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.