Study of (La,Sr)(Ti,Ni)O3-δ materials for symmetrical Solid Oxide Cell electrode - Part B: Conditions of Ni exsolution

The stability of La2xSr1-2xTi1-xNixO3-delta (LSTN) and La7x/4Sr1-7x/4Ti1-xNixO3-delta (25LSTN) materials in high tem- perature reducing conditions has been studied with a special focus on the Ni exsolution process for SOFC anode / SOEC cathode application. In a general way, LSTN and 25LSTN compounds are stable after treatments at 800 degrees C in air and wet reducing atmosphere. The low chemical expansion makes them compatible with a use in an electrochemical Solid Oxide Cell. Those materials are therefore useful for an application as symmetric oxide cell electrode or only hydrogen electrode. In situ Nickel exsolution is evidenced at 800 degrees C in Ar/H-2 (2%) but is limited by a slow kinetics and a higher temperature pre-reduction is preferred before a use as SOFC anode (SOEC cathode). Depending on the treatment, in situ reduction or pre-reduction (T > 1000 degrees C), the compounds are not in the same thermodynamic equilibrium state.