SYNTHESIS AND CHARACTERIZATION OF LaMnO3- BASED CERAMIC MATERIALS FOR SOLID OXIDE FUEL CELLS

Abstract

Fuel cells are devices that convert the chemical energy of the fuel directly in to electrical energy and heat by electrochemical reactions. Interest in fuel cells started growing steadily with the question of how to provide electrical energy to support the growing energy economy in the world without the risk of pollution. Today’s fuel cells have provided answer to all the question and have an immiscible potential to supply partially supply world energy needs in the future in case of oil crises. Among the different types of fuel cells, solid oxide fuel cell (SOFC) with perovskite structure are mostly applied and studied. LaMnO3 is recently one of the most intensively studied cathode materials for SOFC. In the present study, LaMnO3-, La0.8Sr0.1Co0.1MnO3- and La0.8Sr0.1Fe0.1MnO3- cathode materials were synthesized by combustion method. The effect of substitution of Sr and Co/Fe cations for La cations onthermal, structure, electrical and electrochemical properties of the so lid electrolytes were investigate. TGA/DTA analysis confirms that the calcination temperature (1000 OC) used is the appropriate temperature for the preparation of all these materials using La (NO3)3.6H2O, MnSO4.H2O, Co(NO3)2.6H2O, Fe(NO3)3.9H2O and C6H8O7.H2O precursors. The XRD results of all materials reveal the formation of the hexagonal structure with R-3C space group Fd-3m. SEM characterization shows that the prepared samples have slightly porous structure with agglomerated particles. The EDS analysis also confirms the presence of La, Mn, Sr, Co, Fe and O elements in all synthesized materials. From the FTIR analysis, the most significant absorption bands located at 1629.8cm-1 and 589.9cm-1 wave numbers are identified. The room temperature conductivity of all samples is found to be 6.3 × 10-3 , 8.7 × 10-3 and 5.8 × 10-3 S.cm-1 for LaMnO3, La0.8Sr0.1Co0.1MnO3- and La0.8Sr0.1Fe0.1MnO3- of cathode materials, respectively. From the dielectric constant ε′ as a function of frequency study, it is observed that value of ε′ maximum at lower frequencies and it begins to drop and becomes constant at higher frequencies.