The growth of La2NiO4+delta at the interface between La2O3 and NiO has been studied from 950 to 1450 degrees C in argon, air and oxygen. The thickness, microstructure and composition of the formed La2NiO4+delta layers have been characterized by means of SEM, EDX, EBSD, EPMA and XRD. The growth rate follows parabolic kinetics. It has been concluded from the position of Pt markers that La2NiO4+delta grows predominantly by solid state diffusion of Ni2+, and the experimental results were accordingly fitted with Wagner's expressions for self-diffusion. Above 1100 degrees C the diffusion coefficients follow Arrhenius-type temperature dependencies, with activation energies 243 +/- 21 and 218 +/- 21 kJ/mol evaluated for the conditions at the La2O3/La2NiO4+delta and NiO/La2NiO4+delta interfaces, respectively. Below 1100 degrees C the diffusivity falls more steeply with decreasing temperature, and possible explanations are discussed. Compared to cation diffusion in perovskite-type oxides, Ni2+ diffusivity in La2NiO4+delta is in higher range. (C) 2012 The Electrochemical Society. [DOI: 10.1149/2.044206jes] All rights reserved.