La2NiO4+delta, a mixed ionic-electronic conducting oxide with K2NiF4 type structure, has been studied as cathode material with La0.9Sr0.1Ga0.8Mg0.2O2.85 (LSGM) electrolyte for intermediate solid oxide fuel cells (IT-SOFCs). XRD results reveal excellent chemical compatibility between the La2NiO4+delta sample and LSGM electrolyte. A single cell (0.22 cm(2) active area) was fabricated with La2NiO4+delta as cathode, Ni-Sm0.2Ce0.8O1.9 (2:1; w/w) as anode and LSGM as electrolyte. A thin buffer layer of Sm0.2Ce0.8O1.9 (SDC) between anode and electrolyte was used to avoid possible interfacial reactions. The cell was tested under humidified H-2 and stationary air as fuel and oxidant, respectively. The electrochemical behaviour was evaluated by means of current-voltage curves and impedance spectroscopy. Microstructure and morphology of the cell components were analysed by SEM-EDX after testing. The maximum power densities were 160, 226, and 322 mW cm(-2) at 750, 800 and 850 degrees C, respectively with total polarisation resistances of 0.77, 0.48 and 0.31 Omega cm(2) at these temperatures. Cell performance remained stable when a current density of 448 mA cm(-2) was demanded for 144h at 800 degrees C, causing no apparent degradation in the cell. The performance of this material may be further improved by reducing the electrolyte thickness and optimisation of the electrode microstructure. (C) 2010 Elsevier B.V. All rights reserved.