The transport properties of layered perovskite GdBaCo2O5+δ, which had recently been proposed as a cathode material for intermediate-temperature solid oxide fuel cells, were investigated as a function of oxygen partial pressure over the oxygen partial pressure range of 10−4 ≤ pO2 (atm) ≤ 0.21 at 1073 ≤ T(K) ≤ 1323. The increase in total conductivity with increasing temperature below the low-temperature, order–disorder transition indicated a semiconductor-type behaviour with an activation energy of 0.42eV. When the oxygen partial pressure was increased to air pressure at a fixed temperature, the total conductivity increases with an apparent slope (∂log σ/∂log pO2) of 1/10 to 1/22. The maximum oxygen ion conductivity, as extracted from the oxygen permeation measurements, was around 0.01S/cm under the nitrogen condition, which strongly supported the potential for cathode application. The chemical diffusion coefficient and surface exchange coefficient were also calculated from direct-current conductivity relaxation measurements and the former was best described by:

D(cm2/s) = 1.88 x 10-2exp[-0.77(eV)/kT]

Chemical Diffusivity and Ionic Conductivity of GdBaCo2O5+δ. M.B.Choi, S.Y.Jeon, J.S.Lee, H.J.Hwang, S.J.Song: Journal of Power Sources, 2010, 195[4], 1059-64