A modified liquid-phase-assisted sintering mechanism for La_(0.8)Sr_(0.2)Cr_(1-x)Fe_xO_(3-δ)-A high density, redox-stable perovskite interconnect for solid oxide fuel cells

摘要

Fe-doped lanthanum strontium chromites, i.e., La_(0.8)Sr_(0.2)Cr_(1-x)Fe_xO_(3-δ) (x = 0.1, 0.2, 03, 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 La_(0.8)Sr_(0.2)Cr_(1-x)Fe_xO_(3-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 La_(0.8)Sr_(0.2)Cr_(0.6)Fe_(0.4)O_(3-δ) and La_(0.8)Sr_(0.2)Cr_(0.5)Fe_(0.5)O_(3-δ), respectively. Furthermore, these compounds are also redox-stable after being heated to 900 ℃ in flowing H_2 for 6 h. The electrical conductivity increases with Fe-doping levels, and the conductivity of La_(0.8)Sr_(0.2)Cr_(0.5)Fe_(0.5)O_(3-δ) is measured to be 21.88 S cm~(-1) in air and 6.45 S cm~(-1) in 5% H_2/Ar at 800 ℃. Therefore, dense La_(0.8)Sr_(0.2)Cr_(0.5)Fe_(0.5)O_(3-δ) is a promising interconnect alternative for solid oxide fuel cells.