Abstract
The oxygen stoichiometry, thermal expansion, morphology, and electrical conductivity of a co-doped perovskitetype cathode system, La1-x Sr (x) Mn0.85Fe0.05Co0.05Ni0.05O3+a (x = 0-0.4 mole), are studied for intermediate-temperature solid oxide fuel cell applications. Sr2+-doping led to a decrease in the unit cell volume, oxygen stoichiometry, particle size, and activation energy, and an increase in the coefficient of thermal expansion and electrical conductivity. The sample with x = 0.3 mole exhibited four to five fold weight loss with respect to La0.75Sr0.25MnO3+delta at an intermediate temperature range and suggested the availability of a large number of oxygen vacancies due to a co-doping effect. This sample also showed sufficiently high electrical conductivity (similar to 76 S cm(-1)) at 650 A degrees C, a low activation energy (similar to 0.15 eV), and a coefficient of thermal expansion (similar to 12.1 x 10(-6) A degrees C-1) comparable to those of the adjacent components and submicron sized particles. The experimental results are explained using defect models.similar to