Oxygen transport properties of La _1-xCa _xCrO _3-δ as an interconnect material of a solid oxide fuel cell

Oxygen isotope diffusion coefficients were determined for La _1-xCa _xCrO _3-δ (x = 0.1, 0.2, 0.3) via bulk and via grain-boundary diffusion as functions of calcium content (x), temperatures from 1073 to 1273 K, and oxygen partial pressures from p(O ₂) = 10 ^-9 to 10 ⁴ Pa at T = 1273 K. Both bulk and grain-boundary diffusion coefficients increased with calcium content. For La _0.8Ca _0.2CrO _3-δ, the activation energy is 160 and 167 kJ mol ^-1 for bulk and grain-boundary diffusion, respectively. The bulk-diffusion coefficient increased with decreasing oxygen partial pressure. The oxygen vacancy diffusion coefficient was calculated as (1.7±0.5)×10 ^-9 m ² s ^-1 at T = 1273 K, constant regardless of calcium content or oxygen-vacancy content. The effect of surface exchange on the oxygen permeation through La _1-xCa _xCrO _3-δ was quantitatively evaluated.