Determination of strontium and lanthanum zirconates in YPSZ-LSM mixtures for SOFC

Mixtures of 3% yttria- and partially-stabilized zirconia with LSM_x (strontium-doped lanthanum manganite, x = 0, 0.15 and 0.2) were prepared and heat treated at temperatures between 1000 and 1300 °C to recreate the cathode-electrolyte interface interactions taking place during preparation and operation of solid oxide fuel cells (SOFC). Such interactions include the formation of La₂Zr₂O₇ and SrZrO₃, which are undesirable for SOFC. The effect of the manganese oxidation number on the mechanosynthesis of LSM during zirconate formation is also discussed. A quantitative analysis of zirconate formation by X-ray diffraction and Rietveld refinement was undertaken. Formation of lanthanum and strontium zirconates was completely avoided at temperatures as high as 1300 °C by synthesizing lanthanum manganites from MnO₂ doped with 15 at.% of Sr. Finally, in the presence of LSM, monoclinic phase content was diminished to less than 1.5 mol% after heat treatment at 1300 °C.