Electrical conductivity and related properties of molten carbonates coexisting with ceria-based oxide powder for hybrid electrolyte

The electrical, thermal and structural properties of composite electrolyte containing Ce0.9Gd0.1O1.95 (GDC) powder and (Li0.52Na0.48)2CO3 eutectics are investigated by AC impedance, differential thermal analysis and polarized Raman scattering spectroscopy. The system shows a dependence of the electrical conductivity upon the temperature. The transition point varies with the apparent average thickness of the liquid phase, while the activation energy, ΔEa, remains constant at any distance from the solid phase. Higher electrical conductivity was obtained for the GDC/(Li0.52Na0.48)2CO3 composite than that for α-Al2O3/(Li0.52Na0.48)2CO3. Even in the N2 or Air gas flow, the weight loss caused by decomposition of CO32− ion based on Lux–Flood equilibrium was rarely observed. The symmetric stretching mode of the polarized Raman spectra shows that carbonate ion maintains its D3h symmetry in the presence of ceria. A constant value of the depolarization ratio of the ν1(A′1) mode with regard to the apparent average thickness confirms that the symmetry of carbonate ions in the molten state is not altered by the presence of ceria powder. It was more stable than that for the system containing α-Al2O3 as a reference sample. These findings contribute to the understanding of the properties of ceria-based carbonate electrolyte for intermediate temperature solid oxide fuel cells.