Oxygen ionic conductivity of La2NiO4+δ via interstitial oxygen defect Original Research Article

The ionic conduction properties of La2NiO4+δ were studied from oxygen permeation flux and defect-related transport properties. The effects of the applied oxygen chemical potential gradient and temperature on the oxygen permeability of La2NiO4+δ at various thickness are reported. The thermally activated oxygen permeation flux increased monotonically with increasing oxygen chemical potential gradient, yielding a maximum of 0.15 cc min−1 cm−2 under air/N2 conditions for the 0.95 mm-thick La2NiO4+δ specimen at 900 °C. The oxygen ion conductivity of La2NiO4+δ was calculated as a function of temperature and oxygen partial pressure by differentiating the chemical diffusion equation for the oxygen permeation flux based on the dominant electronic transference number. In addition, the oxygen ion conductivity was extracted successfully by solving the Nernst–Einstein equation combining with the calculated self-diffusion coefficient of oxygen from the chemical diffusivity and thermodynamic enhancement factor from the equilibrium oxygen nonstoichoimetry of a La2NiO4+δ specimen, and a deviation of the OPP dependence of 1/6 power was observed.