Study of phase evolution and microstructural features when modeling operating conditions of fuel cells based on lanthanum-strontium ferrite compounds

Abstract

   Interest in lanthanum-strontium ferrite ceramics having mixed electron and oxygen-ion conductivity as well as good stability is due to the great potential for use as electrode materials for solid oxide fuel cells. The article presents the results of an assessment of alterations in the morphology and phase composition of ceramics based on lanthanum-strontium ferrite compounds obtained by solid-phase synthesis. This was done during simulation of conditions as close as possible to their operating conditions in the mode of elevated temperatures. The primary objective of the research is to alter theratio of the phase composition of ceramics under prolonged thermal exposure, simulating thermal ageing processes, and thus, oxidation processes that occur during long-term cyclic tests. The studies revealed that the presence of the Sr2Fe2O5 phase in the composition of ceramics results in enhanced resistance to corrosive oxidation processes during high-temperature corrosion. The data obtained on the change in the electrochemical characteristics of ceramics depending on the exposure time during the simulation of high-temperature degradation revealed that the most significant decreases were observed after 400-500 hours of consecutive tests at a temperature of 500-600 °C and after 250-300 hours at temperatures above 700 °C. Moreover, the reduction in the specific power is due to the formation of oxide inclusions in ceramics, resulting from the decomposition of the (La0.3Sr0.7)FeO4 phase in the composition of the ceramics. In turn, the presence of the Sr2Fe2O5 phase results in the formation of an oxidation-resistant structure, leading to less pronounced changes in specific power during measurement of parameters of electrochemical characteristics.