Oxygen ionic conductivity of La2NiO4+delta via interstitial oxygen defect

Abstract

The ionic conduction properties of La2NiO4+delta 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+delta 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/N-2 conditions for the 0.95 mm-thick La2NiO4+delta specimen at 900 degrees C. The oxygen ion conductivity of La2NiO4+delta 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+delta specimen, and a deviation of the OPP dependence of 1/6 power was observed. (C) 2012 Elsevier Ltd. All rights reserved.