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

Abstract

Strontium- and titanium-doped lanthanum scandates (La 1− x Sr x Sc 1− y Ti y O 3− 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 N 2/H 2/H 2O or N 2/O 2/H 2O. 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% H 2O at 800 °C, the highest total conductivity achieved was for (La 0.8Sr 0.2) 0.99Sc 0.9Ti 0.1O 3− 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 La 0.8Sr 0.2Sc 0.9Ti 0.1O 3− d . The ceramic processing procedure affected the conductivity of La 0.6Sr 0.4Sc 0.7Ti 0.3O 3, particularly at low temperature.