To accurately evaluate the role as diffusion barrier of gadolinia-doped ceria (GDC) interlayer, often used in real stacks of solid oxide fuel cells, the cation diffusion behavior in a LSCF/GDC/YSZ system was investigated. Diffusion under open circuit voltage (OCV) and cathodic polarization conditions was evaluated using pellet-type cells in which a dense GDC interlayer, about 1 pm in thickness, was prepared by pulse laser deposition (PLD). Results clearly show that under polarization, SrZrO3 formation along both LSCF/GDC and GDC/YSZ interfaces is accelerated. The enhancement of Sr diffusion during cathodic polarization is explained by a shift to higher values of the thermodynamic activity of Sr at the LSCF/GDC interface that also leads to a decrease in oxygen potential. (C) 2014 Elsevier B.V. All rights reserved.