The structural evolution of La-Cr-O thin films and the formation mechanisms of the LaCrO3 perovskite phase have been studied. X-ray amorphous La-Cr-O protective coatings were deposited by magnetron sputtering on metallic interconnect materials. During the annealing of the material in air a two-step phase transition from La-Cr-O to a monoclinic LaCrO4 monazite and further to an orthorhombic LaCrO3 Perovskite phase was observed. The formation of a fine nanoporous structure is a result of the significant increase in density of the final LaCrO3 perovskite in comparison with monazite LaCrO4 phase. While the porous structure was not sought after for this application, these distinctive nanostructures may have numerous applications in catalysis, separation membranes or for other SOFC components. (c) 2006 Published by Elsevier B.V.