Oxygen diffusion of non-stoichiometric (La, Sr)MnO3 /CERIA NANO-composite SOFC cathode

Conference Dates

March 10-14, 2019


Solid oxide fuel cell (SOFC) is one of the highly efficient energy generation system, and it requires higher power density per unit volume to expand SOFC stationary market as well as vehicle. Co-sintering of stacks or cells including electrodes, electrolyte and separators is most promising approach to improve the power density significantly. Generally, cathode materials have low heat resistant temperatures, and they were easily decomposed or degraded by sintering at a high temperature which is suitable for densification of SOFC electrolytes. Cathode material of (La1-xSrx)1-yMnO3 (LSM) shows relatively highly heat resistance and preferable low-reactivity with fluorite electrolytes during sintering at high temperatures. The addition of LSM also much increased degradation temperature. However, it shows lower cathodic properties than lanthanum strontium cobaltite and lanthanum strontium cobalt ferrite because of poor oxygen ionic conduction. We thus investigate LSM/ceria nanocomposite cathode materials to improve oxygen ionic conduction.

The nanocomposite precursor powder containing LSM and lanthanum doped ceria (LDC) was synthesized by glycine method. Two stoichiometric compositions, which are stoichiometric composition (y=0) and non-stoichiometric (y=0.05), were prepared as LSM, and LDCs that were dissolved with lanthanum at various ratios were used to investigate inter-diffusion of lanthanum between LSM and LDC. The composite ratio of LSM and CeO2 was fixed at 9: 1 (molar ratio). Figure 1 shows SEM image of LSM/LDC nanocomposite sintered at 1200oC for 5 h in air. Sintering at 1200oC for 5h resulted in dense composite, and fine LDC particles were homogeneously dispersed with LSM. Lanthanum ratios of LDC and LSM in the composite were identified using XRD peak shift of LDC and magnetic properties of LSM, respectively. Electrical conductivity and oxygen diffusion coefficient were estimated with these dense composites. Oxygen diffusion coefficient were obtained by electrical conductivity relaxation method.

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