Strontium-doped LaCoO3 or LaMnO3 materials have been studied for use as cathodes for solid oxide fuel cells (SOFCs). This choice relies on the required properties and competitive cost. However, formation of reaction products under typical electrode-firing conditions may affect the performance of SOFCs. La2Zr2O7 was detected at YSZ/electrode interfaces. This reaction product was synthesized from powders and characterized to obtain a better understanding of its effects on cell performance. Its structural, thermal, and electrical properties are reported.