Highly Conductive and Stable Calcium-Doped Oxygen-deficit Strontium Iron Titanium Molybdenum Oxide Ceramic Interconnect for Flat-Tubular Segmented-In-Series Solid Oxide Fuel Cells

This study has produced a novel double-perovskite (Calcium-Doped Oxygen-deficit Strontium Iron Titanium Molybdenum Oxide (Ca-doped Sr2Fe1.2Ti0.3Mo0.5O6-δ)ceramic interconnect material to address the challenges of poor electrical conductivity and structural instability in dual-atmosphere operations for self-sealing flat-tubular segmented-in-series solid oxide fuel cells (FT-SIS-SOFCs).The Sr2-xCaxFe1.2Ti0.3Mo0.5O6-δ(x = 0, 0.1, 0.2, 0.3) powders were synthesized via a sol-gel method.The phase composition, sintering density, thermal expansion, and electrical conductivities of the Sr2-xCaxFe1.2Ti0.3Mo0.5O6-δwere systematically analyzed.The results demonstrated that Ca doping effectively suppressed the precipitation of metallic Fe under reducing conditions.Although the conductivity in air decreased from 7.61 to 3.04 S cm -1 at 650 °C with increasing Ca content, it significantly increased in a reducing atmosphere (from 3.43 to 13.12 S cm -1 ).These improvements were caused by lattice contraction strengthening the Ca-O bonds and an increased Mo 6+ /Mo 5+ ratio, which shortens electron transfer pathways.Sr1.8Ca0.2Fe1.2Ti0.3Mo0.5O6-δexhibited optimal overall performance, demonstrating excellent conductivity in both atmospheres, well-matched thermal expansion with common electrolytes, and robust chemical compatibility with adjacent cell components.Moreover, it showed remarkable long-term stability at 650 °C.This work provides a promising strategy for developing high-performance ceramic interconnects for advanced SOFC configurations.