Effect of Co substitution for Mn on Y1-xSrxMnO3 properties for SOFC cathode material

[[abstract]]c2002 Springer - Y0.6Sr0.4Mn1-yCoyO3 (0 [less-than or equal to] y [less-than or equal to] 0.4) perovskite oxides were prepared by the coprecipitation method. The effect of Co substitution for Mn on the crystal structure, electrical conductivity and thermal expansion properties were investigated. By X-ray powder diffraction, the crystal structure was found to change from hexagonal symmetry of Y0.8Sr0.2MnO3 to orthorhombic of Y0.6Sr0.4Mn1-yCoyO3. The differences in the structure of the unsubstituted Y1-xSrxMnO3 (0.2 [less-than or equal to] x [less-than or equal to] 0.4) are attributed to the average ionic radii of the cations and the amounts of Mn4+ present. The results of electrical conductivity analysis can be described by the small polaron hopping conductivity model. With Co substitution, the activation energy increases, possibly due to an increase of Jahn-Teller distortion, at an extent higher than the increase of the concentration of charge carriers; thus, the electrical conductivity decreases. In addition, the relative densities of the materials reached [similar to] 94% with sintering at 1350°C for 12 h and had higher concentration of the available lattice sites, thus showing higher conductivity, than that with sintering at 1300°C for 6 h, which achieved [similar to] 70% relative density. It is also found that the thermal expansion coefficient (TEC) increases as the Sr and Co content of Y1-xSrxMn1-yCoyO3 increases and those with Co content of y = 0.2 exhibit TEC compatibility with YSZ.[[department]]化學工程學