Evaluation of chemical stability, thermal expansion coefficient, and electrical properties of solid state and wet-chemical synthesized y and Mn-codoped CeO₂ for solid oxide fuel cells

Chemical stability and high electrical conductivity under the operating conditions of solid oxide fuel cell (SOFC) are considered as the momentum for innovating solid electrolytes and electrodes. In this paper, we report synthesis, structure, chemical stability and electrical conductivity of novel co-doped Ce_0.9-xY_0.1Mn_xO_2-δ (x = 0-15 mol%) (CYMO). X-ray diffraction of Mn and Y-doped CeO₂ shows the formation of fluorite-type structure with a space group Fm-3m. A few weak peaks corresponding to a tetragonal Mn₃O₄ phase has been detected in some samples. Solubility of Mn in ceria is explained by considering the influence of the ionic radius, the crystal structure and its electronic structure. Thermal analysis shows dissimilarity between the reduction behavior of Ce_0.9Mn_0.1O_2-δ and Ce _0.9-xY_0.1Mn_xO_2-δ. Ce _0.8Y_0.1Mn_0.1O_2-δ exhibited the highest conductivity of ∼6 × 10^-2 S cm^-1 and 0.15 S cm^-1 at 700 C in air and H₂, respectively. Surface studies have confirmed the formation of S species upon exposure to 30 ppm H ₂S in H₂ and a mechanism for S poisoning is presented.