Electrical conductivity of Al-doped La_1-xSr_xScO₃ perovskite-type oxides as electrolyte materials for low-temperature SOFC

As an electrolyte material for reduced temperature solid oxide fuel cell (SOFC), La_{1 - x}Sr_xScO_{3 - α} (x = 0.05-0.5) solid oxides with high ionic conductivity were synthesized by the solid phase method. The electrical conductivity rose as the value of x increased. For x ≥ 0.35, the compound underwent a phase transition at 1073 K. Adding 2 mol% Al to the Sc site was very effective in suppressing this transition. However, the electrical conductivity of La_0.65Sr_0.35Sc_0.98Al_0.02O₃ was lower than that of La_0.675Sr_0.325ScO₃. La_0.675Sr_0.325ScO₃, an unstable solid, maintained high ionic conductivity even when effectively stabilized by 1 mol% Al doping at the Sc site. Furthermore, no n-type conduction of La_0.675Sr_0.325Sc_0.99Al_0.01O₃ was observed under low oxygen partial pressure.