Cobalt-free perovskite cathode materials SrFe1−xTixO3−δ and performance optimization for intermediate-temperature solid oxide fuel cells

•Effects of Ti substitution for Fe on structure and properties of the SFT are studied.•SFT materials are chemically compatible with LSGM and SDC electrolytes.•Cell performance and thermal compatibility are greatly improved by adding SDC.

Fe-based perovskite oxides SrFe1-xTixO3-δ (SFT, x = 0.00–0.15) are developed as cathode materials for intermediate-temperature solid oxide fuel cells (IT-SOFCs). Dense single-phase SFT solid solutions are obtained by sintering the samples at 1300 °C for 10 h. The SFT materials are chemically compatible with the La0.9Sr0.1Ga0.8Mg0.2O3−δ (LSGM) and Ce0.8Sm0.2O1.9 (SDC) electrolytes at 1000 °C for 2 h. The highest electrical conductivity of 72 S cm−1 at 650 °C in air is obtained for the x = 0.05 sample. The substitution of Ti for Fe significantly reduces the thermal expansion coefficients (TECs) from 26.5 × 10−6 K−1 at x = 0.00 to 22.9 × 10−6 K−1 at x = 0.15 between 30 and 1000 °C. Single cells that use SFT as cathodes with x = 0.00, 0.05, 0.10, and 0.15 on a 300 μm-thick LSGM electrolyte reach the peak power density of 446, 475, 439, and 432 mW cm−2 at 800 °C, respectively. The addition of SDC in x = 0.05 cathode significantly enhances the cell performance and reduces the TEC of the SFT–SDC composite cathodes. The Ti-substituted SFT perovskites and SFT–SDC composites can be considered cheaper alternative cathode materials for use in IT-SOFCs.