Reducing the Cobalt Content in SrCo0.95Ti0.05O3-δ-Based Perovskites to Produce Cleaner Cathodes for IT-SOFCs

Abstract

Recent studies have demonstrated the possibility of stabilizing the cubic or tetragonal perovskite phases in the SrCoO3-δ system at room temperature by partially replacing Co atoms with small amounts of highly charged cations like Ti4+ in SrCo0.95Ti0.05O3-δ. This material gives extraordinary performances as a cathode for solid oxide fuel cells (SOFCs) at intermediate temperatures (800–850 °C). In this work, we have tried to still improve this cathode in a cleaner and low-priced material by reducing its Co content, since Co is a high-cost and toxic element, additionally reducing its thermal expansion coefficient (TEC), to make it more mechanically compatible with the rest of the components of a SOFC. SrCo0.50Fe0.45Ti0.05O3-δ perovskite has been obtained by the citrate method, introducing 45% of Fe in the Co and Ti positions. Its crystalline structure has been studied by X-ray diffraction (XRD) and neutron powder diffraction (NPD) and has been correlated with mechanical and electrical properties. A chemical compatibility study between SrCo0.50Fe0.45Ti0.05O3-δ and the electrolyte La0.8Sr0.2Ga0.83Mg0.17O3-δ (LSGM) revealed that both materials do not interact at high temperatures. TEC measurements show a linear expansion over the entire temperature range. Finally, the perovskite showed good electrical conductivity and an encouraging power density value of 667 mW/cm2 at 850 °C, which indicate that this material is a promising cathode for SOFCs at intermediate temperatures.