6 Perillat-Merceroz, Cedric Gauthier, Gilles Roussel, Pascal Huve, Marielle Gelin, Patrick Vannier, Rose-NoelleThe possibility to introduce cerium in the perovskite-type titanate with formula La0.33Sr0.67TiO3+delta (LST) was investigated. Pure-phased La0.23Ce0.1Sr0.67TiO3+delta (LCST) was only obtained by synthesis at high temperature in reducing (diluted hydrogen) atmosphere. The material exhibits the same orthorhombic symmetry with Immm space group as LST and nearly the same cell volume. When exposed to oxidizing atmosphere at 1200 degrees C, Ti3+ and Ce3+ oxidation leads to the decomposition of LCST and the growth of several nanoscaled Ce-rich phases, as highlighted by backscattered electron microscopy. Shifting the gas back to a reducing atmosphere, but at lower temperature, only involves partial reversibility, ensuring the presence of nanoparticles of (electro)catalytically active phase within an electronically conducting n-type network. The catalytic tests in methane steam reforming at 900 degrees C (CH4/H2O = 10/1) show that the properties of the partially decomposed phase are greatly improved, what could make it a promising anode material for SOFC operating on slightly wet methane