A modified liquid-phase-assisted sintering mechanism for La0.8Sr0.2Cr1−xFexO3−δ—A high density, redox-stable perovskite interconnect for solid oxide fuel cells

Abstract

Fe-doped lanthanum strontium chromites, i.e., La0.8Sr0.2Cr1−xFexO3−δ (x = 0.1, 0.2, 0.3, 0.4, and 0.5), are synthesised and evaluated as potential interconnect materials for SOFCs. A modified liquid-phase-assisted sintering mechanism is employed to improve the sintering abilities of La0.8Sr0.2Cr1−xFexO3−δ powders. A distinct transient liquid phase forms during the sintering process, which spreads into a uniform layer and covers the grain boundaries, thereby enhancing densification. Additionally, it is determined that the amount of liquid phase formed during liquid-phase-assisted sintering significantly affects the densification of doped lanthanum chromites. Relative densities of 94.6% and 96.6% are successfully obtained for La0.8Sr0.2Cr0.6Fe0.4O3−δ and La0.8Sr0.2Cr0.5Fe0.5O3−δ, respectively. Furthermore, these compounds are also redox-stable after being heated to 900 °C in flowing H2 for 6 h. The electrical conductivity increases with Fe-doping levels, and the conductivity of La0.8Sr0.2Cr0.5Fe0.5O3−δ is measured to be 21.88 S cm−1 in air and 6.45 S cm−1 in 5% H2/Ar at 800 °C. Therefore, dense La0.8Sr0.2Cr0.5Fe0.5O3−δ is a promising interconnect alternative for solid oxide fuel cells.