Thermodynamic Properties, Defect Analysis, and Electrical Conductivity of the La0.8Sr0.2ScxMn1-xO3-delta Infiltrated into YSZ Scaffolds

Abstract

La0.8Sr0.2ScxMn1-xO3-delta-yttria stabilized zirconia composite anodes were synthesized by infiltration and investigated as alternative anodes for intermediate solid oxide fuel cells. Non-stoichiometric variation of oxygen content and electrical conductivity in La0.8Sr0.2ScxMn1-xO3-delta-yttria stabilized zirconia composite was studied by high temperature coulometric titration at 923-1023 K. La0.8Sr0.2ScxMn1-xO3-delta shows an oxygen deficient composition depending on the oxygen partial pressure, temperature, and Sc content. A defect chemistry model is presented by taking into consideration the interaction of randomly distributed defects, Sr-La('), V-O(center dot center dot), O-O(X), Mn-Mn(X), Mn-Mn(center dot) and Sc-Mn(X). The proposed defect model fits well with experimental non-stoichiometric data. The interaction among the defects for vacancy formation is strongly influenced by the amount of dopant, Sc content, and temperature. The thermodynamic properties, oxidation enthalpy Delta H and entropy Delta S, were obtained from the oxygen isotherms. The electrical conductivities measured by the 4-probe method as a function of oxygen partial pressure and temperature were high enough for composite anode application.