In this paper, we report the chemical reactivity between Ce0.7RE0.2Mo0.1O2 (RE = Y, Sm) (CRMO) and 8 mol% yttria-stabilized zirconia (8YSZ), at an elevated temperature in air and investigate the crystal structure, morphology, and electrical conductivity of their reaction product. Solid state reaction between CRMO and 8YSZ starts to occur on heating at 1000 degrees C and yields single phase Mo-doped fluorite solid solution at 1200 degrees C, as confirmed by powder X-ray diffraction (PXRD). Thermo-gravimetric analysis in 5% H-2/N-2 showed that weight loss in the case of solid solution is less compared to pure CRMO. In order to study the ability of CRMO to be co-fired with YSZ, compatibility tests between CRMO and 8YSZ in the pellet form were also performed. It was found that electrical conductivity data of CRMO-YSZ solid solution (CRZMO) in the air and wet H-2 was lower than CRMO, due to the formation of defect associates and decrease in concentration of charge carriers. (C) 2014 Elsevier B.V. All rights reserved.