Preparation of cathode material for co-sintering with electrolyte at high temperature

Ti-doped La-Sr-Co-Fe-based oxides (LSTCFs) were prepared as cathode material for co-sintering with electrolyte at high temperatures. LSTCFs have relatively high solid solubility limits of Ti up to 80mol%. Before reaching the solubility limits, LSTCFs were well densified and single phase with a rhombohedral structure (R-3c). Meanwhile, after exceeding the solubility limits, a Ti-rich secondary phase appeared and microstructures tend to be porous. Electrical conductivity and thermal expansion coefficient (TEC) for LSTCF decreased with increasing Ti content. Ti4+ appears to work as a donor and suppress electronic spin state transition of Co3+ ions and formation of oxygen vacancies. The composition, such as La_0.6Sr_0.4Ti _0.4Co_0.2Fe_0.8)_0.6O ₃-δ (LSTCF28) with 40 mol%Ti and La_0.6Sr _0.4Ti_0.6 (Co_0.8Fe_0.2) _0.4O₃-δ (LSTCF82) with 60 mol%Ti, showed low sinterability and sufficient thermomechanical compatibility with GDC electrolyte. Those, however, possess more than two order of magnitude lower electrical conductivity than those of typical cathode materials.