Thermodynamic properties of some perovskite type oxides used as SOFC cathode materials

The solid-oxide electrolyte galvanic cells method has been employed in orde r to obtain the thermodynamic properties of some perovskite-type materials based on lanthanum strontium manganite and lanthanum strontium ferrite mang anite. The relative partial molar free energies, enthalpies and entropies o f oxygen dissolution in the perovskite phase, as well as the partial pressu res of oxygen have been obtained in the temperature range of 1073-1273 K. B y solid state coulometric titration, the initial composition of the perovsk ite phase was altered under controlled conditions. The results evidence the influence of the oxygen relative stoichiometry change on the thermodynamic properties. The effect of the iron content and of the overall A-site stoic hiometry is also discussed. Broadening the potentialities of solid state EM F techniques, the method was proved very useful in thermodynamic studies wh en searching improved cathode materials used in solid oxide fuel cells (SOF C). (C) 1999 Elsevier Science B.V. All rights reserved.