Mixtures of 3% yttria- and partially-stabilized zirconia with LSMx (strontium-doped lanthanum manganite, x=0, 0.15 and 0.2) were prepared and heat treated at temperatures between 1000 and 1300 degrees 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 degrees C by synthesizing lanthanum marganites 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 degrees C. (C) 2008 Elsevier B.V. All rights reserved.