The chemical compatibility of 8 mol% YSZ and (La_0.8Sr _0.2)_1-xMnO₃ (LSM) has been investigated at temperatures in excess of 1300°C. Stoichiometric LSM (x=0) reacted readily with YSZ producing the undesired La₂Zr₂O₇ (LZO) pyrochlore phase at 1300°C. An A-site deficiency of x=0.03 reduced the amount of pyrochlore present, and increasing the LSM particle size from 0.3 μm to 2.5μm removed any visible LZO peaks in the XRD analysis. An A-site deficiency of x=0.05 was found to be adequate to prevent the formation of the La₂Zr₂O₇ (LZO) pyrochlore at temperatures up to 1400°C within the detection limits of X-ray diffraction. Increased A-site deficiency in the LSM resulted in improved adhesion between cathode and the electrolyte.