Alanine Assisted Low-Temperature Synthesis and Characterization of Nanocrystalline SOFC Cathodes

Abstract

Nanocrystalline SOFC cathode materials of perovskite family, La1-xSrxM1-yCoyO3, where 0<x{less than or equal to}0.5, 0<y {less than or equal to}0.8 (M is transitional metal= Mn or Fe) have been synthesized at a relatively low temperature by combustion technique using alanine as novel fuel. The thermal analyses of the precursor gels show sharp single step combustion with low decomposition temperature (170- 200oC). Detailed X-ray powder diffraction analyses show 47-96% phase purity in the as-synthesized powder and upon calcination at temperature ~ 825oC, single phase material is obtained wherein the nanocrystallinity (crystallite size ~19-24 nm) is retained. Densification studies of the materials are carried out within 900-1100oC. The coefficient of thermal expansion (CTE) of the sintered cathodes is also measured. Detailed electrical characterizations of the sintered cathodes are evaluated and correlated with the microstructures. The electrochemical performances of SOFC single cells (Ni-YSZ anode-support /YSZ ~ 20 μm/LaFeO3-based cathodes) with ceria interlayer show high current density of ~1.2 A/cm2 at 0.7V at 8000C.