Electrode properties of the ruddlesden-popper series, La_{n +1}Ni_nO_3n+1 (n=1, 2, and 3), as intermediate-temperature solid oxide fuel cells

The Ruddlesden-Popper phases, La_n+1Ni _nO_3n+1 (n=1, 2, and 3), were synthesized by a solid-state reaction for use as cathodes in an intermediate-temperature (500°-700°C) solid oxide fuel cell. The samples crystallized into an orthorhombic layered perovskite structure. The overall electrical conductivity increased with the increase of n in the intermediate temperature range. Single test-cells, which consisted of samarium-oxide-doped ceria (SDC; Sm_0.2Ce _0.8O_x) as an electrolyte, Ni-SDC cermet (Ni-SDC) as an anode, and La_n+1Ni_nO_3n+1 as a cathode, were fabricated for measurements of cell performance at 500°-700°C. Current interruption measurements revealed that both the ohmic and overpotential losses at 700°C decreased with the increase of n. La₄Ni₃O₁₀ was found to exhibit the best cathode characteristics in the La_n+1Ni_nO _3n+1 series. Maximum test-cell power densities with La ₄Ni₃O₁₀ (n=3) were 10.2, 36.5, and 88.2 mW/cm² at 500°, 600°, and 700°C, respectively.