Sintering Characteristics and Electrical Conductivity of (Sr_1−xLa_x)TiO₃ Synthesized by the Citric Acid Method

The air-sintering characteristics and electrical conductivity of (Sr_1−xLa_x)TiO₃ perovskites (0 ≤ x ≤ 0.3) synthesized by the citric acid method were evaluated in terms of their use as interconnect materials in solid oxide fuel cells. A single perovskite phase of (Sr_0.8La_0.2)TiO₃ powder was formed at 800 °C. In this powder, a Ruddlesden–Popper Sr₂TiO₄ layer appeared in the temperature range of 1100–1500 °C, and disappeared at 1600 °C. (Sr_0.8La_0.2)TiO₃ powders which were calcined at 1000–1100 °C showed the best sintering characteristics. The relative density of the samples reached 94% at 1400 °C, although the Ruddlesden–Popper layer remained in this dense sample. Electrical conductivities of (Sr_1−xLa_x)TiO₃ bars at 1000 °C were approximately 0.10–1.1 S cm⁻¹ in air and 7.1–12 S cm⁻¹ in a reducing atmosphere. For a (Sr_0.9La_0.1)TiO₃ pellet placed between both air and reducing atmospheres, the conductivity at 850 °C was 0.033 S cm⁻¹, which is close to that in air. No compositional dependency on electrical conductivity was observed for the (Sr_1−xLa_x)TiO₃ pellets.