Preparation of La₁₋x Sr[subscript x] FeO₃ (LSF) - La[subscript 0.8] Sr [subscript 0.2]Co₁-x₋Fe[subcript x]O₃ (LSCF) composite cathodes for solid oxide fuel cell

Abstract

Composite materials were prepared by physical mixing of La₁₋xSrxFeO₃-δ (x = 0.6 และ 0.7) กับ La[subscript 0.8]Sr[subscript 0.2]Co₁₋xFexO₃-δ (x = 0.1 and 0.2) in various ratios: 1:2, 1:3, 1:1, 3:1 and 2:1. The influences of calcination temperature, sintering temperature and sintering time on the structures and properties of LSF-LSCF perovskite were investigated. X-ray diffraction (XRD) patterns showed that LSF-LSCF perovskite phase was formed after calcination at 800℃ and 900℃. Using SEM, the morphology of the perovskite oxide discs revealed dense microstructures. The grain sizes of LSF-LSCF composites increased with increasing the amount of LSCF and the sintering temperature, but decreased with increasing the sintering time. Conductivity measurements using DC 4-probe in air exhibited that the conductivity of the composites increased with increasing the amounts of LSCF. The conductivity performance of the 1:3 LSF-LSCF composite was maximized by sintering at 1300℃ for 10 hours. The specific conductivity of LSF37-LSCF8291 reached the maximum value of 1,000.90 S/cm at 650 °C. For thermal expansion analysis, the TEC values of LSF-LSCF composites reduced with mixing LSF. The lowest thermal expansion coefficient is 18.10 x 10⁻⁶ oC⁻¹ for LSF46-LSCF8291.