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 La0.6Sr0.4Ti0.4(Co0.2Fe0.8)(0.6)O3-delta (LSTCF28) with 40 mol% Ti and La0.6Sr0.4Ti0.6(Co0.8Fe0.2)(0.4)O3-delta (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.