La0.3Sr0.7Ti0.3Fe0.7O3-δ derived from Malaysian ilmenite and monazite for application of solid oxide fuel cell cathode

Abstract

This study investigates the effect of using low-purity oxides in synthesizing lanthanum strontium titanate ferrite (LSTF) on its electrochemical performance as a solid oxide fuel cell (SOFC) cathode material. Lanthanum oxide at 30% and 60% purity is extracted from monazite, and iron oxide at 70% and 90% purity is extracted from ilmenite as the LSTF precursor. Symmetrical pellets are fabricated from yttria-stabilized zirconia (YSZ) as the electrolyte, samarium-doped ceria (SDC) as the buffer layer, and silver paste as the current-collecting layer (CCL). Results from electrochemical impedance spectroscopy (EIS) demonstrate that LSTF made from extracted lanthanum with low purity shows comparable electrical performance with a polarity resistance (Rp) of below 0.2 Ω at operational temperature of 800 °C compared to LSTF made from commercial ingredients, while LSTF made from extracted iron shows equal performance only with high-purity ingredients. LSTF made with extracted lanthanum and iron exhibits an Rp of 0.5 Ω and does not show comparable performance with LSTF made with commercial ingredients, likely due to a high variety of impurities. Based on this study, LSTFLa30 and LSTFFe90 show high potential for SOFC cathode applications at operating temperatures in the range of 700–800 °C.