The role of dopant concentration, A-site deficiency and processing on the electrical properties of strontium- and titanium-doped lanthanum scandate

Strontium- and titanium-doped lanthanum scandates (La1−xSrxSc1−yTiyO3−δ) have been prepared and their electrical properties studied over the temperature range 170–1000 °C and in varied oxygen partial pressures. The electrical conductivity was measured by four-point dc technique in atmospheres of N2/H2/H2O or N2/O2/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 ∼1% H2O at 800 °C, the highest total conductivity achieved was for (La0.8Sr0.2)0.99Sc0.9Ti0.1O3−d of 23 mS cm−1 of which 6 mS 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.