Oxygen-loss in A-site deficient Sr0.85La0.10TiO3 perovskite

Abstract

The electrical properties of Sr_1−3xLa_2xTiO₃ ceramics (x = 0.05, LST) change dramatically with sintering temperature and atmosphere. Ceramics sintered at 1200 °C in both O₂ and N₂ exhibit near intrinsic band-type conduction with bulk conductivity ∼10⁻⁷ S cm⁻¹ at 500 °C and activation energy for conduction, E_a of ∼1.6–1.8 eV. LST ceramics sintered at 1450 °C in O₂ exhibit much higher bulk conductivity (>10⁻⁴ S cm⁻¹ at −50 °C) with an E_a ∼ 0.16 eV. For LST ceramics sintered at 1450 °C in N₂, the bulk conductivity was too high to be measured by impedance spectroscopy even at 10 K. In addition, electrical heterogeneity is observed in LST pellets sintered at 1450 °C under both O₂ and N₂ where pellet outer surfaces are more resistive than the inner regions of the ceramic. The defect chemistry of Sr_0.85La_0.10TiO₃ perovskite is discussed based on chemical doping and oxygen-loss mechanisms and we highlight the importance of A-site vacancies on the oxygen-loss mechanism in La-doped ST-based ceramics.