Caroline Levy

Thermodynamic Stabilities of La2Zr2O7 and SrZrO3 in SOFC and Their Relationship with LSM Synthesis Processes

A Sr-substituted LaMnO 3 perovskite (LSM) and yttria-stabilized zirconia mixture was investigated by thermodynamic calculations to understand the factors affecting the stabilities of La 2 Zr 2 O 7 and SrZrO 3 , the two zirconates, at different conditions in solid oxide fuel cell. Two sets of independent experimental investigations were done: (i) The thermodynamic stabilities of the two zirconates in N 2 and air to simulate the phase equilibria at different conditions. The experimental data proved that thermodynamic calculations were reliable and they can be used to provide guidance to reduce/prevent the formation of the two zirconates. (ii) The stabilities of zirconates with LSM made by fusion and conventional methods were compared in air and N 2 . The fused LSM powders from Saint-Gobain show less zirconate phase formation in all conditions than in conventional synthesis methods.

Fused LSM: A Novel Powder Limiting the Formation of La2Zr2O7 and SrZrO3 Resistive Phases at the Interface with YSZ in SOFC Cathodes

In solid oxide fuel cell (SOFC) on the cathode side, the formation of highly electrically resistive phases as La2Zr2O7 (LZO) or SrZrO3 (SZO) at the triple-phase boundary between LSM, YSZ and air decreases the performance of the cell and is partially responsible for the long term degradation of the SOFC. Saint-Gobain Company is making LSM material by fusion process. The reactivity of LSM made by fusion and conventional methods with 8YSZ was compared. Ageing tests were performed by increasing the temperature over 1100{degree sign}C and in several atmospheres (air and N2). Whatever the conditions are, the reactivity of fused LSM is barely if not observable whatever the Sr content is, whereas LSM powders made by conventional methods lead to the formation of LZO or SZO as a function of Sr content. Thus, LSM made by fusion process is a promising material for cathodes to avoid the long term degradation of SOFC.