IMPROVED CATHODE MATERIALS FOR THE SOLID OXIDE FUEL CELL

Single phase Sr- and/or Co-doped LaMnO 3 perovskite materials with various cation stoichiometries (A/B ratios) were produced by spray drying and characterised for structure and phase composition. Room temperature X-ray diffraction analysis on equimolar mixtures of La y-x Sr x Mn 1-u Co u O 3 (y=1, 0.95, 0.9; 0≤x≤0.4; 0≤u≤0.2) and Yttria-stabilised Zirconia (YSZ) after annealing at 1200 and 1400°C indicate a strong dependence of the chemical interaction on the composition of the perovskite and on temperature. La-deficiency leads to slower reaction rates. The materials with y=0.95, u=0, and 0.2≤x≤0.4 did not form La 2 Zr 2 O 7 or SrZrO 3 in reaction with YSZ at 1200°C (400 h), while La 0.65 Sr 0.3 MnO 3 resisted the formation of zirconates even at 1400°C (200 h). Although Co-doping enhances the reactivity, the perovskite La 0.79 Sr 0.16 Mn 0.9 Co 0.1 O 3 also did not form zirconates with YSZ at 1400°C (20 h). The electrical conductivity and thermal expansion of the same materials confirm the applicability of La 0.95-x Sr x Mn 1-u Co u O 3 perovskites with an A-cation deficiency for the cathode of SOFC compared to their stoichiometric counterparts.