Investigation of Pr0.2Ce0.8O2-δ@Li2CO3 nanocomposite electrolytes as intermediate temperature ionic conductors: a thermal, structural, and morphological insight

Pr0.2Ce0.8O2-δ@Li2CO3 (PDC-LC) nanocomposite electrolytes were prepared through the co-precipitation of Pr-doped cerium/lithium complex carbonate and its pre-firing and sintering operations. The structural and thermal properties of PDC-LC nanocomposite were investigated by means of X-ray diffraction, thermogravimetric analysis, Raman spectroscopy, and electrochemical impedance spectroscopy. The remarkable presence of oxygen vacancies and the influence of the interfacial interactions between PDC crystallites and amorphous Li2CO3 were deliberately probed by Raman spectroscopy and FEG-SEM, respectively. It was observed that there is a long-range interaction between the PDC crystallites and Li2CO3 phase, which resulted in the tight binding of \( {\mathrm{CO}}_3^{2-} \) ions on the facets of PDC nano-crystals and may be well characterized by the shift and broadening of the characteristic Raman spectroscopic peaks of \( {\mathrm{CO}}_3^{2-} \) ions in the samples. The X-ray diffraction results confirm the successful incorporation of praseodymium into ceria phase that presented the sole crystalline structure contrarily to the lithium carbonate present as an amorphous phase in the as-prepared samples. The oxygen ionic conductivity behaviors of PDC-LC phase were measured at the intermediate operating temperature range (300–500 °C). However, AC conductivity measurements demonstrated that the conductivities in air atmosphere increased linearly with temperature. The Arrhenius plot of total conductivity showed two different slopes indicating two distinct conduction mechanisms. The interfacial interactions between the PDC and LC phase inside the PDC-LC nanocomposite were responsible for oxygen ionic conductivity.