Space charge layer induced superionic conduction and charge transport behaviour of “alkali carbonates and tri-doped ceria nanocomposites” for LT-SOFCs applications

Abstract

Our investigations highlight the importance of alkali carbonates addition on influencing the superionic conduction via composite interfaces in doped ceria based nanocomposites Ce0.76Pr0.08Sm0.08Gd0.08O2-δ/(Li0.52Na0.48)2CO3 (CPSG/LNC). X-ray diffraction of composite confirms single-phase cubic CeO2 like structure as major phase with few weak reflections due to (Li0.52Na0.48)2CO3 suggesting that the major part of the carbonates transform into amorphous phase during synthesis. The CPSG/LNC nanocomposites show improved ionic conductivity in the temperature range 200–650 °C with maximum ionic conductivity σ650°C = 6.02 × 10−2 S-cm−1 for composition having 35 wt% of (Li0.52Na0.48)2CO3. The TEM analysis reveals that the amorphous layer of carbonates forms on the nanocrystalline codoped ceria particles to develop a close shell-layer enclosure, stimulating space charge layer as a preferred conduction paths in the composite electrolytes. Dielectric and complex ac-conductivity measurements confirm the existence of low frequency interfacial/space-charge polarization along the grain boundary regions and multi-ion long-range conduction along the interface regions.