased ionic and p-type conductivity over La0.8Sr0.2Sc0.9Ti0.1O3-d. The ceramic processing procedure affected the conductivity of La0.6Sr0.4Sc0.7Ti0.3O3, particularly at low temperature. (C) 2004 Elsevier B.V. All rights reserved.